Late complications after total hip arthroplasty

Abstract: The present study concerns late complications after total hip arthroplasty in relation to implant material, design, and mode of implant fixation. Frictional characteristics in retrieved and new acetabular sockets was studied under dry and lubricated conditions comparing conventional polyethylene sockets with polyacetal sockets from the Christiansen prosthesis. No difference between new sockets of the two materials was found, whereas the friction in 12 retrieved polyacetal sockets was significantly higher than in 6 new and 6 retrieved polyethylene sockets. The annual average wear of 12 retrieved polyacetal cups was 240 + 50 mm[3]. Periprosthetic tissue samples from 18 patients with polyethylene and 16 with polyacetal sockets were assessed in a comparative morphological study showing significantly more inflammation and necrosis in the polyacetal group. Polyacetal wear particles were smaller (l-loµ) than those from polyethylene cups which may be an important factor for the severe tissue response. In a retrospective study 70 patients with uncemented Lord prostheses were followed for nearly 10 years. Pain and radiological changes were recorded at 1 and 5 years and at the latest follow-up. Twenty-five patients (36 %) complained of thigh pain. Radiological changes interpreted as adaptive bone remodelling, progressed throughout the period of observation. Physically active patients with thigh pain had less proximal bone loss than less active ones. New bone formation was associated with radiolucencies at the mid-stem level indicating that the elastic relative displacement may contribute to the pattern of bone remodelling seen with bulky uncemented implants. Thigh pain was not associated with any particular radiographic changes. In a series of retrieved modular Lord prostheses discoloration and dark deposits at the head-neck junction was found in 4 of 9 cases. Metallographic analysis of retrieved implants revealed material flaws close to the modular interfaces where severe corrosion had occurred. Bone and soft tissues at the implant site were similarly discoloured by corrosion products. Metal particles were often found in areas of extensive necrosis indicating a toxic reaction. Moreover, foreign-body granuloma and chronic inflammation were common findings, and in two cases we observed obliterative vascular changes similar to those previously described with metal-to-metal prostheses. Constituents of the alloys used in hip prostheses - notably chromium, nickel, and cobalt – are carcinogenic and there is concern over a possible association between total hip arthroplasty and cancer. Epidemiological data are scarce but two recent reports have indicated an increased incidence of lymphoma and leukaemia after hip replacement surgery. We studied the cancer incidence after hip arthroplasty in a cohort of 10,785 individuals operated in Stockholm County between 1974 and 1988, representing a total follow-up of 58,437 person-years at risk. The incidence of malignant tumors was not increased during the first decade after surgery.