Thursday, November 8, 2007

Tendon Transfer--General Principles

Tendon transfers are done to restore a function that has been lost. It is a procedure in which the tendon of a functioning muscle is detached or divided at or near it's insertion, mobilized and reinserted into a bony part or another tendon to supplement or substitute for the lost function. Restoring something as simple as a pinch grip can create major improvement in the function of the hand. (photo credit)

Tendon transfers have been used in upper extremity reconstruction for well over a century. Early on, the technique was used for reconstruction following obstetric brachial plexus palsy or paralysis secondary to polio. As hand surgery evolved as a subspecialty, transfer techniques expanded. The middle part of the 20th century saw the development of transfers for multiple peripheral nerve paralyses, including median, ulnar, and radial nerve palsies. Some of the "Giants" who contributed to the field, include Bunnell, Boyes, Brand, Burkhalter, Goldner, Littler, Moberg, Omer, Phalen, Riordan, and Zancolli.

Indications for tendon transfers

  • Irreparable nerve damage --Penetrating injuries can result in transection of the median, ulnar, or radial nerves or more centrally in the brachial plexus.
  • Loss of function of a musculotendinous unit due to trauma or disease -- Rupture of the extensor pollicis longus (EPL) tendon is a common complication secondary to a distal radial fracture. Rheumatoid arthritis may be responsible for tendon rupture of any of the hand and wrist tendons, but it commonly leads to rupture of extensor tendons of the fingers or thumb (photo credit).
  • In some non-progressive or slowly progressive neurological disorders -- These tends to be less responsive to surgical solutions, and can include stroke and neurologic diseases such as multiple sclerosis or cerebral palsy.

Contraindications:

  • The only absolute contraindication to tendon transfer is a lack of appropriate donors.
  • The availability of muscle-tendon units with less than grade 5 strength is a relative contraindication.
  • Similarly, if only muscles that have been denervated and then reinnervated are available, this is also a relative contraindication.
  • Transfers planned in individuals with progressive neuromuscular diseases should be carefully considered before proceeding because the underlying disease process may affect the transferred unit.
  • Lastly, satisfactory results are difficult to achieve in transfers performed to produce motion in less-than-supple joints.
Most important functions of the Upper Extremity
Grasp power (FDP & wrist stabilisers)
Pinch (FDP, FDS & intrinsics)
Positioning the hand
Radial nerve injuries affect opening the hand for grasping.

Low ulna and median nerve defects affect surrounding the object to grasp.

High ulna and median nerve injuries affect long flexors and grip

Axillary palsy and brachial plexus palsy -- unable to abduct the shoulder and here shoulder arthrodesis may be indicated to stabilise the upper arm to enable effective use of distal muscles. (generally transfers around the shoulder of little value)

Elbow function dependant on the musculocutaneous nerve. Pectoralis major transfer to biceps (Clark), proximal transfer of the common flexor origin (Steindler), triceps transfer (Bunnell) and may restore elbow flexion. Latissimus dorsi can also be used to restore elbow flexion.

Key elements crucial in tendon transfer operations.

  • Be sure that the tendon to be transferred can be spared from it's original location. The EIP has redundant function with the EDC and, thus, is expendable. Before transfer of the EIP, especially in a patient with rheumatoid arthritis, the surgeon should be confident that the EDC has not been affected by the disease and is functioning normally.
  • Be sure that it is strong enough for its new task. Only muscles with power of 4+ should be considered donors as they always lose 1 MRC grade of power.
  • Be sure it has enough amplitude for its movement. As a guide, amplitudes are as follows: Wrist motors 33mm; Finger extensors 50mm; Finger flexors 70mm.
  • Be sure that is is under conscious voluntary control
  • Be sure that its old action is synergistic with its new, or at least retrainable to it (photo credit--example of natural synergic movement: The effect shows extension of the fingers when the wrist is flexed and flexion of the fingers when the wrist is extended. If the tendons are not intact, this effect is lost.)
  • Be sure that it can reach its new insertion without a sharp change of direction
  • Be sure that it can get to its new location without going through dense scar tissue, through fascia, or across bare bone
  • Be sure that the movement it is expected to produce is already freely possible by passive movement (no stiff or "frozen" joints)
  • Be sure that they patient understands what is to be done and is ready to accept the postoperative discipline of exercises and training

Timing

The timing of a tendon transfer after an injury depends on the likelihood of spontaneous reinnervation and nerve recovery. If nerve repairs or nerve transfers were performed initially, then sufficient time has to be allowed to determine the outcome of the initial treatment before considering tendon transfers. Keep in mind that axons regenerate at a rate of approximately 1 mm per day. If one cannot determine from the initial injury whether the nerve was interrupted (neurotmesis) and if the clinical examination reveals a loss of motor or sensory function, determining if adequate recovery is likely is mandatory before considering tendon transfer as a reconstructive option. EMG performed immediately and then again at 6 weeks helps to determine which functions may be expected to recover. Lack of evidence of innervation at 6 weeks should prompt exploration and repair if possible. Once sufficient time has elapsed to allow for spontaneous or repaired recovery, consider reconstruction for missing functions. (photo of some splints often used in upper limb paralysis--credit)

Of note, some hand surgeons advocate early tendon transfers, particularly in patients with radial nerve palsies, even if recovery is still possible. In 1974, Burkhalter reported that the indications are

(1) the transfer can act as a substitute during regrowth of the nerve, which will thereby reduce the time of external splinting and improve early function

(2) the transfer can act as a helper and add power to normal reinnervated muscle function

(3) the transfer can act as a substitute when, statistically, the recovery after neurorrhaphy or nerve repair is poor.

References

Tendon Transfer Surgery--American Society for Surgery of the Hand

Hand, Tendon Transfers by Philip E Higgs, MD--eMedicine article

Tendon Transfer Principles and Mechanics by Premal Sanghavi, MD and Mohammad Ali, MD--eMedicine article

Surgical Reconstruction and Rehabilitation in Leprosy and other Neuropathies by Richard Schwarz, MD

Peripheral Nerve Problems --Military Report by Colonel George E. Omer, Jr., MC, USA (Ret.), and Colonel William W Eversmann, Jr., MC, USA (Ret.)

1 comment:

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