Extensor Tendon Injuries

High Yield Overview

EXTENSOR TENDON INJURIES

Verdan Zones | Mallet Finger | Boutonnière | Elson's Test

Zone IMallet finger - most common closed tendon injury

Zone IIICentral slip rupture → Boutonnière

6-8 wksSplinting duration for Zone I (Mallet)

OddOdd zones = Joints (I, III, V, VII)

Critical Must-Knows

Verdan Zones: Odd = Joints (I=DIP, III=PIP, V=MCP, VII=Wrist). Even = Bones
Mallet (Zone I): Stack splint DIPJ extension 6-8 weeks. Bony mallet with greater than 1/3 articular = surgery
Boutonnière (Zone III): Central slip rupture → lateral bands migrate volar → PIPJ flexion, DIPJ hyperextension
Elson's Test: Flex PIPJ 90°, extend against resistance. Intact = floppy DIP. Torn = rigid DIP (lateral bands tighten)
Sagittal Band (Zone V): 'Boxer's knuckle' - tendon subluxates ulnarly between knuckles

Examiner's Pearls

"
Active DIP flexion exercises MANDATORY in Boutonnière splinting (pulls lateral bands dorsal)
"
Juncturae tendinum can mask proximal lacerations - test each finger independently
"
Zone V lacerations often penetrate joint capsule - requires washout
"
Relative Motion Splinting (Yoke) now gold standard for Zone V-VI repairs

Clinical Imaging

Imaging Gallery

Exam Warning

Elson's Test

Central Slip Integrity. Flex PIP 90°. Ask to extend. Rigid DIP = Torn Central Slip. Floppy DIP = Intact.

Verdan Zones

Odd = Joints. I=DIP, III=PIP, V=MCP. Even = Bones.

Mallet Splinting

Continuous Extension. 6-8 weeks 24/7. Even 1 second of flexion resets the clock.

Anatomy

Verdan's Zones (Extensor)

Odd Numbers are Joints!

Zone I: DIP Joint (Mallet Finger).
Zone II: Middle Phalanx.
Zone III: PIP Joint (Central Slip / Boutonnière).
Zone IV: Proximal Phalanx.
Zone V: MCP Joint (Sagittal Bands).
Zone VI: Metacarpal.
Zone VII: Carpus (Retinaculum).
Zone VIII: Distal Forearm.
Zone IX: Musculotendinous Junction.

At a Glance

Extensor tendon injuries are classified by Verdan zones (I-IX)—odd numbers are joints, even numbers are bones. Zone I (DIP/Mallet finger) is the most common closed tendon injury: treat with Stack splint in extension for 6-8 weeks. Zone III (PIP/Boutonnière) involves central slip rupture causing lateral band volar migration; requires extension splinting for 6 weeks with active DIP flexion exercises to prevent deformity. Elson's test diagnoses central slip injury: with PIP flexed 90°, if the central slip is torn, the DIP becomes rigid (lateral bands tighten). Zone V (MCP) sagittal band rupture ("Boxer's knuckle") causes extensor subluxation into the valley between knuckles. Unlike flexors, extensors are flat with less excursion and prone to gapping.

Mnemonic

M-B-SFinger Deformities by Zone

Mallet

Zone I (DIP) - DIP flexed, cannot extend

Boutonnière

Zone III (PIP) - PIP flexed, DIP hyperextended

Swan Neck

Zone I chronic - PIP hyperextended, DIP flexed

Mnemonic

ODD = JOINTSVerdan Zones

DIP Joint

Terminal tendon - Mallet finger territory

III

PIP Joint

Central slip - Boutonnière territory

MCP Joint

Sagittal bands - Boxer's knuckle

VII

Wrist

Extensor retinaculum - adhesion risk

Mnemonic

F-RElson's Test Interpretation

Floppy DIP

Central slip INTACT - lateral bands loose

Rigid DIP

Central slip TORN - lateral bands tighten

Specific Injuries

Zone I: Mallet Finger

Pathology:

Rupture of terminal extensor tendon at insertion.
+/- Bony avulsion.

Management:

Closed (Soft tissue): Stack splint (DIPJ extension ONLY) for 6-8 weeks. 24/7 wear.
Bony Mallet: If fragment greater than 1/3 of articular surface or subluxed -> Extension block pinning (Ishiguro) or ORIF.
Chronic: Tenodermodesis.

