Relation between lower extremity alignment and proximal femur anatomy. Parameters during total hip arthroplasty - 25/06/13

Doi : 10.1016/j.otsr.2013.02.006

M. Ollivier, S. Parratte ^⁎ , L. Lecoz, X. Flecher, J.-N. Argenson
Motion research and musculo-skeletal institute, Southern Teaching Hospital Center, Sainte-Marguerite Hospital, 270, boulevard Sainte-Marguerite, 13009 Marseille, France

^⁎Corresponding author. Tel.: +33 491 745 011; fax: +33 491 745 625.

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En prensa. Pruebas corregidas por el autor. Disponible en línea desde el Tuesday 25 June 2013
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Summary

Background

Lower extremity alignment correlates with native femoral offset. Eventual impact of the change in femoral offset induced by total hip arthroplasty (THA) on lower extremity alignment has not been documented.

Hypothesis

THA significantly changes lower extremity alignment, and the change correlates with the change in femoral offset.

Materials and methods

We conducted a prospective study of 200 patients with primary hip osteoarthritis or avascular femoral head necrosis who underwent cementless THA. Pre-operative computed-tomography templating was performed and the femoral component was then custom-manufactured to replicate the native femoral anatomy. Mean age was 58 years (range, 28–83 years). Before and at least two years after THA, two observers who were not involved in the surgical procedures used standing antero-posterior long-leg radiographs to determine the mechanical axis of the lower-limb (hip-knee-ankle [HKA] angle), femoral offset, neck-shaft angle (NSA), and lower-limb length discrepancy (LLLD).

Results

Mean values pre-operatively and at last follow-up were as follows: HKA angle, 179.2°±3.9° (range, 170.5° to 190.5°) and 177.7°±3.5°(range, 173° to 187°); LLLD, −0.7mm (range, –30mm to+25mm) and+5.1mm (range, –7mm to+21mm); NSA, 134°±7.5° (range, 100° to 124°) and 135°±4.2° (range, 124° to 146°); and femoral offset, 42±7.8mm (range, 24mm to 68mm) and 49±7.5mm (range, 33mm to 70mm). Although THA significantly altered lower-limb alignment, univariate and multivariate analyses showed no significant association between the change in HKA angle and the change in femoral offset.

Discussion

Lower-limb alignment was significantly affected by THA, although the HKA angle changes were small. The small impact of THA on HKA angle values may be ascribable to efforts aimed at replicating the native femoral offset during arthroplasty, as well as to the limited sample size and to potential measurement errors related to the small size of the changes. Our results suggest that, provided careful attention is directed to replicating the native femoral offset, THA in patients with limited pre-operative anatomical abnormalities may have no major impact on the biomechanical parameters of the ipsilateral knee.