8: Acute Repair of Zone 2 Flexor Tendon Injury

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Procedure 8 Acute Repair of Zone 2 Flexor Tendon Injury

Brent M. Egeland, Sandeep J. Sebastin, Kevin C. Chung

image See Video 5: Acute Repair of Zone 2 Flexor Tendon Injury

Figure 8-7 is adapted from Tang JB. Flexor tendon repair in zone 2C. J Hand Surg [Br]. 1994;19:72-75, with permission from Elsevier. Figure 8-18 is adapted from Strickland JW. Development of flexor tendon surgery: twenty-five years of progress. J Hand Surg [Am]. 2000;25:214-235, with permission from Elsevier.

Indications

image Acute repair of zone 2 flexor tendon injuries is indicated when there is a clean-cut injury with the following findings:

• Completely divided flexor digitorum profundus (FDP) and/or flexor digitorum superficialis (FDS)
• Partial flexor tendon injury involving greater than 60% of the tendon substance
• Minimal wound contamination

image A tendon defect of up to 1 cm can be repaired by end-to-end suturing. Greater losses (up to 2 to 3 cm) may need an intramuscular tendon lengthening via forearm incisions, and larger tendon gaps will need tendon grafting.

Examination/Imaging

Clinical Examination

image Patients present with loss of active distal interphalangeal (DIP) and proximal interphalangeal (PIP) joint flexion if both FDP and FDS are divided, or loss of only DIP joint flexion if only FDP has been injured. On inspection, the normal finger cascade is lost with the affected digit in an extended position.

image The function of the FDP is determined by asking the patient to actively flex the DIP joint of the involved finger.

image Testing for FDS injury is more complex compared with the FDP because the PIP joint is flexed both by the FDS and by the FDP. Therefore, one needs to check the function of the FDS while blocking the action of the FDP.

• The standard test for the FDS takes advantage of the fact that the FDP tendons to the long, ring, and small fingers share a common muscle belly. The finger being tested is allowed to flex while the action of the FDP tendon is blocked by preventing flexion of the DIP joint of the other two fingers (Fig. 8-1). The standard test is not reliable for the index finger because the index finger FDP has an independent muscle belly (Fig. 8-2). In addition, the action of the FDS of the small finger may be dependent on the FDS to the ring finger, and they may need to be tested together (Fig. 8-3).
• Mishra described a modified test whereby the subject is asked to press the fingertip pulp of all the fingers together against the proximal part of the palm, such that the DIP joint is kept extended. If the FDS is acting, the DIP joint remains in a position of extension to hypertension while the MCPJ and PIPJ are fully flexed. If the FDS of any of the fingers is injured or absent, the DIP joint goes into flexion. This test works on the principle that the FDP can flex the PIP joint only after it has flexed the DIP joint. If the DIP joint is maintained in extension, PIP joint flexion is purely a function of the FDS (Fig. 8-4).

image A partial tendon laceration should be suspected in patients in whom active motion is associated with pain or triggering.

image In patients who cannot cooperate (e.g., children or comatose or intoxicated patients), one can look for passive movement of the fingers resulting from the wrist tenodesis effect or by squeezing the forearm muscles (Fig. 8-5). The same maneuvers can be used when trying to differentiate between tendon injury and inability to move as a result of nerve palsy.

image It is important to examine the patient for presence of concomitant injuries to the digital arteries and nerves.

image

FIGURE 8-1

image

FIGURE 8-2

image

FIGURE 8-3

image

FIGURE 8-4

image

FIGURE 8-5

Imaging

image Preoperative imaging studies are not typically necessary, but anteroposterior and lateral x-rays may help identify associated bony injury. When a patient presents with unstable or intra-articular fractures, rigid fixation of the fracture is performed so that judicious tendon mobilization can be performed after tendon repair.

Surgical Anatomy

image Zone 2 contains both the FDS and FDP tendons and extends from the proximal edge of the A1 pulley in the palm to the insertion of the FDS over the middle phalanx. It includes four annular pulleys (A1, A2, A3, and A4) and two cruciate pulleys (C1 and C2) (Fig. 8-6).

image Zone 2 was subdivided by Tang (1994) into four subzones (Fig. 8-7).

