Diagnosis and Pathology

Traumatic injury to the extensor tendons may be by open or closed means. Open lacerations most often occur from a sharp object lacerating the extensor tendon. Open injuries are diagnosed at the time of injury as the wound is explored for tendon, nerve, and ligament damage. Injury to the tendon can vary from a partial to complete laceration or loss of tendon length, from clean to dirty, or from a straight cut made by a sharp edge to a jagged, rough surface. Associated injury to the extensor retinaculum, sagittal bands, bone, ligament, nerve, or vessel may have occurred, or a crushing force may increase the complexity of injury. Repair of the tendon and associated structures is performed as soon after the injury as possible, often in the emergency room.

Closed traumatic injuries of the extensor tendon may occur as a rupture of the tendon from its attachment, from friction of the tendon across a rough bony prominence, or from disease that weakens the tendon, such as rheumatoid arthritis. Closed extensor tendon injuries in the digit include mallet and boutonniere injuries. Rheumatoid arthritis can cause synovial invasion of an extensor tendon, often at the level of the wrist, eventually resulting in its rupture. Closed extensor tendon ruptures also occur at the wrist by friction of the tendon over a bony prominence, such as an extensor pollicis longus (EPL) rupture over Lister’s tubercle, or extensor digiti minimi (EDM) rupture over a rough edge of the distal ulna.

This chapter focuses on surgical repair, postoperative healing, and rehabilitation approaches following extensor tendon repair. Closed injuries to the tendon that do not require surgical repair (such as, mallet and boutonniere injuries) are discussed in Chapter 29.

Surgical Repair of Extensor Tendons

Less attention has been given to the types of surgical repair for extensor tendons than flexor tendons. However, the strength of repair of an extensor tendon is important in preventing gapping or rupture when motion is initiated. A number of suture techniques for extensor tendons exists.1,2,12,13 Newport notes that because extensor tendons are smaller and flatter than flexor tendons and have less cross linking, performing a stronger, multi-strand repair in the extensor tendon is more difficult. The same repair technique performed in an extensor tendon is approximately 50% as strong as if it was performed in a flexor tendon due to the smaller size of the tendon and lack of collagen cross linking.^1,13 The type of suture performed on the lacerated extensor tendon is largely dependent on the area the tendon was injured. The thinner area of extensor tendon (such as, in the digit) will not tolerate multiple strands required for stronger repair.¹ The therapy protocols discussed in this chapter for extensor tendon injury are not dependent on the type of surgical technique used.

Precaution. The therapist must know, however, whether the surgeon considers the repair to be sufficiently strong to tolerate immediate motion protocols before considering their use.

Timelines and Healing

Healing of tendons occurs from direct blood supply and synovial diffusion. The blood supply to the extensor tendons is through vascular mesenteries, which travel through the fascia to the tendons from the radial and ulnar arteries and deep palmar arch. Nutrition from synovial diffusion to the extensor tendons occurs from the deep fascial layer in the dorsum of the hand and the extensor retinaculum.¹

Three basic approaches to rehabilitation of the repaired tendon in the hand are 1) immobilization, 2) immediate passive motion in the direction of the repaired tendon, and 3) immediate active motion in the direction of the repaired tendon. The main difference in these approaches is within the early phase, or first month, of tendon healing.

The early phase of tendon healing consists of the inflammatory phase and early fibroplasia phase of tendon healing when the tendon is at its weakest and collagen is just beginning to be laid down at the repair site. This phase is also the time when adhesions begin to occur. The intermediate phase of tendon healing includes the period from 3 to 4 weeks to approximately 7 to 8 weeks after repair, during which time the tendon repair gains tensile strength. The late phase of tendon healing includes the period from 7 or 8 weeks to 12 weeks after repair. During this period, the tendon repair continues to gain tensile strength and begins to remodel in alignment with the tension placed on it. The repaired tendon is considered to have nearly full tensile strength at 12 weeks after the repair. Tissue remodeling continues for a number of months.

Most clients who have had an extensor tendon injury and repair are allowed to use their hands functionally by 6 to 8 weeks following repair. The reason for this is that although normal use of the hands consistently offers resistance to the flexor tendons, it rarely offers resistance to the extensor tendons.

Precaution. Although allowed to use the hand functionally, exercises designed to offer resistance to the extensor tendon should be deferred until the tendon is fully healed to prevent rupture.

Knowledge of tendon healing is the basis for determining safe advancement to resistive exercises of the repaired tendon. This is an important concept to understand. This guideline affects clinical decisions about strengthening of grip or pinch following a flexor tendon repair or applying resistance to digital extension, following an extensor tendon repair. Resistance is introduced appropriately to motion of a tendon when adhesions limit active motion more than passive motion in an effort to place tension on the scar to improve proximal gliding of the tendon. This same resistance, however, may overcome the tensile strength of the repair and result in a rupture. Good active motion of the repaired tendon indicates lack of adhesions that would prevent proximal gliding of the repaired tendon. Tension develops in the tendon when the muscle pulls again added resistance. Without the support and restriction of surrounding adhesions, all this tension is transferred directly through the tendon, and the risk of tendon rupture greatly increases when resistance is introduced. Thus all timelines in this chapter must be individualized, and progression to resistance of the repaired tendon that is showing good to excellent gliding is done at the later of the timelines discussed or is deferred until the referring surgeon determines the tendon is near or at full tensile strength.

