Zone-dependent exposure and a strong multi-strand core plus early protected motion decide the result. Zone 2 — 'no man's land' — is the test of technique.
- A complete flexor tendon laceration needing primary repair. Zone-specific: Zone 1 (FDP only), Zone 2 (FDP and FDS — 'no man's land' — with the critical A2 and A4 pulleys), Zone 3 (palm), Zone 4 (carpal tunnel), Zone 5 (forearm).
- Timing decides what is possible: primary repair is ideal under 12 hours and acceptable to 24 hours if the wound is clean; a contaminated wound needs a delayed or staged approach; a chronic injury over 3 weeks cannot be repaired primarily (retraction and scarring) and needs a graft or two-stage reconstruction.
- A2 (over the proximal phalanx, 17–20 mm) and A4 (over the middle phalanx, 7–10 mm) are the critical pulleys — preserve more than 50% of each, or bowstringing with 30–40% power loss results. A1, A3, A5 and all the cruciate pulleys can be divided.
- Each core strand adds about 1 kg of tensile strength. The modern minimum is a 4-strand core (about 4 kg); 6 to 8 strands are best for early active motion. The old 2-strand repair (about 2 kg) is inadequate and ruptures in 10–30% with early motion.
- Add an epitendinous suture (5-0/6-0 monofilament, running locked around the full circumference) — it adds 10–50% strength and was the single factor most strongly associated with avoiding re-operation in the Dy meta-analysis.
- Early protected motion in a dorsal blocking splint (wrist 20–30° flexion, MCP 60–70° flexion, IP extended) prevents adhesions — the most common complication. No passive IP extension for 6 weeks — it ruptures the repair.
When & Why
Indication. A complete laceration of a flexor tendon (FDP and/or FDS) requiring primary repair or reconstruction. The presentation is a sharp volar hand or finger laceration with loss of active flexion distal to the cut, and the surgical plan is set almost entirely by the zone of injury and the time since injury. Assess the injury precisely before theatre. Document the laceration details — location (zone), depth (complete versus partial), structures injured, wound contamination (clean versus contaminated), time since injury, and associated injuries (nerve, artery, bone or joint, skin loss). - Test each tendon individually. FDP: stabilise the PIP in extension and ask the patient to flex the DIP. FDS: block the adjacent fingers in extension (which eliminates FDP through the quadriga effect) and ask the patient to flex the PIP. Testing only one tendon is a common error that misses the other injury.
- Neurovascular status. Check two-point discrimination (less than 6 mm is normal; greater than 15 mm suggests a nerve injury), capillary refill and a digital Allen test.
- Imaging. An X-ray to exclude a fracture or a retained foreign body (glass). Timing — the decision that governs everything else:
Clean wound, ideally under 12 hours and acceptable up to 24 hours. Direct tendon-to-tendon repair with a strong multi-strand core plus an epitendinous suture and early protected motion.
Contaminated wound. Clean and debride first, then return to theatre at 3 to 7 days for the repair once the soft tissues are clean.
Chronic injury over 3 weeks — too much retraction and scarring for primary repair. Options are staged reconstruction (a Hunter silicone rod to form a pseudosheath, then a tendon graft at about 3 months) or a single-stage graft if the bed is suitable.
Consent specifically for digital numbness or a painful neuroma, stiffness and adhesions (the most common problem), repair rupture needing re-operation, bowstringing if a critical pulley is lost, and the absolute need for compliance with the hand-therapy protocol — non-compliance in either direction (too much activity, or too little motion) ruins the result. Setup. Supine with the arm on a hand table, shoulder abducted 90 degrees. Loupe magnification (2.5–3.5x) is mandatory for all zones and essential for Zone 1 to 2, with a microscope for very distal repairs. Have fine instruments (Adson and Bishop-Harmon forceps, tenotomy scissors, nerve hooks, mosquito clamps, a tendon passer), tendon-retrieval tools (an 8 Fr feeding tube or silicone catheter) and the right suture ready — 3-0 or 4-0 braided non-absorbable for the core (FiberWire, Ethibond, braided nylon) and 5-0 or 6-0 monofilament for the epitendinous (Prolene or nylon). A Zone 2 repair needs an experienced hand surgeon, a modern multi-strand technique and an early-motion protocol.
