Veterinary Surgery 38:770–779, 2009
Achilles Tendon Repair in Dogs Using the Semitendinosus Muscle: Surgical Technique and Short-Term Outcome in Five Dogs WENDY I. BALTZER,
DVM, PhD, Diplomate ACVS
and PAUL RIST,
DVM, Diplomate ACVR
Objective—To describe augmentation of primary Achilles tendon repair using suture with a semitendinosus muscle flap and report outcome in 5 dogs. Study Design—Prospective clinical study. Animals—Dogs (n ¼ 5) with Achilles tendon rupture (n ¼ 6). Methods—After tendon repair with #2 polypropylene in a 3-loop pulley suture pattern, the lateral one-half of the semitendinosus muscle was transected from the ischium, rotated distally then sutured with #2 polypropylene to the calcaneus in a 3-loop pulley pattern. The epitenon was sutured to the muscle flap fascia with interrupted sutures. All dogs had a bivalved cast for 2 weeks then a cranial splint for 2–6 weeks. Lameness scores (0 ¼ stands and walks normally to 4 ¼ non-weight-bearing lameness, plantigrade stance on affected pelvic limb) were determined every 2–3 weeks postoperatively for 12 weeks. Outcome was determined from telephone questionnaire of owners. Results—Four had lameness scores of 0, the 5th had a score of 1 at 12 weeks. Three owners were very satisfied with outcome. Minor complications included cast sores (2 dogs), infection (2), and acute swelling (1); 1 major complication occurred (infection resulting in reoperation). Conclusions—Semitendinosus flap augmentation resulted in early return to function without prolonged postoperative immobilization. Three dogs returned to full work/activity after repair. Clinical Relevance—Augmentation of primary Achilles tendon repair with a semitendinosus flap can be considered in dogs with chronic rupture but further investigation of the long-term outcome using this technique is needed. r Copyright 2009 by The American College of Veterinary Surgeons
resulting in complete transection of all of its components2 resulting in a typical tarsus plantigrade stance in dogs with complete rupture.3 Partial tendon ruptures, in which the superficial digital flexor remains intact, are thought to occur during exercise in large breeds or working/racing dogs.4,5 When the gastrocnemius tendon has ruptured but the superficial digital flexor remains intact, the dog most commonly presents with hyperflexion of the tarsus and hyperflexion of the digits from contraction of the superficial digital flexor.6 Besides blunt or sharp trauma, Achilles tendon injuries have been attributed in dogs and people to avulsion fracture of the calcaneus, chronic wear damage caused by repetitive stress, postmenopausal osteoporosis, exercise-
INTRODUCTION
T
HE ACHILLES tendon is comprised of 3 tendinous structures: the gastrocnemius tendon, the superficial digital flexor tendon, and the common tendon of the biceps femoris, gracilis, and semitendinosus muscles.1 The tendon of the superficial digital flexor proximally lies cranial to the gastrocnemius then passes medially to the caudal aspect of the gastrocnemius tendon as it courses distally. The superficial digital flexor tendon continues distally after inserting on the tuber calcis to insert on the proximal caudal border of the second phalanges of digits II–V.1 The most common cause of Achilles tendon rupture is reportedly acute trauma, such as laceration of the tendon
From the Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, Corvallis, OR. Address reprint requests to Wendy I. Baltzer, DVM, PhD, Diplomate ACVS, Department of Clinical Sciences, College of Veterinary Medicine, Oregon State University, 105 Magruder Hall, 2979 NW Audene Dr, Corvallis, OR 97331. E-mail: wendy.baltzer@ oregonstate.edu. Submitted May 2008; Accepted November 2008 r Copyright 2009 by The American College of Veterinary Surgeons 0161-3499/09 doi:10.1111/j.1532-950X.2009.00565.x
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induced hyperthermia, increased corticosteroids, and exposure to fluoroquinolones.4,5,7–10 Fluoroquinolones alter protein concentrations in the tendons of puppies, similar to a magnesium deficient diet, and enrofloxacin in cell culture induces apoptosis and DNA fragmentation of tendon cells and chondrocytes.11,12 Regardless of the inciting mechanism or completeness of the rupture, Achilles tendon injuries involving rupture of the gastrocnemius tendon are typically treated surgically by primary tenorrhaphy and postoperative immobilization. Surgical treatment is preferred over conservative medical management when there is complete gastrocnemius tendon rupture because recurrence is common with conservative treatment.3,8,9 In people and dogs, primary repair of the tendon most commonly involves the 3-loop pulley or the locking-loop suture pattern to oppose tendon ends or tendon to calcaneus insertion. A modified 3-loop suture pattern has been adapted for use with tendon avulsions from the calcaneus where the suture is passed through a bone tunnel in the calcaneus.13 Apposition of tendon ends or tendon to bone early in the postoperative period is imperative because a gap of o3 mm allows strength and stiffness to increase with a decrease in repair failure during the first 6 weeks after surgery.14 Maintaining apposition after suturing in the first 6 weeks can be problematic because weight bearing and muscle contraction may cause the suture to break or tear out of the tendon or bone before adequate return of strength to the tendon has occurred. Postoperative immobilization is recommended to prevent failure of the primary repair and to improve outcome by reducing the incidence of suture pullout or breakage. For the first 2–3 weeks after primary repair of the tendon, the repair is entirely dependent upon the suture used to oppose the tendon ends. Postoperative immobilization is recommended during this time to prevent suture failure or pull out of the tendon and repair failure.15 Immobilization methods used include transarticular external skeletal fixation, calcaneo-tibial bone screws, full casts, and splints.4,7,8,16–18 Unfortunately, no method of immobilization has proven more effective than any other in terms of complication rate, duration of immobilization, recovery time, or functional outcome.19 Prolongation of immobilization does not improve functional outcome and on average, immobilization is recommended for at least 6–10 weeks with a time to best recovery of function at 16 or more weeks.5,19 With this prolonged recovery, major complications, including recurrence of rupture are common.5,19 Specific major complications encountered include fracture at the calcaneo-tibial screw or fixator pins, breakage of the external skeletal fixator, osteomyelitis, and repair failure. Minor complications with postoperative immobilization methods often include cast sores, superficial infection, and continued tarsal hyperflexion.5,19
