Influence of Stem Dimensions on Radiological and Clinical Results in Revision Knee Arthroplasty With Metaphyseal Sleeves: A Retrospective Analysis.

Abstract

Metaphyseal sleeves (MSs) achieve press-fit fixation in zone 2 during revision total knee arthroplasty (rTKA). The Canal Filling Ratio (CFR) estimates the engagement offered by a stem. The objectives in this study were to evaluate clinical and radiological outcomes in patients undergoing rTKA using stemmed MSs and to determine if there is a correlation between these variables and stem length and CFR. This retrospective study included 67 patients who underwent rTKA using uncemented stemmed MSs, with a minimum follow-up of 2 years. The radiological outcomes included the stem length and CFR, the incidence of radiolucent lines for each sleeve, measured by the modified Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System for MSs, and limb alignment, measured by hip-knee-ankle angle. Functional outcomes comprised the Knee Society Score, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Numerical Rating Scale for pain. The mean CFR for femoral and tibial components was 64 ± 12 and 68.4 ± 12.1%, respectively. Radiolucencies were observed in 23.4% of femoral and 44.8% of tibial implants, with no cases of prosthetic loosening. The mean hip-knee-ankle angle was 178 ± 2.93º, with 94% of the patients within 3º varus-valgus. Patients who were correctly aligned had a significantly higher tibial CFR (69.2 versus 56.5%, respectively, P = 0.049) and stem length (97.7 versus 67.5 mm, respectively, P = 0.029). No correlation was found between CFR or stem length and modified Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System scores. Functional outcomes improved significantly in all patients. Tibial CFR showed a weak, but significant correlation (r = 0.270) with Knee Society Score function (P = 0.031). Press-fit stems may not be necessary to achieve adequate implant stability when used in combination with an MS, but tibial stem dimensions seem to influence limb alignment and could slightly improve functional outcomes.