Effect of Glenoid Component Compression Timing on the Cement–Bone Interface of Pegged All-Polyethylene Glenoid Components: A Micro–Computed Tomography Study

Glenoid loosening remains a principal failure mode after anatomic total shoulder arthroplasty (aTSA). Cement pressurization improves fixation; however, the optimal timing of axial compression during polymethylmethacrylate (PMMA) curing remains unknown. We hypothesized that brief-early compression followed by undisturbed curing would yield a more favorable cement–bone morphology than continuous or intermittent compression. 15 ovine scapulae received three-pegged all-polyethylene glenoid components (Next Health Products, Ankara, Turkey) using standard-viscosity PMMA. Specimens were randomized to continuous compression (70 N for 10 min), brief-early compression (70 N for 2 min, then none), or intermittent compression (70 N; 2 min on, 1 min off, 3 min on, 1 min off, 3 min on) groups (n=5/group). An axial load was applied using a universal testing machine and custom seating jig; no off-axis or cyclic loading was introduced. High-resolution micro-computed tomography (micro-CT) with blinded analysis quantified cement–bone interdigitation volume, cement porosity, cement–bone contact area, penetration depth, and peri-implant trabecular bone mineral density (BMD). Group comparisons used one-way or Welch ANOVA, Holm–Bonferroni correction across the four prespecified interface outcomes, and Tukey or Games–Howell tests for pairwise comparisons. BMD was analyzed exploratorily. Omnibus tests showed significant group effects for interdigitation volume (P = .002), cement porosity (P < .001), and cement–bone contact area (P = .017), whereas penetration depth did not differ between the groups (P = .475) despite these differences. Brief-early and continuous compression produced greater interdigitation than intermittent compression (brief-early vs. intermittent mean difference [MD] +273 mm 3 , 95% CI 119–428; P = .001; continuous vs. intermittent MD +162 mm 3 , 95% CI 7–317; P = .040), whereas brief-early versus continuous compression was not significant (P = .176). For cement porosity, intermittent compression yielded more porous mantles than brief-early (MD +1.5%, 95% CI 0.9–2.2; P < .001) and continuous (MD +0.9%, 95% CI 0.3–1.6; P = .006); continuous versus brief-early was not significant (P = .091). Cement–bone contact area was greatest with brief-early and lowest with intermittent; only the brief-early versus intermittent comparison reached significance (MD +20 mm 2 , 95% CI 8–32; P = .004). In this ovine glenoid model, brief-early compression followed by undisturbed curing produced a more favorable cement–bone micro-architecture than an intermittent pattern and a numerically more favorable profile than continuous compression without altering penetration depth; however, the brief-early versus continuous comparison did not reach statistical significance. These micro-CT findings support brief-early compression for pegged all-polyethylene glenoids, but remain hypothesis-generating pending mechanical validation.