Tendon Injuries and Tendinopathies of the Hand and Wrist



Tendon Injuries and Tendinopathies of the Hand and Wrist


Kendrick Au, MD, MSc

Nina Suh, MD, FAAOS


Dr. Suh or an immediate family member serves as a paid consultant to or is an employee of Shire. Neither Dr. Au nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.





ABSTRACT

Tendon injuries of the hand and wrist can be challenging for surgeons, therapists, and patients. Recent advancements in surgical technique, surgical materials, anesthesia, and postoperative protocols have helped improve patient outcomes. Research continues to focus on maximizing tendon strength and gliding to maximize early motion for all types of tendon injuries. Despite these evolutions, patients should be counseled on the challenging rehabilitation process and imperfect functional results. Tendinopathies of the hand and wrist involve tenosynovitis of the six extensor compartments and stenosing flexor tenosynovitis. These pathologies are often distinguished on a thorough history and physical examination. They generally follow a similar course of treatment, as recent literature continues to provide guidance for optimizing nonsurgical and surgical modalities.

Keywords: early active motion; extensor tendon injuries; flexor tendon repair; tendinopathies


Introduction

Tendon injuries and tendinopathies of the hand and wrist encompass a wide spectrum of pathologies of both the flexor and extensor tendons. Flexor and extensor tendon injuries typically involve a traumatic mechanism that can occur in the presence of a laceration or avulsion. These injuries are often managed surgically and do pose specific challenges given the intricate anatomic and biomechanical considerations. In contrast, tendinopathies of the hand and wrist are often from overuse or inflammatory origins. These conditions can often be successfully managed nonsurgically, with surgical release reserved for patients refractory to nonsurgical measures.


Flexor Tendon Injury


Pathology and Anatomy

The hand contains a total of nine finger flexor tendons: four flexor digitorum superficialis (FDS) tendons, four flexor digitorum profundus (FDP) tendons, and one flexor pollicis longus tendon. The FDS muscle has two heads and originates from the anterior aspect of the medial epicondyle. At the level of the midforearm, the FDS muscle divides to send a deep layer of tendons to the little and index fingers and a superficial layer of tendons to the long and ring fingers. Approaching the insertion on the base of the middle phalanx, the FDS tendon dives deep to the FDP tendon as it splits into a radial and ulnar slip at the Camper chiasm. The FDP muscle arises from the volar and medial aspects of the proximal ulna and interosseous membrane. It travels in the deepest aspect of the forearm to attach to the proximal aspect of the distal phalanx. The flexor pollicis longus tendon originates from the volar aspect of the middle third of the radial shaft and lateral interosseous membrane and attaches at the proximal aspect of the distal phalanx of the thumb. All nine tendons pass through the carpal tunnel in a consistent topography. The FDS tendons to the ring and long fingers are the most superficial, followed by the FDS tendons to the little and index fingers. Immediately beneath them, the FDP and flexor pollicis longus tendons will be found.

The pulley mechanism of the flexor tendon sheath aids in flexor tendon excursion and efficiency. It is composed of five annular pulleys and three cruciate pulleys. The annular pulleys are stiffer and ensure the intimate contact between tendon and the underlying bone is preserved. Recent literature has further supported the existence of an A0 pulley located just proximal to the A1 pulley, composed of transverse fascicular fibers of the palmar aponeurosis, that can be a source of persistent
triggering after an A1 pulley release.1 The thumb pulley system is arranged in a similar fashion, classically containing an A1, A2, and oblique (A0) pulley.

As knowledge of flexor tendon anatomy has evolved, this has facilitated a distinction of five anatomic zones (I through V) for the fingers and three (I through III) for the thumb (Figure 1). Classically zone II has been labeled “no man’s land.” However, anatomic considerations and technique evolutions have challenged the historically poor results of repair in this zone.


Diagnostic Evaluation

The evaluation of a flexor tendon injury should start with a thorough history and physical examination. Careful inspection of patients with a flexor tendon injury may reveal a penetrating wound and loss of the inherent tone of the tendon. This may manifest in the loss of the normal cascade of the hand, with the injured digit assuming a more extended posture. In this circumstance, there may be an absence of the tenodesis effect of digital flexion with wrist extension. When attempting to narrow the diagnosis of tendon injury, the examiner should also isolate each individual tendon during examination. To isolate the FDS tendon, the adjacent digits are held in an extended position while active proximal interphalangeal (PIP) joint flexion is evaluated. During this maneuver, FDP function is effectively blocked as it originates from a common muscle belly. Meanwhile, FDP integrity is evaluated by stabilizing the middle phalanx in extension while distal interphalangeal (DIP) joint flexion is attempted.

