Relationship between joint motion and flexor tendon force in the canine forelimb

Area of Science:

• Orthopedics
• Biomedical Engineering
• Rehabilitation Science

Background:

• Flexor tendon repair requires careful management of passive motion to optimize healing and function.
• Understanding the biomechanical factors influencing tendon force is crucial for effective rehabilitation protocols.

Purpose of the Study:

• To investigate the relationship between wrist and digital position, muscle activation, and in vivo tendon force in a canine model.
• To determine the optimal joint positions for controlling tendon force during flexor tendon repair rehabilitation.

Main Methods:

• A canine model was used to measure flexor tendon force during various passive motion paradigms.
• Measurements included single-finger and four-finger flexion-extension with the wrist in flexed and extended positions.
• Tendon force was also measured during electrical stimulation of the flexor muscle mass.

Main Results:

• Passive tendon force was significantly higher (2-3 times) with the wrist extended compared to the wrist flexed, irrespective of the number of digits moved.
• Peak passive tendon force with the wrist extended reached 1,997 g, versus 853 g with the wrist flexed during single-digit manipulation.
• Active muscle force and passive tension varied dramatically with wrist position, decreasing significantly as the wrist moved from full extension to full flexion.

Conclusions:

• Wrist position is the dominant factor influencing flexor tendon force during common rehabilitation exercises.
• Minimizing tendon force for rehabilitation can be achieved with the wrist in a flexed position.
• Maximizing tendon force for rehabilitation can be achieved by incorporating greater wrist extension into exercise programs.