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, 72 patients were enrolled and divided into three groups according to the S1-screw fixation method: PMMA-augmented pedicle-screw fixation (Group A, n = 26), bicortical fixation (Group B, n = 22), and tricortical fixation (Group C, n = 24). 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 < 0.05), with no significant difference between Groups B and C. Moreover, the screw-loosening rate of Group A was significantly lower than that of Groups B and C (P < 0.05), with no significant difference between Groups B and C. No significant difference was noted in postoperative complications, bone-cement leakage rates, and intervertebral fusion rates among the three groups. 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. Furthermore, we recommend this surgery for patients with osteoporosis, and the LL should be increased as much as possible during the operation to restore the matching of lumbar and pelvic parameters.