Extensor Tendon Repair.

Background: Extensor tendon injuries are a common condition that hand surgeons must be prepared to treat. The area of extensor tendon injury can traditionally be broken down into 9 zones. Physical examination is the best way to diagnose extensor tendon injury with a loss of active extension in the injured digit. The tenodesis effect may be utilized to aid in diagnosis: wrist flexion should cause passive extension at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints if the extensor tendon is in continuity.

Description: Repair of extensor tendon injuries depends on the zone of injury and the thickness of the tendon, which determines its ability to hold core sutures. For zone-I and II injuries, several "figure of 8" buried sutures can be utilized or a running type of suture may be employed. For zone-III to VII injuries, 1 or 2 core sutures and a supplementary running suture can be utilized.

Alternatives: Several alternative techniques have been previously described. These include variations in the number of core strands, repair configuration, and suture caliber, as well as the use of epitendinous repair. Alternative treatments also include nonoperative treatment, which is typically reserved for partial tendon injuries and for patients who are unable to tolerate a surgical procedure.

Rationale: The techniques that we describe are tailored to the thickness of the tendon. Running sutures are applicable to any zone, whereas core sutures are best utilized in zones III through VII. The running interlocking horizontal mattress technique has been found to be stiffer and faster to accomplish compared with the other techniques, and was found to have good to excellent clinical results in a study of lacerations in zones IV and V^1,2.

Expected outcomes: Repair of extensor tendon lacerations has demonstrated good long-term outcomes if performed in a timely manner after injury. A previous study showed good to excellent function in up to 64% of acute extensor tendon repairs, more fingers lost the ability to flex fully than lost the ability to extend³. Systematic reviews have suggested that dynamic rehabilitation may not provide superior long-term benefit compared with static splinting⁴.

Important tips: The Elson test should be performed under a digital nerve block in order to properly assess the integrity of the central slip.In distal zone I and III injuries, suture anchors or bone tunnels may be utilized when there is no remaining tendon on the distal end of the laceration.When preparing the tendon ends for repair, it is important to handle the tendon delicately-preferably through the cut end of the tendon rather than the tendon itself.In zone-VII injuries, the injured tendon may lie beneath the extensor retinaculum. In such cases, windowing of the extensor retinaculum may decrease adhesion formation and facilitate repair.

Acronyms and abbreviations: MCP = metacarpophalangealPIP = proximal interphalangealDIP = distal interphalangealIP = interphalangealROM = range of motionRMS = relative motion splintRIHM = running interlocking horizontal mattress.