Upper Limb Tendon Transfers

Definition

  • Transfer of a functional muscle tendon unit to a non-functional unit in order to restore or improve function

Muscle-Tendon Unit Mechanics

  • Force exerted is proportional to the cross-sectional area of the muscle
  • Force of contraction is greatest at a muscle’s resting length
  • Tendon Excursion (amplitude) is proportional to the length of the muscle
  • Sufficient excursion of transferred tendon is required to restore full function
    • Smith’s 3-5-7 rule estimates the excursion of:
      • Wrist Flexors & Extensors - 3cm
      • Finger Extensors - 5cm
      • Finger Flexors – 7cm
  • Work Capacity is force times length
  • Power is Work per unit time

Principles of Tendon Transfer

Rule of 13 S’s

  • Covers patient, tendon, surgical and joint factors

Patient

  • Sensible & motivated

Tendon

  • Strong
  • Sacrificable
  • Synergistic
  • Sufficient excursion

Surgery

  • Straight
  • Scarless skin
  • Stable wound bed
  • Subcutaneously transferred
  • Secure fixation distally
  • Single function

Joint

  • Supple
  • Sensate

“In a Sensible patient, I will transfer a Strong, Sacrificable, Synergistic tendon with sufficient excursion, straight through a scarless, stable, subcutaneous bed over a supple, sensate joint to achieve a single function by secure fixation distally.”

Indications for Tendon Transfer

The 3 R’s – Restore, Replace, Rebalance

  1. Restore Function (nerve injury)
  2. Replace ruptured or avulsed tendons
  3. Rebalance a deformity

Timing of Transfers

  • Usually worth waiting to see what equilibrium has been achieved
  • Do not wait too long
  • Motor end plate undergoes degradation at 12-18 months
  • Early transfers are <1 month, late are >6 months

Choice of Tendon

  • Think about what needs restoration
  • What tendons are available?
  • Which fits the above criteria?

Radial Nerve Lesions

Clinical Features

High Lesion (Axilla or proximal)

  • All muscles lost including triceps
  • Sensory deficit over:
    • Anatomic snuffbox
    • Posterior arm (posterior cutaneous nerve of forearm)

Low Lesion – Mid-arm and elbow findings

  • Triceps intact, all other muscles lost
  • Anconeus, Brachioradialis, and ECRL innervated above elbow
  • Supinator

Management

Splinting

  • Static extension splint with passive ROM
  • Radial Splint (Lively splint)
    • Outrigger with elastic bands to replace ECRB, EPL, and EDC

Transfers

Indications for Transfer

  • No recovery by 6 months
  • ECRL should be recovering by 6 months
  • Consider early restoration of wrist extension to place fingers at an advantage

Transfer Priorities

  1. Wrist Extension
  2. Finger Extension
  3. Thumb Extension

Typical Radial Nerve Transfers

  • PT to ECRB
  • FCR to EDC
  • PL to EPL
    • If no PL (20%) use FDS (ring finger) to EPL

Other Points

  • FCR preferred to FCU
  • Balances wrist especially if ECRL intact
  • PT to ECRB not always needed in low injury as ECRL functional
  • Often done anyway as ECRB is a more central, stronger wrist extensor
  • Restoration of wrist extension places thumb flexors at advantage
    • Improves pincer grip
  • Jones Transfer – classic transfer
    • PT to ECRB
    • FCU to EDC
    • FCR to EPL
      • An option when PL not available
      • Problem: Wrist becomes unbalanced – radial deviation

Median Nerve Lesions

1st muscle supplied: Pronator Teres

Last muscles supplied: Thenar muscles (OP, APB, FPB)

High Lesion - Above Distal Forearm

  • PT, PQ, FDS, half FDP, FCR, FPL, APB, half FPB, OP
  • AIN palsy if at elbow level – PQ, FPL, lateral two FDP
  • Sensory loss over lateral 3 ½ digits

Low Lesion

  • Only thenar muscles lost - OP, APB always
    • FPB is half innervated by Ulnar nerve
    • APB is key to opposition function
  • Sensory loss over lateral 3 ½ digits

Goals of Restoration in Order of Importance

  1. Thumb opposition (APB more important for this than OP)
  2. Thumb flexion (FPL)
  3. Index/Middle finger flexion (FDP)
  4. Forearm pronation (PT)

Available Tendons

  • FDS (in low palsy); Ulna half FDP; EPL; BR; EID; PL
  • Only Opposition needs restoration in a low palsy

Common Median Nerve Transfers

Opposition (APB)

  • EIP to APB
  • In a low median nerve – use PL to APB (Camitz transfer)

Thumb Flexion

  • BR to FPL

Index/Middle Finger Flexion

  • Ulna FDP buddy to Radial FDP
  • Fuse DIPJs

Forearm Pronation

  • Biceps re-routed to radial aspect radius – pronates rather than supinates

Ulnar Nerve Lesions

High Lesion

  • 1st muscle supplied: FCU
  • FDP (ulnar half)

Low Lesion

  • FDM, ODM, ABD DM, 2 Lumbricals, 3 Palmar IOS, 4 Dorsal IOS, ADP, FPB ½

Priorities of Treatment

  1. Restore ADP – provides post for pincer grip
  2. Correct clawing – FDP and Lumbricals
  3. 1st Dorsal IOS – Index abduction improves pincer grip
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