Tendon Transfers

Tendon Transfer Principles & Donors - The Great Muscle Shuffle

• Goal: Restore lost function via rerouted tendon.

• Indications: Irreversible nerve palsy (radial, median, ulnar), muscle loss.

• Timing: 3-6 months post-injury; stable soft tissues, supple joints.

• Boyes' Pre-requisites (Critical):

  • Supple joints (full passive ROM).
  • Soft tissue equilibrium (mature scar, no inflammation).
  • Donor muscle strength: MRC Grade ≥ 4/5.
  • Expendable donor (no significant functional loss).
  • Similar excursion & power to recipient if possible.

• Core Principles:

  • One transfer for one function.
  • Synergistic muscles preferred.
  • Straight line of pull.
  • Correct tension (avoid too tight/loose).
  • Secure fixation.

• Common Donors (Forearm):

  • PT (Pronator Teres)
  • FCR (Flexor Carpi Radialis), FCU (Flexor Carpi Ulnaris)
  • BR (Brachioradialis)
  • ECRL (Extensor Carpi Radialis Longus), ECRB (Extensor Carpi Radialis Brevis), ECU (Extensor Carpi Ulnaris)
  • APL (Abductor Pollicis Longus)
  • Consider: Strength, excursion, direction.

⭐ Key Boyes' pre-requisites for successful tendon transfer: Supple joints & donor muscle strength of at least MRC Grade 4/5.

Radial Nerve Palsy Transfers - Wrist Drop Reversal

• Goal: Restore wrist, finger (MCPJ), & thumb extension/abduction.
• Wrist Extension (Workhorse):
  • Pronator Teres (PT) → ECRB (Extensor Carpi Radialis Brevis).
• Finger (MCPJ) Extension:
  • FCU (Flexor Carpi Ulnaris) / FCR (Flexor Carpi Radialis) / FDS (Flexor Digitorum Superficialis) (Middle/Ring) → EDC (Extensor Digitorum Communis).
• Thumb Extension/Abduction:
  • PL (Palmaris Longus) → EPL (Extensor Pollicis Longus) (rerouted).
  • FDS (Ring) / FCR (split) → EPL.

⭐ PT to ECRB is crucial for wrist extension. Insertion into ECRB, not ECRL (Extensor Carpi Radialis Longus), prevents unwanted radial deviation of the wrist during extension.

Median & Ulnar Nerve Palsy Transfers - Grasp & Pinch Revival

• Median Nerve Palsy (Ape Thumb):
  • Goal: Restore thumb opposition.
  • Common Transfers (Opponensplasty):
    • EIP to APB (Bunnell).
    • FDS (Ring) to APB (Riordan).
    • PL to APB (Camitz).
• Ulnar Nerve Palsy (Claw Hand, Froment's sign):
  • Goal: Correct clawing, restore key pinch.
  • Claw Correction (Intrinsic Minus):
    • Static: Zancolli lasso (FDS loop).
    • Dynamic: Brand (FDS MF 4-tail), Fowler (ECRL + graft).
  • Key Pinch (Adductor Pollicis): BR/ECRB + graft.
  • 📌 Mnemonic: "BRAND new FDS for 4 fingers" (Brand: FDS for 4 fingers).
• Combined Palsy: Prioritize opposition > finger flexion > intrinsics.

⭐ For low ulnar nerve palsy, Zancolli lasso procedure (FDS loop through A1 pulley) is a common static transfer to correct clawing by preventing MCP hyperextension.

Tendon Transfer Post‑Op & Complications - Healing & Hurdles

• Post-Op Protocol:
  • Immobilization: Splint/cast for 3-6 weeks.
  • Mobilization: Early controlled passive motion, progressing to active motion.
  • Rehabilitation: Phased physiotherapy crucial for strength, ROM, and function.
• Healing Dynamics: Tendon junction strength builds over weeks; maturation takes months.
• Potential Hurdles:
  • Adhesions (most frequent, restrict glide).
  • Rupture (risk with premature stress or poor compliance).
  • Imbalance: Overcorrection or undercorrection.
  • Joint stiffness/contracture.

⭐ Adhesions are the most common complication following tendon transfer, significantly limiting active range of motion and functional outcome.

High‑Yield Points - ⚡ Biggest Takeaways

• Radial Nerve Palsy: Common transfers: PT to ECRB (wrist), FCU to EDC (fingers), PL to EPL (thumb).
• Median Nerve Palsy: Opponensplasty is key (e.g., EIP to APB, FDS to APB).
• Ulnar Nerve Palsy: For claw hand: FDS lasso (Zancolli) or Brand transfer.
• Power Loss: Transferred tendon loses one grade of power.
• Prerequisites: Supple joints, good passive ROM, healthy soft tissue.
• Timing: After nerve recovery plateaus (typically 3-6 months).
• Goal: Restore essential functions, not anatomical normality.