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Extensor tendon injuries
The extensor tendons are divided into zones 1 to 9, with the odd zones over joints; a mallet finger in zone 1 is treated with a continuous DIP extension splint for 6 to 8 weeks, and a central slip injury in zone 3 develops into a boutonniere deformity if untreated.
Why it matters in the exam
Mallet finger: drooping of the distal phalanx after a blow to the fingertip, from tendon rupture or an avulsion fracture; treatment: a continuous DIP extension splint for 6 to 8 weeks and then a night splint for another 2 to 4 weeks — any flexion during that period restarts the count. Surgery is considered for a fracture involving more than a third of the joint surface with volar subluxation. Injury to the central slip over the PIP (zone 3) later causes a boutonniere deformity: PIP flexion and DIP hyperextension; it is diagnosed with the Elson test and treated with a PIP extension splint for about 6 weeks with the DIP free to move. The opposite swan neck deformity — PIP hyperextension and DIP flexion — follows chronic mallet finger, volar plate laxity and rheumatoid arthritis.
In zone 5, over the MCP joint, every cut is a "fight bite" until proven otherwise: a tooth strike during a punch penetrates the joint; treatment is exploration and washout in theatre, leaving the wound open and antibiotics covering Eikenella corrodens (amoxicillin-clavulanate). Sagittal band rupture causes the extensor tendon to sublux off the joint. After an undisplaced distal radius fracture the EPL tendon can rupture, and treatment is EIP transfer. The juncturae tendinum between tendons on the back of the hand can mask a cut proximal to them — the finger still extends. A partial tear of less than 50% of the tendon width usually needs no repair. After repair, protected early motion protocols (relative motion) reduce adhesions.
Key points
- Odd zones — over joints.
- Mallet finger — continuous splint for 6 to 8 weeks.
- Central slip — boutonniere; PIP extension splint.
- Fight bite — washout, open wound, amoxicillin-clavulanate.
- EPL rupture after radius fracture — EIP transfer.
Summary table
| Zone | Location | Typical injury | Treatment |
|---|---|---|---|
| 1 | DIP | Mallet finger | DIP extension splint for 6 to 8 weeks |
| 3 | PIP | Central slip — boutonniere | PIP extension splint, DIP free |
| 5 | MCP | Fight bite; sagittal band rupture | Washout in theatre and antibiotics |
| 7 | Wrist | Cut under the retinaculum | Repair and retinaculum reconstruction |
| EPL | Thumb, after radius fracture | Late rupture | EIP transfer |
Free exam questions
מה נכון לגבי ממצא קליני של ACTINIC KERATOSIS ? (the question as examined, in Hebrew)
- א. אינו מופיע בבעלי עור פיצפטריק 5 או 6
- ב. מופיע יותר בנשים ביחס לגברים
- ג. שכיח יותר באזור של אמה פלקסורי ביחס לאמה אקסטנסורי
- ד. הינו סמן ליצירת מוגברת של INVASIVE SCC
לאיזה מהגורמים הבאים יש את ההשפעה הגדולה ביותר על סיכויי התמותה סביב ניתוח אמבולטורי כגורם בלתי תלוי? (the question as examined, in Hebrew)
- א. זיהום
- ב. גיל מעל 80
- ג. מחלת לב פעילה
- ד. סרטן מפושט
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Sources
- Green's Operative Hand Surgery, 8th edition (2022) — Extensor tendon injury
- American Society for Surgery of the Hand: Hand Surgery Update, current edition — Extensor tendon zones and mallet finger
- IDSA Practice Guidelines for Skin and Soft Tissue Infections, 2014 — Human and animal bite wounds
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.