Keywords

Anatomy: Flexor Tendon and Pulley Apparatus

Zones of Injury

Kleinert and Verdan described five zones of injury that consider the anatomy of injury, the biologic mechanisms of repair, and functional outcomes [1] (Fig. 13.1).

Fig. 13.1
figure 1

Flexor tendon zones of injury for the fingers and thumb

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Extrinsic Flexor Tendon Anatomy

The extrinsic flexor muscles originate in the volar forearm and include the flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), and flexor pollicis longus (FPL). The FDP arises from the anterior-medial aspect of the ulna and interosseous membrane and forms a common tendon origin, although typically the index finger has greater independence. The anterior interosseous nerve (AIN) innervates the FDP muscle bellies to the index and middle fingers and the ulnar nerve innervates the ring and small fingers, although variations to this pattern are not uncommon. The superficial flexor muscle, the FDS, is innervated by the median nerve and originates from the medial epicondyle of the humerus, the sublime tubercle of the proximal medial ulna, and the anterior radius. In the forearm, the FDS is separated from the deeper FDP muscle by the median nerve which exits from this interval between the FDS and flexor carpi radialis (FCR) muscles to course distally to the carpal tunnel with the FDS, FDP, and FPL tendons [2].

The FDS and FDP tendons exit the carpal tunnel deep to the superficial palmar arterial arch and are enveloped by a specialized, multi-layered synovial sheath before entering the fibro-osseous digital retinacular system. The common digital neurovascular bundles and the flexor sheath are separated by the vertical retinacular septae of Legeau and Juvara that attach palmarly to the transverse ligament of the palmar aponeurosis and dorsally to the deep intermetacarpal ligament. These eight septae create seven longitudinal compartments: four that contain the flexor tendons, and three that contain the neurovascular bundles and the lumbricals [3].

At the level of the first annular pulley (A1 pulley), the FDS flattens and bifurcates to allow the deeper FDP to pass distally to its insertion at the base of the distal phalanx. The footprint of the FDP insertion is substantial, encompassing nearly the entire palmar surface of the distal phalanx to the neck of the phalanx, just proximal to the tuft [4]. Bifurcating limbs of the FDS rotate laterally and dorsally around the FDP before dividing again into medial and lateral slips. The medial slips of the FDS tendon cross dorsal to the FDP and interdigitate as the chiasma tendinum digitorum manus, or Camper chiasma, over the distal aspect of the proximal phalanx and the proximal interphalangeal joint volar plate [2]. The lateral slips of the FDS tendon continue distally to insert at the palmar base of the middle phalanx (Fig. 13.2).

Fig. 13.2
figure 2

The bifurcating limbs of the FDS tendon rotate laterally and dorsally around the FDP tendon and then divide again into medial and lateral slips. The medial slips cross dorsal to the FDP tendon (decussation), rejoining as the chiasma tendinum of Camper (c) over the distal aspect of the proximal phalanx and PIP joint volar plate. The lateral slip (s) continues distally to insert at the volar base of the middle phalanx. The vincula longum to the profundus tendon (*) is identified as it penetrates the FDS from dorsal to volar. (Reprinted with permission: © Leversedge FJ, Goldfarb CA, Boyer MI. From: Leversedge et al. [2]: 17)

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The FPL originates on the anterior surfaces of the radius and interosseous membrane in the mid-forearm and is innervated by the AIN. The FPL tendon courses through the dorsal and radial aspect of the carpal tunnel, through the interval between the adductor pollicis and the thenar musculature before entering the fibro-osseous digital sheath of the thumb, slightly proximal to the thumb metacarpophalangeal (MCP) joint [2]. The FPL inserts into a broad footprint at the palmar aspect of the distal phalanx.

Intrinsic Musculature

The lumbrical muscles originate from the radial aspect of their respective FDP tendon in the hand and course volar to the deep intermetacarpal ligament to contribute to the extensor mechanism of the digit via the oblique fibers of the extensor hood. It is important to consider the anatomic course of the lumbricals as they are palmar to the MCP joint axis of rotation and dorsal to the axis of rotation of the PIP and DIP joints; the lumbricals continue as the oblique fibers of the extensor hood and contribute to the conjoined lateral bands [2, 5,6,7]. Therefore, the lumbricals assist in flexing the MCP joint and extend the interphalangeal joints. Understanding the relationship between the FDP and the lumbrical musculotendinous units is essential in explaining the phenomenon of paradoxical digital extension following flexor tendon injury and repair.

