The influence of leg length difference on clinical outcome after revision TKA

BackgroundThe purpose of this paper was to document the incidence of leg length changes after revision total knee arthroplasty (TKA) and its effect on clinical outcome.MethodsLeg length difference (LLD) was prospectively measured in 85 patients using digital standing full leg radiography before and after revision TKA. Additionally the patient's subjective perception of LLD was assessed postoperatively. Linear regression models were used to study the correlation between each of these parameters and the clinical outcome after 1 year. Clinical outcome was evaluated by means of the Knee Society Score (KSS).ResultsRevision TKA resulted on average in an increased leg length of 5.3 mm. Sixty-five legs (76%) were lengthened with the procedure, 17 (20%) were shortened and three (4%) remained of identical length. Increased leg length after revision was positively correlated with clinical outcome at 3 months (Spearman r = 0.22, p = 0.044) and 1 year (Spearman r = 0.26, p = 0.027). The evidence for this correlation remained after correction for age, gender and diagnosis (p = 0.012). The most important contributors to improved clinical outcome scores were improved pain score (Spearman r = 0.19, p = 0.09) and increased stability (Spearman r = 0.13, p = 0.24), rather than range of motion (Spearman r = − 0.02, p = 0.85).ConclusionsThe results from our work indicate that revision TKA tends to lengthen the leg by approximately 5 mm. Contrary to what might be expected, leg lengthening after revision TKA is correlated with improved clinical outcome.Level of evidenceLevel 2b.