title: The influence of leg length difference on clinical outcome after revision TKA.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  Leg 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).
  
  
  RESULTS
  Revision 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).
  
  
  CONCLUSIONS
  The results from our work indicate that revision TKA tends to lengthen the leg by approximately 5mm. Contrary to what might be expected, leg lengthening after revision TKA is correlated with improved clinical outcome.
  
  
  METHODS
  Level 2b.
authors.affiliation: Department of Orthopaedic Surgery, University Hospitals Leuven, Weligerveld 1, 3012 Pellenberg, Belgium. Electronic address: shevan.mufty@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Mufty
authors.affiliation: Department of Orthopaedic Surgery, University Hospitals Leuven, Weligerveld 1, 3012 Pellenberg, Belgium.
authors.forename: H
authors.initials: H
authors.lastname: Vandenneucker
authors.affiliation: Department of Orthopaedic Surgery, University Hospitals Leuven, Weligerveld 1, 3012 Pellenberg, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Bellemans
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D006801:Humans; D007593:Joint Instability / Q000601:surgery; D007719:Knee Joint / Q000601:surgery; D007870:Leg Length Inequality / Q000000981:diagnostic imaging* / Q000209:etiology; D016014:Linear Models; D035002:Lower Extremity / Q000000981:diagnostic imaging*; D010147:Pain Measurement; D063868:Patient Outcome Assessment; D011446:Prospective Studies; D011859:Radiography; D016059:Range of Motion, Articular; D012086:Reoperation
keywords: Knee; Leg length difference; Outcome; Revision; TKA