Abstract
BACKGROUND
We originally performed metal-on-metal hip resurfacing using a Townley designed Vitallium Total Articular Replacement Arthroplasty (TARA) curved stemmed prosthesis. Neither the acetabular or femoral components were cemented or had porous coating. The bearing surfaces were consistently polar bearing. The surgical objectives were to preserve bone stock, maintain normal anatomy and mechanics of the hip joint and to approximate the normal stress transmission to the supporting femoral bone. The functional objectives were better sports participation, less thigh pain and limp, less perception of a leg length difference and a greater perception of a normal hip. Metal-on-metal was selected to conserve acetabular bone and avoid polyethylene associated osteolysis.
Relatively few cases were performed until the Conserve Plus and later the Birmingham Hip Resurfacing systems became available.
METHODS
We examined the results of metal-on-metal hip resurfacing in patient with at least 10 years of follow-up and an age less than 50 at the time of surgery. We did not have access to the Birmingham Prosthesis until 2006. We performed 101 TARA procedures and 397 Conserve Plus procedures for 357 patients. For the combined series the mean age was 43 and 62% of patients were male. 34 patients had a conventional total hip replacement on the contralateral side. We used both the anterolateral and posterior approaches. All acetabular components were placed without cement and all the Conserve Plus Femoral Components were cemented.
RESULTS
There were no implant related failures with the TARA prosthesis. The average Harris Hip Score was 93. There were 2 revisions for femoral neck fracture at years 8 and 14 and one revision for infection. There was one dislocation but no instance of implant loosening.
There were 29 (7%) revisions with the Conserve Plus Prosthesis. 14 revisions were for adverse reactions to metal wear debris and 10 of these patients had femoral components of size 46 mm or smaller. There were 5 revisions for acetabular loosening and 3 for femoral loosening. There were 7 revisions for femoral neck fracture and infection. The limb lengths were measured to be within 1 cm of equal in 98% of patients. 95% of patients had a UCLA activity score above 6 and 96% of patients rated their outcome excellent or good. 32 of 34 patients preferred their hip resurfacing to total hip replacement.
The Kaplan-Meier survivorship was 93%. Narrowing of the femoral neck was seen in 9% of patients but acetabular osteolysis was not seen. Signs of impingement of the femoral neck against the acetabular prosthesis were seen in 14% of patients.
CONCLUSIONS
Metal-on-metal hip resurfacing has been performed for more than 40 years using predicate prostheses such as the Townley TARA. The results of metal-on-metal resurfacing are favorable even in young and very active individuals. There were no instances of medical illness related to metal-on-metal implants with up to 41 years of follow-up. Metal-on-metal hip resurfacing has favorable outcomes at 10 years. There is an increased chance of an adverse reaction to metal wear debris with femoral component sizes 46 mm or smaller.
