Between 1981 and 1986 two groups of patients received either Charnley low-friction arthroplasties or the Wrightington Frusto-Conical hip replacement with otherwise identical management before and after operation. There were 260 consecutive replacements in 215 patients in the first group and 260 consecutive procedures in 211 patients in the second. Both components of each design were cemented and featured a 22.25 mm femoral head, but the geometry of the stems differed.

Of the patients lost to follow-up, 16 (18 hips) were in the Wrightington series and 24 (36 hips) in the Charnley series, and of those who have died 20 (23 hips) were Wrightington and 14 (16 hips) were Charnley. All surviving patients have been followed up clinically and radiologically or until revision was necessary. The mean length of follow-up for original surviving components in both series was 140 months (120 to 180).

Pain, function and movement were measured by the grading system of Merle D’Aubign′e and Postel and showed a marked improvement in both groups. There was little or no pain in 98% of patients in the Wrightington series and 96% in the Charnley series, while 93% and 85%, respectively, were entirely painfree. Trochanteric osteotomy was used in 292 cases overall, with a complication rate of 13% due to wire breakage, trochanteric bursitis or trochanteric detachment, requiring a further operation in 5.8% (17 hips). Heterotopic ossification was seen in 40% of cases in which trochanteric osteotomy had been performed (117 hips) but only 3% (10 hips) had clinically significant changes. After the direct lateral approach heterotopic ossification was seen in 24% (42 hips) with only 2% in class 3 or 4 (4 hips). Femoral osteolysis was more common in the Charnley series, occurring in 7.6% of cases (17 hips) as opposed to 2.1% (5 hips) in the Wrightington series.

Ten acetabular and seven femoral components have been revised in the Wrightington series and 16 acetabular and 11 femoral implants in the Charnley series. Survivorship based on revision for aseptic loosening using the Kaplan-Meier technique showed survival of the femoral implant at 5, 10 and 15 years of 100%, 99% and 98%, respectively in the Wrightington and 100%, 99% and 87% in the Charnley series. The survival of the acetabular component at 10, 12 and 15 years respectively, was 100%, 99% and 95% for the Wrightington, and 99%, 98% and 84% for the Charnley.

The survival of both the acetabular and femoral components of the Wrightington system at a mean of 11.7 years was better than that of the Charnley system, with a lower incidence of radiological loosening of unrevised components.