Tendon Transfers for Radial Nerve Palsy

Radial nerve palsy causes devastating functional loss - inability to extend wrist, thumb, and fingers eliminates precision grip, power grip, and all hand positioning. Tendon transfers can restore 85-95% of function when nerve recovery fails. Early recognition and timely surgery (before 12 months) prevents permanent disability.

The timing section above frames transfers as a late salvage after recovery fails - but a high-yield concept is that the wrist-extension transfer can be done EARLY, at the time of (or soon after) nerve repair, as an "internal splint" rather than waiting the full reinnervation period:

• The idea (Burkhalter): perform the pronator teres to ECRB transfer early, while awaiting radial nerve recovery. It provides immediate active wrist extension - so the patient regains a functional, grip-stabilising hand straight away and can often discard the external cock-up splint during the long wait.
• It acts as a "helper", not a burned bridge: because PT is synergistic and the transfer is to the wrist (not the fingers), it does not preclude nerve recovery - if the radial nerve reinnervates the wrist extensors, the PT transfer simply augments them; if recovery fails, it is already in place as the definitive wrist transfer.
• Why the wrist first: wrist extension is the most important single function (it powers grip via tenodesis and positions the hand), so restoring it early gives the biggest functional return during the recovery window; the finger and thumb transfers are usually still staged/decided later.
• Caveat: this is an adjunct to, not a replacement for, the recovery-monitoring pathway; the finger/thumb transfers and any nerve surgery are still timed on reinnervation.

Exam point: the PT-to-ECRB transfer can be performed early as an "internal splint" to give immediate wrist extension during the wait for nerve recovery - it is synergistic, does not block reinnervation, and becomes the definitive wrist transfer if recovery fails.

EMG at 3 months shows denervation (fibrillation potentials). Repeat EMG at 6 months - if no motor unit potentials in radial-innervated muscles, nerve recovery unlikely. Proceed with tendon transfer surgery at this point. Do not wait beyond 12 months - muscle fibrosis reduces transfer success.

The single most-asked radial-palsy question is "what are the options?" - and the examinable framework is the three named transfer sets, which differ only in the finger-extension donor (all three use PT to ECRB for the wrist and PL/FDS to EPL for the thumb):

• Standard / "Jones" set - FCU to EDC: the historical set. The problem is that flexor carpi ulnaris is the only ulnar deviator and the key power-grip wrist stabiliser, so sacrificing it produces radial deviation and weakens the wrist for heavy grip.
• Brand set - FCR to EDC: the popular modern choice. By preserving FCU, it maintains wrist stability/ulnar deviation and avoids the radial-deviation deformity of the Jones set - the main reason FCR is preferred over FCU.
• Boyes (superficialis) set - FDS to EDC/EPL (FDS of middle to EPL+EIP, FDS of ring to EDC), routed through the interosseous membrane: gives independent finger extension at any wrist position and strong excursion, but requires an intact median nerve, more retraining, and a window in the interosseous membrane, and costs PIP flexion of the donor fingers.

Pair these with the thumb/wrist donors: PT to ECRB (wrist - never ECRL, which is radial-artery-vascularised), and PL (or FDS) to EPL (thumb).

Exam point: name the three sets by their finger donor - FCU (Jones, but causes radial deviation), FCR (Brand, preserves FCU - preferred), and FDS (Boyes, independent extension but needs median nerve) - all on a background of PT-to-ECRB and PL-to-EPL.

Factors predicting success:

• Surgery within 12 months of injury (before muscle fibrosis)
• Full passive ROM preoperatively
• M4 or M5 donor strength
• No concurrent nerve injuries
• Compliant with rehabilitation
• Young age and high motivation Patients meeting all criteria achieve M4-M5 transfer strength and return to previous occupation in 90% of cases.

Q: A patient with radial nerve injury at the spiral groove has preservation of which function? A: Elbow extension (triceps innervated proximal to spiral groove). Loss of wrist extension, finger extension, and thumb extension. ECRL is variable - may be spared if injury is distal in spiral groove.

Q: Why is ECRL never used as a donor tendon for transfer? A: ECRL is vascularized by radial artery perforators and harvesting it risks vascular compromise. ECRB is the appropriate recipient for wrist extension restoration via PT transfer.

Q: When is the optimal time to perform tendon transfer surgery for radial nerve palsy? A: 3-6 months post-injury if EMG shows no motor unit potentials. Do not wait beyond 12 months as muscle fibrosis reduces outcomes. 70% of patients recover spontaneously within 3-6 months.

Q: What is the appropriate wrist position when tensioning PT to ECRB transfer? A: 45 degrees of wrist extension with fingers in neutral (not flexed). Too much extension creates finger tightness. Too little extension provides inadequate wrist extension power.

Q: What is the most common cause of inadequate strength after tendon transfer? A: Incorrect tensioning (transfer too loose) or inadequate donor strength (under M4 preoperatively). Prevention: confirm M4 donor strength preop and use proper tensioning technique intraoperatively.

There is no high-level (Level 1) guideline mandating a single pathway. All major bodies converge on: (1) expectant management of closed fracture-associated palsy because spontaneous recovery is the norm; (2) a decision checkpoint at roughly 3 months using clinical examination plus electrophysiology; and (3) tendon transfer as the durable reconstruction for established, non-recovering palsy, with nerve transfer as an emerging alternative when the injury is recent and the proximal nerve is viable (PMID 32093993, 38059217).