Frontal plane alignment after total knee arthroplasty using patient-specific instruments.

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering

Background:

• Total knee arthroplasty (TKA) aims for optimal patient outcomes, with neutral postoperative mechanical axis alignment being a key goal.
• Achieving precise alignment is crucial for TKA longevity and function.
• Patient-specific instrumentation (PSI) has emerged as a technology to enhance surgical precision.

Purpose of the Study:

• To evaluate the effectiveness of PSI in achieving a neutral hip-knee-ankle angle (HKA) within ±3° of 180° post-TKA.
• To assess the accuracy of PSI in aligning the mechanical axis relative to the tibial base plate.

Main Methods:

• Retrospective analysis of 124 TKAs performed using PSI technology.
• Long-leg X-rays were used to measure the hip-knee-ankle angle (HKA) and analyze the zone of the mechanical axis (ZMA).
• Follow-up was conducted at an average of 3.5 months post-surgery.

Main Results:

• The average HKA improved from 175.5° preoperatively to 178.5° postoperatively.
• 11% of cases were outliers for ±3° HKA, and 3% for ±5° HKA.
• The mechanical axis passed through the central third of the tibial base plate in 93% of cases, with no intra-operative complications.

Conclusions:

• PSI technology facilitates the achievement of an average neutral mechanical axis in TKA patients.
• The study demonstrates PSI's potential for accurate limb alignment during TKA.
• Further long-term follow-up is necessary to confirm the sustained benefits of PSI-guided TKA.