High-yield overview
Zone III Extensor Tendon Injury
PIPJFlexion Deformity
DIPJHyperextension
6wSplint Duration
Zone 3Anatomic Zone
Burton Classification
Stage I
PatternSupple deformity (passive correctable).
Treatment
Stage II
PatternFixed deformity (contracture).
Treatment
Stage III
PatternFixed deformity with arthritis.
Treatment
Pseudo
PatternHyperextension injury (Volar plate).
Treatment
Critical Must-Knows
- Caused by rupture of the Central Slip insertion (Zone III).
- Lateral bands subluxate volarly (below axis of rotation) to become PIPJ flexors.
- The Triangular Ligament must stretch/fail to allow band subluxation.
- Elson's Test is the most sensitive clinical sign for acute central slip injury.
- Treatment requires splinting the PIPJ in extension while allowing the DIPJ to flex (this pulls lateral bands dorsal).
- Chronic deformities (Type II/III) are very difficult to treat surgically.
Clinical Pearls
- "If the patient can extend the DIPJ while the PIPJ is held at 90 degrees, the Central Slip is intact.
- "The deformity is progressive; acute injuries may not show deformity immediately.
- "The 'Buttonhole' refers to the head of the proximal phalanx popping through the lateral bands.
Clinical Imaging
Imaging Gallery
The Diagnostic Trap
The Problem
Acute Presentation Initially, only the central slip is ruptured. The lateral bands have NOT yet subluxed. The finger looks straight or only slightly swollen. The classic deformity takes 10-14 days to develop as the triangular ligament stretches. Missing this leads to a fixed deformity.
The Solution
Elson's Test You MUST perform Elson's test on any "jammed" finger with dorsal PIPJ tenderness. Assume rupture until proven otherwise. Treat with "Safety Splinting" if unsure.
| Condition | Pathology | PIPJ | DIPJ |
|---|---|---|---|
| Boutonniere | Central Slip Rupture | Flexed | Hyperextended |
| Swan Neck | Volar Plate Laxity | Hyperextended | Flexed |
| Pseudo-Boutonniere | Volar Plate Injury | Flexed | Normal/Stiff |
| Mallet | Terminal Tendon | Normal | Flexed |
Mnemonic
SLIDEPathomechanics
| S | Subluxation Lateral bands slide volar. |
| L | Ligament Triangular ligament fails. |
| I | Insertion Central slip insertion rupture. |
| D | DIPJ DIPJ hyperextension (increased pull). |
| E | Extension Loss of PIPJ extension. |
| S | Subluxation Lateral bands slide volar. | D | DIPJ DIPJ hyperextension (increased pull). |
| L | Ligament Triangular ligament fails. | E | Extension Loss of PIPJ extension. |
| I | Insertion Central slip insertion rupture. |
Hook:The bands SLIDE down.
Mnemonic
FLOPElson's Test Interpretation
| F | Floppy DIPJ is floppy (loose) in rupture. |
| L | Locked DIPJ is locked (taught) in normal. |
| O | Open Open injury check. |
| P | Pain Pain over dorsal PIPJ. |
| F | Floppy DIPJ is floppy (loose) in rupture. | O | Open Open injury check. |
| L | Locked DIPJ is locked (taught) in normal. | P | Pain Pain over dorsal PIPJ. |
Hook:A ruptured central slip makes the DIPJ FLOP.
Mnemonic
FREEManagement Goals
| F | Free DIPJ Allow DIPJ flexion. |
| R | Retract Retract lateral bands dorsally. |
| E | Extend PIPJ Maintain PIPJ extension. |
| E | Exercise Active DIP flexion exercises. |
| F | Free DIPJ Allow DIPJ flexion. | E | Extend PIPJ Maintain PIPJ extension. |
| R | Retract Retract lateral bands dorsally. | E | Exercise Active DIP flexion exercises. |
Hook:FREE the DIPJ to fix the PIPJ.
Overview
Definition
Boutonniere deformity is a flexion deformity of the PIPJ coupled with hyperextension of the DIPJ, resulting from dysfunction of the central slip of the extensor mechanism.
The term "Boutonniere" (French for Buttonhole) describes the condyles of the proximal phalanx protruding dorsally through the defect between the lateral bands.