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To strengthen the repair and shorten the postoperative immobilization time, many authors recommend augmentation of the repair. One method is application of a bone plate to the tendon repair, however, a 2nd procedure must be performed to remove the plate at 8–10 weeks.20 Other synthetic implants used in dogs and people have included carbon fiber and polypropylene mesh, however, these implants may incite foreign body reactions.9,10,21 Autogenous flaps have been advocated to strengthen repaired tendons including free fascia lata grafts, fascial flaps of the plantaris and gastrocnemius, peroneus brevis or longus tendon transposition, and flexor hallicus longus muscle transfer.8,10,18,22 Allogeneic grafts of porcine small intestinal submucosa and acellular human dermal tissue matrix have been used to augment primary calcaneal tendon repair. Both autogenous and allogenous free grafts are degraded rapidly and require host tissue ingrowth to restore tendon strength and structure regardless of the substance used.23,24 To date, no investigations have proven one method of augmentation is more effective than any other.9 The prognosis for return to function is considered good to excellent for pet dogs3,19,20; however, return to work or vigorous athletic activities is considered fair to poor, with 71% of dogs returning to herding with good to excellent function in 1 report.5 Although many techniques are used successfully, no single technique has been proven to significantly reduce complications or shorten the time to best function. Rupture of the Achilles tendon most commonly occurs 2–6 cm proximal to the calcaneus, where the blood supply to the tendon is dependent upon vasculature arising from the calcaneal bone.4,9,18 Reestablishment of the blood supply across the defect in the tendon is important for tendon healing and to improve the strength of the healed tendon, as well as to prevent recurrence and return of the patient to preinjury function and activities. Muscle flaps deliver a blood supply to devitalized wounds to improve healing time and reduce morbidity.25–27 A myocutaneous muscle flap involving the semitendinosus muscle based on the distal vascular pedicle has been used to augment repair of an open comminuted tibial fracture in a dog.28 The semitendinosus muscle is suited to muscle transfer procedures because of its type III vascular supply where either proximal or distal vascular pedicles can be ligated and the remaining vasculature (caudal gluteal artery proximally and distal caudal femoral artery, distally) provides adequate perfusion through choke vessels to the entire length of muscle.29–31 We are unaware of previous reports using semitendinosus muscle to repair Achilles tendon rupture in the dog. We transferred the semitendinosus muscle to the Achilles tendon in 5 dogs (6 tendon ruptures) to provide an immediate blood supply and cellular matrix to the repaired tendon, with an aim to reduce healing time and improve repair strength.
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Thus our purpose was to determine if transposition of the semitendinosus muscle to augment primary repair of the Achilles tendon in dogs with rupture of the tendon would improve outcome and return to function as well as require reduced postoperative immobilization time. Our null hypothesis was that augmentation of primary Achilles tendon repair with a distal vascular-based semitendinosus pedicle would have no effect on functional outcome or postoperative immobilization time.16,18,19
MATERIALS AND METHODS Surgical Technique With dogs positioned in lateral recumbency, the affected pelvic limb was elevated away from the table and aseptically prepared and draped. The skin was incised from 2 to 3 cm proximal to the ischium, distally to the calcaneus on the caudolateral aspect of the hind limb. The subcutaneous tissue was dissected to the depth of the semitendinosus muscle and common calcaneal tendon from the ischium to the tendinous insertion on the calcaneus. The superficial digital flexor tendon was exposed and a lateral desmotomy performed to retract the tendon medially. The epitenon was incised laterally, from the calcaneus to 2–3 cm proximal to the ruptured and retracted tendon bundles. In 3 instances, the tendon was debrided of fibrous tissue and the cut ends apposed with suture in a 3-loop pulley pattern using #2 polypropylene. The other 3 tendons were repaired without debridement using a 3-loop pulley pattern and #2 polypropylene. When there was avulsion from the calcaneus (3 tendons; dogs 1, 3), the tendon was apposed to the bone with a single modified 3-loop pulley suture using #2 polypropylene to a calcaneus tunnel created with a 2.5 mm drill bit. The bone tunnel was oriented in a caudolateral to proximomedial direction through the calcaneus to avoid interference with the superficial digital flexor tendon. The caudal gluteal artery and vein were ligated where they entered the semitendinosus muscle at the ischial tuberosity. A combination of blunt and sharp dissection was used to free the lateral one-half of the muscle from its origin on the tuber ischium. The muscle was divided into medial and lateral sections with a combination of blunt and sharp dissection, distally until the caudal femoral artery was identified. The freed, lateral half of the semitendinosus muscle was rotated 1801 distally, and sutured with #2 polypropylene in a 3-loop pulley pattern to the distal tendon in midsubstance tendon ruptures, or to the calcaneal bone in a modified 3-loop pulley pattern using the previously made bone tunnel for the primary tendon repair. The desmotomy in the superficial digital flexor tendon was closed with simple interrupted sutures using 2-0 polydioxanone. The epitenon was sutured to the length of the semitendinosus flap with 3-0 polydioxanone in simple interrupted sutures. The flap was, therefore, held in place by a 3-loop pulley suture to the tendon or bone and by simple interrupted sutures along its length, laterally and caudomedially, to the epitenon. The epitenon was not closed but was sutured to the
muscle flap. The subcutaneous tissue and skin were reapposed using simple interrupted sutures of 3-0 polydioxanone and 3-0 polypropylene, respectively.
