· tendon transected and reinserted into bone or another tendon
· its muscle and the muscle's blood and nerve supply are preserved
· substitution for function of paralysed muscle
· nerve injury
· neurological disease
· replacement of ruptured or avulsed tendons or muscles
· rheumatoid arthritis
· restoration of balance to a deformed hand
· cerebral palsy
· other CNS disorders
· all inflammation and swelling subsided
· joint contractures freed by appropriate operative and nonoperative interventions
· stable bony framework established
· bed for tendon is supple and soft
· free skin grafts and hypertrophic scar not suitable
· silicone rod may prepare smooth bed
Calculated
· donor must be sufficiently strong to perform new function in altered position
· muscles will usually use one grade of strength when transferred
· relative strengths have been calculated
· BR, FCU 2
· FR, ECRL, ECRB, ECU, PT, FPL, FDS, FDP 1 (each tendon)
· EDC, EIP, EDQ 0.5 (each tendon)
· interossei 2.7 (combined)
· lumbricals 0.5 (combined)
Current
· current condition of muscle very important
· should not be used for transfer unless at least 85% of normal power
· if possible, avoid use of muscles that have been reinnervated
Considerations
Function of transfer
· tendon may be for grasp or positioning
· if for grasp, greater strength needed
Strength of antagonist
· must balance potential force on either side of paralysed digit to avoid overcorrection
Mobility of joints
· must take care to avoid overcorrection if joint hypermobile (congenital laxity, prolonged paralysis)
Measured
· amplitude related to resting length
· greatest potential force of contraction occurs at resting length
· practical values for excursions are
· wrist flexors and extensors 35 mm
· finger extensors and EPL 50 mm
· finger flexors 70 mm
Effective
· can increase effective amplitude in two ways
Joints
· can change position of intercalary joints over which tendon passes
· if wrist flexor is transferred to a finger flexor, good function can be achieved if wrist mobile
· deficit in amplitude made up by tenodesis effect when wrist dorsiflexed
· wrist motion increases amplitude by 25-30 mm
Dissection
· can free soft tissues that limit muscle contraction
· can increase amplitude of brachioradialis from 40 mm to 80 mm by freeing fascia that surrounds it
· tendon transfer should pass in straight line from origin to insertion
· not always possible but should be aimed for
· if must change direction, should pass through stable, smooth and ample pulley
· when donor tendon transferred to recipient tendon, recipient tendon should be sectioned proximal to site of suture
· to prevent diversion of direction of transfer
· tendon transfer should only have one function
· may be inserted into more than one recipient
· eg FCU to all finger extensors
· should not expect tendon transfer to perform two dissimilar functions even if not direct opposites
· controversial whether synergistic muscles should be chosen as donors
· synergistic muscles do not always work togther and antagonistic muscles may work together
· brain chooses appropriate muscles for function and can recruit substitutes
· muscles will contract appropriately to their new position within 1 day of surgery
· removal of tendon for transfer must not result in unacceptable loss of function
What works ?
· make list of all muscles with power grading of fair, good or excellent
What is available ?
· make list of working muscles that may be transferred without functional loss
What is needed ?
· make list of functions needed
Matching
· match available muscles and needed functions based on above principles
Alternatives
· if all desired functions cannot be achieved, consider
· capsulodesis
· tenodesis
· arthrodesis
· pulley release
Staging
· divide procedures into three stages
· transfers on flexor side of hand
· transfers on extensor side of hand
· transfers passing both volar and dorsal to joints of hand