Flexor tendon injury of the distal interphalangeal joint (jersey finger)

INTRODUCTION — Rupture of the flexor digitorum profundus (FDP) tendon from its distal attachment is commonly known as jersey finger. This injury occurs most often in athletes involved in contact sports, such as American football or rugby [1]. The injury is often overlooked by players and trainers and misdiagnosed as a "jammed" or sprained finger, but requires more urgent management than these minor injuries.

The mechanism, diagnosis, and management of jersey finger will be reviewed here. The management of other finger injuries is discussed separately. (See "Extensor tendon injury of the distal interphalangeal joint (mallet finger)" and "Distal phalanx fractures" and "Middle phalanx fractures".)

ANATOMY — Finger anatomy is complex and is discussed in greater detail elsewhere. Anatomy of particular relevance to jersey finger injuries is described below. (See "Finger and thumb anatomy".)

The flexor digitorum profundus (FDP) tendon travels along the volar side of the palm and finger and passes distally through a split in the flexor digitorum superficialis (FDS) tendon to insert at the base of the distal phalanx (figure 1 and figure 2). The FDP is the primary flexor of the finger at the metacarpophalangeal (MCP) joint and proximal interphalangeal (PIP) joint. It is the sole flexor of the distal interphalangeal (DIP) joint and is most likely to rupture at its insertion on the distal phalanx (figure 3) [1]. Although uncommon, intra-tendinous ruptures of the FDS can occur, mimicking jersey finger [2].

Tendinous bands called vincula help to secure the FDS and the FDP and carry small penetrating blood vessels and nerves. The vincula also assist with PIP and DIP motion. The FDP receives its blood supply via the vincula longa and vinculum breve, which are fed by branches of the digital arteries. The more the tendon retracts following rupture, the more likely the vascular supply will be disrupted, thereby increasing the risk of complication [3].

MECHANISM OF INJURY — Jersey finger occurs when a flexed distal interphalangeal (DIP) joint is suddenly and forcefully hyperextended, leading to rupture of the flexor digitorum profundus (FDP) tendon at its insertion on the distal phalanx. The eponym derives from the common injury scenario of an American football or rugby tackler who reaches out with flexed fingers to grab the jersey of an opponent who pulls away, causing sudden extension of the tackler's finger [4]. The tendon injury can occur with or without a concomitant avulsion fracture of the distal phalanx.

The ring finger is involved in approximately 75 percent of jersey finger injuries. Several reasons for the frequent involvement of the ring finger have been proposed. The ring finger has more limited independent motion than any other digit [5]. The ring finger's FDP insertion is weaker than the long finger [6]. The ring fingertip appears to protrude further than other fingers when the hand is gripping and therefore absorbs greater force [7].

SYMPTOMS AND EXAMINATION FINDINGS — Athletes with a jersey finger often present with acute pain and swelling over the volar aspect of the distal interphalangeal (DIP) joint and distal phalanx. Examination may reveal pain along the course of the flexor tendon extending proximally from the distal phalanx [1]. The point of maximal tenderness along the finger may represent the stump of the retracted avulsed tendon.

The pathognomonic finding of jersey finger is the inability to actively flex the DIP joint. To examine the integrity of the tendon, the clinician holds the proximal interphalangeal (PIP) joint in full extension and asks the patient to flex the DIP joint (picture 1) [4]. Alternatively, the clinician can ask the patient to make a fist (picture 2) [1]. In either case, the patient will be unable to flex the DIP joint fully. The absence of active flexion suggests a complete disruption of the tendon, while weak incomplete flexion suggests a partial tear.

As part of the complete examination of an injured digit, the clinician should assess the finger's neurovascular function and inspect the soft tissue for lacerations and nailbed injuries. The lateral stability of the DIP joint should be evaluated by placing a radial and then ulnar stress on the joint. Comparison with the corresponding finger of the opposite hand can help to determine if laxity is present, which suggests a collateral ligament injury.

Of note, jersey finger may be misdiagnosed initially as a "sprained finger" or present late if a patient does not appreciate the extent of injury. Complications are more likely with late presentations. (See 'Complications' below.)