Zone III: Boutonnière Deformity

Pathology:

Rupture of Central Slip at PIPJ.
Lateral bands migrate Volar to axis of rotation -> Become flexors of PIPJ.
Result: PIPJ Flexion + DIPJ Hyperextension.

Management:

Acute: Splint PIPJ in extension for 6 weeks. Active DIPJ flexion exercises mandatory (pulls lateral bands dorsal).
Open: Repair central slip if avulsed.

Zone V: Sagittal Band Rupture

Pathology:

Usually Middle Finger.
"Boxer's Knuckle" (often confused with MCP fracture).
Tendon subluxates into "valley" between knuckles (usually Ulnar direction).
Patient cannot extend MCP from full flexion, but can maintain extension if placed there.

Management:

Acute: Yoke splint (holds extension) 4-6 weeks.
Chronic: Surgical realignmnent.

Elson's Test

To test Central Slip (Zone III): Flex PIPJ 90° over table edge. Ask patient to extend against resistance. If Central Slip INTACT: Strong extension, DIPJ remains floppy. If Central Slip TORN: Weak extension, DIPJ becomes rigid (Lateral bands tighten).

Clinical Context: Crucial to diagnose acute Zone III injury before Boutonnière develops.

Management Principles

Repair Techniques

Extensor Tendons (Zone IV-VI):

Tendons are flatter and thinner than flexors.
Core suture often simpler (e.g., Mattress suture or 2-strand Kessler).
Epitendinous running suture strongly recommended.
Rehab: Dynamic extension splinting or Early Active Motion (Relative Motion Splinting).

Relative Motion Splinting (ICAM):

Recent trend.
Splint holds injured finger in relative extension compared to neighbours.
Allows immediate hand use.
Fewer adhesions.

Relative Motion Splinting

Merritt WH. • J Hand Ther (2014)

Key Findings:

Relative Motion Extension (RME) splinting allows immediate active motion
Holding injured finger extended relative to adjacent fingers relaxes the repair
Evidence shows faster return to function and strength compared to static splinting for Zones IV-VII

Clinical Implication: Consider Yoke/Relative Motion splints for zone V/VI repairs instead of bulky forearm splints.

Mallet Finger Outcomes

Handoll HH, Vaghela MV. • Cochrane Database Syst Rev (2004)

Key Findings:

Conservative splinting effective for soft tissue mallet finger
No significant difference between splint types (Stack, Zimmer)
Compliance with 24/7 splinting is the key to success
Most patients have minor residual extensor lag but good function

Clinical Implication: Stack splinting remains gold standard for Zone I - surgery rarely needed for soft tissue injuries.

Elson's Test for Central Slip

Elson RA. • J Hand Surg Br (1986)

Key Findings:

Described clinical test for central slip integrity
Rigid DIP with attempted PIP extension = positive (torn central slip)
Lateral bands tighten when central slip is disrupted
Test must be performed before Boutonnière deformity develops

Clinical Implication: Essential bedside test to diagnose acute Zone III injury before chronic deformity develops.

Boutonnière Deformity Prevention

Cardon LJ et al. • J Hand Surg Am (1999)

Key Findings:

Early PIP extension splinting prevents Boutonnière deformity
Active DIP flexion exercises critical to reposition lateral bands dorsally
Chronic deformity much harder to treat than acute injury
6 weeks of splinting required for central slip healing

Clinical Implication: Active DIP flexion during Zone III splinting prevents lateral band volar migration.

Complications

Complications of Extensor Injury

References

Doyle JR. Extensor tendons: acute injuries. Operative Hand Surgery. 1993.
Elson RA. Rupture of the central slip of the extensor hood of the finger. A test for early diagnosis. J Hand Surg Br. 1986.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Zone V Extensor Tendon Injury

EXAMINER

"A 30-year-old woman cut the back of her hand on glass. She has a 2cm laceration over the 3rd MCP joint. She cannot extend the middle finger at the MCPJ. X-ray is normal. How do you manage this?"

