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A 70-year-old man with an uncemented metal-on-polyethylene total hip prosthesis underwent revision arthroplasty 33 months later because of pain, swelling and recurrent dislocation. There appeared to be corrosion and metal release from the prosthetic head, resulting in pseudotumour formation and severe local soft-tissue destruction. The corrosion occurred at the junction between the titanium-molybdenum-zirconium-iron taper and the cobalt-chrome-molybdenum head, but the mechanism was unproven.

One hundred fourteen total hip arthroplasties in 110 patients performed between 1979 and 1983 using the Lord femoral component were analyzed. Nine femoral revisions were performed within 13 years after surgery (two because of infection). Excluding infections there was a 94% 13-year survival according to a Kaplan-Meier analysis. Subsidence was seen in five hips (five patients), but only one needed revision surgery. Seventy-six hips (73 patients) had a radiographic followup of 10 years or more and were analyzed in detail. Changes in cortical thickness, density, and formation of spotwelds continued beyond 5 years after surgery, meaning the remodeling of periprosthetic bone continued beyond that time. Osteolysis on the femoral side was seen in seven hips, always in the proximal part of the femur, apparently as a continuation of the joint space. No remote focal osteolysis was seen. Elderly patients, women, and patients with a pedestal were overrepresented among individuals with many spotwelds. For the clinical outcome the Merle d'Aubigne and Postel score as modified by Charnley was used. Among 69 hips (66 patients) with a mean followup of 153 months 96% (66 hips) had a pain score equal to or greater than 4 and 74% (51 hips) had a score of 5 or 6. The Lord femoral component gave surprisingly good clinical long term results despite the bone remodeling (stress shielding), which in some cases was pronounced. The most obvious disadvantage with this design appears to be the difficulties associated with its removal when indicated.

Most reports of excellent long-term results of cemented total hip arthroplasty originate from studies of Charnley prostheses. A radiographic and clinical study was performed on 126 patients who underwent a cemented total hip arthroplasty from 1983 to 1985 with the Harris Design 2 prosthesis (Howmedica, Rutherford, NJ). The femoral component was cobalt-chromium and it had a broad, rounded medial border and a collar. The head diameter was 26 mm. A cemented all-polyethylene socket was used in all cases. At the last follow-up examination, 71% of the patients were completely free of pain and no patient had severe pain or pain at rest. Kaplan-Meier survival analysis estimated the revision rate at 10 years after operation to be 5 +/- 2% (mean +/- SEM) (including planned revisions). The rate of complete acetabular demarcation was 20% at 10 years, and femoral demarcation involving more than 50% of the bone-implant surface or endosteal cavitation was noted in only three cases. These results are as good as the best reported after total hip arthroplasty with the Charnley prosthesis.

We studied 70 patients after uncemented hip replacement with the Lord prosthesis which has a relatively long, completely macrotextured stem. The mean follow up was for 9.5 years. We compared radiographs at one year after operation, at 5 years and at the last follow up. Twenty-five patients (36%) had deep or circumferential pain in the thigh. Of the 44 who were most active at 5 years those with thigh pain had less proximal cortical loss than those without (p < 0.05), most cortical bone formation distally and most often had incomplete radiolucent lines at the mid-stem level, perhaps indicating more elastic displacement of the bone relative to the prosthesis. The presence of radiolucent lines correlated with the increase in cortical width at 5 years (p < 0.01). Cortical remodelling continued after 5 years at all levels except at the tip (p < 0.01). The relative elastic displacement at the interface could cause pain and may contribute to the pattern of bone remodelling in the femur after uncemented hip replacement.

The incidence of cancer after hip replacement was studied in the 1.6 million inhabitants of Stockholm County, Sweden. A cohort of 10,785 individuals who had had hip replacement between 1974 and 1988 was followed from the date of operation to the first malignant tumour, to death, or to the end of 1989. The follow-up was based on 58,437 person-years at risk as calculated from information obtained by record-linkage with the National Cancer Registry and the National Cause-of-Death Register. The Standardised Morbidity Ratio (SMR) for all cancer sites, disregarding the length of follow-up, was 0.96 (95% CI 0.90 to 1.03). For lymphoma and leukaemia the corresponding SMR was 0.89 (0.68 to 1.14). Our results do not support previous suggestions of an increased incidence of leukaemia and lymphoma after total hip replacement.

Restoration of femoral offset is an important part of total hip arthroplasty. Since radiographs showing the femur at a sufficient degree of internal rotation to allow direct measurement of femoral offset are not usually available, templates of the prosthesis at 25 and 45 degrees of rotation were created. Radiographs of 20 cadaver femurs with a mean offset of 44 +/- 5 mm (r 36-56) were then obtained at different degrees of rotation. Simple guidelines to indicate the correct template for each projection of the femur were found. The system could be used to select a prosthesis with correct offset using radiographs obtained at angles of rotation between 20 degrees internally and 40 degrees externally.

Nine uncemented hip prostheses of modular design were revised because of late infection (2 cases), femoral stem loosening or fracture (2), loosening of threaded cups (3) and protrusion of bipolar cups (2). At surgery we found tissue discoloration and macroscopic corrosion in four of the nine prostheses, located at the head-neck junction. Histological examination in most cases showed extensive necrosis associated with metal particles, indicating metal toxicity. Metallographic examination of the prosthetic heads revealed structural imperfections and inhomogeneity of the metal. We suggest that the crevice between the head and neck is a potential site of corrosion in modular designs.

The tissue reaction to implanted materials and their wear products is important for the long-term fixation of a total hip replacement (THR). Recent reports indicate a relatively high incidence of aseptic loosening with Christiansen total hip prostheses. We examined tissue reactions to wear products in two groups of prostheses: 16 Christiansen prostheses with polyacetal (Delrin) sockets, and 18 Charnley-Müller total hip prostheses with ultrahigh-molecular-weight polyethylene (UHMWP) sockets. Specimens from these 34 patients were compared in a combined qualitative and semiquantitative morphological study. We saw similar histological changes in specimens of both groups, but specimens from the bone-cement interfaces of the acetabulum and femur shaft in the polyacetal group showed more inflammation and necrosis.