AOT MIPO2 book sample by AO Foundation

Table of contents

Principles

History and evolution of minimally invasive plate osteosynthesis

Basic mechanobiology of bone healing and new aspects of cerclage

2.1

Basic mechanobiology of bone healing

2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to

periprosthetic fractures 3

Instruments

Implants

Intraoperative imaging

Reduction techniques

Decision making and preoperative planning

101

Postoperative management

113

Complications and solutions

121

Education in minimally invasive plate osteosynthesis (MIPO)—how to become a

141

better MIPO surgeon

Cases 11

Clavicle

153

Humerus, proximal

179

Humerus, shaft

219

Pelvis

247

Acetabulum

287

Femur, proximal

331

Femur, shaft

375

Femur, distal

411

Tibia and fibula, proximal

461

Tibia and fibula, shaft

509

Tibia and fibula, distal

545

Calcaneus

595

Pediatric fractures

623

Fragility fractures

651

Special indications

679

Implant removal

757

VII

Authors Stephan M Perren, Alberto Fernandez dell’Oca, Pietro Regazzoni, Markus Windolf

2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures 1

Introduction

Surgical fracture treatment aims to restore the function of bone, limb, and patient. Cerclages, which were conceived as simple periosteal loops for internal fixation, seem to be an attractive and simple method of fracture fixation. When used on their own, cerclages lack sufficient strength to maintain enough stability to allow functional aftertreatment. Historically, therefore, cerclage was used routinely in combination with a protective plaster cast. This procedure combined the disadvantages of both surgical and conservative methods. Furthermore, the loose coupling between plaster cast and bone did not significantly protect cerclage from overload. With the development of stable and strong fixation using plates, nails, or fixators the cerclage technique fell into disrepute and was infrequently used. Its application was limited to the treatment of long oblique or spiral fractures. Recently, the use of cerclage has seen a revival due to the increasing incidence of periprosthetic fractures where the intramedullary cavity is not available for penetrating implants (Fig 2.2-1). Today, when cerclages are used, they are protected by internal splinting (plate, nail, or stem of the prosthesis), avoiding the need for the plaster treatment mentioned above. Frequently, periprosthetic fractures are also multifragmented explosion fractures. Fragments are displaced centrifugally. In such cases cerclage offers help because it provides simple, safe, and efficient centripetal reduction and, when using up-to-date technology, adequate fixation. In recent decades, our understanding of the way bone reacts to forces, strain, and blood supply has evolved. Furthermore, recent studies have demonstrated improvements in fixation technology [1]. The use of cerclage in the treatment of periprosthetic fractures will benefit from the application of these new insights into the reaction of bone to trauma [2]. These studies suggest it is now time to reconsider conventional cerclage technology and to discuss possible improvements with special reference to their use in minimally invasive

osteosynthesis (MIO) and the treatment of periprosthetic fractures. The term “cerclage” will be used here for any type of loop circling the bone while other uses of wires, such as tension bands or wire sutures, will not be considered. The term “stability” will be used in its orthopaedic sense describing the degree of relative mobility of the fracture fragments. Cerclage wiring is a simple technique and has been practiced widely since the advent of surgical treatment of fractures. A cerclage technique, using solid wires locked with a knurled twist, was described by Götze in 1933 [3]. Since then many studies have reported the use of various cerclage technologies using wires, cables, and straps which were connected to form closed loops in a variety of ways. The results and resultant conclusions in the literature differ widely. Leemann [4] addressed the lack of strength of the Götze [3] cerclage and proposed a new technology (“cerclage by folding”) that offered superior strength. This technique improved results

Fig 2.2-1 Treatment of a periprosthetic fracture. The proximal main fragment is connected to the distal main fragment by a locked plate acting as a splint. The stem of the prosthesis blocks the use of penetrating implants and/or reduces the anchorage of periosteal splints within a part of the proximal fragment. Plate screws when locked can either be used as unicortical screws or if they are of the variable angle locked (VAL) type they may be tilted, such that they avoid the medullary stem while maintaining locking. In the proximal fragment cerclage is used to approximate the bone fragments. The cerclage wires improve fixation and approximate fragments. As a supplementary implant their limited strength is acceptable for the application illustrated (courtesy of P Regazzoni).

2 Basic mechanobiology of bone healing and new aspects of cerclage 2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures

but this was generally not convincing for many surgeons (see 2.1 Cerclage as a reduction tool). As late as 1985 Rütt and Beck [5] proposed the use of a simple wire twisted knot cerclage as a useful technology especially suited to spiral fractures. All these techniques had limited indications and results which do not match those of today’s technology. In addition they could not, as a rule, forego protection by a plaster. The indications for cerclage were limited, the results were generally disappointing, and other technologies offered a better outcome. Therefore, today cerclage is used rarely as an exclusive implant even for its most popular indication:

Fig 2.2-2 Cerclage temporarily used for reduction of fracture fragments during surgery. Once the plate is in place and fixed, the wires are removed. This is a generally accepted use of cerclage functioning as a tool rather than as an implant. It is important to consider that special care is required when passing the wire around the distal tibia because of the proximity of the large blood vessels.

The increasing numbers of periprosthetic fractures, where technologies with penetrating implants are of limited use has led to a revival of interest in cerclage. The shortcomings of the cerclage are outweighed by its benefits and cerclage is now frequently used for this indication. (Clamp-on plates [8] are not discussed here as they are considered incompatible with minimally invasive technology.)

Functions of cerclage

The cerclage may function in different ways: cerclage may be used temporarily as an instrument during surgery (Fig 2.2-2) or can be used long-term as an implant (Fig 2.2-3). Cerclage can either reduce or fix fracture fragments. When used temporarily the wire loop is used as a tool for reduction. When used long term the cerclage functions as an implant.

the treatment of middiaphyseal spiral fractures of the tibia. Newer technologies, such as plates, nails, and fixators have been used in preference to cerclage for over 50 years despite the fact that their use is generally more demanding. Their results are far better than those of cerclage [6, 7].

2.1

Cerclage as a reduction tool

Cerclage allows the reduction of several fracture fragments with a single cerclage loop. Cerclages applied for reduction of complex fractures function best when the instrument allows intermittent tensioning. If a fracture cannot be properly reduced on the first attempt, releasing tension and shaking the wire and fragments during retensioning may be a solution.

Fig 2.2-3a–b Cerclages as sole implants stabilizing a diaphyseal fracture. Due to the limited strength and preload of the cerclage wires, such treatment is rarely successful. Such fixation usually needs protection by an external or internal splint. In this example, the appearance of callus indicates that absolute stability was either not achieved or not maintained (courtesy of JW Wilson).

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Stephan M Perren, Alberto Fernandez dell’Oca, Pietro Regazzoni, Markus Windolf

With reduction using temporary cerclage fixation, the fracture is ready for final stabilization, such as with a splinting plate. Once the fracture is splinted by the plate the cerclage wires are removed. The temporary use of cerclage as a reduction tool is generally accepted because it offers a good balance between the technical performance of reduction on the one hand and the biological disadvantages on the other hand. Cerclage is an efficient reduction tool when used for reduction of long, shallow fracture planes and/or for reduction of fragments around an intramedullary implant. When carefully applied using appropriate instruments to avoid stripping the periosteum, the balance between mechanical advantage and biological damage is favorable. Today’s MIO cerclage procedure takes advantage of the MIO wire passer (see Fig 2.2‑9). This is a special forceps with two connectable cannulated semicircles which can be inserted around the bone, allowing the insertion of a wire loop with minimal soft-tissue damage (see Fig 2.2-7). 2.2

2.4

Assisting wire stabilization

Cerclage can effectively assist in the treatment of periprosthetic fractures (Fig 2.2-4). With the stem of the prosthesis in place, fixation can rarely be achieved with conventional locked plates. The screw all too often hits the stem or does not achieve sufficient anchorage in the bone fragments. A special design of the plate including angled locked screws may offer a solution but hitherto these plates do not offer sufficient locking strength when applied in a nonperpendicular inclination. New improved designs of VAL screws provide strong locking at inclined positions. When treating a periprosthetic fracture the addition of cerclage not only improves the reduction of the fragments but also adds strength to the fixation. When cerclage is used in this way it is combined with two splinting elements, the plate and the stem of the prosthesis. This is, overall, a good indication for cerclage.

