MicroStructured Omnifit acetabular components: concerns with locking system complications and excessive polyethylene...

Area of Science:

• Orthopedic surgery
• Biomaterials engineering
• Medical device analysis

Background:

• Cementless MicroStructured Omnifit acetabular components were introduced in 1988.
• Post-implantation observations revealed liner dislodging and excessive polyethylene wear.
• A review was initiated to assess the long-term performance of these modular components.

Purpose of the Study:

• To evaluate the incidence of locking system complications in cementless MicroStructured Omnifit acetabular components.
• To determine the influence of femoral head size on polyethylene wear rates.
• To identify factors contributing to excessive wear in total hip arthroplasty.

Main Methods:

• Radiographic examination of 887 hips (672 patients) implanted with cementless MicroStructured Omnifit acetabular components.
• Comparison of polyethylene wear between hips with 26-mm (group 1) and 32-mm (group 2) femoral heads using a digitiser.
• Analysis of locking system complications and polyethylene thickness.

Main Results:

• A 0.8% incidence of locking system complications was observed within a mean of 2.9 years.
• Mean annual liner wear rate was 0.15 mm (group 1) vs. 0.20 mm (group 2), with group 2 showing significantly higher wear (p < 0.005).
• Polyethylene thickness was significantly less in group 2 (3.9–10.6 mm) compared to group 1 (5.9–13.6 mm) (p < 0.005).

Conclusions:

• Patients with MicroStructured Omnifit acetabular components require regular monitoring for radiographic signs of locking system complications.
• The 32-mm femoral head group exhibited significantly higher polyethylene wear rates.
• Inadequate polyethylene thickness was identified as the primary cause of excessive wear in the larger femoral head group.