• 2A: Includes the C2 and A4 pulleys and has the FDS insertion. Only the FDP tendon glides under the A4 pulley. The A4 pulley is located at the midpoint of the middle phalanx and is 0.5 to 0.8 cm long.
• 2B: Includes the C1 and A3 pulleys and has the chiasm portion of the FDS.
• 2C: Includes the A2 pulley and represents the narrowest segment of zone 2. The A2 pulley is about 2 cm long and is situated over the proximal two thirds of the proximal phalanx. The middle and distal parts of the A2 pulley are very narrow, and the FDS tendon bifurcates within the midpart of the A2 pulley.
• 2D: Includes the A1 pulley and represents the widest portion of zone 2.

image The blood supply to the tendons in this region comes from the vincular system and enters the tendon on the dorsal surface. It is recommended that core sutures be passed in the palmar portion of the tendon.

image

FIGURE 8-6

image

FIGURE 8-7

Positioning

image The patient lies supine on the operating table with the affected arm placed on a hand table.

image A lead hand is used during dissection and tendon repair.

Exposures

image Bruner incisions or midaxial incisions (by incorporating the transverse lacerations) are designed from the DIP joint to the base of the finger (Fig. 8-8).

image Thick skin flaps are raised in a plane superficial to the tendon sheath to expose the tendon sheath (Fig. 8-9).

image

FIGURE 8-8

image

FIGURE 8-9

Pearls

If the incision needs to be extended to the distal palm, one must avoid placing the incision in the web space to prevent a scar contracture that limits finger extension.

Knowing the mechanism of injury helps in determining the location of the distal cut end of the tendon, and the incision can be planned accordingly. If injury occurred in flexion, the distal cut end will migrate distal to the skin laceration with the finger held in extension. The skin incision will need to be extended distally. If injury occurred in extension, the distal cut end will be at the same level as the skin laceration. Retraction of the proximal cut end depends on the level of injury in relation to the vincular attachment. In zone 2A and 2B injuries, the proximal end may get caught at the A2 pulley. In zone 2C and 2D injuries, the tendon retracts to the distal palm, where the FDP is restricted by the lumbrical muscle attached to the radial side of the FDP.

Procedure

Step 1: Exposure of Divided Tendons

image The excursion of FDP within zone 2 is approximately 2 cm. To allow this excursion, we divide varying portions of the A2, A3, and A4 pulleys and the flexor sheath, depending on the location of the distal cut end of the tendon with the finger in extension (Fig. 8-10). Selective and limited division of the pulleys allows free movement of the repaired tendon while avoiding clinically significant bowstringing.

image

FIGURE 8-10

Step 2: Retrieval of Proximal Tendon End

image This can be challenging when the tendon has retracted into the palm. The following maneuvers are used in sequence:

• The first maneuver is to apply gentle pressure in a proximal to distal direction on the forearm with the wrist and metacarpophalangeal (MCP) joint in flexion. This may occasionally coax the tendon through the pulley system, especially for tendons ends that are caught at the A2 pulley.
• A single attempt with a fine-tipped mosquito forceps passed into the sheath from distal to proximal can be done next.

image If both these maneuvers do not work, the method described by Sourmelis and McGrouther should be tried. A chevron incision is made in the distal palm proximal to the A1 pulley. The flexor tendons are identified. If they are still within the A1/A2 pulley, they are not disturbed. A 5/6 French pediatric feeding tube is passed from retrograde through the flexor sheath to emerge at the proximal incision. The feeding tube is sutured to the palmar surface of the flexor tendon without withdrawing the tendons from the fibrous flexor sheath. If the tendon ends have retracted proximal to the A1 pulley, the feeding tube is sutured to the end of the tendons. Using a combination of pulling the feeding tube at the distal incision and pushing the flexor tendon at the proximal incision, the tendon ends are delivered into laceration (Fig. 8-11).

image After retrieval to the site of repair, the tendon should be secured in place with a hypodermic needle to prevent it from retracting proximally and to allow a tension-free repair.

image

FIGURE 8-11

Step 2 Pearls

The tendon should be handled with care to prevent iatrogenic injury and scarring.

