Interbody rhBMP-2 in long-segment fusions for adult scoliosis: CT scan, radiograph and clinical analysis

2009

SUMMARY

This is the first study of CT scan and clinical results of interbody rhBMP-2 (ALIF or TLIF) combined with posterior instrumented fusion for adult scoliosis. 74 consecutive patients undergoing long-segment arthrodesis (avg 8.8 levels, range 4-17) were followed 42 months (24-72 months). 49 were fused to the sacrum. CT scan at 2 years identified 5 nonunions, all at L5-S1. ODI and VAS showed significant improvements from pre-op. Nonunion patients had worse outcomes. Severe sagittal imbalance was linked to nonunion.

INTRODUCTION

Achieving multi-level arthrodesis in adult scoliosis surgery is challenging. This is the first study of CT scan and clinical results in adult deformity patients treated with interbody rhBMP-2 and posterior instrumented fusions (PSF).

METHODS

A retrospective review of prospectively collected data on 74 consecutive adults with scoliosis age 63 years (38-88 years) who underwent PSF at 8.8 levels (4-17 levels) using local autograft and allograft chips plus additional interbody arthrodesis using rhBMP-2 treated by one surgeon, followed 42 months (24-72 months). Prior surgery: 12 fusion, 6 laminectomy; 7 smoked. ALIF was used in 154 discs (avg 4.4) in 35 patients; structural allograft in 30, cages in 5. TLIF was used in 96 discs (avg 2.3) in 39 patients. Two had both ALIF+TLIF, 49 were fused to S1. BMP ranged 2-12mg/disc placed on absorbable collagen sponges. Oswestry (ODI) and pain scores (VAS) collected pre-op, 1 and 2 years. Radiograph measurements: scoliosis, sagittal T5-12, T10-L2, T12-S1, balance, and pelvic incidence; CT scan at 2 years on 67/74 patients were analyzed.

CONCLUSION

Interbody rhBMP-2 use in adult scoliosis reliably leads to arthrodesis and improved outcomes in doses from 2mg/disc, ALIF or TLIF, with bone or cage support. BMP overgrowth occurred 1/250 discs. Nonunions only occurred at L5-S1 and had worse outcomes.

SIGNIFICANCE

Interbody rhBMP-2 combined with posterior intrumented fusion is effective. The stress across L5-S1 in long fusions, especially in severe sagittal imbalance, continues to challenge arthrodesis, despite improved fusion rates with BMP.