Validity and Reliability of Intraoperative Radiographs to Assess Leg Length During Total Hip Arthroplasty: Correlation and Reproducibility of Anatomic Distances.

BACKGROUND: Leg length discrepancy after total hip arthroplasty is a frequent complication. The aim of this study was to assess the validity (correlation) and reproducibility (inter-rater agreement) of various intraoperative hip radiographs measures to estimate leg length. METHODS: Patients were included if they were aged 15 years or older; were eligible for a total hip arthroplasty, and were operated in lateral recumbent. An intraoperative hip radiograph was performed with the definitive implants in place. At 6 weeks postoperatively, anteroposterior pelvis radiograph was taken. We used 3 measures to assess leg length: the height from the ischial tuberosity to the lesser trochanter (LTI), the height from the center of femoral head to the greater trochanter (GTC), and to the inferior teardrop (TC). RESULTS: The study group consisted of 71 hips with an average age of 69 years (range, 24-92 years). The correlation was 0.545 (95% CI: 0.35-0.69) for GTC, 0.75 (95% CI: 0.61-0.84) for TC, and 0.70 (95% CI: 0.56-0.80) for LTI. Intraoperative and postoperative measures were statistically different for GTC (<0.0001) and TC (<0.0001), and not significant for LTI (P = .06). Reproducibility of these measures were excellent with intraclass correlation coefficients of 0.977, 0.814, and 0.983 for the GTC, TC, and LTI, respectively. CONCLUSION: None of the parameters used to assess leg-length based on an intraoperative radiograph showed good correlation with the postoperative radiograph.