Flexor Tendon Injury, Repair and Rehabilitation

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Key points

  • Flexor tendon injuries can be challenging, especially in zone II.

  • A strong repair using at least a 4-strand core suture and an associated epitendinous suture will allow for early rehabilitation, which can minimize the risk of adhesion formation. Core sutures should have a minimum of 7-mm to 10-mm depth of purchase, whereas epitendinous sutures should have a 2-mm rim for repair.

  • Bulky repairs should be avoided to allow for smooth tendon function. On occasion, the A2 or A4 pulleys may be vented up

Anatomy

The flexor digitorum superficialis (FDS) muscle originates proximally in the forearm, and is innervated by the median nerve. The flexor digitorum profundus (FDP) lies deep to the FDS and has a dual innervation: the FDP to the ring and small fingers by the ulnar nerve and the FDP to the index and long fingers by the median nerve. The FDP tendons all arise from a common muscle belly, although the tendon to the index finger may arise separately. Distally, at the level of the carpal tunnel, the FDS

Patient evaluation

The initial evaluation of a patient with a flexor tendon injury is important in formulating a diagnosis, establishing a treatment plan, and counseling the patient regarding expected outcomes. The mechanism of injury has implications for the quality of the tendon and the status of the surrounding soft tissues. A sharp laceration is more likely to have a cleanly cut tendon end and less soft tissue damage than a crushing or avulsion-type mechanism. The position of the finger at the time of injury

Principles of tendon repair

There are several variables that can affect the quality of flexor tendon repair. The resistance to gap formation at the repair site and the ultimate strength of the repair are interrelated. They are primarily influenced by the number of core suture strands, the core suture configuration, the core suture size, and the addition of a peripheral epitendinous suture. However, additional factors influence the strength of a repair including material properties of the suture, presence of locking

Biology of tendon repair

Several growth factors have been recognized to increase after tendon injury, which may contribute to both tendon healing and scar formation. These include vascular endothelial growth factor, insulinlike growth factor, platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), and transforming growth factor-ß.41, 42, 43, 44, 45 The transcription factor NF-κB has been shown to increase for up to 8 weeks after tendon injury.42 Fibronectin and integrins are upregulated during the

Zone I

Zone I injuries occur distal to the FDS insertion and involve only the FDP tendon. Lacerations in which there is less than 1 cm of distal stump remaining attached to the distal phalanx can be treated with advancement and direct repair of the proximal tendon to the distal phalanx. If the tendon must be advanced more than 1 cm, or if there is excessive tension at the repair site, a “quadriga effect” can occur. In this situation, the digit with the overtensioned tendon will reach maximal flexion

Rehabilitation

Complete immobilization after flexor tendon repair is indicated only in limited situations such as pediatric patients, patients with concomitant bone or soft tissue injuries requiring immobilization, or patients who are unable to comply with a protected motion protocol.

In most cases, a protected motion protocol is used postoperatively. Early motion of flexor tendons improves recovery of tensile strength, decreases adhesions, improves tendon excursion, and promotes intrinsic healing.1 The

Summary

Flexor tendon injuries remain a challenging problem in hand surgery due to the intimate anatomy of the FDP, FDS, and the pulley system. Repairs need to be strong enough to begin early range of motion, while avoiding bulkiness within the confines of the pulley system. Currently, although many repair configurations are acceptable, it is recommended that at minimum a 4-strand core suture repair with an epitendinous suture is used. Although every attempt should be made to repair both the FDP and

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  • Cited by (17)

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    • The evidence-base for the management of flexor tendon injuries of the hand: Review

      2019, Annals of Medicine and Surgery
      Citation Excerpt :

      Lacerations in zone 2 may involve the FDS and FDP tendons and both should be repaired with extra care taken not to disrupt campers chiasm [25]. If repair of both slips of the FDS results in a bulky tendon which impedes glide then it is acceptable for one slip to be resected [26]. Tendons can be safely exposed by using a Bruner's incision or a mid-lateral Bunnell's incision [25].

    • Acute tendon injuries

      2019, Orthopaedics and Trauma
      Citation Excerpt :

      Some controversy exists as to whether FDP and FDS should be repaired. Some surgeons will only repair FDP, while others will repair only a single slip of the FDS tendon and use the other slip to reconstruct the pulley.3 It may be wise to first repair the FDP and then to assess how much gliding resistance is present before deciding whether to repair the FDS or not.

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    Funding Sources: None.

    Conflicts of Interest: None.

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