Radiolucent cage for cervical vertebral reconstruction: a prospective study of 17 cases with 2-year minimum follow-up

Abstract

In cervical spondylotic myelopathy, extended anterior spinal cord decompression necessitates subsequent stable vertebral reconstruction. Reconstruction with an iliac crest graft and screw-plate fixation gives satisfactory clinical and radiological results, but they are often compromised by morbidity involving the bone harvest. The purpose of this study was to evaluate the contribution to cervical reconstruction of a biocompatible, radiolucent cage combined with screw-plate fixation, making use of bone harvested in situ. This prospective study was performed between July 2000 and March 2001 in eight women and nine men (mean age, 55 years) operated for cervical spondylotic myelopathy. Situated between levels C3 and C6, the cage was inserted after one corporectomy in ten patients, two corporectomies in five patients, and three corporectomies in two patients. The cage consisted of a polyester mesh impregnated with poly-L-lactic acid (PLLA) conferring temporary rigidity to the cage during bony fusion. Clinical and radiological follow-up (plain films, computed tomographic reconstruction in three cases) was performed at 2 months, 6 months, 12 months, 24 months and 36 months, postoperatively, with a mean follow-up of 30 months. Functional results were evaluated according to the Japanese Orthopaedic Association's scoring system. An independent surgeon assessed the radiological evidence of anterior cervical fusion using the grades proposed by Bridwell [6]. Every patient experienced neurological recovery. At last follow-up, radiological findings were consistent with grade I (complete fusion) in five cases, grade II (probable fusion) in ten cases, grade III (radiolucent halo in favor of non fusion) in one case, and grade IV (graft lysis) in one case with persistent neck pain. In three cases there was screw breakage (two grade II, one grade IV). None of these cases required surgical revision at latest follow-up. In extensive spinal cord decompression through an anterior approach, cervical reconstruction using the present type of cage can achieve clinical results comparable to conventional techniques. The rigidity of the cage meets biomechanical imperatives. Its radiolucency permits one to monitor the course of consolidation, contrary to metal cages. The cases of probable non-fusion and screw breakage were not accompanied by signs of instability on the flexion extension films. This cage meets the biologic and biomechanical imperatives of cervical reconstruction. It obviates complications involving bone harvest.