Primary surgical repair of acute flexor tendon lacerations in Zone 2 ('no man's land') using multi-strand core suture techniques with pulley preservation and early active motion rehabilitation
- Zone 2 runs from the A1 pulley to the FDS insertion — 'no man's land' — where both FDP and FDS run together inside a tight sheath with the critical pulley system, giving it the worst prognosis and the highest adhesion risk.
- A2 and A4 are the CRITICAL pulleys, providing 75 percent of pulley force (A2 fifty percent, A4 twenty-five percent). Preserve at least 50 percent of each; all three cruciate (C) pulleys can be sacrificed for exposure.
- A minimum 4-strand core suture plus an epitendinous suture is required for early active motion (greater than 50 N strength). 6-strand techniques (Adelaide, Savage) deliver 60–80 N and are preferred.
- Early active motion started within 3–5 days roughly halves the adhesion rate compared with immobilisation — but it demands a strong repair, a compliant patient, and an expert hand therapist.
- The dorsal blocking splint holds the WRIST and MCPs FLEXED but the IP joints in FULL EXTENSION — counter-intuitive, but it protects the repair while preventing a PIP flexion contracture.
When & Why
Indication. An acute complete flexor tendon laceration in Zone 2 — classically a sharp knife or glass injury with loss of active flexion at the PIP and/or DIP joint — repaired primarily, ideally within 7–10 days, in a patient who is medically fit for surgery and able to commit to three months of intensive hand therapy. Repair is mandatory when the FDP is completely divided (it is the only flexor of the DIP joint; a finger without it is non-functional), and for a partial FDP laceration involving greater than 50 percent of the cross-section. Indications fall into absolute and relative groups: - Absolute: acute complete FDP laceration in Zone 2 (less than 7–10 days old); combined complete FDP and FDS lacerations; partial FDP laceration greater than 50 percent of cross-section; clean sharp injury with minimal contamination; patient medically fit and able to comply with therapy.
- Relative: isolated FDS laceration (controversial — many observe); subacute injury 10–21 days old (repair still possible but harder); partial laceration 25–50 percent (may heal without repair if FDP intact, but risks triggering); tendon injury with an associated digital nerve or artery injury that will be repaired at the same sitting. Contraindications also split into absolute and relative: - Absolute: active infection (pyogenic flexor tenosynovitis — drain first and reconstruct later); severe crush with devitalised tissue (staged reconstruction preferred); extensive soft-tissue loss preventing skin closure; a patient unable to comply with therapy (cognitive impairment, severe psychiatric disease); medical comorbidities precluding safe surgery (unstable cardiac disease, coagulopathy); severe underlying inflammatory arthropathy (rheumatoid — the repair is likely to fail).
- Relative: delayed presentation greater than 3 weeks (tendon retraction and scarring — consider staged); human or animal bite injury (high infection risk — irrigate, give antibiotics, delay repair 3–5 days); multiple-digit involvement (prolonged surgery — consider staging); heavy smoker; diabetes with neuropathy; previous failed flexor repair in the same digit; significant IP joint arthritis (repair will not improve a destroyed joint). Timing governs what is technically possible. The tendon ends are freshest and easiest to retrieve in the first week; after that, retraction and scarring make primary repair progressively harder, and beyond about six weeks a staged reconstruction is usually the better plan.
- Timing
- 0–7 days
- Characteristics and approach
- Ideal. Fresh tendon ends, minimal retraction and scarring, best functional outcomes
- Timing
- 7–21 days
- Characteristics and approach
- Still possible but technically harder; early retraction and scar; more dissection needed
- Timing
- 21 days to 6 weeks
- Characteristics and approach
- Challenging; significant retraction, often retrieval from palm or forearm; consider staged reconstruction
- Timing
- Greater than 6 weeks
- Characteristics and approach
- Primary repair not recommended; proceed to staged reconstruction (Hunter rod then graft) or tendon transfer
Favourable prognostic factors are a sharp clean laceration (not a crush), a single-structure injury, presentation within 48 hours, a young motivated patient, no crush component, and an index or long finger (which tolerate injury and FDS loss better than the ring or small). Adverse factors are the mirror image: crush mechanism, combined nerve/artery/bone injuries, delayed repair, significant pulley loss (greater than 50 percent of A2 or A4), infection, non-compliance, older age (over 60), smoking, diabetes, and high manual demands. Consent specifically for the intensive three-month therapy commitment, a realistic expectation of 75–85 percent good or excellent results, a 2–5 percent rupture rate, around a 15 percent chance of needing a second operation (tenolysis for stiffness or re-repair/reconstruction for rupture), and the possibility of triggering, a PIP contracture, or CRPS. Setup. Supine on the operating table, arm on a radiolucent hand table, shoulder abducted 80–90 degrees, elbow extended and hand supinated. Use a high-arm tourniquet at 250 mmHg (exsanguinate with Esmarch or elevation). Anaesthesia may be general, a brachial plexus block (axillary or supraclavicular), or — increasingly the modern standard — WALANT (wide-awake local anaesthesia, no tourniquet) using 1 percent lidocaine with 1:100,000 epinephrine, which lets you test active motion intra-operatively and tailors pulley venting to the actual gliding observed. Loupe magnification (2.5–3.5×) or the microscope (4–6×) is mandatory — this is fine, precision surgery.