Accompanying an examination of each individual tendon, a thorough neurovascular examination should always be performed. The close proximity of the neurovascular bundle puts it at risk in the presence of a flexor tendon injury. A neurologic examination using light touch, static two-point discrimination, and/or monofilament testing is preferred. Capillary refill of the volar digital pulp and nail bed can be used to assess vascularity. A digital Allen test, Doppler examination, or pulse oximetry can also be performed.

For zone I flexor tendon injuries, radiographs are typically obtained to assess for the presence and location of a bony avulsion injury to the distal phalanx.







Tendon Repair

The objectives of flexor tendon repair are to promote intrinsic healing potential, maximize strength, and ensure tendon glide to allow for early active motion to limit adhesion formation. There should be less than 3 mm of gapping at the repair site and the tendon should have well-coapted ends. Apart from these factors, many surgical techniques and materials can be used to bolster the strength and glide of the tendon depending on location of injury and tissue quality.



Zone I

Injury to the FDP tendon can occur from either a laceration or avulsion in this area. An avulsion injury is often referred to as a jersey finger and generally results from a hyperextension mechanism of the DIP joint. The Leddy and Packer classification is commonly used to describe five patterns of FDP avulsion (Figure 2). Type I injuries are the most urgent, as the FDP tendon retracts into the palm and the vincular blood supply of the tendon has been disrupted. These injuries should typically be addressed within 10 days of injury because the tendon can undergo necrosis and myostatic contracture.2 Type II injuries have a small fleck of bone accompanying an FDP avulsion, with tendon retraction to the level of the PIP joint. In type III injuries, there is a large bone fragment attached to the FDP tendon stump that prevents retraction proximal to the A4 pulley. Type IV and V injuries were added to the original classification and describe a separation of the FDP tendon from a bony avulsion fragment and a bony avulsion of FDP with a distal phalanx fracture, respectively. Early exploration of these injuries is often advocated because it can be a challenge to distinguish certain types clinically. However, type II injuries, for example, have been shown to have good outcomes even when repaired 3 months after injury.2

Although it is possible to have an intratendinous rupture enabling an end-to-end repair, avulsion injuries are far more common and require tendon-to-bone reduction. Purely tendinous injuries (types I and II) can be fixed with either a pullout button technique, suture anchors, or suturing over a bone bridge. Classically, the pullout button technique is used and involves core suture placement with the free ends of the suture being passed through the distal phalanx and tied over a sterile button on the dorsum fingernail. The disadvantages of the pullout button construct are the external sutures, nail plate deformity, and higher infection rate. The use of a bone suture anchor offers an alternative that may avoid the associated morbidity associated with the pullout button construct. Clear clinical superiority has not been demonstrated between techniques; however, patients receiving suture anchors have shown to have a quicker return to work.3

Types III through V injuries are less common but are generally managed with open reduction and fixation of the bony fragment. In type IV injuries, the tendon is typically repaired to bone after fixation. Occasionally a dorsal blocking pin may be required to maintain joint congruity.







Zone II

Traditionally repair of tendons in zone II have resulted in poor results. However, changes in surgical technique and postoperative motion protocols have dramatically changed outcomes over the past few decades. Modern surgical principles are anchored in maximizing tendon strength to prevent tendon gap formation while allowing for tendon glide to achieve early active motion. Many clinical decisions and technical factors play an additional role in building strength within a tendon repair. The most studied aspect has been suture technique, with studies to support that a minimum of four core sutures should be used to allow for early active motion.4 There have been many applied techniques to execute four core suture repairs without consensus of a superior technique. Techniques using more than four core sutures have also been described, and although these repairs have superior biomechanical strength, these techniques may require more tissue handling, increased knot burden, and meticulous placement of suture. Regardless of the suture strategy, ensuring that suture purchase is between 7 and 10 mm from the tendon edge, there is a sufficiently sized lock (2 mm in diameter, if used), there is adequate tensioning (10% tendon shortening), and at least 3 knots are thrown for most sutures will also effectively improve repair strength.5,6 Typically, 3-0 and 4-0 suture diameter is the most commonly used. In cyclic loading and linear testing 3-0 suture has been shown to be stronger and as such are generally recommended.7

