Changes in bone mineral density around the femoral stem after total hip replacement: a preliminary report

Background. Degenerative changes in the hip, accompanied by clinically significant pain, decrease the range of motion in physical examination and give characteristic changes in X-ray images. Total hip replacement is most often indicated. The most important factor affecting the usable life of implants is the adaptive rebuilding of osseous tissue in this region. A typical radiological examination showing the hip prosthesis and surrounding osseous tissue gives only late, qualitative indications of possible loosening of the prosthesis. Examination of bone mineral density (DEXA) gives quantitative data on changes occurring in the immediate region of the hip prosthesis, enabling early assessment of prothesis endurance. The aim of our study was to compare proportional changes in the BMD of the proximal femur after cemented and cementless total hip replacement. Material and methods. Densitometry of osseous tissue was done with a LUNAR device, using the Orthopedic computer program, in two groups of female patients after total hip replacement. BMD changes were analyzed occurring around the femoral stem 3 months after surgery using autoanalysis in the 7 Gruen zones. Examinations were done across different types of hip prosthesis. Results. In both groups our preliminary data point to a proportional decrease in BMD in all the analyzed zones. The greatest decreases occurred in zones 1 and 7, the least in zone 4. Conclusions. DEXA allows for quantitative monitoring of changes in osseous tissue in the region around the prosthesis.