JOA - 2026-05-19 - Journal Article
Comparative Outcomes of Modular Versus Monoblock Fluted Tapered Stems in Revision Total Hip Arthroplasty: An American Joint Replacement Registry Analysis.
Deckey DG, Kelly M, Zaniletti I, Hegde V, Springer BD, Kagan RP, Bingham JS
Topics
Key Takeaway
Monoblock fluted tapered stems were associated with a 40% lower risk of re-revision for dislocation compared to modular stems (aHR 0.6, P=0.045), with no significant difference in all-cause re-revision (8.5% overall) between designs.
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Summary
This AJRR analysis compared re-revision rates between modular and monoblock fluted tapered stems in rTHA patients aged >65 years from 2012–2021 using adjusted cause-specific Cox proportional hazard models. Overall all-cause re-revision was 8.5%, with index revision for dislocation (aHR 1.5) and periprosthetic fracture (aHR 1.3) independently predicting re-revision. Monoblock stems showed a statistically significant lower risk of re-revision for dislocation (aHR 0.6, P=0.045) but no significant difference in all-cause re-revision, infection, PPFx, or aseptic loosening.
Key Limitation
The 83:17 modular-to-monoblock ratio reflects significant selection bias, as surgeons likely chose monoblock stems for anatomically straightforward cases with better bone stock, confounding the dislocation outcome despite adjusted modeling.
Original Abstract
INTRODUCTION
Modular and monoblock fluted tapered femoral stems have become the workhorse in revision total hip arthroplasty (rTHA). This study compared the associated risk of all-cause revision, infection, dislocation, periprosthetic fracture (PPFx), or aseptic loosening between modular and monoblock fluted tapered stem designs.
METHODS
An analysis of rTHA in patients aged > 65 years from 2012 through 2021 in the American Joint Replacement Registry (AJRR) was performed. A total of 9,121 patients who had fluted tapered stems were identified: 7,565 (82.9%) modular and 1,556 (17.1%) monoblock designs. Outcomes including all-cause re-revision, re-revision for infection, dislocation, PPFx, and aseptic loosening were captured through December 2023, for a minimum 2-year follow-up. Adjusted cause-specific Cox proportional hazard models (aHRs) were used to assess the association of stem design with outcomes.
RESULTS
The overall all-cause re-revision rate was 8.5%. Index revision for dislocation (aHR 1.5, P = 0.03) and PPFx (aHR 1.3, P = 0.01) were associated with increased re-revision risk. There was no risk of infection (aHR 0.9, 95% confidence interval (CI): 0.6 to 1.4, P = 0.57), PPFx (aHR 0.7, 95% CI: 0.5 to 1.1, P = 0.12), or aseptic loosening (aHR 0.9, 95% CI: 0.6 to 1.6, P = 0.83) that was found to be associated with type of fluted tapered stem. Compared to those who had modular stems, those who had monoblock stems were not associated with an increased risk of all-cause re-revision (aHR 0.7, 95% CI: 0.6 to 1.0, P = 0.052). However, compared to those who had modular stems, those who had monoblock stems were associated with a lower associated risk of re-revision for dislocation (aHR 0.6, 95% CI: 0.4 to 1.0, P = 0.045).
CONCLUSIONS
There was no significant difference in the risk of all-cause re-revision between modular and monoblock fluted tapered femoral stems in rTHA. Notably, monoblock stems were associated with a lower risk of subsequent re-revision for dislocation.