Cerclage as permanent fixation implant

When cerclages are used as the exclusive fixation element for long-term maintenance of reduction, the balance between advantages and disadvantages is questionable. The use of cerclage as a long-term implant is limited to specific indications. To clarify the nature of real or perceived disadvantages the following aspects deserve discussion. 2.3

Exclusive wire stabilization

The use of cerclage as an exclusive implant for fixation (Fig 2.2-3) is of questionable value because other technologies offer far more advantages with respect to regaining early and complete bone function. When treating long spiral fractures in the past, the surgeon tried to compensate for the insufficient strength of exclusive wire loops by adding a plaster cast. A plaster cast does not abolish displacements of the fragments, due to the inherently loose coupling between plaster and bone through skin and soft tissues. The plaster is meant to act as an external splint but it does not prevent high loads exerted on a comparably stiff cerclage fixation. The cerclage is not sufficiently protected from functional load by the additional plaster cast. On the contrary the additional weight of the plaster may even increase the load exerted on the cerclage.

Fig 2.2-4 Cerclage used to improve the anchorage of a locked plate. The cortex does not offer sufficient purchase to the screws. The presence of the stem prevents the use of penetrating implants, thus only unicortical screws were used. The cerclage improves the fixation strength (courtesy of A Fernandez).

Callus-free healing, mostly described in the cerclage literature as endosteal healing, may be direct healing. Absolute stability is provided very rarely by cerclage.

2 Basic mechanobiology of bone healing and new aspects of cerclage 2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures

Biological aspects of cerclage

Rhinelander and Stewart [9] observed in a dog model that cerclage wires and bands are mechanically compatible with fracture healing. They also studied the effect of cerclage contact upon periosteal blood supply. Wires and straps behaved differently. The effect of wires on blood supply was minimal; bands and straps produced a more noticeable effect. The local elevation of straps with undercuts or the like, did not, in the hands of Rhinelander improve the periosteal blood supply. According to Wilson [10], such undersurfaces of the straps rendered the reduction and fixation more difficult. Nyrop et al [11] confirmed the limited damage of cerclage upon periosteal blood supply while Geiser [12] reported major damage to the periosteum and impaired fracture healing.

tissue on the inserting side. The method referred to by Rütt and Beck [5] (see Fig 2.2-8) consists of an insertion tool and a hocked wire-catching tool. Once again this procedure is not compatible with MIO technique because of the extent of the exposure required. Tissue damage is likely to occur when trying to find the wire and pull the hook back.

The pilot experiments by Fernandez et al [13] confirmed that cable and wire applied to femora of sheep had minimal effect on bone periosteal blood supply as shown in Fig 2.2-5.

Examples from literature [9] and the authors’ own experience (Fig 2.2-5) prove that the interruption of longitudinal blood vessels has no major consequences because there is ample centripetal vascular supply to the periosteum.

3.1

3.2

“Strangulation” of blood vessels

It is obvious that a wire placed around the periosteum seemed/would block blood vessels, which run along the bone. This was be thought of as local contact strangulation. The question is, whether the interruption of longitudinal blood supply has an important effect on the vitality of periosteum and bone.

Biological damage at insertion of the cerclage loop

Inserting the cerclage around the bone without creating softtissue damage is challenging, especially when performing MIO. As Fig 2.2-6 visualizes schematically, the exposure required during application of the conventional (Beranger) instrument is not compatible with the goals of MIO. To bring the tip of the semicircle within range to grab the end of the wire involves a fairly wide displacement of the skin and soft

When passing the wire around the bone the surgeon must ensure that the tip of the wire passer is always in direct contact with the bone, especially when closing the forceps, otherwise larger blood vessels and nerves of the limb may be caught and strangled [14, 15] (see Fig 2.2-7, Fig 2.2-9). Careful use of proper tools should avoid this major complication.

Solid wire Cable

Hematoma Prep. artifact Cortical bone Hematoma Small loss of perfusion

Cortical bone 200 um

Small loss of perfusion

200 um

Fig 2.2-5a–b The vascular damage beneath the cerclage wire and cable. The cerclages were applied to the intact femur of a sheep. After 5 weeks the arterial supply to the hind leg was marked with procion red infusion. The periosteum near the wire and the cable in contact with the bone appears red indicating the presence of an arterial blood supply. Only a small length of the periosteum at the contact site does not show blood perfusion. This damaged area is for wire 0.4 mm, and for cable 0.2 mm wide. There is no relevant strangulation of periosteal blood supply but there is a tiny area of contact damage [13]. a The effect of a solid wire. b The effect of a cable.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Stephan M Perren, Alberto Fernandez dell’Oca, Pietro Regazzoni, Markus Windolf

Fig 2.2-6a–c The conventional method of passing the wire using the cannulated semicircular instrument. The method dislodges a major part of the soft tissues to bring the exit hole (dark pink) of the semicircle channel into a position where the wire can be caught. This applies both to wire passers with straight or angulated handles.

Fig 2.2-7a–c Application of the MIO wire passer. This improved version uses two semicircles which can be assembled to form a solid full-circle channel. This allows passing of the wire with minimal disruption (dark pink) of soft tissues. The arrows on the instrument indicate the application of the wire. The two semicircles can be disassembled for atraumatic removal.

2 Basic mechanobiology of bone healing and new aspects of cerclage 2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures

Fig 2.2-8a–c The method of passing the wire as used by Rütt and Beck [5]. Catching the wire end requires skill and dislodging of skin and tissues.

Fig 2.2-9a–c Minimally invasive osteosynthesis cerclage passer consists of two semicircles that can be applied sequentially and assembled with minimal soft-tissue stripping. Handling procedure: after both semicircles are sequentially applied snugly around the bone, the wire is passed through the channel in the instrument and remains in place while the two halves are removed sequentially.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Stephan M Perren, Alberto Fernandez dell’Oca, Pietro Regazzoni, Markus Windolf

3.3

Pressure necrosis

The amount of radial pressure has been calculated by Bandi and Sommer [16]: p=

F r * b

Where F is the amount of tension in the wire, r is the radius of the loop, and b the contact width of the wire or band. As an example they calculated that the pressure exerted onto bone by the cerclage was 150 kp/cm2 (~15MPa) assuming a tension force in the wire of 60 kp (~600N), a diameter of the loop of 2 cm and a contact width of 0.2 cm. The footprint of the wire and cable according to Fig 2.2-5 may be only 0.2–0.4 mm wide [13]. Static compression exerted by plates (up to 1400N) [17] as well as by 4.5 mm cortex screws (up to 1800N) [18] has not induced pressure necrosis. Today, based on these observations, it can be assumed that radial pressure and pressure necrosis are

not the cause of any bone resorption that may be seen in cerclage fixations as long as the stability of the fixation is maintained. 3.4

Formation of grooves beneath the cerclage

The formation of massive grooves beneath cerclage wires has been reported (Fig 2.2-10a) [19, 20]. This observation was frequent in the early days of cerclage and seems to be less frequent today due to improved technique and procedures. The resorption beneath the cerclage was attributed by Leemann in 1957 [21] to mechanical abrasion. Nowadays, we understand it as a reaction of bone which is triggered by micromotion which in turn induces active resorption (Fig 2.2‑10b) [22]. Jones [20] indicated that micromovement between cerclage and bone at high strain condition induces the bone loss [2]. The groove formation reported by Baumann [19] may be induced by chemical irritation (chrome catgut) together with instability.