Flexor Pulley Apparatus

The digital fibro-osseous sheath provides both biomechanical efficiency and a source of nutrition to the flexor tendons. The visceral paratenon envelopes the flexor tendons and the parietal paratenon lines each pulley and the retinacular system [8, 9]. Condensations of the synovial sheath, or pulleys, form at strategic points along the digit to work in conjunction with the transverse carpal ligament and the palmar aponeurosis pulley to maximize efficiency of joint rotation and force transmission.

Classically, five annular (A) and three cruciform (C) pulleys are described for the fingers, as well as the palmar aponeurosis pulley [2, 8,9,10,11,12] (Fig. 13.3). The A1, A3, and A5 pulleys take their origin from volar plates of the MCP, PIP, and DIP joints, respectively, and the A2 and A4 pulleys originate from the proximal and middle phalanges, respectively. The C1, C2, and C3 pulleys are less substantive and are positioned in the A2 and A3, the A3 and A4, and A4 and A5 pulley intervals, respectively. The A2 and A4 pulleys are the most important pulleys biomechanically [13, 14], although several studies have indicated improved clinical outcomes with sacrifice or venting of the critical A4 pulley when its integrity may restrict gliding of the repaired flexor tendon [15, 16]. The anatomical arrangement of the flexor pulleys of the thumb is different from the finger with the A1, oblique, and A2 pulleys described. The A1 pulley is located at the level of the MCP joint, the oblique pulley fibers are oriented in a distal and radial direction at the level of the proximal phalanx, and the A2 pulley originates from the interphalangeal joint volar plate. Biomechanical studies have demonstrated that the A1 and oblique pulleys are most important for resisting FPL bowstringing; biomechanical efficiency is maintained when at least one of these two pulleys is preserved clinically [13].

Fig. 13.3
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Illustration of the digital flexor pulley system and flexor sheath of the finger

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Flexor Tendon Nutrition

The intrasynovial flexor tendons have two sources of nutrition: direct vascular supply and synovial diffusion. The direct vascular system is based on the digital arteries that supply the transverse digital arteries, or “ladder branches,” and the vincular system, as well as the intraosseous vessels that percolate the tendinous insertions [17, 18] (Fig. 13.4a, b). Synovial diffusion occurs in the relatively hypovascular zones of the FDS and FDP within the flexor tendon sheath via intratendinous canaliculi [8, 9].

Fig. 13.4
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(a) Arterial system of the fingers highlighting the digital arteries (a) and the transversely oriented arterial ladder branches (*) that provide perfusion to the flexor tendons via the vincular system. (b) Transverse section of the intrasynovial portion of the digital flexor tendon (clarified following India Ink arterial injection) demonstrating the dorsal vincula or mesotenon that arise from the transverse digital arterial “ladder” branches. (Reprinted with permission: © Leversedge FJ, Goldfarb CA, Boyer MI. From: Leversedge et al. [2]: 18)

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Injury Assessment: Clinical Evaluation

Clinical History

A thorough history is obtained regarding the timing and mechanism of injury. While the timing of open injuries such as a laceration will be obvious, detection of a closed injury to the flexor mechanism may be subtle, leading to a delay in presentation and/or treatment. Pertinent history such as prior extremity injury and pre-existing digital stiffness is noted, and new symptoms such as alterations in sensibility (sensory nerve injury), digital triggering or pain with tendon excursion (tenosynovitis, partial tendon laceration), perceived reduction in strength or flexion lag (loss of tendon integrity, pulley injury, tenosynovitis), or loss of motion/stiffness are recorded. The player may report an audible or palpable “pop” at the time of a specific loading activity to the hand or digit, commensurate with a soft-tissue avulsion injury, such as a pulley rupture [19]. The mechanism of injury, specific to a particular event or play, or to a particular position-dependent activity, is important to review as this knowledge may shed light on the anatomy of injury. For example, a sudden eccentric loading through the DIP or PIP joints may be accentuated with use of a glove or catching mitt, contact with the ground or fencing, by being struck with the ball, or with incarceration in another player’s jersey. Alteration in pitching mechanics and a reduction in accuracy or velocity may be early warning signs of a tendinopathy, intrinsic muscle injury [20], or pulley injury [19] that could progress to a chronic condition in the throwing athlete.