The Operation
The goal is to retrieve both tendon ends, restore FDP (and selectively FDS) continuity with a strong multi-strand core plus an epitendinous suture that glides smoothly through a preserved A2/A4 pulley system, and protect the repair in a dorsal blocking splint so that early active motion can begin within days. The exposure is laid out in full below (and in depth on the Bruner volar zigzag approach to the digit page).
Operative sequence
- Supine, hand table, high-arm tourniquet at 250 mmHg, elbow extended, hand supinated; loupes (2.5–3.5×) on.
- Mark the laceration and plan the Bruner zigzag extensions BEFORE inflating the tourniquet, when skin landmarks are clearest.
- Have fine instruments, a paediatric feeding tube (6 Fr) for tendon retrieval, 3-0/4-0 braided non-absorbable core suture (Ethibond, Ticron, FiberWire), 5-0/6-0 monofilament for the epitendinous (Prolene, Nylon), and vessel loops ready.
- Extend the traumatic laceration with Bruner zigzag incisions, each segment angled 60 degrees to the flexion creases (never perpendicular — a 90-degree crossing causes web-space contracture).
- Place the apex of each zigzag at the mid-axial line, with each limb 5–8 mm long; extend proximally into the palm with further zigzags if the tendon has retracted.
- Raise full-thickness skin flaps (skin and subcutaneous fat together) — this avoids undermining and skin-flap necrosis, especially at the zigzag apices.
- A mid-lateral incision along the mid-axial line is the alternative: simpler and safer for the skin, preserves one neurovascular bundle unviolated, but gives more limited exposure. A straight volar longitudinal incision crossing the creases is contraindicated (hypertrophic scar and flexion contracture).
- Identify both digital neurovascular bundles BEFORE opening the sheath — they run 2–3 mm from the sheath edge; retract them gently with moist vessel loops and avoid cautery within 5 mm of the nerve.
- Mark the edges of the flexor sheath with a pen (it aids closure). Open the sheath BETWEEN pulleys to expose the tendons.
- Preserve A2 (over the proximal phalanx) and A4 (over the middle phalanx) — these are critical. Excise or widely vent the C1, C2 and C3 cruciate pulleys for exposure (all are expendable).
- If the repair will be bulky, the distal 25 percent of A2 or the proximal 25 percent of A4 may be vented provided the central portions are kept; at least 50 percent of each must remain intact.
- The proximal FDP end commonly retracts into the palm or carpal tunnel (pulled by lumbrical action and FDP muscle contraction); FDS usually retracts less and stays in the finger.
- Retrieve by (1) gentle milking from the proximal palm toward the finger, or (2) passing a paediatric feeding tube (6 Fr) proximally through the sheath, making a small 1 cm transverse incision in the distal palmar crease, retrieving the tube, passing a suture through the FDP end with a Keith needle, tying it to the tube and pulling the tendon back into the finger.
- Identify BOTH tendons and mark orientation (e.g. the volar surface, or an asymmetric suture) to avoid rotation, which causes maltracking and poor excursion.
- Define the extent of each laceration (complete versus partial, percentage of cross-section). FDP repair is mandatory — it is the only DIP flexor.
- Decide on FDS based on sheath capacity, the finger involved (index/long tolerate FDS loss better), and the extent of injury (see the FDS options below).
- Freshen the tendon ends with a sharp blade perpendicular to the long axis, with minimal debridement — trim only crushed tissue. Each millimetre of lost length adds tension and shortening, risking the quadriga effect.
