Combination of sacral-alar-iliac screw and cortical bone trajectory screw techniques for lumbosacral fixation: technical note

OBJECTIVELumbosacral fixation plays an important role in the management of devastating spinal pathologies, including osteoporosis, fracture, infection, tumor resection, and spinal deformities, which require long-segment fusion constructs to the sacrum. The sacral-alar-iliac (SAI) screw technique has been developed as a promising solution to facilitate both minimal invasiveness and strong fixation. The rationale for SAI screw insertion is a medialized entry point away from the ilium and in line with cranial screws. The divergent screw path of the cortical bone trajectory (CBT) provides a higher amount of cortical bone purchase and strong screw fixation and has the potential to harmoniously align with SAI screws due to its medial starting point. However, there has been no report on the combination of these two techniques. The objective of this study was to assess the feasibility of this combination technique.METHODSThe subjects consisted of 17 consecutive patients with a mean age of 74.2 ± 4.7 years who underwent posterior lumbosacral fixation for degenerative spinal pathologies using the combination of SAI and CBT fixation techniques. There were 8 patients with degenerative scoliosis, 7 with degenerative kyphosis, 1 with an osteoporotic vertebral fracture at L5, and 1 with vertebral metastasis at L5. Fusion zones included T10–sacrum in 13 patients, L2–sacrum in 2, and L4–sacrum in 2.RESULTSNo patients required complicated rod bending or the use of a connector for rod assembly in the lumbosacral region. Postoperative CT performed within a week after surgery showed that all lumbosacral screws were in correct positions and there was no incidence of neurovascular injuries. The lumbosacral bone fusion was confirmed in 81.8% of patients at 1-year follow-up based on fine-cut CT scanning. No patient showed a significant loss of spinal alignment or rod fracture in the lumbosacral transitional region.CONCLUSIONSThis is the first paper on the feasibility of a combination technique using SAI and CBT screws. This technique could be a valid option for lumbosacral fixation due to the ease of rod placement with potential reductions in operative time and blood loss.

The Prevalence and Risk Factors for S2 Alar-Iliac Screw Loosening with a Minimum 2-Year Follow-up

Study Design: A retrospective cohort study.Purpose: The purpose of this study was to investigate the prevalence and risk factors for S2 alar-iliac (SAI) screw loosening following lumbosacral fixation, with a minimum 2-year follow-up.Overview of Literature: Although SAI screws allow surgeons to perform lumbosacral fixation with a low profile and enhanced biomechanical strength, screw loosening following surgery can occur in some cases. However, few studies have investigated the prevalence and risk factors for SAI screw loosening.Methods: This retrospective study included 35 patients (mean age, 72.8±8.0 years; male, 10; female, 25) who underwent lumbosacral fixation using SAI screws with at least 2 years of follow-up. SAI screw loosening and L5–S bony fusion were assessed using computed tomography. The period for which the screws appeared loose and the risk factors for SAI screw loosening were investigated 2 years after surgery.Results: A total of 70 SAI screws and 70 S1 pedicle screws were inserted. Loosening was observed 0.5, 1, and 2 years after surgery in 17 (24.3%), 35 (50.0%), and 35 (50.0%) SAI screws, respectively. Bony fusion rate at L5–S was significantly lower in patients with SAI screw loosening than in those without screw loosening (65.0% vs. 93.3%, p =0.048). The score for SAI screw contact with the iliac cortical bone and the bony fusion rate at L5–S were significantly lower in the loosening group than in the non-loosening group (1.8±0.5 vs. 2.2±0.3, p <0.001, respectively). Postoperative pelvic incidence–lumbar lordosis was significantly higher in the loosening group than in the non-loosening group (7.9°±15.4° vs. 0.5°±8.7°, p =0.02, respectively).Conclusions: SAI screw loosening is closely correlated with pseudoarthrosis at L5–S. Appropriate screw insertion and optimal lumbar lordosis restoration are important to prevent postoperative complications related to SAI screws.

TOMOGRAPHIC STUDY OF THE S2-ALAR-ILIAC SCREW TECHNIQUE IN BRAZILIAN WOMEN

ABSTRACT Objective: Lumbosacral fixation presents problems in its arthrodesis, mainly due to pseudoarthrosis. Iliac screws minimize this problem, however, they show problems in the operative wound. The S2-Alar-iliac (S2AI) screw presents a lower rate of these complications. The anatomical differences between the populations and the sexes analyzed in the literature justify the study of the S2AI screw technique in Brazilian women. Methods: A total of 14 adult female CT scans were analyzed by 4 evaluators. Results: The mean bone length was 131.8 mm, the largest bone diameter was 22.6 mm, and the smallest bone diameter was 22.6 mm. Conclusions: The data presented are compatible with the literature and may assist spine surgeons in choosing the best implant and surgical technique. Level of Evidence I; Diagnostic Studies — Investigating a Diagnostic Test (anatomical investigation).