Clinical Examination

A global assessment is critical as concomitant injuries such as fracture or nerve injury may influence treatment recommendations. Inspection of the limb and involved digit(s) confirms an open or closed injury, evaluates for deformity (fracture or dislocation), considers the location of ecchymosis and swelling, and may provide information regarding the neurovascular status of the affected limb. For example, ecchymosis of the digital pulp in the setting of a closed, eccentric extension loading of the distal fingertip is concerning for an FDP avulsion injury and/or fracture. The resting posture of the hand and digits will reflect the influence of the tenodesis effect; observation of tenodesis during inspection and during dynamic testing of the hand and wrist may provide useful information regarding the integrity of the flexor apparatus (Fig. 13.5).

Fig. 13.5
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Typical presentation of a closed, FDP avulsion injury demonstrated in the ring finger. Note the mild swelling and ecchymosis of the distal digit with a characteristic loss of DIP joint tenodesis with the hand in a resting position. (Reprinted with permission: © Leversedge FJ, 2004)

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Focal palpation of the injured hand and wrist progresses through a logical anatomical assessment: the location of injury may be highlighted; however, secondary findings such as the location of a retracted proximal tendon stump, subtle crepitus or triggering with tendon excursion, or local joint instability may improve diagnostic accuracy. Investigation of possible prodromal symptoms or progressive tendon pathology is helpful for considering diagnostic evaluation, serial examinations and/or timely intervention as indicated. Diagnostic clues may improve prophylactc management of an impending tendon injury such as in the setting of hardware prominence following distal radius volar plating or with irregular bony prominences at the hand or wrist such as a hook of the hamate nonunion sustained by a direct palmar injury during batting.

A neurovascular assessment is essential, particularly in the setting of an open injury. Often, digital or palmar lacerations will involve a neurovascular injury and, therefore, sensory and motor examination is routine as well as digital Allen’s testing, where applicable. Although less common, ulnar nerve motor exam is critical prior to surgical intervention for flexor tendon attritional rupture in the setting of a hook of hamate nonunion [21, 22].

The assessment of intrinsic and extrinsic tendon integrity should consider the anatomy of injury, but also anatomic variations that may or may not be present. Evaluation of the FDP tendon involves initial assessment as to presence of the tenodesis effect on the DIP joint during wrist flexion and extension. Discontinuity of the FDP tendon will cause an absence of DIP joint flexion as the wrist is extended (loss of tenodesis), although in rare cases a closed avulsion of the FDP tendon without substantial retraction may exert a flexion force to the distal phalanx via the intact vinculum and / or volar plate of the DIP joint. Active motion of the FDP tendon is assessed with blocking of the middle phalanx as the patient is asked to flex the DIP joint (Fig. 13.6a). Intact but reduced motion may be caused by a partial injury or an impediment to tendon gliding such as flexor tenosynovitis.

Fig. 13.6
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(a) Illustration of the clinical examination technique for evaluating active function of the FDP tendon. (b) Illustration of the clinical examination technique for evaluating active function of the FDS tendon by limiting the indirect action of the FDP tendon

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Independent FDS tendon evaluation is performed by preventing the indirect influence of the potentially intact FDP tendon on PIP joint motion. During assessment of active FDS function, all the other fingers are held in full extension such that the tenodesis effect of the common FDP origin prevents proximal FDP excursion in the finger being tested, although this may be of limited value in the index finger where a more independent FDP origin has been described (Fig. 13.6b). Absence of the FDS to the small finger is a common anatomic variant and may be unilateral or bilateral [23].

In certain conditions, particularly with open injuries to the hand or with a metacarpal fracture, compromise of digital flexion may be caused by intrinsic muscle dysfunction. The delicate balance between intrinsic and extrinsic function for supporting normal hand function is critical, and alterations in this relationship may cause stiffness or paradoxical digital extension via diversion of the extrinsic flexor forces through the lumbrical muscle and extensor tendon mechanism. A Bunnell intrinsic tightness test is performed by assessing the relative resistance to passive interphalangeal joint flexion with the metacarpophalangeal (MCP) joint in flexion (intrinsics are lax) versus in hyperextension (intrinsics are taut) [24]. Increased resistance to passive interphalangeal joint flexion with the MCP joint in hyperextension (versus flexion) is consistent with intrinsic tightness.

In the thumb, FPL integrity is assessed in similar fashion as for the suspected FDP injury with use of tenodesis and with active tendon function assessment with blocking of the proximal phalanx.

