Flexor Tendon Rehabilitation
The ultimate goal of flexor tendon repair is to restore normal digital function. Historically, repaired flexor tendons were treated with immobilization (161). This produced a strong repair but also led to uncontrolled tendon adhesion, loss of tendon gliding, secondary joint contracture, and unsatisfactory digital function.
Scientific and clinical research since this time has demonstrated the beneficial effects of applying early controlled stress to the healing tendon (43,45,49,160,176). Mobilized tendons gain greater tensile strength, form fewer adhesions, and have better excursion, resulting in improved digital function.
Rehabilitation programs that employ early motion principles have almost invariably replaced immobilization and can be broadly categorized into three groups: passive flexion/active extension, passive flexion/passive extension, and active flexion/active extension.
Passive Flexion/Active Extension
The first results of early passive motion were reported by Kleinert and associates (38). Good to excellent results were achieved in 87% of cases using a postoperative technique of passive flexion and active extension of the repaired digit (39).
After carefully controlled surgical repair, patients were placed in a dorsal forearm based splint with the wrist flexed to 20° short of full flexion, the metaphalangeal (MP) joints in 40° flexion, and the interphalangeal joints fully extended. Rubber band traction was applied to the tip of the injured digit and pulled toward a fixed point on the forearm (Fig. 3). During exercise, the patient actively extended against the rubber band, which passively returned the digit to a posture of flexion. The splint was discontinued after 6 wk, at which time gentle active flexion exercises were commenced.
The Kleinert concept of passive controlled motion using rubber band traction has remained among the most popular methods of rehabilitation, but many modifications to the original regimen have been introduced (Fig. 4). Wrist flexion has been reduced to neutral, lowering the tensile load at the repair site (177). MP flexion has been increased to 90°, facilitating the action of the intrinsic musculature in extending the interpha-langeal (IP) joints (161). A palmar pulley has been added to redirect the line of pull of the traction toward the palm, increasing DIPJ flexion and improving FDP excursion at this joint (178,179). All four digits are placed in rubber band traction, reducing restriction on tendon glide caused by adjacent digits not brought into full flexion (180).
The complication of PIPJ flexion contracture, seen as a result of the sustained flexion digit posture in the splint, has been addressed in several ways. First, patients are encouraged to manually reduce rubber band tension to allow full active IP joint extension during exercise sessions. Second, traction is reduced or disconnected during sleep.
Exercise parameters have remained largely unchanged despite the numerous splint modifications. Patients are instructed to perform 10 active extension exercises each waking hour, and the splint is worn for 6 wk. After this, active movement is commenced. Return to full activity is not advised until 10-12 wk postoperatively, but reducing the postoperative period to 8 wk has not been found to be detrimental (181).
Passive Flexion/Passive Extension
An alternative method of rehabilitation that incorporated the concept of early motion was described by Duran and Houser (159). Immediately following repair, the patient was placed in a dorsal forearm-based splint that extended to the proximal phalanges but did not include the PIPJs. The wrist was held in 20° flexion. Rubber band traction was applied to the injured digit and fixed to the distal forearm (Fig. 5).
Unlike the previously described programs, the rubber band traction was removed for exercises performed twice daily and consisted of six to eight repetitions of passive digital motion, designed to maximize differential tendon glide (Fig. 6). The dorsal splint was removed at 4.5 wk, and the rubber band was attached to a wrist cuff. Passive
Fig. 5. Dorsal-blocking splint used for the passive flexion/passive extension protocol. The splint extends to the proximal phalanx and holds the wrist in 20° flexion.
motion was continued and active extension commenced. The rubber band traction was discontinued at 5.5 wk when active motion was permitted.
Although Duran and Houser's (159) original passive motion protocol is now rarely followed in its entirety, passive digital motion is frequently incorporated into current dynamic traction programs, and the more recently devised active motion programs.
Active Flexion/Active Extension
Excellent results using passive motion protocols have not been universally achieved (182,183). This has raised doubts about the ability of passive digital motion to produce adequate excursion at the repair site, particularly in the presence of postoperative hematoma and edema (122,165). The addition of an active component to postoperative mobilization has increased the excursion of tendon repair (184,185).
These findings have led to the development of early active mobilization programs. However, the force generated by active muscle contraction is not easy to control, and the challenge of such programs has been in maximizing tendon excursion without exceeding the tensile limit of the repair.
