Postoperative Development of Bone Mineral Density and Muscle Strength in the Lower Limb After Cemented and Uncemented Total Hip Replacement

BACKGROUND Numerous studies have shown reduction of periprosthetic bone mineral density (BMD) after hip replacement. The effect on the whole limb, however, is still unexplored. This study's objective was to analyse the postoperative development of BMD and muscle strength of the limb after total hip replacement (THR) and to determine links between these parameters. METHODS 55 patients, who underwent THR, were included. Depending on therapeutic indication, either an uncemented stem (Group A, n=30) or a cemented stem (Group B, n=25) has been implanted. In the limbs, the measurement of BMD using DEXA and the maximum isometric muscle strength, detected by a leg press, were undertaken preoperatively and after 3, 6 and 12 months. RESULTS A total of 12 patients (Group A: n = 6, Group B: n = 6) were excluded due to reasons which were not relevant to the study. So, the results refer to the data of 43 patients. In Group A (uncemented, n = 24), a significant decrease of BMD on the operated extremity was seen after 3, 6 and 12 months compared with preoperative values. Isometric muscle strength on the affected extremity increased significantly after 6 and 12 months. In Group B (cemented, n = 19), with a lower baseline compared to group A, an increase in BMD of the affected limb was seen postoperatively. This rise was significant after 12 months. With regard to the isometric muscle strength, a significant increase could be observed in this group after 6 and 12 months. CONCLUSION Analogous to postoperative reduction of periprosthetic bone density, a decrease of the entire limb BMD on the operated leg occurred after implantation of uncemented hip stems. In contrast, an increase in BMD was recorded for cemented stems. Regardless of the type of anchoring, a substantial increase in muscular strength could be observed postoperatively in both groups.