Postoperative Immobilization A bivalved cast was applied to the limb for 2 weeks, then the limb was splinted cranially for 2–6 weeks using 5–7 layers of fiberglass casting material (Vetcastt Plus, 3M Animal Care Products, St. Paul, MN). Dogs were discharged to the owners 1–2 days postoperatively, after bandage changes with the bivalved cast. Owners were instructed to keep the dogs under strict activity restriction and not allow the cast or splint to become soiled at any time. Bandages were changed weekly, or more frequently if they became soiled. After splint removal at 4–8 weeks, dogs were continued under strict activity restriction for another 6 weeks. Return to normal activity was not allowed until 16 weeks. Several owners performed passive range of motion exercises twice daily after splint removal.
Follow-Up Dogs were examined by the first author before surgery and every 2–3 weeks postoperatively. Lameness scores were recorded for each dog at each postoperative time until 12 weeks using a lameness scoring system32 we modified where a score of 0 ¼ stands and walks normally; 1 ¼ stands normally to slight hyperflexion of the tarsus, slight lameness when walking; 2 ¼ stands normally to slight hyperflexion of the tarsus, obvious lameness when walking; 3 ¼ stands abnormally with moderate-to-severe hyperflexion of the tarsus, slight to obvious lameness when walking; and 4 ¼ non-weight-bearing lameness, plantigrade stance on affected pelvic limb. Follow-up information about final outcome was obtained by telephone interview of owners using a questionnaire (Appendix A). For dogs 1 and 3, initial and follow-up ultrasonography examination were performed with a 50-mm-wide linear transducer operating at 12 MHz (iU22, Phillips, Andover, MA). Hair over the calcaneal tendon region was shaved and gel was applied before scanning. Both longitudinal and transverse plane images of the calcaneal tendon were obtained with the dog in lateral recumbency. A moderate amount of flexion was applied to the tarsocrural joint to maintain tension on the calcaneal tendon for optimal evaluation. Images from preoperative and sequential postoperative exams were compared.
RESULTS Five dogs (median age, 5 years; range, 0.75–10 years) were admitted for lameness associated with Achilles tendon rupture. One dog had for bilateral pelvic limb lameness (Table 1). Median weight of the dogs was 24 kg (range, 16–32 kg). Dog 2 had an acute laceration of the Achilles tendon and the other 4 dogs all had chronic progressive lameness and swelling proximal to the calcaneus for an extended period of time.
Blue Heeler 9 m M 16 kg
Whippet 10 y SF 20 kg
Labrador Retriever 8 y M 32 kg
Labrador Retriever 5 y SF 29 kg
2
3
4
5
Right chronic rupture, 41 year lameness duration. Superficial digital flexor intact
Complete right rupture 3 months after partial rupture. Plantigrade stance
Right gastrocnemius tendon rupture. Superficial digital flexor intact
Chronic right progressive lameness. Failed repair with 3-loop pulley suture, tensor fascia lata graft and transarticular external skeletal fixator. Superficial digital flexor intact Acute complete right tendon rupture after laceration 4 days previously, plantigrade stance Left chronic progressive rupture to complete failure over 6 months, plantigrade stance
Injury
y, year; m, months; M, male; CM, castrated male; SF, spayed female.
