Abstract
Introduction
The purpose of this study was to evaluate the functional and radiographical results in patients who underwent a modified minimally invasive two-incision total hip arthroplasty using large-diameter metal-on-metal articulations for osteonecrosis of the femoral head.
Methods
From December 2007 to July 2008, 45 hips (33 patients) underwent total hip arthroplasty for the treatment of osteonecrosis of the femoral head. There was 1 woman (2 hips) and 32 men (43 hips) who had a mean age of 39 years (range, 22 to 64 years). The minimum follow-up was 12 months (range, 12 to 19 months). The authors modified the original minimally invasive two-incision total hip arthroplasty technique and used large-diameter metal-on-metal articulations. In the lateral position, an anterolateral approach was used between the gluteus medius and tensor fascia lata muscles and for the posterior approach the muscle plane was between the piriformis and gluteus medius muscles. The acetabular components, Durom¯ (Zimmer) in 20 hips and Magnum¯ (Biomet) was used in 25 hips. M/L taper¯ (Zimmer) femoral stems were used in all cases. The size of the femoral heads were 38 mm (1 hip), 40 mm (3 hips), 42 mm (13 hips), 44 mm (18 hips), 46 mm (5 hips), 48 mm (4 hips) and 50 mm (1 hip). Postures such as excessive flexion or adduction which cause dislocation were not restricted, post-operatively. Functional results were measured by Harris hip scores (HHS), WOMAC scores, and range of motion. Radiographic evaluation was assessed for positions of components and post-operative complications were noted.
Results
Mean operation time was 72 minutes (range, 54 to 94 minutes). The mean Harris hip score improved from 50 points (range, 38 to 73 points) pre-operatively to 96 points (range, 84 to 100 points) post-operatively, and the mean WOMAC score improved from 68 points (range, 50 to 93 points) to 28 points (range, 26 to 34 points). The mean flexion improved from 85° pre-operatively to 122° post-operatively. The mean internal rotation improved from 2.5° pre-operatively to 25.3° post-operatively. The mean external rotation improved from 31.8° pre-operatively to 60.1° post-operatively. The mean abduction improved from 24.0° pre-operatively to 41.6° post-operatively. The mean adduction improved from 19.4 ° pre-operatively to 26.6° post-operatively. All patients were able to sit cross legged and squat. On radiological evaluation, the mean lateral opening angle of the acetabular component was 39.4° (range, 32.2°-48.5°) and the mean stem position was valgus 0.3° (range, varus 2.8° to valgus 2.0°). At last follow-up, all femoral and acetabular components were well-fixed without loosening or subsidence. There were no complications such as dislocation, immediate post-operative deep infection or delayed infection.
Conclusion
Modified minimally invasive two-incision total hip arthroplasty using large-diameter metal-on-metal articulations for osteonecrosis of the femoral head results in satisfactory early clinical and radiologic results.
