Introduction: Treatment of complex spinal deformity in adult patients requires an understanding of the effect of regional changes on global balance. While the regional impact of an osteotomy can be planned, the impact on distant segments of the spine remains poorly understood. The objective of this study is to analyze reciprocal regional corrective changes in the unfused segments of the spine away from the site of osteotomies as it relates to the final radiographic outcome.
Methods: This is a consecutive, multicenter retrospect review of 134 consecutive adult patients (24M, 110F, mean age= 54 +/− 12 yo). 29 subjects underwent thoracic resection procedures (“Thoracic group”), and 105 underwent lumbar resection procedures (“Lumbar group”). Resection levels ranges from T2 to L4 (Table). Radiographic analysis included pre and postoperative assessment of Thoracic Kyphosis, Lumbar Lordosis, SVA, Pelvic tilt, Pelvic incidence. Paired independent t‐test analysis (SPSS) was computed to evaluate the changes in radiographic parameters
Results: In “Thoracic group”, preop thoracic Kyphosis of 58° was corrected to 38° (p<0.001) and localized correction measured to 11°. For the unfused lumbar segment (12 patients), spontaneous Lordosis changed from 70° to 62° (p<0.05). Preop SVA improved from 2.4cm to ‐1cm (p=0.006) and pelvic tilt improved from 19deg pre‐op to 13deg (p<0.001) In “Lumbar group”, the average correction at the osteotomy was 23°. Lumbar Lordosis increased from 20° to 49° (p<0.001). For the unfused thoracic segment (34 patients), Kyphosis increased from 22° to 35 post op (p=0.002). Pre op SVA improved from 14cm to 4cm post‐op (p<0.001) and pelvic tilt improved from 33° to 25° (p<0.001).
Conclusion: In an attempt to correct spinal imbalance several parameters play important roles in pre‐operative planning. If reciprocal changes related to regional deformity correction can be anticipated, then better post‐operative alignment can be achieved. Furthermore, limiting resection to the site of maximum deformity may addresses the regional malalignment and result in reciprocal and spontaneous changes in unfused segments leading to improved restoration of overall spinal balance. This may eliminate the need to perform longer fusions of the spine.