Hand Tendon Transfers

Anatomy and Physiology

Pathoanatomy of Specific Nerve Injuries 

Functional deficits will vary based upon the specific structures injured, as well as the location of the injury along the course of that structure.[4][5][6] In the upper extremity, characteristic deficits result from injuries to the radial, median, and ulnar nerves (the primary focus of this article). These injuries are often classified as either "high" or "low." They are as follows:  

• Radial Nerve
  • High radial nerve injuries occur above the elbow and lead to deficits in:
    • Wrist extension with denervation of the brachioradialis, extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), and extensor carpi ulnaris (ECU)
    • Finger metacarpophalangeal (MCP) joint extension with denervation of the extensor digitorum communis (EDC), extensor indicis proprius (EIP), and extensor digit minimi (EDM)
    • Thumb extension with denervation of the extensor pollicis longus (EPL)
    • Sensation in the superficial radial nerve distribution
  • Low radial nerve injuries occur distal to the elbow and affect muscles innervated by the posterior interosseous nerve (PIN). These injuries typically have no sensory deficits because they occur distal to where the superficial radial nerve branches off the radial nerve, but result in the following motor deficits:
    • Weakness in wrist extension as the innervation to the ECU is lost, but the ECRL innervation is often preserved, leading to radial deviation with wrist extension
    • Finger MCP extension weakness secondary to denervation of the EDC, EIP, and EDM
    • Thumb extension weakness secondary to denervation of the EPL 
• Median Nerve
  • High median nerve injuries occur proximal to the elbow and lead to weakness of:
    • Thumb opposition secondary to denervation of the superficial head of the flexor pollicis brevis (FPB), abductor pollicis brevis (APB), and the opponens pollicis
    • Thumb interphalangeal (IP) flexion secondary to denervation of the flexor pollicis longus (FPL)
    • Distal interphalangeal (DIP) flexion secondary to denervation of the index and long finger flexor digitorum profundus (FDP)
    • Proximal interphalangeal (PIP) flexion secondary to denervation of the flexor digitorum superficialis (FDS)
    • Forearm pronation secondary to denervation of the pronator teres and pronator quadratus
    • Wrist flexion secondary to denervation of the flexor carpi radialis (FCR); ulnar deviation occurs with wrist flexion since the flexor carpi ulnaris (FCU) is intact
    • Sensory deficits in the thumb, index, middle, and radial half of the ring fingers
  • Low median nerve injuries occur distal to the elbow, resulting in the following motor and sensory deficits:
    • Thumb opposition secondary to denervation of the superficial head of the FPB, APB, and the opponens pollicis
    • Sensory deficits in the thumb, index, middle, and radial half of the ring fingers
• Ulnar Nerve
  • High ulnar nerve injuries occur proximal to the elbow, leading to deficits in:
    • Ring and small finger DIP flexion secondary to denervation of the FDP
    • Ring and small finger MCP flexion secondary to denervation of the interossei and ring and small finger lumbricals
    • Pinch strength secondary to denervation of the adductor pollicis (ADP), deep head of the flexor pollicis brevis (FPB), and first dorsal interosseous
    • Sensory deficits both volarly and dorsally in small finger, ulnar half of the ring finger, and on the ulnar third of the palm
  • Low ulnar nerve injuries occur at the level of the wrist, leading to deficits in:
    • Ring and small finger MCP flexion secondary to denervation of the interossei and ring and small finger lumbricals
    • Pinch strength secondary to denervation of the ADP, deep head of FPB, and first dorsal interosseous
    • Sensory deficits on the volar aspect of the small finger and ulnar half of the ring finger

Indications

The indications for a hand tendon transfer will depend on the severity and impact of the functional deficit for each patient. To determine this, a thorough history and physical examination should be performed.

History

The clinician should obtain information regarding the patient's hand dominance, mechanism of injury, date of injury or onset of symptoms, any functional deficits they have noted (with an understanding of their prior baseline level of function), and prior treatments attempted. Additionally, a thorough review of the patient's past medical and surgical histories is necessary to assess for medical comorbidities that may influence the surgical and anesthetic risks. 

Physical Examination

A complete examination of the entire upper extremity, with an emphasis on the hand and wrist, should be conducted. This includes a detailed, systematic assessment of motor and sensory function for each primary nerve, muscle, and tendon.[7][8][9] This will aid in localizing the key injury(s) and determining the severity of each deficit. The following are a few clinical findings to note (this list is not exhaustive):

• Range of motion of each affected joint: Stiff joints may require preoperative hand therapy or other interventions to restore full range of motion before a tendon transfer can be performed
• Wrist passive tenodesis testing should be performed by passively ranging the wrist from flexion to extension. In the setting of a normal test, the digits transition from an extended posture in wrist flexion to a flexed posture in wrist extension, with the fingers maintaining a symmetric cascade. An abnormal exam may indicate isolated tendon injuries. 
• In an ulnar nerve palsy, when the patient attempts to pinch a piece of paper with their thumb and index finger, the thumb MCP hyperextends. The interphalangeal joint flexes in an attempt by the EPL and FPL, respectively, to compensate for the deficiency of the adductor pollicis, first dorsal interosseous, and the deep head of the FPB. This is called the Froment sign. 
• The integrity of the EPL tendon (particularly in the setting of a nondisplaced distal radius fracture) can be assessed by having the patient place their palm flat on a table and then lift their thumb upward off the table. An inability to lift the thumb is consistent with an EPL rupture.

