Segmental cantilever correction of kyphosis and kyphoscoliosis: Technique and early clinical and radiographic outcomes

2009

SUMMARY

This is a retrospective review of prospective data collected on 41 patients with kyphosis and kyphoscoliosis surgically corrected with incremental cantilever forces applied segmentally through spinal implants, followed 35 months (12-81 months). Improved ODI, VAS, medication use were recorded. Complications included 6 nonunions with 2 broken rods, 1 infection, and 2 adjacent fractures in osteoporotic patients. Gradual application of cantilever correction forces through segmental translation is effective at correcting sagittal deformity without increased complications.

INTRODUCTION

Computer modeling has shows translational deformity correction products lower screw-bone interface stress than other techniques, with better deformity correction. This is the largest series describing early clinical and radiographic outcomes for kyphosis and kyphoscoliosis correction utilizing segmental cantilever forces gradually applied.

METHODS

Prospective data was retrospectively reviewed on 41 consecutive patients age 49 years (14-81 years) undergoing surgery for kyphosis (14) or kyphoscoliosis (27) and followed average 35 months (12-81 months). Posterior instrumented sagittal correction was achieved by pulling the spine to contoured rods via pivoting posts attached to segmentally placed pedicle screws. Fusions averaged 11 levels (4-17 levels). Subtraction osteotomies were excluded; extension osteotomies were common. Nine had prior fusions. Anterior release was done in 30/41. Clinical data included Oswestry (ODI), pain scores (VAS), pain medication use, work status, and complications. Radiographic data included sagittal (T5-12, T10-L2, T12-S1, kyphosis), coronal and sagittal balance, scoliosis, pelvic incidence.

RESULTS

Complications: 6 nonunions with 2 broken rods, 1 infection, 2 adjacent fractures, 2 transient foot drops. ODI scores improved from 39% (0-94%) preop to 27% (0-58%) at 1 year. VAS improved from 6.1 (1-10) pre-op to 3.2 (1-8) at 1 year (p<0.05). Pain medication use dropped similarly. Kyphosis corrections: Scheuermanns: pre-op 83° (73-91°) improved to 44° (32-59°), idiopathic kyphoscoliosis: pre-op 47° (10-80°) improved to 31° (0-58°), post-traumatic kyphosis: pre-op 86° (70-103°) improved to 35° (19-51°). For degenerative kyphoscoliosis: pre-op 45° (23-76°) improved to 45° (20-68°) and T12-S1 improved from -28° (0-(-62°)) to -42° (-20-70°), and T10-L2 improved from 21° (4-31°) to 10° (-10-29°).

CONCLUSION

Gradual application of cantilever correction forces through segmental translation is effective at correcting coronal and sagittal deformity without increased complications. This technique reliably leads to clinical and radiographic improvement when used to treat patients with kyphosis and kyphoscoliosis.

SIGNIFICANCE

Incremental application of segmental cantilever forces to correct kyphosis is effective without increasing complications.