Distribution of Bone Ongrowth in Metaphyseal Sleeves for Revision Total Knee Arthroplasty: A Retrieval Analysis

Background: The metaphyseal region of the bone has been recognized by its importance to the overall stability of a revision construct. Porous titanium metaphyseal sleeves to enhance biologic fixation can be used to manage bone loss encountered during revision total knee arthroplasty. While clinical results for metaphyseal sleeves are encouraging, there is little information on the extent to which biologic fixation is achievable with metaphyseal sleeves. We examined retrieved metaphyseal sleeves to determine the amount of bone ongrowth. Materials and Methods: We studied 14 tibial and 11 femoral retrieved metaphyseal sleeves from 16 typical arthroplasty patients. Prerevision radiographs were reviewed for the presence of biologic fixation to the sleeves and the stem canal fill ratio. Bone ongrowth was assessed regionally in the anterior, posterior, medial, and lateral areas of the retrieved implants. Results: Bone ongrowth covered on average 14.7 +/- 3.4% of the entire porous surface of the tibial sleeves. The lateral and anterior surfaces had a significantly greater proportion (P < .05) of bone ongrowth compared with the posterior and medial surfaces of the tibial components. Bone ongrowth covered on average 21.3 +/- 2.6% of the entire porous surface of the femoral sleeves. No differences were found in the proportion of bone ongrowth among the posterior, medial, lateral, and anterior surfaces of the femoral. No significant association was found between the clinical, demographic, or radiographic factors and the pattern or quantity of bone ongrowth. Discussion: This study demonstrates that sufficient fixation can be achieved with only limited amounts of bone ongrowth (14.7% in tibial sleeves and 21.3% in femoral sleeves). (C) 2019 Elsevier Inc. All rights reserved.