Fig 2.2-10a–b Formation of bone grooves beneath Partridge bands. a X-ray shows a large groove. b Similar groove produced by dynamic strain of periosteal soft tissues near the bone surface [9, 22].

Technical aspects of cerclage

4.1

Types of stability

When discussing stability with respect to cerclage the usual classes of absolute and relative stability familiar to trauma surgeons do not adequately describe what is seen. A third definition of stability is needed, namely “twin (loose-lock) stability”. This type of stability is typical for cerclage but also for other technologies which allow “play” before engaging solidly, such as the locked nail. Relative stability plays a minor role with respect to cerclage. In the following, the term “wire” will be used for wires, cables, and straps.

4.1.1 Absolute stability

The highest degree of stability, absolute stability, is characterized by an absence of displacement within the fracture on functional loading. It depends on the presence of sufficient compressive preload on the fracture surfaces (see 2.1 Basic mechanobiology of bone healing). If the surgeon wishes to achieve absolute stability using cerclage, he/she must ensure that the tension in the wire maintains compression of the fracture plane during functional loading until the fracture is solidly united. Such tension may be created during surgery; its maintenance depends on:

2 Basic mechanobiology of bone healing and new aspects of cerclage 2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures

• Sufficient strength of the wire. The rare incidence of wire breakage indicates that wire strength is usually sufficient to withstand functional load. • Sufficient strength of the connection between the ends of the wire, eg, the knot. Failure of the loop usually occurs by loosening or breakage of the wire connection. • Maintained close reduction of the bone fragments, ie, no slippage of the fracture surfaces. Small adjustments of fragment position may result in gross instability because the tension in the wire is lost. • Maintained mechanical integrity of the enclosed bone fragments, ie, no fracture of the small ends of the bone fragments. This problem occurs when the wire is placed too close to the tips of the fragments. 4.1.2 Relative stability

Reversible displacement as seen when fragments are splinted with an elastic element requires that the splint is strong enough to avoid plastic deformation and stiff enough to provide the stability required for undisturbed fracture healing. A bridging plate or nail or an external fixator are stiff enough to fulfill this function. Cerclage alone does not provide splinting when it is loose (loose phase of twin stability, see 4.1.3 Twin (“loose-lock“) stability). During the lock phase the displacement allowed by the elongation of the wire is minimal. Therefore, cerclage can only provide relative stability when the cerclage is used to fix a stiff splint (plate, nail, or shaft of the endoprosthesis). The applied functional load will then result in reversible displacement. The displaced fracture will return to its original position when the load is released. The degree of fracture mobility will depend on the load applied as well as on the stiffness of the bridging element.

In phase 1 minimal load will displace the fracture fragments. After a certain amount of travel the fragments will abut against the wire loop and in phase 2 further travel may be reversibly minimized. This situation represents a combination of free displacements of the fragments which then changes abruptly into an elastically (or plastically) resisted displacement. This frequently occurs after application of a cerclage and this is similar to the situation of a conventionally locked intramedullary nail where there are also two distinct phases of stability. According to the authors (see Fig 2.2-10b), the repeated displacement allowed in phase 1 induces bone surface resorption at the contacting interface between bone surface and wire. The effect will be an ongoing increase of instability which may result in delayed- or nonunion. 4.2

Cerclage configuration

In cases where wire stabilization is used on its own, a frequent mechanism of cerclage failure is breakage of the bone fragments. The problem is that in an effort to improve the strength of fixation by increasing the lever arm between the wires, the surgeon may be tempted to apply the wires near the end of the fragments where they taper and become weak. Leemann [23] suggests positioning the cerclages with respect to the bone fragments such that the outermost wires are placed 1 cm in from the tips of the fragments. The resulting positions of the cerclages are outlined in Fig 2.2-11. This rule applies to solid cortical bone. This proposition of Leemann [4, 23] may be a good compromise and is generally accepted in the literature. However, when the fragment is porotic or does not consist of cortical bone it is advisable to increase the distance between the tip of the fragment and the outermost cerclages.

4.1.3 Twin (“loose-lock“) stability

When tension of the wire is either not installed or lost, a type of stability is present which is characterized by two phases with an abrupt changeover between them. • Phase 1: At rest there is no tension of the wire. Due to slackness the wire does not produce any stability and the fragments displace easily. • Phase 2: After a certain amount of free travel the wire regains tension and stabilizes the fragments though mostly in an unacceptably displaced position.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Stephan M Perren, Alberto Fernandez dell’Oca, Pietro Regazzoni, Markus Windolf

1 cm

3 cm

1 cm

Fig 2.2-11 Long oblique fracture, good leverage of the cerdages. To protect the tip of the fragments a minimum safe distance of 1 cm from the tip to the next cerclage must be allowed. The lever arm between the outer cerclages is 6 cm.

1 cm

2 cm

1 cm

2 cm

1 cm

Fig 2.2-12 Fracture with butterfly fragment, poor leverage of the cerclages. As in Fig 2.2-11 the cerclages are placed at least 1 cm from the tip of the fragments. The resulting lever arm between the main fragments and the butterfly fragment here is only 2 cm.

4.3

Cerclage types

The cerclage loop (wire, strap Fig 2.2-13, or cable Fig 2.2-14), may consist either of a simple piece of wire or one end may form a loop or a plug retainer. Straps are mostly locked using ratchets or the like. The material of the cerclage may be metal or plastic. The metal used for cerclage is usually steel (ISO 5832-1 annealed condition). Titanium is also used. Standard diameters of the solid wires are 1.25 mm (1.0 mm and 1.5 mm also used). Cables consist of multiple fine metal strands that render it flexible. Plastic materials without fiber reinforcement lack strength and, therefore, need a larger cross section compared to wires or cables. Thus plastic materials are designed as bands. They have, by necessity, a wider footprint on the bone and therefore produce larger contact damage to the blood supply. Some designs of metal cerclages also use flat bands. With these implants stability and strength are improved but this is a trade-off against loss of vitality of the soft tissues and bone. When a deformation is applied to a plastic cerclage the resisting force decreases with time (creep or stress relaxation). This phenomenon brings about an undesirable and sometimes deleterious loss of the initially applied tension.

For straps mostly made of plastic, the fixation elements are designed as ratchets. In general, such ratchets allow for a certain spring back when the applied tension is released. The amount of spring back is determined by the distance from step to step in the ratchet mechanism. Therefore, the design of the ratchet is important. Plastic material with ratchets allows installation of initial tension without the need for additional tools. When ratchets are used the distance from one “tooth” to the next is critical because it determines how much tension is immediately lost in the worst case due to travel from one tooth to the next. To reduce the vascular damage created by cerclage bands, these bands are often provided with a means of keeping the contact area to the bone small, aiming to create less damage to the blood supply. Plastic straps have been used with small transverse undercuts to produce a surface that is similar to a cogwheel. Another way to reduce the contact area is to use protrusions. For the same reasons similar designs have been proposed for wires, such as elevating the wire from the bone surface using spheres. As the vascular damage created by a wire is small and the reduction of the contact surface area results in comparably high local surface stress, we do not consider these designs to be an advance.

2 Basic mechanobiology of bone healing and new aspects of cerclage 2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures

Fig 2.2-13a–c Partridge and Parham bands. a Straps made of plastic material. b Straps combined with plastic splint. c Straps used as cerclage together with a small plastic splint. The elderly patient with porotic bone and poor compliance to partial weight bearing suffered an incident with consequent overload of a strap, which failed. The fracture only barely united [24].