The integrity of the flexor pulley apparatus and fibro-osseous digital sheath may be difficult to assess, particularly in the setting of an acute injury where local swelling may influence digital motion. Increased inflammation associated with injury to the flexor apparatus may cause a reduction in digital extension. A loss of flexor pulley integrity may be difficult to confirm by clinical examination alone; however, focal tenderness typically over the critical A2 or A4 pulleys and a concomitant loss of biomechanical efficiency manifest as a flexion lag should raise the suspicion for a pulley rupture when the mechanism of injury is consistent with forceful loading of the flexor pulley system.

Finally, in the setting of a flexor tendon repair and / or reconstruction, evaluation as to the presence/absence of the bilateral palmaris longus tendons is useful, in the event that a source of tendon graft is necessary [25].

Injury Assessment: Imaging

Radiographs

In general, radiographic assessment includes three views of the injured digit(s) to evaluate for possible tendon avulsion with an associated osseous fragment and/or an associated digital fracture or joint subluxation/dislocation. Careful identification of an avulsion fragment along the flexor sheath, particularly at the volar aspect of the PIP joint, may provide useful information regarding the proximal retraction of a closed tendon avulsion injury.

Ultrasound

Improvements in the quality and resolution of ultrasound, despite this technique being user-dependent, have increased its popularity in the assessment of tendon continuity and the level of retraction of a transected or avulsed tendon [26, 27]. Ultrasound may be useful, also, in evaluating patients with a suspected flexor pulley injury and may provide the advantage over MRI as being a point of care and dynamic study [26,27,28,29]. Recently, however, the diagnostic accuracy of ultrasound assessment of certain tendon injuries has been called into question [30].

Magnetic Resonance Imaging

Often, in the setting of a pathologic tendon rupture or tenosynovitis, MRI has been demonstrated to provide useful information prior to surgical exploration and / or tendon reconstruction [29,30,31,32]. A dynamic MRI may be considered to evaluate for a symptomatic closed pulley rupture. This may be done by comparing images obtained of a resting hand in full extension with those of the digit actively held in flexion, or images obtained with active flexion against resistance [32]. While the actual pulley injury may not be visible on MR images, T1 sequences may demonstrate bowstringing of the tendon from the phalanx and T2 imaging sequences will characteristically highlight local peritendinous inflammation [28,29,30,31,32].

Injury Classification: Flexor Tendon

  • Tendon Laceration

Transection or laceration injuries to the flexor tendons are defined by their zone of injury (Fig. 13.1) and as to complete or incomplete lacerations. The anatomic zones of injury permit perioperative planning by the surgeon, both for repair and reconstructive options but also for the coordination of post-repair rehabilitation.

  • Tendon Avulsion

Avulsion of the FDS from its insertion at the base of the middle phalanx is rare, although it has been described in isolation [33], and mid-substance FDS rupture has been described in combination with a distal FDP avulsion [34]. Avulsion of the FDP from its insertion at the base of the distal phalanx is more common and is known by the descriptive term “jersey finger.” The classification system for FDP avulsion injuries emphasizes the variations in both prognosis and treatment choices based on the level of tendon retraction, the remaining sources of nutrition to the avulsed tendon, and the nature of the soft-tissue or bony avulsion fragment. The classification scheme described by Leddy and Packer [35] (Types I, II, and III) was supplemented by Robins and Dobyns through their recognition of a less common, but important Type IIIA injury [36].

Type I

Type I injuries involve a complete avulsion of the FDP tendon and retraction of the tendon (with its bony avulsion fragment, if present) through the flexor sheath and into the palm. The majority of its vincular attachments are striped from the tendon as the tendon is retracted proximally, compromising vascular supply to the tendon.

Type II

Type II injuries involve a complete avulsion of the FDP tendon (with its bony avulsion fragment, if present) and retraction of the proximal stump to the level of the PIP joint. Compared to the Type I injury, there is less disruption of the vincular system. Continuity of the flexor sheath and intrasynovial environment is generally maintained.

Type III

Type III injuries involve avulsion of the FDP tendon from its insertion; however, it retracts no further proximally than the A4 pulley. Proximal retraction of the tendon may be restrained by the vincula and volar plate; however, restriction to proximal retraction of the tendon is typically due to a large bony avulsion fragment that is trapped by the A5 or A4 pulley. In contrast to Type I and II injuries, the vinculae and synovial sheath remain in continuity, improving tendon nutrition.

