We assessed outcome after total hip arthroplasty (THA) using a dual metaphyseal-diaphyseal modular femoral stem with hydroxyapatite coating on the metaphyseal portion only. Implanted without cement, this stem was adaptable to all the anatomic morphotypes defined by the Noble canal flare index.
THA was performed in 116 patients (124 hips), mainly for degenerative joint disease (80% for dysplasia). Mean age was 61.2 years. Follow-up was 6.9 years (72-108 months).
There were no preoperative complications excepting 3 cases of neck fissuration without clinical consequence. There was no trochanteric fracture. We had two early and one late dislocations. The Postel Merle d'Aubigné score improved from 8.09 to 17.27. Clinical outcome was not influenced by patient age, weight or morphotype. Radiologically, signs of bone ingrowth were found in more than 80% of the cases. Lucent lines were seen in only 3 cases. There was a single case of migration. No revision was needed among the cases with ossifications (23%, 22% Brooker I) and no femur revisions were required. There was no mechanical problem involving the metaphyseal-epiphysial junction.
The dual metaphyseal-diaphyseal modular stem was found to be a safe and effective implant adaptable to all anatomic variations of the femur and providing good primary stability. In our series, 58% of the femurs were "standard" but for one-third of the femurs, the modular stem enabled implantation without cement, particularly in young adults with a dysplasic or funnel-shaped femur.
The dual metaphyseal-diaphyseal modular stem was found to be most useful for optimizing total hip arthroplasty without cement.