Protrusio Acetabuli,an Unwelcome Result in Hip Hemiarthroplasty

We report 140 patients with subcapital fractures of the femur, treated by hemiarthroplasty. We used self locking Müller stems Trilock® with modular heads as well as Thompson prostheses, all being cemented. The self locking stems were of Ti-6A1-4V, the Thompsons of chrome-cobalt alloy and the modular heads of stainless steel. Having found 14% to develop protrusio acetabuli, we retrospectively studied the main variables: age, sex, presence or absence of osteoarthritis, osteoporosis, length of the prosthetic neck, disparity of diameters between the head of the femur and the prosthetic head, the type of hemiarthroplasty and the degree of independence of the patients. Patients in their seventies suffered protrusio more than those in their eighties (p=0.0004), as did those with an independent life, in contrast with dependent patients (p<0.05). The modular Muller Trilock® prostheses, with stainless steel heads, protruded in greater number than the Thompson chrome-cobalt type.