In an attempt to mitigate suture pull-through, a mesh suture design has recently been studied. It is composed
of multiple polypropylene filaments, and the open braid design allows for a larger suture diameter that collapses on tying, which creates a smaller strand and lower knot profile. According to a 2019 study, mesh repairs had a significantly higher yield and ultimate force required for gap formation in cadaver testing compared with braided poly-blend suture.8 Peripheral epitendinous repairs have been shown to increase strength and reduce gapping to core suture techniques. However, if a strong multistrand repair is achieved, some surgeons have gone without supplemental peripheral augmentation, with positive results indicating it may not be as critical to tendon repair as previously thought.9

Tendon glide after flexor tendon repair can be affected by the major annular pulleys (A2 and A4) and the FDS tendon. In recent years, it has been understood that the A2 pulley can be released up to two-thirds of its length and the A4 can be released entirely without causing clinically significant bowstringing. Recent cadaver research has shown that FDP repairs between the A2 and A4 pulley will slide proximally under the A2 pulley with full active flexion, suggesting A2 pulley venting will be required in these circumstances. The length between the repair and A4 pulley can be used as a guide to the amount of venting of the A2 pulley required for tendon glide.10 In addition, to reduce the diameter of contents passing through the pulleys, some studies have suggested resecting a slip of the FDS tendon or only repairing one slip of FDS in the event of a complete laceration.11,12

Once the repair is completed it is important to evaluate the quality and glide of the repair. This can be done at three separate points when going from full extension to flexion. In full extension the repaired tendon is evaluated for any visible gap formation. Next, as the finger is brought into midflexion, the tendon is examined to ensure adequate glide is achieved. Last, the finger is brought into full flexion to confirm that the repair does not cluster along the pulleys and venting is sufficient.12


Tendon Reconstruction

In a delayed presentation of a flexor tendon injury without tendon retraction, primary repair and satisfactory clinical outcomes may still be achieved. However, in the event of dramatic tissue loss from trauma, neglected tendinous injury involving tendon retraction, or failed tendon repair, primary end-to-end repair of the tendon is generally not possible.13 Heroic efforts to complete an end-to-end repair may risk contracture and quadriga; therefore, tendon reconstruction should be considered. Reconstruction can be accomplished as a single-stage or two-stage procedure, with options of intrasynovial or extrasynovial donor tendons. Prior to proceeding with tendon reconstruction, careful preoperative planning to evaluate for tendon availability and length requirements is needed. The finger should also be supple and free of contracture. When the reconstruction involves an isolated FDP tendon, the intact FDS tendon should not be sacrificed as a donor. The functional satisfaction of an FDS-only finger should be discussed with the patient prior to undertaking the complex process of a tendon reconstruction.

Single-stage reconstruction is a viable option in scenarios with a substantial loss of flexor tendon tissue but with preservation of pulley system and tendon sheath. Staged tendon grafting is more commonly used and allows for the management of concomitant injuries to the surrounding structures such as the pulley system, bone, skin, and neurovascular structures. Under these conditions, a silicone spacer is affixed to the distal and proximal ends of the remaining tendon to create a sufficient space and path within the tendon sheath to allow for eventual passage of a tendon graft during the second stage. As part of the first stage, the A2 and A4 pulleys are typically reconstructed using a graft belt loop reconstruction or shoelace reconstruction.14 Generally, it is advised to wait 6 to 8 weeks prior to commencing the second stage to allow for a formation of a pseudosheath and to regain range of motion prior to grafting. Extrasynovial grafts are commonly used for both immediate or staged reconstruction and include palmaris longus, extensor digiti minimi, and extensor indicis proprius. Traditionally, a Pulvertaft weave technique has been used for the suture technique in combining the graft to the remaining tendon. It offers sufficient strength and stiffness, but does require ample length of donor tendon and considerable diameter of both tendons and results in a relatively bulky repair. Side-to-side suture techniques have been introduced as an alternative method to mitigate some of the challenges with the Pulvertaft weave. There have been various described methods of tendon and suture configuration with the side-to-side technique, but proponents of this technique advocate for its simplicity compared with the Pulvertaft weave. Recent biomechanical studies have also shown that the side-to-side techniques demonstrated a higher load to failure and less bulkiness when compared with the Pulvertaft technique.15,16


