What imaging should be obtained to evaluate suspected knee hardware breakage?

Imaging for Suspected Knee Hardware Breakage

Start with standard anteroposterior (AP) and lateral radiographs of the knee, ensuring the entire prosthesis is included on the images; these plain films are the initial and most appropriate imaging modality for evaluating suspected hardware breakage after total knee arthroplasty. 1

Initial Radiographic Evaluation

• Obtain weight-bearing AP and lateral views whenever possible, as weight-bearing films expose true alignment and can reveal subtle hardware displacement or fracture that may not be apparent on non-weight-bearing images 1, 2
• Include an axial (skyline) view of the patellofemoral joint to complete the standard three-view series and assess patellar component integrity 2
• Ensure the entire prosthesis is visible on all images, from the proximal extent of the femoral component to the distal extent of the tibial component 1

What Radiographs Can Detect

Plain radiographs effectively demonstrate:

• Hardware fracture or breakage (the primary concern in your clinical scenario) 1
• Abnormal bone or hardware alignment 1
• Periprosthetic fractures 1
• Evidence of polyethylene liner wear 1
• Cement fracture or displacement 1
• Periprosthetic lucency suggesting loosening 1

Advanced Imaging Techniques When Radiographs Are Equivocal

If plain radiographs do not clearly demonstrate hardware breakage but clinical suspicion remains high:

• Fluoroscopy can provide dynamic evaluation and allow optimal positioning to detect subtle hardware fractures or motion of prosthesis components 1
• CT with metal artifact reduction protocols is superior to radiographs for detecting radiographically occult fractures of bone or hardware, though beam-hardening artifact remains a limitation 1
• MRI with metal artifact suppression sequences may be considered for evaluating surrounding soft tissues (extensor mechanism, fluid collections) but is not the primary modality for hardware assessment 1, 3

Critical Pitfalls to Avoid

• Do not rely solely on a single radiographic view—hardware fractures may be visible in only one projection, making multiple orthogonal views essential 1, 2
• Do not skip weight-bearing films when the patient can tolerate them, as non-weight-bearing images may miss displacement or instability that becomes apparent under load 1, 2
• Do not proceed directly to advanced imaging without obtaining plain radiographs first; this violates evidence-based imaging algorithms and increases cost unnecessarily 1
• Ensure comparable positioning if comparing serial radiographs to assess for progressive hardware changes, as rotational differences can create false impressions of component shift 1, 4

When Hardware Breakage Is Confirmed

Once hardware fracture is identified on imaging:

• Immediate orthopedic referral is warranted, as hardware breakage typically requires revision surgery 1
• Serial radiographs are not appropriate for monitoring known hardware fractures—surgical intervention is the definitive management 1