Leg length discrepancy after total hip arthroplasty: Can leg length be satisfactorily controlled via anterior approach without a traction table? Evaluation in 56 patients with EOS 3D.

BACKGROUND: Leg length discrepancy (LLD) occurs in about 25% of cases after total hip arthroplasty (THA) and adversely affects function if greater than 10mm. When using the direct anterior approach (DAA), limb length control is considered easier with a standard operating table than with a traction table. However, this assumption has not been confirmed. More specifically, no studies have used EOS imaging, which is currently the reference for assessing limb length. The objectives of this retrospective study were: (1) to use EOS imaging to determine whether THA via the DAA on a standard table allowed satisfactory limb length control; (2) whether LLD was associated with other parameters such as age, gender, body mass index (BMI), or side; and (3) to compare clinical score values between patients with and without LLD.

HYPOTHESIS: The DAA without a traction table allows satisfactory limb length control as assessed using 3D EOS imaging.

MATERIAL AND METHODS: This retrospective descriptive study included 56 patients who underwent primary THA via the DAA between March 2013 and June 2014. LLD was measured on pre- and post-operative EOS images, using sterEOS™ 3D software. Age, gender, BMI, and side of THA were collected. The 12-item Short Form score, Harris Hip Score, and Postel-Merle d'Aubigné score were determined to look for radio-clinical correlations.

RESULTS: Of the 56 patients, 15 (26.8%) had an LLD >10mm before THA and 12 (21.4%) after THA. Limb length equality was restored in 7 patients with 1 with a shorter and 1 with a longer limb before THA. In 5 patients with equal limb length before THA, the operated limb was lengthened after THA, by a mean of 8.92mm (range, 5.8-10.8mm). Thus, in all, 5/56 (8.9%) patients experienced a detrimental change in limb length due to the surgery. No statistically significant differences were found between patients with and without LLD regarding age, gender, BMI, side, or clinical scores.

DISCUSSION: Although the frequency of LLD after THA in our study was consistent with earlier reports, our results show that good limb length control can be obtained via the DAA with a standard operating table. Thus, 7 of the 11 patients with a shorter limb and 1 of 4 with a longer limb before THA had equal limb lengths after THA, and only 8.9% of patients experienced a detrimental increase in limb length after THA. The DAA without a traction table allows satisfactory intra-operative limb length control based on visualisation of anatomical landmarks (antero-superior iliac spines and medial malleoli). This technique is therefore valuable for limiting the risk of LLD. When combined with 3D EOS planning, it may increase the accuracy of limb length adjustment.

LEVEL OF EVIDENCE: IV, retrospective study with no control group.