Labrador Retriever 7 y CM 24 kg
Signalment
1
Dog
3
4
3
4
4
3
Preoperative
2
2
2
2
2
2
3
2
3
2
3
1
1
6
1
1
1
1
1
1
9
0
0
0
0
0
1
12
Postoperative (Weeks)
Lameness Scores
Bilateral tendon rupture, uncontrolled hyperadrenocorticism, ligaments intact but hyperflexion of tarsus present bilaterally, cast sores Postoperative infection with repair breakdown, Repaired—3 loop pulley and medial half of semitendinosus muscle flap Cast sores
None
Acute soft tissue swelling at 6 m, treated for 2 weeks with a dorsal splint
Complications
20
28
37, 33
40
54
Follow-Up (Weeks)
Very satisfied No lameness Hiking
Very satisfied No lameness Hiking, running
Very satisfied No lameness Agility competitor Satisfied, ongoing exercise intolerance and hyperadrenocorticism
Very satisfied No lameness
Owner Assessment
Table 1. Summary Clinical Data and Outcome for 5 Dogs that had Rupture of the Common Calcaneal Tendon Repaired by 3-Loop Pulley Suture and Semitendinosus Muscle Flap Augmentation
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Dog 1 had a chronic ( 3 months) right pelvic limb lameness. On ultrasonographic examination (Fig 1A and B), gastrocnemius tendon avulsion from the calcaneus was observed. The avulsion was repaired using the 3-loop pulley technique, a free tensor fascia lata graft, and transarticular external skeletal fixator.8 Five months later the dog returned for lameness of 2 weeks duration with hyperflexion of the tarsus and digits and gastrocnemius tendon rupture. On ultrasonography, the tendon ends were retracted, and there were hypoechoic areas suggestive of hemorrhage and swelling in the area of the gastrocnemius tendon, and 2 focal areas of mineralization or avulsion fragments (Fig 1C and D). At the 2nd surgery, previous primary repair sutures had broken and the gas-
trocnemius tendon ends were retracted from the calcaneus. The tendon was repaired primarily and a semitendinosus muscle flap performed. Ultrasonographic exam of the repair and semitendinosus flap 2 months later showed longitudinally oriented fibers with no evidence of inflammation or hemorrhage at the previous site (Fig 1E and F). At 6 months, the dog developed lameness and swelling over the Achilles tendon at the insertion to the calcaneus and a partial avulsion of the gastrocnemius tendon was identified on ultrasound (Fig 1G and H). The lameness was mild, grade 1 without hyperflexion of the tarsus, and was treated conservatively for 2 weeks with a cranial splint and cage rest. Hypothyroidism (0.61 mg/dL serum thyroxine,
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T4; reference interval, 1–4 mg/dL) was also diagnosed. After conservative treatment, no lameness recurred (score 0) and the owners are very satisfied with the outcome. Dog 2 had an acute laceration of the Achilles tendon (including the superficial digital flexor tendon) and was treated by primary tendon repair and semitendinosus flap as described earlier. At 8 weeks, mild hyperextension of the tarsus of the affected limb occurred. Rehabilitation with flexion and extension passive range of motion exercises and leash walks was performed and the hyperextension resolved by 12 weeks. The dog had returned to agility competition. Dog 3 was admitted with a plantigrade stance in the left pelvic limb and hyperflexion of the tarsus and digits in the right pelvic limb. On ultrasonography, there was complete Achilles tendon avulsion from the calcaneus, including the superficial digital flexor tendon in the left pelvic limb, and gastrocnemius tendon avulsion from the calcaneus only in the right pelvic limb. The left tendon was surgically repaired as described above 1 month before repair of the right tendon. Both limbs developed superficial bandage-induced wounds as minor complications and no major complications occurred. Despite medical treatment for hyperadrenocorticism diagnosed at the time of the right calcaneal tendon surgery, the dog continued to have generalized weakness, exercise intolerance, polyphagia, and polydipsia-polyuria. The owner was satisfied with the surgical outcome and declined further medical intervention for the hyperadrenocorticism. Dog 4 was admitted with a plantigrade stance in the right pelvic limb after 3 months of progressively worsening lameness after entrapment in a reclining chair. At surgery, complete Achilles tendon rupture was identified
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including the gastrocnemius tendon, superficial digital flexor tendon, and common tendon 3 cm proximal to the calcaneus. The tendon was repaired with a 3-loop pulley suture and semitendinosus flap. One week after repair, infection (Enterobacter sp.) developed at the distal aspect of the surgical site and wound breakdown occurred while in the cast. The wound was treated open with wet-to-dry bandages and enrofloxacin (10 mg/kg, orally once daily for 5 days) was administered before surgical repair. The tendon ends and lateral half of the semitendinosus muscle were debrided, primarily sutured as described above, and the medial remaining half of the semitendinosus muscle transferred to the calcaneus as described above for the lateral half of the muscle. Enrofloxacin (10 mg/kg, orally once daily) was continued for another 11 days and no other complications occurred. Dog 5 was admitted with a 1-year history of progressive lameness. Ultrasonography of the calcaneal tendon identified gastrocnemius tendon rupture with an intact superficial digital flexor tendon. The gastrocnemius tendon was repaired using a semitendinosus flap. Surgical site infection (b-hemolytic Streptococcus sp., Staphylococcus intermedius) developed and was treated with wetto-dry bandages and amoxicillin trihydrate/clavulanate potassium (13.75 mg/kg orally every 12 hours for 14 days) administration and subsequently healed without further complication. Three of the 6 Achilles tendon ruptures were complete and included the superficial digital flexor tendon and 3 were partial with the superficial digital flexor tendon intact (Table 1). Only 1 tendon repair had a major complication (surgical site infection and repair failure) requiring further surgical repair, which was performed