EXCEPTIONAL ANSWER

This is a **Zone V Extensor Tendon Injury**. **Assessment:** - Confirm no concomitant injury (Joint capsule penetration? Fight bite context?). - Assess sensation (digital nerves) and perfusion. - Test extension: Rupture of EDC. EIP/EDQ absent for middle finger so no redundancy. - **Juncturae Tendinum:** Be aware that adjacent fingers might extend the injured finger via juncturae, masking a proximal laceration (Zone VI), but at Zone V the deficit is usually clear. **Management:** - **Explore and Repair:** - Regional block or GA. - Tourniquet. - Extend incision (Standard Z or straight). - Retrieve ends (unlikely to retract far due to juncturae). - **Repair:** 3-0 or 4-0 non-absorbable core suture (e.g., Modified Kessler) + 5-0 epitendinous suture. - **Joint Check:** Ensure capsule not breached. If so, washout and close capsule. **Rehab:** - **Dynamic Splinting** (Volar splint with outrigger) OR - **Relative Motion Splint** (Yoke splint holding middle finger extended relative to others). - Start protected active motion immediately. - Full use at 6-8 weeks.

KEY POINTS TO SCORE

Zone V injuries often involve joint capsule (Open joint)

Relative Motion Splinting is modern gold standard

Juncturae can mask proximal lacerations

Fight bite must be excluded

COMMON TRAPS

✗Missing a glass foreign body (X-ray needed)

✗Suturing the skin but missing the tendon

✗Repairing tendon but missing capsular penetration (Septic arthritis risk)

LIKELY FOLLOW-UPS

"How do you distinguish EDC from EIP?"

"What is the Elson test?"

"Describe the juncturae tendinum."

VIVA SCENARIOChallenging

Scenario 2: Bony Mallet Finger with Large Fragment

EXAMINER

"A 28-year-old basketball player presents 2 days after jamming his right ring finger. He has a flexion deformity at the DIP joint and cannot actively extend it. X-rays show an avulsion fracture involving approximately 40% of the articular surface of the distal phalanx with 2mm of volar subluxation of the distal phalanx. What is your assessment and management approach?"

EXCEPTIONAL ANSWER

This is a bony mallet finger with significant articular involvement and joint subluxation, which requires surgical management rather than simple splinting. The key decision factors are the size of the bony fragment (40% of articular surface) and the presence of volar subluxation indicating joint instability. My management algorithm is based on these criteria: if the fragment involves less than one-third of the articular surface and the joint is stable (no subluxation), splinting is appropriate; if the fragment is larger than one-third or there is joint subluxation, surgical intervention is indicated. This patient meets both surgical criteria. My surgical options are extension block pinning (Ishiguro technique) or open reduction internal fixation. For a fragment of this size with subluxation, I would recommend extension block pinning as the first-line approach. The technique involves placing the DIP joint in hyperextension which reduces the avulsed fragment, then passing a K-wire longitudinally down the middle of the distal phalanx to hold the joint in extension. The wire blocks hyperextension and prevents re-subluxation. Alternatively, if the fragment is large enough and minimally comminuted, ORIF with small screws or a tension band wire could be performed, but this is technically more demanding and risks further fragmentation. Post-operatively, I would protect the joint with a Stack splint in addition to the wire for 6 weeks, then remove the wire and continue night splinting for a further 2 weeks. I would counsel him that even with surgical fixation, some residual extensor lag (5-10 degrees) is common and functionally well-tolerated. Return to basketball would be expected at 8-10 weeks with protective taping initially.

KEY POINTS TO SCORE

Bony mallet greater than 1/3 articular surface or subluxed = surgical indication

Extension block pinning (Ishiguro) is first-line for most bony mallets

ORIF alternative if fragment large and non-comminuted

Some residual extensor lag expected even with surgery (5-10°)

Return to sport 8-10 weeks with protection

COMMON TRAPS

✗Attempting splinting for large fragment with subluxation

✗ORIF on small comminuted fragments (will fragment further)

✗Not warning about residual extensor lag

✗Removing wire too early (before 6 weeks healing)

LIKELY FOLLOW-UPS

"Describe the extension block pinning (Ishiguro) technique"

"What percentage of articular surface is the threshold for surgery?"

"What is the risk of DIP arthritis with bony mallet?"

