Flexor tendon injuries Flashcards
What are the 5 anatomical zones of flexor tendon injury as described by Kleinert and Verdan, and what are their boundaries?
Zone I: Distal to FDS insertion (contains only FDP);
Zone II: From A1 pulley to FDS insertion (‘no man’s land’);
Zone III: From distal palmar crease to A1 pulley;
Zone IV: Carpal tunnel;
Zone V: Proximal to carpal tunnel in forearm.
These zones guide surgical approaches and prognostic considerations due to their unique anatomical characteristics.
How did Tang subclassify different areas of Zone II flexor tendon injuries?
Tang subclassified Zone II into zones IIa, IIb, IIc, and IId, based on the relationship of the FDS relative to the FDP and the A2 pulley. Zone IIc specifically refers to the area covered by the A2 pulley, which is the largest and most rigid pulley of the fingers, requiring special consideration during repair.
What is the anatomical arrangement of tendons in the carpal tunnel from radial to ulnar, and why is this clinically relevant in zone IV injuries?
From radial to ulnar:
FPL (most radial and deep to median nerve),
FDS of index and middle fingers (superficial),
FDS of ring and small fingers (deep), and
FDP tendons (deepest).
This arrangement is critical in zone IV repairs to ensure proper tendon identification and to avoid iatrogenic damage to the median nerve during surgical exploration.
What is the Linburg-Comstock anomaly and how might it affect flexor tendon repair?
The Linburg-Comstock anomaly is an interconnection between the FPL and FDP of the index finger that may be muscular or tendinous. Present in 31% of patients unilaterally and 16% bilaterally, it must be recognized during tendon exploration and repair to avoid mistaking it for pathology and to plan appropriate repair techniques.
Describe the three phases of flexor tendon healing biology.
1) Early inflammatory phase: Initial response with inflammatory cell infiltration and minimal strength;
2) Intermediate active repair phase: Fibroblast proliferation and collagen synthesis with increasing strength;
3) Late remodeling phase: Reorganization of collagen and maturation of scar tissue. Understanding these phases guides rehabilitation timing and progression.
What are the two pathways of tendon healing and how do they affect adhesion formation?
The intrinsic pathway involves cells from within the epitenon, resulting in restoration of the gliding surface with minimal adhesions. The extrinsic pathway involves recruitment of cells from the synovial sheath, contributing to peritendinous adhesion formation. The balance between these pathways determines the quality of healing and functional outcome.
In a 4-strand flexor tendon repair, what is the optimal core suture purchase length and why?
The optimal core suture purchase is 7-10mm from the tendon laceration. Studies by Cao et al. demonstrated that gap and ultimate strengths increased significantly as suture purchase increased from 0.4cm to 0.7cm, but remained constant with purchases from 0.7cm to 1.2cm, suggesting 7-10mm as the ideal balance between repair strength and minimizing tissue handling.
What is the significance of gap formation at the repair site in flexor tendon repairs?
Gelberman demonstrated that a gap at the repair site of more than 3mm within the early phases of healing is detrimental to accrual of repair strength. Repairs without gaps showed considerable increase in repair strength. Gap formation can lead to adhesions, decreased tendon excursion, and potential rupture, necessitating intraoperative testing to ensure no early gap formation.
What are the biomechanical advantages of multi-strand core suture repairs compared to traditional 2-strand repairs?
Multi-strand repairs (4-8 strands) provide:
1) Greater tensile strength (43% stronger with 8-strand vs. 4-strand);
2) Better gap resistance;
3) Improved load-to-failure metrics;
4) Enhanced early active motion capability;
5) Lower rupture rates.
These advantages make multi-strand repairs the current standard for flexor tendon injuries, particularly in zones II and III.
What is the M-Tang repair method and what are its clinical advantages?
