Figure 1. Laceration overlying proximal interphalangeal (PIP) joint of right second digit. (Photograph by Daniel Ting and Jared Baylis)

A 34-year-old cabinet maker presents to your Emergency Department after accidentally getting his finger caught in a drawer. On examination, he has a superficial, clean laceration over the dorsal surface of the right second digit (Figure 1).

In a previous post, we discussed the approach to identifying, treating, and managing extensor tendon injuries of the hand. In it, we advocate for a high index of suspicion for extensor tendon injuries whenever a patient suffers a laceration to the dorsal aspect of the hand. However, lacerations over the PIP joint deserve special mention. In this article, we focus on the diagnosis of a specific type of extensor tendon laceration: the central slip injury.

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You are working in the treatment area with a medical student and she is ready to review a “straightforward” case with you. She presents a young, healthy 27-year-old man with a laceration over the dorsal surface of the left hand after a kitchen mishap. It appears clean, and she doesn’t suspect a foreign body. The neurovascular status seems okay with the intact ability to extend the fingers. Her plan is to repair the wound and send the patient for follow up in 7 to 10 days with his family physician for suture removal. The wound appears superficial, but you are an astute clinician and wonder if the skin laceration might not be the only injury. Is there an associated extensor tendon injury?

Epidemiology

Extensor tendon injuries of the fingers, hand, and wrist are frequently seen in the emergency department. One recent study found 33.2 tendon injuries to the hand/wrist per 100,000 person-years.¹ These injuries occur more often in males than females and have their highest incidence between 20 and 29 years of age.^1,2

Anatomy

Extensor tendons are superficial and as such are easy to injure. Over the dorsum of the hand, the extensor tendons form a network of fibers connected by the juncturae tendinum [Figure 2]. These can mask an extensor tendon injury because an uninjured adjacent tendon may compensate for extensor movement.

Figure 2: Extensor tendons of the hand with juncturae tendinum as illustrated by black marker. (Photo by Daniel Ting and Jared Baylis)

Which structures are injured depends on the zone of injury. Injuries can occur to the common extensor tendon, the lateral bands, the central slip, and/or the terminal extensor tendon. The zones of injury are broken down anatomically into zones I through VIII, allowing a universal language for the description of hand/wrist injuries [Figure 3].

Figure 3. Verdan’s zones of the Hand, used as a common language for description and management of extensor tendon injuries to the hand. Image created by Brian Lin, MD

There are specific anatomical considerations for extensor tendons overlying the fingers, especially over the proximal interphalangeal joint, where the central slip may be injured. Injuries of the central slip will be covered in our next post.

Physical exam

Test each extensor joint through active range of motion against resistance. If there is any uncertainty, compare it to the other hand.  The key to diagnosing an extensor tendon injury is to maintain a high index of suspicion. Do not forget to test the distal joint to identify a subtle mallet finger injury.

1. Exam: Proper exposure

In the case of open extensor tendon injuries, achieve proper exposure to assess the tendon. This requires good lighting, analgesia, positioning, and hemostasis. Adequate analgesia can be achieved using a nerve block with lidocaine or bupivicaine.³ Next, depending on the location of the injury, use a Penrose drain or a sphygmomanometer to achieve a bloodless field [Figures 4-5].

Figure 4: The Penrose drain method to obtain digit hemostasis. A) After anesthesia is infiltrated, start by wrapping the Penrose drain from a distal to proximal direction. B) Continue wrapping until the end of the digit reached. C) Begin unwrapping the drain from distal to proximal. D) Clamp the drain to hold the Penrose in place. (Photos by Daniel Ting and Jared Baylis)

Figure 5: The sphygmomanometer method to achieve hemostasis for wounds proximal to the finger. Apply cast padding (stockinette) to the forearm, inflate a blood pressure (BP) cuff to 260 mmHg, and then clamp the cuff tubes with Kelly clamps. This is usually well tolerated by the patient for up to 15-20 minutes [6]. (Photo by Daniel Ting and Jared Baylis)

The above video from LacerationRepair.com summarizes the key points of the exam (additional pearls/pitfalls regarding the exam from the site).

One key pitfall is not having enough exposure since the actual laceration can be very small or proximal/distal to the skin laceration, such as when injury occurs while the hand is in a fist. Lacerations can be extended to properly visualize the injury [Figure 6].

Figure 6: Wounds may be extended by making small incisions (approximately 1 cm) at a 90 degree angle to the ends of the laceration, with subsequent unfolding of the skin. Often only a proximal extension of the wound is needed as it is the proximal end that is harder to find. Once unfolded, the skin is held in place using a suture or skin hooks. (Illustration by David Ting)

A video demonstrating wound extension technique can be seen below from LacerationRepair.com, along with a description of additional tests used in the diagnosis of extensor tendon injury in specific hand zones from the site.

