Because there is little to protect the extensor tendons (thin skin, minimal subcutaneous tissue), they can be easily injured by knives, saws, teeth (hitting someone), etc. The extensor tendon anatomy can be reviewed here online, or in more depth offline using a good anatomy or hand surgery text.
These injuries will often include fractures or soft tissue injuries (lacerations, crush, loss of skin, etc). This post is only a brief overview of the repair of "isolated" extensor tendon laceration at the time of injury, not reconstructively later. This post will in no way make the reader an expert on extensor tendon injury/repair, but will give you a general understanding (maybe).
Injuries of the extensor tendon are defined by zones. The tendon injuries in finger Zones II-IV and VII tend to fare worse than injuries in the other zones.
Zone I --
- DIP joint of the fingers
- IP joint of the thumb
- Middle Phalanx of the fingers
- Proximal Phalanx of the thumb
- PIP joint of the fingers
- MP joint of the thumb
- MP joint of the fingers
- CMC joint/radial styloid of the thumb
Zone VI -- Dorsum of the hand
Zone VII -- Dorsal retinaculum
Zone VIII -- Distal forearm
Primary suture of extensor tendon lacerations in all zones is the accepted standard. Indications for the need to repair include:
- Tendon laceration greater than 50%
- Tendon laceration less than 50% with significantly decreased strength compared with contralateral finger (the finger next to the one injured)
- Tendon laceration associated with significant overlying skin loss, joint space penetration, or bony fracture
Reasons not to do a primary repair include:
- Skilled physician unavailable in which case simple closure of the skin to aid in prevention of infection until the patient can be seen by a hand surgeon, sooner rather than later in a perfect world.
- Contaminated injury, particularly open zone 5 "fight bite" injury. The injury due to hitting someone in the mouth.
- Presence of bony fracture, open joint space, or significant overlying skin loss (requires an orthopedist or hand surgeon for repair) See the injury posted by Shadowfax last week.
Treatment by zone of injury
Zone I -- Mallet Finger, see my post from last year
- Extension splinting of just the DIP joint has become
the standard of care for most mallet injuries. Splinting is continuous for a period of 6 to 8 weeks and may be continued longer. (photo credit)
- Indications for operative treatment are controversial. The three most often indications include (1) open injuries, (2) those individuals who are noncompliant or unable to tolerate
a splint, and (3) in cases where there exists a large dorsal fragment with palmar subluxation of the distal phalanx.
Zone II -- Injuries are typically seen with sharp lacerations, saw injuries, and crush injuries.
- Acute lacerations with extensor lag present on examination need to be explored and repaired.
- If there is active extension with some weakness against resistance, it can be treated with splinting for 3 to 4 weeks.
- A running core suture oversewn with a epitendinous stitch is recommended for the repair.
Zone III --
- The treatment of acute injuries is designed to prevent the boutonniere deformity.
- Closed injuries should be treated with splinting alone. (photo credit)
- Partial lacerations encompassing greater than 50 percent and complete lacerations are repaired with a modified Kessler technique or modified Bunnell suture using a 5-0 non-absorbable suture. (photo credit)
- Postoperatively, the patient is placed in a volar positioning splint.
- For the first 3 weeks, passive extension is allowed in the splint.
- At week 4, gentle active extension is monitored.
- No passive flexion is allowed at any time for the first 4 weeks. After 4 weeks active flexion is initiated and graded resistive exercises are added to the regimen.
Zone V --
- The injuries here may divide the sagittal band allowing the tendon to shift laterally. If this is not repaired, the patient may have difficulty with extension of the the proximal phalanx.
- Use of the modified Kessler or modified Bunnell is a good choice.
- The patient is placed in a dynamic extension splint for early mobilization. During the initial 4 weeks, the patient is allowed to perform active flexion to 30 degrees of MCP joint motion with passive extension by means of rubber band traction.
- The range of motion is increased gradually over the ensuing several weeks to full by the 5th week.
- After 5 weeks, the dynamic extension splint can be discontinued, provided there is no extensor lag or other complications present to interfere with motion.
- Once the splint is discontinued, the patient may begin active extension and flexion.
- Eventually, graded resistive exercises are begun to augment strength and mobility.
Zone VI --
- Injuries through or just distal to the juncturae tendinum may be difficult to diagnose because of the minimal extensor lag associated with these injuries.
- Injuries occurring proximal to the juncturae may result in retraction of the proximal tendon stump. This makes repair technically more challenging.
- Here the tendons are very superficial, covered only with thin paratenon and scant subcutaneous tissue. Degloving injuries are not uncommon and may require grafting, or local versus distant flap coverage.
- Modified Bunnell using 4-0 nonabsorbable suture is a good way to repair the tendons in this zone.
- Postoperative dynamic splinting and therapy is similar to Zone V.
Zone VII --
- Injuries in this zone may have the worst prognosis as the injuries may produce mass healing of tendons to the underlying joint capsule and surrounding retinaculum. All of that may impair tendon excursion (sliding/movement) after healing and frequently results in a tenodesis of the tendons at the wrist.
- Injuries in the wrist will often require releasing the retinaculum for visualization and repair. As much of the extensor retinaculum should be preserved as possible to prevent bowstringing of the tendons.
- Modified Bunnell or modified Kessler using a 4-0 nonabsorbable suture
- Early dynamic splinting may prevent or minimize postoperative adhesions. Often the same postop regimen as for Zone 4 is used.
Zone VIII --
- Injuries in the forearm may involve extensor muscle bellies, tendons, or the musculotendinous junctions.
- Actual muscle injuries should be repaired with liberal figure-of-8 stitches.
- Static mobilization for 5 to 6 weeks with the wrist extended to approximately 45 degrees is recommended.
Thumb Zones I - III
- Repair is similar to that of the fingers.
- A thumb spica splint is used initially. During the first 3 weeks, the wrist is positioned to 30 degrees of extension. The thumb, CMC, MCP, and IP joints are all held in an extended
- At week 3, gentle active extension of those joints is initiated.
- At weeks 4 to 5, there is continued gentle active extension with the addition of gentle active flexion of the same joints.
- At week 6 and beyond, graded resistive exercises are initiated.
Extensor Tendon Repair; eMedicine Article, July 22, 2007; Adam J Rosh, MD, MS and Nancy S Kwon, MD,MPA
Mallet Fracture; eMedicine Article, June 17, 2008; Michael E Robinson, MD
Boutonniere Deformity; eMedicine Article, Jan 11, 2008; Randle L Likes, DO and Sean D Ghidella, MD
Extensor Mechanism of Fingers; Duke Orthopaedics Wheeless' Textbook of Orthopaedics Online
Extensor Mechanism Anatomy, Biomechanics and Closed Rupture of Digital Extensor Tendons; E-Hand.com; Charles Eaton, MD
Doyle, J. R. Extensor tendons: Acute injuries. In D. P. Green (Ed.), Green's Operative Hand Surgery, 5th Ed. Philadelphia: Elsevier Churchill Livingstone, 2005.
Extensor Tendon Injuries: Acute Management and Secondary Reconstruction; Plastic and Reconstructive Surgery:Volume 121(3)March 2008pp 109e-120e; Kevin R. Hanz, M.D.; Michel Saint-Cyr, M.D.; Maynard J. Semmler, O.T.R.; Rod J. Rohrich, M.D.