Late complications after total hip arthroplasty

The present study concerns late complications after total hip arthroplasty inrelation to implant material, design, and mode of implant fixation. Frictional characteristics inretrieved and new acetabular sockets was studied under dry and lubricated conditionscomparing conventional polyethylene sockets with polyacetal sockets from the Christiansenprosthesis. No difference between new sockets of the two materials was found, whereas thefriction in 12 retrieved polyacetal sockets was significantly higher than in 6 new and 6 retrievedpolyethylene sockets. The annual average wear of 12 retrieved polyacetal cups was 240 + 50mm3Periprosthetic tissue samples from 18 patients with polyethylene and 16 with polyacetal socketswere assessed in a comparative morphological study showing significantly more inflammationand necrosis in the polyacetal group. Polyacetal wear particles were smaller (l-loµ) than thosefrom 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 nearly10 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 asadaptive bone remodelling, progressed throughout the period of observation. Physically activepatients with thigh pain had less proximal bone loss than less active ones. New bone formationwas associated with radiolucencies at the mid-stem level indicating that the elastic relativedisplacement may contlibute to the pattern of bone remodelling seen with bulky uncementedimplants. 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 revealedmaterial flaws close to the modular interfaces where severe corrosion had occurred. Bone andsoft tissues at the implant site were similarly discoloured by corrosion products. Metalpalticles were often found in areas ol extensive necrosis indicating a toxic reaction. Moreover,foreign-body granuloma and chronic inflammation were common findings, and in two caseswe 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 - arecarcinogenic and there is concern over a possible association between total hip arthroplasty andcancer. Epidemiological data are scarce but two recent reports have indicated an increasedincidence of lymphoma and leukaemia after hip replacement surgery.We studied the cancer incidence after hip arthroplasty in a coholt of 10,785 individuals operatedin Stockholm County between 1974 and 1988, representing a total follow-up of58,437 person-years at risk. The incidence of malignant tumors was not increased during thefirst decade after surgcry