Management

Extensor tendon injuries fall into 2 general categories: open versus closed. Both rely on a high index of suspicion and careful physical examination. Closed injuries only require splinting in a volar extension splint [Figure 7] with a hand surgery follow-up within 1 week.²

Figure 7: Volar extension splint, supporting the arm and hand in neutral position. (Photo by Daniel Ting and Jared Baylis)

Some open injuries can be repaired in the ED, and some will need delayed repair by a hand surgeon. Ultimately, all these injuries (repaired or not) need hand surgeon follow up in one week.

Figure 8: Suggested management algorithm for extensor tendon injuries of the hand. (Graphic by Daniel Ting)

Which injuries can be repaired in the ED?

• Zone I: Mallet finger, treated with continuous extension splinting of the DIP joint and referral to a hand surgeon for follow-up.⁴
• Zone II-IV: May repair in the ED ^2,3
• Zone V: Suspect a human bite from a clenched fist hitting a person’s teeth (“fight bite”).⁵ Refer for delayed repair by a hand surgeon unless the injury was caused by a sharp, clean object.⁶
• Zone VI: May repair in the ED, often easy technically because the juncturae minimize tendon retraction.²
• Zone VII and VIII: The extensor retinaculum is in this area. Excessive trauma increases risk of adhesion formation.² Refer to a hand surgeon for repair.

Contraindications to ED repair

• “No-go” hand zones (VII, VIII)
• Thumb involvement
• Open fracture
• Neurovascular compromise
• Gross contamination
• Immunocompromised patients or those who are considered elite athletes ⁴

Complete versus partial tendon disruption

Complete tendon lacerations need to be repaired. Partial tendon lacerations are more controversial; however, it is generally recommended to repair (either in the ED or OR) if the laceration involves >50% of the tendon diameter. Lacerations involving <50% usually need 6 weeks of splinting in extension with hand surgeon and hand therapist follow-up.

Choice of suture

The best choice is a braided non-absorbable suture, such as Ethibond.² Prolene can be used but is considered suboptimal because it stretches over time. Nylon sutures are sharp and can tear through the tendon.

For size, our local plastic surgeon group recommends the largest suture that the tendon can tolerate to maximize retention strength. 3-0 is a common size choice for extensor tendon repair of the hand where the tendons are thicker and can accommodate core sutures.⁷ For extensor tendon repair in the fingers, a 4-0 is often selected,^2,7 although a 3-0 or even a 2-0 could be used if the tendon is large enough.

A tapered needle is preferred as it is less traumatic when compared to a cutting needle.²

Suture strategy

There are many techniques of suture repair and you will find differing recommendations depending on your source. The figure-of-8 is an acceptable technical choice³ because:

1. It is familiar to emergency physicians.
2. The number of suture strands across the repair site correlates with tensile strength.⁸

Be gentle when manipulating the tendon to minimize additional trauma. Use only single toothed forceps on the exposed cut end of the tendon with as little force as possible.

In certain situations, a more advanced practitioner might also consider use of a grasping suture technique, demonstrated in the following video (more information on their indications).

Disposition

Even when extensor tendon injuries are repaired in the ED, hand surgeon follow-up in 7 days is required for reassessment, skin suture removal, and referral to hand physiotherapy for strengthening and range of motion. There is a dearth of evidence for prophylactic antibiotics, but they are often prescribed.^2,4 If you are unable to adequately assess a suspected extensor tendon injury, close the skin, place the arm in a volar extension splint, and refer to a hand surgeon for follow-up within 7 days.

Case Conclusion

You identify a 50% injury of the extensor tendon in zone VI of the left hand and repair the injury using 3-0 Ethibond. Subsequently, you place the arm in a volar extension splint, and send your patient for follow up with a hand surgeon. His extensor tendon injury recovers beautifully.

Take Home Points for Extensor Tendon Injuries of the Hand

1. Some extensor tendons of the hands and fingers can be repaired in the ED.
2. Adequate exposure, a bloodless field, and possible wound extension are needed to properly assess wounds for an extensor tendon injury.
3. Use 3-0 and 4-0 nonabsorbable braided sutures for extensor tendons of the hand and fingers, respectively.
4. Use a figure-of-8 technique for suturing extensor tendon lacerations in the ED.
5. Apply a volar extension splint and refer for hand surgeon follow-up within 7 days, regardless of ED repair.