Patient-Related Factors Associated with Mechanical Failure After Hemilaminectomy with Posterolateral Fusion: An Exploratory Retrospective Cohort Study

Background: Implant-related mechanical failure remains a clinically relevant concern following posterior decompression and fusion in elderly patients with lumbar spinal stenosis (LSS). The relative contribution of host-related versus construct-related factors to failure risk requires further clarification. Methods: This retrospective single-center cohort study included 118 patients aged ≥65 years who underwent single-level hemilaminectomy with posterolateral fusion (PLF) for isolated L4–5 central LSS, with a minimum follow-up of 48 months (mean 51.0 ± 2.0 months). All procedures were performed using a standardized posterior technique with uniform 6.5-mm titanium rods and 6.5-mm pedicle screws. Mechanical failure was defined as revision surgery due to radiographically and clinically confirmed hardware-related complications in the absence of infection. Exploratory univariable analyses were conducted to evaluate associations between baseline variables and mechanical failure. Clinical outcomes were assessed using validated patient-reported outcome measures. The Oswestry Disability Index (ODI), Roland Morris Disability Questionnaire (RMDQ), and Visual Analog Scale (VAS) for pain were recorded. Results: Overall revision rate was 13.6% (16/118), including 14 cases (11.9%) of implant-related mechanical failure and 2 cases (1.7%) of infection-related revision. Higher age (p = 0.005), higher body mass index (BMI) (p = 0.005), lower bone mineral density (BMD) (p < 0.001), active smoking (p < 0.001), and diabetes mellitus (DM) (p = 0.023) were significantly associated with mechanical failure. Functional outcomes (ODI, RMDQ, VAS) improved significantly at final follow-up (all p < 0.001). Conclusions: Mechanical failure following hemilaminectomy with PLF appears to be predominantly influenced by host-related factors rather than construct characteristics when a standardized surgical technique is applied. Bone quality and modifiable systemic risk factors may play a critical role in long-term construct durability.