The Operation
The goal: expose the tendons through a zone-appropriate incision, protect the neurovascular bundles and the critical A2 and A4 pulleys, retrieve the retracted stumps without trauma, and build a strong, smooth, multi-strand repair that glides — then protect it with a dorsal blocking splint and early motion. The exposure (position, the zone-specific incision, the neurovascular protection and the pulley-sparing sheath opening) is laid out in full as the first steps, because access is the foundation of a good repair. The Bruner zigzag approach to the digit is described in depth on the Bruner volar zigzag approach page.
Operative sequence
- Supine, arm on a hand table, shoulder abducted 90 degrees, elbow extended. Surgeon and assistant seated comfortably; consider an arm holder for a long case.
- Anaesthesia by complexity: general anaesthesia for complex Zone 2 repairs, children, anxious patients and long cases (it gives muscle relaxation that aids tendon retrieval); regional block (axillary or supraclavicular, or a Bier block/IVRA) for the hand and forearm; WALANT (lidocaine 1% with 1:100,000 epinephrine) for simple Zone 1, 3 or 5 repairs in a cooperative patient — the advantage is that the repair can be tested actively intra-operatively, though retrieval is harder without muscle paralysis.
- Exsanguinate by elevation, or Esmarch — but avoid Esmarch when retraction is a concern, because compression can push the stump proximally and make retrieval harder.
- Arm tourniquet at 250 mmHg (about 100 mmHg above systolic), or 300 mmHg for a large arm, well padded. Plan tourniquet time under 90 to 120 minutes where possible — complex Zone 2 repairs may need longer, so warn the patient, pad well, and consider release and reinflation beyond 120 minutes to avoid compartment syndrome and tourniquet pain.
- Magnification: loupes 2.5–3.5x for all zones (essential for Zone 1 to 2); a microscope at 10–16x for very distal repairs or a microsurgical technique.
- Zone 1: a midlateral or volar Bruner incision on the radial side of the digit, extending from the laceration proximally to the DIP joint and distally toward the fingertip. Avoid a direct volar incision over the DIP — poor padding and a painful scar.
- Zone 2 (no man's land): the Bruner zigzag is the gold standard. Place the apices at the flexion creases (PIP, DIP, distal palmar crease) with angles of about 60 degrees — never 90 degrees, which risks a flexion-contracture scar. Extend proximal and distal to the laceration to expose the pulleys and allow tendon retrieval, and incorporate the traumatic laceration into the design. A radial midlateral incision is an alternative for a limited laceration (less exposure).
- Zone 3: a longitudinal or gently curved palmar incision following the skin creases — a transverse palmar incision crosses too many neurovascular bundles. Extend from the carpal tunnel area to the base of the affected digit.
- Zone 4: a standard carpal tunnel release incision — longitudinal or slightly oblique over the carpal tunnel in line with the ring-finger axis (Kanavel's line) — extended distally into the palm if needed.
- Zone 5: a longitudinal volar forearm incision along the flexor compartment, starting 3 to 4 cm distal to the elbow flexion crease and running to the wrist, kept slightly ulnar to midline to avoid the superficial median nerve branch; it can extend distally into the carpal tunnel.
- Principles: never cross a flexion crease at 90 degrees, use Bruner angles of about 60 degrees, extend generously for exposure (do not compromise access to save 1 cm), and incorporate the existing laceration into the design.
- Sharp skin incision with a 15-blade, then careful dissection to the deep structures. Raise full-thickness skin flaps (skin plus subcutaneous fat) — avoid thin flaps (vascular compromise, necrosis) and avoid undermining (haematoma).
- Identify the neurovascular bundles immediately: the proper digital nerves and arteries run palmar-laterally, about 2 to 3 mm from the midline, the nerves pink-white with accompanying arteries. Use a spreading technique parallel to the bundles with fine scissors or a mosquito clamp rather than cutting.
- Divide Grayson's ligaments (palmar to the bundles, tethering skin to sheath) carefully to mobilise the flaps; Cleland's ligaments (dorsal to the bundles) are generally safe.
- Zone-specific structures at risk: in the palm (Zone 3) protect the common digital nerves, superficial palmar arch branches and lumbricals; in the carpal tunnel (Zone 4) the median nerve is central and superficial — identify and protect it before any tendon work, and divide the transverse carpal ligament on its ulnar side if access is needed; in the forearm (Zone 5) map the median nerve, ulnar nerve and radial artery before proceeding.
- Retract gently with self-retaining retractors (Weitlaner, Gelpi) or skin hooks — excessive traction causes nerve injury.
