Intramedullary and extramedullary tibial alignment guides applied to each knee of the same patient resulted in no significant differences in radiological or clinical outcomes.

backgroundThe superiority of intramedullary versus extramedullary alignment guides in total knee arthroplasty remains controversial, with previous studies reporting inconsistent results. Unlike studies comparing different patient groups, this study controlled for inter-patient variables by applying each method to the left and right knees of the same patients.

methodsWe retrospectively reviewed 344 patients (688 knees) who underwent bilateral TKA between March 2012 and December 2023. After excluding cases with the same guide used for both knees, revision procedures, PROSTALAC insertion, and loss to follow-up, 94 knees (47 patients) were analyzed. Each patient received IM guidance in one knee and EM guidance in the other, performed by a single experienced surgeon using a standardized technique. Radiological parameters (hip-knee-ankle axis, medial proximal tibial angle, joint line convergence angle, posterior tibial slope) and clinical measures (flexion contracture, further flexion, range of motion) were compared at a minimum of 12 months postoperatively.

resultsNo significant differences were found between IM and EM groups in postoperative radiological alignment (HKA axis, p = 0.308; MPTA, p = 0.523; JLCA, p = 0.984; posterior slope, p = 0.269) or clinical outcomes (flexion contracture, p = 0.339; further flexion, p = 0.724). Both methods achieved similar improvements from preoperative values.

conclusionsIM and EM guides provided comparable radiographic and clinical outcomes, allowing flexible selection based on patient anatomy and surgical conditions.