- Place a minimum 4-strand, preferably 6-strand (Adelaide or Savage), core suture using 3-0 or 4-0 braided non-absorbable (Ethibond, Ticron, FiberWire).
- Use a locking configuration (20–30 percent stronger than grasping); purchase the tendon 7–12 mm from the cut edge with each pass to prevent cheese-wiring.
- Ensure no gap at the repair site (less than 1 mm acceptable), equal tension on all strands, and bury the knots so they do not catch on the pulleys.
- Strength: 4-strand = 40–50 N; 6-strand = 60–80 N. You need greater than 50 N to safely run an early active motion protocol.
- Run a continuous peripheral suture with 5-0 or 6-0 monofilament (Prolene, Nylon), starting 180 degrees from the core knot, bites 0.5–1 mm deep and 2 mm apart.
- Techniques include simple running, the cross-stitch (Lin) — a running locked figure-of-eight that is the strongest and gives the smoothest surface — and the Halstead modification.
- This adds 10–50 percent to repair strength (average 25 percent), inverts the tendon edges to create a smooth gliding surface, buries the core knots, and resists gap formation.
- Nuance: high-volume Zone 2 series (Pan/Tang) show that a well-tensioned strong multi-strand core needs only three to four sparse peripheral stitches rather than a full circumferential epitendinous suture — the core tension, not the peripheral stitch, is the key to gap resistance.
- If repairing FDS, fewer strands are acceptable (2–4 strand). If excising a slip, divide it distal to the chiasm of Camper and remove it completely to the A1 pulley level — never leave stumps (they form an adhesion nidus).
- The decision is a balance between preserving PIP flexion power and avoiding over-bulking in a tight sheath:
Maximum PIP flexion power; best in the ring and small fingers that need independent PIP flexion. Risks over-bulking and adhesions in a tight sheath.
The common compromise. Usually repair the radial/dorsal slip and excise the ulnar/volar slip — reduces bulk while keeping some FDS function. Remove the excised slip completely.
Preferred by some in a tight Zone 2 sheath — least bulk and fewest adhesions. Fingers function well on FDP alone, especially index and long.
Operative sequence (continued)
- With the sheath still open, passively flex and extend the finger while watching the tendon glide under loupe magnification. It must glide smoothly, with no catching or jerking.
- If it catches, troubleshoot in order: check the core knots are buried (not on the surface); check the epitendinous for bunching (redo with shallower, even bites); vent all C pulleys completely; if still bulky, consider venting the distal 25 percent of A2 or proximal 25 percent of A4 (keep the central portions); or sacrifice FDS to reduce bulk; and smooth any sharp pulley edges with micro-scissors.
- Any catching under direct vision in theatre WILL trigger post-operatively — fix it before closing. Confirm there is no bowstringing (the tendon should stay close to bone on flexion).
- Close the sheath loosely with 5-0 or 6-0 absorbable suture (Vicryl, Monocryl), leaving vents — do not close the whole sheath circumferentially.
- Close enough to maintain pulley geometry but allow synovial fluid circulation; many surgeons close only at the pulley sites and leave the cruciate areas open.
- The principle is a loose closure with no tension on the repair. Tight circumferential closure strangulates the repair and guarantees triggering.
- Close the skin with 4-0 or 5-0 non-absorbable interrupted sutures (Nylon, Prolene), vertical mattress or simple interrupted, tension-free. For a Bruner incision, close the zigzag apices first to align the pattern.
- Apply a non-adherent dressing (Xeroform, Adaptic) directly on the wound, then light gauze — no pressure dressing.
- Check digital perfusion: capillary refill less than 2 seconds, fingertip pink. A dusky finger or slow refill means the dressing is too tight or a vessel has been injured.
- Apply a dorsal blocking splint in theatre, moulded dorsally in thermoplastic material so it blocks extension but allows full flexion.
- Position: wrist 20–30 degrees flexion, MCPs 70–80 degrees flexion, IP joints 0 degrees (full extension). The wrist and MCPs are flexed to take tension off the repair; the IP joints are kept extended to prevent a PIP flexion contracture.
- Within this splint the patient can make a full fist but cannot extend the wrist or MCPs. (A Kleinert splint with rubber-band traction from nail to palmar wrist band is an alternative that gives passive flexion and blocks active extension.)