Step 2 Pitfalls

Repeated blind grasps with a hemostat within the fibrous flexor sheath in an attempt to retrieve the proximal tendons should be avoided. Limited incisions in the pulleys will allow atraumatic access to the tendon within zone 2.

Step 3: Tendon Repair

image The tendon ends are gently débrided of frayed ends while retaining their length.

image The FDS is repaired before the FDP. An attempt is made to repair both slips of the FDS (Fig. 8-12). This may be difficult, especially in zone 2C, where the A2 pulley is narrowest. In such circumstances, repair of one slip is appropriate. Because of the flatness of the FDS at zone 2, its repair is a simple horizontal mattress suture repair of each slip of the FDS.

image Many methods of tendon repair have been described for the FDP. We use a 6-0 Prolene suture epitendinous repair combined with a 3-0 Ethibond modified double-Kessler core suture (Fig. 8-13).

image First the epitendinous repair of the dorsal half of the tendon is carried out. Sutures bites are taken at 1- to 2-mm intervals approximately 1 to 2 mm from the edge of the tendon. This is a continuous suture repair, and the loops are locked.

image Next a modified Kessler core suture is placed in the standard manner (Fig. 8-14). The transverse portion of the suture is locked. It is important to remember that 3-0 Ethibond is a braided suture and does not glide well within the tendon substance. One should therefore pull the required length of the suture through the tendon at first pass. A minimum of 0.7 cm, and most commonly 1 to 1.2 cm, of the tendon is grasped by the longitudinal portion of the suture loop before making the transverse portion.

image A horizontal mattress suture is placed within the previous suture repair using 4-0 Ethibond. Approximately 0.5 to 0.6 cm of the tendon is grapsed by the longitudinal portion of the suture loop before making the transverse portion (Fig. 8-15).

image The palmar half of the epitendonous repair is now completed (Fig. 8-16).

image

FIGURE 8-12

image

FIGURE 8-13

image

FIGURE 8-14

image

FIGURE 8-15

image

FIGURE 8-16

Step 3 Pearls

If the FDS is lacerated at the Camper chiasm, direct mattress repair to the radial and ulnar tendon ends can be performed using 4-0 or 5-0 braided suture.

After tendon repair, the finger should be placed through gentle range of motion to ensure adequate tendon gliding through the pulley system. If the pulleys are restricting free motion, they should be vented by divided them at one edge.

Step 3 Pitfalls

If a gap is noted during passive mobilization, the repair needs to be done again or strengthened. The gap will heal by scarring, which will be weak and can rupture easily.

It is crucial to orient the FDS and FDP correctly during repair because the tendons may twist in the sheath. Additionally, the lacerated FDP may migrate outside the FDS chiasm, and it should be gently passed through the chiasm. If the vincula is still intact, it must be carefully preserved during the repair.

Step 4: Closure

image The tourniquet is released and hemostasis obtained.

image The skin is loosely closed to accommodate for postoperative edema (Fig. 8-17).

image

FIGURE 8-17

Postoperative Care and Expected Outcomes

image The patient is splinted in 30 degrees of wrist flexion and 60 degrees of metaphalangeal (MP) flexion and with the fingers in slight flexion.

image It is critical for the surgeon and therapist to maintain direct communication during the postoperative period.

image Tendon repair strength declines for the first week after surgery, plateaus for 1 week, and then slowly begins to get stronger. In this initial phase of healing, all strength across the repair is due to the suture and will increase predictably with increasing strand count. During tendon healing, the force applied to the repair should always be below the repair strength, or rupture may occur. Following this logic, and explicitly described later for a four-strand core-suture repair, passive exercises always remain below rupture threshold and are used for the initial 4 weeks following surgery. At 4 weeks, active exercises are safely started. Strengthening is not started until 8 weeks (Fig. 8-18).

image Indiana Early Active Mobilization, or the Tenodesis Program, is initiated on postoperative day 3. This involves both passive exercises using a Modified Duran Program and place-and-hold exercises.