Fig 1. Dog 1: Longitudinal (proximal is to the left, caudal is closest to the probe) and transverse (lateral is to the left) ultrasound images of right calcaneal tendon at the distal aspect, 2–3 cm proximal to the calcaneus. (A) Longitudinal image at the musculotendinous junction with the TC of the calcaneus. Note the hypoechoic areas, suggestive of hemorrhage and fluid accumulation in the CT, white arrow, and avulsion bone fragment or soft tissue calcification, white arrowhead. (B) Transverse image proximal to the calcaneus where inflammation and hemorrhage are visible within the gastrocnemius tendon, white arrow. Avulsion fragment or soft tissue calcification can also been seen, white arrowhead. (C) Longitudinal image of the distal calcaneal tendon 5 months after initial repair with a 3-loop pulley suture and transarticular external skeletal fixator. Note the presence of hypoechoic hemorrhage, enlarged tendon, and retracted ends of the ruptured CT, white arrow. The previously visible avulsion fragment or soft tissue calcification (white arrowhead) is still present, and another, larger and more proximal fragment or calcification is now present (double arrow). (D) Transverse image, 5 months after initial repair. The arrow points to hemorrhage in the gastrocnemius tendon and the arrowhead at the avulsion fragment or soft tissue calcification. Lateral is to the left. (E) Longitudinal image of distal tendon 2 months after repair with a 3-loop pulley suture and semitendinosus flap augmentation. Note the longitudinally aligned fibers of the tendon and semitendinosus flap with no evidence of fiber disruption. (F) Transverse image ( 2 cm proximal to the calcaneus) 2 months after suture and flap repair. (G) Six months after suture and semitendinosus flap repair. The dog had acute lameness of 12 hours duration. Longitudinal image of partial rupture of the conjoined tendon and semitendinosus muscle flap (CT þ ST) can be seen by the hemorrhage and inflammation, (arrowhead) and retracted fibers (small arrow). The polypropylene suture can be seen proximally (large arrow). (H) Six months after suture and semitendinosus flap repair. Transverse image showing a small avulsion fragment or soft tissue calcification (small arrow) and hemorrhage within the gastrocnemius tendon with semitendinosus muscle flap. CT, conjoined tendon of the gastrocnemius, biceps femoris, semitendinosus, and gracilis muscles; SDFT, superficial digital flexor tendon; TC, tuber calcis of the calcaneus; G, gastrocnemius tendon; CT þ ST, conjoined tendon and semitendinosus flap; G þ ST, gastrocnemius tendon and semitendinosus muscle flap.
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similarly to the initial repair, but with the remaining medial half of the semitendinosus muscle as a flap. Minor complications included cast sores, infection, and acute swelling associated with partial breakdown of the flap postoperatively. All minor complications were successfully treated with, depending upon the complication, wetto-dry bandages, cranial splints, systemic antibiotics, and cage rest. Ultrasonography was used in dogs 1 and 3 to determine the location and extent of the injury and to monitor healing postoperatively. In these dogs, ultrasound examination was performed preoperatively and at 8 weeks, and, in dog 1, at the time of lameness and swelling at the semitendinosus flap repair site 6 months postoperatively. In the other 3 dogs, the owners declined ultrasound examination postoperatively and only preoperative images were obtained. Four dogs had healed by 12 weeks and had no signs of lameness (except dog 1) at the 12-week orthopedic examination. Dog 1 had a grade 1 lameness score at 12 weeks, and subsequently developed partial breakdown of the surgical repair at 6 months after a semitendinosus flap. This complication was considered minor because the lesion resolved with only cranial splinting and cage rest for 2 weeks. This dog was diagnosed with hypothyroidism at the time of the partial gastrocnemius tendon rupture 6 months after semitendinosus flap surgery. Owner assessment of outcome was performed by telephone questionnaire at a median of 35 weeks (range, 20– 54 weeks), which was a median of 23 weeks after the last orthopedic examination (Table 1). Four owners were very satisfied with the outcome. The owner of dog 3 stated that the dog continued to have signs of hyperadrenocorticism with exercise intolerance and generalized weakness, although there was no lameness evident in the pelvic limbs. Three dogs have returned to previous activity levels including agility competition and running/ hiking with the owners. The owners of dog 1 do not allow the dog to run or exercise on hard surfaces but do take him hiking.
DISCUSSION We report a technique for repair of Achilles tendon rupture in dogs using a 3-loop pulley suture pattern augmented by a semitendinosus muscle flap transfer using the lateral half of the muscle, supported initially by a bivalve cast (2 weeks) and then a cranial splint (2–6 weeks). The technique was successfully used in 1 dog with a previous failed tendon repair, in 1 dog with an acute laceration, and in 3 dogs with chronic rupture (4 tendons). Augmentation may not have been required in the dog with acute tendon laceration as acute cases may have an ex-
cellent prognosis with primary repair alone.3,19 One dog that we repaired developed partial failure of the repair after surgical site infection, and we were able to achieve repair after a 2nd surgical procedure where the 3-loop pulley suture was replaced and the remaining (medial) half of the semitendinosus muscle flap was transferred. Except for 1 dog with uncontrolled hyperadrenocorticism (not lame after repair and healing), owners were generally satisfied with outcome and 3 dogs returned to previous activity levels. Although this is a small case series, the technique warrants further investigation. Owner assessment of outcome was used similar to previous report of Achilles tendon surgical repairs because a return to previous activity levels by the dog more accurately assesses the endpoint of successful outcome compared with gait or lameness examinations.5 Further characterization of outcome could be achieved by gait platform analysis, however, function under extreme conditions like herding, agility, and unstable surfaces cannot be addressed with this method. Lameness scores were used to assess outcome because the lameness caused by common calcaneal tendon rupture produces a profound gait abnormality including hyperflexion of the tarsus to a complete non-weight-bearing gait; and when standing, laxity of the tendon can be observed by tarsal hyperflexion to a plantigrade stance. Osteoarthritis (not identified in any of our dogs that were radiographed) can produce a more subtle lameness that may require force plate analysis to identify, in contrast to Achilles tendon rupture. Metabolic disease can adversely affect surgical outcome and may have contributed to the complications that occurred postoperatively in some dogs as well as the reduced owner satisfaction in 1 dog.33,34 Two dogs had breakdown of the surgical repair using the semitendinosus flap. Dog 1 was admitted 6 months after repair with a partially ruptured gastrocnemius and semitendinosus muscle flap that was treated conservatively with a cranial splint and cage rest. Dog 4 had a surgical site infection that resulted in repair breakdown and was suspected to be from fecal contamination of the incision postoperatively. Repair was achieved by reapplication of the 3-loop pulley and augmentation with the medial half of the semitendinosus muscle as a flap. No further complications occurred, so transfer of the entire semitendinosus muscle may be possible without negative effects on gait or return to previous activity levels. Only the lateral half of the semitendinosus muscle was used in the other 5 dogs to decrease the size of the muscle flap transferred to the distal tendon and to facilitate closure of the subcutaneous and cutaneous tissues at the time of repair. Splitting the semitendinosus muscle longitudinally has not been reported to our knowledge. Using the entire semitendinosus flap would be possible; however, use of the flap with overlying cutaneous tissues would be recommended facilitate
