High Yield Overview
FLEXOR TENDON REPAIR
Suture Techniques and Biomechanics
4Min Strands
20%Epitendinous Strength
2mmMax Gap
Zone 2No Man's Land
Verdan Zones
Zone I
PatternDistal to FDS insertion (FDP only).
Treatment
Zone II
PatternA1 Pulley to FDS insertion. (FDS + FDP in sheath).
Treatment
Zone III
PatternPalm (Lumbrical origin).
Treatment
Zone IV
PatternCarpal Tunnel.
Treatment
Zone V
PatternForearm.
Treatment
Critical Must-Knows
- A 4-strand core suture is the absolute minimum for Early Active Motion.
- The Epitendinous suture adds 10-20% strength and reduces gapping.
- Gapping greater than 3mm leads to poor outcomes (adhesions/rupture).
- Preserve A2 and A4 pulleys to prevent bowstringing.
- Repair should be performed within 7-10 days (before myostatic contracture).
- WALANT (Wide Awake) allows intra-operative testing of glide.
Examiner's Pearls
- "Strength is proportional to the number of strands crossing the repair site.
- "Locking loops prevent suture pull-out but can strangle the tendon (ischemia).
- "The placement of the knot (inside or outside) is debated; mostly inside to reduce friction.
Clinical Imaging
Suture Technique Comparison
Click to expand
The Gap Formation
The Problem
Gap greater than 2mm Gap formation at the repair site allows fibrous tissue ingrowth (adhesions) rather than tendon healing. A gap weakens the repair significantly and predisposes to rupture.
The Solution
Pre-tensioning & Epitendinous Pre-tensioning the core suture ensures faces are opposed. The epitendinous running suture is CRITICAL for resisting gap formation. It smooths the edges and adds strength.
| Feature | Modified Kessler | Adelaide | Cruciate |
|---|---|---|---|
| Config | Locking Rectangular | Cross-Locking (4 strand) | Cross-Stitch |
| Strands | 2 (Standard) | 4 (Standard) | 4 (Standard) |
| Strength | Moderate | High | High |
| Bulk | Low | Moderate | Low |
Mnemonic
SCENERepair Strength Factors
S
Strands
Number of core strands (most important).
C
Core
Suture caliber (3-0 or 4-0).
E
Epitendinous
Adds strength and glide.
N
Nodes
Locking loops grasp the fibers.
E
Expeditious
Early repair (less than 10 days).
Memory Hook:Create a SCENE for strong repair.
Mnemonic
DAP-CT-FVerdan Zones
D
Distal
Zone I (Distal to FDS).
A
A1 to FDS
Zone II (No Man's Land).
P
Palm
Zone III.
CT
Carpal Tunnel
Zone IV.
F
Forearm
Zone V.
Memory Hook:Distal to Proximal mapping.
Mnemonic
GLIDERehabilitation Goals
G
Gentle
Passive flexion.
L
Load
Controlled active extension.
I
Inflammation
Control edema.
D
Differential
FDS vs FDP glide.
E
Edema
Coban/Elevation.
Memory Hook:The goal is GLIDE.
Overview
Definition
Flexor tendon repair aims to restore digital flexion while minimizing adhesion formation. The challenge is balancing Mechanical Strength (to allow early motion) against Gliding Resistance (bulkiness of the repair).
The history of flexor tendon repair has evolved from "primary repair is impossible" (Bunnell's 'No Man's Land') to the current standard of primary repair with robust constructs allowing Early Active Motion (EAM).
Key historical milestones include:
- Bunnell: Advocated tendon grafting in Zone II.
- Kleinert: Introduced immediate controlled active motion with rubber bands.
- Strickland: Defined the biomechanical requirements for EAM (Work of Flexion vs Repair Strength).
Pathophysiology and Mechanisms
Verdan Zones
- Zone I: FDP only. Distal to FDS insertion. Repair is straightforward (or advancement).
- Zone II: FDS and FDP share the sheath (A1 to FDS insertion). Most complex. Adhesion risk is highest here.
- Zone III: Lumbrical origin. Good prognosis.
- Zone IV: Carpal Tunnel. Crowded.
- Zone V: Forearm. Good prognosis.
The transition from Zone II to Zone III is defined by the distal palmar crease.
