Tibial morphological difference between metal augmentation and actual tibia for revision total knee arthroplasty

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Anatomy

Background:

• Tibial component overhang/underhang in knee arthroplasty can lead to soft tissue irritation or bone resorption.
• The tapering angles of existing metal augmentation blocks may not align with the natural proximal tibial contour.
• Understanding tibial morphology is crucial for optimizing implant fit and function.

Purpose of the Study:

• To analyze the bony contour of the proximal tibia.
• To measure the tapering angle of the proximal tibia across different resection levels.
• To compare the native tibial tapering angle with that of currently available metal augmentation blocks.

Main Methods:

• Computed tomography (CT) scans of 100 lower extremities were used to create 3D tibial models.
• Tapering angles were calculated based on projected bone surfaces at 5, 10, 15, and 20 mm below the primary resection level.
• Measurements were compared to the angles of commercially available metal augmentation implants, and mismatch distances were quantified.

Main Results:

• Tibial tapering angles increased with distal resection, reaching up to 30° medially/laterally and 40° posteriorly at 20 mm.
• The tapering angle of current implants was consistently smaller than the native tibial morphology.
• Significant distances of mismatch, up to 11.3 mm, were observed between implants and bone surfaces.

Conclusions:

• Existing metal augmentation block designs do not accurately reflect the native proximal tibial morphology.
• A notable size mismatch exists between current implants and the tibia, particularly during revision total knee arthroplasty (TKA).
• Surgeons need to be vigilant about component fit to mitigate risks associated with revision TKA.