INJURY CLASSIFICATION — Flexor digitorum profundus (FDP) injuries can be classified based upon the degree of tendon retraction, as described in Leddy and Packer's grading scheme [5]:

●Type I injuries involve retraction of the profundus tendon all the way to the palm, with associated injuries to the vincula longus and vinculum brevis [1]. Injuries to the vincula disrupt the blood supply to the tendon, necessitating surgical repair within seven days to avoid necrosis of the tendon and a permanent contracture deformity. (See 'Indications for referral' below.)

●Type II injuries involve retraction of the tendon to the proximal interphalangeal (PIP) joint. The tendon stump is held in place by the vincula longa, which are often intact [8]. An avulsion fracture sometimes occurs with type II injuries, and often becomes trapped in the A-3 pulley (figure 4) [1]. Without an observable bony fragment on radiograph, it is impossible to determine the degree of retraction, and thus, all type II injuries should be surgically repaired within seven to ten days, if possible. Successful repairs up to three to six weeks after injury have been reported [9].

●Type III injuries involve a large avulsion fragment that is often intraarticular [8]. The bony fragment prevents retraction past the A-4 pulley and holds the tendon in near-anatomic position obviating the need for urgent repair. The vincula longus and brevis remain intact. Type III injuries are amenable to repair within six to eight weeks [9].

●Type IV injuries are type III lesions with the addition of an avulsion of the FDP tendon from the fracture fragment with retraction of the tendon. Type IV injuries are rare but require urgent repair because of the disruption to the tendon's blood supply [10,11].

●Type V injuries involve bony avulsions coupled with another distal phalanx fracture. These are described as extra-articular or intraarticular (Vb) [12].

DIAGNOSTIC IMAGING — Anteroposterior, lateral, and oblique radiographs should be obtained to rule out avulsion fractures and articular injuries. Radiographs may reveal an avulsion fracture at the base of the distal phalanx (injury types II to IV) (image 1).

An MRI should be obtained if the diagnosis remains in question or the location of the retracted tendon is unclear. Magnetic resonance imaging (MRI) can also be helpful in the evaluation of chronic injuries. According to one small observational study, MRI accurately depicted the location of tendon rupture and the gap between tendon ends as subsequently determined during surgery [13].

Although technically more difficult to perform than MRI, ultrasound can be used to evaluate jersey finger [14]. Dynamic ultrasound should be performed during passive, active, and resisted range of motion. In partial tears, ultrasound shows a hypoechoic, fusiform swelling of the tendon and focal discontinuity of internal fibers. In complete tears, the ruptured tendon is not seen at the distal interphalangeal (DIP) insertion, but the retracted tendon appears as an irregular hypoechoic lesion with posterior acoustic shadowing [15].

In one small observational study, ultrasound accurately identified tendon rupture and adhesive scarring in digital tendons that had been surgically repaired [16]. In a retrospective study of 80 patients with an acute or postoperative flexor tendon rupture, ultrasound was reported to be more accurate than physical examination (95 versus 79 percent), particularly when performed within seven days of injury (accuracy declined to 86 percent if the ultrasound evaluation was performed after one week) [17].

INDICATIONS FOR REFERRAL — Jersey finger injuries require surgical repair in ALL cases, and prompt referral to a hand surgeon is necessary. This is particularly important given the potential difficulty in determining the injury type. Although type III injuries may not be repaired for a couple of weeks, type I injuries require urgent repair (generally within seven days).

TREATMENT — Acutely, the injured finger should be placed in an aluminum splint with the proximal interphalangeal (PIP) joint and the distal interphalangeal (DIP) joint slightly flexed. The splint provides support and prevents extension of the DIP joint. The patient should avoid DIP extension and rest the hand until it can be evaluated by a hand specialist.

Definitive treatment for ALL cases of complete disruption of the flexor digitorum profundus (FDP) tendon involves surgical repair. Because it can be difficult to determine the injury type clinically, urgent surgical referral is necessary. The scheme of injury types is described above. (See 'Injury classification' above.)

Type I injuries involve substantial retraction of the tendon and must be diagnosed and treated within seven days from the initial injury. The blood supply of the retracted tendon is often disrupted with type I injuries, which can lead to a muscle contracture and permanent finger dysfunction. The injury is repaired by reattaching the tendon to the distal phalanx [1]. Multiple repair techniques have been described using pullout wire/sutures, mini-suture anchors, or tendon repair with incorporation of the volar plate [2,9,18].

