Lateral stability of the proximal interphalangeal joint

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Hand Surgery

Background:

• Current diagnostic criteria and therapeutic guidelines for proximal interphalangeal (PIP) joint collateral ligament injuries are imprecise.
• The lateral collateral ligament (LCL) is crucial for stabilizing the PIP joint against angular deformities.

Purpose of the Study:

• To analyze the biomechanical properties and failure patterns of the lateral collateral ligament (LCL) in the proximal interphalangeal (PIP) joint.
• To establish clearer diagnostic criteria for LCL injuries based on stress testing.

Main Methods:

• Performed laxity determinations, failure analysis, radiographic stress testing, and microscopic dissections on 112 PIP joints.
• Investigated the primary restraint function of the LCL against varus and valgus angulation.

Main Results:

• The LCL is the primary restraint to varus and valgus angulation; failure typically initiates in the palmar fibers proximally.
• Lateral stress tests indicating >20 degrees of angulation suggest complete LCL disruption.
• Tests with <20 degrees angulation show a 53% chance of partial and 47% chance of complete LCL failure, with connective tissues potentially maintaining alignment.

Conclusions:

• The study elucidates the biomechanical behavior and failure sequence of the PIP joint's LCL.
• Refined stress test interpretations can aid in diagnosing the extent of LCL injuries.
• Further clinical investigation is needed to define surgical intervention criteria for these injuries.