Long-term behaviour of the Charnley offset-bore acetabular cup

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Radiology

Background:

• Total hip arthroplasty (THA) is a common procedure for hip joint issues.
• Acetabular socket design significantly impacts THA longevity and patient outcomes.
• The Charnley offset-bore acetabular socket is a specific design used in THA.

Purpose of the Study:

• To evaluate the long-term radiological outcomes of the Charnley offset-bore acetabular socket in total hip arthroplasty.
• To assess wear, radiolucent lines, and migration of this specific acetabular socket design.
• To determine the revision rate and identify reasons for revision in patients who received this implant.

Main Methods:

• Radiological assessment of 58 total hip arthroplasties (THA) using the Charnley offset-bore acetabular socket.
• Measurement of polyethylene wear at four defined sites.
• Recording of radiolucent lines and assessment of component migration.
• Analysis of four retrieved acetabular cups using microscopy and X-ray microanalysis.

Main Results:

• Mean wear in DeLee and Charnley zone I was 0.4 mm and zone II was 0.26 mm at a mean seven-year follow-up.
• Wear rates were 0.06 mm/year (zone I) and 0.04 mm/year (zone II).
• Radiolucent lines progressed in 8.6% of cases; 5.2% of sockets were revised for aseptic migration, and one for infection.

Conclusions:

• The Charnley offset-bore acetabular cup demonstrates excellent wear characteristics and a low rate of migration and revision.
• Its performance supports its consideration in total hip arthroplasty, particularly given the increasing use of smaller cups in revision procedures.