Total Knee Replacement with an Uncemented Porous Tantalum Tibia Component: A Failure Analysis

Area of Science:

• Orthopaedic Surgery
• Biomaterials Science
• Materials Engineering

Background:

• Porous tantalum is widely used in uncemented total knee arthroplasty (TKA) with earlier designs showing favorable outcomes.
• Evolution to modular implants aimed to improve TKA performance.
• This study investigates causes of medial tibia bone loss and subsequent modular porous tantalum tibia baseplate fracture after primary TKA.

Purpose of the Study:

• To analyze the causes of extensive medial tibia bone loss and modular porous tantalum tibia baseplate fracture.
• To investigate the role of metal debris and bone ingrowth in implant failure.

Main Methods:

• Proton-Induced X-ray Emission (micro-PIXE) elemental analysis of retrieved tissue samples.
• Stereomicroscopy for fractographic and microstructural analysis.
• 3D finite-element modeling for stress-strain analysis of the tibial baseplate.

Main Results:

• Histological examination revealed tantalum and titanium metal debris under the fractured baseplate.
• Fractographic analysis indicated the tibial baseplate failure met criteria for fatigue fracture.
• Bone ingrowth was observed on only 22.5% of the contact surface, particularly limited on the medial side.

Conclusions:

• Modular porous tantalum tibia baseplate fracture in TKA is likely due to fatigue.
• The presence of metal debris and limited bone ingrowth, especially medially, may contribute to bone resorption and catastrophic failure.
• Further research is required to confirm the link between metal debris, bone absorption, and tibial tray failure.