The impact of bone atrophy on the stability of cementless hip replacements in the oldest old. A post-mortem analysis

Abstract

Background Continual implant stability is an important factor for the long-term success of cementless hip replacements. The increasing lifespan of patients causes a higher frequency of osteoporosis which may result in implant loosening due to bone loss. This study aimed to evaluate stability of long living implants in patients with advanced age. Patients and methods Nine cementless stems made of Titanium-alloy including adjacent bone tissue obtained post mortem were evaluated by radiologic-microradigraphical, histological and morphometrical analysis. The percentage of the surface area covered by bone (BICI=bone implant contact index) was determined. The age of seven women and two men ranged between 81 and 92 years. The time in situ ranged between 10 and 20 years. From the entire length of the femora bearing implants 5 transverse segments were excised, dehydrated, embedded in methylmethacrylate. After the grinding procedure, the sections were evaluated by light microscopy and morphometrical analysis. The autopsy findings were recorded. Atherosclerosis and their related diseases were evident in all cases. Results The femora of all female patients revealed features of high bony atrophy with concomitant transformation of the corticalis into spongy bone, whereas in male patients minor to moderate atrophic bone changes in the proximal femoral area without implication of the corticalis could be observed. All of the cementless stems made of Titanium-alloy showed osteointegration. The stabilization of the implant resulted in the forceps-like encasement of the edges of the implant within the cortical anchoring and by the development of compensatory bony hypertrophy. The BICI ranged between 35 und 63 percent. Conclusion Elderly patients provided with cementless hip replacments revealed stable implants in spite of marked bone atrophy and an implantation period up to 20 years. Simultaneously, severe atherosclerosis and their related diseases, which may contribute to bone loss, were evident. The present findings may result from the favoring properties of cementless endoprostheses made of titanium alloy, cortical prosthesis anchoring, and self regulating bone processes. Pharmacologic and therapeutic consequences together with geriatric assessment should be required to preserve functionality and mobility.