1. Principles of Tendon Transfers

2. What is a tendon transfer? The tendon of a functioning muscle is detached from itsinsertion and reattached to another tendon or bone toreplace the function of a paralysed muscle or injured tendon.The transferred tendon remains attached to its parent musclewith an intact neurovascular pedicle. Or Using the power of a functioning muscle unit to activate anon functioning nerve/muscle/tendon unit. Tendon transfers work to correct instability, imbalance, lackof co-ordination and restore function by redistributingremaining muscular forces 3. Indications Paralysed muscle Nerve injury peripheral or brachial plexus High cervical quadriplegia (needs some input to brachial plexus/hand) Neurological disease Nerve repair with early transfer as internal splint Injured (ruptured or avulsed) tendon or muscle ConsiderationsGraft vs. transfer (adhesions more likely in graft 2 anastomoses)Quality of available donorsLength of time since injuryNature of tendon bed Balancing deformed hand e.g. cerebral palsy or rheumatoid arthritis Some congenital abnormalities 4. General principles1. Only justified in restoring functional motion of the hand, not just motion Not all patients require the same functions/motions2. Patient factors Age Functional disabilities with poor non operative prognosis Ability to understand nature and limitations of surgery, including aesthetic goals Motivated to co-operate with post operative physiotherapy3. Recipient site Tissue Equilibrium concept as per Steindler/Boyes Tissue bed into which transfer is placed should be soft and supple Good soft tissue coverage Stable underlying skeleton Full passive range of motion of joints to be powered Area to be powered must be sensate 5. 4. Donor muscle factors (APOSLE)Amplitude of the donor muscleShould be matched to the unit being replacedFinger flexors 60 - 70mm, finger extensors and EPL 40 - 50mm, wrist flexors / extensors 30 - 40mm, brachioradialis 20 - 30mmAmplitude of motion of any tendon can be increased by :-Increasing the number of joints its crosses eg the amplitude of a tendon crossing the wrist joint is increased by 20 30mm by full ROM of wristTenodesis effect during active movementFreeing fascial attachments to donor tendonsInserting the tendon closer to the joint being moved, but this requires a motor unit of increased power (due to leverage); and vice versaPower of the donor muscleAny transferred muscle loses at least one grade of strength, so only Grade 5 muscles are satisfactory (Grade 4, or 85% normal strength, can be sufficient for some transfers). Donor muscle strength should be maximised pre- operatively.Strongest are brachioradialis and FCU. Donor power correlated roughly with cross sectional area of muscle and fibre lengthOverly powerful muscles will unbalance and, over time, deform a joint. So muscle power should be matched if possible.Effective power of a transfer can be increased by placing the tendon insertion farther from the joint axis and as close to 90 as possibleBrachioradialis does not adapt well to transferred functionsOne tendon, One functionEffectiveness reduced in transfer designed to produce multiple functionsSynergistic muscle groups are generally easier to retrainFist group wrist extensors, finger flexors, digital adductors, thumb flexors, forearm pronators, intrinsicsOpen hand group wrist flexors, finger extensors, digital abductors, forearm supinatorsUse of synergistic muscles tends to help retain joint balanceLine of transferShould approximate pull of original tendon if possibleAcute angles should be avoidedExpendabilityTransfer must not cause loss of an essential function 6. 5. Other muscle factors of secondary importanceInnervation - Donor muscle should be independently innervated and not act in concert with other motors (eg lumbricals)Availability or necessity of antagonists eg brachioradialis is an effective wrist extensor only if triceps is functioning to resist its normal elbow flexor action6. Tension of the transferAll transfers should be sutured at the maximum tension in the position that reverses their proposed activity (Listers 4th Edn)7. Location and nature of pulley if required8. Selected arthrodesesSimplify polyarticular systemStabilise joints Radiocarpal arthrodesis in combined nerve lesions Thumb CMC in adducted thumb unable to be stabilised by transfers eg cerebral palsy, quadriplegia, combined nerve injury Glenohumeral arthrodesis in upper truck brachial plexus palsyArthrodeses useful in providing stable pinch grip Thumb MPJ and IPJ Index PIPJ and DIPJ 7. 