ix
Table of contents
1
Spine classification systems to spine disease severity measures: a paradigm shift… ……………………………………………………………………………………………………1
2
Method for identifying and evaluating spine severity measures… ………………………………………9
3
What makes a quality severity measure?… ………………………………………………………………… 17
4
How the severity measures are displayed in this book…………………………………………………… 25
5 Spine disease severity measures… …………………………………………………………………………… 29 5.1 General disease severity measures… ……………………………………………………………………… 31 Instability severity measures… ……………………………………………………………………………… 43 5.2 5.3.1 Deformity severity measures: scoliosis……………………………………………………………………… 63 5.3.2 Deformity severity measures: kyphosis… ………………………………………………………………… 99 5.3.3 Deformity severity measures: ankylosing disorders… ………………………………………………… 107 5.3.4 Deformity severity measures: spondylolisthesis………………………………………………………… 141 Degenerative measures: cervical myelopathy…………………………………………………………… 155 5.4.1 5.4.2 Degenerative measures: degenerative disc disease… ………………………………………………… 177 5.5 Osteoporosis severity measures…………………………………………………………………………… 213 5.6 Infection severity measures………………………………………………………………………………… 235 5.7 Tumor severity measures…………………………………………………………………………………… 259 5.8 Stenosis severity measures… ……………………………………………………………………………… 299 5.9 Heterotopic ossification… ………………………………………………………………………………… 307 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7
Spine trauma severity measures… ………………………………………………………………………… General trauma severity measures………………………………………………………………………… Spinal cord injury severity measures……………………………………………………………………… Upper cervical spine trauma classification systems… ………………………………………………… Lower cervical spine trauma classification systems… ………………………………………………… Thoracolumbar spine trauma classification systems…………………………………………………… Lumbosacral spine trauma classification systems……………………………………………………… Whole spine trauma classification systems … …………………………………………………………
317 319 331 355 401 437 485 503
7
Going beyond classification systems: new horizons for adolescent idiopathic scoliosis… …………………………………………………… 519
Glossary of terms and abbreviations………………………………………………………………………………… 524 List of assessed measures……………………………………………………………………………………………… 528
43
Allan F Tencer
5
Spine disease severity measures
5.2
1
Instability severity measures
Introduction to posttraumatic stability as related to classification systems
Biomechanical observations
A spinal injury classification system should provide information as to the extent of injury in structural and neurologic dimensions to aid in selecting the most appropriate treatment. Based on available outcomes in the literature, integrity of neurologic function is a prevalent parameter towards the final result. Similarly, preservation of neurologic function by correctly predicting structural stability is of high clinical concern. Therefore, a classification system should be able to predict the severity of neurological injury or risk of incurring a secondary neurologic deficit using observable postinjury measures. A widely used technique to measure the extent of spinal trauma is derived from imaging the canal space postimpact and assessing the degree to which the midsagittal canal diameter has been occluded. However, it has been difficult to directly correlate the degree of neurotrauma with the observed geometric occlusion [1–5], even though occlusion should correlate with cord compression. A possible explanation for this apparent lack of correlation may be due to the elastic nature
of the spine during impact. As the maximum load is reached, the spine deforms and the cord is occluded, but as the load is released the spine recovers some of its deformation, regaining height loss and reducing canal occlusion. Therefore the maximum occlusion of the canal, and the effect, transiently, on the cord may be significantly greater than that observed by postinjury radiography. Similarly, the static images obtained in a recumbent fashion with CT scan and MRI fail to take into account the potential of an injured spine segment to undergo secondary deformation under physiologic loads. Biomechanical testing
The potential for dynamic vertebral deformation was tested in a fresh cadaveric experiment, shown in Fig 5.2-1, with vertical compressive or compression/flexion loads applied. Volumetric and pressure changes to the spinal canal could be measured with a malleable plastic tube and a saline pump system attached [6]. The results shown in Fig 5.2-2 indicated a significant difference between occlusion measured during impact,
5
Spine disease severity measures
Load pin 80
Pump Pressure transducer
Transient 70
Load frame
Immediate P-I 60
Water tank
Flow
Specimen
Tygon tubing
MSD occlusion (%)
44
Clinical P-I 50 40 30 20 10 0
Load frame
Fig 5.2-1 Method for measuring transient mid-sagittal diameter of the spinal canal during and post impact using a tube placed in the canal with fluid flow circulated by a pump. A pressure transducer measures occlusion and a dynamic pressure change [6].