An electromyogram can help determine the severity of nerve injury and the likelihood of recovery. Unlike procedures to reinnervate muscles, tendon transfers do not depend on the viability of the motor endplate of the dysfunctional muscle and, thus, can theoretically be performed at any time. However, in the setting of a spinal cord injury, tendon transfers may be delayed until at least 12 to 18 months following injury to allow time for maximum natural recovery with therapy. Ultimately, the final indications for a hand tendon transfer rest on the aforementioned considerations and patient-specific goals and expectations. 

Contraindications

Contraindications for a hand tendon transfer include, but are not limited to, the absence of an appropriate donor muscle-tendon unit, limited passive range of motion (indicating a stiff joint), minimal-to-no anticipated functional improvement with surgery, inability for the patient to attend necessary postoperative follow-up and hand therapy sessions, and significant patient comorbidities that preclude safe surgical intervention.  

Equipment

The required operative equipment includes select suture material, a basic hand tray (with dissecting scissors and forceps), and a tendon passer (if desired).[10]

Preparation

The procedure is typically performed in the operating room under general anesthesia, although local anesthesia has also been described.[11][12] A tourniquet is placed high in the axilla, and the operative upper extremity rests on a hand table.

Technique or Treatment

Principles of Tendon Transfer to Mitigate Complications 

• Choose a donor tendon for transfer that minimizes functional loss. The donor tendon should be expendable.
• The muscle strength of the donor tendon must be near normal, as it will lose a function grade with the transfer (eg, a tendon with 5/5 strength will decrease to 4/5 strength after transfer).
• The excursion of the donor tendon should be similar to the excursion of the recipient tendon. Wrist extension and flexion tendons have 33 mm of excursion, finger extensors have 50 mm of excursion, and finger flexors have 70 mm of excursion (Smith 3-5-7 rule). Utilizing the tenodesis effect of the wrist can compensate for an additional 20 to 30 mm of finger tendon excursion. 
• The donor tendon should be routed in the direction of pull, in line with the recipient tendon.
• A single tendon transfer should aim to restore one function.
• Soft tissue adjacent to the transfer site should be stable and pliable to allow for tendon gliding. Full passive range of motion of the joint controlled by the transferred tendon should be achieved before surgery.
• Ideally, donor tendons should be in the same phase as recipient tendons (eg, finger extensors act in phase with wrist flexors, and finger flexors act in phase with wrist extensors).[13][14][15]

Surgical Procedures 

There are various surgical procedures based upon the injuries being addressed.[16][17][18] They are as follows: 

• Radial Nerve Injury
  • Wrist extension achieved with transfer of pronator teres to ECRB
  • Finger MCP extension achieved with transfer of the FCR to EDC or FDS of the middle finger to the EDC
  • Thumb extension achieved with transfer of the palmaris longus to the EPL or FDS of the ring finger to the EPL
• Low Median Nerve Injury
  • Thumb opposition achieved with transfer of the abductor digiti minimi to the APB (Huber), extensor indicis proprius to the APB (Burkhalter), or FDS of the ring finger to the APB (Bunnell or Royle-Thompson). These are considered opponensplasty procedures as they attempt to restore thumb opposition. Palmaris longus to APB (Camitz) transfer is another well-described procedure, but only restores palmar abduction, not thumb opposition.
• High Median Nerve Injury
  • Thumb opposition is achieved with transfers described above
  • Thumb interphalangeal flexion is achieved with transfer of the brachioradialis, ECRL, or ECU to the FPL
  • DIP and PIP flexion to the index finger can be achieved by transferring the ECRL to the FDP tendon of the index finger or by side-to-side tenodesis of the FDP tendons
• Ulnar Nerve Palsy 
  • Clawing is corrected by blocking MCP hyperextension, thereby allowing EDC extensor forces to be transmitted distally to the PIP and interphalangeal joints through the extensor hood. This is accomplished by MCP capsulodesis or tenodesis. The FDS slips of the affected finger can be transected 2 cm proximal to their insertion and sutured back to themselves proximally, thereby creating a lasso around the A1 pulley (Zancolli lasso).
  • Alternatively, the FDS of the middle finger can be transected 2 cm proximal to its insertion and retracted from the tendon sheath proximally and then rerouted distally deep to the intermetacarpal ligament and inserted into the radial lateral bands of the small and ring fingers (Stiles-Bunnell). Clawing of all 4 digits (as seen in a combined ulnar and low median nerve palsy) can be treated using the FCR, or ECRB tendon split into 2 to 4 tails according to the number of fingers being addressed. The tails are then extended using free tendon grafts and attached to the radial lateral bands of the small, ring, and middle fingers and the ulnar lateral band of the index finger (Brand).