- Before closing, document the repair quality: visual inspection (no gap, smooth contour, no bunching); passive ROM (smooth gliding through the pulleys); gentle traction on the proximal tendon (should hold 30–40 N without gapping); and the cascade (the finger rests in a normal cascade with the wrist neutral).
- Classify the repair — OPTIMAL (6-strand plus epitendinous plus pulleys intact), GOOD (4-strand plus epitendinous plus greater than 80 percent pulleys), ACCEPTABLE (4-strand plus partial epitendinous), SUBOPTIMAL (fewer than 4 strands or greater than 50 percent pulley loss) — because this determines the rehabilitation protocol.
- If a fracture, artery and/or nerve are also injured, repair in sequence: (1) skeletal stability first (K-wire or mini-plate), (2) artery if both are cut (at least one patent artery per digit), (3) flexor tendon (the longest step — do it before the nerve so you can tension the tendon without pulling the nerve), (4) digital nerve last (if both are cut; a single clean nerve laceration may be observed).
- Combined injuries carry a worse prognosis (good results fall from 75–85 percent to 50–60 percent from added scarring), and often warrant a more conservative (passive) motion protocol.
- Radial and ulnar digital neurovascular bundles — run 2–3 mm from each sheath edge. Identify them before opening the sheath, retract gently with vessel loops, avoid cautery near the nerve, and preserve at least one digital artery per finger.
- A2 and A4 annular pulleys — provide 75 percent of pulley force. Preserve at least 50 percent of each (ideally the central portion); vent only the distal A2 or proximal A4 if needed. Loss of greater than 50 percent of either causes bowstringing and a weak grip even if the tendon heals.
- Vincula — the delicate dorsal vascular mesenteries (vinculum longus and brevis to FDP and FDS) that feed the tendon. Minimise sheath opening and handle tendon gently; vincula damage brings ischaemia and adhesions.
The dorsal blocking splint holds the WRIST and MCPs FLEXED (to protect the repair from tension) but the IP joints in FULL EXTENSION (to prevent a PIP flexion contracture). Patients can make a full fist inside the splint but cannot extend the wrist or MCPs. Getting the IP joints flexed instead of extended is the classic avoidable error — it seeds a contracture that is very hard to reverse.
Passively flex and extend the finger while watching the tendon glide before you close. Any catching under direct vision WILL be worse once swelling and inflammation set in — it predicts triggering, adhesions, and a higher rupture risk. Address the cause (buried knots, epitendinous bunching, inadequate cruciate venting, FDS bulk) until gliding is completely smooth. Never accept gliding that is merely "good enough".
Aftercare & Complications
Early active motion is the gold-standard protocol — it roughly halves the adhesion rate compared with immobilisation — but it requires a strong repair (greater than 50 N), a motivated compliant patient, an expert hand therapist, and close weekly monitoring at first.
- Timing
- Day 0–2
- Splint
- Dorsal blocking splint applied in theatre
- Therapy
- Hand elevated above the heart; ice and pain control only
- Timing
- Day 3–5
- Splint
- Splint on continuously
- Therapy
- Active flexion (make a fist — full composite flexion), passive extension, place-and-hold 5 seconds; 10 reps every waking hour (8–10 sessions/day)
- Timing
- Week 1–4
- Splint
- Splint full-time (off only for therapy)
- Therapy
- Progress active flexion; add blocking (isolate FDP/FDS); weekly ROM checks; sutures out day 10–14
- Timing
- Week 4–6
- Splint
- Splint continues
- Therapy
- Gentle passive extension out of the splint (therapist-supervised); differential gliding
- Timing
- Week 6–8
- Splint
- Daytime off gradually, night splint 2–4 more weeks
- Therapy
- Progressive active ROM; light ADLs
- Timing
- Week 8–10
- Splint
- Discontinue splint
- Therapy
- Gentle strengthening (soft putty); light gripping
- Timing
- Week 10–12
- Splint
- None
- Therapy
- Progress resistance and function; unrestricted activities by week 12 (manual labourers 14–16 weeks)
Alternative protocols apply when the repair is not strong enough for full early active motion, or compliance is in doubt:
- Mechanism
- Active flexion within a dorsal blocking splint
- Adhesion rate
- 10–15%
- Use when
- Strong repair (greater than 50 N), compliant patient, expert therapist — the default
- Mechanism
- Rubber-band traction from nail to palmar wrist band — passive flexion, active extension blocked
- Adhesion rate
- 15–25%
- Use when
- Repair strength questionable or compliance concerns
- Mechanism
- Limited-arc active flexion to the distal palmar crease, place-and-hold, no forceful flexion
- Adhesion rate
- Intermediate
- Use when
- Moderate-strength repairs — a compromise
- Mechanism
- Splint for 3 weeks, then passive 3 weeks, then active after 6 weeks
- Adhesion rate
- 30–40%
- Use when
