Modern Study Review (AI-Generated)
High-Yield Summary
Tendon transfers remain a cornerstone in restoring hand function after intrinsic muscle paralysis, commonly due to low median or ulnar nerve injuries. The primary goal is to re-establish a stable base for thumb opposition and finger MCP joint stability, thereby improving pinch strength and grasp mechanics. Modern techniques emphasize balancing flexion and extension forces around the MCP joints to prevent deformities such as clawhand and intrinsic plus deformity. Understanding the biomechanics and selecting appropriate donor tendons are critical for optimal functional outcomes.
Key Diagnostic Findings
| Aspect | Details |
|---|---|
| Anatomy | – First dorsal interosseous: key for thumb pinch stability – Intrinsic muscles: stabilize MCP joints and coordinate finger flexion-extension |
| Clinical Presentation | – Clawhand deformity with MCP hyperextension and IP joint flexion – Weak pinch and grasp strength (up to 50% loss) – Long extensors intact but ineffective if MCP hyperextended |
| Imaging | – Usually clinical diagnosis – EMG/NCS to localize nerve injury – X-rays to rule out joint contractures or arthritis |
| Classification Systems | – No formal classification for tendon transfers; however, nerve injury level (low median/ulnar) guides treatment – Clawhand severity scales may assist in planning |
Current Gold Standard Treatment
| Treatment Type | Indications & Approach |
|---|---|
| Non-operative | – Splinting to prevent MCP hyperextension (e.g., intrinsic plus splint) – Hand therapy to maintain ROM and strengthen compensatory muscles |
| Operative | – Tendon Transfers: • Extensor Indicis (EI) transfer to first dorsal interosseous insertion for thumb stability • Abductor Pollicis Longus (APL) transfer, often with palmaris longus graft, to restore thumb abduction and pinch • Intrinsic restoration via transfers such as: – Zancolli volar capsulodesis or Riordan tenodesis for MCP stabilization – Bunnell FDS transfer (single slip to avoid intrinsic plus deformity) – Fowler split extensor communis tendon transfer – Riordan FCR transfer with plantaris graft for combined wrist and intrinsic deficits |
| – Arthrodesis | Reserved for severe MCP instability or fixed deformities not amenable to soft tissue reconstruction |
Modern Complications & Outcomes
| Complication | Notes |
|---|---|
| Intrinsic Plus Deformity | Overcorrection from strong extensor transfer (e.g., full FDS slip) causing MCP flexion contracture and IP hyperextension |
| Residual Clawing | Incomplete correction due to inadequate MCP stabilization or poor tendon tensioning |
| Donor Site Morbidity | Weakness or loss of function in donor tendon territory (e.g., index finger extension after EI transfer) |
| Joint Stiffness | Due to prolonged immobilization or inadequate therapy |
| Functional Outcomes | Tendon transfers improve pinch and grasp strength significantly; success depends on patient selection, surgical technique, and rehabilitation |
Classic Clinical Notes
PRINCIPLES 2
- Providing a stable base against which the thumb pinches. It is a function largely of the first dorsal interosseous muscle.
- Tendons most frequently used are extensor indices, EPB, palmaris longus, APL.
- Extensor Indices transfer: simply take the EI insertion off the ulnar aspect of the extensor hood, then transfer it radially to the insertion of the first dorsal interosseous.
- Abductor Pollicis Longus transfer: identify a slip of APL (usually there are two) and route it via a free palmaris longus graft to the insertion of the first dorsal interosseous.
Restoring Intrinsic Function
- Low median and ulnar nerve lesions cause paralysis of the intrinsics, but spare the long extrinsics to act unopposed, resulting in a clawhand.
- Without the intrinsics, grasp strength is diminished by 50% because of lack of flexion at the MCP joints; also, the dynamics of finger flexion are altered, so that the fingers “roll up” rather than flex properly – flexion begins distally at the DIP joints. This makes it difficult to grasp large objects.
- It should be noted that the long extensors ARE able to extend the fingers fully, but only when the MCP joints are stable and not hyperextended (when hyperextended, the long extensors exert and lose all their power at the level of the MCPs and cannot act at the PIP or DIP joints).
Techniques to restore intrinsics
- One approach is to just stabilize the MCPs so that they don’t fall into hyperextension (this allows the fingers to be flexed by the extrinsics and extended by the extrinsics).
- Zancolli – volar capsulodesis
- Riordan – tenodesis
- Arthrodesis
- The other approach is to perform tendon transfers that will extend the IP joints and flex the MCP. There are many procedures advocated – all are based on the principle of moving something volar to the deep transverse metacarpal ligament, then back up to the dorsal hood.
- Bunnell – FDS transfer from volar to dorsal hood (often makes the strong PIP flexor into too strong of an extensor, creating an intrinsic plus deformity – can be avoided by only taking one of the two slips of FDS)
- Fowler – split extensor communis tendon from index and little fingers to form four slips, which are then re-routed volar to the deep transverse metacarpal ligament and then back dorsally to the extensor hood of each finger.
- Riordan – FCR transferred dorsally to a free plantaris graft divided into four slips, each then passed through the interossei to lie volar to the deep transverse metacarpal ligament. Good for when a wrist flexion contracture exists.
Last Updated on January 24, 2026 by orthonet
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