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Lateral tibial plateau reference point for tibial resection in total knee arthroplasty in patients with tibial bowing.


Presenting Author - Rajshekhar K.T.
Background - Extramedullary guides referenced to the center of the intercondylar eminence are usually preferred for alignment of the tibial component in total knee arthroplasty. However, the tibial cut referenced to the center of the intercondylar eminence leads to a varus malalignment in the presence of pre-existing proximal tibial bowing. Methods – In this prospective cohort study, sixty-two patients (94 knees) with osteoarthritis and tibial bowing underwent primary total knee arthroplasty with a lateral tibial plateau reference point for the extramedullary jig. The preoperative and postoperative radiographs were measured for mechanical axis deviation, degree of tibial bowing, proximal lateral reference point of tibial condyle, and coronal alignment of femoral and tibial components. Results - The mean lateral displacement of the reference point was 7 mm (SD – 2.24 mm). Post-operative tibio-femoral angle was 6 to 10 degrees of valgus in 94% percent of cases. There was a strong correlation between the magnitude of tibial bowing and the amount of lateralization of the tibial reference point. Conclusions - In TKA in patients with proximal tibial bowing, reasonable accuracy can be achieved with the use of extramedullary jig for tibial component alignment by lateralizing the proximal tibial reference point. Unlike the recommendations of the previous studies that lateral intercondylar eminence should be used as a reference point in the presence of varus bowing of the tibia, we recommend that lateralization should be individualized based on the deformity. With higher degrees of varus, the reference point may lie further lateral to the lateral intercondylar eminence.