Type IIIA

The less common Type IIIA/Type IV injury involves a Type III injury, however with avulsion of the FDP tendon from the bony avulsion fragment following incarceration of the bony fragment by the flexor pulley system. The subsequent FDP tendon retraction can, therefore, replicate a Type I or Type II injury. The potential for this injury mechanism highlights the importance of confirming by direct visualization the continuity of the FDP tendon with the bony avulsion fragment at the time of surgical repair. This injury should not be confused with an FDP avulsion injury that occurs incident to a peri-articular fracture of the base of the distal phalanx.

  • Tendon Rupture

Mid-substance tendon rupture is rare; however, this may be caused by progressive attritional changes associated with local factors such as retained hardware (e.g., distal radius hardware) or bone irregularity (e.g., hook of hamate fracture), or underlying medical condition such as inflammatory tendinopathy or gout.

Management of Flexor Tendon Injuries

Pre-Repair Considerations

Clinical suspicion for a flexor tendon injury on the field of play is important as the absence of pain or open injury could promote continued participation and compromise injury outcomes through the increasing migration of the proximal tendon stump. This escalation of injury should be avoided by protecting the digit from further injury by application of a forearm-based resting hand splint application and immediate restriction of activity that might promote further tendon retraction. For open injuries, appropriate wound care should be instituted (debridement and irrigation, hemostasis, sterile dressing care), with an appropriate antibiotic regimen and tetanus update, as indicated.

Injury Management: Surgical Repair

General Principles

Surgical repair of flexor tendons is done in an operating room setting under a general anesthesia or upper extremity regional block. The surgeon (and player) should be prepared for the potential scenarios of tendon repair and reconstruction, including the need for multiple incisions for tendon retrieval, the potential need for a tendon graft source for pulley reconstruction or primary tendon graft reconstruction, use of a silicone tendon implant, and consideration for salvage procedures in the event that primary repair is not feasible. Associated injuries should be considered during the surgical exposure and determination as to an effective strategy for the sequence of repairs. Preoperative antibiotics are given in timely fashion within 1 h of incision, and tetanus toxoid and/or tetanus immunoglobulin are administered when indicated. Repairs are done using loupe optical magnification.

In general, a mid-axial or Bruner-type incision is used to facilitate exposure of the flexor tendon system. Open injuries or lacerations are incorporated into the exposure, maintaining adequate and viable soft-tissue flaps for subsequent closure. The digital neurovascular bundles are protected and meticulous hemostasis is maintained during dissection.

A strategy for exposing and retrieving the injured flexor tendons should be considered prior to opening the digital flexor sheath in order to preserve the biomechanical integrity of the digital flexor sheath system. Iatrogenic peritendinous adhesion formation will be reduced through the careful handling of the gliding surfaces of the flexor tendons and the fibro-osseous digital sheath [37]. Where possible, the A2 and A4 pulleys are preserved, although venting of these critical pulleys or complete release of the A4 pulley is reasonable depending on the level of injury [13]. Preserving the adjacent pulleys, therefore, will assist in reducing the work of flexion in the event that the integrity of the critical A2 and A4 pulleys are compromised, either through the original injury or by venting during surgical exposure.

Often, the retracted tendon stump may be identified within the sheath by the presence of local hemorrhage. The proximal tendon stump may be “milked” distally within the tendon sheath to facilitate retrieval with the wrist and MCP joints held in flexion. The exposed interior substance of the tendon stump may be grasped using fine-toothed forceps. If the tendon stump is not able to be retrieved in an atraumatic manner, then the retracted proximal tendon stump may be retrieved using a pediatric feeding catheter passed retrograde within the flexor sheath from the initial wound or at the distal tendon sheath to a transverse incision in the palm or within the membranous portion of the flexor sheath distal to the A2 pulley [38] (Fig. 13.7). As the tendon(s) are retrieved and brought distally for repair, the FDS and FDP relationship is restored at the level of the FDS bifurcation.