Rehabilitation

The advancements in tendon repair have afforded rehabilitation to begin within days after repair completion. The benefits of early motion have subsequently been supported in the literature, showing increasing tendon repair site strength and excursion.17 Early motion
enhances the restoration of the flexion-extension arc and total active motion. To date, there have been various active motion protocols implemented that range from place and hold techniques to true active flexion. A 2019 systematic review demonstrated that the place and hold exercises provided better outcomes than passive flexion protocols, but there currently is insufficient evidence to recommend a specific active protocol.17

Complications of tendon repair can include tendon adhesions, which can be a major factor in the plateau of motion recovery after tendon repair. Tenolysis may be beneficial, but it should only be attempted after at least 3 months following repair and after a thorough trial of appropriate hand therapy. The technical tips described earlier are the best guard against re-rupture of the repair site. However, if re-rupture is encountered up to 3 weeks postoperatively, repeat repair can be attempted. If it occurs outside the 3-week window, the success of a repeat repair is less predictable, and the surgeon should be prepared for reconstructive options.


Extensor Tendon Injuries


Pathophysiology and Anatomy

The extrinsic extensor muscles originate in the forearm and are divided into superficial and deep muscular components. The superficial group includes the extensor carpi radialis longus, the extensor carpi radialis brevis, the extensor digitorum communis, the extensor digiti minimi, and the extensor carpi ulnaris (ECU). The deep group is composed of the abductor pollicis longus (APL), the extensor pollicis brevis (EPB), the extensor pollicis longus, and the extensor indicis proprius. At the level of the wrist, the extrinsic extensor tendons travel through six dorsal compartments on the way to the dorsal hand. At this level, the extrinsic tendons that cross the wrist are responsible for wrist extension. After the tendons course through these fibro-osseous tunnels, they become more superficial and flatter. The complexity increases distally whereby the intrinsic muscles (lumbricals and interosseous muscles) coalesce into the extensor mechanism. The extrinsic tendons traverse the metacarpophalangeal (MCP) joint dorsally and are responsible for MCP extension. However, transverse fibers of the interossei travel volar to the MCP joint axis and are primarily responsible for MCP joint flexion. At the level of the PIP joint, the common extensor tendon trifurcates into two lateral bands and a central slip, whereas the intrinsic muscles also swing inward and contribute to both tributaries. The central slip inserts at the base of the middle phalanx to extend the PIP joint. The lateral bands merge with slips from the intrinsic muscles to form the conjoined lateral bands, which coalesce to form the terminal tendon, inserting at the distal phalanx. The terminal tendon is responsible for DIP joint extension. The knowledge of this complex system can help with understanding diagnoses, treatment, and rehabilitation for these injuries. To help easily identify and guide treatment of these injuries, the extensor mechanism can be divided into eight zones along its course (Figure 3).


Diagnosis and Evaluation

Similar to flexor tendon injuries, suspected extensor tendon injuries should start with a thorough examination.
Open wounds should be evaluated for the size and location of wounds, the resting cascade of the hand should be inspected for loss of posture, and a neurovascular examination should be completed. In patients with a terminal tendon disruption, the DIP is often found in obligate flexion, whereas the PIP may have compensatory hyperextension. Extensor lag of the affected digit may also be noticed in digits at all levels. Wrist and digital motion should also be included in the evaluation, with assessment of each extensor tendon individually so that the juncturae tendinum do not mask an injury. The Elson test is a common special test that is often used in the diagnosis of central slip injuries. The PIP joint is placed in a flexed position, often over the edge of a table, and the patient is asked to extend the PIP joint of the involved finger against resistance. A central slip injury is inferred in the absence of PIP extension with compensatory hyperextension of the DIP, as the intact lateral bands overexert extension force on the DIP joint when attempting to extend the affected digit.






Radiographs of the affected digit can be obtained if osseous injury is suspected. Both static and dynamic ultrasonography may also be used as a clinical adjunct for equivocal examinations.18


Tags:
May 1, 2023 | Posted by in ORTHOPEDIC | Comments Off on Tendon Injuries and Tendinopathies of the Hand and Wrist

Full access? Get Clinical Tree
Get Clinical Tree app for offline access