- Identify the pulley system before opening the sheath: A1 (MCP joint), A2 (proximal phalanx — the longest and critical), C1 (PIP level), A3 (PIP joint), C2, A4 (middle phalanx — critical), C3, A5 (DIP).
- Open the sheath in windows between pulleys. You can safely divide A1 (for proximal access), A3 over the PIP, and all the cruciate pulleys (C1, C2, C3); create windows between A2 and C1, C1 and A3, A3 and C2, and C2 and A4.
- Preserve A2 and A4. If more exposure is essential you may release up to 50% of one (radial or ulnar side, keeping at least half intact); if you release more than 25% of A2 or A4 you must repair it later (Step 11).
- Modern evidence (Tang and Lalonde): controlled venting of a short segment of a critical pulley — keep the total vented sheath under 2 cm, ideally venting A4 or the distal A2 rather than the whole A2 — is safe, does not cause bowstringing when the rest of the sheath is intact, and improves gliding for early active motion. Vent just enough for the repair to pass without catching.
- Extend the sheath opening proximally into the palm (Zone 3) or carpal tunnel (Zone 4) as needed to retrieve a retracted stump. Zones 3, 4 and 5 have no flexor sheath — direct access after superficial dissection.
- Distal stumps are usually visible at the laceration site or just distal; gentle traction with fine forceps or a mosquito clamp delivers them into the wound.
- Proximal stumps often retract significantly, especially FDP, which retracts more than FDS because of its deeper position and lumbrical pull. Retrieval options: (1) milking — an assistant milks the forearm muscles from proximal to distal to push the stump distally; (2) the feeding tube or silicone catheter (the most common method) — pass an 8 Fr tube from distal to proximal through the sheath, identify it in the palm or forearm through a small window, suture the proximal stump to its tip, and pull it back distally delivering the stump; (3) a separate proximal window in the palm (Zone 3) or wrist and forearm (Zone 4 to 5); (4) flex the wrist and fingers to relax the tendons and reduce retraction.
- Identify the correct tendons: FDS is superficial and splits into two slips at Camper's chiasm; FDP is deep and single, inserting on the distal phalanx. Verify by traction — pulling FDP flexes the DIP, pulling FDS flexes the PIP. Freshly lacerated tendon is whitish with visible fibre bundles.
- Handle gently — excessive force shreds the tendon or avulses the musculotendinous junction. If the tendon is severely retracted from a chronic injury (over 3 weeks), primary repair is not possible: plan staged reconstruction (a Hunter silicone rod to form a pseudosheath, then a graft at about 3 months) or primary grafting if the bed is suitable.
- Trim only crushed, macerated or contaminated tissue back to healthy tendon with a sharp scalpel or fine scissors, and minimise shortening. Aim for a final gap of less than 3 mm; if trimming would create a gap greater than 10 mm, plan an intercalary graft or staged reconstruction.
- Bevel the ends at about 45 degrees (oblique) to increase the healing surface area and improve biomechanics — a transverse cut is also acceptable.
- Assess quality: healthy tendon is white and fibrous with good substance; poor-quality tendon (macerated, rheumatoid, infected) may need a graft rather than primary repair. Remove all loose fragments and frayed tissue.
- Zone-specific points: Zone 1 — if the FDP laceration is very distal (less than 1 cm from insertion), perform primary reinsertion to bone (transosseous tunnels in the distal phalanx, sutures tied over a button on the fingertip) rather than a tendon-to-tendon repair. Zone 2 — prepare both tendons; if FDS is badly damaged and bulky you may resect one slip (preserve the radial slip) to reduce bulk. Preserve intact vincula where possible — they vascularise the repair.
- Modern principle: a minimum 4-strand core suture for early motion; 6 or 8 strands are better. Each strand adds about 1 kg of tensile strength (2-strand about 2 kg, inadequate for active motion with a 10–30% rupture rate; 4-strand about 4 kg, rupture 3–10%; 6 to 8 strand about 6–8 kg, rupture under 5%).
- Suture: non-absorbable, 3-0 or 4-0, braided (FiberWire, Ethibond, braided nylon) for knot security and strength, or monofilament Prolene (less friction). Each suture locks within the tendon substance — bites 7 to 10 mm from the cut end (closer pulls out, farther grasps too much), 2 to 3 mm deep into the substance, with a locking loop.