- Very weak repairs, poor compliance, combined injuries — essentially abandoned in modern practice
Monitoring. Review weekly for the first month (active flexion ROM fingertip-to-distal-palmar-crease, passive extension deficit at each joint, signs of rupture, infection, triggering, and PIP contracture), then biweekly and monthly adding strength and functional testing (Jamar grip, pinch gauge, Jebsen-Taylor). Red flags requiring urgent assessment are sudden loss of active flexion (rupture), severe increasing pain with fusiform swelling (infection or CRPS), locking or severe triggering, a progressive PIP contracture greater than 20 degrees, and Kanavel's signs of flexor sheath infection. A plateau — active ROM still less than 50 percent of normal at three months despite optimal therapy — prompts consideration of tenolysis at four to six months once scar has matured. Complications. The overall complication rate is 25–35 percent, though most are minor. The table below covers recognition, prevention and management of the major ones.
- Recognition
- Progressive limitation of active ROM despite full passive ROM (active lag); plateau by 8–12 weeks; active flexion less than 50 percent of passive
- Prevention
- Atraumatic technique; strong repair allowing early active motion; preserve pulleys and vincula; early active motion within 3–5 days
- Management
- Intensive therapy for 3–4 months; if ROM is less than 50 percent and plateaued, tenolysis at 4–6 months (gain in 60–70 percent; 5–10 percent rupture post-tenolysis)
- Recognition
- Sudden loss of active flexion, often a 'pop'; cannot flex the DIP with the PIP held extended; palpable gap; diagnosis is clinical
- Prevention
- Minimum 4-strand plus epitendinous (greater than 50 N); patient education on avoiding forceful extension; protocol matched to repair strength; smooth gliding; weekly monitoring
- Management
- Early rupture (less than 6 weeks) — direct re-repair may be attempted but fails in 30–40 percent; late or failed re-repair — staged reconstruction (Stage 1 Hunter rod plus pulley repair, Stage 2 tendon graft), 60–75 percent good results
- Recognition
- Progressive loss of PIP extension, initially flexible then fixed; volar plate thickening; pain on passive extension stretch
- Prevention
- Dorsal blocking splint with IP joints in full extension from day 0; early extension exercises; serial static splinting if a deficit develops
- Management
- Less than 30 degrees at 3 months — static progressive/dynamic splinting; 30–50 degrees persistent beyond 6 months — PIP capsulotomy (plus tenolysis); greater than 50 degrees or failed capsulotomy — fusion or arthroplasty
- Recognition
- Catching or locking with active motion; palpable click over A1 or A2; sudden jerking rather than the smooth limit of adhesions
- Prevention
- Confirm smooth gliding intra-operatively; vent cruciate pulleys liberally; vent distal A2 or proximal A4 if bulky; do not close the sheath tightly
- Management
- Mild — therapy, NSAIDs, observation (often settles over 6–12 weeks); persistent beyond 3 months — A1 release or revision pulley venting; severe locking — earlier release
- Recognition
- Kanavel's four signs: fusiform finger swelling, flexed posture, tenderness along the whole sheath, pain on passive extension (most sensitive); fever, raised WCC/CRP
- Prevention
- Thorough irrigation (6–9 L for contaminated wounds); debridement; prophylactic antibiotics; delayed primary repair for heavily contaminated wounds
- Management
- Urgent irrigation and debridement within 24 hours; IV antibiotics (flucloxacillin or vancomycin if MRSA risk); leave open, delayed closure at 3–5 days; delay beyond 48 hours carries up to 30 percent amputation
- Recognition
- Cannot fully flex adjacent fingers (shared FDP muscle belly) when the repaired FDP is too short or over-tensioned; extension lag in adjacent digits on isolated FDP testing
- Prevention
- Minimal debridement to preserve length; repair with the finger in neutral (not flexed); check adjacent finger flexion intra-operatively; do not over-tighten
- Management
- Clinical diagnosis; if greater than 1 cm adjacent lag and disabling — tendon lengthening or FDP tenotomy of the shortened finger; accept if mild
- Recognition
- Budapest criteria — symptoms in 3 of 4 categories (sensory, vasomotor, sudomotor, motor); pain disproportionate to injury; shiny oedematous hand; temperature asymmetry
- Prevention
- Early mobilisation; adequate analgesia; avoid prolonged splinting; gentle therapy
- Management
- Therapy mainstay (desensitisation, stress loading, mirror therapy, graded motor imagery); neuropathic agents (gabapentin, pregabalin); sympathetic blocks; psychological support; most resolve over 6–12 months, 10–20 percent become chronic
Return to function. Light work and ADLs by 6–8 weeks, moderate work by 10–12 weeks, heavy manual labour by 14–16 weeks, and contact sports by 12–16 weeks. Maximum medical improvement plateaus at 6–9 months.
