The effect of total knee design on patellar strain

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Biomaterials science

Background:

• Total knee arthroplasty (TKA) is a common procedure for end-stage knee osteoarthritis.
• Patellar resurfacing is frequently performed during TKA, but its effect on patellar biomechanics remains a concern.
• Understanding anterior patellar strain is crucial for optimizing implant design and surgical techniques to improve long-term outcomes.

Purpose of the Study:

• To quantify anterior patellar strain following total knee arthroplasty with patellar resurfacing.
• To investigate the influence of surgical capsulotomy and flexion angle on patellar strain.
• To compare patellar strain across different TKA prosthesis designs.

Main Methods:

• Utilized a biomechanical model to measure anterior patellar strain in cadaveric knees undergoing TKA with patellar resurfacing.
• Assessed strain at various flexion angles (0-90 degrees) with and without surgical capsulotomy.
• Compared strain measurements between the Total Condylar, Insall-Burstein, and Robert Brigham prosthesis designs.

Main Results:

• Total knee arthroplasty with patellar resurfacing increased anterior patellar strain up to three times that of controls.
• This increase was independent of surgical capsulotomy and became prominent at flexion angles >30 degrees.
• The Total Condylar prosthesis exhibited the highest strains, while the Insall-Burstein showed higher strains than the Robert Brigham prosthesis.

Conclusions:

• Patellar resurfacing in TKA significantly elevates anterior patellar strain, especially in deeper flexion.
• Prosthesis design, specifically the Total Condylar, may influence the magnitude of this strain.
• Further research is warranted to correlate these biomechanical findings with clinical outcomes and implant longevity.