- Achieve tendon-to-tendon apposition with a gap of less than 3 mm. Bury the knots within the tendon or at one end (not in the repair site), with 5 to 6 throws for braided and 3 to 4 for monofilament. After placing the core suture, check the gap with gentle traction — it should be less than 3 mm, and the epitendinous suture will close it further.
- Not just cosmetic: it adds 10 to 50% to repair strength, smooths the surface (less friction and fewer adhesions), and reduces gapping.
- Use 5-0 or 6-0 monofilament (Prolene or nylon — monofilament glides better than braided), placed after the core suture as a running locked suture around the full circumference (360 degrees).
- Start at the core-suture knot, catch epitenon only (the superficial layer) with small 1 to 2 mm bites, lock at the quadrants (every 90 degrees) or every 2 to 3 mm, and run right around the whole circumference, finishing near the start.
- Goals: a smooth contour (palpate — no step-off), gap reduced to less than 1 to 2 mm, and strength augmentation. Total strength is the core (4 to 8 kg depending on strands) plus the epitendinous (about 0.5 to 2 kg).
- The Zone 2 dilemma: both tendons lie in a tight sheath with the critical pulleys. FDP repair is essential — it is the only DIP flexor. FDS repair is beneficial if space allows but optional where bulk is a concern.
- Algorithm: (1) if the FDS laceration is clean and space is adequate, repair both slips with the same 4-strand plus epitendinous technique; (2) if FDS is ragged or the combined repair is too bulky, resect one slip (preserve the radial slip where possible, reducing bulk by about 30–40%) and repair FDP plus the remaining slip; (3) if the sheath is extremely tight, resect both FDS slips and repair FDP only (some PIP flexion is lost — FDP gives only about 30–40% of FDS strength — but DIP flexion is excellent and adhesion risk falls).
- Test intra-operatively: after the FDP repair, pass the construct through the A2/A4 area with passive motion — if it catches, resect FDS; if it glides, repair FDS. Modern trend: increasing acceptance of FDP-only repairs, especially with a strong 6 to 8 strand FDP core. No consensus exists; a heavy manual worker may favour FDS repair (more strength), an office worker FDS resection (better motion).
- Critically, test the repair by passive finger motion through full range before closure, observing the repair site directly throughout.
- Assess: (1) gliding — the repair should glide smoothly under A2 and A4 without catching or triggering (if it catches, slim the repair, trim a pulley edge or remove synovium); (2) gap — under 3 mm throughout flexion and extension (a gap over 5 mm means excessive tension or an inadequate repair — revise, graft or accept a reduced arc); (3) pulley interaction — watch the repair pass through A2 and A4; (4) resistance — passive motion should feel smooth (a tight point needs revision); (5) range — aim for more than 50% of normal passive ROM immediately (oedema and sutures limit the rest).
- Profundus check rule: with the finger extended the repair should lie proximal to A2 (in the palm); with full flexion it should pass through A2 into the finger. If it cannot pass A2 with flexion, the tendon is too short or A2 is too tight. Adjust now — never accept catching or resistance on the assumption that it will improve.
- If more than 25% of A2 or A4 was released for access, repair it to prevent bowstringing: 6-0 absorbable (Vicryl, PDS) or non-absorbable (Prolene, nylon) interrupted horizontal mattress sutures reapproximating the edges, aiming to restore at least 50% of pulley width.
- Do not over-tighten — it constricts gliding. Test gliding after repair — the tendon must pass smoothly. The cruciate pulleys (C1, C2, C3) do not need repair, and A1, A3 and A5 usually do not either.
- Complete A2 or A4 loss (over 50% or the whole pulley) cannot be adequately repaired acutely. Options: accept the loss (mild bowstringing may be tolerable), immediate reconstruction (advanced — a slip of FDS, extensor retinaculum or a palmaris graft weaved around the phalanx), or delayed reconstruction if symptomatic bowstringing develops. Document all pulley management in the operative note.
- After the repair, decide whether to close the flexor sheath (Zone 1 to 2). Two schools: close loosely (interrupted 6-0 absorbable, maintaining a synovial environment — but never tight, which strangulates the repair and increases adhesions), or leave it open (it reduces compartment pressure, and the sheath reconstitutes over time).
- No strong evidence favours either; there is a slight trend toward better motion with an open sheath. Never perform a tight circumferential closure. Zones 3, 4 and 5 have no sheath to close.