Pathophysiology and Mechanisms
Normal Extensor Anatomy (Zone III)
- Central Slip: Inserts into the dorsal base of the Middle Phalanx. Extends the PIPJ.
- Lateral Bands: Run laterally. Join distally to form Terminal Tendon.
- Triangular Ligament: Connects the two lateral bands dorsally over the Middle Phalanx. Prevents them falling volar.
- Transverse Retinacular Ligament: Connects lateral bands to the volar plate. Pulls them volar.
The interplay between the Triangular and Transverse ligaments is critical for stability.
Classification Systems
Burton Classification
- Stage I: Supple. Passive correction of PIPJ is possible.
- Stage II: Fixed deformity. Contracture of lateral bands.
- Stage III: Fixed deformity + Arthritis.
Stage I is treatable with splinting. Stage II requires surgical release or serial casting.
Clinical Assessment
Examination
- Deformity: Look for PIP flexion and DIP hyperextension.
- Open: Check for dorsal laceration.
- Tenderness: Dorsal base of Middle Phalanx.
- Boyes Test: Test for tightness of oblique retinacular ligament.
Early changes can be subtle. Compare with the other hand.
Investigations
Radiology
- Views: AP and Lateral.
- Findings:
- Avulsion: May see bony fleck from dorsal base of P2.
- Joint: Assess for OA (Stage III).
- Subluxation: Volar subluxation of middle phalanx may be visible.
- Soft Tissue: Swelling dorsal to PIPJ.
Bony avulsion is treated similarly to tendinous rupture (Splinting), unless huge displaced fragment.
Management Algorithm
Algorithm
Conservative Management (Stage I)
- Goal: Restore central slip continuity + Move lateral bands dorsal.
- Splint: PIPJ in FULL extension (block extension).
- DIPJ: LEFT FREE. Must be flexed actively.
- Mechanism: Active DIP flexion while PIP is extended pulls the lateral bands distally and dorsally (via Triangular ligament), reducing them.
- Duration: 6 weeks continuous.
- Follow-up: Weekly review to ensure compliance and splint fit.
This is known as the "Safety Splint" position.
Surgical Considerations
Acute Repair
- Approach: Dorsal zig-zag incision centered over PIPJ.
- Repair: 4-0 non-absorbable mattress suture into central slip.
- Fixation: K-wire across PIPJ in extension for 3-4 weeks.
- Triangular Ligament: Must be repaired to prevent lateral band subluxation.
- Closure: Skin closure over buried sutures.
Do not overtighten the central slip, or you will cause a DIPJ extension lag. The goal is merely to appose the tendon ends, not to create tension.
Complications
- Stiffness: Loss of PIP flexion is common after prolonged splinting.
- DIPJ Lag: If lateral bands are tight.
- Recurrence: If triangular ligament is incompetent.
- Skin Necrosis: From tight splints.
- Hypersensitivity: Often managed with desensitization.
- DIPJ Hyperextension: If the central slip is overtightened during repair.
- Quadriga Effect: If the FDP is tethered.
- Infection: Post-operative, or from the initial injury (human bite?).
Rehabilitation
Week 0-6
- Splint: PIPJ straight (full extension). DIPJ left free.
- Exercises: Active DIPJ flexion 20 reps every hour while awake.
- Mechanism: Active DIP flexion pulls lateral bands distally and dorsally via the oblique retinacular ligament, encouraging dorsal relocation.
- Hygiene: Remove splint 1-2 times daily for skin care while holding PIP extended.
- Edema Control: Coban wrap, elevation.
Week 6-8
- Wean: Start gentle active PIP flexion (20-30°) initially.
- Progression: Increase arc 10° per week based on extensor lag.
- Monitor: If extensor lag greater than 10° recurs, back to full-time splint.
- Night Splint: Continue at night for additional 4 weeks.
- Exercises: Active assisted and passive ROM.
Week 8-12
- Full Activity: Gradual return by 12 weeks.
- Grip Strengthening: Theraputty, grip exercises.
- Night Splint: May continue for 3-6 months in some patients.
- Functional Goals: Return to sport/work-specific activities.
Splint Types
- Cylinder Splint: Simple, inexpensive, good for initial immobilization.
- Capener Splint: Dynamic splint with spring mechanism for chronic deformity.
- Safety Pin Splint: Low-profile, allows more function.
- Serial Casting: For fixed Stage II deformity to gain passive extension.