Spine Classifications and Severit y Measures
Fast
Slow Loading rate
Fig 5.2-2 Results from impact (fast) and compressive (slow) loading. Mid sagittal diameter (MSD) occlusion is expressed as a percentage of normal canal diameter. The greatest occlusion occurred during impact and decreased post impact and during CT scanning (clinical) [6].
5.2
45
Instability severity measures
2
immediately postimpact, and by postinjury CT scanning. During impact, the maximum canal occlusion (decrease in the midsagittal diameter) was 71.5%. Immediately post impact (while still in the test frame), it averaged 46.7%, demonstrating the amount of initial elastic recovery of the spine, and after removal of specimens and CT scanning, the average canal occlusion had decreased to 21.5%. The decrease from transient to postimpact canal midsagittal diameter was 70%. Therefore, most of the canal occlusion had disappeared postimpact. These findings, from the perspective of laboratory testing, demonstrate why it may be difficult to relate post-traumatic measured canal compromise with the actual occlusion that had occurred during the traumatic event. It stands to reason that a similar observation could be made for sagittal angular deformation, with a transient major bending deformation partially reducing by “springing back”. In addition, a spontaneous traumatic deformity reduction may be expected with recumbent patient positioning. Further variables to consider in measuring sagittal angular deformation can be expected with patient body habitus, mobility of spine segments, and type of support structure, such as a rigid board versus a soft mattress. In this context determination of injury severity by measuring static post-traumatic images in a number of dimensions may well under appreciate the actual deformation that the spinal column underwent at the point of impact.
Treatment consideration
A spinal injury classification system should also be a guide to the surgeon as to how to best stabilize the injured spine mechanically to prevent further damage to the neurological structures. We hypothesized that different spinal fracture patterns result in different patterns of damage and that some of the load carrying structures (the facets for example) may remain intact after specific types of trauma. In a different set of in-vitro tests we set out to identify the residual mechanical stability related to the type of fracture produced in the thoracolumbar spine. Mechanical stability of the spine pre and postinjury was defined in terms of the neutral zone concept described by Panjabi [7]. The neutral zone is an area in which the spinal motion segment can be positioned without applying significant load, and in which the spine will remain after the load is released. Every normal joint has a range of motion in which it displaces without requiring the application of significant load. When the joint is injured, this range increases. The neutral zone provides an easy to visualize method for describing the remaining spinal joint stability. For this series of experiments, thoracolumbar spinal fractures encompassing compression injuries, flexion-distraction injuries, as well as burst fractures were created by impact. Once damaged, loads were applied to specimens in flexion, left lateral bending, extension, right lateral bending, and torsion and in combinations of these loads. For each measurement, the load on the specimen was applied and then released, and the position of the center of the vertebra measured. The measured positions described an area in the horizontal plane, which correlated to the particular type of fracture induced. The outer boundary of the area is the limit of the unstable region, since load is required to move in any direction outside the boundary of the neutral zone.
5
Spine disease severity measures
Fig 5.2-3a demonstrates the difference in neutral zones be-
tween an intact vertebral motion segment and the same one after compression fracture. The specimen maintained almost complete mechanical integrity in flexion/extension/lateral bending as indicated by how the intact and injured specimen neutral zone boundaries overlap. However, the torsional neutral zone was increased significantly. In contrast, as Fig 5.2-3b shows, a burst fracture has a much wider neutral zone boundary in flexion and right and left lateral bending.
20
15
15
10 5 0 -5 -10
Specimen no.1 Intact Injured
10 5 0 -5 -10
Specimen no.15 Intact Injured
-15
(deg) -20 -15 -10 -5 0 5 10 15 20 (L) Lateral bending (R)
Extension / flexion
60
15
-15
1
2
3
4
Torsional NZ range (deg) (combined CW and CCW)
-5 -10
Specimen no.22 Intact Injured
Intact Injured 0
b
5 0
(deg) -20 -15 -10 -5 0 5 10 15 20 (L) Lateral bending (R)
Intact Injured 0
10
-15
(deg) -20 -15 -10 -5 0 5 10 15 20 (L) Lateral bending (R)
Intact Injured
a
Currently, the concept of a “neutral zone” has become a well recognized biomechanical term utilized widely in research endeavors. As the graphs show it is possible to express spinal stability increasingly well in a graphic fashion in an in-vitro setting. At this point, we currently still lack a translational application which would allow a neutral zone diagram to be applied to any given patient’s fracture based on expected biomechanical performance of the injured segment in order to allow the treating physician to choose the most appropriate care from a variety of nonsurgical or operative options. However, these results do indicate generally how different fracture patterns affect remaining mechanical stability of the spine after injury.