Classification Systems
Repair Configurations
- Modified Kessler: Rectangular locking. 2 strands per pass.
- Adelaide: 4 strands. Locking. Developed for EAM.
- Cruciate: Cross pattern. 4 strands.
- Tajima: Locking loops for grasping the end.
- Lim/Tsai: 6-strand loops.
The mechanical strength of the repair is linearly related to the number of strands.
History
History Taking
- Mechanism: Sharp (knife, glass) vs Crush (machinery).
- Time: Hours since injury. Ideal repair within 24-72 hours.
- Contamination: Animal bite, soil, marine environment.
- Occupation: Manual worker, musician, typist.
- Hand Dominance: Right or left handed.
- Smoking: Major risk factor for complications.
- Diabetes: Impaired healing.
- Previous Hand Surgery: Scarring, previous tendon injury.
Sharp, clean lacerations have best prognosis.
Examination
Pre-operative Examination
- FDS Test: Hold other fingers in extension. Ask patient to flex PIPJ.
- FDP Test: Hold PIPJ in extension. Ask patient to flex DIPJ.
- Index Quirk: Some patients have independent FDP to index (absent FDS).
- Neuro: Digital nerves are lateral to tendons and often cut concomitantly.
- Perfusion: Digital arteries. Check cap refill, Allen's test.
- Wound: Assess depth, contamination, tissue loss.
Ensure you test FDS function for each digit individually.
Investigations
Ultrasound
- Can locate retracted tendon ends.
- Confirm diagnosis in partial tears.
- X-Ray: Rule out avulsion fracture (Jersey finger) or foreign body.
MRI is rarely needed for acute lacerations but useful for chronic ruptures. It can visualize:
- Tendon stump location (retraction).
- Integrity of the pulley system.
- Presence of scar tissue/adhesions.
This helps in planning tenolysis or staged reconstruction.
Treatment
📊 Management Algorithm
Click to expand
Primary Repair
- Gold Standard: Repair within 24-72 hours ideally.
- Limit: Up to 10-14 days. After this, pulleys collapse and muscle contracts.
- Delayed: If greater than 3 weeks, may need 2-stage reconstruction (Hunter Rod).
Immediate repair is always technically easier than delayed repair.
Surgical Considerations
Exposure (Bruner)
- Incisions: Zig-zag (Bruner) incisions prevent scar contracture.
- Flaps: Full thickness flaps raised.
- Sheath: Window the sheath between pulleys (e.g. C1 window) to access the tendon. Do not vertically slice A2/A4 if possible.
Good exposure is key. Extend incisions proximally and distally.
Antibiotic Protocol
Antibiotics
Prophylaxis:
- Cefazolin (Kefzol) 2g IV at induction.
- Post-op oral antibiotics (Cephalexin) often given for 5 days due to length of procedure and implant material, though evidence is debated.
- Contaminated Wounds: Augmentin.
Complications
- Adhesions: Most common complication. Loss of active flexion despite good passive ROM. Needs Tenolysis.
- Rupture: Catastrophic failure. Occurs if rehab is too aggressive or repair is weak (less than 4 strands).
- Bowstringing: Loss of A2/A4 pulleys results in an increased moment arm but loss of excursion (finger curls but doesn't fully flex).
- Contracture: PIPJ flexion contracture is common if not splinted in extension.
- Quadriga Effect: Overtightening FDP in one finger tethers the others (common muscle belly). The patient cannot make a full fist because the repaired finger hits the palm first.
- Infection: Deep space infection is disastrous for tendon gliding.
Rehabilitation
Week 0-4
- Splint: Dorsal Blocking Splint (Wrist 30° flex, MCP 70° flex, IP extended).
- Passive Flexion: Duran protocol - passive flexion exercises within splint.
- Active Extension: Controlled active extension to splint limits.
- Synergistic Motion: Wrist extension with finger flexion (Tenodesis effect).
- Early Active: Gentle active flexion to 1/3 fist if 4-strand repair (Manchester/Stark).
- Edema Control: Coban wrap, elevation, retrograde massage.
Week 4-6
- Wrist Neutral: Progress wrist position to neutral.
- Place and Hold: Active extension, passive flexion, then hold.
- Tendon Gliding: Hook, Straight, Fist, Table-top positions.
- Differential Glide: Isolated FDS vs FDP exercises.
