THE ASRTM HIP SURFACE REPLACEMENT. PROSPECTIVE CONSECUTIVE MULTICENTRE STUDY OF 1030 HIPS AT 0–4 YEARS

Abstract

Introduction: The DePuy ASRTM hip resurfacing system has been in clinical use since 2003. Its design features include a diametral clearance of 100–150 microns for optimal wear, and thinner components for improved bone preservation. Three of the six designer surgeons have pooled their clinical experience from three countries.

Methods: 1030 consecutive cases have been studied prospectively at annual intervals,. There were 379 females (average age 56.8 years, 16–71 years) and 579 males (average age 56.9 years, 21–75 years). 86% of patients had a primary diagnosis of Osteoarthritis. Follow up data has been collected by patient questionnaire, radiographs and clinical review. All retrieved specimens have been analysed

Results: The size of implants used varied from 46mm outside diameter acetabular component to 70mm

The Harris Hip Score improved from a pre-operative mean of 56.99 to 97.12 at the latest follow up, and 60% of patients were scored at 100. At the latest follow up, 91% of patients scored 6 or above on the UCLA activity score; indicating at least regular participation in moderate exercise.

There were no dislocations and no clinically evident DVT’s or PE’s

There have been 11 revisions for fracture (1.06%). Five of these were intra-operative fractures, and six of these took place in patients aged over 50years. Fractures occurred in 3.1% of patients 65 years or more and in 0.5% of patients under 65 years(P< 0.05). In addition there were three revisions for cup loosening (0.29%) all in women over 60 years, three for unexplained pain (0.29%), one for impingement and subluxation, and one for infection(0.1%) Five patients have died with the resurfacing in situ (0.51%), for unrelated causes.

The 3-year cumulative survival rate for all patients and all components was 97.4%. For 425 patients under 55 years the cumulative survival rate was 99.4%, aged under 65 years was 98.3%, and aged over 65 yrs was 94.8 %.

Discussion: Clinical results of this all-inclusive cohort of patients using a new resurfacing implant have been typical of other resurfacing systems and confirm excellent relief of pain and rapid return to an active lifestyle. The failures were evident within the first year after implantation, with no revisions occurring after 2 years. Cup loosening has been a rare complication associated with older females and only 0.29% of patients have undergone revision surgery for pain which could not be attributed to implant loosening or infection.