The Effect of Sacral Alar Screw on Long-level Fusion Including Lumbosacral Segment

STUDY DESIGN: This is a retrospective study. OBJECTIVES: To evaluated the clinical and radiological effectiveness of sacral alar screws for augmentation of S1 pedicle screws in long-level fusion including L5-S1 segment. SUMMARY OF LITERATURE REVIEW: The fusion rates of lumbosacral junction in long-level fusion are various when S1 pedicle screws are used without augmentation. But, reports of sacral alar screw augmentation are rare. MATERIAL AND METHODS: From 1996 to 2005, 63 patients performed more than two-level fusion including lumbosacral junction were reviewed. 47 patients underwent lumbosacral fusion with S1 pedicle screws only (S1 group), and 16 patients with sacral alar screws augmentation in addition to S1 pedicle screws (S1-2 group). Radiologically, bony union, halo sign, and breakage of implants were evaluated. Clinically, complications associated with screw placement and general complications were evaluated. RESULTS: Bony union was obtained in 56 cases(89%) at postoperative 4.3 months. Nonunion was observed in 7 cases(11%, S1 group:5, S1-2 group:2). Loosening of S1 pedicle screw was observed in 32 cases(89%) of S1 group and in 4 cases(25%) of S1-2 group. It showed statistical significance between two groups. Sacral alar screw loosening occurred in 8 cases(50%) of S1-2 group. Metal breakage was developed in 2 cases of S1 group without nonunion or loosening. Postoperative infection occurred in 7 cases(11%, S1 group:5, S1-2 group:2). CONCLUSIONS: Sacral alar screw augmentation was effective on protecting the loosening of S1 pedicle screw. Additional sacral alar screw can improve the rate of fusion for lumbosacral junction despite no statistical significance.

A Comparison of Clinical Stability of Distal Instrument Fused Down to S1 with and without Sub-S1 Alar Screw in the Long Fusion using Segmental Pedicle Screw for Lumbar Degenerative Deformity

STUDY DESIGN: This is a retrospective study. OBJECTIVES: We wanted to assess the stability of distal instrumentation using the bilateral S1 and sacral alar screws for the treatment of degenerative lumbar deformity. SUMMARY OF LITERATURE REVIEW: Various instrumentation methods have been introduced for increasing the strength of lumbosacral fusion. However, there are not many clinical studies that have evaluated the effectiveness of a sub-S1 alar screw for treating degenerative lumbar deformity surgery. MATERIALS AND METHODS: A total of 39 patients with degenerative lumbar deformity were treated by long fusion and we retrospectively analyzed these patients after a minimum follow-up of 1 year. All the patients underwent an operation with distal instrumentation using either bilateral S1 screws alone (the S1 group) or additional bilateral sub-S1 sacral alar screws (the SA group). There were 19 patients in the S1 group and 20 patients in the SA group. The stability of the distal instrumentation was assessed by breakage or backout of a rod and/or screws based on simple radiography. RESULTS: Instability of the distal instrumentation was detected in 6 cases (32%) in the S1 group and in 1 case (5%) in the SA group. The SA group had a more stability of the distal instrumentation than that of the S1 group with a significant difference (P0.05). CONCLUSIONS: Bilateral sacral alar screws coupled with bilateral S1 screws can provide good distal fixation for stability of the distal instrumentation when performing long fusion for treating degenerative lumbar deformity.