Precautions for Minimizing Tension on a Repaired Extensor Tendon

Tendon repairs are never at their full strength when motion is initiated. The precaution always exists regarding gapping or potential rupture of a tendon until 12 weeks after repair. Two things cause gapping or rupture of a repaired tendon. The first of these is overstretching of the extensor tendon repair by moving too far into flexion (pulling the tendon repair apart) before the tendon is strong enough to tolerate the amount of tension placed on it. The second is an excessive internal pull on the tendon by the muscle during active or resisted motion in the same direction as the repaired tendon. This would include active or resisted extension following an extensor tendon repair before the tendon is strong enough to tolerate that amount of internal tension on the tendon.

Precaution. When initiating active motion, do it gently with a gradual increase in tension applied to the tendon as healing advances.

As we encourage tendon gliding for active motion, we must consider the amount of tension the muscle is placing on the repaired tendon to achieve the active motion. Our goal in tendon rehabilitation is to achieve tendon gliding while minimizing tension on the repair during the healing process. We can minimize resistance or tension on the tendon when mobilizing the tendon by decreasing edema and joint stiffness, performing motion slowly and gently, and using optimal positions of proximal joints during active motion. When we mobilize stiff joints associated with the tendon repair in the first 6 weeks after repair, we must do it with the tendon in a protected position.

For instance, if the PIP joint is stiff following an extensor tendon injury over the dorsum of the hand at 3 weeks after repair, support the wrist and metacarpophalangeal (MP) joint in extension while applying gentle joint mobilization or passive proximal interphalangeal (PIP) flexion. This will prevent overstretch of the repaired extensor tendon while improving flexion of the individual joint.

Anatomy

Extrinsic extensor tendons to the digits include the extensor digitorum communis (EDC), extensor indicis proprius (EIP), EDM, EPL, extensor pollicis brevis (EPB), and abductor pollicis longus (APL). Each of these tendons crosses the wrist dorsally, passing under the extensor retinaculum, which is separated into six compartments to maximize mechanical efficiency of the extensor tendons as they cross the wrist, preventing bowstringing (Fig. 31-1).

Proximal to the MP joints, the juncturae tendinum fibers separate from the EDC tendon, providing a cross-connection to the adjacent EDC tendon. This cross-connection of fibers exists to a variable extent in each individual but most consistently occurs between the EDC to the ring finger and the EDC tendons to the small and middle fingers. The juncturae tendinum fibers assist in extension of the neighboring finger and help maintain the EDC in midline over the metacarpal head during finger flexion.

The extrinsic extensor tendons serve the primary purpose of extending the MP joints of the fingers and the thumb MP and IP joints. The EDC also assists in extension of the finger IP joints by its anatomic contribution to the lateral bands and weakly by its attachment on the proximal portion of the middle phalanx.

Extension of the finger PIP and distal interphalangeal (DIP) joints is performed primarily by the lateral bands, which consist of portions of the lumbrical and interossei tendons with contributions from the EDC (Fig. 31-2). The lateral bands on both sides of the fingers pass dorsal to the axis of motion at the PIP and DIP joints and merge over the DIP joint to form the terminal extensor tendon. Extension at the PIP and DIP joints is delicately balanced by a combination of tendon fibers and ligamentous support in an uninjured finger to prevent excessive dorsal or volar migration (subluxation) of the lateral bands. The transverse retinacular ligament (TRL) supports the lateral bands volarly, and the triangular ligament supports the lateral bands dorsally. The oblique retinacular ligaments (ORLs) run along the sides of the finger and cross the PIP and DIP joints volar to the PIP axis of motion and dorsal to the DIP axis of motion. Thus when the PIP joint extends, it places tension on, or stretches, the ORL. This causes the ligament to tighten across the DIP joint, placing a passive extension assist on the DIP joint by this tenodesis effect.

The IP joint of the thumb is extended primarily by the EPL tendon, and the MP joint is extended by a combination of the EPL and the EPB. The APL, EPB, and EPL tendons extend the carpometacarpal (CMC) joint.

Injuries to the extensor tendon are discussed in relation to the zone of injury, for there are different protocols following repair of the extensor tendon for each set of zones. Extensor tendon zones are reviewed in Fig. 31-3. Orthoses used for extensor tendon repairs in the early phase of tendon healing are reviewed in Table 31-1.

TABLE 31-1

Overview of Orthoses Used for Extensor Tendon Repairs in the Early Phase of Tendon Healing

Zone of Injury	Immobilization	Immediate Passive Extension	Immediate Active Extension
I and II	DIP extension orthosis (see Fig. 31-4)	None available	None available
III and IV	Finger gutter, full IP extension, taped in place (see Fig. 31-5)	Hand-based outrigger allowing 30° of PIP flexion (see Fig. 31-6)	Finger gutter, taped in place between exercises (see Fig. 31-5) Exercise template with 30° of PIP flexion, 20° of DIP flexion (see Fig. 31-7)
V, VI, and VII	Full-length resting pan in partial wrist extension and full digit extension or slight MP flexion (see Fig. 31-8)	Dynamic MP extension outrigger allowing 30° of MP flexion (see Fig. 31-9, A and B) Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Related Related posts: Some Thoughts on Professionalism Perspectives on Pain Tissue-Specific Exercises for the Upper Extremity Ganglions and Tumors of the Hand and Wrist Flexor Tendon Injury Peripheral Nerve Problems Stay updated, free articles. Join our Telegram channel Join Tags: Fundamentals of Hand Therapy Clinical Reasoning and Treatment Gu Sep 9, 2016 | Posted by admin in MANUAL THERAPIST | Comments Off on Extensor Tendon Injury Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access