The tension applied to the cerclage can be maintained using a device where the ends of the cable run in opposite directions through snugly fitting holes in the crimp. This technique is especially applicable when using cables (Fig 2.2-14a). Upon reaching the desired tension, the crimp is squeezed to maintain tension. The advantage of such a procedure is the high retention force achievable. An additional benefit is that the change in wire tension, which during crimping is minimal. 4.4

Locking cerclage loops

The most common way of locking wires consists of twisting or bending the free ends. For wires a multitude of tensioning devices are available from simple, flat-nose forceps to devices which allow twisting, tensioning, and cutting in one continuous movement. The usual method of locking by twisting requires a material that allows for extensive plastic deformation. Annealed steel is characterized by the

large amount of plastic deformation that occurs before breakage (~40%). This is at the expense of somewhat less strength (~780MPa). The relative lack of strength only has an effect with regard to the knot strength. Ruptures of the wire outside the twist or bend rarely occur. The locking mechanism of cables consists of crimping. Such a connection may be very strong and requires less plastic deformation of the cable material. Crimping is attractive because the amount of wire traction can be installed at selected levels and bending the wire flat is not required. Straps are held together using a ratchet mechanism with possible unloading at application due to displacement between the incremental steps. In the following section the different types of connection and their characteristics will be discussed for wires and cables only.

Fig 2.2-14a–b Cables appear to be the most up-to-date cerclages. They are strong and flexible. a The locking mechanism using crimps rests flat on the bone surface. b Conventional cable crimp.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Stephan M Perren, Alberto Fernandez dell’Oca, Pietro Regazzoni, Markus Windolf

The performance of cerclages under different conditions has recently been studied [1]. Two testing methods were applied using a material testing machine (Fig 2.2-15). With the first method the compressive effect of the applied cerclage was measured. For this purpose two halves of a diaphyseal bone were kept at a slight distance. The force required to maintain this position was evaluated in terms of traction in the wire. A second test concerned the effect of cyclically loading the two halves by application of a force tending to open the

compressed contact area. Packets of stepwise increasing cyclic load were applied. After each load cycle the initial position of the test specimen was restored and the remaining wire traction was recorded. Fig 2.2-16 shows the behavior of a 1 mm cable with respect to wires with different diameters. Fig 2.2‑17 shows the loss of wire/cable pretension during cyclic loading. Twisting wires produces and maintains the tension of the wire provided that the following aspects are considered.

Fig 2.2-15a–b Test setup and diagram of the testing methods of Wähnert et al [1]. The wire traction reached after surgery and its remaining effect after cyclic loading were measured.

After twisting / tightening After bending / crimping

Wire traction [N]

Pretension in wire [N]

300

150

250

125

200

100

150

100

Cable 1 mm Wire 1 mm Wire 1.25 mm Wire 1.5 mm

0 Cable 1 mm

Wire 1 mm

Wire 1.25 mm

Wire 1.5 mm

Fig 2.2-16 Cerclage type and diameter: traction in the cerclage comparing a 1 mm cable to wires with different diameters. Blue bars indicate wire traction after twisting the knot/tightening the cable. Gray bars show drop in traction when cutting and bending the twist/ crimping the cable.

150 250 350 Applied wire traction [N]

450

550

650

750

Fig 2.2-17 Cyclic behavior of cerclage loops. Average curves showing a drop of wire pretension with increasing functional load in terms of traction in the wire. The wire traction was cyclically increased and the remaining pretension was recorded after each cycle. The advantage of the 1 mm cable compared to the wires is obvious.

2 Basic mechanobiology of bone healing and new aspects of cerclage 2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures

4.4.1 Deformation of the twist and its effect on wire traction

If the surgeon twists the wires up to peak torque but not more, the twisted ends will spring back and tension drops off when the torque is released. This phenomenon occurs only at the turn of the twist closest to the bone (Fig 2.2-18a). Partial or even complete loss of tension is the result of such inadequate application. When twisting beyond peak torque, plastic deformation of the inner turn is installed resulting in higher maintained tension (Fig 2.2-18b). In the earlier literature this important aspect of application was not mentioned. This subtle difference of application explains, in the authors’ opinion, the wide variety of results reported. The results obtained with these settings are listed in Fig 2.2-19. The differences between elastic and plastic deformation of the innermost turn are impressive. Wire breakage occurred at the second innermost turn and had little effect on traction achieved (Fig 2.2-18c).

Wire traction [N]

After twisting After bending

200

150

4.4.2 Twisting under elevation

If the wires are twisted without special care, one wire may inadvertently twist around the other, which remains straight (Fig 2.2-20) instead of symmetrical deformation of both wire ends occurring. The asymmetrical twist does not allow full and maintained tension to be achieved. To avoid this, the wire must be twisted under tension while elevating the twist from the bone surface, ie, “twisting under traction”. 4.4.3 Cutting and bending the twist flat

The twist stands perpendicularly off the bone surface after twisting and cutting irritates the soft tissues and produces pain. It must therefore be bent to lie flat on the bone surface. According to Wähnert et al [1] (Fig 2.2-21) this can be achieved in three different ways. The maintained wire tension differs grossly depending on how the twisted wire is bent flat. The usual bend carried out perpendicular to the long axis of the wire results in about 50% loss of tension. If the twist is bent flat along the wire in a movement which continues the movement of twisting, here called “forward”, a similar loss of tension occurs. The “backward” group in which the bending movement reverses the movement of twisting results in a loss of nearly all the tension in the wire. To overcome the limited strength of simple twisted knots a proposal has been made [4] to use a double wire and to fold the two wire ends around a loop formed by the folded wire. The device developed by Müller [25] uses the same mechanism but with only one wire.

Fig 2.2-18a–c Different degrees of twisting the locking knot. a The innermost turn is twisted within the elastic range (shiny surface of wire). b The wire is plastically deformed in its entire length (matt surface). c Exceeding twisting resulted in wire breakage at the innermost turn.

100

0 Elastic

Plastic

Breakage

Fig 2.2-19 Deformation of the twist: wire traction produced with the setup of Fig 2.2-15. Blue bars: wire tension after release of twisting torque. Gray bars: wire tension left after cutting and bending flat, no manipulation of breakage group. Tests performed with a 1.5 mm cerclage wire.

Fig 2.2-20a–b a Both wires are symmetrically deformed. b One wire turns around the other which remains straight at the innermost turn. The strength of the knot does not reach optimal value. This can be avoided by pulling the knot away from the bone while twisting.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Stephan M Perren, Alberto Fernandez dell’Oca, Pietro Regazzoni, Markus Windolf

4.4.4 Complications

Leemann [21] reported that simple twisting of a solid cerclage wire of 1 mm diameter withstood 50 kg force (~500N) while folding the cerclage wire resisted 103 kg force (~1000N). He also noted that the tension in the wire with twisted knot dropped immediately to 50% while the folding technique maintained the initial tension. Furthermore, he showed that under dynamic load the knotted connection was inferior to the folded one. Wilson [10] reported the knot strength and yield points of different bands and wires and different applications. The wire diameter was reported to be more important in its effect upon traction achieved and maintained than the different ways of application. Wähnert et al [1] stated that the mode of applying the twist was equally important. This discrepancy of statements originates from the fact that the results of the different modes of application were not known earlier. Kanakis and Cordey [26] compared the stability achieved using a splinting plate combined with folded cerclage and/or plate screws. The cerclage performed astonishingly well (Fig 2.2-22). The combination of splinting plate with cerclage deserves further consideration.

Wire traction [N]

After twisting After bending

200

150

100

0 Perpendicular

Forward

Backward

Fig 2.2-21 Cutting and bending the twist flat: bending the twist flat in different directions. The loss of wire traction is ~50% when bending perpendicular to the wire loop or forward in a twisting direction. A backward bend results in drastic loss of traction. Tests were performed with a 1.5 mm cerclage wire.

