5 Flexor Tendon Injuries (Zone 3–5)

10.1055/b-0040-177420

5 Flexor Tendon Injuries (Zone 3–5)

Derek L. Masden

Abstract

Flexor tendon injuries within zones 3 to 5 represent those confined to the palm and distal forearm. They can be debilitating with resultant loss of basic hand function. A thorough understanding of the anatomy, surgical approach, reconstructive options, and rehabilitation is required to provide the best opportunity for functional recovery in these anatomic regions. Proper exposure with identification and repair of neurovascular structures and repair of injured tendons with sound surgical technique can ensure successful outcomes and recovery.

5.1 Description

The majority of literature on flexor tendon injury focuses on the management of zone 2 lacerations. Although much of this is applicable to flexor tendon injuries in other zones, several key differences exist between zones. Surgeons must be familiar with these differences when evaluating, treating, and rehabilitating patients with zones 3 to 5 flexor tendon injuries.

5.2 Classification

The classification of the zone of injury is through the following standard anatomical boundaries: zone 3 marks the area of the palm between the carpal tunnel and the flexor tendon sheath, or from the distal aspect of the transverse carpal ligament to the proximal border of the A1 pulley; zone 4 describes the area within the carpal tunnel; and zone 5 is from the proximal border of the transverse carpal ligament to the musculotendinous junction in the proximal forearm See Fig. 4.1.

5.3 Key Principles

Given the close proximity of tendons, nerves, and blood vessels in the hand and forearm, combined injuries are common, and there should be a low threshold for surgical exploration and identification of the surrounding neurovascular structures. Primary tendon repair is preferred and possible in the majority of zones 3 to 5 injuries. A minimum of a four-strand repair and an epitendinous suture is recommended (► Fig. 5.1). Early active motion rehabilitation protocols should be employed to optimize functional outcomes after these injuries.

**Fig. 5.1 (a)** Original Kirchmayer/Kessler: Two sutures (two-strand) with knots buried in the tendon outside the suture line. A two-strand core suture with knots. In the suture line or burled in the tendon outside the suture line. lntratendinous knots may have better gliding properties, but have more suture material in the tendon gap. Theoretically, sutures should be placed insofar as possible at the volar aspect of the tendon to avoid disturbance of the dorsally situated vessels. Too much compression at the suture line should be avoided to prevent bulging of the tendon repair with subsequent impairment of gliding. **(b–e)** Modified Kessler: One or two sutures (two-strand) with intratendinous knots. Cross section demonstrates optimal position of core sutures (*continued*). **(f)** Strickland’s “double grasp” modification of the Kirchmayer-Kessler technique (two-strand). **(g)** “Double grasp” technique with an additional rectangular mattress suture (four-strand). **(h,i)** Tsuge’s loop technique: Double loop (six-strand). **(j)** Pulvertaft technique: The tendon stumps are connected in a braided pattern–excellent tensile strength, allows early active mobilization. **(k,l)** Epitenon sutures: Epitenon sutures add considerable tensile strength to the tendon repair. They also smooth the contour of the tendon repair, thereby improving gliding properties. The two most commonly used patterns are running stitches (5–0) or interlocking sutures (5–0). A modification is a crisscross pattern that may increase tensile strength. (Modified with permission from Günter Germann, L. Scott Levin, Randolph Sherman. Reconstructive Surgery of the Hand and Upper Extremity, 1st edition. © 2018 Thieme.)

5.4 Expectations

Zones 3 to 5 injuries are more forgiving than zone 2 injuries due to excellent tendon nutrition, a bed that is less prone to adhesions, and fewer surrounding retinacular structures, thereby easing repair and promoting tendon gliding. As such, good to excellent outcomes in range of motion and tendon function should be expected. However, concomitant neurovascular injury can complicate recovery and functional outcomes after such combined injuries. ¹ ^, ²

5.5 Indications

Complete lacerations or > 60% transection of the flexor tendons in zones 3 to 5.

5.6 Contraindications

Contraindications include severe multitissue injuries to the hand and fingers, contaminated wounds, significant soft tissue loss over the flexor system, and patients that are unable to participate in rehabilitation. These instances may require staged tendon repair or reconstruction after an adequate wound bed and soft tissue coverage have been established.

5.7 Diagnosis

Similar to other zones, complete transection of a flexor tendon in zones 3 to 5 will present with inability to flex the digit at the interphalangeal joints along with loss of the natural resting cascade of the hand (► Fig. 5.2). Given the close proximity of the vascular palmar arch and neurovascular bundles, detailed examination of the peripheral nerves and vessels around the zone of injury and distally is imperative. The Allen’s test must be performed when examining pulses as retrograde flow through palmar arches may mask vascular injuries. There should be a low threshold for surgical exploration as innocuous lacerations may hide the extent of deep structural injury, and the preoperative examination is often unreliable in these patients. ³