Classifying Bone Loss in Failed Stemmed Total Knee Arthroplasty: Determining Reliability.

BACKGROUND: Failed stemmed total knee arthroplasty (TKA) components present with varying degrees of bone loss and technical challenges. A classification system has been proposed based upon metaphyseal bone loss and diaphyseal cortical integrity. A validation study was performed to determine interobserver and intraobserver reliability at multiple institutions and with different levels of training. METHODS: An online survey with digital anteroposterior and lateral radiographs was sent to 5 arthroplasty surgeons and 5 adult reconstruction fellows. The survey included 62 cases with stemmed femoral and tibial components, considered failures and pending revision, and scored by each reviewer independently using the classification system. Each case was scored in 2 separate sessions. Interobserver and intraobserver reliability was assessed using the intraclass correlation coefficient (ICC). RESULTS: Interobserver grading for both the femur (0.69) and tibia (0.72) showed strong reliability among the attendings and fellows, with slightly stronger reliability in tibia cases. The intraclass correlation coefficient (ICC) for attendings and fellows was similar overall, demonstrating consistency of the grading regardless of training level. Intraobserver comparisons showed a strong ICC for attendings and fellows in femoral cases, while fellows had near-perfect ICC in tibia cases. Across all reviewers there was on average 93% agreement within 1 grade per case with the majority of the discrepancy occurring at the metaphyseal-diaphyseal junction. CONCLUSION: This classification demonstrated overall strong interobserver and intraobserver reliability, with 93% agreement within 1 grade of bone loss. With further education, this classification system can ultimately be used to standardize the degree of bone loss in failed stemmed components and help with preoperative planning.