Indications and operative planning
• Zone 1 –the technique for flexor repair in zone 1 depends on how close to the insertion the FDP has been divided. If the tendon is divided close to the bone (e.g. FDP avulsion) then it may be necessary to use a suture anchor such as a mini-Mitek to secure the tendon end.
• Zone 2– proximal zone 1 and zone 2 repairs of the FDP tendon are similar. The aim is to repair the tendon but to avoid any bulkiness at the repair site to allow the tendon to glide within the flexor sheath. If the repair is done badly it will be too bulky and may trigger, rupture or jam in position unless the flexor sheath is opened. Special care must be taken with repairs of FDS in this zone (see below).
• Zone 3 – zone 3 repairs are easier to perform because there is no tight flexor sheath to contend with and the tendon ends are larger. Distal zone 3 repairs may catch on the A1 pulley, which may need to be divided.
• Zones 4–5– repairs in these zones are the same as repairs of the extensor tendons in zones 6–8.
• Complete division – primary repair of a flexor tendon rupture should be performed as soon as possible. Unlike the extensor tendons, surgical
intervention of some form is always necessary when the flexor tendons have been divided.
• Timing of repair – there is good evidence that the outcome of primary repair is superior when carried out as quickly as possible (within 72 hours). There is a particular urgency in carrying out a repair of the flexor tendons (as compared with extensor tendons) because the flexor pulleys will eventually collapse/fill with scar tissue after 3–4 weeks. Any tendon repair will then need to reconstruct the pulleys as well, making surgery more complicated than necessary.
• Particular tendons – the flexor muscle bellies (especially flexor pollicis longus – FPL) have a tendency to shorten quickly. This may make primary repair of a tendon impossible. The ring and middle fingers are particularly prone to avulsion injuries of the FDP tendon. Repair of combined injuries of flexor digitorum superficialis (FDS)/FDP tendons in the little and ring fingers are particularly prone to formation of adhesions. Therefore, considera - tion should be given to repairing just the FDP tendon in these digits.
• Zone of injury – as for extensor tendons, the surgical technique for repair of flexor tendons varies depending on the zone of injury (Fig. 9.14).
Flexor tendon repair 131
Zone 1 (distal to FDS insertion) Zone 2 (A1 to FDS insertion) Zone 3 (forearm) Zone 3 (palm) Zone 4 (carpal tunnel)
Figure 9.14 The zones of flexor tendon injury. FDS, flexor digitorum superficialis
• Partial division of flexor tendons– there is good evidence that inserting sutures into a tendon results in necrosis of the tendon substance. Therefore, the use of sutures should be avoided for any partial tendon injury involving less than 50 per cent of the diameter of the tendon. Instead, we recommend trimming the edges of the tendon laceration to prevent triggering (if any is present) followed by supervised mobilization in a splint as for a complete flexor tendon division for the next 8 weeks.
Contraindications
• Active infection
• Skeletal instability
• Fixed joints
• Delayed presentation (more than 3–4 weeks) can rarely be repaired primarily as the tendon ends will have retracted and shortened and the flexor pulleys will have collapsed.
• Attrition ruptures
• Smoker
• Poor social or psychological circumstances
• Partial tendon rupture of less than 50 per cent should not be repaired
• Delayed presentation.
Consent and risks
• Scars: it is often necessary to extend the wounds to gain access to the tendon ends
• Splintage and physiotherapy: patients will not have full use of the affected hand for 12 weeks. The importance of compliance with the postoperative physiotherapy must be stressed
• Infection
• Adhesions: a particular problem when there is an underlying fracture. Overall, there is a 5 per cent tenolysis rate
• Rupture: zone 2 finger flexors – 5 per cent, FPL repair – 12 per cent
• Bowstringing: may not be evident for some years after the original event. It may occur if it proves necessary to divide the flexor sheath completely in order to repair the tendons. A subsequent pulley reconstruction will then be required
• Neuroma formation
Anaesthesia and positioning
For isolated FDP injuries, it is often possible to perform a repair under digital nerve block with a finger tourniquet. For FPL, FDS and more proximal flexor injuries, general anaesthesia or a regional block is necessary because of the need for an arm tourniquet. The arm is positioned in the supine position with an arm table.
SURGICAL TECHNIQUE
Landmarks and incisions
The Bruner (zigzag) incision (Fig. 9.15) is preferred. If there is a laceration then it can be incorporated into the incision after suitable debridement of the wound edges. Bruner incisions are marked out and the skin and fat are incised down to the level of the flexor sheath using a no. 15 scalpel blade and/or tenotomy scissors.
Dissection
Structures at risk
• Edges of the skin flaps
• Neurovascular bundles
Figure 9.15 Suggested Bruner incisions to approach the flexors
The flaps can be retracted with skin hooks or held in place with ‘stay’ sutures. A ‘window’ is opened in the flexor sheath by creating zigzag flaps. Ideally, the window should be as small as possible and should be positioned only between the annular pulleys to allow maximum preservation of the pulley system.
If the flexor sheath is opened with zigzag flaps it is usually possible to repair the sheath with a slightly larger diameter by approximating the tips of the flaps. This will allow any reconstructed pulley system to accommodate a more bulky, less than perfect, tendon repair.