Fig. 13.7
figure 7

Intraoperative photograph demonstrating the use of a pediatric feeding catheter to retrieve the retracted FDP stump at the PIP joint following a closed avulsion injury (Type II) of the ring finger. (Reprinted with permission: © Leversedge FJ, 2004)

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Acute Injuries

Zone I flexor tendon injuries involving avulsion of the FDP tendon from its insertion or a distal laceration of the FDP tendon with insufficient distal tendon for end-to-end repair are treated by advancement of the proximal stump and reinsertion into the distal phalanx. In general, up to 1 cm of advancement may be permissible to avoid the limitations of a post-repair quadriga effect, although the more independent index FDP may tolerate up to 1.5 cm [39]. Various methods of tendon to bone repair have been described including use of: (1) a pullout suture passed through osseous tunnels in the distal phalanx and tied over a well-padded suture button placed on the nail (Fig. 13.8a, b); (2) a pullout suture construct is created similar to (1); however, the suture is passed around the distal phalanx instead of through the phalanx; (3) a suture tied deep to the skin overlying the extensor tendon insertion after passage from volar to dorsal via trans-osseous tunnels; and (4) one or two suture size-appropriate anchors [40,41,42,43,44] (Fig. 13.9).

Fig. 13.8
figure 8

(a) Intraoperative photograph demonstrating an FDP tendon repair using a well-padded, tie-over suture button. Sutures are passed through an osseous tunnel using straight Keith needles that have been drilled through the base of the distal phalanx, avoiding injury to the germinal matrix of the fingernail. (Reprinted with permission: © Leversedge FJ, 2004). (b) Intraoperative photograph demonstrating an FDP tendon repair with the finger held in flexion as the FDP tendon is reduced to its anatomic insertion and the sutures are secured over the polypropylene button. Note that the digital flexion cascade ideally shows slightly increased tension in the repaired digit. (Reprinted with permission: © Leversedge FJ, 2004)

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Fig. 13.9
figure 9

(a) Lateral radiograph of the finger demonstrating an avulsion fracture from the volar base of the distal phalanx fracture consistent with a possible Type III or Type IIIa FDP avulsion injury. (Reprinted with permission: © Leversedge FJ, 2004). (b) Intraoperative photograph demonstrating open fracture reduction and internal fixation of a displaced volar base fracture of the distal phalanx, consistent with an FDP avulsion injury. (Reprinted with permission: © Leversedge FJ, 2004)

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For each of the repair methods, in general, the distal tendon stump is debrided and the volar base of the distal phalanx, distal to the insertion of the volar plate of the DIP joint, is prepared for tendon reattachment by debridement of residual tendon fibers and exposure of the phalangeal cortex, although elevation of a periosteal flap may be used.

If a pullout button repair method is used, the button and suture are removed at approximately 8 weeks postoperatively. It is important to inform the patient as to signs or symptoms of soft-tissue complications while the button is in place as such issues are not uncommon [45], and osseous complications including osteomyelitis can complicate non-pullout suture methods of repair [46]. Suture anchor use should be critically assessed, also, as technique-related studies have demonstrated the risk of intra-articular placement and potential dorsal cortical penetration concerning for nailbed injury and / or infection [47, 48].

Open flexor tendon injuries may involve one or both of the flexor tendons. When both tendons are transected, typically the FDS is repaired first as its inserting limbs are located dorsal to the FDP tendon. Many suture configurations have been described for zone II flexor tendon repair and, while the exact techniques are beyond the scope of this chapter, it is important to consider a modern core suture method which includes the following: (1) at least four suture strands of 4–0 or 3–0 suture, (2) a suture configuration that interacts with the tendon substance in an appropriate grasping or locking fashion, and (3) a method that is finished with an epitendinous suture repair that not only reduces the tendon ends, but also increases the ultimate strength of the tendon repair construct. The use of wide-awake local anesthesia, no tourniquet (WALANT) methods for anesthesia have improved intraoperative assessment of the repaired tendon in regard to tendon gliding and avoidance of gap formation during active tendon excursion [49].

Treatment of partial tendon injuries should consider the amount of tendon involvement appreciated at the time of open tendon exploration or a patient’s symptoms if there is uncertainty as to the extent of injury during clinical evaluation. Although the difficulty in determining the percentage of tendon involvement in a partial tendon laceration has been demonstrated [50], multiple investigators have concluded that partial lacerations involving less than 60% of the tendon’s cross-sectional area should not be repaired. Debridement of the injured tendon may be indicated if the laceration site presents a risk for tendon triggering or entrapment and tendons lacerated greater than 60% should be repaired, typically with a core suture and epitendinous suture repair, as appropriate, to minimize the risk of tendon triggering, entrapment, or rupture [51, 52].

