Interest of an intraoperative limb-length and offset measurement device in total hip arthroplasty.

INTRODUCTION: Total hip arthroplasty (THA) seeks to restore a stable, mobile and pain-free joint. This requires good implant positioning and peroperative restoration of limb-length and femoral offset.

HYPOTHESIS: A mechanical measurement device (length and offset optimization device [LOOD]) fixed to the pelvis can optimize lower-limb length and offset control during THA performed on a posterolateral approach.

PATIENTS AND METHODS: Two prospective THA series were compared: 32 using the LOOD and 26 without. Patients with more than 5mm preoperative limb-length discrepancy were excluded. The intraoperative target was to restore individual anatomy. Radiographic analysis was based on pre- and postoperative AP pelvic weight-bearing views in upright posture, feet aligned, with comparison to peroperative LOOD data.

RESULTS: Mean deviation from target length (i.e., pre- to postoperative length differential) was 2.31 mm (range, 0.04-10.6mm) in patients operated on using the LOOD versus 6.96 mm (0.01-178 mm) without LOOD (P=0.0013). Mean deviation from target offset was 3.96 (0.45-13.50) mm with LOOD versus 10.16 (0.93-28.81) without (P=0.0199). There was no significant difference between operative and radiographic measurements of length deviation using LOOD (P=0.4); those for offset, however, differed significantly (P=0.02).

DISCUSSION: The LOOD guides control of limb-length and offset during THA on a posterolateral approach. Reliability seems to be better for limb-length than for offset. It is a simple and undemanding means of controlling limb-length and offset during THA.

LEVEL OF EVIDENCE: III, prospective case-control study.