- Scar Management: Silicone gel sheets, massage.
Week 6-8
- Splint Wean: Day use only, night splint continues.
- Full Active Motion: Unrestricted active ROM exercises.
- Blocking Exercises: Isolated joint motion (DIP blocking for FDP).
- Light Functional Use: ADLs with precautions.
Week 8-12
- Splint Discontinue: Week 8.
- Progressive Resistance: Putty, hand exercisers.
- Work Hardening: Task-specific conditioning.
- Return to Work: Light duties Week 8, full duties Week 12.
- Sport: Full contact sports at Week 12.
Prognosis
- Zone I/III/V: Excellent results.
- Zone II: "Fair" to "Good". Stiffness and adhesions remain a challenge. 10-15% rupture rate depending on compliance.
- Tenolysis: Required in 15-20% of Zone II repairs.
- Children: Excellent healing potential but poor compliance with rehab creates high risk of rupture or adhesion. Cast immobilization is often used.
- Smokers: Higher rates of complications (infection, poor healing).
Evidence Base
Strickland's Evaluation
Strickland JW. • J Am Acad Orthop Surg (1995)
Key Findings:
- Review of biomechanics
- 2-strand repair = 2000g strength (insufficient for early active)
- 4-strand repair = 4000g+ strength (sufficient)
- Established the standard for 4-strand core sutures
Clinical Implication: You must use at least 4 strands.
Epitendinous Suture
Dona et al. • J Hand Surg (1991)
Key Findings:
- Biomechanical study
- Epitendinous suture increases gap resistance and ultimate tensile strength by 20-50%
- Reduces work of flexion
Clinical Implication: Always use an epitendinous running suture.
WALANT
Lalonde D. • J Hand Surg Am (2009)
Key Findings:
- Wide Awake Local Anesthesia No Tourniquet
- Allows intra-operative active movement to test gap and glide
- Reduces rupture and tenolysis rates
Clinical Implication: See the repair work before closing.
Early Active Motion
Small et al. • J Bone Joint Surg Br (1989)
Key Findings:
- Comparison of immobilization, passive, and active motion
- Early active motion resulted in superior ROM and tendon healing
- Requires strong repair
Clinical Implication: Move it or lose it (adhere it).
Venting Pulleys
Tang JB. • J Hand Surg Am (2010)
Key Findings:
- Partial release of A2/A4 pulleys (venting) improves gliding of bulky repairs
- Does not significantly affect bowstringing if limited length
- Crucial for Zone II repairs
Clinical Implication: Don't be afraid to vent stiff pulleys.
Viva Scenarios
Practice these scenarios to excel in your viva examination
VIVA SCENARIOStandard
Scenario 1: The Zone II Cut
EXAMINER
"A 25-year-old carpenter presents with a laceration over Zone II of the index finger. FDS and FDP are non-functional. He wants a quick return to work. Discussion?"
EXCEPTIONAL ANSWER
This is a Zone II injury requiring exploration and repair. I would counsel him that 'quick' is not possible. He faces 3 months of rehab. I would perform a 4-strand core repair (e.g. Adelaide) with epitendinous suture, aiming for Early Active Motion. I would assess digital nerves. If he cannot commit to the rehab, stiffness or rupture is guaranteed.
KEY POINTS TO SCORE
Zone II complexity
Rehabilitation compliance is key
Minimum 4-strand repair
COMMON TRAPS
✗Promising full function
✗Using a weak 2-strand repair
LIKELY FOLLOW-UPS
"He asks why not just fuse it?"
"Arthrodesis is a salvage option. Primary repair gives the best chance of function. If it fails, he can have a fusion later. Don't burn bridges."
VIVA SCENARIOStandard
Scenario 2: The Rupture
EXAMINER
"6 weeks post-op Zone II repair, a patient feels a 'pop' lifting a coffee cup. Finger is extended, no active flexion. What now?"
EXCEPTIONAL ANSWER
This is a rupture. Options are limited. Re-repair is rarely successful due to fraying and retraction. Options include: 1. Reconstruction (2-stage Hunter Rod). 2. Tendon Graft (if sheath intact). 3. Fusion of DIPJ (if FDP only). 4. Ignore (if FDS intact). Given it's Zone II (both), he likely has no flexion. I would offer 2-stage reconstruction or fusion depending on his needs.