Early reports of active motion protocols demonstrate favorable motion outcomes but unacceptably high rates of rupture (51,52,54,55,186). Ruptures may be attributable to the use of repair techniques inadequate to withstand the tensile demands of active motion, which is discussed previously in the section on tendon repairs.
In a typical program (187), the patient is placed in a dorsal protective splint with the wrist in neutral, MP joints in approx 40° flexion, and the IP joints extended. Therapy is commenced 48 h postoperatively to allow time for the resolution of edema, which may otherwise increase the resistance to tendon glide during active motion and contribute to repair site deformation.
Under therapist supervision, the splint is removed, the wrist is placed in 20° extension to reduce the work of flexion, and the patient is asked to gently actively flex the fingers through a limited range of motion over approx 10 repetitions. Flexion efforts are alternated with passive digital flexion; active digital extensions are with the wrist in modest flexion.
The patient is seen two to three times a week and supplements therapy sessions with a home exercise program of passive digital motion within the splint. Active motion may be added to the home exercise program after the first session (188), or delayed for up to 3 wk (187). Treatment is progressed by the addition of place and hold exercises in wk 2, active fist making in wk 4, and light pick-up activities in wk 5. The splint is discontinued after the fifth postoperative week and light-resisted activities are introduced at wk 6.
The extensor tendons' contribution to the balance, power, dexterity, and range of hand activities is fundamental, but injury to the extensors is often regarded as less serious than injury to the flexors (189). This attitude is reflected in the convention of managing extensor injuries with postoperative immobilization. The extensor tendons proximal to the extensor retinaculum are broad and flat, with a relatively high tendon-to-bone interface, making them prone to peritendinous adhesion when immobilized after injury. Long-term complications, such as extensor lag and loss of digital flexion, have been observed as a result of static immobilization of repaired extensor tendons (190). Efforts to prevent adhesion and restore the normal gliding function of repaired extensor tendons have seen the development of postoperative programs incorporating the concepts of early motion, thus effective in the management of repaired flexor tendons (38,39,43,45,49,160,161,176).
The anatomical and biomechanical characteristics of the extensor tendons vary from their origin in the distal forearm to their insertion into the terminal phalanx. Therefore, a single postoperative program would be unsuitable to adequately treat all levels of injury.
Rehabilitation programs will be described for each zone, following on from the discussion previosly in section "Extensor Tendon Repairs."
A disruption of the conjoined lateral bands in zone I results in an extensor lag at the DIPJ. The deformity is commonly referred to as a mallet finger. Injuries may be closed or open.
Treatment of the closed injury involves immobilization of the DIPJ in extension or slight hyperextension. This may be achieved by the application of a suitable splint. Prefabricated plastic splints are available for this purpose and have been found to be highly effective (Fig. 7; 191,192).
More commonly, a custom-molded thermoplastic splint is applied to the digit to ensure an exact fit. The splint extends from the tip of the finger to the PIPJ and may be placed dorsally, volarly, or in the design of the prefabricated styles circumferentially. The dorsal splint (Fig. 8) has the advantage of allowing unrestricted PIPJ flexion (191,192) and interferes the least with sensory feedback from the finger tip during hand function. It is customary to splint the DIPJ in some hyperextension, but care must be taken to avoid pressure necrosis of the dorsal skin from a position of extreme hyperextension (193).
The splint is worn continuously for a period of 6-8 wk, then for a further 2 wk at night (191,194,195). During the final 2 wk, additional splint-weaning measures may be employed. The patient may be instructed to apply the splint during the day if a lag is observed and leave the splint in place until the next day. Alternatively, a sling of strapping tape may be applied to gently support the DIPJ in extension.
Splint treatment is effective in restoring or improving extension in 50-75% of cases (194,196,197). The remainder have persistent extensor lag and/or loss of terminal joint flexion (198). Gradual reduction of extensor lag has been observed in the months following treatment as the scar tissue bridging the extensor defect contracts (195). While it is recommended that splinting of the mallet finger be initiated as soon as possible after injury, splinting has been shown to be beneficial even after delay in commencing treatment (199,200).
Open injuries may be satisfactorily treated in the same manner as the closed injury. Alternatively, a longitudinal K-wire can be placed through the extended DIPJ at the time of repair (201). The wire is removed at 6 wk, and a night splint is worn for a further 2 wk. No difference has been found in the outcome between Stack splintage and K-wire fixation (202).
Injuries from disruption of the lateral bands in zone II are splinted in the same manner as for zone I. In the case of a single lateral-band injury, the digital extension splint is usually removed at 10-14 d, and active movement is resumed (192).
