Flexor Tendon Repair

Updated 3/2017-- photos and all links removed as many are no longer active.

Like the extensor tendons, there is little to protect to the flexor tendons -- thin skin (though the palm skin is thicker than skin on the back of the hand) and minimal subcutaneous tissue. The flexor tendons can be easily injured by knives, saws, splinters, etc. The flexor tendon anatomy can be reviewed here online, or in more depth offline using a good anatomy or hand surgery text. 

These injuries will often include fractures or soft tissue injuries (lacerations, crush, loss of skin, nerve/vessel injury, etc). This post is only a brief overview of the repair of "isolated" flexor tendon laceration at the time of injury, not reconstructively later. This post will in no way make the reader an expert on flexor tendon injury/repair, but will give you a general understanding (maybe).

Injuries of the flexor tendon are defined by zones. The tendon injuries in finger Zones II tend to fare worse than injuries in the other zones.

Zone I --

• defined as distal to the FDS insertion, so only the profundus tendon here.

Zone II --

• is often referred to as "Bunnell's no man's land". Frequently restrictive adhesion bands will form around lacerations in this area.
• It is defined as the area extending from the insertion of the FDS tendon to the proximal end of the A1 pulley.
• Within zone II and at the level of the proximal third of the proximal phalanx, the FDS tendons split into 2 slips, collectively known as Camper chiasma. These slips then divide around the FDP tendon and reunite on the dorsal aspect of the FDP, inserting into the distal end of the middle phalanx.

Zone III --

• extends from the distal edge of the carpal ligament to the proximal edge of the A1 pulley, which is the entrance of the tendon sheath.
• Within this zone, the lumbrical muscles originate from the FDP tendons.
• The distal palmar crease superficially marks the termination of zone III and the beginning of zone II.

Zone IV --

• includes the carpal tunnel and its contents (ie, the 9 digital flexors and the median nerve).

Zone V --

• extends from the origin of the flexor tendons at their respective muscle bellies to the proximal edge of the carpal tunnel.

Clinical Evaluation

Careful attention to the patient's history and the mechanism of injury can often alert the examiner to the extent of the injury. Finger position at the time of injury is important.

• If the injury occurred while the finger was in flexion, the level of the tendon injury will be distal to the skin laceration.
• A finger that is injured in the extended position will have a tendon injury that closely corresponds to the skin laceration.

The natural resting position of the hand should be closely observed.

• In the uninjured hand, the flexion of the fingers increases from the radial to the ulnar side. This is the "normal composite cascade".
• The finger with a tendon disruption will rest in a more extended position.
• If only the FDP tendon has been transected, the flexion of the MCP and PIP joints may be within the normal cascade but the DIP will be extended.
• A finger in which the FDS tendon and the FDP tendon are both disrupted will lie flat in an extended position, well outside the normal cascade.
• A thorough, formal examination of the FDS and FDP tendons is important because testing these tendons may reveal partial lacerations. A partial laceration may present with pain when the patient attempts to flex against resistance.

The integrity of FDS and FDP tendons should be tested independently and in tandem.

• To test the FDP tendon, the examiner holds the other fingers in extension and stabilizes MCP and PIP joints. The patient is then asked to flex the distal phalanx.
• To test the FDS tendon, the examiner holds the other fingers in extension, but the MCP and PIP joints are released. The patient is asked to flex the finger. The PIP joint and, to a lesser degree, the MCP joint should flex. About 20% of patients are missing an FDS tendon in the little finger and will therefor have limited or no PIP flexion during testing.
• For flexor pollicis longus (FPL) testing, the thumb MCP joint is stabilized in neutral position. The patient is asked to flex the interphalangeal (IP) joint against resistance. A communication may exist between the FPL and the index FDP. The examiner stabilizes the other 3 digits. The patient opposes his or her thumb to the little finger MCP joint. Flexion of the index distal phalanx proves the existence of this anomalous communication.
• Passive manipulation of the wrist through flexion and extension should result in extension and flexion of the digits, respectively. This uses the tenodesis effect of the antagonistic tendons. If a tendon is transected, then there can be no tenodesis effect.
• Compression of the forearm flexion muscles also can be used to test the integrity of the flexor tendons in the hand. As the forearm is compressed, the digits are drawn into flexion. Transected tendons in the digits do not flex with this maneuver.

PRIMARY REPAIR

The optimal time for repair of the flexor tendons is within 24 hours of the injury (primary tendon repair). Delayed primary repair (between 24 hrs and 2 weeks) is indicated in grossly contaminated wounds. Early secondary repair takes place between 2 and 5 weeks after the injury. The earlier the surgery, the less likely it is that wound edema and infection will ensue. Late secondary repair (more than 5 weeks after injury) results in poor function due to tendon swelling, muscle retraction, and extension deficit.

All flexor tendons should be repaired in the main operating room in a controlled, sterile environment under tourniquet control. Surgical exposure can be obtained through Brunner (volar zigzag) or lateral (mid-axial) incisions. Care is taken not to injure the neurovascular bundles, which can be quite superficial in the finger.

