Abstract
Background: It has been reported that there is poor correlation between neurological injury and degree of bony retropulsion in thoracolumbar burst fractures1. Wilcox et al2 showed biomechanically that there was poor concordance between the extent of post impact spinal canal occlusion and the maximum amount of occlusion that occurred at the moment of impact. In the current study we examined the possibility that variation in the termination of the conus medullaris may offer protection from neurological injury in a proportion of these fractures.
Methods: A retrospective study was made of 39 patients (26M:13M, mean age 35.9 years, range 15 – 75 years) presenting with a single level thoracolumbar burst fracture (T12–L2) between 1998 and 2001. A whole spine MRI scan was performed on all patients and the level of the conus noted. Age, sex, injury severity score (ISS), neurological status (ASIA motor score) and the transverse spinal canal area (TSCA) of the vertebral levels either side of the fractured vertebra was measured. A predicted TSCA for the injured level was then calculated from the mean of the TSCA’s of the adjacent levels. The actual TSCA of the injured level was calculated and this enabled a percentage decrease of the TSCA to be worked out from the predicted value. Analysis was made of the presence or absence of neurological injury in relation to canal compromise and involvement of the conus.
Results: Eighteen patients with neurological compromise and 21 with intact neurology (the age and sex distribution in the two groups were similar). The mean ± SD ASIA motor score of the patients studied was 90.4 ± 23. Mean ISS was 20.2 in the neurologically injured and 10.5 in the intact (p=0.0005). Mean TSCA of the canal was 218mm2 in the intact and 150mm2 in the injured groups (p=0.006) and mean %TSCA was 70 and 49 respectively (p=0.007). The conus lay between T12 and L2 in all patients. When the conus lay cranial to the fracture (n=13), 38% were neurologically intact. When the conus lay at the level of the fracture (n=26), 62% were intact (NS). Neurological deficit did not occur in the absence of neurological compression on MRI.
Conclusion: Our study showed that the risk of neurological injury from a thoracolumbar burst fracture was not decreased when the conus lay outside the fracture zone. However, there was a statistically significant difference in percentage of canal compromise when the patients with neurological impairment were compared with those that were neurologically intact.
The abstracts were prepared by Mr Colin E. Bruce. Correspondence should be addressed to Colin E. Bruce, Consultant Orthopaedic Surgeon, Alder Hey Children’s Hospital, Eaton Road, Liverpool, L12 2AP.
References:
1 Does neurological recovery in thoracolumbar and lumbar burst fractures depend on the extent of canal compromise? Mohanty SP, Venkatram N. Spinal Cord. 2002 Jun;40(6):295–9 Google Scholar
2 A dynamic study of thoracolumbar burst fractures. Wilcox RK, Boerger TO, Allen DJ, Barton DC, Limb D, Dickson RA, Hall RM. J Bone Joint Surg Am.2003 Nov;85-A(11):2184–9 Google Scholar