Comparing the results of twisted knot and folded twin cerclage, a reduction of hospital stay from 84 to 52 days and of temporary working incapacity from 168 to 146 days has been reported [12]. Bandi and Sommer [16] observed a reduction to 18 days hospital stay and a working incapacity of 130 days after folded cerclage. Both series show that temporary working incapacity was between one-third and one-half a year following both cerclage and conservative treatment. If this data is compared with today’s data the difference shows that important advances in fracture treatment have occurred through the use of rigid internal fixation techniques.

Fig 2.2-22 Folded cerclage assisting a splinting plate. Comparing the twin folded cerclage strength under torque and axial load the cerclage performed very well [26].

The data from the literature reports a substantial incidence of complications but the results do not differentiate between single and multiple complications in the same patient. Still the picture is fairly uniform for delayed unions. Geiser [26] reported an incidence of delayed union of 27% with a total rate of 43% complications in 328 cases. The most recent data by Rütt and Beck [5] shows an obvious improvement when compared to earlier data but still reports an appreciable rate of complications. There was a complication rate of 24%, with about 5% delayed union, 6% malalignment, and 8% reduced joint mobility in 189 cases studied.

2 Basic mechanobiology of bone healing and new aspects of cerclage 2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures

The poor results from treating long diaphyseal fractures using cerclage were often understood to be caused by strangulation of bone and soft tissues. The results of Rhinelander and Stewart [9] and Fernandez et al [13] question such an explanation. The damage of cerclage contact and pressure is small due to the presence of sufficient centripetal periosteal circulation. Another explanation of the failures, namely pressure necrosis, due to high pressure exerted by cerclage onto the bone surface, is also in doubt. According to the data of Bandi and Sommer [16] the pressure exerted by the wire is small but their assumption of the footprint of the wire is challenged by the data shown in Fig 2.2-5. No pressure necrosis has been observed when large static compression is exerted by plates and by screws [17, 18]. The observation of grooves immediately deep to the cerclage by Baumann [19] is explained by the effect of interface instability in a similar way as Stadler et al [22] has shown with a plunger dynamically approaching but not hitting the bone surface. Ganz et al [27] induced interface resorption with plate screws which were dynamically tilted producing intermittent gapping. How can we understand the complications of the early days of cerclage treatment? Fig 2.2-18 shows that when the innermost turn of the cerclage wire is twisted only elastically, the wire traction which remains after releasing twisting torque is small. Under early mobilization with its functional loading, such low-wire traction will not maintain stable interfaces. The interface instability will induce secondary gross instability due to the bone resorption. Those comparably rare cases, where cerclage fixation on its own was successful, are explained by the achievement of good stability combined with careful aftertreatment. Two fracture surfaces with grossly rough surface structure without imperfect reduction may settle into a more snug relative position when the interfragmental compression is not sufficient to prevent the surfaces from settling. As the cerclage is stiff, applied traction elongates the cerclage only minimally. Even minimal “settling” of the fracture planes abolishes the cerclage traction completely and instability occurs. This is a situation comparable to that seen when interfragmental lag screw fixation is used as the sole method of fixation. Cerclages and lag screws both need protection by a splinting plate.

When considering the load-bearing capacity the weak spot of the cerclage wire is the locking device. The wire ends may “untwist” or unbend. Due to the stiffness of the wire or cable even minimal untwisting results in complete loss of wire traction and instability. Thus the strength offered by cerclage wiring on its own is weaker than the fixation strength offered by plates, nails, and fixators. As mentioned, cerclage wiring should, as a rule, not be protected by external plaster but by internal splinting using plates or intramedullary rods, including the shaft of the prosthesis. This is very similar to the way lag screws are protected by “neutralization” plates. Protecting a cerclage by external plaster has two major drawbacks. Firstly, the immobilization of joints and soft tissues may result in trophic disturbances like reflex dystrophy. Secondly, even a tightly applied plaster cast still allows some deformation of the fracture area. This is due to the comparably loose coupling between plaster cast and bone because of the presence of skin and soft tissue between plaster and bone. When a cerclage wire is loaded within the limits of its strength, the deformation of the wire is small. Therefore even small deformation of the cerclaged fracture induces high traction in the cerclage and thus the plaster does not protect from overload failure. Effective protection of a cerclage can only be provided by internal splinting using, eg, a bridging plate. The same applies to cerclage by cable but here the remaining strength of cable and crimp is larger compared to the twisted wire (see Fig 2.2-16). It is an open-ended question whether the use of cerclage and plate offer help in the treatment of complex fractures in the porotic bone of elderly patients. The limited resistance of bone to centripetal force beneath the wire, as well as the high demands regarding strength of fixation in patients who cannot control the amount of weight bearing postoperatively, render such application problematic. Still the combination of a plate anchored by screws with additional cerclages provides an added security worth considering.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Stephan M Perren, Alberto Fernandez dell’Oca, Pietro Regazzoni, Markus Windolf

Common errors

Understanding the following basic facts about technical, biological, and biomechanical aspects prevents common errors. 5.1

Technical aspects

Earlier technology often failed to reliably create and maintain the required wire tension needed to provide sufficient strength to allow functional aftertreatment. Cerclage as proposed by Götze [3] became unpopular due to a high rate of complications. The use of improved materials—cables rather than wires—is required. Protecting the cerclage with internal splinting using the stem of the prosthesis and/or by an additional splinting plate results in adequate strength and stability which allows withstanding load resulting from functional aftertreatment. 5.2

Biological aspects

Maintaining an intact blood supply to soft tissues and bone allows healing and improves resistance to infection. Major damage to the periosteal blood supply of bone is produced by forcing a conventional half-circle wire passer around a bone. This procedure results in major trauma to the skin, muscles, and periosteal soft tissues especially when the bone (eg, femur) is buried deep in soft tissues. Soft-tissue trauma can be avoided or minimized by using a wire passer inserted minimally invasively. The “generally accepted” view that cerclage strangulates longitudinal blood supply of periosteum and bone is challenged based on reports from the literature and the authors’ ongoing experiments. The most severe errors result from poor application of the wire passer.

When the tip of the wire passer is not guided in close contact around the bone a large blood vessel of the limb may be caught and strangulated with deleterious effect. 5.3

Biomechanical aspects

The early assumption that pressure exerted onto the bone surface by implants would induce pressure necrosis and secondary loosening is challenged if the interface is maintained stable. Static compression as used in compression plate osteosynthesis is biologically well tolerated without reaction. The fact that living cortical bone tolerates, within its limit of strength, static compression without pressure necrosis also applies to cerclage [18]. Similarly micromotion due to lack of stability at contacting surfaces produces bone surface resorption [27] whereby initial microdisplacements induces biologically gross “loose-lock” instability. Instead of applying small amounts of wire tension in an erroneous attempt to avoid “pressure necrosis”, resulting in instability, the wire tension must be high enough to avoid the secondary instability induced by bone resorption at the interfaces. The recent findings regarding the effect of plastic deformation of the twisted knot and strength of cable cerclage have direct clinical application. Considering today’s mechanobiological knowledge there is no conceivable reason why a cerclage should fail to result in adequate healing, provided the cerclage maintains stable fixation during functional aftertreatment.

