LIGAMENTOTAXIS WITH AN INTERNAL SPINAL FIXATOR FOR THORACOLUMBAR FRACTURES

We assessed narrowing of the spinal canal in 39 burst fractures and fr acture-dislocations of thoracolumbar vertebrae treated by the AO Inter nal Spinal Fixator, using CT preoperatively and at various stages post operatively. Computer-aided planimetry was used to measure the narrowi ng, and its restoration shortly after instrumentation, or at 15 months . The mean initial reduction of canal area was to 63.7% +/- 18.8% of n ormal; this was restored to a mean of 95.4% +/- 21.2% of normal when m easured either soon after surgery or at 15 months (p < 0.001 for both groups). There was more improvement in cases assessed later. For fract ures from D12 to L3, the mean canal area was restored to 99.4% of norm al; but at L4 or L5 the mean restitution was to only 60.9% (p < 0.05). We found no correlation between preoperative loss of area and amount of restoration, or severity of neurological deficit. Nor was there any correlation between the delay before surgery and the improvement achi eved. The mechanism of fracture reduction appears to be a combination of distraction ligamentotaxis and forced hyperextension.