31: Flexor Tendon Injuries

Published on 23/05/2015 by admin

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Last modified 23/05/2015

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Flexor Tendon Injuries

Jeffrey S. Brault, DO


Flexor tendon injury, laceration, or rupture

Jersey or sweater finger

ICD-9 Codes

727.64  Rupture of flexor tendons of hand and wrist, nontraumatic

842.1  Sprains and strains of the wrist and hand, unspecified site

848.9  Lacerated tendon (not specific to the hand)

ICD-10 Codes

M66.341  Spontaneous rupture of flexor tendons, right hand

M66.342  Spontaneous rupture of flexor tendons, left hand

M66.349  Spontaneous rupture of flexor tendons, unspecified hand

S63.90  Sprain of unspecified part of unspecified wrist and hand

S63.91  Sprain of unspecified part of right wrist and hand

S63.92  Sprain of unspecified part of left wrist and hand

The appropriate seventh character is added to each code of category 63 to determine episode of care.

S66.921  Laceration of unspecified muscle, fascia and tendon at wrist and hand level, right hand

S66.922  Laceration of unspecified muscle, fascia and tendon at wrist and hand level, left hand

S66.929  Laceration of unspecified muscle, fascia and tendon at wrist and hand level, unspecified hand

The appropriate seventh character is added to each code of category 66 to determine episode of care.


The flexor tendons of the hand are vulnerable to laceration and rupture. These injuries are most commonly seen in individuals who work around moving equipment, use knives, or wash glass dishes; in people with rheumatoid arthritis; and in athletes (jersey finger) [1]. The flexor digitorum profundus (FDP) of the ring finger is the most commonly involved [2]. Incomplete injuries to the flexor tendon are easily missed on physical examination and can progress to full ruptures.

Regions of potential tendon injury are divided into five zones (Fig. 31.1) [3]. Zone I is from the tendon insertion at the base of the distal phalanx to the midportion of the middle phalanx. Laceration or injury in this zone results in disruption of the FDP tendon and the inability to flex the distal interphalangeal (DIP) joint. 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 [4,5]. Tendon injury in this zone usually involves both FDP and flexor digitorum superficialis (FDS) tendons and results in inability to flex the DIP and proximal interphalangeal (PIP) joints. 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 in the area of the carpal tunnel. In this zone, injuries usually involve multiple FDP and FDS tendons. Zone V extends from the 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).

FIGURE 31.1 Zones of flexor tendons.

The flexor tendons are held close to the bone in zone I and zone II by a complex series of pulleys and vincula. These structures are frequently injured with the tendons [1].


On occasion, individuals may hear a popping sensation as the flexor tendon tears. This is followed by pain, swelling, and inability to flex the affected joint. Sensation of the involved finger is often affected because of the proximity of the flexor tendons to the neurovascular bundle.

Physical Examination

Obtaining a detailed history is important to outline the mechanism of injury. Evaluation begins with observation of the resting hand position. If the flexor tendon is completely severed, the unsupported finger will assume an extended position (Fig. 31.2) [1,6]. Active flexion of all finger joints needs to be assessed. If active finger flexion is not observed because of pain, tenodesis can be employed to determine whether the tendon is intact. The wrist is passively extended, and all fingers should assume a relatively flexed posture. If the flexor tendons are disrupted, the finger will remain in a relatively extended posture.

FIGURE 31.2 Jersey finger. The flexor profundus tendon is detached by a forced hyperextension of the DIP joint. (Reprinted from Mellion MB. Office Sports Medicine, 2nd ed. Philadelphia, Hanley & Belfus, 1996.)

Flexion strength of each digit should be evaluated by manual muscle testing or finger dynamometry. Strength is evaluated by having the patient individually flex first the DIP joint and then the PIP joint against applied resistance. It is possible to have a complete laceration of the flexor tendons with preservation of peritendinous structures and active motion. In these cases, however, flexion will be weak [7].

For individual function of the FDP tendon to be checked, the patient is asked to flex the fingertip at the DIP joint while the PIP joint is maintained in extension. If there is injury to the FDP tendon, the patient will be unable to flex the DIP joint.

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