Article

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. 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 degrees +/- 3.9 degrees (range, 170.5 degrees
to 190.5 degrees ) and 177.7 degrees +/- 3.5 degrees (range, 173 degrees to 187
degrees ); LLLD, -0.7 mm (range, -30 mm to +25 mm) and +5.1 mm (range, -7 mm to
+21 mm); NSA, 134 degrees +/- 7.5 degrees (range, 100 degrees to 124 degrees )
and 135 degrees +/- 4.2 degrees (range, 124 degrees to 146 degrees ); and femoral
offset, 42 +/- 7.8 mm (range, 24 mm to 68 mm) and 49 +/- 7.5 mm (range, 33 mm to
70 mm). 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. LEVEL OF EVIDENCE: Level III,
prospective diagnostic study.
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Langue : FRANCAIS