Background
Flexor tenolysis is a surgical procedure used to remove adhesions that inhibit active flexion of digits. [1, 2, 3] Normal active tendon function requires that flexor tendons be able to glide smoothly within their tendon sheath. Damage to these tendons can necessitate surgical repair, and tendon adhesions can develop despite successful surgical tendon repair, appropriate postoperative management, and compliance with physical therapy. [4]
The exact etiology of tendon adhesions following surgery is unclear, but it appears to be due to scarring between the damaged surfaces of both the tendon and the tendon sheath when the tendon is immobilized. [5]
The classical paradigm including inflammation, proliferation, synthesis, and apoptosis appears to be at work, but cellular activity has been shown to be greater in the surrounding tendon sheath. [3] Initially, the adhesions were thought to be the source of reparative cells, nutrients, and blood supply to the tendon, but that opinion fell out of favor. [6] Subsequent investigations revealed that healing of tendons could occur in the absence of tendon adhesions and thereby helped to elucidate the presence of a population of cells inside the tendon capable of repair. [7]
As far back as the 1960s, tendon immobilization was shown to be critical to adhesion formation. [8, 9] Subsequent investigations mapped out the phases of repair that occur separately in both the tendon and surrounding synovial sheath and showed that the healing phases are more robust and prompt in the sheath than in the tendon body. [3]
Indications
Any surgery of the flexor tendon anatomy should only be undertaken if the patient is willing to commit to a rigorous course of physical therapy. In addition, the patient must have the following:
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Intact alignment of skeletal structures, including bones, ligaments, and tendons, with no underlying arthrosis
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Stable, mature scarring evident over all wound areas
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Good strength in flexor and extensor muscles of the hand, as well as intact nerves to flexor muscles
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Good passive range of motion (ROM) of affected tendons
Clinically, tenolysis is frequently offered if after a prolonged period of immobilization, passive flexion noticeably exceeds active flexion or if the patient exhibits a fixed contracture at a proximal interphalangeal (PIP) joint. [4] The exact period prior to undergoing tenolysis is up for debate, and every patient is unique, but it is generally accepted that flexor tenolysis is recommended after the patient has concluded passive and active ROM exercises for at least 3 months and has reached a plateau of progress. [3]
Contraindications
Tenolysis is absolutely contraindicated in patients with active infection, motor-tendon problems secondary to denervation, and unstable underlying fractures requiring fixation and immobilization.
Relative contraindications include extensive adhesions, immature previous scars, and severe posttraumatic underlining arthrosis.
Technical Considerations
Anatomy
Two tendons contribute to active flexion of a finger: the tendon from the flexor digitorum profundus (FDP) muscle and the tendon from the flexor digitorum superficialis (FDS) muscle (see the image below). Both tendons attach to each finger. Both are enclosed within an enclosed tendon sheath called a theca. The tendons connect the muscle bodies in the forearm with the fingers in the hand, passing through the carpal tunnel at the wrist.
Flexor tendons with attached vincula. FDS, flexor digitorum superficialis; FDP, flexor digitorum profundus.
Tendons from the FDS insert on the base of the middle phalanx of each finger to flex the finger at the metacarpophalangeal (MCP) and PIP joints. The FDP inserts into the base of the distal phalanx and flexes the finger at the MCP, PIP, and distal interphalangeal (DIP) joints. Not all fingers are capable of independent movement in every individual, because the tendons from the FDP are usually connected proximal to the individual fingers, the only common exception being the tendon to the index finger.
An elaborate system of pulleys is in place to prevent “bowstringing” or elevation of the tendon away from the palmar surface of the wrist during active flexion. The tough membrane that prevents this at the wrist is called the flexor retinaculum of the hand, and the tunnel for the tendons beneath is called the carpal tunnel.
At the fingers, there are various anular or cruciate ligaments that perform a similar task by preventing the tendons from elevating. The precise number of anular or cruciate ligaments in each finger can potentially vary from individual to individual, but commonly, there are three or four cruciate ligaments (C1-C4, proximal to distal) and four or five anular ligaments (A1-A5, proximal to distal).
The first anular pulley, A1, lies at the head of the metacarpal bones, whereas the second through fifth anular ligaments, A2-A5, all attach to the bones on the finger. The cruciate ligaments generally are smaller than anular ligaments and are found between anular ligaments. Together, the cruciate and anular ligaments make a tunnel through which normally the flexor tendons pass.
Outcomes
Flexor tenolysis is a highly individualized procedure; consequently, reports of how much active flexor ROM increases after tenolysis vary widely. It has been reported that active ROM increases for between 59% and 90% of all patients. [10]
Breton et al evaluated the increase in active ROM and the incidence of complications in 60 patients (75 fingers) who underwent flexor tenolysis in zone 2, with or without dorsal tenolysis or PIP arthrolysis. [11] The mean increase in total active motion for patients undergoing tenolysis only was 60°, compared with 90° in those undergoing tenolysis with arthrolysis. At 6 weeks, 23% of cases had excellent functional outcomes, 47% had good outcomes, 20% had average outcomes, and 10% had poor outcomes.
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Flexor tendons with attached vincula. FDS, flexor digitorum superficialis; FDP, flexor digitorum profundus.
