Transcript Principles of Tendon Transfers

Principles of Tendon Transfers
What is a tendon transfer?
• The tendon of a functioning muscle is detached from its
insertion and reattached to another tendon or bone to
replace the function of a paralysed muscle or injured tendon.
The transferred tendon remains attached to its parent muscle
with an intact neurovascular pedicle.
• Or “Using the power of a functioning muscle unit to activate a
non functioning nerve/muscle/tendon unit”.
• Tendon transfers work to correct instability, imbalance, lack of
co-ordination and restore function by redistributing remaining
muscular forces
Indications
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Paralysed muscle
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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
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Considerations
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Graft vs. transfer (adhesions more likely in graft – 2 anastomoses)
Quality of available donors
Length of time since injury
Nature of tendon bed
Balancing deformed hand e.g. cerebral palsy or rheumatoid arthritis
Some congenital abnormalities
General principles
1. Only justified in restoring functional motion of the hand, not just motion
• Not all patients require the same functions/motions
2. 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 physiotherapy
3. 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
4. Donor muscle factors (APOSLE)
Amplitude of the donor muscle
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Should be matched to the unit being replaced
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Finger flexors  60 - 70mm, finger extensors and EPL  40 - 50mm, wrist flexors / extensors  30 - 40mm,
brachioradialis  20 - 30mm
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Amplitude 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 wrist
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Tenodesis effect during active movement
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Freeing fascial attachments to donor tendons
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Inserting the tendon closer to the joint being moved, but this requires a motor unit of increased power (due to
leverage); and vice versa
Power of the donor muscle
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Any 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 preoperatively.
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Strongest are brachioradialis and FCU. Donor power correlated roughly with cross sectional area of muscle and
fibre length
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Overly powerful muscles will unbalance and, over time, deform a joint. So muscle power should be matched if
possible.
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Effective power of a transfer can be increased by placing the tendon insertion farther from the joint axis and as
close to 90° as possible
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Brachioradialis does not adapt well to transferred functions
One tendon, One function
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Effectiveness reduced in transfer designed to produce multiple functions
Synergistic muscle groups are generally easier to retrain
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Fist group – wrist extensors, finger flexors, digital adductors, thumb flexors, forearm pronators, intrinsics
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Open hand group – wrist flexors, finger extensors, digital abductors, forearm supinators
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Use of synergistic muscles tends to help retain joint balance
Line of transfer
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Should approximate pull of original tendon if possible
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Acute angles should be avoided
Expendability
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Transfer must not cause loss of an essential function
5. Other muscle factors of secondary importance
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Innervation - 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 action
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6. Tension of the transfer
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“All transfers should be sutured at the maximum tension in the position
that reverses their proposed activity” (Lister’s 4th Edn)
7. Location and nature of pulley if required
8. Selected arthrodeses
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Simplify polyarticular system
Stabilise joints
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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 palsy
Arthrodeses useful in providing stable pinch grip
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Thumb MPJ and IPJ
Index PIPJ and DIPJ
9. Timing
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“The 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 mobility
Early 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 injury
10. Comparison to alternatives
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Nerve repair or transfer
Tendon repair or graft
Tenodesis (joint stabilisation by anchoring tendons that move the joint)
Arthrodesis
Amputation
Muscle lengthening, release or denervation (in spasticity)
11. Contraindications
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Age – due to joint stiffness, decreased need for power movements and difficult rehabilitation
Motivation – patients must be concerned about disability and highly motivated to perform hand rehabilitation
Task analysis – transfers must be designed to accomplish tasks rather than just specific motions. Eg opening doors
requires grasp and twist
Nature of disability – systemic and local disease factors must be controlled before reconstruction attempted
12. Disadvantages
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No increase in strength
Normal function of transferred muscle is lost
Transferred tendon may perform a different force, amplitude of movement and functional pattern
Transferred tendon must learn a new movement/function
Selecting donor tendons
• Based on Smith & Hastings (Principles of tendon
transfers to the hand. Instr Course Lect 29:129, 1980)
1. List functioning muscles
2. List which of those muscles are expendable
3. List hand functions requiring restoration
4. Match #2 and #3
5. Staging
Example of planning tendon transfers in complex upper
extremity palsies
Working
Available
Needed
BR
BR
Thumb flexion
PT
PT
Finger extension
Thumb extension
ECRL
ECRL
Finger flexion
ECU
ECU and graft
MP flexion / IP extension (intrinsics)
FCU (fair)
FCU (fair)
Thumb opposition
PP
Thumb adduction
ECRB
FCR
PQ
Stage 1: BR to FPL, ECRL to FDP, FCU to EPB for thumb opposition
Stage 2: PT to EPL & EDC, thumb IP arthrodesis
Stage 3: ECU + plantaris graft to lateral bands of index to little fingers (routed volar to deep transverse metacarpal
ligament)
Maximising Success / Surgical Technique
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Incisions should not cross the path of the transferred tendon
Avoid interference with normal structures
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 excursion
The transferred tendon should insert into another tendon or bone. Strong insertions allow
earlier mobilisation.
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.
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.
Joint should be initially immobilised in a position that relieves tension at the insertion of
the transfer
Reverse order – harvest grafts, prepare recipient site and tunnel before raising muscle
General Post Operative Management
• Rehabilitation is equally important in tendon transfer success
as 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 the
motivation, so the easier the retraining
• Children are usually managed with static protocols or longer
protective phase
Basic Principles of Post Operative
Rehabilitation
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Described by Toth 1986
1. Protective phase
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Begins at surgery and lasts 3 – 5 weeks
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Objectives:–
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Protective splinting
Oedema control
Mobilise uninvolved joints
2. Mobilisation phase
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Begins when tendon healing is adequate for activation (usually 3 – 5 weeks post op)
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Objectives
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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
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Usually day time dynamic splinting with nightly static splinting
3. Intermediate phase
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Begins 5 – 8 weeks post operatively
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Gradually increases hand activity and passive range of motion exercises
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Limited functional movements permitted
4. Resistive phase
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Beginning at 8 – 12 weeks
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Tendon junctions are strong enough to withstand increasing resistance
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Therapeutic objective is to increase endurance and strength of transferred muscles
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Work related simulated tasks are begun to patient tolerance