ABSTRACT
STUDY DESIGN. This is a retrospective study. OBJECTIVES. To verify the advantage of segmental pedicle screw fixation in restoration of thoracic kyphosis in hypokyphotic patients. SUMMARY OF BACKGROUND DATA. Restoration of thoracic kyphosis is essential for a satisfactory three dimensional correction in thoracic AIS. However, with significant preoperative hypokyphosis, the result of multiple hook fixation was often unsatisfactory. METHODS. Fifty-one patients with thoracic AIS treated by posterior instrumentation and followed up for more than 2 years were divided into 3 groups each comprising 17 patients. Hypokyphosis- Hook(HH) group comprised patients with thoracic kyphosis less than 15degrees treated by multiple hooks. Hypokyphosis-Screw(HS) group comprised hypokyphotic patients treated by segmental pedicle screws. Normal kyphosis-Screw(NS) group comprised patients with kyphosis greater than 15degrees treated by segmental pedicle screws. Preoperative thoracic kyphosis was 4.1+/-8.6degrees, 8.1+/-5.6degrees and 27.3+/-9.8degrees in the HH, HS and NS group respectively. There was no significant difference between the HH and HS groups(p=0.39). Three groups were compared for restoration of thoracic kyphosis. Results. At the final follow up, the thoracic kyphosis was 14.5+/-10.2degrees, 27.3+/-11.3degrees and 28.3+/-3.7degrees in the HH, HS group and NS group showing correction of 10.0+/-10.0degrees, 19.2+/-14.0degrees and 0.4+/-12.3degreesrespectively. There was a significant difference between HH and HS group(p=0.0008). However there were no difference between tile HS and the NS group(p=0.8). CONCLUSIONS. Segmental pedicle screw fixation was more effective than multiple hooks in restoring the thoracic kyphosis in AIS patients with hypokyphosis. The restored kyphosis was similar to that obtained in patients without hypokyphosis.