Clinical and Radiographic Outcomes of Two-Stage Allograft-Augmented Fixation Versus Conventional Posterior Segmental...

Background: Successful spinal stabilization depends not only on early mechanical fixation but also on durable biological integration at the bone-implant interface. This study aimed to compare a two-stage allograft-augmented fixation strategy, intended to promote biological fixation, with conventional posterior segmental stabilization (PSS) in the treatment of screw loosening following multilevel spinal surgery for degenerative spine pathology. Methods: This retrospective comparative study included 40 patients who underwent multilevel spinal stabilization between January 2022 and February 2025, with follow-up completed by November 2025. Patients were divided into a conventional PSS group (n = 28) and a two-stage allograft-augmented fixation group (OI-focused strategy, n = 12). Demographic characteristics, comorbidity burden, length of hospital stay, complications, Visual Analog Scale (VAS), the Oswestry Disability Index (ODI), and sagittal radiographic parameters-including lumbar lordosis (LL), sagittal vertical axis (SVA), sacral slope (SS), and pelvic incidence (PI)-were evaluated preoperatively and at 1, 6, and 9 months postoperatively. Results: The groups were similar in terms of age, sex, body mass index, smoking status, and number of operated levels. Despite the significantly higher Charlson Comorbidity Index and Elixhauser Comorbidity Index scores in the OI-focused group, hospital stay was significantly shorter. VAS and ODI scores were comparable preoperatively and at 1 month; however, significantly better pain and functional outcomes were observed in the OI-focused group at 6 and 9 months. Radiologically, SVA was significantly lower in the OI-focused group at 6 and 9 months. Late differences were also observed in LL and SS, while PI remained similar between groups. Fusion-related findings were interpreted cautiously because fusion was assessed using plain radiographs and osseointegration was not directly measured. Conclusions: The two-stage allograft-augmented fixation strategy was associated with better mid-term pain control, improved functional recovery, and better preservation of selected sagittal alignment parameters compared with conventional PSS. However, these findings should be interpreted cautiously due to the retrospective design, limited sample size, imbalanced groups, absence of direct osseointegration measurement, and lack of CT-based fusion analysis.