- Interrupted non-absorbable sutures (4-0 or 5-0 nylon or Prolene) are preferred over running (they allow selective removal if infected and purse-string less). Bruner incision: vertical mattress at the zigzag apices (eversion, prevents dog-ears) and simple interrupted on the straight segments. Midlateral or longitudinal: simple interrupted or vertical mattress. Palm and forearm: simple interrupted, with a 4-0 absorbable subcutaneous layer to reduce tension.
- No tension, good apposition, slight eversion. Avoid buried sutures near the repair (adhesion risk if they migrate). A subcuticular absorbable (5-0 Monocryl) gives better cosmesis but needs perfect haemostasis.
- Release the tourniquet before final skin closure, wait 2 to 3 minutes, and cauterise any bleeding vessel — this prevents a post-operative haematoma that causes adhesions and infection. WALANT is already haemostatic.
- Apply a dorsal blocking splint before leaving theatre: wrist 20 to 30 degrees flexion, MCP 60 to 70 degrees flexion, IP joints in full extension or 10 to 20 degrees flexion. This position maximally relaxes the flexor tendons and protects the repair from tension.
- The full rehabilitation protocol (early protected motion, progression, restrictions) is detailed in Aftercare.
- Strands
- 2
- Approx. strength
- ~2 kg
- Role
- Historical only — inadequate for early motion
- Strands
- 4
- Approx. strength
- ~4 kg
- Role
- Modern minimum standard
- Strands
- 4
- Approx. strength
- ~4 kg
- Role
- Excellent 4-strand option
- Strands
- 6
- Approx. strength
- ~6 kg
- Role
- Allows more aggressive early motion
- Strands
- 8
- Approx. strength
- ~8 kg
- Role
- Strongest — for early active motion
The proper digital nerves and arteries run palmar-laterally only 2 to 3 mm from the midline and are the structures most often injured; in the carpal tunnel (Zone 4) the median nerve is central and superficial. Identify and protect them with a spreading technique and loupe magnification before any deep dissection or tendon work — a digital nerve injury is the most common complication, and a median nerve injury in Zone 4 is a major complication (thenar weakness, sensory loss) needing microsurgical repair. Avoid excessive retraction, which causes a traction neurapraxia that may be permanent.
Loss of more than 50% of A2 or A4 causes bowstringing (the tendon lifts off the bone axis), with a 30 to 40% loss of grip power, PIP hyperextension and a reduced motion arc — it then needs pulley reconstruction. Open the sheath in windows between pulleys, dividing A1, A3 and the cruciates freely; preserve A2 and A4, and if you must release more than 25% of either, repair it before closing. Never divide pulleys indiscriminately.
With the finger extended the repair site should lie proximal to A2 (in the palm); with full flexion it should pass through A2 into the finger. If the repair cannot pass A2 with flexion, the tendon is too short or A2 is too tight — fix it now, before closing. It is far harder to revise after closure.
When the repair catches, controlled venting of a short segment of A4 or the distal A2 — keeping the total vented sheath under 2 cm — is safe, does not cause bowstringing when the remainder of the sheath is intact, and improves gliding for early active motion. Vent just enough for the repair to pass without catching.
Release the tourniquet, wait 2 to 3 minutes and cauterise any bleeding vessel before completing skin closure. Missing this step leaves bleeding vessels that fill the wound with a post-operative haematoma once tourniquet pressure is released — driving adhesions and infection.
Palmar-lateral, 2 to 3 mm from the midline at each digit level. Raise full-thickness flaps, identify the nerves before deep dissection, use a spreading technique parallel to the nerve, and use loupe magnification.
Alongside the proper digital nerves, palmar-laterally. Same protection as the nerves — spreading technique and gentle retraction; cauterise only bleeding branches, not the main vessels.
Over the proximal phalanx, 17 to 20 mm long — the most critical pulley. Preserve more than 50% (loss causes 30 to 40% power loss and bowstringing). Open the sheath between pulleys, not through A2.
Over the middle phalanx, 7 to 10 mm long. Preserve more than 50% — combined A2 and A4 loss causes severe bowstringing. Repair with 6-0 suture if more than 25% is released.
Central and superficial in the carpal tunnel, directly under the transverse carpal ligament. Identify it before tendon access, divide the TCL on the ulnar side, and protect it with a retractor during tendon retrieval.
