Abstract
Flexor tendon injury occurs to the muscle-tendon flexor system of the hand. Flexor tendons are prone to laceration and rupture with injuries commonly occurring in association with manual labor, athletics, and in the setting of degenerative tendon rupture. Examination should evaluate resting hand posture, active and passive range of motion at each digital joint, strength against resistance at each digital joint, and digital neurovascular status. Surgical intervention is typically required for most flexor tendon finger injuries. Rehabilitation focuses on appropriate postoperative splinting protocols with the goal of limiting adhesion formation, restoring motion, and restoring function. Early motion splinting protocols have been shown to reduce postoperative adhesions and improve range of motion when compared to static splinting in flexor tendon injuries. Early motion protocols can utilize passive or active mobilization, or a combination thereof. Flexor tendon injury may result in permanent loss of finger flexion. Partial tendon damage can be easily missed and result in weakness or progress to complete rupture.
Keywords
Flexor tendon finger injury, Jersey finger, Sweater finger
| Synonyms | |
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| ICD-10 Codes | |
| M20.0 | Acquired deformities of finger(s) |
| M66.34 | Spontaneous rupture of tendons, hand |
| M66.341 | Spontaneous rupture of tendons, right hand |
| M66.342 | Spontaneous rupture of tendons, left hand |
| S66.0 | Injury of long flexor muscle, fascia, and tendon of thumb at wrist/hand level |
| S66.01 | Strain of long flexor muscle, fascia, and tendon of thumb at wrist/hand level |
| S66.02 | Laceration of long flexor muscle, fascia, and tendon of thumb at wrist/hand level |
| S66.1 | Injury of flexor muscle, fascia, and tendon of other and unspecified finger at wrist/hand level |
| S66.11 | Strain of flexor muscle, fascia, and tendon of other and unspecified finger at wrist/hand level |
| S66.12 | Laceration of flexor muscle, fascia, and tendon of other and unspecified finger at wrist/hand level |
Definition
The flexor system of the digits is formed by the flexor muscles that originate in the forearm, including the flexor digitorum superficialis (FDS), flexor digitorum profundus (FDP), and flexor pollicis longus, their corresponding tendinous extensions into the digits, and the digital flexor sheaths that house the tendons in the digit. The digital flexor sheath has an inner synovial component and an outer retinacular component. The synovial component maintains a low friction environment for tendon movement and supplies nutrition to the tendon. The retinacular component thickens to form the pulley system that tethers the tendon to the digit, maximizing tendon excursion with digit motion.
The flexor tendon system of the fingers is divided into five zones where flexor tendon injury may occur ( Fig. 31.1 ).
Zones I and II comprise the distal-most aspect of the flexor tendon system where the tendons are contained within the flexor tendon sheath. Injuries in these zones frequently damage the flexor sheath and may damage the vincular system that provides secondary security and nutrition to the tendons. Damage to these structures complicates healing potential and increases the risk of postoperative adhesions. Zone I is the distal-most portion of the FDP tendon, located from the FDP tendon insertion at the base of the distal phalanx to the midportion of the middle phalanx distal to the FDS insertion. Injury here affects the FDP, leading to the inability to flex the distal interphalangeal (DIP) joint. “Jersey finger” occurs in zone I as the avulsion of FDP from the distal phalanx. This commonly occurs in sporting events as the result of a sudden extension force on an actively flexing DIP joint. Jersey finger, much like mallet finger in extensor tendon injuries, can have associated avulsion fractures of the distal phalanx.
Zone II extends from the midportion of the middle phalanx to the distal palmar crease. This zone is known as “no man’s land” because of the poor functional results after tendon repair. Tendon injury in this zone usually involves both FDP and FDS tendons and results in inability to flex the DIP and proximal interphalangeal (PIP) joints.
Zones III, IV, and V comprise the more proximal region of the flexor tendon system. Zone III is located from the distal palmar crease to the distal portion of the transverse carpal ligament. This zone includes the intrinsic hand muscles and vascular arches.
Zone IV overlies the transverse carpal ligament where the flexor tendons traverse the carpal tunnel. In this zone, injuries usually involve multiple FDP and FDS tendons.
Zone V is proximal to the carpal tunnel, extending from wrist crease to the level of the musculotendinous junction of the flexor tendons. Injuries in this region most often result from self-inflicted laceration (suicide attempts).
Flexor tendons of the hand are vulnerable to laceration and rupture. Injuries commonly occur in association with manual labor (lacerations from sharp objects, crush injuries), in athletes (jersey finger), and in people with rheumatoid arthritis (degenerative tendon rupture). In general, finger flexor tendon injuries are less common than finger extensor tendon injuries. Open laceration injury occurs more commonly in zone II, frequently involving the index finger flexor tendons. The most common closed flexor tendon injury is jersey finger, typically involving the ring finger. Injuries can be complete or partial. Partial injuries are easily missed on examination and can progress to full ruptures if untreated.
Physical Examination
Obtain a detailed history outlining the mechanism of injury. Ask about any premorbid motion deficits in the hand that may complicate examination. Begin the evaluation by noting the resting hand position. If the flexor tendon is completely disrupted, the unsupported finger will assume an extended position at the joint(s) distal to injury ( Fig. 31.2 ).
