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Orthopedic implant or hardware failure refers to the failure of the implant to live up to its expected requirements with respect to the manufacturer's or the surgeon's allegations. This includes any complication directly related to the implant such as wear, fractures, dissociations and dislocations due to material fatigue.
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Frequency and specific type of hardware failure are heavily dependant on the type of the implant, the implantation site, implant position, composition and geometry 1. It can range anywhere up to 20-40% in pubic symphyseal implants 3.
Predisposing factors for hardware failure include 2,4:
- implant or component malposition
- imbalance of tissue tension
- suboptimal surgical approach or implant design
Orthopedic hardware failure can be associated with the following conditions 1:
- component migration
- nonunion, delayed union
- particle disease (osteolysis)
Common signs and symptoms include pain and functional loss.
Hardware failure can lead to the following complications 1,4:
- periprosthetic fracture
- neurovascular injury
Causes of orthopedic implant failure include 4:
- primary material fatigue
- aseptic loosening
- periprosthetic infection/septic loosening
Orthopedic implant or hardware failure can be classified into the following conditions, some of the subtypes apply only for specific implants such as arthroplasty 4-7:
- implant fracture or dislocation
- implant deformation
- wear (e.g.polyethylene wear)
- component displacement/dislocation
- screw back-out
- inlay dislocation
Imaging features of hardware failure include the following:
- implant discontinuity or deformity
- implant displacement or migration
- reduced intermodular distances suggesting wear
An early radiographic sign associated with an increased risk of hardware failure is stress shielding.
Plain radiographs are usually used as a first-line imaging tool for the assessment of orthopedic hardware and can detect and visualize most types of hardware failure.
CT might be needed in certain locations (e.g. the spine), situations of uncertainty (e.g. component tilt) as a problem-solving tool or for the evaluation of associated complications such as neurovascular injury 2.
MRI is especially useful in the assessment of non-metallic orthopedic implants or for the assessment of the surrounding soft tissues and complications.
The radiological report should include the following:
- specification of the affected implant
- type of hardware failure
- fracture or deformity
- implant displacement or migration
- component migration, tilt or dislocation
- implant wear (e.g. polyethene wear, cement erosion)
- associated complications
Treatment and prognosis
Treatment includes revision and will mainly depend on the type of hardware failure, clinical symptoms and presence and/or risk of associated complications 1.
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