Can Preoperative Radiographic Analysis Help Us Evaluate When to Use Metaphyseal Cones?

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Revision total knee arthroplasty (TKA) can be challenging in the setting of bone loss. Previously, severe bone loss was managed with impaction grafting and structural allografts; however, these had limited success. Recently, metaphyseal cones have been developed as useful adjuncts with good early outcomes. Presently, there are no published guidelines on how to preoperatively predict the need for metaphyseal cone implantation radiographically. Therefore, the purpose of this study was to evaluate how well preoperative radiographs were able to predict the use of cones in a small series of patients undergoing revision TKA. In this study, three patients who were undergoing a revision TKA were evaluated radiographically. For each case, we used the Knee Society Roentgenographic Evaluation and Scoring System to assess for osteolysis and bone loss or defects. The intraoperative findings of bone loss that may have necessitated the use of cones were described and correlated with preoperative evaluation. The first patient had obvious osteolysis of both tibia and femur on anteroposterior (AP) and lateral radiographs. The preoperative radiographs predicted the need for a cone in both tibia and femur. The intraoperative findings correlated with preoperative radiographs. In the second case, there was obvious osteolysis of the tibia on AP and lateral films. The surgeon predicted the need of a tibial cone for tibial component placement based on these X-rays. The intraoperative findings confirmed this. In the third case, the patient had obvious osteolysis surrounding tibial component on both AP and lateral radiographs. The preoperative radiographs revealed the need for tibial cone only. Intraoperatively, the tibial findings correlated with the preoperative radiographs, but the femur revealed a large defect which required use of a metaphyseal cone. All three patients had marked radiolucencies and osteolysis surrounding the tibial component, and one of the three patients surrounding the femoral components. In this case series, the radiographs predicted the need for four out of five cones. The Knee Society Roentgenographic Evaluation and Scoring System may be a potential option for a radiographic evaluation method to predict the need for cones in revision TKA. It is hoped that this study will provide a starting point for future larger scale studies to assess the predictive need for cones in revision TKA.

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