Summary

Cerclages were conceived of as simple periosteal loops for internal fixation. When used on their own, cerclages have insufficient strength to maintain the stability that would allow functional aftertreatment. Cerclages, therefore, were initially used with external protection by plaster cast. This procedure combines the disadvantages of surgical and conservative treatment. With the onset of stable and strong fixation using plates, nails, or fixators the cerclage technique fell into disrepute and its infrequent application was limited to long oblique or spiral fractures. With increasing incidence of periprosthetic fractures the use of cerclage is worth reconsidering. The treatment of periprosthetic fractures without cerclage is demanding because it is not possible to use implants which

penetrate the medullary cavity because it is blocked by the stem of the prosthesis. Therefore, the periprosthetic fracture often cannot be treated by conventional compression or splinting technology. A specially designed plate and its locked screw connection (variable angle) may serve to assist the surgeon. The periprosthetic fracture is frequently also a multifragmented explosion fracture. Fragments are displaced centrifugally. Cerclage in this case offers help because it provides simple, safe, and efficient centripetal reduction and adequate fixation when using up-to-date technology. Cerclage offers this possibility, provided that improved technology permits achieving reliable fixation without unacceptable biological disadvantages. Properly performed cerclage may be an outstanding minimally invasive procedure worth considering.

2 Basic mechanobiology of bone healing and new aspects of cerclage 2.2 New aspects of cerclage: improved technology applicable to MIO with special reference to periprosthetic fractures

References

1. Wähnert D, Lenz M, Schlegel U, et al (2011) Cerclage handling for improved fracture treatment. A biomechanical study on the twisting procedure. Acta Chir Orthop Traumatol Cech; 78(3): 208–214. 2. Perren SM (2002) Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology. J Bone Joint Surg Br; 84(8):1093–1110. 3. Götze O (1933) Subcutane Drahnaht bei Tibiaschrägbrüchen. Arch Klin Chir; 177:145. 4. Leemann R (1952) Cerclage by folding and folding tighter. The problem of fracture surgery; special consideration of mechanical and biological viewpoints of fracture healing and of stabile osteosynthesis of long bones. Helv Chir Acta; 19(2):119–163. 5. Rütt J, Beck E (1985) [What is the value of Goetze’s wire cerclage in treating torsion fractures of the lower leg?] Unfallchirurg; 88(7):308–314. German. 6. Haas N, Hauke C, Schütz M, et al (2001) Treatment of diaphyseal fractures of the forearm using the Point Contact Fixator (PC-Fix): results of 387 fractures of a prospective multicentric study (PC-Fix II). Injury; 32 Suppl 2:B51–B62. 7. Müller M, Allgöwer M, Willenegger, H (1963) Technik der operativen Frakturenbehandlung. Berlin Göttingen Heidelberg: Springer Verlag. 8. Mennen U (2003) Mennen plate fixation for the treatment of periprosthetic femoral fractures. J Bone Joint Surg Am; 85(11): 2248–2249.

9. Rhinelander FW, Stewart CL (1983) Experimental fixation of femoral osteotomies by cerclage with nylon straps. Clin Orthop Relat Res; 179:298–307. 10. Wilson JW (1988) Knot strength of cerclage bands and wires. Acta Orthop Scand; 59(5):545–547. 11. Nyrop KA, DeBowes RM, Ferguson HR, et al (1990) Vascular response of the equine radius to cerclage devices. Vet Surg; 19(4):249–253. 12. G eiser M (1958) [Critical observations on the problem of cerclage of torsion and oblique fractures of the long bone, especially the tibia, with a contribution to the problem of fracture healing.] Schweiz Med Wochenschr; 88(6):137–144. German. 13. Fernandez A, Milz S, Perren, S M (2010) unpublished data from the ARI. 14. A leto T, Ritter MA, Berend ME (2008) Case report: superficial femoral artery injury resulting from cerclage wiring during revision THA. Clin Orthop Relat Res; 466(3):749–753. 15. Mehta V, Finn HA (2005) Femoral artery and vein injury after cerclage wiring of the femur: a case report. J Arthroplasty; 20(6):811–814. 16. B andi W, Sommer G (1959) [Experience with the folded cerclage technic of Leemann.] Helv Chir Acta; 26(2):95–113. German. 17. Perren SM, Huggler A, Russenberger M, et al (1969) The reaction of cortical bone to compression. Acta Orthop Scand Suppl; 125:19–29. 18. C ordey J, Blümlein H, Ziegler W, et al (1976) [Study of the behavior in the course of time of the holding power of cortical screws in vivo.] Acta Orthop Belg; 42 Suppl 1:75–87. French.

19. Baumann E (1956) [The material to be used for cerclage of bones.] Schweiz Med Wochenschr; 86 Suppl 20:533–534. German. 20. J ones DG (1986) Bone erosion beneath partridge bands. J Bone Joint Surg Br; 68(3):476–477. 21. Leemann RA (1957) [Notch cerclage as a technical improvement in winding of wires in fractures of long hollow bones.] Chirurg; 28(2):60–64. German. 22. Stadler J, Brennwald J, Frigg R, et al (1982) Induction of bone surface resorption by motion. An in vivo study using passive and active implants. Second International Symposium on Internal Fixation of Fractures. Lyon, France, 62–64. 23. Leemann R (1954) [Indications for the technic of cerclage in leg fractures.] Helv Chir Acta; 21(5–6):480–492. German. 24. Kallel S, Bouillet R (1991) [The use of Partridge plates in the treatment of femoral diaphysis fractures near a prosthesis in elderly patients.] Acta Orthop Belg; 57(1):11–18. French. 25. Müller ME, Allgöwer M, Schneider R, et al (1977) Manual der Osteosynthese. Berlin Heidelberg New York: Springer Verlag. 26. Kanakis TE, Cordey J (1991) Is there a mechanical difference between lag screws and double cerclage? Injury; 22(3):185–189. 27. Ganz R, Perren SM, Rüter A (1975) [Mechanical induction of bone resorption.] Fortschr Kiefer Gesichtschir; 19:45–48. German.

Acknowledgment

The authors thank Mark Lenz, ARI Davos, for his help editing the manuscript.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Chang-Wug Oh

23.2 Tibia and fibula, shaft: simple fracture, oblique 1

Case description

An 8-year-old boy sustained a both-bones fracture of his right leg. Initial treatment by percutaneous pinning with long-leg cast was performed. After 3 weeks the reduction was lost because of inadequate immobilization due to the windows made in the cast for wound management. The original fracture pattern was simple and oblique. One month after initial treatment the patient presented at the author’s hospital with angular deformity of his left lower leg.

Fig 23.2-1a–c a riginal injury x-ray. O b X -ray after percutaneous pins and long-leg casting show reduction of the fracture in slight valgus position. c L ong-leg cast with open windows for wound management.

Indication for MIPO

Once osteotomy of the malunited site is performed, the technique for fixation is the same as for treatment in acute tibial fractures in children. Titanium elastic nailing is recommended, but it commonly requires external support, such as cast, which in this case is not suitable as the wound still needs to be managed. In addition, the stability of titanium elastic nails may not be sufficient for nonunion treatment. Furthermore the fracture is more distal and it may be unstable after fixing with elastic nailing. Since the physis is open, rigid nailing may not be applicable. Therefore, MIPO is an ideal option for this patient from the points of view of stability and wound care.

Fig 23.2-2a–b One month after the initial fracture, AP and lateral x-rays show lost reduction of the simple, oblique diaphyseal fracture of the tibia. Note callus formation at the tibia and fibula fracture sites.

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23 Pediatric fractures 23.2 Tibia and fibula, shaft: simple fracture, oblique

Preoperative planning

Once a decision has been made for MIPO, a good preoperative plan helps to facilitate the subsequent execution of the surgical procedure. The plan should include the surgical approach, a graphic representation of the fracture fragments, the reduction technique, the most appropriate implant, and the sequential steps required in its application (Fig 23.2-3).

3 1 6

Fig 23.2-3a–b In general it is recommended to first fix the plate with cortex screws to hold the plate in the desired position, starting with the proximal part (1). The plate is used as a reduction tool by inserting a cortex screw, which will reduce and correct the valgus deformity (2). At this stage the alignment can be checked by image intensifier with the cable technique by aligning the center of the hip to the center of the knee and the center of the ankle, or by comparing alignment with the uninjured leg. Once alignment is correct, the additional LHSs are inserted (3, 4, 5, 6).