20 Extension / flexion
Extension / flexion
46
1
2
3
4
Torsional NZ range (deg) (combined CW and CCW)
5
0 c
1
2
3
4
Torsional NZ range (deg) (combined CW and CCW)
Fig 5.2-3a–c a Neutral zone map of a lumbar specimen intact and after compressive fracture (the neutral zone is the area over which the specimen can be positioned without applying a significant force and where it will remain after the force is released. b Burst fracture. c Flexion-distraction injury [8].
Spine Classifications and Severit y Measures
5.2
Instability severity measures
3
Summary
In summary, the current attempts at identifying ‘spinal stability’ remain somewhat arbitrary, subjective, and are largely empirically based. Under-appreciation of spinal injury severity based on reliance on static recumbent postinjury films remains a real danger in management aspects. Ultimately preservation of neurologic function and optimization of its recovery potential in case of injury with restoration of a pain-free and physiologically aligned spinal column remain the parameters used for identifying a structurally stable spine. Hopefully translational research will enable application of visual decision-making aids in the future to help in determining stability needs of patients.
47
4
References
1. Denis F (1983) The three column spine and its significance in the classification of acute thoracolumbar spinal injuries. Spine; 8:817–831. 2. Fontijne WP, de Klerk LW, Braakman R, et al (1992) CT scan prediction of neurological deficit in thoracolumbar burst fractures. J Bone Joint Surg Br; 74:683–685. 3. Hashimoto T, Kaneda K, Abumi K (1988) Relationship between traumatic spinal canal stenosis and neurologic deficits in thoracolumbar burst fractures. Spine; 13:1268–1272. 4. Kang JD, Figgie MP, Bohlman HH (1994) Sagittal measurements of the cervical spine in subaxial fractures and dislocations. An analysis of two hundred and eighty–eight patients with and without neurological deficits. J Bone Joint Surg Am; 76:1617–1628. 5. Kilcoyne RF, Mack LA, King HA, et al (1983) Thoracolumbar spine injuries associated with vertical plunges: reappraisal with computed tomography. Radiology; 146:137–140. 6. Carter JW, Mirza SK, Tencer AF, et al (2000) Canal geometry changes associated with axial compressive cervical spine fracture. Spine; 25:46–54. 7. Panjabi MM (1992) The stabilizing system of the spine. Part II. Neutral zone and instability hypothesis. J Spinal Disord; 5:390–396. 8. Ching RP, Tencer AF, Anderson PA, et al (1995) Comparison of residual stability in thoracolumbar spine fractures using neutral zone measurements. J Orthop Res; 13:533–541.
48
5
Spine disease severity measures
1 Frymoyer Classification of Degenerative Segmental Instability Frymoyer JW, Selby DK (1985) Segmental instability. Rationale for treatment. Spine; 10:280–286.
Scale Description
Scale Illustration
Degenerative segmental instabilities classified based on clinical, radiographic and biomechanical considerations: • • • •
Y
F Force Load M Movement
Type I—Axial rotational Type II—Translational Type III—Retrolisthetic Type IV—Postsurgical
T Translation R Rotation
Interpretation: Descriptive of segmental instability. One type not necessarily more severe than the next.
Z
Fig 5.2.1-1 Schematic drawings demonstrates the possible displacements that can occur along each of the three mutually perpendicular major axis of the spine. Coupling can occur between rotations and translations, and specific patterns exist for each lumbar vertebral level (from White and Panjabi).
Spine Classifications and Severit y Measures
X
Displacement
5.2
49
Instability severity measures
Methodology
Content
No predictive validity or reliability studies were identified.
