Incidence of Leg Length Discrepancy Following Index Hinge Total Knee Arthroplasty

Abstract Background Leg length discrepancies (LLD) are not commonly associated with total knee arthroplasty (TKA); however, hinge TKA is a complex form of knee reconstruction where functionality of all knee ligaments is replaced by the TKA construct. The purpose of this study is to evaluate incidence of LLD following unilateral index hinge TKA and association with patient outcomes. Methods A retrospective review was performed of all patients that underwent unilateral index hinge TKA at a single academic institution from 1999-2019. Among 671 patients that had index hinge TKA, 188 (28%) had full length standing anteroposterior hip-to-ankle radiographs available for review both preoperatively and postoperatively. All patients with a leg length change ≥2 cm were also contacted with a standardized questionnaire to assess for complications. Mean age was 65 years, mean body mass index was 33 kg/m2, and 52% were female. Mean number of prior surgeries was 2 (range, 0–12). Results The absolute mean and median change in leg lengths was 20 mm and 13 mm, respectively (range, 0–130 mm). Lengthening occurred in 119 patients (63%) compared to shortening in 69 patients (37%). An absolute change in leg lengths ≥1 cm was observed in 109 patients (58%), ≥2 cm in 63 patients (34%), and ≥5 cm in 15 patients (8%). Conclusion Large changes in leg length are common following hinge TKA, likely secondary to altered soft tissue constraints. Surgeons should be cognizant of potential changes in leg length in the setting of hinge TKA and incorporate this into preoperative planning and patient counseling. Level of Evidence Level IV, therapeutic