Viva & Exam Focus
PULLEYPULLEY — the critical pulleys to preserve
STRANDSTRAND — multi-strand repair essentials
- Location
- 2–3 mm radial to the sheath along the digit, with the radial digital artery
- How to protect it
- Raise full-thickness flaps; identify before opening the sheath; retract gently with a vessel loop; no cautery within 5 mm of the nerve
- Location
- 2–3 mm ulnar to the sheath, mirror image of the radial bundle
- How to protect it
- Identify early; gentle retraction; preserve at least one digital artery per finger
- Location
- Over the proximal half of the proximal phalanx — 15–17 mm (index/long), 12–15 mm (ring/small); 50 percent of pulley force
- How to protect it
- Preserve at least 50 percent (central); may vent the distal 25 percent if bulky; mark edges before opening
- Location
- Over the middle third of the middle phalanx — 7–9 mm; 25 percent of pulley force
- How to protect it
- Preserve at least 50 percent (central); may vent the proximal 25 percent; combined A2 plus A4 must exceed 1.2 cm
- Location
- Vinculum longus and brevis to FDP and FDS — delicate dorsal vascular mesenteries within the sheath
- How to protect it
- Minimise sheath opening; handle tendon gently; consider partial sheath closure to preserve synovial nutrition
Clinical Decision Scenarios
Practise clinical reasoning and management decisions out loud
“A 28-year-old chef presents 6 hours after cutting his right long finger with a sharp knife. He has lost active flexion at the DIP and PIP joints. Describe your management including surgical technique.”
“You are repairing a Zone 2 flexor tendon injury and intra-operatively the repair catches and triggers as it passes through the A2 pulley. What are the causes and how would you address this?”
“A 35-year-old manual labourer had a Zone 2 flexor tendon repair 3 weeks ago with an early active motion protocol. He now has sudden loss of active DIP flexion after lifting a heavy box, with no active FDP function. Discuss your management options and their outcomes.”
Indication
- Acute complete FDP laceration in Zone 2 (less than 7–10 days); combined FDP and FDS; partial FDP greater than 50 percent of cross-section
- Contraindicated with active infection (drain first), severe crush (staged), or a patient unable to comply with therapy
- Favourable: sharp injury, single structure, young patient, index/long finger, early presentation
Key anatomy
- Zone 2 = A1 pulley to FDS insertion = 'no man's land' — both tendons in a tight sheath with the critical pulleys, worst prognosis
- A2 (proximal phalanx) is 50 percent of pulley force, A4 (middle phalanx) is 25 percent — together 75 percent; all C pulleys expendable
- FDP inserts on the distal phalanx (the only DIP flexor — mandatory to repair); FDS splits at the chiasm of Camper to insert on the middle phalanx
- Digital neurovascular bundles run 2–3 mm from the sheath edge — identify before opening the sheath
Critical steps
- Bruner zigzag at 60 degrees to creases (never 90); apex at mid-axial line; full-thickness flaps
- Open the sheath preserving A2 and A4 (at least 50 percent each), vent all C pulleys
- Retrieve the proximal end (FDP retracts more than FDS — feeding-tube technique); minimal debridement to preserve length
- 6-strand Adelaide core (60–80 N), 3-0/4-0 braided non-absorbable, locking, 7–10 mm purchase; running epitendinous 6-0 cross-stitch
- Confirm smooth gliding (catching WILL trigger); loose sheath closure with vents
- Dorsal blocking splint: wrist 20–30 degrees flexion, MCPs 70–80 degrees flexion, IP joints 0 degrees extension; early active motion day 3–5
Technique pearls
- Repair strength hierarchy: 2-strand 30 N (inadequate), 4-strand 40–50 N (minimum for early active), 6-strand 60–80 N (preferred); need greater than 50 N
- Epitendinous adds 10–50 percent strength and a smooth gliding surface — not optional
- FDS: repair both (bulky), repair one/excise one (common compromise), excise both (least adhesion)
