NEUROLOGICAL INJURY IN THORACOLUMBAR BURST FRACTURES: IS CONUS INVOLVEMENT THE KEY?

Abstract

Introduction: The poor correlation between neurological injury and degree of retropulsion in thoracolumbar burst fractures has been identified, but not adequately explained. We have 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 presenting with single level thoracolumbar burst fractures between June 1998 and April 2001. Admission MRI was performed on all patients. Age, sex, ISS, neurological status, mode of treatment and any neurological recovery were recorded. From the MRI scans the levels of the conus and the fracture were noted. Transverse Spine Area(TSA) was measured at the cranial, caudal and injured levels. A predicted TSA and % TSA for the injury level was calculated from the mean of the two other levels. Analysis was of severity of neurological injury in relation to canal compromise and involvement of the conus.

Results: 26 male and 13 female patients of mean age 35.9 (SD 17) years and mean ASIA motor score 90.4 (SD 23) were studied. Neither sex nor age distribution differed between 18 neurologically injured and 21 intact patients. Mean ISS was 20.2 in the neurologically injured and 10.5 in the intact (p=0.0005). Mean TSA of the canal was 218mm2 in the intact and 150mm2 in the injured groups (p=0.006) and mean %TSA was 70 and 49 respectively (p=0.007). The conus lay between T12 and L2 in all. 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.

Conclusions: Neurological injury is not less likely when the conus lie outside the fracture zone. Canal compromise is a highly significant factor in neurological injury.