FDP retracts more than FDS (deeper position, lumbrical pull). Retrieve with milking, an 8 Fr feeding tube passed distal-to-proximal, or a proximal window — never force it, or the tendon shreds or the musculotendinous junction avulses.
Aftercare & Complications
Rehabilitation — early protected motion is as important as the surgery. The dorsal blocking splint (wrist 20 to 30 degrees flexion, MCP 60 to 70 degrees flexion, IP extended) is worn continuously for 4 to 6 weeks, removed only for supervised exercises. Motion begins within 1 to 5 days of surgery — frequency is critical: 10 repetitions every 1 to 2 hours while awake.
- Position
- 20–30° flexion
- Rationale
- Relaxes the flexor tendons
- Position
- 60–70° flexion
- Rationale
- Protects the repair from tension
- Position
- 0–20° flexion
- Rationale
- Prevents a flexion contracture
- Method
- Passive flexion, active extension against the dorsal block
- Advantages
- Simple, low rupture risk
- Disadvantages
- Needs a therapist
- Method
- Elastic-band traction from nail to wrist
- Advantages
- Dynamic, patient-driven
- Disadvantages
- Flexion-contracture risk
- Method
- Passively placed, brief active hold
- Advantages
- Progressive loading
- Disadvantages
- Complex compliance
- Method
- Gentle active flexion from day 3–5
- Advantages
- Best adhesion prevention
- Disadvantages
- Needs a 6–8 strand repair
Progression: - Day 1 to 5 — begin early protected motion (Duran, Kleinert or place-and-hold).
- Week 4 to 6 — begin gentle active flexion (remove the dorsal block for active exercises).
- Week 6 to 8 — light resistance (therapy putty, sponge).
- Week 8 to 12 — progressive strengthening and graded return to activity.
- No passive IP extension for 6 weeks — it ruptures the repair. Supervised hand therapy is essential, especially for Zone 2 repairs. A weak 2-strand repair may need 3 weeks of immobilisation before motion (with a higher adhesion rate), whereas a strong multi-strand repair allows safe early active motion. Full recovery takes 3 to 6 months.
Passive extension of the IP joints ruptures the repair. The patient must understand the protocol and comply — too much activity ruptures the repair, too little motion causes adhesions. Removing the splint before 4 weeks, or the wrong splint position (wrist and MCPs extended), also loads the repair and risks rupture.
Complications
- Recognition
- Reduced ROM at 6–12 weeks; active motion far worse than passive
- Prevention
- Multi-strand repair, early active motion, supervised therapy
- Management
- Aggressive therapy first; tenolysis at 3–6 months if severe and plateaued (now infrequent — Tang)
- Recognition
- Sudden loss of motion, palpable gap, FDP/FDS test becomes negative
- Prevention
- Minimum 4-strand core, epitendinous suture, dorsal blocking splint, no passive extension for 6 weeks
- Management
- Early re-exploration and re-repair, or graft. Pooled ~4% (Dy); 0–3% in modern multi-strand series
- Recognition
- Tendon tents on flexion, reduced power, PIP hyperextension
- Prevention
- Preserve more than 50% of A2 and A4; repair if more than 25% released
- Management
- Pulley reconstruction (FDS slip, palmaris, extensor retinaculum)
- Recognition
- Numbness, paraesthesia, neuroma pain at the incision
- Prevention
- Identify bundles early, spreading technique, loupes, gentle retraction
- Management
- Observation for neurapraxia; microsurgical repair or graft for transection
- Recognition
- Clicking or catching with flexion and extension, pain at the pulley level
- Prevention
- Smooth slim repair, test gliding before closure
- Management
- Revise the repair if early; pulley release if late (preserving A2 and A4)
- Recognition
- PIP flexion contracture, reduced passive ROM, joint stiffness
- Prevention
- Early protected motion, correct splint position, hand therapy
- Management
- Progressive splinting and therapy; capsulotomy if severe and static
Viva & Exam Focus
ZONESZONES — flexor tendon zone classification
STRANDSTRAND — core suture principles
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 28-year-old chef presents with a sharp laceration to the volar aspect of the middle finger at the PIP flexion crease. He cannot flex the DIP or PIP joints actively. What is your assessment and management?”
“During a Zone 2 flexor tendon repair you realise you have damaged 75% of the A2 pulley width. What are the implications and how do you manage this?”