• The patient’s bulky dressing is removed and replaced with a dorsal blocking splint (DBS) to be worn at all times with the wrist in 20 degrees of palmar flexion, MP joints in 70 degrees of flexion, and interphalangeal (IP) joints at neutral. While wearing the DBS, a modified Duran Exercise Program is initiated and continued every 2 hours throughout the day. Specifically, each session involves 25 repetitions of passive flexion and extension of the PIP, then the DIP, and then the entire digit.
• In addition, a second tenodesis splint is applied. This allows wrist flexion but limits wrist extension to 30 degrees. Within this splint, place-and-hold exercises are performed. This involves composite passive flexion of the digits while simultaneously bringing the wrist from flexion into extension. Once in extension, the patient actively maintains a fist position for 5 seconds and then lets it passively relax, and the wrist drops into flexion.

image At 4 weeks, the tenodesis splint is discontinued, but the place-and-hold exercises continue. Additional active exercises are started, consisting of making a fist while the wrist is in neutral position. Active wrist flexion and extension are allowed. The Modified Duran Program is continued within the DBS.

image At 5 weeks, active extension is allowed.

image At 6 weeks, the DBS is discontinued, and the involved finger is buddy-taped to the adjacent finger. An extension splint is worn at night.

image At 8 weeks, progressive strengthening is started.

image At 10 to 12 weeks, the patient may return to all activities but should not perform heavy lifting until 16 weeks.

image Based on the Total Active Motion (TAM) evaluation system proposed by Kleinert and Verdan, and advocated by the American Society for Surgery of the Hand, most patients should regain good to excellent function after primary repair of flexor tendons (Table 8-1). TAM is calculated by the following formula:

• TAM = total active flexion (MCP joint + PIP join + DIP joint) − total extension deficit (MCP joint + PIP joint + DIP joint).
image

FIGURE 8-18

Table 8-1 Methods of Grading Total Active Motion

image

Evidence

Kitis PT, Buker N, Kara IG. Comparison of two methods of controlled mobilisation of repaired flexor tendons in zone 2. Scand J Plast Reconstr Surg Hand Surg. 2009;43:160-165.

This study compares active and passive regimens of postoperative motion. Controlled active motion (Kleinert/Washington) was compared with group-controlled passive motion (Duran). The controlled active motion group achieved better results in Total Active Motion (TAM) and Disabilities of the Arm, Shoulder and Hand (DASH) scores. This is the first high-level evidence study demonstrating superiority of early active versus early passive movement. (Level II evidence)

Tang JB. Flexor tendon repair in zone 2C. J Hand Surg [Br]. 1994;1:72-75.

This article reports on a randomized prospective clinical study evaluating Total Active Motion (TAM) after repair of both the FDS and FDP, versus the FDP alone, in zone 2B (under the A2 pulley). The results indicated decreased TAM when both FDS and FDP are repaired in this region. Furthermore, there was a higher rate of adhesions or rupture requiring operative management. The author concluded that with a laceration at zone 2C, the FDS should be excised in favor of repairing FDP alone. (Level IV evidence)

Tang JB. Indications, methods, postoperative motion and outcome evaluation of primary flexor tendon repairs in zone 2. J Hand Surg [Br]. 2007;32:118-129.

In this expert opinion article, the author presents his practical views on zone 2 flexor tendon repairs. Tang discusses indications, techniques, and postsurgical treatment and outcome measures and further describes methods of sheath-pulley release, tendon repair, postoperative motion, and outcome evaluation. Based on the information in this review, the author notes that predictable outcomes of flexor tendon repair in zone 2 are now routine. (Level V evidence)

Thien TB, Becker JH, Theis JC. Rehabilitation after surgery for flexor tendon injuries in the hand. Cochrane Database Syst Rev. 2004;4:CD003979.

This is the only Cochrane review regarding flexor tendon repair, and it specifically reviews postoperative therapy. Six randomized controlled trials were reviewed. Despite widespread use of postoperative therapies, this review found insufficient evidence to define the best mobilization strategy. There was a trend toward early active mobilization strategies. (Level II evidence)

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