Disruption of the central slip in zone III results in a loss of active extension at the PIPJ, and associated hyperextension of the DIPJ. The consequent posture is referred to as a "boutonniere deformity," thus named because of the apparent "button-holing" of the PIPJ between the volarly displaced lateral bands in the space created by the injured central slip. The injury can be closed or open.
Empirically, the boutonniere deformity (either open or closed) has been treated by 4-6 wk of immobilization in a static PIPJ extension splint (203,204). The DIPJ is kept free to allow active and/or passive movement to prevent adhesions of the lateral bands and contracture of the oblique retinacular ligaments.
Results of treatment by immobilization are frequently disappointing, particularly after complex and open injuries. Characteristic extensor lag and loss of flexion of the IP joints are attributable to extensor tendon adhesion at the proximal phalanx (190,196,205).
To reduce tendon adhesion and improve outcome, early controlled motion programs for open zone III injuries have been developed. Both passive (206-209) and active (210) controlled motion programs have been described. Both are initiated within 5 d of repair.
The passive motion program reported by Crosby and Wehbe (204) requires the application of a dorsal, hand-based dynamic splint that holds the MP joints in neutral. Rubber band traction provides passive PIPJ extension (Fig. 9). The patient is instructed to flex the finger through a limited range of 30°, 10 times every waking hour in the dynamic splint. The splint is discontinued after 4-6 wk when active motion is commenced.
The active motion program, termed "short-arc motion" (210), uses a series of static digital splints for rest and exercise (Fig. 10). When not exercising, the involved digit is immobilized in extension in a static volar digital splint. The immobilization splint is removed every waking hour to allow 20 repetitions of PIPJ flexion through a range of 30°, guided by the first exercise splint. A second exercise splint is used to support the PIPJ in extension, whereas the DIPJ is flexed 20 times through an unrestricted range of motion.
If no lag develops during the first 2 wk of treatment, the first exercise splint is altered to allow 40° of PIPJ motion in the third postoperative week and 50° during the fourth. Splinting is discontinued 4-6 wk postoperatively. During exercise, the wrist is positioned in 30° of flexion, and the MP joint is supported in 0° of flexion to reduce the workload on the EDC throughout the activity.
Fig. 9. A hand-based dynamic splint for zone III extensor tendon injury. The splint allows active PIPJ flexion, and the rubber band traction provides passive PIPJ extension.
Disruptions to the extensor tendons in the region extending from the proximal phalanges to the wrist have been empirically managed by postoperative immobilization (211). Techniques of early passive mobilization and, more recently, controlled active mobilization (212-214) have yielded improved outcomes.
Following exploration and repair, the forearm is immobilized in a volar splint (Fig. 11) with the wrist in approx 40° extension, the MP joints in 0-20° of flexion, and the IP joints extended. The splint is discontinued after 3 wk, and standard rehabilitation techniques follow to restore maximum active range of motion.
Within the first five postoperative days, a dorsal forearm-based dynamic extension splint (Fig. 12) is applied with the wrist in 20-40° extension. Rubber band traction
Fig. 13. Static volar splint for controlled active motion. The splint allows active MP joint flexion to 45°. IP joint flexion is unrestricted.
holds the MP joint in extension. The patient is instructed to actively flex the MP joints 10 times every hour, with the traction device passively extending the joint to neutral. The range of flexion is initially limited to 30° by a blocking device, which is progressively adjusted each week to allow an increased range of flexion until the splint is removed at 6 wk.
During the first three to four postoperative days, a palmar blocking splint (Fig. 13) is applied, in which the hand rests in 30° and the MP joints in 45° flexion. The IP joints are unsupported and able to move freely.
The patient is instructed to actively flex and extend the MP and IP joints simultaneously within the confines of the splint 10 times every hour. MP extension is limited to neutral during the first 2 wk. In the third week, the MP flexion block is increased to 70° and hyperextension exercises of the MP joints are added. The splint is discontinued after 4 wk.
No difference exists in the outcome between dynamic extension splinting and controlled active mobilization in patients with simple extensor tendon injuries in zones V and VII. Therefore, controlled active mobilization is recommended in this patient group, as it is simpler, cheaper, and requires less therapy time.
In practice, dynamic splinting remains the preferred treatment for multiple tendon lacerations, complex injuries involving damage to underlying bone or joint, or injuries associated with a loss of dorsal skin.
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