Tendon Transfer - Principles

Definition

• A tendon transfer is a procedure in which the tendon of insertion or of origin of the functioning muscle is mobilised, detached or divided and reinserted into a bony part or onto another tendon, to supplement or substitute for the action of the recipient tendon

Indications for tendon transfers

1. Irreparable nerve damage

2. Loss of function of a musculotendinous unit due to trauma or disease

3. In some nonprogressive or slowly progressive neurological disorders

Basic principles of tendon transfer

1. Mobile Joints / Correction of joint, skin and soft tissue contractures

• If necessary, capsulotomy, or free flap may be necessary prior to tendon transfer

 2. Adequate power of transferred tendon

• Power of a muscle is determined by its cross sectional area

• Only muscles with power of 4+ should be considered donors as they always lose 1 MRC grade of power

 3. Sufficient amplitude (excursion / freedom of movement) in the transferred  tendon

• The amplitude of a muscle is a function of the sarcomere length

• It is a fixed value for any muscle, but can be increased by

• Freeing the muscle from its fascial attachments

• Changing a muscle from monoarticular to  biarticular, the amplitude is increased by  movement of the  extra joint that the tendon crosses

• Amplitude can be limited by scarring and adhesions

• As a guide, amplitudes are as follows

  • Wrist motors     33mm

  • Finger extensors            50mm

  • Finger flexors     70mm