5 2 4

Operating room setup

Anesthesia

General anesthesia is usually recommended for children. Patient and image intensifier positioning

The patient is positioned supine on a radiolucent operating table. Placing a pad under the patient’s ipsilateral buttock prevents the leg from externally rotating so the surgeon does not need to hold the leg during the procedure. A pneumatic tourniquet is applied to the thigh and the leg placed on a pad (Fig 23.2-4). An image intensifier is positioned on the opposite side of the table. Equipment

• Simple external fixator • Locking compression plate (LCP) 3.5

Fig 23.2-4 The patient is positioned supine on a radiolucent table, with a tourniquet on the thigh and a bolster under the knee.

(Size of system, instruments, and implants may vary according to anatomy.)

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Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Chang-Wug Oh

Surgical approach

The osteotomy of the malunited site can be performed by a minimally invasive method. Through the lateral incision the fibula is osteotomized with multiple drilling. After the fibular osteotomy has been completed, a 1 cm incision is made on the anterolateral aspect of the tibia over the fracture site. Through the window of the incision a percutaneous tibial osteotomy is performed (Fig 23.2-5).

Fig 23.2-5a–b Percutaneous tibial osteotomy.

Reduction

Following the percutaneous tibial osteotomy, indirect reduction is performed using an external fixator (Fig 23.2-6). Schanz screws are placed into the proximal and distal tibial fragments in an AP direction close to the osteotomy site. Each

Schanz screw is fixed with a clamp and connected to a long bar after reduction by traction and manipulation to ensure correct length and alignment. Further correction is achieved by a mallet (Fig 23.2-7).

Fig 23.2-6a–c Preliminary reduction is maintained with a simple external fixator.

Fig 23.2-7 Further correction with a mallet is checked with image intensification.

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23 Pediatric fractures 23.2 Tibia and fibula, shaft: simple fracture, oblique

Fixation

Two small incisions about 3 cm long are made over the medial aspect of the proximal and distal tibia. A subcutaneous, extraperiosteal tunnel is created. A prebent, 10-hole LCP 3.5 is introduced into this tunnel.

Fig 23.2-8 Prebent, 10-hole LCP 3.5.

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Fig 23.2-9 Insertion of the plate. Note the protected saphenous vein.

Fig 23.2-10a–b Alignment of the tibia and contour of the plate are checked using image intensification.

Fig 23.2-11 A 3.5 mm cortex screw is used to reduce the fracture and stabilize the plate to the bone using image intensification.

Fig 23.2-12 Valgus alignment is corrected by a mallet.

Fig 23.2-13 Maintaining reduction, a 3.5 mm LHS is fixed into the proximal fragment.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Chang-Wug Oh

Fig 23.2-14a–b Postoperative x-rays show proximal and distal fixation using two 3.5 mm LHSs and one 3.5 mm cortex screw in each fragment. Alignment is acceptable and no physis is violated.

Fig 23.2-15 Sutured skin incisions.

Rehabilitation

Fig 23.2-16a–d Ten months postoperatively. a–b A P and lateral x-rays show complete fracture consolidation. c T he patient achieved good range of motion. d T he full-length standing x-ray shows good alignment and correct mechanical axis.

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23 Pediatric fractures 23.2 Tibia and fibula, shaft: simple fracture, oblique

Implant removal

Implant removal in children is recommended 1–1.5 years postoperatively to prevent bone ingrowth and to be able to remove the plate minimally invasively.

Fig 23.2-18a–b X-rays taken immediately after implant removal.

Fig 23.2-17a–d Implant removal 12 months postoperatively. a–b T he screws are removed percutaneously using the previous skin incisions. c–d T he plate is also removed distally through the previous skin incision.

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Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Author Chang-Wug Oh

23.3 Tibia and fibula, shaft: simple fracture, oblique

Case description

A 12-year-old boy was hit by a car and sustained a closed oblique simple fracture of the right tibial shaft. The leg was severely swollen and the patient complained of severe posterior lower-leg pain when his ankle was dorsiflexed passively. An emergency fasciotomy was performed to release compartment pressure.

Fig 23.3-1a–b Preoperative AP and lateral x-rays show a simple, oblique diaphyseal fracture of the tibia.

Indication for MIPO

Conservative treatment after reduction using plaster cast is the treatment of choice for pediatric tibial shaft fractures. However in this case, the patient required fasciotomy to treat compartment syndrome. It is difficult to maintain fracture reduction after fasciotomy and to treat the soft tissue using only a cast. For adults, nailing should be considered for treatment of simple transverse tibial shaft fractures. But in this case, nailing will damage the patient’s open physes. In addition the narrow tibial intramedullary canal hinders the rigid nailing. Therefore MIPO is the most appropriate option as it provides sufficient stability.

Fig 23.3-2a–b The lower leg of the patient was severely swollen. Compartment pressure was over 40 mmHg.

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23 Pediatric fractures 23.3 Tibia and fibula, shaft: simple fracture, oblique

Preoperative planning

Once a decision has been made for MIPO, a good preoperative plan helps facilitate the subsequent execution of the surgical procedure. The plan should include the surgical approach, a graphic representation of the fracture fragments, the reduction technique, the most appropriate implant, and the sequential steps required in its application (Fig 23.3-3).

4 5

The fasciotomy must first be treated by opening the anterolateral and posteromedial compartments. In this case plate fixation is applied on the medial side, so it will not compromise the anterolateral wound of the fasciotomy.

7 8 1 6 3

Fig 23.3-3 In general it is recommended to first fix the plate with cortex screws to hold the plate in the right position. Cortex screw (1) is inserted in the fourth hole from distal to hold the plate. Manual traction is performed to reduce the fracture and an LHS inserted in the fifth hole from proximal. Length and alignment are checked using image intensification, and if correct, LHSs are inserted in the last distal and last proximal holes, respectively (5, 6). Lastly unicortical screws (7, 8) are inserted.

Operating room setup

Anesthesia

General anesthesia is usually recommended for children. Patient and image intensifierpositioning

The patient is positioned supine on a radiolucent operating table. Placing a pad under the patient’s ipsilateral buttock prevents the leg from externally rotating so the surgeon does not need to hold the leg during the procedure (Fig 23.3‑4). A pneumatic tourniquet is not recommended in this case to allow easy assessment of the vascularity of the muscle. An image intensifier is positioned on the opposite side of the table. Equipment

• K-wires • 14-hole narrow locking compression plate (LCP) • Kelly forceps

Fig 23.3-4 The patient is positioned supine on a radiolucent table, with a bolster under the knee.

(Size of system, instruments, and implants may vary according to anatomy.)

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Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Author Chang-Wug Oh

Surgical approach

First, an emergency fasciotomy is performed (Fig 23.3-5). Then, medial plating is planned because it is a diaphyseal fracture with no soft-tissue lesion on the medial side

(Fig 23.3‑6a). Kelly forceps are used to tunnel under the subcutaneous tissue to create the epiperiosteal tunnel, then the plate is introduced (Fig 23.3-6b).

Fig 23.3-5a–b The anterolateral and posteromedial compartments are opened using subcutaneous fasciotomy with relatively small skin incisions.

Fig 23.3-6a–b a A 14-hole narrow LCP is placed on the skin to make two small incisions about 3 cm each made over the anteromedial aspect of the proximal and distal tibia. b Kelly forceps are used to create the epiperiosteal tunnel, before plate insertion.

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23 Pediatric fractures 23.3 Tibia and fibula, shaft: simple fracture, oblique

Reduction

Reduction is performed by manual traction because the fracture is relatively stable.

Fig 23.3-7a–d K-wires are inserted for temporary fixation of the plate over the bone using drill sleeves. Before fixation, the location of the plate should be verified using image intensification.

