Less invasive surgical correction of adult degenerative scoliosis, part I: technique and radiographic results

Abstract

Background: Adult scoliosis is a condition with increasing prevalence and medical and socioeconomic importance. Surgery is fraught with a significant complication rate in an elderly multimorbid patient population.

Objective: To assess technical feasibility and radiographic results of image-guided less invasive correction of adult degenerative scoliosis.

Methods: Thirty individuals (age, 64-88 years) with progressive deformity (coronal Cobb angles > 25 degrees and < 85 degrees), intractable back pain, radiculopathy, or neurogenic claudication were treated by less invasive decompression and fusion (unilateral transforaminal interbody cage instrumentation and bilateral facet fusions) with recombinant human bone morphogenetic protein-2, spanning 3 to 8 segments (average, 6 segments), using biplanar fluoroscopy or intraoperative computed tomography (iCT)-based navigation. Accuracy of screw placement, curve correction, and fusion rate were evaluated during a mean follow-up of 19.6 months.

Results: With 415 screws implanted, misplacement (grade II or greater) was not observed, and no implants required revision. Spinal iCT with automated registration required 17.5 +/- 8.5 minutes (single registration for all segments); monosegmental bilateral screw insertion required 6.8 +/- 3.4 minutes. Mean sagittal (coronal) Cobb angle correction was 44.8 +/- 10.7 degrees (31.7 +/- 13.7 degrees). Mean lumbar lordosis increased from 8.8 +/- 8.9 degrees to -36 +/- 6.9 degrees, and sagittal balance was reduced from 31.6 +/- 15.2 to 8 +/- 8.4 mm. Solid fusion was confirmed in 90% of instrumented segments at 16 months. Average radiation dose to the surgeon was 0.025 mSv for single-level transforaminal lumbar interbody fusion with fluoroscopic guidance vs 0 mSv with iCT navigation.

Conclusion: Instrumented correction of adult deformity was significantly facilitated by iCT navigation, eliminating radiation exposure to the surgeon. Intraoperative biplanar CT scout views including pelvis and shoulders allow comprehensive assessment of multiplanar deformity correction. Fusion rates obtained with less invasive access equal those of conventional open technique.