Comparison of Three Sacral Screw Internal Fixation Techniques in the Treatment of L4-S1 Lumbar Degenerative Disease with Osteoporosis: A Retrospective Observational Study

Background: Patients with L4?S1 lumbar degenerative disease (LDD) with osteoporosis are prone to sacral-screw loosening during spinal internal fixation. We aimed to compare the clinical efficacy and imaging results of sacral bicortical, tricortical, and polymethylmethacrylate (PMMA)-augmented pedicle-screw fixation in the treatment of L4? S1 LDD with osteoporosis. Methods: This is a retrospective study, 36 patients were enrolled and divided into three groups according to the S1-screw fixation method: PMMA-augmented pedicle-screw fixation (Group A, n=12), bicortical fixation (Group B, n=12), and tricortical fixation (Group C, n=12). The visual analog scale (VAS) and Oswestry disability index (ODI) were recorded preoperatively and at the last follow-up, and the postoperative complications, screw-loosening rate, and fusion rate were compared between the three groups. Results: Upon the last follow-up, the VAS and ODI scores of the three groups were significantly improved compared with those recorded preoperatively. The VAS and ODI scores of Group A were significantly smaller than those of Groups B and C (P<0.005), with no significant difference between Groups B and C. Furthermore, we found that osteoporosis and change of lumbar lordosis (LL) value were independent risk factors for sacral-screw loosening in patients with L4?S1 LDD with osteoporosis. Conclusions: When patients with L4?S1 LDD with osteoporosis undergo lumbosacral fusion and fixation, the use of S1 pedicle screws with PMMA augmentation has better stability and less screw loosening.