KEY POINTS TO SCORE
Poor prognosis of re-repair
Need for reconstruction (Graft/Rod)
Salvage options
COMMON TRAPS
✗Attempting direct primary re-repair in a scarred bed
LIKELY FOLLOW-UPS
"What is a Hunter Rod?"
"A silicone rod placed in the sheath to form a pseudosheath over 3 months, followed by tendon grafting."
VIVA SCENARIOStandard
Scenario 3: The Stiff Finger
EXAMINER
"4 months post-op. Full passive flexion, but no active flexion. What is the diagnosis and management?"
EXCEPTIONAL ANSWER
This is an adhesion. The tendon is healed but stuck to the sheath. Confirmed by the discrepancy between active and passive ROM. Management: 1. Aggressive therapy (Work hardening). 2. Tenolysis surgical release. I would wait until soft tissues are soft (usually 6 months) before offering tenolysis.
KEY POINTS TO SCORE
Adhesion diagnosis (Passive > Active)
Timing of Tenolysis (Soft tissues must be mature)
Surgical release
COMMON TRAPS
✗Operating too early (causes more scarring)
LIKELY FOLLOW-UPS
"What happens after tenolysis?"
"Need immediate moving. Indwelling catheter for pain control. Full active motion immediately."
VIVA SCENARIOStandard
Scenario 4: The Thumb Laceration
EXAMINER
"A 35-year-old presents with a glass laceration at the thenar crease. FPL is non-functional. Describe the anatomy and management."
EXCEPTIONAL ANSWER
This is a Zone T3 (thenar eminence) FPL injury. Anatomy: FPL is the only flexor to the thumb IP joint. The A1 pulley is at the MCP level, oblique pulley over the proximal phalanx is critical. The tendon may retract into the forearm (single muscle belly). I would explore through a Bruner incision, retrieve the tendon (may need carpal tunnel extension), and perform a 4-strand repair. WALANT allows active testing. Thumb rehabilitation is challenging as patients use it constantly.
KEY POINTS TO SCORE
Zone T3 anatomy
Oblique pulley preservation
Tendon may retract proximally
WALANT for intraoperative testing
COMMON TRAPS
✗Missing the proximal retraction
✗Forgetting to test EPL at same time
✗Underestimating thumb functional demands
LIKELY FOLLOW-UPS
"What if the oblique pulley is destroyed?"
"Oblique pulley is critical for thumb flexion. May need reconstruction with tendon graft or consider the A1 pulley as substitute."
MCQ Practice Points
Biomechanics
Q: How much strength does a standard epitendinous suture add to a repair? A: 10-20%.
Anatomy
Q: Which nutrient pathway is most important in Zone II? A: Synovial diffusion (Imbibition).
Complications
Q: What is the Quadriga Effect? A: Limitation of flexion in adjacent fingers due to overtightening/shortening of the FDP in the repaired finger (shared muscle belly).
Technique
Q: What is the minimum strand count for Early Active Motion? A: 4 Strands.
Zone II
Q: Why is Zone II called 'No Man's Land'? A: FDP and FDS travel within a tight fibro-osseous tunnel, making repair technically challenging and historically associated with poor outcomes due to adhesion formation.
Pulley Preservation
Q: Which pulleys are critical and must be preserved during flexor tendon surgery? A: A2 and A4 - They prevent bowstringing. A1, A3, and A5 can be released if needed for exposure.
Australian Context
Australian Injury Patterns
- Workplace: Construction, manufacturing, meat processing industries have highest rates.
- Compensation: Hand/wrist injuries represent significant proportion of workers' compensation claims.
- Demographics: Peak incidence in working-age males (20-40 years).
- Mechanism: Glass and knife lacerations are most common causes.
Understanding local injury patterns helps guide prevention strategies and resource allocation.
High-Yield Exam Summary
Technique
- •4-Strand Core (Min)
- •Epitendinous Running
- •Vent Pulleys if tight
- •Preserve A2/A4
Rehab
- •Dorsal Block Splint
- •Early Active Motion
- •Passive Flexion (Duran)
- •Place and Hold
Complications
- •Rupture (Worst)
- •Adhesion (Common)
- •Bowstringing (Pulley loss)
- •Quadriga (Length mismatch)