Outcomes of collared uncemented stems in total hip arthroplasty for primary osteoarthritis: A Swiss National joint registry analysis.

BACKGROUND

Uncemented stems have become the preferred fixation method in total hip arthroplasty (THA) for patients under 65 due to high implant survival rates. Collared uncemented femoral stems have risen in popularity because their design offers increased vertical and rotational stability. This provides an additional support and pressurizing effect at femoral calcar until complete biological fixation occurs. Evidence remains conflicting, with no clear consensus on whether collared stems reduce revision rates or improve clinical outcomes compared to collarless stems in primary THA. Therefore we performed a large registry based investigation aiming to: (1) compare the cumulative all-cause revision rates of Corail™ collared uncemented, collarless uncemented, and collarless cemented stems in THA for primary osteoarthritis, (2) examine the cumulative rates of postoperative PPFs (pPPFs), aseptic femoral stem loosening, instability, and infection.

HYPOTHESIS: The use of collared uncemented stems is associated with reduced cumulative all-cause revision rate compared to collarless uncemented and cemented stems in THA for primary OA.

METHODS

All THA procedures recorded by the Swiss National Joint Registry from September 2012 to December 2023 for a diagnosis of primary osteoarthritis using Corail™ collarless uncemented (Group1, n = 14,413), Corail™ collared uncemented (Group 2, n = 17,220), and Corail™ cemented stems (Group 3, n = 21,032), were included. Propensity scores were used to match the three groups. Cumulative percent revision was calculated for all-cause revisions, revision for postoperative PPFs (pPPFs), aseptic femoral stem loosening, infection, and instability. Cumulative hazard rates (HR) with 95% confidence intervals (CI) were calculated from inverse probability-weighting to compare revision rate among the three groups regarding all-cause revisions. A Poisson regression model subanalysis was performed to assess the risk factors associated with the occurrence of intraoperative PPFs (iPPFs).

RESULTS

Collared uncemented stems were associated with the lowest rate of all-cause revisions (HR: 3.5, 95%CI: 2.9-4.1 (p < .001)) compared to collarless and cemented stems (HR: 5.5,95%CI: 4.8-6.2 and HR: 6.0 95%CI: 5.0-6.9), respectively). Moreover, collared stems had the lowest revision rate for pPPFs (0.14%; p < .001) compared to collarless and cemented stems (1.00%, and 0.43%, respectively). Furthermore, collared stems had a significantly lower revision rate for aseptic femoral loosening (0.47%; p < .001) compared to cemented stems (1.02%), but no statistical difference was found with collarless stems (0.73%; p = 0.022). Finally, collared stems also demonstrated a lower revision rate for infection, and instability, although these differences were not statistically significant compared to the other two groups. The subanalysis revealed that significant incidence rate ratio (RR) associated with occurrence of iPPFs were collared stems (RR = 1.5, 95%CI: 1.1-2.0 [p =  0.007]) and posterior approach (RR = 1.6, 95% CI: 1.1-2.2 [p = 0.005]).

CONCLUSION

Although collared uncemented stems were associated with an increased risk of iPFFs, they demonstrated a diminished rate of all-cause revision for uncemented THA. This reduction in risk may be attributed to protection against pPPFs and a lower risk of revision for aseptic femoral stem loosening.

LEVEL OF EVIDENCE: III; Propensity score matching analysis.