VIVA SCENARIOCritical

Scenario 3: Chronic Boutonnière Deformity

EXAMINER

"A 45-year-old presents with a longstanding deformity of his left index finger that occurred after a basketball injury 18 months ago. He was told it was just a 'jammed finger' and it was not treated initially. Examination shows fixed PIP joint flexion contracture of 40 degrees and DIP joint hyperextension of 30 degrees. He cannot actively extend the PIP joint beyond 40 degrees of flexion and passive correction is limited to 20 degrees. X-rays show no arthritis. He requests treatment as the deformity affects his hand function and appearance. What would you discuss?"

EXCEPTIONAL ANSWER

This is a chronic established boutonnière deformity from an untreated central slip rupture 18 months ago. The initial injury likely disrupted the central slip at Zone III (PIP joint), and without proper splinting, the lateral bands migrated volarly and contracted, causing the characteristic PIP flexion and DIP hyperextension deformity. The fact that he has fixed contracture (passive PIP extension only to 20 degrees) and established deformity for 18 months makes this a complex surgical problem with guarded outcomes. My management approach would be stepwise. First, I would assess whether he has any functional deficit - some patients with boutonnière can adapt and function well. If he has significant functional impairment, I would initially attempt conservative measures with aggressive hand therapy focusing on passive PIP extension stretching exercises and DIP flexion exercises to try to improve the contracture over 3 months. If this fails to improve his range and function, surgical options include lateral band mobilization and central slip reconstruction. The surgery involves a dorsal approach to the PIP joint, releasing the contracted lateral bands from their volar position, mobilizing them back dorsally, and reconstructing or shortening the central slip using either direct repair (if tissue available) or tendon graft. This may also require terminal tendon lengthening at the DIP to correct the hyperextension. However, I must counsel him that chronic boutonnière is one of the most difficult tendon problems to treat surgically, with success rates around 50-60% for significant improvement. He may not regain full PIP extension, residual stiffness is common, and there is a risk of swan neck deformity developing if we overcorrect. In severe fixed contractures, salvage options include PIP fusion or arthroplasty if arthritis develops. Given the difficulty and uncertain outcomes, some patients elect to accept the deformity if functionally tolerable.

KEY POINTS TO SCORE

Chronic boutonnière from missed central slip injury very difficult to treat

Fixed contracture indicates lateral band contracture and volar migration

Conservative: 3 months aggressive hand therapy before considering surgery

Surgery: Lateral band mobilization + central slip reconstruction/shortening

Success rates only 50-60%, residual stiffness common, may develop swan neck

COMMON TRAPS

✗Overpromising surgical outcomes for chronic boutonnière

✗Not attempting conservative therapy first

✗Overcorrecting PIP extension causing swan neck deformity

✗Not counseling about PIP fusion as salvage option

LIKELY FOLLOW-UPS

"What is the pathomechanism of boutonnière deformity development?"

"Why does DIP hyperextension occur with PIP flexion in boutonnière?"

"What is the Fowler central slip tenotomy and when is it used?"

MCQ Practice Points

Exam Pearl

Q: What are the extensor tendon zones and why are they important?

A: 8 zones (odd numbers over joints, even over bones): Zone 1 (DIP), Zone 2 (middle phalanx), Zone 3 (PIP), Zone 4 (proximal phalanx), Zone 5 (MCP), Zone 6 (metacarpals), Zone 7 (wrist), Zone 8 (forearm). Importance: Treatment varies by zone - Zone 1-2 often splinted, Zone 3+ usually repaired. Zones over joints have thinner tendons and less surrounding tissue, making repair more challenging and prone to adhesions.

Exam Pearl

Q: What is a mallet finger and how is it treated?

A: Mallet finger: Zone 1 injury with disruption of terminal extensor tendon, causing DIP flexion deformity (15-45°). Types: Tendinous (closed injury, forced flexion); Bony (avulsion fracture of distal phalanx dorsum). Treatment: Closed/small bony mallet: Splinting in DIP extension (Stack splint) for 6-8 weeks continuous, followed by 4 weeks night splinting. Bony mallet with greater than 30% articular surface or subluxation: Consider K-wire or ORIF.

Exam Pearl

Q: What is a boutonniere deformity and what causes it?