“At 6 weeks after a Zone 2 flexor tendon repair your patient has very limited finger motion — only 30 degrees of PIP flexion and 10 degrees of DIP flexion. What is your differential diagnosis and management?”
Indications & timing
- Complete flexor tendon laceration needing repair (FDP and/or FDS)
- Primary repair: clean wound under 24 hours (ideal under 12 hours)
- Delayed primary for contaminated wounds; staged reconstruction for chronic injuries over 3 weeks
- Zone 2 (no man's land): both tendons, critical pulleys, highest complexity
Exposure
- Bruner zigzag for Zone 2 — apices at creases, 60-degree angles, never cross at 90 degrees
- Midlateral or volar Bruner (Zone 1), longitudinal palmar (Zone 3), standard carpal tunnel (Zone 4), volar forearm (Zone 5)
- Identify neurovascular bundles before deep dissection; protect the median nerve in Zone 4
- Open the sheath in windows between pulleys, preserving A2 and A4
The repair
- Retrieve gently (milking, 8 Fr feeding tube, proximal window); identify FDP (deep, single) and FDS (superficial, splits)
- Core suture: minimum 4-strand (6 to 8 better), 3-0 or 4-0 braided, bites 7 to 10 mm from the end
- Epitendinous: 5-0 or 6-0 monofilament, running locked 360 degrees — adds 10 to 50%
- Gap under 3 mm; test gliding through A2 and A4 before closure
Critical pulleys
- A2 (17 to 20 mm over the proximal phalanx) and A4 (7 to 10 mm over the middle phalanx) are critical
- Preserve more than 50% of each, or bowstringing with 30 to 40% power loss results
- A1, A3, A5 and all cruciate pulleys can be divided
- Repair with 6-0 suture if more than 25% of A2 or A4 is released
Aftercare
- Dorsal blocking splint: wrist 20 to 30 degrees flexion, MCP 60 to 70 degrees, IP extended
- Early protected motion from day 1 to 5, 10 reps every 1 to 2 hours (Duran, Kleinert or place-and-hold)
- No passive IP extension for 6 weeks (ruptures the repair)
- Progress: 4 to 6 weeks active flexion, 6 to 8 weeks light resistance, 8 to 12 weeks strengthening
Complications
- Adhesions: most common — prevented by early motion; therapy first, tenolysis at 3 to 6 months if plateaued
- Rupture: pooled about 4% (Dy); 0 to 3% in modern multi-strand series — re-repair or graft
- Bowstringing: from A2 or A4 loss — needs pulley reconstruction
- Stiffness: from immobilisation — prevented by early protected motion
Background & Evidence
The zones frame prognosis and approach. A flexor tendon laceration is a common hand injury, and outcome depends on the zone, the timing, the repair technique and the rehabilitation. The Verdan zones guide both: the further from the muscle (and the tighter the fibro-osseous sheath), the harder the repair. Zone 2 earned the name 'no man's land' because both tendons run together in a tight sheath with the critical A2 and A4 pulleys, and the older 2-strand repairs with immobilisation gave poor results — adhesions and rupture. Modern multi-strand repairs with an epitendinous suture, short-segment pulley venting and early active motion have converted Zone 2 into a zone with reliable good-to-excellent results.
- Location
- FDS insertion to fingertip
- Structures injured
- FDP only
- Key considerations
- Very distal FDP may need reinsertion to bone
- Location
- A1 pulley to FDS insertion
- Structures injured
- FDP and FDS plus pulleys
- Key considerations
- 'No man's land' — highest complexity
- Location
- Carpal tunnel exit to A1
- Structures injured
- FDP, FDS, lumbricals
- Key considerations
- Good exposure, no pulleys
- Location
- Carpal tunnel
- Structures injured
- FDP, FDS, median nerve
- Key considerations
- CTR for access; protect the median nerve
- Location
- Proximal to carpal tunnel
- Structures injured
- Muscle-tendon junctions
- Key considerations
- Adequate exposure; may need a forearm incision
Thumb zones: T1 (distal to the IP joint), T2 (A1 to the IP joint), T3 (thenar eminence).
- Location
- MCP joint
- Length
- 8–10 mm
- Critical?
- No
- Can divide?
- Yes — often divided
- Location
- Proximal phalanx
- Length
- 17–20 mm
- Critical?
- Yes — critical
- Can divide?
- No — preserve more than 50%
- Location
- PIP level
- Length
- Variable
- Critical?