Red Flags During Rehabilitation
- Extensor lag greater than 15° on weaning
- Increasing flexion contracture
- Pain at terminal extension (tendon healing issue)
- Skin breakdown under splint
Prognosis
- Acute: Excellent prognosis if splinted early (within 3 weeks of injury).
- Chronic: Poor prognosis. Reconstruction often swaps deformity for stiffness.
- Bony: Good prognosis with union if avulsion fragment adequately reduced.
- Arthritis: Long term consequence of uncorrected subluxation.
- Function: Even with some residual deformity, hand function can remain good if range is preserved.
- Patient Satisfaction: Often higher with a slightly deformed but mobile finger than a straight but stiff one.
- Chronic Pain: Rare, unless secondary arthritis develops.
- Cosmesis: The main complaint for many patients.
Prognostic Factors
- Time to Treatment: Early treatment (less than 3 weeks) = better outcomes.
- Stage at Presentation: Stage I has superior outcomes compared to Stage II/III.
- Compliance: Poor splint compliance leads to recurrence.
- Age: Younger patients heal better but may be less compliant.
- Occupation: Manual workers may require longer rehabilitation.
Evidence Base
Elson's Test — Original Description (Landmark)
Elson RA • J Bone Joint Surg Br (1986)
Technique description / clinical method
Key Findings:
- Closed central slip rupture is easily missed until the late buttonhole deformity appears, by which time Boyes' test (DIP flexion with PIP held extended) is already positive
- New test: with the PIP flexed 90° over a table edge, the patient extends against resistance — absence of PIP extension force PLUS fixed (rigid) DIP extension signals complete central slip rupture
- Allows diagnosis in the acute phase, before deformity develops, when treatment outcomes are best
Clinical Implication: The defining clinical test for acute central slip injury — trust a positive Elson test over a normal-looking finger and a normal radiograph.
Biomechanics of the Acute Boutonniere (Cadaveric)
Grau L, Baydoun H, Chen K, et al • J Hand Surg Am (2017)
Cadaveric biomechanical study (18 fresh hands)
Key Findings:
- Central slip detachment alone produced only loss of PIP extension — NOT a boutonniere deformity
- A boutonniere developed only when the central slip, the triangular ligament, AND the transverse/oblique interosseous hood fibres were all divided
- Lateral band subluxation volar to the PIP axis of rotation is required to generate the deformity
Clinical Implication: A substantial extension loss or frank deformity implies damage beyond the central slip — explains why the deformity evolves over days as the triangular ligament attenuates.
Extensor Tendon Injuries at the PIP Joint (Zone III)
Pillukat T, Windolf J, Schädel-Höpfner M, et al • Unfallchirurg (2021)
Review of diagnosis and management
Key Findings:
- Acute closed central slip injuries are a clinical diagnosis (Elson test) after bony injury is excluded radiographically
- Non-displaced avulsions and lacerations can be splinted; displaced avulsions and complex injuries are surgical
- Fixed deformities must have full passive PIP extension restored (hand therapy or release) BEFORE any tendon reconstruction
Clinical Implication: Stage the chronic deformity: convert fixed to supple first, then reconstruct.
Controversies and Areas of Uncertainty
Where the evidence is thin
There are no randomised controlled trials comparing splinting regimens or operative techniques in boutonniere deformity. Recommendations rest on cadaveric biomechanics, case series, and expert consensus — a frequent examiner probe.
- Optimal splint position and type: Static PIP extension splinting is standard, but relative-motion (yoke) splinting and serial casting all have advocates. There is no high-level evidence that any one orthosis is superior, and the construct material (thermoplastic vs aluminium-foam vs cast) is far less important than position and compliance.
- Bony avulsion threshold for surgery: The fragment size or articular involvement that mandates fixation over splinting is not precisely defined; most non-displaced or small avulsions do well with extension splinting, mirroring tendinous injury.
- Surgery for chronic deformity: Reconstruction reliably trades PIP extension for flexion. Whether to operate at all in a functional but cosmetically displeasing finger is genuinely debated — many authorities advise against surgery when the hand is functional.
- Choice of reconstruction: Anatomical central slip reconstruction, lateral band relocation (Littler), terminal/Dolphin tenotomy (Fowler-type), and tendon transfer/graft each have proponents; comparative data are limited and largely retrospective.
