Operative stabilization of the posttraumatic thoracic and lumbar spine: a comparative analysis of the Harrington distraction rod and the modified Weiss spring.

To assess the efficacy of operative stabilization techniques, a retrospective study of Harrington distraction rod (HDR) and modified Weiss spring instrumentation was performed in 90 patients. An operation was performed for one or both of two indications: persistent spine instability or the presence of a neurological deficit in patients with incomplete neurological injuries and myelographic evidence of spinal cord or cauda equina compression. The lateral extracavitary operative approach to the spine for decompression and anterior interbody fusion was performed with an accompanying HDR (47 patients) or modified Weiss spring placement (43 patients). Eight HDRs failed, resulting in gross instability (17 per cent) that either resulted in further neurological injury (1 patient), further surgery (2 patients), or increased morbidity secondary to prolonged bed rest (5 patients). One Weiss spring failed, requiring further surgery (2.3 per cent). Nonsurgical complications were similar in both groups and appeared to be unrelated to the type of instrumentation utilized. The modified Weiss spring instrumentation technique, which offers a dynamic compression fixation of the spine, was clearly superior to the HDR technique, which offers a rigid distraction fixation. The biomechanics of distraction versus compression and rigid versus nonrigid spine stabilization are discussed.