Fig 23.3-8a–d The fracture is reduced by manual traction and manipulation to ensure correct length and alignment. The contouring of the plate and its correct position is verified using the image intensifier.

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A 4.5 mm cortex screw is used as indirect reduction technique, placed under image intensifier guidance.

Fixation

Fig 23.3-9a–b Immediately postoperative x-rays show proximal fixation using three 5.0 mm LHSs and distal fixation using four 5.0 mm LHSs with two bicortical and two monocortical screws, and one cortex screw. Alignment is acceptable and no physis is violated.

Fig 23.3-10 Sutured skin incision.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Author Chang-Wug Oh

Rehabilitation

Fig 23.3-11a–d Control 6 months postoperatively. a–b X-rays 6 months postoperatively show complete fracture consolidation. c T he patient achieved good range of motion of knee and ankle. d L ong, standing x-ray shows correct mechanical axis.

Implant removal

In children plate removal is usually recommended and medial plating of the tibia will cause irritation to the skin and soft tissue.

b Fig 23.3-12a–b The screws are removed percutaneously using the previous skin incisions. The plate is also removed through the previous proximal skin incision.

Fig 23.3-13a–b Immediately postoperative x-rays after implant removal.

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23 Pediatric fractures

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Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Chang-Wug Oh

23.4 Femur, shaft: simple fracture, transverse

Case description

A 13-year-old boy sustained a closed, transverse fracture of the right femoral shaft after being hit by a car. He was overweight for his age.

Indication for MIPO

Pediatric femoral shaft fractures can be treated with different methods depending on the age and weight of the patient. The TEN is an ideal option for pediatric femoral shaft fractures in young children, but it was not suitable in this case, since the patient was over 10 years old and overweight for his age. Rigid intramedullary nailing may be considered, but it can destroy the blood supply to the femoral head resulting in avascular necrosis. The length and intramedullary canal of the femur is small for the standard size of the nail, In this case, plating is the recommended alternative. When plating is used, MIPO should be considered as this technique preserves blood supply to the fracture fragments.

Fig 23.4-1a–b Preoperative AP and lateral x-rays show a transverse diaphyseal fracture of the femur.

645

23 Pediatric fractures 23.4 Femur, shaft: simple fracture, transverse

Preoperative planning

A good preoperative plan helps to facilitate the subsequent execution of the surgical procedure. The plan should include the surgical approach, a graphic representation of the fracture fragments, the reduction technique, the most appropriate implant, and the sequential steps required in its application (Fig 23.4-2).

3 1 5

Fig 23.4-2 Preoperative plan. A 14-hole broad locking compression plate (LCP) is selected and three screws are placed on each main fracture fragment. 1 The second proximal hole is fixed first with a cortex screw to hold the plate in place. 2 Then, indirect reduction with a cortex screw at the second last hole distally is also fixed. 3–6 After checking the alignment with image intensification, additional LHSs are inserted in both main fracture fragments.

4 2 6

Operating room setup

Anesthesia

Equipment

General anesthesia is usually recommended for children.

• • • •

Patient and image intensifier positioning

The patient is positioned supine on a radiolucent operating table. Placing a pad under the patient’s ipsilateral buttock prevents the leg from externally rotating so the surgeon does not need to hold the leg during the procedure (Fig 23.4‑3). Preparing and draping both lower extremities in patients with complex fractures will allow for better assessment of leg length, alignment, and rotation by comparison with the uninjured leg. Improved lateral proximal view with image intensification is accomplished by elevating the opposite leg. The C-arm is positioned on the opposite side of the injured leg. A preoperative image of the contralateral hip and knee using image intensification can be helpful to check correct mechanical axis of the femur.

Large fragment manipulator Tunneling device (periosteal surfer) K-wires Broad LCP (or narrow, depending on the size of the femur)

(Size of system, instruments, and implants may vary according to anatomy.)

Fig 23.4-3 The patient is positioned supine on a radiolucent table, with a bolster under the knee.

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Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Chang-Wug Oh

Reduction and surgical approach

It is mandatory to restore axial alignment, length, and rotation. Although MIPO enables excellent biological advantage and optimal stability, it has technical difficulties and there is a risk of improper fixation and alignment because the fracture site is not opened. It requires a longer operative time which increases the risks for radiation exposure for patients and operating room personnel. Preliminary reduction by manual traction will usually provide an easy, reproducible MIPO procedure. If manual traction is not sufficient, reduction can be performed with a reduction tool, such as large fragment manipulator, fracture table and/or external fixator, and/or reduction via the implant. The use of an external fixator can facilitate the reduction procedure and maintain temporary alignment during the plating procedure

(Fig 23.4-4). In this case, the large fragment manipulator was chosen instead of an external fixator, featuring a self-drilling tip, standard tip, and round-cannulated tip, as well as a K-wire and cannulated drill. The threaded, cannulated rod with a round tip allows for a guided, unicortical/bicortical application. Proximal and distal fixator screws should be inserted carefully to avoid interference with the later plating procedure. For this purpose, correct screw positions would be anterolateral or anterior of the femur. Proximal and distal incisions are made on the lateral aspect of the thigh. A submuscular tunnel is created for plate insertion using the tunneler. The plate is inserted under this tunnel, and the fracture site is not exposed (Fig 23.4-5).

Fig 23.4-4a–d a Proximal and distal screws are fixed into the anterior aspect of the femur. A bar is used to connect the two clamps, then reduction is achieved by manipulating the segments. b–d AP and lateral images are checked with image intensification for proper alignment.

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23 Pediatric fractures 23.4 Femur, shaft: simple fracture, transverse

Fig 23.4-5a–d Creation of submuscular tunnel and plate insertion.

Fig 23.4-6a–c K-wires are inserted for temporary fixation of the plate over the bone.

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Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez

Authors Chang-Wug Oh

Fixation

5.0 mm LHSs are inserted. After fixation, alignment is verified with image intensification using the cable method (Fig 23.4-7). If rotation is correct, the electrocautery cord will pass over the center of the hip, the midline of the patella,

and slightly medial to the tibial eminence and the center of the ankle joint. This produced good alignment of the fracture (Fig 23.4-8).

Fig 23.4-7a–c Image intensification to check correct alignment of the femur using the cable method. a Landmark: center of the femoral head. b Landmark: center of the knee. c Landmark: center of the ankle joint.

Fig 23.4-9 Sutured skin incisions.

Fig 23.4-8a–b Immediately postoperative AP and lateral x-rays show good alignment of the fracture.

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23 Pediatric fractures 23.4 Femur, shaft: simple fracture, transverse

Rehabilitation

No casting or bracing was necessary during the postoperative period. The patient started range-of-motion exercises for the knee and hip in the hospital with crutches and toetouch weight bearing for approximately 8 weeks. The patient was allowed limited weight bearing until x-rays showed evidence of healing. One year postoperatively there was complete fracture consolidation and good range of motion (Fig 23.4-10).

Fig 23.4-10a–d X-rays and range of motion 1 year postoperatively. a–b X-rays show complete fracture consolidation.

d c Excellent range of motion 1 year postoperatively. d Standing x-ray shows good alignment and no overgrowth of the femur.

Implant removal

One year postoperatively the screws were removed through the original incisions with the assistance of image intensification. The proximal and distal incisions were used to expose the plate with enlargement of 1–2 cm. After removal of the screws, the undersurface of the plate was mobilized from the soft-tissue adhesion using the periosteal elevator. The plate was then removed using the hook-shaped retractor.

a Fig 23.4-11 Implant removal performed 1 year postoperatively.

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Fig 23.4-12a–b AP and lateral x-rays after implant removal.

Minimally Invasive Plate Osteosynthesis—second, expanded edition Reto Babst, Suthorn Bavonratanavech, Rodrigo Pesantez