The M-Tang repair is a 6-strand repair created with two groups of looped sutures using an M-shaped configuration. Its advantages include: superior tensile strength, minimal gap formation, compatibility with early active motion protocols, reduced rupture rates (as low as 0% in some studies), and excellent clinical outcomes with 83-91% achieving good to excellent results in zone II repairs.
What is the clinical significance of venting the A2 or A4 pulley during flexor tendon repair?
Venting of the A2 or A4 pulley (within 2cm) facilitates surgical access, reduces repair site friction, improves tendon gliding, and prevents repair site impingement. Studies by Moriya and Tang demonstrated that limited pulley venting does not produce clinically significant bowstringing despite theoretical concerns, while improving surgical access and outcomes.
According to the Leddy and Packer classification, how are Zone I FDP avulsion injuries categorized?
Type I: FDP laceration with retraction to the palm level;
Type II: FDP laceration with retraction to the PIP joint level;
Type III: FDP avulsion with a bone fragment limiting retraction to the DIP joint level.
This classification guides treatment approach, with more proximal retraction generally requiring more extensive surgical exposure and different repair techniques.
What special considerations are important when repairing the flexor pollicis longus tendon compared to finger flexor tendons?
FPL repair requires:
1) Wider exposure due to potential retraction into the carpal tunnel;
2) Consideration of the unique pulley system (A1, oblique, A2) with the oblique pulley being the primary restraint;
3) Lower reported adhesion rates but historically higher rupture rates;
4) Potentially venting one or two pulleys safely without risking bowstringing;
5) Similar rehabilitation protocols as finger repairs.
What is the ‘50% rule’ in partial flexor tendon lacerations and what is its biomechanical basis?
The ‘50% rule’ suggests repair when 50% or more of the tendon has been lacerated. Kondratko’s biomechanical testing showed marked increase in stress concentration starting at 47.2% tendon laceration width. Repair prevents late rupture and limits risk for tendon entrapment within the tendon sheath, even though tendons retain tensile strength with large degrees of laceration (60-75%).
What are the primary criteria for determining the need for emergency flexor tendon repair?
Emergency repairs are required only when digital blood supply has been substantially compromised. Otherwise, acute flexor tendon injuries should ideally be repaired within the first 7 days after injury. Delayed repair risks proximal tendon retraction and remodeling that complicates repair or necessitates tendon grafting.
What is the digital extension-flexion test during flexor tendon repair and why is it important?
The digital extension-flexion test, proposed by Tang, involves moving the repaired digit from full extension to marked flexion intraoperatively to ensure: 1) No gapping at the repair site during full extension; 2) No impingement of the repair site against the pulley during digital flexion. This is a critical checkpoint of repair quality that predicts functional outcomes.
What are the key components of the Nantong protocol for post-repair rehabilitation?
The Nantong protocol involves:
1) True active flexion from day 4-5 post-repair;
2) 4-6 daily exercise sessions of 15-20 minutes each;
3) Passive motion through full range followed by 40-60 runs of active flexion to 1/2 or 2/3 of initial range;
4) Out-of-splint motion with MCP joint in mild flexion;
5) Progression to full active flexion at weeks 3-4;
6) Specific DIP joint therapy to prevent stiffness.
When repairing both FDS and FDP tendons in zone II, what criteria guide the decision to repair both tendons versus FDP only?
Both tendons should be repaired only when they are tidy and easy to repair.
FDP-only repair is preferred when:
1) The repair is in zone IIc (A2 pulley area) where the sheath tunnel is narrowest;
2) The laceration is distal to the decussation of the FDS;
3) The injury is severe with difficulty obtaining a smooth repair;
4) Studies show no significant difference in finger mobility between full repair and selective repair strategies.
What is the ‘wide-awake’ approach to flexor tendon repair and what are its specific advantages?
The wide-awake approach uses local anesthetic (1% lidocaine with 1:100,000 epinephrine) without tourniquet or general anesthesia. Advantages include: 1) Intraoperative active motion testing to assess repair integrity and gliding; 2) Immediate adjustment of repair if gapping occurs; 3) Reduced costs and complications associated with general anesthesia; 4) Patient education during surgery about rehabilitation expectations.