Only the lacerated edges of the tendon should be handled to avoid trauma to the uninjured area of the tendon. The proximal tendon end may retract into the palm because of the muscle tension of the profundus and lumbrical muscles.

• The tendon can be retrieved with Jacob forceps or fine clamps, aided by milking the tendon proximally to distally.
• If this doesn't work, then a counter-incision in the palm must be made to find the proximal end of the severed tendons. Once identified, a pediatric feeding tube is introduced at the distal wound site through the fibro-osseous canal, to emerge into the palm incision site. The feeding tube is sutured to the end of the tendon and pulled out distally, carrying with it the proximal end of the flexor tendon. The tendon is then held in this position with a 25-gauge needle in the palm.

Using an atraumatic technique for tendon manipulation helps prevent further injury to the tendons and decreases the amount of adhesion formation. Every traumatic site along the tendon is another potential spot for adhesion formation. Delicate forceps, such as the Bishop-Harmon or Iris forceps, should be used to pick up the tendon at its severed end, although not along the sides of the tendon.

Disruption of the pulleys, especially A2 and A4, should be avoided. If the laceration is at these pulleys or if the repair is hindered because of the pulleys, then Z-plasties in the pulleys or partial releases may be required. The pulleys are repaired after the tendon is repaired. Shredded or mutilated pulleys may need to be reconstructed. This can be done using a slip of the FDS tendon, tendon grafts, or extensor retinaculum grafts.

The goal of the tendon repair is to coapt the severed ends without bunching or leaving a gap. Bunching of the repair may inhibit tendon excursion under the pulley system. Leaving a gap left at the repair site can either weaken the repair, which will leave the tendon prone to future rupture, or foster an overabundance of adhesions (scarring), limiting excursion of the tendon.

Most tendon suture methods will use both a core suture and an epitendinous suture.
Core Suture Techniques

• Modified Kirchmayr/Kessler Suture with single knot at repair site
• Tajima Modification of Kessler Suture with double knots at repair site

  Tajima repair, core suture only; B) Tajima repair, core plus epitendon suture; C) Savage repair, core suture only; D) Savage repair, core plus epitendon suture.

• Four-strand Interlock Stitch (Tsuge)
• Double-loop Locking Suture
• Six-strand suture techniques

1. (A) The Y1 technique: combination of the Tsuge suture with a 4–0 looped thread and the modified Kessler suture using a 4–0 double strand with 2 needles.
2. (B) The TL technique using 3 Tsuge sutures with 4–0 looped thread.

Epitendinous Suture Techniques

It was once thought that the epitendinous suture was primarily of esthetic importance, as in "tidying up the ends". It has been shown that an epitendinous suture actually increases the overall strength of the repair and is important in resisting gap formation.

• Simple Continuous Running Epitendinous suture
• Running-locking Loop Suture
• Halsted Continuous Horizontal-mattress Suture
• Continous Horizontal-mattress Intrafiber Suture
• Cross-stitch

The suture material that is used to repair the severed tendon varies. The usual caliber of suture is either 3-0 or 4-0. Braided or monofilament sutures also have been used. Knots should be buried, as their exposure can promote adhesion formation. One or 2 core sutures and a running epitendinous suture should be used. There is recent interest in using barbed sutures for "knotless" repair of tendons. (photo credit)

Early initiation of rehabilitation is important for an optimal result. Here are some good sources for postop rehab guidelines:
Zones 2-5 Flexor Tendon Repair (PDF file); Dept of Rehabilitation, Brigham and Women's Hospital, Sept 2007
Flexor Tendon Repair Rehab Guidelines. Zones 1-3; Center for Orthopedics (PDF file)
Flexor tendon repair- Kleinert protocol


REFERENCES
Flexor Tendon Anatomy; eMedicine Article, May 1, 2007; Steven J Bates MD, Cato T Laurencin MD, and James Chang MD
Flexor Tendon Lacerations; eMedicine Article, Oct 19, 2007; Michael Nuemeister MD, Bradon J Wilhelmi MD, and Reuben A Bueno, Jr MD
Flexor tendon repair in zone II with 6-strand techniques and early active mobilization. J Hand Surg [Am] 31A:987–992, 2006; Osada D, Fujita S, Tamai K, et al
Flexor Tendon Repair and Rehabilitation : State of the Art in 2002; J. Bone Joint Surg. Am., September 3, 2002; 84(9): 1684 - 1706
M. I. Boyer, J. W. Strickland, D. R. Engles, K. Sachar, and F. J. Leversedge
Flexor Tendon Repair; Duke Orthopaedics Wheeless' Textbook of Orthopaedics Online
Flexor Tendon Lacerations in the Hand; UPOJ, Vol 10, Spring 1997, pp 5-11; David R Steinberg MD
Zones 2-5 Flexor Tendon Repair (PDF file); Dept of Rehabilitation, Brigham and Women's Hospital, Sept 2007
Flexor Tendon Repair Rehab Guidelines. Zones 1-3; Center for Orthopedics (PDF file)