Biomechanical bases for tendon transfers at the shoulder

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Rehabilitation Medicine

Background:

• Shoulder muscle paralysis is a challenging condition leading to functional deficits and pain from glenohumeral subluxation.
• Effective management requires glenohumeral joint stabilization and restoration of active range of motion (external rotation, abduction, internal rotation).

Purpose of the Study:

• To outline the objectives for managing shoulder muscle paralysis, focusing on joint stability and functional restoration.
• To emphasize the importance of understanding muscle coordination and biomechanical principles before considering tendon transfers.

Main Methods:

• Review of biomechanical principles relevant to shoulder function and tendon transfers.
• Criteria for successful tendon transfers: similar line of pull, tension, and excursion to the native muscle.
• Requirement for a single tendon transfer to replace a single function and for the donor muscle to possess adequate strength (M4).

Main Results:

• Successful tendon transfers depend on matching biomechanical properties (moment arm, tension, excursion) of the donor tendon to the recipient muscle.
• A single tendon transfer should ideally restore one specific shoulder function.
• Donor muscle strength is a critical factor for successful functional restoration.

Conclusions:

• A thorough understanding of shoulder muscle coordination and biomechanics is essential for planning effective tendon transfers.
• Adherence to specific biomechanical and functional criteria ensures optimal outcomes for tendon transfer surgery in shoulder paralysis.