- No
- Can divide?
- Yes
- Location
- PIP joint
- Length
- 3–5 mm
- Critical?
- No
- Can divide?
- Yes
- Location
- Between A3 and A4
- Length
- Variable
- Critical?
- No
- Can divide?
- Yes
- Location
- Middle phalanx
- Length
- 7–10 mm
- Critical?
- Yes — critical
- Can divide?
- No — preserve more than 50%
- Location
- Between A4 and A5
- Length
- Variable
- Critical?
- No
- Can divide?
- Yes
- Location
- DIP joint
- Length
- 3–5 mm
- Critical?
- No
- Can divide?
- Yes
References
Complications after flexor tendon repair: a systematic review and meta-analysis
- Pooled meta-analysis of 29 studies: re-operation 6%, rupture 4%, adhesions 4%
- Presence of an epitendinous (peripheral) suture decreased re-operation by 84%
- Core suture technique and epitendinous suture did not independently influence rupture rate
- No definitive improvement in reported complication rates comparing studies before and after 2000
Flexor tendon repair: recent changes and current methods
- Six high-volume units across four continents now use strong multi-strand core sutures with a simpler peripheral suture
- Venting of critical pulleys over a length less than 2 cm is safe and favours functional recovery
- Over 80% good or excellent outcomes achieved consistently after Zone 2 repair with infrequent need for tenolysis
- Zone 2 outcomes are not dissimilar to other zones, with very low to zero rupture incidence
Flexor Tendon Repair Techniques: M-Tang Repair
- M-Tang six-strand core repair with early active flexion used for Zone 2 digital flexor repair across six institutes
- Repair rupture incidence zero to 1% in Nantong, Yixing and Saint John; 3% in Florence and Heidelberg
- Good to excellent outcomes generally between 80% and 90%
- Few digits required secondary tenolysis
Zone 2 flexor tendon repairs using a tensioned strong core suture, sparse peripheral stitches and early active motion: results in 60 fingers
- 60 FDP tendons repaired with a tensioned 4-strand or 6-strand core suture and only 3-4 peripheral stitches
- A2 or A4 pulleys vented as necessary to allow gliding
- No repairs ruptured after early active flexion (follow-up 8-33 months)
- 52 of 60 (87%) fingers recovered good or excellent function by Tang criteria
Outcomes of Primary Flexor Tendon Repairs in Zones 2 and 3: A Retrospective Cohort Study
- Multicentre registry: 174 Zone 2 and 39 Zone 3 repairs using 4-6 strand FDP core sutures and an early active motion protocol
- Range of motion and grip strength improved significantly over time in both zones
- No relevant between-zone differences in DASH disability scores at any time point
- Patient satisfaction generally good to high (mean 6.8 to 8.0 on an 11-point scale)
Additional classic references: 1. Strickland JW. Development of flexor tendon surgery: twenty-five years of progress. J Hand Surg Am. 2000;25(2):214-235. 2. Tang JB. Clinical outcomes associated with flexor tendon repair. Hand Clin. 2005;21(2):199-210. 3. Elliot D, Giesen T. Primary flexor tendon surgery: the search for a perfect result. Hand Clin. 2013;29(2):191-206. 4. Boyer MI, Strickland JW, Engles D, Sachar K, Leversedge FJ. Flexor tendon repair and rehabilitation: state of the art in 2002. Instr Course Lect. 2003;52:137-161. 5. Tang JB, Amadio PC, Boyer MI, et al. Current practice of primary flexor tendon repair: a global view. Hand Clin. 2013;29(2):179-189. 6. Peck FH, Bücher CA, Watson JS, Roe A. A comparative study of two methods of controlled mobilization of flexor tendon repairs in zone 2. J Hand Surg Br. 1998;23(1):41-45. 7. Dowd MB, Figus A, Harris SB, Southgate CM, Foster AJ, Elliot D. The results of immediate re-repair of zone 1 and 2 primary flexor tendon repairs which rupture. J Hand Surg Br. 2006;31(5):507-513. 8. Sirotakova M, Elliot D. Early active mobilization of primary repairs of the flexor pollicis longus tendon with two Kessler two-strand core sutures and a strengthening circumferential suture. J Hand Surg Br. 2004;29(6):531-535. 9. Amadio PC. Friction of the gliding surface: implications for tendon surgery and rehabilitation. J Hand Ther. 2005;18(2):112-119.