Abstract
Introduction
Study design: prospective.
Objectives
To assess lumbar curve behavior in Lenke IA and B curves treated by selective thoracic posterior fusion. Test hypotheses were that spontaneous lumbar curve correction (SLCC) would be better with smaller initial deformities, in more flexible curves, and of greater magnitude with higher metal density.
Summary of Background Data
There are different and often conflicting recommendations regarding selection of lowest instrumented vertebra and best approach which provides the greatest SLCC. All-pedicle-screw constructs and increasing metal density are recent trends. However, few reported the fate of the residual unfused lumbar curve.
Material and Methods
Thirty-three patients with AIS Lenke 1A/B (single surgeon) were included with a minimum follow-up of 2 years. Mean age was 14.2 years (9–19 years). All had all-pedicle-screw constructs with mean metal density of 58% (36–75%). The mean fused level was 10.3.
Results
The mean thoracic Cobb angle for preoperative, immediate postoperative, at 1-year, and final follow-ups were 60.6, 15.5, 15.9, and 17.2 degrees, respectively (mean flexibility 49.4% [10–96%]). Lumbar curve preoperative mean Cobb angle was 29.6 degrees (14–53 degrees) (mean curve flexibility 79% [40–96%]). Cobb angle at immediate postoperative, 1-year, and 2-year follow-ups were 9.2, 8.9, and 9.4 degrees, respectively. The mean lumbar lordosis angle preoperatively and at final follow-up was 57.3 and 55.9 degrees. Maximum SLCC was achieved within 6 weeks and maintained throughout. No lumbar decompensation was noted. There was significant correlation between the percentage correction of the thoracic curve and SLCC percentage (p = 0.027). There was no significant correlation between SLCC and the preoperative thoracic curve magnitude (p = 0.16). Similarly, there was no correlation between metal density and SLCC (p = 0.62). The patients were divided into two groups according to the flexibility (< 40 and ≥ 40%). There was no correlation between the SLCC and curve flexibility.
Conclusion
Our results demonstrate that in Lenke IA and B curves treated with selective pedicle-only posterior fusion, there were no decompensation, lumbar curve was corrected significantly, and SLCC was completed within 6 weeks and maintained. Lumbar lordosis remained normal. The percentage of lumbar curve correction was neither associated with its initial Cobb angle magnitude nor flexibility. Finally, magnitude of preoperative thoracic curve, latter curve percentage correction, and metal density did not affect SLCC.