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.

Long Segment Fusion to L5 Vertebra and Sacral Vertebra in Degenerative Lumbar Spine / 대한척추외과학회지

STUDY DESIGN: A retrospective clinical study about problems in distal ends of long segment fusion to L5 and S1. Authors compared the incidence of fixation failure and analized the problematic cases. OBJECTIVES: To verify the causes and associated conditions for high incidence of fixation failure in distal ends of long segment fusion. SUMMARY OF LITERATURE REVIEW: In Degenerative lumbar diseases, degenerative kyphosis, degenerative scoliosis with revision surgery and multiple stenosis require long level fusion which is accompanied by various fixation problems extending to sacrum. Fusion to sacrum provides excellent correction of deformity. However, it results in the loss of movable segment and concentration of the force on lumbosacral region. Moreover it may foresee the problems of fixation or fusion and S-I joint problems. But long fusion to L5 leaving one movable segment below can result in early degenerative change of this segment. MATERIAL AND METHODS: Among 65 patients given long level fusion involving more than 3 segment in National Medical Center from January 1991 to may 2000, 45 patients were selected and were followed for more than 2 years. First group (G1) involving L5 were 14 cases. Second group (G2) involving S1 were 31 cases. We evaluated loosening of implant-hallo around screw, pull out screw, breakage of screw or rod, change of adjacent segment and pseudarthrosis by means of radiologic modality. RESULTS: Follow up radiologic findings showed 28.6% of loosening of implant on L5 in G1. G2 showed 41.9% of hallo around screw in S1. Among cases with more than 4 level fusion, G1 showed 33.3% lower segment screw loosening and G2 showed 57.9%. In G2, group performed more than 3 level fusion showed 16.7% lower segment screw loosening. More than 4 level fusion showed higher loosening rate (57.9%) with the statistical segmental corellation (P=0.023). Lower end screw loosening occured 16% in cases with interbody fusion and 55% in cases without interbody fusion and it showed statistical corellation (P=0.047). Also cases with deformity correction by posterior instrumentation showed higher loosening rate (60%) and showed 18.2% in situfusion cases and it showed statistical corellation (P=0.049). In second case, sacral screw loosening occured more frequently in patients of osteoporosis (54%), sagittal imbalance postoperatively (38%), correction loss (31%). Only 1 case of G1 showed an increased degenerative change between L5-S1. CONCLUSION: In fusion to S1 in degenerative lumbar disease, factors such as long level fusion more than 4 segments by posterior instrumented correction, correction loss, sagittal imbalance and accompanied osteoporosis is related to high incidense sacral implant loosening-hallo around screw, pull out screw, breakage of screw or rod. So if these kind of risk factor exist, it seems that the anteriorposterior interbody fusion in necessary. Postoperative L5-S1 degenerative change did not occur in follow up period in patient with well preserved sagittal balance postoperatively in this follow up periods.