Outline

We present our experience with pull-out repairs of flexor digitorum profundus (FDP) tendon injuries in zone 2. Since 1973, we have repaired zone 1 and 2 tendon injuries with the Bunnell technique of pull-out suture through the fingertip, together with immediate active digital mobilization of patients. We followed a sample of patients with zone 2 FDP tendon lacerations treated between 2005 and 2008, and no patients had rupture of the repairs. We assessed the outcomes of one group of 46 patients (46 digits) by evaluating subjective and objective function; 33 digits (72%) had good or excellent results. We also compared the results in 22 digits treated with the pull-out method to those in 22 digits after two-strand surgical repairs. We noted faster recovery of active finger flexion and grip strength after the pull-out method. Poor results were seen only when tendon mobilization was begun too late or was insufficient.

Flexor tendon surgery has made much progress since the 1970s due to accrued knowledge of the biology of tendon tissue repair and great improvement in suture techniques and postoperative mobilization concepts. However, tendon repair in zone 2 still is a problem due to the high risk of adherence and consequent limitation of range of active motion, even when early postoperative protected motion is adopted.

The pull-out technique was described by Bunnell in the beginning of the 20th century for tendon repair. Mantero and colleagues ¹^–³ started using the technique in 1973 in association with immediate postoperative active motion. With this regimen, the occurrence of tendon adherence and an hypertrophic cutaneous scar with consequent acquired and permanent deformity and stiffness of the joints was remarkably decreased.

Indications

Any clean-cut injury of the flexor digitorum profundus (FDP) tendon in zone 2 or the flexor pollicis longus (FPL) tendon in zone 2 can be repaired with this technique. This method is also indicated for FDP tendon injuries in proximal zone 1, where direct end-to-end tendon repair is necessary.^1,⁴^–⁶ However, we do not use this method in the case of complex trauma (e.g., amputation or tendon injury associated with exposed fracture), because early motion is not possible, and the button on the top of the finger carries a risk of causing ischemia in situations in which digital circulation is already poor.

When both the FDS and FDP tendons are injured, the FDS tendon can be repaired with any end-to-end repair method in association with FDP repair by our method.

Surgical Techniques

Under regional anaesthesia, two cut tendon ends are exposed through a Bruner’s skin incision. A needle (size: 20G) used for spinal anesthesia is inserted from the fingertip and passed through the distal FDP tendon stump, from distal to proximal. Then, a 2-0 nylon thread is passed in the proximal tendon stump for 1 to 1.5 cm from the cut creating an Ω-shaped loop. The needle is then cut and the two ends of the suture are passed in the distal tendon stump by the previously inserted needle. The thread is pulled out from the tip of the finger and its two ends are secured over a mother-of-pearl button with multiple knots (Figures 18[A]-1 to 18[A]-6). For all repairs, ensuring correct coaptation of the two tendon ends with good tension is very important and depends on the surgeon’s experience. A running suture with 4-0 suture is added to tighten the tendon edges. Previously, we used a 4-0 Prolene suture and noted some foreign body reactions caused by sutures during long-term follow-up, and suture remnants had to be removed. We prefer to use absorbable (such as PDS) sutures presently.

Figure 18(A)-1 Illustration of the pull-out technique. The needle is passed through the distal part of the tendon after an Ω-shaped loop is made in the proximal tendon stump.

Figure 18(A)-2 Passing the thread through the distal tendon stump.

Figure 18(A)-3 A case of zone 2B flexor tendon injury in a child and skin incisions to expose the tendons.

Figure 18(A)-4 The retracted proximal tendon stump was exposed and pulled distally under the A2 pulley.

Figure 18(A)-5 The Ω-shaped suture was placed in the proximal stump of the tendon.

Figure 18(A)-6 The thread was passed through the distal stump of the tendon and tired over a mother-of-pearl button on the fingertip.

Tendons cut distal to the A2 pulley (in zones 2A and 2B) can be more easily repaired with this method, because the distal tendon is shorter and has fewer constrictive pulleys. Therefore, it is easier to insert the needle from the fingertip through the entire distal tendon stump. For tendons cut at or proximal to the A2 pulley, the needle will pierce a greater length of the distal tendon stump with both DIP and PIP joints slightly flexed. After piercing, the internal guide of a spinal needle is retracted so that the passage of the 2-0 nylon thread is allowed. We prefer to use two different passages through the tendon stump for the thread; it ensures greater tightness of the system as the suture tension is more evenly spread along all parts of the tendon during motion.

Whenever possible, the pulley system is respected. When the A2 or A3 pulley is partially or totally damaged or when the pulleys must be partially incised to avoid any impingement of the tendon repair site on the edge of the pulley, these pulleys are not repaired. When more pulleys are injured, reconstruction is strongly recommended, especially for A2 and A4 pulleys, to avoid tendon bowstringing. We prefer to use a flap of extensor retinaculum (Lister technique) or one of the FDS tendon slips (when the FDS tendon is not repaired), sutured to the pulley remnants. A suction drain is placed and the skin is sutured with absorbable sutures. The drain is removed 1 day later, and a thinner dressing is made so that a wider range of active digital motion is allowed.

Postoperative Care

Immediate active motion is the keystone to success with this technique and it has to start as soon as possible.¹^–⁴ In particular, full extension of the proximal interphalangeal (PIP) joint must be achieved in the first few days after surgery. On the first day, the dressing is reduced and the patient can start active digital motion with the wrist in a protected position (wrist in flexion). Daily homework is given to the patient, so that he or she can be autonomous, not only in moving but also in cleaning and renewing the dressings if necessary. One week later, the wound is checked and any remaining swelling is controlled. If possible, a smaller dressing is placed to allow a wider range of motion. The range of active digital flexion is increased gradually (Figure 18[A]-7). At about 21 days, it is important to observe whether there are any early clinical signs of block of tendon gliding or joint motion. If nothing abnormal is found, more vigorous and full active digital flexion exercises are performed.