Proximal Femoral Shape Changes the Risk of a Leg Length Discrepancy After Primary Total Hip Arthroplasty.

BACKGROUND

To evaluate how canal morphology affects the technical aspects of total hip arthroplasty, we investigated the effects of femoral cortical index (FCI) on the re-establishment of leg length at the conclusion of surgery.

METHODS

We retrospectively reviewed age, gender, body mass index, and radiographs of 516 patients with osteoarthritis or osteonecrosis who underwent unilateral cementless primary total hip arthroplasty between 2008 and 2015. Patients were divided into level of FCI and leg length discrepancy (LLD). Each cohort was compared in terms of demographics and LLD. One-way analysis of variance and Kruskal-Wallis test were used.

RESULTS

The mean FCI and LLD were 0.6 ± 0.1 and 3.5 ± 6.3 mm, respectively. Utilization of an extended offset stem was highest with Dorr type A and B hips (P = .001). High FCI increased the risk of lengthening (P = .017) and low FCI increased the risk of shortening (P = .005).

CONCLUSION

A high FCI increases the probability of a leg length increase and a low FCI increases the probability of a leg length decrease. Surgeons might consider informing patients in advance of possible variation in leg length depending on the patients' proximal femoral shape and bony quality.