Anatomical
Predictive validity
Interobserver reliability
Intraobserver reliability
Not tested
Reliability Population tested in
ch Biome anical
Predictive validity
ee of severit y
Outcome
Degr
Population tested in
Clinical
Not tested
Rating Content
●○
Content validity
–
Anatomical
½ ½
Biomechanical Clinical Degree of severity
–
Methodology Predictive validity
○○
Index population
–
Test population
–
○○
Reliability Interobserver
–
Intraobserver
–
Clinical utility Simple and easy to remember
●○
Three categories or less
–
Single phrase
1
Directs treatment
●○
Index population
1
Test population
–
Total 3/10
●●●○○○○○○○
50
5
Spine disease severity measures
2 Posner Lumbar Instability Checklist Posner I, White AA 3rd, Edwards WT, et al (1982) A biomechanical analysis of the clinical stability of the lumbar and lumbosacral spine. Spine; 7:374–389. White AA 3rd, Panjabi MM, Posner I, et al (1981) Spinal stability: evaluation and treatment. Instr Course Lect; 30:457-483. Scale Description
Scale Illustration
Checklist of elements for instability in lumbar spine:
11°
• Cauda equina damage (3 points) • Relative flexion sagittal plane translation > 16% or extension sagittal plane translation > 12% (2 points) • Relative flexion sagittal plane rotation > 11 degrees (2 points) • Anterior elements destroyed (2 points) • Posterior elements destroyed (2 points) • Dangerous loading anticipated (1 point)
37.5 mm 6mm
Interpretation: Sum of elements. Maximum score: 12 points Minimum score: 0 points A total score of 5 or more is considered clinically unstable.
a
b
a a a > 16% c
d
γ
γ > 11° e
Spine Classifications and Severit y Measures
a > 12%
Fig 5.2.2-1a– e a Fracture angulation. b Neural element injury. c Anterolisthesis. d Retrolisthesis. e Sagittal kyphosis.
5.2
51
Instability severity measures Content
Scale Illustration (cont)
Anatomical
ee of severit y
ch Biome anical
Degr
a
b Clinical
Fig 5.2.2-2a–b a Anterior elements. b Posterior elements.
Rating Content
●●
Content validity Anatomical
½
Biomechanical Clinical
½ ½
Degree of severity
½
Methodology
Methodology No predictive validity or reliability studies were identified.
○○
Index population
–
Test population
–
○○
Reliability
Predictive validity Population tested in
Predictive validity
Outcome
Predictive validity
Not tested
Interobserver
–
Intraobserver
–
Clinical utility Simple and easy to remember
Reliability Population tested in Not tested
Interobserver reliability
Intraobserver reliability
●○
Three categories or less
–
Single phrase
1
Directs treatment
●○
Index population
1
Test population
–
Total 4/10
●●●●○○○○○○
5
Spine disease severity measures
3 Posner Lumbosacral Instability Checklist Posner I, White AA 3rd, Edwards WT, et al (1982) A biomechanical analysis of the clinical stability of the lumbar and lumbosacral spine. Spine; 7:374–389. White AA 3rd, Panjabi MM, Posner I, et al (1981) Spinal stability: evaluation and treatment. Instr Course Lect; 30:457-483. Scale Description
Scale Illustration
Checklist of elements for instability in lumbosacral spine: • Cauda equina damage (3 points) • Relative flexion sagittal plane translation > 6% or extension sagittal plane translation > 9% (2 points) • Relative flexion sagittal plane rotation < 1 degree (2 points) • Anterior elements destroyed (2 points) • Posterior elements destroyed (2 points) • Dangerous loading anticipated (1 point)
a a = 6%
b
a
Interpretation: Sum of elements.
γ
52
Maximum score: 12 points Minimum score: 0 points
a
γ = <1°
A total score of 5 or more is considered clinically unstable. a = 9% c
Fig 5.2. 3-1a–d a Anterior and posterior elements. b Sagittal plane translation. c Segmental motion. d Retrolisthesis.
Spine Classifications and Severit y Measures
d
5.2
53
Instability severity measures
Methodology
Content
No predictive validity or reliability studies were identified.
