Flexor Tendon Injuries

FLEXOR TENDON INJURIES: PRINCIPLES OF MANAGEMENT

 

Flexor Tendon Zones(Verdan zones)

•    Zone I extends from just distal to the insertion of the sublimis tendon to the site of insertion of the profundus tendon.

•    Zone II is in the critical area of pulleys (Bunnell’s “no man’s land”) between the distal palmar crease and the insertion of the sublimis tendon.

•    Zone III comprises the area of the lumbrical origin between the distal margin of the transverse carpal ligament and the beginning of the critical area of pulleys or first annulus.

•    Zone IV is the zone covered by the transverse carpal ligament.

•    Zone V is the zone proximal to the transverse carpal ligament and includes the forearm.

 

• The flexor tendons are covered by a thin visceral layer of adventitia, or paratenon.
• The tendons enter a synovium-lined fibro-osseous tunnel at the base of each digit that provides both a biomechanical advantage (on the basis of the pulley system) and a source of tendon nutrition (from the parietal and visceral layers of paratenon).

There is an arrangement of five annular pulleys and three cruciform pulleys in the finger.

1)      The A1, A3, and A5 pulleys originate from the palmar plates of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints, respectively.

2)      The A2 and A4 pulleys are continuous with the periosteum of the proximal aspect of the proximal phalanx and of the middle third of the middle phalanx, respectively.

3)      The cruciform pulleys are thin and compliant; they are located between the A2 and A3 pulleys (C1), between the A3 and A4 pulleys (C2), and between the A4 and A5 pulleys (C3).

 

 

 

 

 

 

 

EXAMINATION

Injured finger is stabilized for obtaining specific joint movements.

1)      When proximal interphalangeal joint is stabilized, inability to flex distal interphalangeal joint suggest injury to the flexor digitorum profundus

2)      Stabilizing metacarpophalangeal joint inability to flex both proximal and distal interphalangeal joint suggest injury to both flexor tendons.

3)      To evaluate injury to flexor digitorum superficialis keep the adjacent fingers in complete extension. Inability to actively flex the injured finger suggests injury to flexor digitorum superficialis.

For checking the integrity of thumb flexors – flexor pollicis longus tendon, the metacarpophalangeal joint of the thumb is stabilized. If the flexor pollicis longus tendon is divided, flexion at the interphalangeal joint is absent.

SURGICAL REPAIR

Tendon healing occurs through extrinsic (activity of peripheral fibroblast) and intrinsic mechanism (activity of fibroblast derived from tendon). It occurs in three phases

1)    Inflammatory (48 to 72 hours)

2)    Fibroblastic (5 days to 4 week)

3)    Remodelling (4 week to 3.5 months)

Strickland six characteristics of an ideal tendon repair:

(1) easy placement of sutures in the tendon,

(2) secure suture knots,

(3) smooth juncture of tendon ends,

(4) minimal gapping at the repair site,

(5) minimal interference with tendon vascularity, and

(6) sufficient strength throughout healing to permit application of early motion stress to

the tendon.

 

Urbaniak Classification of suture configuration for tendon repair

•    Group 1 suture applies shearing force to tendon ends parallel to collagen bundles and results in weak repair.

Eg: Simple sutures

 

•    Group 2: longitudinal pull of suture is converted to either oblique or transverse compressive force on tendon and strength of repair approaches strength of suture material.

Eg: Bunnel suture, Kessler suture

 

•    Group 3: strongest union, loading of tendon applies compressive force of tendon to tendon at right angles to longitudinal shearing forces.

Eg: Pulvertaft repair (Fishmouth suture).

 

Principles of flexor tendon repair:

 

• Flexor tendons should be repaired at whatever level they are severed
• Whenever possible the repair should be done primarily. When delayed a tendon graft may be required

• A2 and A4 annular pulley areas of flexor sheaths should be preserved – prevents tendon bowstring and flexion deformity and excursion of tendion is preserved.
• Tendon laceration of 60% or more is treated as a complete transection.
• Laceration less than 60% is evaluated for the risk of triggering. If triggering is seen, the flap of tendon is smoothly débrided, and the flexor sheath is repaired to help avoid entrapment or triggering of the flap in the defect in the flexor sheath.

