TENDON DISORDERS IN THE HAND
Trigger finger is the result of localized tenosynovitis of the superficial and deep flexor tendons in the region of the fibrous sheath (annular ligament, or pulley) at a metacarpal head (A1). It occurs most often in the long or ring fingers (occasionally in the thumb) of middle-aged women, but its exact cause has not been determined. Trigger finger may also be associated with rheumatoid arthritis and diabetes involving several fingers.
The localized inflammation causes a thickening and narrowing of the sheath, and a nodular or fusiform enlargement develops in the tendons distal to the pulley. These changes interfere with and may actually prevent the smooth gliding of the tendons through the fibrous sheath.
In the early stage, the nodule produces a slightly painful clicking or grating as it passes through the constricted sheath when the finger is flexed and extended. As the pathologic changes in tendon and sheath advance, flexion of the finger is arrested in the middle range; as more force is required to pull the nodule through the constricted pulley, the finger snaps painfully into full flexion or extension. Later, the tendon nodule may not pass through the stricture, and the finger is partially fixed in extension or flexion, usually the latter. Passive manipulation of the flexed finger may force the nodule through the sheath, producing a painful snap into extension.
On examination, the patient can usually demonstrate the trigger finger and may be able to demonstrate the finger locking in flexion; flexion and extension produce crepitation. Palpation over the metacarpal head reveals a tender nodule that moves with the tendon.
Although trigger finger often subsides spontaneously, a cortisone injection into the tendon sheath may alleviate the triggering in up to 80% of patients. If painful triggering continues, a minor operation can provide permanent relief. A 34 -inch transverse incision is made just distal to the distal flexion crease over the metacarpal head, exposing the flexor tendons and sheath. The constriction is relieved by completely incising the thickened A1 pulley longitudinally along its radial or ulnar aspect, taking care to avoid the digital nerves. The patient can now actively flex and extend the finger freely and comfortably, and the pulley heals again but has a larger diameter.
Flexor Tendon Repair
Flexor tendon injuries can occur by various mechanisms, but the most common injury is a laceration. “Jersey finger” is an avulsion of the flexor digitorum profundus tendon that occurs typically in the ring finger as a result of a forced gripping versus resistance, as seen when the finger gets tied up in an opponent’s jersey during a football tackle. Flexor tendon laceration often occurs in the household on broken glass, from tin can lids, or inadvertently with a kitchen knife. Laceration can occur anywhere along the length of the finger, with the most complex occurring in zone 2 over the proximal phalanx where the profundus and sublimis tendons travel together in a fibro-osseous sheath. Typically, the hand is clenched and therefore the skin injury is more proximal than the tendon injury, requiring careful attention to the physical examination.
Primary repair in the first 6 weeks produces acceptable functional results; after 6 weeks, tendon grafting or arthrodesis of the distal interphalangeal joint is the treatment of choice. Repair of the lacerated or an avulsion flexor digitorum profundus tendon to the distal phalanx is typically performed by using a bone suture anchor placed in the distal phalanx or passage of the locking suture weave placed in the tendon through the bone from palmar to dorsal and tying the sutures over the dorsal cortex. Postoperatively, a dorsal splinting protocol prevents maximal extension during the early phases of healing with early passive motion and active flexion initiated by 3 weeks. Strengthening is begun at the 6-week mark.
Tendon repair is most successful after a sharp laceration of the tendons as opposed to tearing seen with saw injuries. The goal is to obtain a strong repair with the least amount of bulk in the tendon so the tendons will pass smoothly through the pulleys in the fibro-osseous sheath. The flexor tendon repair consists of two layers of sutures. The first layer is a core stitch most commonly performed to obtain four passes across the tendon repair. This provides significant strength to allow early active range of motion. The second layer is a circumferential epitendinous stitch with a fine nonabsorbable suture to help reduce the volume and friction of the repair. Owing to the site of laceration, at times a four-strand repair is not possible and separate two-strand core stitches are placed in each stump and then tied in order to work around the pulleys. A second core stitch can then be placed in a horizontal mattress fashion, providing a total of four core stitches.
Therapy after flexor tendon repair requires highly skilled hand therapists to work closely with patients to reduce edema and guide the patient through the different stages of recovery. The initial stage is typically passive motion to initiate tendon gliding in a safe manner, followed by active range of motion and later strengthening. Full recovery can take up to 6 months, and it is not uncommon that a secondary operative procedure is required to perform a tenolysis to break down the adhesions that occur after wound and tendon healing.