Abstract
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.
Highlights
Numerous studies have shown reduction of periprosthetic bone mineral density (BMD) after hip replacement
Analogous to various studies, which describe a periprosthetic bone loss after cementless total hip replacement (THR) [3-6, 30], we found a decrease in BMD at the entire operated limb 3, 6 and 12 months after implantation of cementless stems
The question to be answered in this study was whether objectified, easy to determine parameters, such as strength or BMD measurement of the limb after primary hip replacement show a characteristic profile and to find out to what extent the previously described periprosthetic bone loss applies to the entire limb, so that by an objective assessment the possible functionality of a hip prosthesis can be determind
Summary
Numerous studies have shown reduction of periprosthetic bone mineral density (BMD) after hip replacement. 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. Total hip replacement (THR) is currently one of the most successful procedures in orthopaedic surgery [1]. More than 1 million THR are implanted annually, about 150,000 of them in Germany alone. A durable endoprosthetic care requires a stable anchoring of the implant in the bone. For cemented replacements, this is achieved by creating an even cavity-free cement coat and by a constant cement penetration into the spongiosa. Primary stability must first be achieved intraoperatively by use of "press-fit" fixation
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