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closure of the repair distally. Musculocutaneous flaps from the semitendinosus muscle have been used previously, but there is a risk of skin necrosis, especially distally.28 Except for dog 4, only the lateral semitendinosus muscle was transferred and the tissues were carefully dissected to preserve the distal caudal femoral artery supplying the transferred tissue so that a myocutaneous flap could be avoided. Further study of either technique is warranted to determine the method which best facilitates repair of the tendon with the least complications. A limitation of the technique is the long incision (from the ischium to the calcaneus), which may not be cosmetically acceptable for some clients. Two incisions could have been made, 1 proximally to mobilize the semitendinosus flap and a distal incision over the ruptured tendon with the muscle flap tunneled subcutaneously to the distal incision. This method has been performed successfully in 2 dogs (not in this report) with no complications in the first 4 weeks postoperatively. The most common point of rupture of Achilles tendons in people is in the distal one-third of the tendon, 2– 6 cm proximal to the tendinous insertion on the calcaneus.4,9 This region also has the poorest blood supply along the length of the tendon and may develop an altered microstructure after repetitive stress predisposing to tendon rupture.35 Augmentation of the primary repair has been suggested in people and animals to improve the immediate strength of the repair and to induce neovascularization of the tendon to speed healing.23,24 The semitendinosus muscle, as used here, provides blood supply to the tendon, improves host defenses, and improves neovascularization of the tendon ends.25,26,28 In addition, the muscle flap used in these 6 tendon repairs was intended to speed healing of the tendon and improve early strength of the repair with placement of a cellular matrix at the tendon anastomosis site so that the time needed for postoperative immobilization could be reduced.7,9 Immobilization was limited to 8–10 weeks postoperatively and allowed early weight bearing on the limb, theoretically allowing for a stronger repair and less damage to articular cartilage.7,9,18,36 One limitation of this report is a lack of histopathology of the ruptured tendon ends or Doppler assessment of blood flow to characterize the microstructure and vascularity of the ruptured tendon. Further study is needed to understand the mechanism of healing that occurs with the semitendinosus flap compared with primary repair of the tendon alone. Theoretically, the muscle flap provides for neovascularization of the injured tendon, a source of extracellular matrix for rapid increase in tissue strength, and cellular components that stimulate tenocytes and reduce interposing fibrous scar tissue formation. Only 3 of the 6 tendons repaired had interposing fibrous tissue resected before reapposition of the tendon in the primary
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repair. Interposing tissue was not removed if a gap would have remained after placement of the 3-loop pulley suture primary repair. Removal of interposing scar tissue may not be necessary for adequate tendon strength and return to function, especially if resection results in excessive (o3 mm) gap formation, which is associated with increased postoperative complications.9,14,37 Ultrasonographic examination was used to determine the extent of the lesion in the common calcaneal tendon5,38,39 as well as to document healing in 2 dogs. We found ultrasonography useful as a diagnostic tool for evaluating which components of the calcaneal tendon were ruptured, as well as for assessment of postoperative inflammation at the surgical site. Further investigation into the usefulness of ultrasound as a method of determining completion of healing is warranted. We immobilized limbs with a bivalved cast for 2 weeks and then a cranial splint for 2–6 weeks. External coaptation was used because it allowed partial weight bearing. In people, controlled motion has resulted in shorter healing times and improved tendon strength, and in rabbits early loading of the Achilles tendon results in a twofold increase in tendon strength.40,41 Although prolonged casting may result in reduced articular cartilage loading, a transarticular external skeletal fixator across the tarsal joint for prolonged immobilization causes articular cartilage deterioration.36 Even though a transarticular external skeletal fixator or calcaneo-tibial screw used for o3 weeks would have been unlikely to cause cartilage damage, it was not used in our dogs because both an external skeletal fixator and calcaneo-tibial screw can result in iatrogenic fracture.19 A calcaneo-tibial screw was also not chosen for immobilization because it requires further second surgery to remove the implant and the use of a cast in addition to the screw to prevent screw loosening.16–18 Further, no single method of postoperative immobilization has been shown to improve clinical outcome over any other.19 Approximately 70% of working dogs have a good outcome after primary calcaneal tendon repair without augmentation, however, recurrence and lameness can occur.5 In our dogs, 4/5 had an owner-assessed outcome as very satisfactory, although only 3 have returned to previous activity levels. The other 2 dogs had underlying metabolic diseases, which may have altered the final outcome as well as owner satisfaction. Chronic injuries are more problematic to treat than acute lacerations and may carry a poorer prognosis because tendon and muscular contracture develops along with fibrous scar tissue at the ruptured tendon ends. Supplementation with a semitendinosus flap may offer the advantage of improved blood supply earlier in the course of healing, thus allowing earlier return to weight bearing and a decreased incidence of recurrence in dogs.