- Combined injuries: repair bone first, then artery, then tendon, then nerve — worse prognosis (50–60 percent vs 75–85 percent)
Complications
- Adhesions (15–25 percent need tenolysis) — most common; active ROM less than 50 percent of passive
- Rupture (2–5 percent) — peak weeks 2–4; re-repair fails in 30–40 percent, prefer staged reconstruction (60–75 percent good)
- PIP contracture (10–20 percent) — prevent with IP joints extended in the splint from day 0
- Infection (1–3 percent) — Kanavel's signs; surgical emergency within 24 hours
- CRPS (2–5 percent) — early motion reduces risk
Background & Evidence
Zone classification. Verdan's five-zone system divides the flexor system from distal fingertip to forearm; Zone 2 — the segment from the A1 pulley to the FDS insertion, nicknamed "no man's land" by Bunnell — is the hardest because both tendons and the critical pulleys coexist in a tight sheath.
- Anatomy
- FDS insertion (mid-middle phalanx) to FDP insertion (base of distal phalanx)
- Significance and prognosis
- FDP only (FDS already inserted); single-tendon repair, relatively simple
- Anatomy
- A1 pulley to FDS insertion — 'no man's land'
- Significance and prognosis
- Both FDP and FDS in a tight sheath with A2 and A4; worst prognosis, highest adhesion risk — the focus of this operation
- Anatomy
- Distal edge of the carpal tunnel to the A1 pulley (palm)
- Significance and prognosis
- Lumbricals originate from FDP here; more space, better prognosis; watch digital nerve branches
- Anatomy
- Within the carpal tunnel
- Significance and prognosis
- Eight FDP, four FDS and the median nerve; median nerve proximity complicates repair
- Anatomy
- Proximal to the carpal tunnel (distal forearm)
- Significance and prognosis
- Musculotendinous junction; median and ulnar nerve injuries common; ample space and the best prognosis
Pulley anatomy and biomechanics. The flexor sheath has five annular pulleys (A1–A5) and three cruciate pulleys (C1–C3). The annular pulleys are the functionally important ones: A1 sits over the MCP joint (8–10 mm), A2 over the proximal half of the proximal phalanx (15–17 mm in index/long, 12–15 mm in ring/small), A3 over the PIP joint (3–5 mm), A4 over the middle third of the middle phalanx (7–9 mm), and A5 over the DIP joint (variable). The cruciate pulleys (C1 between A2 and A3, C2 between A3 and A4, C3 between A4 and A5) are thin and provide minimal force — all can be sacrificed. Biomechanically A2 provides about 50 percent of total pulley force, A4 about 25 percent (together 75 percent), and at least 1.2 cm of combined A2/A4 length is needed to prevent bowstringing. Classic teaching is to preserve at least 50 percent of both A2 and A4. Modern evidence (Tang, Pan, Lalonde) reframes this as case-specific venting judged by wide-awake intra-operative excursion testing — controlled venting of A2 and/or A4 is widely accepted provided the core is well tensioned and active gliding confirms no clinically significant bowstringing. FDS, FDP and the vincula in Zone 2. FDS inserts on the volar middle third of the middle phalanx, splitting into radial and ulnar slips that decussate around FDP at the chiasm of Camper; it provides PIP flexion and grip. FDP inserts on the volar base of the distal phalanx and is the only DIP flexor — it must be repaired; because all four FDP tendons share a common muscle belly, shortening one limits excursion of the others (the quadriga effect). Both tendons draw their blood supply from the vincula (vinculum longus and brevis, to FDP and FDS), delicate mesenteries entering the tendons dorsally within the sheath — which is why minimal sheath opening and gentle handling preserve vascularity and limit adhesions. Core suture strength governs the rehabilitation you can safely run. The strand count directly sets breaking strength and therefore how aggressively the tendon can be mobilised.
