The effect of femoral offset modification on gait after total hip arthroplasty.

BACKGROUND AND PURPOSE: A decrease of 15% in femoral offset (FO) has been reported to generate a weakness of the abductor muscle, but this has not been directly linked to an alteration of gait. Our hypothesis was that this 15% decrease in FO may also generate a clinically detectable alteration in the gait. PATIENTS AND METHODS: We performed a prospective comparative study on 28 patients who underwent total hip arthroplasty (THA) for unilateral primary osteoarthritis. The 3D hip anatomy was analyzed preoperatively and postoperatively. 3 groups were defined according to the alteration in FO following surgery: a minimum decrease of 15% (9 patients), restored (14), and a minimum increase of 15% (5). A gait analysis was performed at 1-year follow-up using an ambulatory device. Each limb was compared to the contralateral healthy limb. RESULTS: In contrast to the "restored" group and the "increased" group, in the "decreased" group there was a statistically significant asymmetry between sides, with reduced range of motion and a lower maximal swing speed on the operated side. INTERPRETATION: A decrease in FO of 15% or more after THA leads to an alteration in the gait. We recommend 3-D preoperative planning because the FO may be underestimated by up to 20% on radiographs and it may therefore not be restored, with clinical consequences.

High 10-year survival rate with an anatomic cementless stem (SPS).

BACKGROUND: Proximal cementless fixation using anatomic stems reportedly increases femoral fit and avoids stress-shielding. However, thigh pain was reported with the early stem designs. Therefore, a new anatomic cementless stem design was based on an average three-dimensional metaphyseal femoral shape. However, it is unclear whether this stem reduces the incidence of thigh pain. QUESTIONS/PURPOSES: We asked whether this stem design was associated with a low incidence of thigh pain and provided durable fixation and high function. METHODS: One hundred seventy-one patients (176 THAs) who had the anatomic proximal hydroxyapatite-coated stem implanted were reviewed. Eleven (6%) patients were lost to followup and 34 (20%) died without revision surgery. We used the Harris hip score (HHS) to assess pain and function. We evaluated femoral stem fixation and stability with the score of Engh et al. and also calculated a 10-year survival analysis. We assessed 126 patients (131 hips) at a mean followup of 10 years (range, 8-11 years) RESULTS: At last followup, two patients described slight thigh pain that did not limit their physical activities. All stems appeared radiographically stable and one stem was graded nonintegrated but stable. Five patients had revision surgery: one on the femoral side (for posttraumatic fracture) and four on the acetabular side. Considering stem revision for aseptic loosening as the end point, survivorship was 100% (range, 95.4%-99.9%) at 10 years. CONCLUSION: This anatomic cementless design using only metaphyseal fixation with a wide mediolateral flare, a sagittal curvature, and torsion, allowed durable proximal stem stability and fixation.

Three-dimensional hip anatomy in osteoarthritis. Analysis of the femoral offset.

Two hundred twenty-three patients with osteoarthritic hips were analyzed using computed tomography and a specific image processing software (HIP-PLAN) to determine 3-dimensional morphological data of the hip focusing on femoral offset (FO). Mean FO was found to be 42.2 +/- 5.1 mm, 2.2 mm greater than the 2-dimensional FO values reported in the literature. The FO was found to be above 45 mm in 31% of patients and greater than 50 mm in 12%. The error associated with the use of conventional plane x-rays to measure FO was found to be 3.5 +/- 2.5 mm, the x-ray technique generally underestimating the measure of FO. The sum of acetabular and femoral anteversion was found to be out of the safe zone regarding dislocation risk in 47% of patients.