Restoration of active pinch and grasp: Extensor carpi radialis longus transfer to flexor digitorum profundus

Indications

• Performed in patients with intact wrist extension supported by the extensor carpi radialis brevis (ECRB) who require transfer for active finger flexion.

• Patients must be at least class 3 on the International Classification for Surgery of the Hand in Tetraplegia scale (see Table 69.2 ), with an expendable extensor carpi radialis longus (ECRL) that can be transferred without compromising wrist extension.

• This transfer enables active grasp and can be tailored to achieve normal (fingers with increased degree of interphalangeal [IP] flexion in the index to small finger direction) or “reverse” cascade (fingers with decreased degree of IP flexion in the index to small finger direction).

• This transfer is synergistic, using a wrist extensor to achieve finger flexion.

• This procedure can also be used in patients with combined median/ulnar nerve injury (See Chapter 67 Tendon Transfers for Combined Nerve Palsy).

Clinical examination

• An organized examination of the entire upper extremity is performed. See Chapter 69 Tendon and Nerve Transfers for Spinal Cord Injury Patients for details.

• Patients who are candidates for extensor carpi radialis longus (ECRL) transfer have functional elbow and wrist extension and desire better pinch and grasp function.

• It is important to ensure adequate ERCB function to maintain wrist extension after ECRL transfer.

Imaging

Standard radiographs of the elbow, wrist, and hand are helpful if the patient has clinical findings of joint stiffness or contracture or to evaluate for arthritis. Patients with significant arthrosis and lack of passive range of motion (ROM) are not candidates for tendon transfer.

Surgical anatomy

• The ECRL originates from the lateral supracondylar ridge of the humerus and inserts onto the dorsal base of the index finger metacarpal. It is innervated by the radial nerve above the elbow and receives blood supply from the radial artery. This muscle is responsible for wrist extension and radial deviation.

• The flexor digitorum profundus (FDP) originates from the proximal ulna and interosseus membrane and inserts at the volar distal phalanx of index, middle, ring, and small fingers. It is found in the deep volar forearm compartment and its blood supply comes from the anterior interosseus artery. It has dual innervation; the index and middle fingers are innervated by the median nerve and the ring and small fingers are innervated by the ulnar nerve. The index finger tendon often has a separate muscle belly.

• The median nerve enters the forearm between the superficial (humeral) and deep (ulnar) heads of the pronator teres (PT) muscle. After emerging from the PT, the median nerve passes deep to the arch created by the two heads of the flexor digitorum superficialis (FDS). The nerve continues distally in the forearm between the FDS and FDP and becomes superficial approximately 5 cm proximal to the wrist, emerging between the flexor carpi radialis (FCR) and palmaris longus (PL) tendons.