Do pedicle screws in concave apex of scoliosis offer any advantages?

Abstract

Study Design: Retrospective analysis of prospectively collected data. Purpose: To assess the relative advantages of implant constructs with and without pedicle screws in the concave apex for correcting scoliosis. Overview of Literature: Concave apical pedicles in scoliosis can be narrow and dysplastic. Neural structures also migrate toward concavity, leaving little room for error while inserting pedicle screws into the concave apex. Methods: Patients (n=35) undergoing scoliosis surgery from September 2004 to September 2009 with minimum 5-year follow-up period were included. Exclusion criteria were pseudarthrosis, implant failure, infection, anterior release surgery, corrective osteotomies, incomplete data, constructs not involving anchors at the apex of the curve, and kyphoscoliosis. Curves were classified into two groups as follows: group A, with screws alone anchoring the convex apex and the correction performed from the convex side and group B, with screws anchoring the concave apex with or without convex apex purchase and the correction performed from the concave side. Results: Twenty-two of 35 patients were selected. In these patients, 29 individual curves were selected and classified into groups A (n=15) and B (n=14). Both groups were comparable in terms of age, sex, and etiology (idiopathic and nonidiopathic). However, group A had larger (68.53°±26.29°) and more rigid (29.04%±18.22% flexibility) curves than group B (50.14°±16.89° with 49.87%±25.01% flexibility) (two-tailed p < 0.05). Despite this, the immediate postoperative correction was comparable between the two groups (A, 57.98%±16.28%; B, 62.76%±13.13%; two-tailed p =0.39). Interestingly, group A showed significantly better results in terms of the gain of instrumented correction over and above preoperative flexibility (A, 28.94%±8.51%; B, 12.89%±23.06%; two-tailed p =0.03). There was no statistically significant difference in the correction percentage of sagittal profile between the two groups and in the loss of correction at follow-up or Scoliosis Research Society-22 scores. Conclusions: Present study could not demonstrate any advantages associated with use of apical concave pedicle screws.