- Imaging role: Ultrasound and MRI can demonstrate the central slip, but the diagnosis remains clinical (Elson test). Whether imaging changes management in equivocal closed cases is unproven.
Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
CLINICAL SCENARIOStandard
Scenario 1: The 'Jammed' Finger
CLINICAL PROMPT
"A basketball player presents with a swollen PIPJ. X-ray is normal. The finger looks straight. What is your exam?"
PRACTICAL APPROACH
I am concerned about a Central Slip injury. I would examine for point tenderness at the dorsal PIPJ. Crucially, I would perform Elson's Test. I place the PIPJ over the table edge at 90 degrees and ask for extension against resistance. If the DIPJ is floppy, it's normal. If the DIPJ is rigid/extends, it's a rupture. If confirmed, I treat with a splint for 6 weeks.
KEY CLINICAL POINTS
Specific exam (Elson's)
Mechanism of injury
Treatment of occult injury
COMMON PITFALLS
Dismissing as a 'sprain' because X-ray is normal
Waiting for deformity to appear
FURTHER QUESTIONS
"What if you are unsure?"
"Treat as a rupture. Splinting is safe. Missing it is disastrous."
CLINICAL SCENARIOStandard
Scenario 2: Chronic Presentation
CLINICAL PROMPT
"A patient presents 3 months post injury with a fixed 45 degree flexion deformity of the PIPJ and hyperextended DIPJ. Management?"
PRACTICAL APPROACH
This is a Stage II Boutonniere. The lateral bands are contracted. Splinting alone will not work initially. I would start with Serial Casting to regain passive extension. Once supple (Stage I), I would use a Capener splint. If casting fails to gain extension, surgical release (check-rein ligaments/volar plate) and lateral band reconstruction is needed.
KEY CLINICAL POINTS
Distinguishing Stage I vs II (Fixed vs Supple)
Role of Serial Casting
Capener Splint (Dynamic)
COMMON PITFALLS
Offering tendon repair on a stiff joint
FURTHER QUESTIONS
"What is the surgical salvage?"
"PIPJ Arthrodesis (Fusion)."
CLINICAL SCENARIOStandard
Scenario 3: The Open Laceration
CLINICAL PROMPT
"A patient has a deep laceration over the dorsal PIPJ. Tendon is visible. Mechanism is a glass cut."
PRACTICAL APPROACH
This is an open central slip injury. It requires surgical repair. I would wash out the wound. I would repair the central slip with a 4-0 non-absorbable mattress suture. I would also repair the triangular ligament to prevent subluxation. Post-operatively, I would K-wire the PIPJ in extension for 3 weeks to protect the repair, then mobilize.
KEY CLINICAL POINTS
Surgical indication (Open)
Repair technique
Importance of Triangular Ligament
COMMON PITFALLS
Repairing skin only
Ignoring the lateral band stability
FURTHER QUESTIONS
"Can you just splint it?"
"If the tendon ends are apposed, maybe. But usually they retract. Direct repair is safer for open wounds."
CLINICAL SCENARIOStandard
Scenario 4: Rheumatoid Patient
CLINICAL PROMPT
"A 55-year-old female with known rheumatoid arthritis presents with bilateral Boutonniere deformities affecting the index and middle fingers of both hands. Her PIP joints are passively correctable. How do you manage her?"
PRACTICAL APPROACH
This is Nalebuff mild-moderate rheumatoid Boutonniere. The bilateral nature is typical for RA. Since the deformities are passively correctable (supple), I would start with conservative management: bilateral cylinder splints for PIP extension with active DIP flexion exercises. I would optimize her rheumatoid disease control with her rheumatologist. If splinting fails after 6-8 weeks, I would consider surgical options like lateral band relocation or extensor reconstruction, prioritizing the dominant hand and most functionally limiting fingers first.
KEY CLINICAL POINTS
Recognize rheumatoid Boutonniere as different entity
Bilateral disease management
Coordination with rheumatology
Conservative before surgical in RA
COMMON PITFALLS
Operating on all fingers at once
Ignoring systemic disease control
Expecting perfect results in RA
FURTHER QUESTIONS
"What if she has DIPJ involvement too?"
"RA can cause combined Swan Neck and Boutonniere in different fingers. Treat the most functionally limiting deformity first. Consider arthrodesis for painful stiff DIPs."