Type II injuries may be successfully repaired up to six to eight weeks following the initial trauma because of the close proximity of the tendon stump to its attachment and preservation of the long vinculum, which provides blood flow to the tendon [1,9]. However, fibrosis can occur at the flexor digitorum superficialis (FDS) arch, which would limit finger flexion [19]. Therefore, many hand surgeons advocate repair within 7 to 10 days for most type II injuries. The results of a small observational study suggest that patients who undergo early primary repair achieve better functional results [20].

Type III injuries typically have preserved blood supply but involve large avulsion fractures that require open reduction and internal fixation of the osseous fragment to the distal phalanx [1]. Most surgeons advocate early repair within two to three weeks of the injury [9].

Type IV injuries involve retraction of the avulsed FDP tendon, which can cause significant disruption of the blood supply, potentially leading to a more difficult surgical repair. Therefore, these injuries should be repaired within one week.

RETURN TO WORK OR SPORTS — Individuals with an acute jersey finger should NOT return to work or a sport that requires the use of their hands until evaluated by a hand surgeon. Patients generally may not return to sport for a minimum of three months following surgical repair. Return to full grasping before 10 to 12 weeks may result in rerupture of the tendon [9].

COMPLICATIONS — Failure to recognize a jersey finger injury early and perform the appropriate surgical repair leaves the patient unable to flex the injured distal interphalangeal (DIP) joint (picture 2). Scarring and pain at the site of the distal tendon stump, instability of the DIP joint, weak proximal interphalangeal (PIP) joint flexion, and finger stiffness can also occur [1].

Some patients report dorsal subluxation of the distal phalanx and instability with chronic untreated injuries [19]. Arthrodesis of the DIP joint can help with chronic complications, particularly instability of the DIP joint [8]. Chronic tendon rupture can be repaired with tendon grafting in some type II and III injuries [9]. Although such patients often fail to regain their preinjury range of motion, satisfactory results can be achieved [21].

Following repair of acute injuries, there is often some loss of DIP function according to observational studies. Adhesions and joint contractures of the DIP joint are common. A series of 36 patients who underwent tendon reinsertion reported an average loss of DIP joint extension of 10 to 15 degrees [22]. Both DIP joint flexion and grip strength were largely intact. Quadriga is a rare phenomenon where advancement of the retracted flexor digitorum tendon of the affected digit during surgery can lead to limitations or a loss of DIP flexion in adjacent fingers [2]. Surgical repair while the patient remains awake may decrease the incidence [18].

A subset of nine patients included in a larger case series of patients with surgically repaired flexor digitorum profundus (FDP) injuries underwent repair of avulsion injuries [23]. Six of the nine were type II jersey fingers treated with primary tendon reinsertion and three were type III injuries repaired by open reduction and internal fixation. Although six of the nine patients had good to excellent overall results, only two had good to excellent outcomes when DIP motion was assessed independently.

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topic (see "Patient education: Common finger injuries (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Anatomy – Jersey finger is an acute rupture of the flexor digitorum profundus (FDP) tendon at its insertion at the distal phalanx. The tendon may retract to the proximal interphalangeal (PIP) joint or all the way to the palm. (See 'Anatomy' above.)

●Mechanism – Rupture of the FDP is caused by a sudden, forceful hyperextension of the distal interphalangeal (DIP) joint. (See 'Mechanism of injury' above.)

●Physical examination – Examination findings with jersey finger injuries include pain and swelling at the palmar DIP joint or along the volar aspect of the involved finger and inability to flex the DIP joint. (See 'Symptoms and examination findings' above.)

●Surgical referral – All jersey finger injuries should be referred urgently to a hand surgeon. Definitive treatment is surgical in all cases, and some injuries require surgical repair within 7 to 10 days. (See 'Indications for referral' above.)

●Misdiagnosis and complications – Jersey finger may be misdiagnosed initially as a "sprained finger" or present late if a patient does not appreciate the extent of injury. Complications are more likely with late presentations. (See 'Complications' above.)