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Proximal component modularity in THA--at what cost? An implant retrieval study
1Department of Medical Engineering and Physics, Royal Perth Hospital, Wellington Street, Perth, 6000, Western Australia, Australia.
Clinical Orthopaedics and Related Research
|November 4, 2011
Summary
The second neck-stem junction in total hip arthroplasty (THA) can degrade through corrosion and fretting, potentially leading to revision surgery. Titanium alloys may reduce degradation but risk cold welding.
Area of Science:
- Orthopedic Surgery
- Biomaterials Science
- Failure Analysis
Background:
- Modular femoral heads are standard in total hip arthroplasty (THA).
- A novel feature is the secondary neck-stem taper junction, offering surgical flexibility.
- Concerns exist regarding catastrophic fracture, cold welding, and junctional corrosion/fretting.
Purpose of the Study:
- To investigate degradation mechanisms at the neck-stem junction compared to the head-neck junction.
- To determine if the neck-stem junction contributes to THA revision.
- To assess the influence of alloy type and trunnion finish on degradation.
Main Methods:
- Analysis of 57 retrieved modular hip implants across seven designs.
- Comparison of cobalt-chromium-molybdenum and titanium-based components.
- Utilized macroscopic inspection, microscopy, and micro-computed tomography (micro-CT).
Main Results:
- Cobalt-chromium-molybdenum components exhibited crevice corrosion and fretting at the neck-stem taper.
- Titanium components showed reduced corrosion but presented cases of intractable cold welding.
- Degradation at the second junction was linked to metallosis and aseptic lymphocyte-laminated vascular-associated lesions.
Conclusions:
- Corrosion, fretting, and debris generation are significant issues at the second neck-stem junction, even with advanced materials.
- Titanium alloys may mitigate some degradation but introduce the risk of cold welding.
- Neck-stem junction degradation contributed to THA revisions due to adverse tissue reactions.