A: Boutonniere deformity: PIP flexion + DIP hyperextension, caused by Zone 3 injury (central slip disruption). Mechanism: Central slip disruption causes lateral bands to migrate volar to PIP axis, becoming flexors at PIP and increasing extension at DIP. Acute treatment: Splint PIP in extension (DIP free) for 6 weeks. Chronic boutonniere: Surgical reconstruction (lateral band mobilization, extensor tenolysis, central slip reconstruction) with variable results.

Exam Pearl

Q: What is the Elson test and what does it assess?

A: Elson test assesses central slip integrity (Zone 3). Technique: PIP flexed 90° over table edge, patient attempts to extend against resistance. Positive test: Weak PIP extension with rigid DIP (due to lateral bands substituting via intact lateral bands). Negative test: Strong PIP extension with floppy DIP. A positive Elson test in acute injury indicates central slip rupture requiring splinting to prevent boutonniere deformity.

Exam Pearl

Q: What is a sagittal band rupture and how does it present?

A: Sagittal band stabilizes extensor tendon over MCP joint (Zone 5). Rupture causes extensor subluxation (tendon subluxates ulnarly, usually over middle finger). Presentation: Painful snapping over MCP with finger extension; May be unable to initiate extension from flexed position. Causes: Trauma (punch), inflammatory arthritis. Treatment: Acute (less than 3 weeks) - splinting MCP in extension; Chronic - surgical repair/reconstruction of sagittal band.

Australian Context

Epidemiology

Hand Injury Patterns in Australia:

Extensor tendon injuries common in industrial, agricultural, and recreational settings
Mallet finger most frequent sports-related tendon injury (cricket, football, basketball)
Glass lacerations common mechanism for zone V-VII injuries
Occupational injuries in construction and manufacturing significant
Higher incidence in rural areas with agricultural machinery exposure

Healthcare System and Referral

Emergency Department Management:

Initial wound assessment and imaging in ED
Primary repair of simple lacerations by trained ED physicians in some centres
Complex injuries referred to hand surgery services
Regional and rural patients may require transfer for specialist care

Hand Surgery Services:

Major metropolitan centres have dedicated hand surgery units
Plastic and orthopaedic surgeons both manage extensor injuries
Private and public sector access variable
Extended wait times for public non-urgent cases

Clinical Guidelines

Australian Therapeutic Guidelines:

Prophylactic antibiotics for contaminated wounds
Tetanus prophylaxis as per immunisation schedule
First-line analgesia: Paracetamol + NSAIDs

Hand Therapy Standards:

Australian Hand Therapy Association (AHTA) guidelines
Early protected motion protocols (relative motion splinting)
Custom thermoplast splinting by certified hand therapists
Stack splints for mallet finger management

PBS Listings

Relevant Medications:

Paracetamol: PBS unrestricted
NSAIDs (meloxicam, ibuprofen): PBS unrestricted
Prophylactic antibiotics (flucloxacillin, cephalexin): PBS unrestricted
Opioids for acute pain: PBS restricted

Rehabilitation

Hand Therapy Services:

Hand therapists (OT or physiotherapist with hand certification)
Available in major centres, limited in regional areas
Private and public hospital outpatient services
Custom splinting and exercise programs
Work capacity assessments

Expected Recovery:

Mallet finger: 8-12 weeks continuous splinting, then progressive use
Zone V-VII repairs: 6-8 weeks to return to light duties
Full grip strength: 3-6 months post-repair
Manual work return: 2-3 months post-repair

Occupational Considerations

WorkSafe/SafeWork:

Workplace injuries eligible for workers compensation
Return-to-work planning with employer liaison
Modified duties during recovery
Hand therapy as part of rehabilitation program

Management Algorithm

Extensor Tendon Quick Reference

High-Yield Exam Summary

Zones

•I: DIP (Mallet)
•III: PIP (Central Slip/Boutonnière)
•V: MCP (Sagittal Band)
•Odd = Joints

Tests

•Elson's Test: For Zone III (Central slip)
•Bouvier Test: For Ulnar Claw (Intrinsics)

Treatments

•Mallet: Splint DIP only 6-8w
•Boutonnière: Splint PIP extension 6w (Active DIP flexion)
•Open V/VI: Repair + Early Motion

Extensor Tendon Injuries

High Yield Overview