• Four to 6 strands is optimal. Strickland modification of the Kessler’s technique is the standard.
• Initially the dorsal epitenon sutures are placed, then the core sutures and then finally the volar epitenon sutures
• The diameter of suture is also directly proportional to the strength of the repair; 3.0 or 4.0 caliber nonabsorbable suture is recommended.
• Locking suture technique does not increase repair strength.
• Failure of the repair frequently occurs at the knot.
• Repair supplemented with a running circumferential epitendon suture technique increases the strength of the core stitch up to 50% and minimizes gapping.
• Suture technique must withstand gap formation of 3 mm at the repair site during the initial 3 weeks following repair.

Zone I:

• Contains only the FDP tendon
• The tendon may be directly repaired if the distal stump is large enough, or it may be reinserted to bone(preferably)
• Sutures(using Keith needles) through the tendon and through the bone are brought out over the dorsal aspect of the nail and tied(alternatively use a pull out button technique)
• Care must be taken not to advance the tendon more than 1 cm
• The finger cascade: Excessive trimming and advancement of the profundus tendon leading to flexed position of finger compared with other fingers.
• Quadriga effect: uneven tension applied to the common muscle belly of the flexor profundus tendons due to advancement of tendon leading to limited flexion of the remaining profundus tendons

Zone II:

• When both the superficialis and profundus tendons are divided, it is preferable to repair both tendons because greater digital independence of motion may be achieved
• Repair of  FDS and FDP also diminishes the likelihood of proximal interphalangeal joint hyperextension deformity
• Core suture with two or more strands, locking component and buried knots is preffered.

• Care should be taken when the flexor sublimis has been injured in the area just proximal to the proximal interphalangeal joint and distally where the orientation of the proximal and distal portions of the tendon can be misinterpreted and repairs may be incorrectly done with the sublimis slips malrotated.
• Care also should be taken to deliver the flexor profundus tendon through the split portion of the flexor sublimis when the profundus tendon has retracted proximally.
• 18 to 25% of patients with flexor tendon repair requires tenolysis.

Zone III:

• Results are better because of the absence of the fibro osseous sheath

Zone IV:

• The area beneath the transverse carpal ligament, a z-lengthening release and repair of the transverse carpal ligament should be performed to prevent flexor tendon bowstringing

Zone V:

• Involving the musculotendinous junction are difficult to repair because muscle tissue will not hold suture. May necessitate multiple mattress sutures

Postoperatively:

–        The wrist should be immobilized at approximately 10 degrees of flexion, the MCP joints at approximately 70 degrees of flexion, and the IP joints at neutral

–        A program of passive ROM exercises should be initiated that decreases the adhesions at the repair site and enhances intrinsic tendon repair

–        At 4–6 weeks following repair, active flexion and extension exercises are allowed as splinting is discontinued.

–        At 6–8 weeks, passive extension exercises and isolated blocking is encouraged.

–        After 8 weeks, the patient may begin flexion against resistance

–        With four-strand techniques in an intelligent compliant patient active motion can be begun earlier for zone I and II injuries

Passive ROM protocols:

Klienert traction	Duran Traction
Prevents patients from moving their digits against resistance	Uses a protective splint, but no elastic bands
Maintains the digits in a protective fashion	Passive flexion obtained by the therapist or with use of uninjured hand
Requires that the fingers are maintained in flexion using an elastic band that is attached to the level of the wrist	Decreases incidence of flexion contractures at the PIP joint.

 

Ref:

1. Kleinert HE, Verdan C. Report of the Committee on Tendon Injuries (International Federation of Societies for Surgery of the Hand). J Hand Surg [Am], 1983; 8: 794-8.