26: Reconstruction of Key Pinch in Tetraplegia Patients

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Procedure 26 Reconstruction of Key Pinch in Tetraplegia Patients

Pao-Yuan Lin, Sandeep J. Sebastin, Kevin C. Chung

See Video 21: Tendon Transfer for Lateral Pinch in Tetraplegic Patients (BR to FPL, FPL to EPL, ECRL to FDP)

Indications

Procedure is used in patients with cervical spine injury with partial upper limb paralysis (spinal cord injury at or below C5 cervical segment) with at least grade 4 strength of the brachioradialis (BR).

General considerations

• More than 12 months have passed after the injury with stabilized motor recovery.

• Patient is medically stable and motivated.

• Patients with poor sensation of the hand may not be candidates for tendon reconstruction because the lack of sensory feedback may present difficulties in use of the reconstructed hand.

Specific considerations for key pinch

• Patients with intact wrist extensors (extensor carpi radialis longus [ECRL]) (group 2) are the best candidates for key pinch reconstruction because the BR can be transferred to the flexor pollicis longus (FPL) to get an active key pinch.

• Only a passive key pinch can be achieved in group 1 patients because they lack wrist extension, and the priority is to get wrist extension. The BR is transferred to the extensor carpi radialis brevis (ECRB) to restore wrist extension, and a passive key pinch is obtained by tenodesis of the FPL, extensor pollicis longus (EPL), and abductor pollicis longus (APL) to the distal radius.

Examination/Imaging

Clinical Examination

Tetraplegia patients are classified based on the number of functional muscles with grade 4/5 Medical Research Council (MRC) strength below the elbow (Table 26-1). Based on what the patient has, the patient’s needs are matched by using a combination of tendon transfers, tenodesis, and arthrodesis to optimize surgical reconstruction.

The purpose of the key pinch reconstruction is to allow the patient to produce a tenodesis effect to firmly pinch an object between the tip of the thumb and the radial border of the index finger. The differential excursion between the extrinsic flexor and extensor tendon system results in the tenodesis effect. When the wrist is extended, the flexor tendon becomes tight, resulting in finger flexion. With the wrist flexed, the fingers extend secondary to tightening of the extrinsic extensor tendons. Patients with tetraplegia use the tenodesis effect to help develop patterns of pinch function to assist in activities of daily living.

It is important to assess the strength of the BR. Muscles chosen for transfer should be at least MRC grade 4 because they lose one grade after transfer. This is done by holding the patient’s elbow in midprone position and asking the patient to flex the elbow against resistance (Fig. 26-1). This will contract the BR. The examiner tries to move the contracted BR. If the BR cannot be moved easily with BR contraction, it is suitable for transfer. On the other hand, if the BR is flaccid and can move easily during contraction, the muscle may not be strong enough for transfer.

The index finger should also be assessed. If the index finger is flaccid, it may not provide a strong post for the thumb. The flexor digitorum superficialis (FDS) of the index finger can be sutured to the A1 pulley or the volar plate in a lasso procedure so that the index finger can be flexed to act as a post for the reconstructed thumb.

The procedures required to achieve key pinch in group 1 and group 2 tetraplegia patients are as follows:

• Group 1 (only BR)

♦ Split FPL-to-EPL transfer (to stabilize thumb interphalangeal [IP] joint)

♦ FPL tenodesis to volar radius (to provide passive key pinch during wrist extension)

♦ EPL and APL tenodesis to dorsal radius and lateral radius, respectively (to allow thumb to abduct and extend during wrist flexion for the release phase of key pinch)

♦ BR to ECRB (to provide active wrist extension and passive key pinch by tenodesis)

♦ FDS lasso procedure (if index finger metacarpophalangeal [MCP] joint flexion is deemed inadequate for key pinch)

• Group 2 (BR and ECRL)

♦ Split FPL-to-EPL transfer (to stabilize thumb IP joint)

♦ BR to FPL (to provide active thumb pinch)

♦ EPL and APL tenodesis to dorsal radius and lateral radius, respectively (to allow thumb to abduct and extend during wrist flexion for the release phase of key pinch)

♦ FDS lasso procedure (if index finger flexion is deemed inadequate for key pinch)

Table 26-1 International Classification for Surgery of the Hand in Tetraplegia

Motor Group	Functioning Muscles (Grade 4 or Greater)
0	No available muscles
1	BR
2	BR and ECRL
3	BR, ECRL, and ECRB
4	BR, ECRL, ECRB, and PT
5	BR, ECRL, ECRB, PT, and FCR
6	BR, ECRL, ECRB, PT, FCR, and finger extensors
7	BR, ECRL, ECRB, PT, FCR, finger and thumb extensors
8	Lacks only intrinsics

BR, brachioradialis; ECRL, extensor carpi radialis longus; ECRB, extensor carpi radialis brevis; FCR, flexor carpi radialis; PT, pronator teres.

FIGURE 26-1

Surgical Anatomy

Figure 26-2 presents the segmental innervation (C5 to T1) of muscles of the elbow, forearm, and hand, and Figure 26-3 shows the relevant anatomy of the procedure.