Radiographic Factors Associated With Tibial Metaphyseal Sleeve Survivorship in Revision Total Knee Arthroplasty: A Matched Cohort Study.

Abstract

Metaphyseal sleeves are increasingly utilized in revision total knee arthroplasty (rTKA) to obtain zonal fixation in the metaphysis and improve implant survivorship. However, radiographic factors associated with long-term sleeve survival remain poorly defined. We previously characterized a cohort of aseptically failed tibial sleeves. This study compared those rare failures to long-term surviving sleeves, assessing whether lack of medial baseplate support and undersized sleeves and stems are more common in aseptic failures. A retrospective review was performed of patients undergoing rTKA with tibial metaphyseal sleeves at a single academic institution (2011 to 2025). There were 18 aseptically failed sleeves identified and compared to a cohort of surviving sleeves with a minimum 3-year follow-up. Stem canal fill ratios (CFRs) were measured on antero-posterior (AP) and lateral radiographs using the Parsley method. A novel area fill ratio was calculated using ImageJ software, comparing implant area to tibial canal area over the sleeve and stem length. The medial baseplate support was classified as unsupported with greater than two mm of gapping or greater than two mm of cement mantle in lieu of augments. Optimal matching by age, sex, and BMI (body mass index) created a matched subgroup for comparison. There were 53 surviving-sleeve patients identified (mean follow-up 6.7 years (range, 3.0 to 13.6 years)). All stem and sleeve fill ratios-Parsley CFRs, distal 4-cm stem area fill ratios, and metaphyseal sleeve area fill ratios-were significantly greater in both the unmatched (n = 53) and matched (n = 31) surviving cohorts versus the 18 failing sleeves (all P < 0.05). The medial baseplate support was present in 77.4% of unmatched and 74.2% of matched survivors versus 44.4% of failures (P = 0.017 and P = 0.064, respectively). Greater metaphyseal sleeve fill, greater diaphyseal stem fill, and the presence of medial baseplate support were each associated with long-term sleeve survivorship following rTKA. These findings support maximizing zonal fixation in rTKA with the use of a sleeve.