TOTAL HIP-ARTHROPLASTY WITHOUT CEMENT IN OBESE PATIENTS - A MINIMUM 2-YEAR CLINICAL AND RADIOGRAPHIC FOLLOW-UP-STUDY

A retrospective study of patients who had had a primary total hip arth roplasty without cement between 1983 and 1990 was done to examine diff erences in clinical and radiographic results between obese and normal- weight individuals. Patients were considered to be of normal weight if the body-mass index (calculated as weight in kilograms divided by hei ght in meters squared) was between twenty and less than thirty, and th ey were considered to be obese if the body-mass index was thirty or mo re. There were 127 normal-weight patients (142 hips) and fifty-five ob ese patients (sixty hips) in the analysis. Eight obese patients (eight hips) who had a body-mass index of forty or more were considered to b e morbidly obese and were examined separately as a subset of the obese group. The duration of follow-up averaged forty-eight months (range, twenty-four to ninety-two months). There were no differences between t he groups with regard to age, diagnosis, the type of stem or cup, the type of bone, the postoperative level of activity, or the duration of follow-up. The obese patients had a significantly greater loss of bloo d during the operation than the patients in the normal-weight group. T here were no significant differences between groups with regard to the prevalence of perioperative complications, the number of units of blo od transfused, the operative duration, or the duration of hospitalizat ion. Of the 202 hips, 184 (91 per cent) were pain-free or only mildly painful at the latest follow-up examination. The normal-weight and non morbidly obese groups had a significant (p < 0.001) increase in each o f the functional measures compared with the preoperative status. The e ight morbidly obese patients had a smaller, yet significant (between p = 0.01 and p = 0.05), increase in most functional measures. The total rate of mechanical failure of the femoral components was 6 per cent ( six revisions for aseptic loosening and two components that were loose radiographically) in the normal-weight group compared with 2 per cent (one revision for aseptic loosening and no components that were loose radiographically) in the non-morbidly obese group (p = 0.28). The tot al rate of failure of the acetabular components was 7 per cent (seven revisions and three components that were loose radiographically) in th e normal-weight group and 8 per cent (three revisions and two componen ts that were loose radiographically) in the non-morbidly obese group ( p = 0.82). There were no failures of a cup or stem in the morbidly obe se patients. The obese patients in this series did not have a higher r ate of complications, with the exception of an increased intraoperativ e loss of blood. They had similar gains in relief of pain and function al abilities and no difference in the rate of mechanical failure compa red with the normal-weight patients. On the basis of these results, af ter an average duration of follow-up of four years, it appears that ob ese patients can benefit substantially from primary total hip arthropl asty without cement and that obesity does not markedly increase operat ive risk. However, substantial differences might occur with long-term follow-up.