Introduction: Pedicle screw instrumentation as a part of scoliosis surgery has been shown to provide a better correction in lumbar deformities. The purpose of this retrospective study was to verify if segmental screw fixation has the same efficacy in correcting hypokyphotic thoracic deformities.

Methods and results: We considered 40 cases with AIS treated posteriorly by segmental fixation (CDI, Colorado or similar instrumentations) from 1987 to 1998. All patients presented with a predominant hypokyphotic thoracic curve and were divided into two groups (20 cases each) according to the fixation method selected: multiple, hook fixation (MHF) or segmental pedicle screw fixation (SPSF). In the PSF group, the pedicle screws were inserted at every other or every third vertebra in lumbar and thoracic areas, and correction was achieved by translation technique and derotation manoeuvre without distraction and compression on the concavity and convexity of the curve, respectively. At a follow-up longer than two years and in all of the cases, the average frontal correction in the PSF group decreased from 61.3° to 27.6°, and in the MHF group from 57.5° to 28°; the average hypokyphosis value improved from 12.9° to 25.6° in the PSF group, and from 15.3° to 17° in the MHF group. There were no major, visceral or neurological complications related to hook or pedicle screw placement.

Conclusion: According to the present results, segmental pedicle screws are more effective than multiple hooks in restoring thoracic kyphosis in AIS: pedicle screw fixation may play a role in reducing the need for the two-stage surgery.