In vitro simulation and quantification of wear within the patellofemoral joint replacement

Area of Science:

• Biomaterials Science
• Orthopedic Engineering
• Medical Device Development

Background:

• In vitro wear quantification is vital for joint replacement development.
• Limited research exists on simulating patellofemoral joint (PFJ) wear, despite high implantation rates.
• Over 200,000 PFJ replacements are performed annually in the EU.

Purpose of the Study:

• To develop and validate a novel in vitro method for simulating wear in the PFJ of total knee replacements (TKR).
• To compare in vitro wear simulation results with in vivo clinical outcomes.

Main Methods:

• A laboratory wear simulation method was developed using four input degrees of freedom for the PFJ in TKR.
• Wear simulation was validated by comparing functional kinematics and patellar surface damage modes to clinical outcomes.
• The technique's reproducibility and repeatability in replicating in vivo kinematics were assessed.

Main Results:

• The developed technique successfully replicated prescribed in vivo kinematics reproducibly.
• Wear scar areas observed in vitro were comparable to those found in vivo.
• Geometrical measurements of wear were unreliable due to creep and geometry changes, similar to findings with tibial inserts.

Conclusions:

• Gravimetric determination of volume change is the most repeatable and reliable measure for quantifying patellar wear in vitro.
• Geometrical measurements are not effective for comparing wear between simulators and retrieved implants.
• This validated method provides a reliable approach for in vitro PFJ wear simulation in TKR development.