[Kinematic alignment-management of deformities and flexion contractures]

Area of Science:

• Orthopedic surgery
• Biomechanical engineering

Background:

• Kinematic alignment (KA) total knee arthroplasty (TKA) is a viable alternative to mechanical alignment (MA) TKA.
• KA-TKA faces challenges including flexion contracture and significant knee deformities.
• Addressing these challenges is crucial for successful KA-TKA outcomes.

Purpose of the Study:

• To discuss strategies for managing flexion contracture in KA-TKA.
• To outline approaches for handling large intra-articular and extra-articular knee deformities in KA-TKA.
• To ensure the validity and efficacy of the kinematic alignment technique.

Main Methods:

• Posterior capsular release is a common but often insufficient treatment for flexion contracture.
• Modifying distal femoral cuts or tibial cuts can lead to instability.
• A
• virtuous mistake
• strategy involves undercutting posterior femoral condyles by 2mm while adhering to KA guidelines.
• Distinguishing between intra-articular and extra-articular deformities guides treatment decisions.

Main Results:

• Proximalizing distal femoral cuts in MA-TKA for flexion contracture can cause mid-flex knee instability.
• Tibial cut adjustments and slope reduction in KA-TKA can achieve full extension but may cause 90° flexion instability.
• The "virtuous mistake" strategy aims to mitigate instability issues.
• Intra-articular deformities may allow for pure KA or modified tibial cuts.
• Extra-articular deformities necessitate osteotomies or combined procedures.

Conclusions:

• Careful management of flexion contracture and large deformities is essential for successful KA-TKA.
• The "virtuous mistake" strategy offers a solution for flexion contracture within KA principles.
• Specific surgical techniques are required for different types of knee deformities to optimize KA-TKA outcomes.