Anatomical
Predictive validity
Interobserver reliability
Intraobserver reliability
Not tested
Reliability Population tested in
ch Biome anical
Predictive validity
ee of severit y
Outcome
Degr
Population tested in
Clinical
Not tested
Rating Content
●●
Content validity Anatomical
½
Biomechanical Clinical
½ ½
Degree of severity
½
Methodology Predictive validity
○○
Index population
–
Test population
–
○○
Reliability Interobserver
–
Intraobserver
–
Clinical utility Simple and easy to remember
●○
Three categories or less
–
Single phrase
1
Directs treatment
●○
Index population
1
Test population
–
Total 4/10
●●●●○○○○○○
54
5
Spine disease severity measures
4 White and Panjabi C1-C2 Instability Criteria White AA 3rd, Panjabi MM, Posner I, et al (1981) Spinal stability: evaluation and treatment. Instr Course Lect; 30:457–483.
Scale Description
Scale Illustration
Summary of C1-C2 subluxations and dislocations: • • • • •
Type I—Bilateral anterior Type II—Bilateral posterior Type III—Unilateral anterior Type IV—Unilateral posterior Type V—Unilateral combined
C1-C2 instability criteria: • • • •
a
Spence’s more than 7 mm total Ring <-> Odontoid space more than 3 mm Avulsed transverse ligament Neurologic deficit
Interpretation: If any of the criteria is true instability is present.
b
d Fig 5.2.4-1a–f a Normal. b Type I—Bilateral anterior. c Type II—Bilateral posterior. d Type III—Unilateral anterior. e Type IV—Unilateral posterior. f Type V—Unilateral combined.
Spine Classifications and Severit y Measures
c
e
f
5.2
55
Instability severity measures
Methodology
Content
No predictive validity or reliability studies were identified.
Anatomical
Predictive validity
Interobserver reliability
Intraobserver reliability
Not tested
Reliability Population tested in
ch Biome anical
Predictive validity
ee of severit y
Outcome
Degr
Population tested in
Clinical
Not tested
Rating Content
●◐
Content validity Anatomical
½
Biomechanical
½ ½
Clinical Degree of severity
–
Methodology Predictive validity
○○
Index population
–
Test population
–
○○
Reliability Interobserver
–
Intraobserver
–
Clinical utility Simple and easy to remember
●○
Three categories or less
–
Single phrase
1
Directs treatment
●○
Index population
1
Test population
–
Total 3.5/10
●●●◐○○○○○○
56
5
Spine disease severity measures
5 White and Panjabi Occiput-C1 Instability Criteria White AA 3rd, Panjabi MM, Posner I, et al (1981) Spinal stability: evaluation and treatment. Instr Course Lect; 30:457–483.
Scale Description Occiput-C1 instability criteria:
Scale Illustration 4–5mm
• Dens (tip) to basion of occiput–4 to 5 mm • Flexion-extension translation—1 mm • Neurologic signs or symptoms Interpretation: If any of the criteria is true instability is present.
Fig 5.2.5-1 The distance between the basion of the occiput and the top of the dens is 4 to 5 mm. An increase of more than 1 mm in this distance with flexion-extension views is believed to indicate instability.
Spine Classifications and Severit y Measures
5.2
57
Instability severity measures
Methodology
Content
No predictive validity or reliability studies were identified.
Anatomical
Predictive validity
Interobserver reliability
Intraobserver reliability
Not tested
Reliability Population tested in
ch Biome anical
Predictive validity
ee of severit y
Outcome
Degr
Population tested in
Clinical
Not tested
Rating Content
●◐
Content validity Anatomical
½
Biomechanical
½ ½
Clinical Degree of severity
–
Methodology Predictive validity
○○
Index population
–
Test population
–
○○
Reliability Interobserver
–
Intraobserver
–
Clinical utility Simple and easy to remember
●●
Three categories or less
1
Single phrase
1
Directs treatment
○○
Index population
–
Test population
–
Total 3.5/10
●●●◐○○○○○○
58
5
Spine disease severity measures
6 White and Panjabi Middle and Lower Cervical Instability Checklist* White AA, Panjabi NM (1978) Clinical Biomechanics of the Spine. JB Lippincott: Philadelphia, 314
Scale Description
Scale Illustration
Checklist of elements for instability in middle and lower cervical spine: • • • • • • • • • •
Anterior elements destroyed or unable to function (2 points) Posterior elements destroyed or unable to function (2 points) Relative sagittal plane translation > 3.5 mm (2 points) Relative sagittal plane rotation > 11 degrees (2 points) Spinal cord damage (2 points) Positive stretch test (2 points) Abnormal disc narrowing (1 point) Developmentally narrow spinal column (1 point) Nerve root damage (1 point) Dangerous loading anticipated (1 point)
> 3.5mm
a
Interpretation: Sum of elements. C4
Maximum score: 16 points Minimum score: 0 points
C5
A total score of 5 or more is considered clinically unstable.
