Development of an In Vitro Swan Neck Deformity Biomechanical Model

Area of Science:

• Orthopedic biomechanics
• Hand surgery research
• Cadaveric study models

Background:

• Swan neck deformity (SND) arises from extensor mechanism injury, causing tendon imbalance and impaired finger motion.
• Understanding the complex pathomechanics of SND is crucial for developing effective treatments.
• An in vitro model is needed to study SND's biomechanical effects and test interventions.

Purpose of the Study:

• To develop an in vitro model for studying swan neck deformity (SND).
• To investigate the biomechanical changes associated with induced SND.
• To evaluate volar plate strain as a measure of SND and its potential for assessing surgical outcomes.

Main Methods:

• Utilized an in vitro active motion simulator with cadaveric finger specimens.
• Created an SND model by sectioning the terminal extensor tendon and transverse retinacular ligament (TRL).
• Measured volar plate strain and proximal interphalangeal joint (PIPJ) angles during simulated motion.

Main Results:

• Volar plate strain significantly increased with the development of mallet finger and SND conditions.
• Sectioning the TRL contributed more to the strain increase than the mallet finger condition.
• PIPJ angle strongly correlated with volar plate strain, serving as a surrogate for hyperextension.

Conclusions:

• In vitro measurement of volar plate strain can detect induced swan neck deformity (SND).
• Volar plate strain serves as a reliable indicator of PIPJ hyperextension in the SND model.
• This method offers a valuable tool for evaluating the immediate effectiveness of surgical interventions for SND.