Impact of Concurrent Lower Limb Arthroplasty on Clinical and Radiographic Outcomes Following Posterior Spinal Fusion for Adult Spinal Deformity: A Single-Center Feasibility Analysis

Study Design: Retrospective single-center cohort study; exploratory feasibility analysis. Objective: To describe the feasibility and 12-month clinical and radiographic outcomes of posterior spinal fusion (PSF) for adult spinal deformity (ASD) with versus without lower limb arthroplasty performed during the same hospital admission, as a hypothesis-generating basis for a subsequent prospective study. Background: Hip-spine and knee-spine syndromes describe the biomechanical interdependence of the lower extremities and the spine. Sequential surgical management is well described, but outcomes when arthroplasty and spinal fusion are performed during a single hospitalization remain poorly characterized. Materials and Methods: We retrospectively reviewed 45 consecutive adult patients who underwent T12–pelvis PSF for ASD at a single academic center between January 2019 and December 2023. All patients received a standardized T12–pelvis construct with selective laminectomies at symptomatic levels. Patients who underwent concurrent lower limb arthroplasty under the same anesthetic event (concurrent group, n = 18; 16 TKA, 2 THA) were compared descriptively with those who underwent PSF alone (spine-only group, n = 27). Clinical outcomes (Oswestry Disability Index, VAS Back and Leg pain) and radiographic sagittal parameters (PI, LL, PT, SS, TK, TPA, SVA) were assessed at baseline and 12 months. Paired within-patient change was analyzed by the Wilcoxon signed-rank; between-group comparisons used Mann–Whitney U for continuous and Fisher exact for categorical variables. A sensitivity ordinary least-squares regression adjusting for age was prespecified. Exact denominators are reported at every time point. Results: The concurrent group was significantly older (74.1 ± 6.1 vs . 65.6 ± 10.2 yr, P = 0.003) with similar BMI and comorbidity profile. Anesthesia time (291.5 ± 84.8 vs . 306.6 ± 99.4 min, P = 0.57) and length of stay (5.8 ± 2.1 vs . 6.2 ± 3.7 d, P = 0.90) did not differ. Among patients with available 12-month radiographs (24/45, 53%), all were assessed as fused. Within-patient paired change in ODI was −18.0 (n = 5) in concurrent vs . −7.7 (n = 14) in spine-only (between-group P = 0.150). ΔVAS Leg reached nominal significance in unadjusted paired analysis (−4.4 vs . −1.5, P = 0.037) but was not significant after adjustment for age (β = −2.5, 95% CI: −6.0 to +1.1, P = 0.17). Structured complications were comparable between groups: proximal junctional failure occurred in 1/18 (6%) concurrent and 2/26 (8%) spine-only patients ( P = 1.00); screw loosening in 3/18 (17%) and 4/21 (19%) respectively ( P = 1.00). No radiographic parameter differed significantly between groups after adjustment. Conclusions: Concurrent lower limb arthroplasty with PSF under a single anesthetic event was feasible in this small ASD cohort, with comparable anesthesia time, length of stay, fusion rates among assessed patients, and structured complication rates. No statistically significant advantage was detected for clinical or radiographic outcomes after adjustment for age. These exploratory findings are hypothesis-generating and require confirmation in prospective multi-institutional studies before any comparative effectiveness inference can be drawn. Level of Evidence: Level III, therapeutic.