Patellar prosthesis positioning in total knee arthroplasty. A roentgenographic study

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Prosthetics and Implants

Background:

• Accurate patellar prosthesis positioning is crucial for successful total knee replacement (TKR) outcomes.
• Traditional patellar button prostheses may present challenges in achieving optimal alignment and tilt.
• Novel implant designs and instrumentation aim to enhance patellar component placement.

Purpose of the Study:

• To evaluate and compare the positioning accuracy of two different patellar prosthesis designs in primary TKR.
• To assess parameters including patellar tilt, component-bone angle, placement, and size relative to bony remnant.
• To determine if a new biconvex prosthesis with specialized instrumentation improves patellar positioning over conventional methods.

Main Methods:

• A comparative study involving 40 primary total knee replacements, divided into two groups (n=20 each).
• Group A: Patellar button prosthesis with conventional surgical technique.
• Group B: New biconvex prosthesis with specially designed instrumentation.
• Evaluation of patellar tilt, component-bone angle, medial/lateral placement, patellar height, and component size.

Main Results:

• Group B demonstrated significantly improved patellar tilt (1.83° postoperative) compared to Group A (8.35° postoperative).
• A higher proportion of patients in Group B achieved normal patellar tilt and component-bone angles (1.447° average).
• Fewer instances of medial prosthesis placement were observed in Group B (1 patient) versus Group A (6 patients).
• Both groups showed decreased patellar height and increased postoperative articular length, suggesting oversized components or bone removal.

Conclusions:

• The novel biconvex patellar prosthesis, when used with specialized instrumentation, significantly enhances patellar positioning accuracy in TKR.
• This improved alignment may lead to better functional outcomes and reduced risk of complications associated with malpositioned components.
• Further investigation into component sizing and bone preparation techniques is warranted for both prosthesis designs.