9. TimingThe timing of tendon transfers depends upon the aetiology and prognosis of motor imbalance, the neurophysiologic problems for the patient, and the constitution of the involved extremity (Omer GE: Timing of tendon transfers to the hand. Hand Clin 4(2):317, 1988)Usually last stage in reconstruction, after skeletal stability, soft tissue coverage, sensation and joint mobilityEarly transfers are appropriate in problems that are expected to deteriorate with time eg opponensplasty to prevent predictable supination/adduction deformity in poor prognosis median nerve injury10. Comparison to alternativesNerve repair or transferTendon repair or graftTenodesis (joint stabilisation by anchoring tendons that move the joint)ArthrodesisAmputationMuscle lengthening, release or denervation (in spasticity)11. ContraindicationsAge due to joint stiffness, decreased need for power movements and difficult rehabilitationMotivation patients must be concerned about disability and highly motivated to perform hand rehabilitationTask analysis transfers must be designed to accomplish tasks rather than just specific motions. Eg opening doors requires grasp and twistNature of disability systemic and local disease factors must be controlled before reconstruction attempted12. DisadvantagesNo increase in strengthNormal function of transferred muscle is lostTransferred tendon may perform a different force, amplitude of movement and functional patternTransferred tendon must learn a new movement/function 8. Selecting donor tendons Based on Smith & Hastings (Principles of tendon transfers to the hand. Instr Course Lect 29:129, 1980)1. List functioning muscles2. List which of those muscles are expendable3. List hand functions requiring restoration4. Match #2 and #35. Staging 9. Example of planning tendon transfers in complex upper extremity palsiesWorkingAvailable NeededBR BRThumb flexionPT PTFinger extension Thumb extensionECRL ECRLFinger flexionECRBECUECU and graft MP flexion / IP extension (intrinsics)FCU (fair) FCU (fair)Thumb oppositionFCRPQ PP Thumb adductionStage 1: BR to FPL, ECRL to FDP, FCU to EPB for thumb oppositionStage 2: PT to EPL & EDC, thumb IP arthrodesisStage 3: ECU + plantaris graft to lateral bands of index to little fingers (routed volar to deep transverse metacarpalligament) 10. Maximising Success / Surgical Technique1. Incisions should not cross the path of the transferred tendon2. Avoid interference with normal structures3. Tendon should insert into the joint of motion at 90 to maximise power and excursion. Insertion can be moved away from the joint to improve power, but this is at the expense of decreased excursion4. The transferred tendon should insert into another tendon or bone. Strong insertions allow earlier mobilisation.5. A single insertion is best. Dual insertions tend to provide motion to the tighter insertion. Can be an advantage in complex movements, where one insertion is tighter during one phase of motion, and the other takes over during another phase.6. Tension should be set to produce the necessary joint movement with maximal muscle contraction. Some initial over correction should be planned, as some tendon stretch is usual.7. Joint should be initially immobilised in a position that relieves tension at the insertion of the transfer8. Reverse order harvest grafts, prepare recipient site and tunnel before raising muscle 11. General Post Operative Management Rehabilitation is equally important in tendon transfer successas surgical execution Rehabilitation / physiotherapy is essential in Regaining joint mobility lost during splinting Training tendon to glide in new course Teaching patients to activate a new muscle to achieve a certain function, which requires development of new neural pathways The more that a patient notices a disability, the greater themotivation, so the easier the retraining Children are usually managed with static protocols or longerprotective phase 12. Basic Principles of Post Operative Rehabilitation Described by Toth 19861. Protective phase Begins at surgery and lasts 3 5 weeks Objectives:- Protective splinting Oedema control Mobilise uninvolved joints2. Mobilisation phaseBegins when tendon healing is adequate for activation (usually 3 5 weeks post op)Objectives Mobilise tendon transfer Immobilise soft tissue Continue immobilisation of uninvolved joints to prevent joint stiffness from disuse Reinforce preoperative teaching and patient education Continue oedema control and protective splinting Begin home rehabilitation program Usually day time dynamic splinting with nightly static splinting3. Intermediate phase Begins 5 8 weeks post operatively Gradually increases hand activity and passive range of motion exercises Limited functional movements permitted4. Resistive phase Beginning at 8 12 weeks Tendon junctions are strong enough to withstand increasing resistance Therapeutic objective is to increase endurance and strength of transferred muscles Work related simulated tasks are begun to patient tolerance