Functional medical ligament balancing in total knee arthroplasty

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Biomedical Engineering

Background:

• Total knee arthroplasty (TKA) aims to restore knee function and alignment.
• Medial collateral ligament (MCL) release is sometimes necessary to correct varus deformity during posterior cruciate retaining TKA.
• The specific roles of MCL portions and posterior capsule in knee stability during TKA are not fully elucidated.

Purpose of the Study:

• To evaluate the functional contribution of the anterior and posterior oblique portions of the MCL and the posterior capsule in knee flexion and extension.
• To determine the effects of releasing these structures on knee laxity following posterior cruciate retaining TKA.
• To correlate in-vitro findings with clinical observations in patients undergoing TKA.

Main Methods:

• Eight cadaveric knee specimens underwent posterior cruciate retaining TKA.
• Subperiosteal release of either the posterior oblique or anterior MCL portion was performed in separate groups.
• Subsequent releases of the posterior capsule and complete MCL were conducted, assessing laxity at various flexion angles.

Main Results:

• Posterior oblique MCL release caused moderate laxity at extension and 30° flexion; posterior capsule release added further extension laxity.
• Anterior MCL release resulted in significant laxity at 60° and 90° flexion.
• Complete MCL release increased laxity in both flexion and extension. Clinical data showed specific releases effectively addressed varus deformity in 76% of cases.

Conclusions:

• Selective release of the posterior oblique MCL addresses extension tightness, while anterior MCL release targets flexion tightness in TKA.
• Posterior capsule release can further improve extension stability.
• These findings support tailored MCL and posterior capsule management for optimal varus deformity correction in TKA.