[Luxations of the Charnley type and Kerboull-modified Charnley-type total prostheses]

The authors have observed 82 dislocations in a series of 4833 total hip prostheses of the Charnley or modified Charnley type. This represents 1.7 p. 100 of the cases. In 26 instances, the hip dislocated only once. In other instances, the dislocation became recurrent. Several factors favoured the incidence of dislocation and could be corrected - malposition of the prosthetic components as shown in radiographs, leverage due to ossification or hypertrophic synovium, and non-union after division of the greater trochanter. In 17 instances, no reason could be found except muscle atrophy. This type of case was difficult to treat and continued to dislocate later.