-2° +20°
* In later checklists published by White and Panjabi [1–4] the developmentally narrow spinal column element was omitted. Interpretation: Sum of elements. Maximum score: 15 points Minimum score: 0 points The higher the score, the greater the instability. A total score of 5 or more is considered clinically unstable. * Later checklists: 1. White AA 3rd, Panjabi MM, Posner I, et al (1981) Spinal stability: evaluation and treatment. Instr Course Lect; 30:457–483. 2. Panjabi MM, Thibodeau LL, Crisco JJ 3rd, et al (1988) What constitutes spinal instability? Clin Neurosurg; 34:313–339. 3. White AA 3rd, Panjabi MM (1984) The role of stabilization in the treatment of cervical spine injuries. Spine; 9:512–522. 4. White AA 3rd, Panjabi MM (1987) Update on the evaluation of instability of the lower cervical spine. Instr Course Lect; 36:513–520.
Spine Classifications and Severit y Measures
-4° b Fig 5.2.6 -1a–b a Sagittal plane translation. b Sagittal plane rotation.
C6 C7
5.2
59
Instability severity measures
Scale Illustration (cont)
Content Anatomical
ee of severit y
ch Biome anical
Degr
c
d
e Clinical
Fig 5.2.6 -1c– e c Anterior elements. d Posterior elements. e Neural element injury.
Rating Content
●●
Content validity
Methodology No predictive validity or reliability studies were identified.
½
Biomechanical Clinical
½ ½
Degree of severity
½
Methodology
Predictive validity Population tested in
Anatomical
Outcome
Predictive validity
Not tested
Predictive validity
○○
Index population
–
Test population
–
○○
Reliability Reliability Population tested in Not tested
Interobserver reliability
Intraobserver reliability
Interobserver
–
Intraobserver
–
Clinical utility Simple and easy to remember
●○
Three categories or less
–
Single phrase
1
Directs treatment
●○
Index population
1
Test population
–
Total 4/10
●●●●○○○○○○
60
5
Spine disease severity measures
7 White and Panjabi Thoracic and Thoracolumbar Instability Checklist White AA 3rd, Panjabi MM, Posner I, et al (1981) Spinal stability: evaluation and treatment. Instr Course Lect; 30:457–483.
Scale Description
Scale Illustration
Checklist of elements for instability in thoracic and thoracolumbar spine: • • • • • • •
5°
Anterior elements destroyed or unable to function (2 points) Posterior elements destroyed or unable to function (2 points) Relative sagittal plane translation > 2.5 mm (2 points) Relative sagittal plane rotation > 5 degrees (2 points) Spinal cord or cauda equina damage (2 points) Disruption of costovertebral articulations (1 point) Dangerous loading anticipated (2 points)
Interpretation: Sum of elements. Maximum score: 13 points Minimum score: 0 points A total score of 5 or more is considered clinically unstable.
a
b
a c
Fig 5.2.7-1a–d a Fracture angulation. b Neural element injury. c Anterolisthesis. d Disruption of costovertebral articulations.
Spine Classifications and Severit y Measures
d
5.2
61
Instability severity measures
Methodology
Content
No predictive validity or reliability studies were identified.
Anatomical
Predictive validity
Interobserver reliability
Intraobserver reliability
Not tested
Reliability Population tested in
ch Biome anical
Predictive validity
ee of severit y
Outcome
Degr
Population tested in
Clinical
Not tested
Rating Content
●●
Content validity Anatomical
½
Biomechanical Clinical
½ ½
Degree of severity
½
Methodology Predictive validity
○○
Index population
–
Test population
–
○○
Reliability Interobserver
–
Intraobserver
–
Clinical utility Simple and easy to remember
●○
Three categories or less
–
Single phrase
1
Directs treatment
●○
Index population
1
Test population
–
Total 4/10
●●●●○○○○○○