Comparison between a Constrained Condylar and a Rotating Hinge in revision knee surgery

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Medical Device Technology

Background:

• Total knee replacement (TKR) aims to restore function and alleviate pain in patients with severe knee joint damage.
• Constrained Condylar and Rotating Hinge prostheses represent different design philosophies for TKR, particularly in managing instability.
• Evaluating the comparative performance of these TKR designs is crucial for optimizing patient outcomes.

Purpose of the Study:

• To compare the mechanical performance, clinical outcomes, and radiographic findings of Constrained Condylar and Rotating Hinge total knee replacements.
• To assess the stability and functional restoration provided by each TKR type.

Main Methods:

• Mechanical testing to evaluate varus strength and rotational stability.
• Knee Society Clinical and Radiographic evaluations for objective assessment.
• Self-assessment questionnaires for patient-reported outcomes.

Main Results:

• Rotating Hinges exhibited minimal varus rotation, indicating superior stability compared to Constrained Condylars (≥6 degrees varus rotation).
• Constrained Condylars showed greater variation in femoral-tibial angles and suboptimal valgus angles due to shorter stems.
• Patient self-assessments revealed a high correlation between operated and non-operated knees in the Rotating Hinge group, suggesting better functional adaptation.

Conclusions:

• Rotating Hinge total knee replacement offers enhanced stability and clinical results, potentially due to its ability to adapt to patient needs.
• Constrained Condylar designs may lead to greater instability and variability in alignment.
• Rotating Hinges warrant greater consideration, provided challenges like increased bone resection and longer stems can be mitigated.