Central Slip Laceration &
Rupture
Jacksonville, FL
A cut or crush injury over the back of the middle knuckle that damages the central slip — the critical extensor tendon attachment to the middle phalanx. If missed or untreated, a boutonnière deformity develops within weeks. R. David Graham, MD at JOI repairs acute central slip lacerations and manages closed ruptures to prevent this progression.
- Central slip = extensor tendon attachment to base of middle phalanx at PIP joint
- Disruption leads to boutonnière deformity if untreated — lateral bands migrate volarly
- Acute laceration: surgical repair within days
- Closed rupture: PIP extension splinting for 6 weeks — DIP left free to flex
- Test: unable to actively extend PIP joint against resistance
- Volar PIP dislocation specifically risks central slip avulsion
The central slip is the extensor mechanism's insertion at the PIP joint. Its disruption is easy to miss — the finger may still extend passively — but active PIP extension against resistance is lost. Missing this leads to boutonnière deformity within 3–6 weeks.
Why Central Slip Injuries Get Missed
The Injury That Becomes
a Boutonnière if Missed
The central slip is the central band of the extensor tendon at the PIP joint — it inserts onto the dorsal base of the middle phalanx and is responsible for active PIP extension. When it is cut, avulsed, or ruptured, the lateral bands — the two flanking slips of the extensor mechanism — lose their dorsal stabilization and migrate volarly over time. This converts the extensor mechanism from an extension force at the PIP into a flexion force, producing the classic boutonnière deformity: PIP flexion contracture with compensatory DIP hyperextension.
The injury is missed for one consistent reason: the finger may still extend passively, and the patient and treating provider assume the extensor tendon is intact. The key test is active PIP extension against resistance — if the patient cannot maintain PIP extension when the examiner applies light flexion resistance, the central slip is not functioning. Any wound over the dorsal PIP joint, any volar PIP dislocation, or any crush injury to the dorsal middle finger must be evaluated specifically for central slip integrity.
Acute lacerations with central slip involvement are repaired surgically — the tendon is identified, freshened, and sutured, followed by PIP extension splinting for 6 weeks. The DIP joint is left free to flex actively, which actually helps centralize the lateral bands by pulling them dorsally. Closed ruptures (no skin wound) are managed with strict PIP extension splinting for 6 weeks with active DIP flexion — the same biological principle applied without surgery.
- → Can patient passively extend PIP? Often YES — does not confirm central slip intact
- → Can patient actively extend PIP against resistance? NO if central slip disrupted
- → Elson test: PIP held at 90° over table edge — DIP goes rigid if central slip ruptured
- → Any dorsal PIP wound: assume central slip involvement until proven otherwise
- → Volar PIP dislocation: central slip avulsion risk — must assess after reduction
- → Untreated: boutonnière deformity in 3–6 weeks
Treatment
Acute Repair for Lacerations — Splinting for Closed Ruptures
Acute Laceration — Surgical Repair
Central slip lacerations are repaired in the operating room through the existing wound or a small extension of it. The tendon ends are identified, debrided to fresh tissue, and repaired with a non-absorbable core suture and epitenon running stitch. The PIP joint is pinned in extension (K-wire) or splinted strictly in extension for 6 weeks. The DIP joint is encouraged to flex actively to keep the lateral bands mobilized. Formal hand therapy at 6 weeks guides progressive PIP mobilization.
Closed Rupture — Extension Splinting
Closed central slip ruptures (no skin wound — from forced PIP flexion, volar dislocation, or crush) are managed with strict PIP extension splinting for 6 weeks. The splint holds the PIP in full extension 24 hours a day — it is not removed for bathing or dressing. The DIP joint is left free and the patient actively flexes it frequently, which helps keep the lateral bands in a dorsal position. At 6 weeks, progressive PIP flexion begins under therapy supervision.
What Happens if a Central Slip Injury Is Missed
Within 3–6 weeks of untreated central slip disruption, the lateral bands complete their volar migration and become fixed in a position that actively flexes the PIP joint. The PIP develops a fixed flexion contracture — the boutonnière deformity. At that point, the injury is no longer a tendon repair problem; it is a deformity correction problem. A flexible boutonnière deformity is managed with splinting and therapy. A fixed boutonnière requires surgical correction — PIP fusion is preferred over arthroplasty for fixed boutonnière, as Dr. Graham has discussed. Identifying the central slip injury at the time of the original wound and initiating 6 weeks of extension splinting prevents this entire cascade.
FAQs
Frequently Asked Questions
Related Conditions
Next Steps
Injury over the back of the
middle knuckle — assess the central slip.
Central slip injuries are time-sensitive. Six weeks of extension splinting started within days of injury prevents boutonnière. Started after the deformity has developed, treatment is significantly more difficult. Walk-ins seen same day via JOI Now.
Jacksonville Beach, FL 32250
Walk-ins welcome via JOI Now for acute finger injuries.