Analysis of the Fit of Modern Pre-contoured Distal Femur Plates: Expect an Imperfect Contour

Abstract The purpose of this study was to determine if the contour of current distal femur plates can reliably be used as a reduction tool and to determine if the presence of a total knee arthroplasty (TKA) influences fit. Thirty-two patients were retrospectively reviewed. Radiographs of 19 patients with normal knees and 21 patients who had undergone TKA were evaluated. Using TraumaCad templating software, the contours of 4 different modern distal femur plates (Depuy Synthes, Stryker, Zimmer Biomet, and Smith & Nephew) were analyzed using a novel measurement technique to evaluate plate fit. To mimic non-locking screws in the shaft, the template was placed on the shaft and the plate to bone (PTB) and condyle to plate (CTP) distances were recorded. The PTB distance measured how closely the plate matched the contour of the metaphyseal flare, while the CTP value represented the distance from the plate to the distal articular surface. Larger PTB and CTP distances represent a higher mismatch between the patient's anatomy and the contour of the plate. There was significant variability in plate fit in all patients. None of the plates fit the patient's anatomy well, with PTB values averaging from 5.5mm to 9.2mm. There was no significant difference between normal radiographs and TKA radiographs, suggesting that the presence of a TKA may not contribute to plate fit. The results of this study show that current plate designs may not match the patient's native anatomy prior to fracture. Therefore, caution should be utilized when using non-locking screws in the shaft and using the pre-contoured nature of the plate as a template for reduction. The authors advocate for careful preoperative planning and using contralateral radiographs for templating purposes to prevent malreduction and to assist in device selection for the best device fit per patient.