Delayed Repair/Reconstruction

Consideration for tendon reconstruction should account for the level of injury and the functional goals of the individual in the setting of a delayed presentation of flexor tendon injury. The time from injury and the level of tendon retraction will influence whether a primary repair is considered; the length-tension relationship of the musculotendinous unit will be altered by the retracted stump resulting in higher risks of contracture and secondary complications such as the adverse effects of quadrigia. Also, a loss of the favorable gliding environment within the “empty” flexor sheath may require recreation of the potential gliding space through the use of a silicone tendon implant. Second-stage flexor tendon reconstruction is delayed until optimal conditions exist for grafting: (1) a supple and mature wound, free of signs of infection or soft-tissue compromise; (2) maximal recovery of passive digital motion to provide the greatest potential for restoring active motion following tendon reconstruction; and (3) patient compliance with therapy and postoperative care [37].

There are several considerations for reconstructing the flexor tendon-deficient digit. In the finger, patients with an FDP injury but an intact FDS tendon may consider staged flexor tendon grafting; however, procedures that involve excision of the injured FDP tendon (to reduce interference with FDS function) and either DIP joint arthrodesis or DIP joint tenodesis may provide reasonable outcomes [35]. The loss of DIP joint motion, however, may impact adversely the ability of certain position players. Importantly, while these DIP joint stabilization procedures remove the potential for independent FDP function, they are regarded as definitive procedures with consistent results. Typically, the DIP joint is stabilized in neutral or in a slightly flexed position of function. Staged flexor tendon reconstruction, however, typically involves considerable patient investment and commitment with multiple procedures with variable outcomes and, therefore, these factors should be discussed in detail with the patient preoperatively [37]. Similarly, in the thumb, reconstruction of the FPL tendon with intercalary grafting, ring finger FDS tendon transfer, or interphalangeal joint arthrodesis may be considered in light of the patient’s underlying condition and expectations for recovery of function.

Injury Management: Post-Repair Rehabilitation

Post-repair rehabilitation protocols should emphasize several principles: (1) player education is essential to minimize the risk of postoperative repair site rupture and to maximize tendon function; (2) communication with the player, training staff, and therapist is imperative regarding the nature of the injury and the specific protocol to be used; (3) the timing for the initiation of post-repair rehabilitation is ideally between 3 and 5 days to reduce work of flexion; (4) the use of a low-force, high-excursion protocol will maximize tendon gliding, but minimize the risk of repair site failure [53, 54].

The timing for the return to unrestricted activity following flexor tendon repair is not well-defined; however, decisions should be guided by a recognition of the accrual of repair site strength with time and the influence of associated injuries. Typically, return to unrestricted activity is permitted between 4 and 6 months from surgical repair, although it is the author’s preference to delay the release to unrestricted activity until 6 months post-repair, consistent with the recent recommendations of Ruchelsman et al. [55]. Associated injuries and treatments such as fracture of nerve repair may influence the timing of incremental rehabilitation strategies.

Despite well-intended protective splinting or casting of the injured extremity to facilitate early return to play, the high risk of repair site rupture persists due to the inability to restrict tensile forces created by the contracting muscle-tendon unit. Therefore, return to upper extremity contact sport and activities involving higher loading forces through the hand and wrist are not advised for 4–6 months. Throwing, catching, and batting all place high-tensile loads through the flexor system and should be restricted for 6 months from repair. Buddy-strapping of the injured digit to an adjacent digit will reduce the risk of inadvertent eccentric loading or passive extension of the isolated injured digit, particularly in the setting of peritendinous adhesion formation and the relative tethering of the affected tendon(s). A hand-based or forearm-based thermoplastic splint or cast may provide reasonable protection for the healing flexor tendon for non-contact (upper extremity) training activities that present low fall risk.

The indications for flexor tenolysis, typically considered at 4–6 months post-repair, include a failure to regain adequate active and independent gliding of the repaired tendon(s) and to restore functional activities despite achieving excellent passive digital motion. This demanding procedure requires close cooperation between the surgeon, patient/player, therapist, and training staff to ensure optimal outcomes [37].

Flexor Pulley Injury

Injury Classification

Injury to the flexor pulley system may be caused by a closed or an open injury. Often, the treatment of open injuries is considered in conjunction with flexor tendon injury repair; however, rarely, a longitudinal laceration of the digit may cause isolated injury to the retinacular pulley system, and treatment should be considered based on the preservation and / or reconstruction of the A2 and A4 pulleys, as described below.