MCQ Practice Points
Diagnosis
Q: What is the hallmark finding of a positive Elson's test? A: Rigid extension of the DIPJ when PIPJ is flexed (due to lateral band over-pull).
Anatomy
Q: Which structure limits the dorsal migration of the lateral bands? A: The Transverse Retinacular Ligament.
Management
Q: In splinting for Boutonniere deformity, what is the position of the DIPJ? A: Free / Flexed. (Active flexion recruits lateral bands).
Pathology
Q: What defines a Stage II deformity? A: Fixed flexion contracture (not passively correctable).
Anatomy Mechanism
Q: Why do the lateral bands become PIPJ flexors in Boutonniere? A: They subluxate volar to the axis of rotation of the PIPJ, converting their pull from extension to flexion.
Treatment Duration
Q: How long should a Boutonniere splint be worn continuously? A: 6 weeks continuous, then progressive weaning with night splinting for months.
Guidelines, Registries & Global Practice
Global Epidemiology
- Traumatic: Closed central slip injury is a ball-sport and contact-sport injury worldwide (basketball, volleyball, football/soccer, rugby, Australian football, cricket, handball) from forced PIP flexion against an actively extending finger, plus axial-load "jamming". Peak incidence in active adults aged 20–40.
- Open: Lacerations over the dorsal PIP (knife, glass, machinery, bites) account for the open subgroup and are at high risk of being missed.
- Inflammatory: Rheumatoid arthritis is the leading non-traumatic cause and is typically bilateral and multi-digit; psoriatic arthritis and SLE contribute. With modern biologic disease control the incidence of advanced rheumatoid boutonniere has fallen.
Side-by-Side Guidance (where emphasis differs)
There is no single randomised-trial-based society guideline for boutonniere; the consensus across hand-surgery bodies is convergent.
| Body / Source | Core recommendation | Practical emphasis |
|---|---|---|
| ASSH / J Hand Surg (US) | Acute closed: PIP extension splint, DIP free for active flexion; surgery for open / displaced bony avulsion / failed conservative | Evidence-based reviews caution that surgery trades PIP extension for flexion |
| BSSH / BOA (UK) | Same splinting principle; emphasises early diagnosis with Elson test and hand-therapy-led splinting | Hand therapists fabricate and supervise relative-motion / PIP extension orthoses |
| FESSH / European hand surgery | Clinical diagnosis (Elson), splint non-displaced injuries, restore passive extension before reconstructing fixed deformity | Staged approach to chronic / fixed deformity |
| IFSSH consensus | Central-slip-protective splinting; reserve reconstruction for selected chronic cases | Realistic goal-setting; function over cosmesis |
Registry and Outcome Notes
- No implant registry applies — boutonniere management is soft-tissue and splint-based, so arthroplasty/implant registries (NJR, AJRR, AOANJRR) do not capture it. Evidence is drawn from cadaveric biomechanical work and surgical case series rather than registry data.
- Surgical series (e.g. Towfigh & Gruber, 172 patients) report roughly two-thirds excellent/good results after reconstruction, with a consistent minority of satisfactory/poor outcomes — a pattern echoed across the literature.
High- vs Limited-Resource Practice Variation
- High-resource settings: Custom thermoplastic and relative-motion orthoses fabricated by certified hand therapists; ultrasound or MRI available for equivocal cases; structured graded rehabilitation.
- Limited-resource settings: Prefabricated splints, low-cost aluminium-foam (Zimmer-type) or plaster cylinder casts, and serial casting deliver equivalent biomechanics — the central slip does not "know" what the splint is made of. Early, correctly positioned, consistently worn immobilisation matters far more than splint cost.
- Universal barrier: Compliance with 6 weeks of continuous PIP extension splinting (heat, skin maceration, manual-work demands) is the dominant determinant of success in every health system; patient education and review drive outcomes more than any device.
Clinical summary
Classification
- •Stage I: Supple (Splint)
- •Stage II: Fixed (Cast/Release)
- •Stage III: Arthritis (Fuse)
- •Pseudo: Volar plate injury
Management
- •Splint PIP Extension
- •DIP Free (Exercise)
- •6 Weeks Continuous
- •Elson's Test is Key
Anatomy
- •Central Slip Rupture
- •Lateral Bands Volar
- •Triangular Lig Failure
- •Zone III