Power pinch (normally achieved by the ulnarly-innervated adductor pollicis, first dorsal interossei, and deep head of the flexor pollicis brevis) can be addressed using the ECRB or FDS for an adductorplasty. The ECRB adductorplasty is performed by detaching the ECRB from its insertion on the base of the second metacarpal and retrieving it proximal to the extensor retinaculum. A free tendon graft is then used as an extension on the end of the ECRB tendon and routed distally between the second and third metacarpals and attached to the adductor pollicis insertion on the first metacarpal.

Alternatively, FDS adductorplasty can be performed using the middle-finger FDS. The FDS is harvested 2 cm proximal to its insertion and routed across the palm and attached to the adductor pollicis insertion. EPL rupture in the setting of a healed distal radius fracture is treated with an EIP to EPL transfer. When harvesting the EIP, it can be identified ulnar to the index EDC tendon at the level of the metacarpal head.

Donor tendons are often attached to recipient tendons using the Pulvertaft weave. Using this method, the donor tendon is woven back and forth through the substance of the recipient's tendon, with each pass approximately 90 degrees perpendicular to the previous, and the tendon is fixed with a mattress suture. A minimum of 3 passes should be used for appropriate strength. Alternatively, techniques such as side-to-side, spiral linking, and lasso reconstruction may be used to connect the donor and recipient tendons. In recent cadaveric studies, side-to-side suturing was shown to outperform the Pulvertaft weave in terms of load-to-failure.[19][20]

Complications

Beyond typical postoperative complications, such as infection and wound dehiscence, hand tendon transfer procedures may have the following additional complications: 

• Improper graft tensioning can result in excessive laxity or tightness, leading to impaired digital or wrist range of motion. This can result from abnormal tensioning during initial graft placement, rupture of the repair site or knot failure, or slit propagation (particularly with the Pulvertaft weave technique). Alternative repair techniques (eg, spiral linking and loop-tendon suture) can be used based upon surgeon preference to improve the biomechanical strength of the repair site.[13][21]
• Impaired tendon glide may result from increased bulk at the repair site or adhesion formation. This can lead to decreased range of motion and/or triggering symptoms.

Clinical Significance

Functional deficits of the upper extremity can have profound effects on the affected patient. In cases of neurotendinous injuries or pathology, hand tendon transfers may be a viable reconstructive treatment option. By routing a healthy muscle-tendon (donor) unit to a weak or nonfunctional muscle-tendon (recipient) unit, range of motion, strength, and overall function can be improved. Postoperatively, custom bracing and meticulous follow-up care with a hand therapist are crucial for ensuring appropriate healing of the repair site and restoring function.  

Enhancing Healthcare Team Outcomes

Successful hand tendon transfer surgery requires meticulous preoperative planning, technical expertise, and coordinated interprofessional care to restore upper extremity function while maximizing patient safety and long-term outcomes. Physicians and advanced practice providers must perform comprehensive evaluations of tendon integrity, joint mobility, muscle strength, donor tendon availability, peripheral nerve function, and patient-specific functional goals before selecting an appropriate tendon transfer. Careful patient selection, optimization of comorbidities, and thorough preoperative counseling regarding expected outcomes, rehabilitation requirements, and realistic functional recovery are essential components of patient-centered care. Hand surgeons frequently collaborate with neurologists, physiatrists, orthopedic surgeons, plastic surgeons, and peripheral nerve specialists to determine the underlying etiology of dysfunction, establish surgical candidacy, and coordinate the timing of tendon transfer with nerve recovery, fracture healing, or soft-tissue reconstruction. Shared decision-making allows patients to participate in treatment planning actively and promotes adherence to postoperative rehabilitation.

Effective communication among the interprofessional team is critical throughout the perioperative and rehabilitation phases. Nurses provide perioperative education, monitor surgical wounds, assess neurovascular status, manage pain, and reinforce postoperative precautions while promptly communicating signs of infection, wound complications, or tendon rupture to the surgical team. Pharmacists optimize perioperative antimicrobial prophylaxis, multimodal analgesia, and medication reconciliation while monitoring for adverse drug interactions and opioid stewardship.

Certified hand therapists, occupational therapists, and physical therapists play a pivotal role in postoperative recovery by fabricating custom splints, supervising progressive range-of-motion and strengthening protocols, retraining motor patterns, and helping patients develop functional use of transferred tendons during activities of daily living. Regular communication among surgeons, rehabilitation specialists, therapists, nurses, and primary care clinicians allows individualized progression of therapy, early identification of complications such as adhesions, tendon rupture, joint stiffness, or imbalance, and timely modification of rehabilitation plans. This coordinated, multidisciplinary approach enhances functional recovery, improves patient satisfaction, minimizes complications, and optimizes long-term upper extremity function following hand tendon transfer surgery.