For zone I injuries with less than 1cm distal tendon stump, compare the surgical options for repair and their relative advantages.
Options include:
1) Pull-out wire/button technique (traditional but with nail deformity risk);
2) Micro-suture anchors (56% good/excellent results, easier technique but risk of dorsal cortex penetration);
3) Direct repair to short stump and periosteum (Tang technique with 10-12 strand repair);
4) Screw or interosseous wire for large bony fragments.
Direct repair techniques have shown improved outcomes with fewer complications than traditional pull-out methods.
What factors predict poor outcomes following zone II flexor tendon repair?
Poor prognostic factors include:
1) Saw/crush injuries versus sharp lacerations;
2) Concomitant digital nerve injuries;
3) Multiple digit injuries;
4) Smoking history;
5) Advanced patient age (>37 years);
6) Delayed presentation (>7 days);
7) Lack of compliance with rehabilitation;
8) Inadequate repair technique with fewer than 4 strands;
9) Significant pulley damage requiring reconstruction.
How does the blood supply to flexor tendons influence repair techniques and healing?
Flexor tendons receive blood supply via:
1) Surface diffusion through canaliculae;
2) Direct blood flow from vincula supplied by the ladder vessels from proper digital arteries. The vincula should be preserved during repair to maintain vascular networks that aid healing. Intact vincula also prevent proximal retraction, facilitating repair and producing better outcomes.
What is the difference between locking and grasping core suture techniques in flexor tendon repair?
Locking sutures (e.g., Kessler, modified Kessler) capture tendon fibers in a loop that tightens under tension, providing greater pullout strength but potentially causing more ischemia. Grasping sutures (e.g., Bunnell) hold fibers without a locking mechanism, offering less pullout strength but potentially less tissue damage. Locking techniques are generally preferred for their superior biomechanical properties.
What are the main differences between early passive motion and early active motion rehabilitation protocols after flexor tendon repair?
Early passive motion protocols (Duran, Kleinert) have lower rupture rates (4% vs. 5%) but higher rates of decreased range of motion (9% vs. 6%). Early active motion protocols produce better overall range of motion (156° vs. 128°) and patient satisfaction. The choice depends on repair strength, patient compliance, and associated injuries.
How do you manage a patient with both flexor tendon and digital nerve injuries in the same digit?
Management includes:
1) Microscope use for both repairs;
2) Typically repair the nerve first to avoid manipulation of the tendon repair;
3) Consider a stronger tendon repair (6-8 strands) due to poorer prognosis;
4) Modified rehabilitation with delayed active motion protocols;
5) Patient counseling about diminished prognosis;
6) Close monitoring for adhesions between nerve and tendon repairs;
7) Earlier consideration of tenolysis if significant adhesions develop.
What biomechanical properties should be considered when selecting suture material for flexor tendon repair?
Consider:
1) Tensile strength (3-0 is 49% stronger than 4-0);
2) Handling characteristics;
3) Knot security (monofilament vs. braided);
4) Gliding resistance;
5) Work of flexion;
6) Gap formation resistance.
Clinically, nylon or coated nylon sutures remain popular, with monofilaments preferred in zones II/III, while Supramid (looped monofilament-like) is widely used worldwide.
What is the role of epitendinous suture in flexor tendon repair and how does it affect repair biomechanics?
The epitendinous suture:
1) Smooths tendon edges to improve gliding;
2) Augments core suture strength (by 10-50%);
3) Reduces gap formation;
4) Decreases gliding resistance when performed first (epitendinous-first technique);
5) Prevents bunching during core suture placement.
However, deeper epitendinous sutures may increase gliding friction and tendon adhesion risk.
How has the concept of ‘no man’s land’ (Zone II) evolved in flexor tendon surgery since Bunnell’s original description?