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REFERENCES 1. Evans HE: Miller’s Anatomy of the Dog (ed 3). Philadelphia, PA, Saunders, 1993 2. Vaughan LC: The use of carbon fibre implants for the repair of Achilles tendon rupture in dogs. J Small Anim Pract 22:629–634, 1981 3. King M, Jerram R: Achilles tendon rupture in dogs. Compend Contin Educ Pract Vet 25:613–620, 2003 4. Reinke JD, Mughannam AJ, Owens JM: Avulsion of the gastrocnemius tendon in 11 dogs. J Am Anim Hosp Assoc 29:410–418, 1993 5. Worth AJ, Danielsson F, Bray JP, et al: Ability to work and owner satisfaction following surgical repair of common calcaneal tendon injuries in working dogs in New Zealand. N Z Vet J 52:109–116, 2004 6. Bonneau NH, M O, Breton L: Avulsion of the gastrocnemius tendon in the dog causing flexion of the hocks and digits. J Am Anim Hosp Assoc 19:717–722, 1983 7. Guerin S, Burbidge HM, Firth E, et al: Achilles tenorrhaphy in five dogs: a modified surgical technique and evaluation of a cranial half cast. Vet Comp Orthop Traumatol 11:205– 210, 1998 8. Shani J, Shahar R: Repair of chronic complete traumatic rupture of the common calcaneal tendon in a dog using a fascia lata graft. Vet Comp Orthop Traumatol 13:104–108, 2000 9. Maffulli N: Rupture of the Achilles tendon. J Bone Joint Surg [Am] 81:1019–1036, 1999 10. Leppilahti J, Orava S: Total Achilles tendon rupture. A review. Sports Med 25:79–100, 1998 11. Shakibaei M, de Souza P, van Sickle D, et al: Biochemical changes in Achilles tendon from juvenile dogs after treatment with ciprofloxacin or feeding a magnesiumdeficient diet. Arch Toxicol 75:369–374, 2001 12. Lim S, Hossain MA, Park J, et al: The effects of enrofloxacin on canine tendon cells and chondrocytes proliferation in vitro. Vet Res Commun 32:243–253, 2008 13. Moores AP, Comerford EJ, Tarlton JF, et al: Biomechanical and clinical evaluation of a modified 3-loop pulley suture pattern for reattachment of canine tendons to bone. Vet Surg 33:391–397, 2004 14. Gelberman RH, Boyer MI, Brodt MD, et al: The effect of gap formation at the repair site on the strength and excursion of intrasynovial flexor tendons. J Bone Joint Surg [Am] 81:975–982, 1999 15. Berg JR, Egger EL: In vitro comparison of the three loop pulley and locking loop surture patterns for repair of canine weightbearing tendons and collateral ligaments. Vet Surg 15:107–110, 1986 16. Morshead D, Leeds EB: Kirschner–Ehmer apparatus immobilization following Achilles tendon repair in six dogs. Vet Surg 13:11–14, 1984 17. deHaan JJ, Goring RL, Renberg C: Modified transarticular external skeletal fixation for support of Achilles tenorrhaphy in four dogs. Vet Comp Orthop Traumatol 8:32– 35, 1995
18. Sivacolundhu RK, Marchevsky AM, Read RA, et al: Achilles mechanism reconstruction in four dogs. Vet Comp Orthop Traumatol 14:25–31, 2001 19. Nielsen C, Pluhar GE: Outcome following surgical repair of Achilles tendon rupture and comparison between post-operative immobilization methods in dogs. Vet Comp Orthop Traumatol 19:246–249, 2006 20. Schulz K: Management of muscle and tendon injury or disease, in Fossum TW (ed): Small Animal Surgery (ed 3). St Louis, MO, Mosby, 2007, pp 1316–1332 21. Fernandez-Fairen M, Gimeno C: Augmented repair of Achilles tendon ruptures. Am J Sports Med 25:177–181, 1997 22. Wapner KL, Hecht PJ, Mills RH Jr: Reconstruction of neglected Achilles tendon injury. Orthop Clin North Am 26:249–263, 1995 23. Lee DK: Achilles tendon repair with acellular tissue graft augmentation in neglected ruptures. J Foot Ankle Surg 46:451–455, 2007 24. Gilbert TW, Stewart-Akers AM, Simmons-Byrd A, et al: Degradation and remodeling of small intestinal submucosa in canine Achilles tendon repair. J Bone Joint Surg [Am] 89-A:621–630, 2007 25. Basher AW, Presnell KR: Muscle transposition as an aid in covering traumatic tissue defects over the canine tibia. J Am Animal Hosp Assoc 23:617–628, 1987 26. Richards RR, Mahoney JL, Minas T: Influence of soft tissue coverage on the healing of cortical defects in canine diaphyseal bone. Ann Plast Surg 16:296–304, 1986 27. Byrd HS, Cierny G III, Tebbetts JB: The management of open tibial fractures with associated soft-tissue loss: external pin fixation with early flap coverage. Plast Reconstr Surg 68:73–82, 1981 28. Puerto DA, Aronson LR: Use of a semitendinosus myocutaneous flap for soft-tissue reconstruction