Fractured stem in total hip replacement. A clinical review of 120 cases.

Clinical review of 120 cases of fractured stem of the now obsolete Charnley "flat back" has shown an incidence of 1.15 per cent. The period of risk was the 11 years from the time of surgery and 97.5 per cent fractured during that time. Before the fractured occurred 87.8 per cent had normal hip function. There was a linear relationship between the patients' weight and the time of the fracture. Patients of comparable weight, and referred from other units, fractured the stem earlier than patients from our unit. Radiographic evidence of failure of the femoral stem fixation, within 1 year of surgery, was found in 77.2 per cent of the hips where serial radiographs were available. This group fractured the stem, on average, 17.3 months earlier. Loss of calcar height was present in 73.3 per cent and was a technical problem at revision. Study of varus/valgus orientation of the stem did not bear out the commonly held opinion; in patients of comparable weight valgus stems fractured earlier than varus stems. Mechanical loosening of the socket in the group was 12.9 per cent. Detachment of the trochanter following revision was 12.1 per cent and the dislocation rate 5.2 per cent. The findings suggest that the surgical technique, as regards preparation of the medullary canal and the cement injection, and the patients' weight, are the most important factors in the complication under study.