Originally described in 1918 by Bunnell as a zone where ‘no man should attempt repair,’ Zone II repairs are now commonplace with excellent outcomes. Advances include:
1) Multi-strand core suture techniques;
2) Improved understanding of tendon healing biology;
3) Sophisticated pulley management;
4) Early controlled mobilization protocols;
5) Wide-awake surgery allowing intraoperative testing;
6) Refined epitendinous repairs;
7) Better understanding of biomechanical principles.
What specific challenges does a Zone IIc (beneath A2 pulley) flexor tendon injury present and how are they best addressed?
Challenges include:
1) Narrowest portion of the sheath;
2) Critical A2 pulley for finger function;
3) Limited surgical access;
4) High friction environment for repair.
Address by:
1) Partial venting of the A2 pulley (within 2cm);
2) Consideration of FDP-only repair.
What recent advances in biological augmentation show promise for improving flexor tendon healing?
Promising advances include:
1) Adipose-derived stromal cells (ASCs) with BMP-12 accelerating healing while suppressing inflammation;
2) Growth factors (bFGF, GDF-5, CTGF) delivered via porous or nanoparticle-coated sutures;
3) Muscle-derived stem cells (MDSCs) showing superior outcomes to bone marrow stem cells;
4) Low-dose 5-fluorouracil in gelatin slow-release systems reducing adhesions;
5) Platelet-rich plasma with fibrin matrix potentially increasing load to failure.
What is the significance of the vincula system in flexor tendon injuries and repair?
The vincula system:
1) Provides critical blood supply to intrasynovial tendons through ladder vessels from proper digital arteries;
2) Prevents proximal retraction of lacerated tendons;
3) Should be preserved during repair when possible to maintain vascular networks aiding healing;
4) Runs at the level of cruciform pulleys;
5) Damage correlates with poorer outcomes due to compromised nutrition and increased retraction.
What are the key steps in retrieving a proximally retracted FDP tendon in Zone I injuries?
Key steps include:
1) Locating tendon (often near Campers Chiasm or A1 pulley);
2) Using separate palmar incision if retracted to palm;
3) Using curved tendon passer or pediatric feeding tube through minimal incisions;
4) Tang’s technique of pushing the retracted tendon forward with forceps from a palmar incision;
5) Temporarily securing with 25-gauge hypodermic needle;
6) Ensuring proper orientation before repair.
How do the biomechanical properties of looped versus single-strand sutures differ in flexor tendon repair?
Calfee’s study showed:
1) 3-0 single-stranded repairs were substantially stronger than looped suture repairs;
2) Looped sutures failed primarily by tendon pullout, while single-stranded sutures failed by suture breakage;
3) Looped sutures have less tendon-suture interface;
4) Single-stranded sutures require more tendon handling;
5) Looped sutures allow faster repair construction. Clinical considerations include balance between strength and surgical efficiency.
What are the specific indications and techniques for pulley reconstruction during flexor tendon repair?
Indications include:
1) Significant bowstringing;
2) Multiple pulley injuries;
3) A2 or A4 pulley disruption with inadequate remaining pulleys.
Techniques include:
1) Extensor retinaculum graft (90% good/excellent outcomes);
2) FDS slip reconstruction;
3) Intrasynovial tendon grafts (superior gliding characteristics);
4) Palmaris longus graft.
Reconstruction should maintain the anatomic position of the original pulley to optimize biomechanics.
What are the epidemiological patterns and risk factors for reoperation after flexor tendon repair?
Dy’s study found:
1) 6% overall reoperation rate, with 91% performed in first year;
2) Higher risk in older patients;
3) Greater likelihood in workers’ compensation cases;
4) 26% lower risk with concomitant nerve repairs;
5) Most common causes: rupture (4%), adhesions (4%), infections, and contractures;
6) Modern techniques show reduced rupture and adhesion rates with strong repairs and early active motion protocols.