Closed pulley injuries are rare in the general population, but these have been described more commonly in rock climbers, associated with the high forces placed on the pulley system with the demands of certain climbing maneuvers on the hands, such as with the hanging and crimping positions [28, 29, 56]. In the hanging position, all of the digital joints are resisting force in a flexed position (MCP, PIP, DIP), whereas in the crimp grip position, the DIP joints are hyperextended maximally, the PIP joints are flexed approximately 90°, and the MCP joints are extended. Previous analysis by Lin et al. [14] demonstrated maximum tear load of the A2 pulley to be approximately 400N although antagonistic forces acting on the A2 pulley may exceed these tolerances during the crimp grip position [28, 29, 56].

Nonsurgical Treatment

Typically, isolated, closed pulley ruptures are treated with nonsurgical management, supported by both biomechanical studies and outcomes evaluations [29]. Initial treatment with anti-inflammatory measures, activity restrictions, and emphasis on tendon gliding and range of motion to prevent stiffness or contracture is encouraged. Protective digital taping at the approximate level of the injured A2 or A4 pulley has been advocated in the recovery period, but also with return to strenuous lifting and grasping activities [57].

A case series involving isolated A4 pulley ruptures in the middle fingers of the throwing hands of four baseball pitchers has been reported [19]. In each of the reported injuries, A4 pulley ruptures were confirmed by MRI or dynamic ultrasound and treatment consisted of rest, anti-inflammatory modalities, and return to play in 6 weeks (1 player), 3 months (2 players), and 6 months (1 player). The injury mechanism was described as “repetitive extension force placed on an acutely flexed finger when throwing a fastball.” The authors recommended return to play at between 6 and 12 weeks, “only after painless range of motion and proper rehabilitation of the throwing arm” and avoidance of corticosteroid injection during treatment, due to the potential adverse effects of pulley rupture and delayed tissue healing [19].

Surgical Treatment

Although treatment for isolated flexor pulley injuries is nonsurgical, injuries involving multiple pulley ruptures may require surgical reconstruction in order to restore biomechanical efficiency of the flexor system. Several reconstruction options exist which emphasize the restoration of the biomechanically important A2 and A4 pulleys [58] (Fig. 13.10). Consideration of ideal graft sources, such as an extrasynovial tendon (palmaris, plantaris) or intrasynovial tendon (excised FDS, single FDS slip, or extensor retinaculum) may take into account ease of harvest and resistance to tendon gliding [59, 60]. The A2 pulley reconstruction typically employs a graft passed volar to the extensor tendon apparatus, whereas during A4 pulley reconstruction the graft is passed dorsal to the terminal extensor tendon.

Fig. 13.10
figure 10

Intraoperative photograph demonstrating an A2 pulley reconstruction using the first of two (side-by-side) palmaris longus tendon grafts, secured with a “belt-loop” configuration. (Reprinted with permission: © Leversedge FJ, 2004)

Full size image

Post-Repair Rehabilitation

Postoperative protocols emphasize early, protected independent tendon gliding, avoiding resisted activity that could compromise the pulley repair. Tenodesis should be incorporated into early motion exercises to reduce forces applied to the repaired tissues; preoperative patient education regarding anticipated post-repair rehabilitation methods may improve patient understanding and compliance with therapy. Anti-edema modalities are critical for reducing the work of flexion associated with swelling in the first 3–5 days following surgery [61]. Supportive taping or use of a thermoplastic pulley ring is utilized for all activities for 3 months, and with higher loading activities until 6 months postoperatively.

Summary

In 1948, R. Guy Pulvertaft, a British surgeon, noted that regarding flexor tendon injuries: “it is not difficult to suture tendons and prepare the ground for sound union; the real problem is to obtain a freely sliding tendon capable of restoring good function” [62]. His observation almost 75 years ago highlights the challenges of flexor tendon injuries faced even today. Flexor tendon and pulley injuries in the baseball player present similar challenges to those same injuries in other athletes or non-athletes, however with the added complexity of a condition that influences directly one’s ability to return to play, often conflicting with an obligate period of tendon healing. Advances in our understanding of the biology of tendon injury and repair and the potential application of adjuvant biologic treatments to accelerate tendon healing hold promise for improved therapies. The diagnosis and treatment, and ultimately the outcomes of flexor tendon injuries remain influenced greatly by a comprehensive understanding of pertinent anatomy, the timely recognition and treatment of the condition, and careful patient, training staff, and therapist education and communication in order to reduce the risk of adverse events during the recovery process and to maximize tendon sliding capable of restoring good function.