of a grade IIIB open tibial fracture in a dog. Vet Surg 33:629–635, 2004 29. Chambers JN, Rawlings CA: Applications of a semitendinosus muscle flap in two dogs. J Am Vet Med Assoc 199:84–86, 1991 30. Chambers JN, Purinton PT, Allen SW, et al: Identification and anatomic categorization of the vascular patterns to the pelvic limb muscles of dogs. Am J Vet Res 51:305–313, 1990 31. Solano M, Purinton PT, Chambers JN, et al: Effects of vascular pedicle ligation on blood flow in canine semitendinosus muscle. Am J Vet Res 56:731–735, 1995 32. Cross AR, Budsberg SC, Keefe TJ: Kinetic gait analysis assessment of meloxicam efficacy in a sodium urate-induced synovitis model in dogs. Am J Vet Res 58:217–224, 1997 33. Ahlgren SA: Bilateral rupture of the Achilles tendons and cushing’s syndrome. Case report. Acta Chir Scand 125: 376–378, 1963 34. Ekmektzoglou KA, Zografos GC: A concomitant review of the effects of diabetes mellitus and hypothyroidism in wound healing. World J Gastroenterol 12:2721–2729, 2006 35. Reinke JD: Treatment of avulsion of the gastrocnemius tendon, in Bojrab MJ, Ellison G, Slocum B (eds): Current Techniques in Veterinary Surgery (ed 4). Baltimore, Williams & Wilkins, 1998, pp 1257–1260
BALTZER AND RIST 36. Keller WG, Aron DN, Rowland GN, et al: The effect of trans-stifle external skeletal fixation and hyaluronic acid therapy on articular cartilage in the dog. Vet Surg 23:119– 128, 1994 37. Gigante A, Moschini A, Verdenelli A, et al: Open versus percutaneous repair in the treatment of acute Achilles tendon rupture: a randomized prospective study. Knee Surg Sports Traumatol Arthrosc 16:204–209, 2008 38. Rivers BJ, Walter PA, Kramek B, et al: Sonographic findings in canine common calcaneal tendon injury. Vet Comp Orthop Traumatol 10:45–53, 1997 39. Lamb CR, Duvernois A: Ultrasonographic anatomy of the normal canine calcaneal tendon. Vet Radiol Ultrasound 46:326–330, 2005 40. Mortensen HM, Skov O, Jensen PE: Early motion of the ankle after operative treatment of a rupture of the Achilles tendon. A prospective, randomized clinical and radiographic study. J Bone Joint Surg [Am] 81:983–990, 1999 41. Enwemeka CS: Functional loading augments the initial tensile strength and energy absorption capacity of regenerating rabbit Achilles tendons. Am J Phys Med Rehabil 71:31–38, 1992
APPENDIX A: OWNER QUESTIONNAIRE MODIFIED FROM WORTH ET AL.5 (1) What type of substrate or property does your dog live on or spend the most amount of time exercising on? (a) (b) (c) (d) (e)
Concrete or blacktop Grass fields Flat dirt or forest trails Rolling dirt or forest trails Various terrain considered more strenuous than above
(2) How many hours per day on average does the dog spend exercising? (exercise is defined as anything walking þ . . .) (a) (b) (c) (d) (e)
o1 hour 1–2 hours 2–3 hours 4–5 hours 6 þ hours
(3) Is lameness involved with exercise or after prolonged periods of rest? (lameness defined as any change in stride) (a) Exercise (i) Yes (ii) No (b) Rest (i) Yes (ii) No
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(4) Describe the role/s of the dog other then companion? (a) (b) (c) (d) (e)
Working dog Fly ball Running partner Agility competitions Other
(5) How badly was the dog affected at the time of injury?
(a) Unaffected (b) Mild, intermittent lameness (c) Mild persistent lameness (d) Moderate, persistent lameness, intermittent non weight bearing (e) Severe, persistent lameness, non weight bearing at walk/trot (f) Non weight bearing even at rest
¼0 ¼1 ¼2 ¼3 ¼4 ¼5
(6) Postsurgery, how has the injury affected the use of the dog? (a) Performs all normal activities that were done prior to surgery (b) Can perform most activities that were done prior to the surgery but not as well as prior to injury (c) Can perform some activities that were done prior to surgery but is very limited (d) Can perform very few activities that were done prior to the surgery (e) Can perform no activities that were done prior to surgery (7) Did the results of the surgery meet your expectations? (a) Yes (b) No (8) In retrospect, was the financial investment worthwhile? (a) Yes (b) No (9) Overall, how would you rate your level of satisfaction? (a) (b) (c) (d) (e)
Very satisfied Satisfied Fair Disappointed Very disappointed
(10) On the injured side, does the dog still have a noticeably more bent ankle than the other leg? (a) Yes (b) No