- Strands
- 2
- Strength
- About 30 N
- Role
- Inadequate for early active motion — superseded
- Strands
- 4
- Strength
- 40–50 N
- Role
- Minimum for early active motion
- Strands
- 6
- Strength
- 60–80 N
- Role
- Preferred — highest strength, most aggressive therapy tolerated
Key evidence. The multi-strand-plus-early-active-motion paradigm rests on Savage and Risitano's original six-strand series (1989; 81 percent excellent or good by Buck-Gramcko) and the canine biomechanical work of Winters et al (1998), which showed Savage and 8-strand repairs significantly stronger than Tajima/Kessler without sacrificing excursion. Lin et al (1988) quantified the epitendinous contribution — a running-locking peripheral suture was 1.68–3.77 times stronger than simple or Lembert running and gave better edge inversion and a smoother gliding surface. Pan et al (2019) reported 60 fingers with no ruptures and 87 percent good or excellent using a tensioned strong core with only three to four sparse peripheral stitches and pulley venting as needed — challenging the dogma that 50 percent of A2/A4 must always be preserved and that a full circumferential epitendinous suture is essential. The contemporary Tang and Lalonde review (2026) frames Zone 2 repair as a balance between strength and free gliding, with pulley venting judged by wide-awake excursion testing rather than a fixed percentage. On rehabilitation, the Cochrane review (2015) found early active motion reduces adhesions and improves total active motion at 6 and 12 months with a slightly higher rupture rate (around 4 percent versus 2 percent) — a worthwhile trade-off that requires a repair stronger than 50 N. Functional outcomes. With modern technique, 75–85 percent achieve good or excellent results by Strickland or Buck-Gramcko scoring (good equals total active motion greater than 50 percent of normal; excellent greater than 75 percent), with mean DASH scores around 10–15. The overall complication rate is 25–35 percent (most minor): adhesions requiring tenolysis 15–25 percent, rupture 2–5 percent, PIP contracture greater than 20 degrees 10–20 percent, triggering 5–10 percent, infection 1–3 percent, CRPS 2–5 percent, and a 20–30 percent rate of needing a secondary procedure.
References
Flexor tendon repair using a 'six strand' method of repair and early active mobilisation
- Original description of the six-strand (Savage) core repair combined with immediate active mobilisation in a protective splint
- 36 fingers treated — 63 percent of lacerations in Zone 2 and 27 percent in Zone 1
- Buck-Gramcko assessment — 69 percent of Zone 2 fingers and 100 percent of Zone 1 fingers excellent or good; 81 percent excellent or good overall
Zone 2 flexor tendon repairs using a tensioned strong core suture, sparse peripheral stitches and early active motion: results in 60 fingers
- 60 FDP repairs with a tensioned 4- or 6-strand core and only three to four peripheral stitches; A2 or A4 pulleys vented as needed
- No ruptures and 52 of 60 fingers (87 percent) good or excellent by Tang criteria at 8–33 months follow-up
- A properly tensioned strong core requires only sparse peripheral stitches — a circumferential epitendinous suture is not always mandatory if the core is well tensioned
The effects of multiple-strand suture methods on the strength and excursion of repaired intrasynovial flexor tendons: a biomechanical study in dogs
- In-vivo canine model comparing Kessler, Tajima, Savage and 8-strand repairs under controlled passive motion
- Savage and 8-strand repairs were significantly stronger than the Tajima method at 3 and 6 weeks; 8-strand stronger than Savage at each interval
- Suture method did not impair tendon excursion or joint rotation — higher strand count widened the safety margin for early loaded motion
Biomechanical studies of running suture for flexor tendon repair in dogs
- Compared a running-locking peripheral (epitendinous) suture with simple circumferential and Lembert running sutures
- The locking peripheral suture was 3.77 times and 1.68 times stronger and 1.73 times and 1.26 times stiffer than the simple and Lembert techniques respectively
- A peripheral locking suture also improves tendon-edge inversion and creates a smoother gliding surface
Achieving balance in tendon repair
- Contemporary review framing Zone 2 repair as a balance between mechanical strength and free tendon gliding
- Pulley venting is a trade-off — too little risks catching/rupture, too much risks bowstringing; wide-awake excursion testing identifies the ideal venting length
- Slight bulkiness with tendon ends in close contact is acceptable; partial-range early active flexion maintains glide without rupture