Effect of a stemless femoral implant for total hip arthroplasty on the bone mineral density of the proximal femur. A prospective longitudinal study.

After total hip arthroplasty with a medullary stem, significant loss of bone mineral density (BMD) has been demonstrated in the proximal-medial femoral cortex. In an attempt to prevent bone loss, a stemless femoral component was designed. Owing to promising experimental results, a prospective clinical trial was undertaken in a limited group of patients, all below the age of 50. Yearly BMD measurements were carried out in the vicinity of the implant and compared with the BMD values obtained in the immediate perioperative period and with the values on the unaffected side. The follow-up period in this study was 4 to 6 years, involving 32 hips in 31 patients. Maintenance of BMD in the operated femur was demonstrated. A statistically significant increase in the BMD of the proximal medial femoral cortex was observed in those patients who had low initial values. In active patients with a life expectancy greater than 30 years, preservation of the proximal bone stock after total hip arthroplasty appears beneficial, as these patients are most likely to need revision surgery, which is more difficult if significant bone loss has occurred. The data further reinforce the crucial role of mechanical stress in BMD maintenance.