Effect of Stem Size and Fixation Method on Mechanical Failure After Revision Total Knee Arthroplasty

Although the need for stemmed components is well accepted to improve mechanical survival in revision total knee arthroplasty (TKA), the ideal fixation method and stem design remain controversial.

We performed a retrospective review of 223 patients who underwent revision TKA in whom stemmed components had not been used previously and with a mean follow-up of 61.6 months, including 108 components with fully cemented stems and 316 components with "hybrid" press-fit stems.

Based on a time to event model, risk for mechanical failure was equivalent for both cemented and hybrid stems (relative risk, 0.991; P = .98). Young age was the single greatest risk factor for mechanical failure (P = .006). Although there was a trend toward increased failure with cemented stems in patients aged <65 years, there was no significant difference in risk after accounting for covariates (relative risk, 1.4; P = .50). Intramedullary canal fill, not stem length or diameter, was the strongest predictor of failure with hybrid stems, and risk was reduced by 41.2% for each additional 10% canal fill.

In conclusion, both cemented and hybrid modular stems are viable options in revision TKA. Surgeons should attempt to maximize canal filling of hybrid stems to obtain a solid press-fit. In addition, further studies are needed to evaluate the long-term survival of cemented stem fixation in young patients.