Abstract
Cementless total hip arthroplasty (cementless THA) is a surgical approach established as a treatment for coxarthrosis. However, this approach is very invasive and associated with many worrying factors including whether the operation is safe especially in an elderly patient, whether stable primary fixation is available and whether walking is achieved immediately after operation or in the long term. This study investigated the usefulness of cementless THA with emphasis on comparison with clinical results of the femoral head prosthetic replacement performed for femoral neck fractures. The subjects were 133 joints in patients aged 75 years and older who underwent cementless THA at our department. The radiographic evaluation was used to examine biological fixation and the incidence of stress shielding by the implant according to the classification of Engh. Although a variety of components were used, the biological fixation did not differ among components. There were no findings showing obvious implant loosening by bone ingrowth fixation in 96% of the subjects and by fibrous fixation in the remaining 4%, and none of the patients required re-replacement. Stress shielding was found at a high frequency with AML models. Strong fixation was obtained in the distal region of the femur but atrophy of the proximal cortical bone became remarkable at the same time, although none of the cases had any clinical issue. A high incidence of stress shielding occurred in cases of 13-mm stem size and over, canal-flare index under3, and cortical index under 0.4. We consider treating preservation bone quality and select the stem to maintain as much bone stock as possible in case of wide marrow cavity. Clinical results were evaluated by follow-up examination of outpatients, death rates during 1-5 postoperative years, and the walking status at discharge from hospital up to 5 postoperative years in the following three groups: THA, monopolar head and bipolar head. No significant difference was observed between the monopolar and bipolar groups. The follow-up rate as outpatients and survival rate of the THA group were higher in comparison to those of the other two groups. About 90% of patients were ambulant or walked with a cane immediately after discharge from hospital. Both pain and ADL, parameters set by the Japanese Orthopaedic Association to evaluate hip joint function, improved remarkably in comparison to the preoperative condition. The cementless THA is considered to be relatively satisfactory and effective and does note present serious complications.
