FLEXOR TENDON INJURIES Flashcards
2 main reasons why Zone 2 flexor tendon injuries (no mans land) are difficult to manage
- Relative avascularity of tendons over proximal phalanx
2. Complexity of repair due to pulleys
Anatomy of FDS and FDP origin
FDS: - 4 tendons arising from separate muscle bellies = act independently - innervation by ulnar nerve - LF FDS absent in 20% of population FDP - 4 tendons arising from common muscle belly = subject to quadrigia effect - IF FDP separates early - dual inneration = AIN and ulnar nerve
Anatomy of Camper’s chiasm
- FDS splits into 2 slips over proximal phalanx
- FDP passes between slips to lie superficial to FDS
- Slips of FDS spiral around and under FDP to attach to base of middle phalanx
Blood supply to flexor tendons
- Proximally = muscle belly
- Distally = periosteal vessels at insertion
- Palm = longitudinal vessels
- Within the flexor sheaths
- long vincula
- nutrition via diffusion from synovial fluid = imbibition
Dorsal 1/2 of flexor tendon has better blood supply than volar 1/2
Vinculae of flexor tendons
- FDS = long and short vincular over proximal phalanx
- FDP = long and short vinculae over middle phalanx
- long vincula = vascular
- short vincula = attaches to joint capsule and pulls tendon out of joint during finger flexion
Tenodesis effect
- Used to assess tendon continuity
- Passive wrist flexion should cause fingers to extend
- Passive wrist extension should cause fingers to flex
- Negative tenodesis effect = tendon disruption
Composition of tendons
Predominantly Type I collagen = forms 80% of dry weight
High water content = forms 60% wet weight
2 mechanisms for tendon healing
Intrinsic vs. extrinsic: 1. Intrinsic healing = desirable - via tenocytes within tendon - occurs with early controlled motion 2. Extrinsic healing = not desirable - involves scar formation - occurs with prolonged immobilisation Intrinsic healing associated with: 1. Fewer adhesions = better excursion and ROM 2. Better strength of repair = load to failure double 3. Better functional outcomes
3 phases of tendon healing
- Inflammatory = 1 wk
- tendon weak - Fibroblastic/ proliferative = 1-4 wks
- disorganised collagen - Remodelling > 4 wks
- organised collagen along long axis of tendon due to tensile stress at repair site
Tendon unlikely to return to original mechanical properties/ strength
5 zones of flexor tendon injury
- Zone 1 = distal to FDS insertion
- Jersey finger - Zone 2 (no mans land) = proximal A1 pulley to FDS insertion
- historically poor prognosis - Zone 3 (palm) = distal carpal tunnel to proximal A1 pulley
- may be associated with NV injury
- outcomes worse with NV injury - Zone 4 = carpal tunnel
- risk of postoperative adhesions
- transverse carpal ligament can be repaired in lengthened fashion to prevent bowstringing - Zone 5 = proximal to carpal tunnel
- may be associated with NV injury
- outcomes worse with NV injury
Indications for nonoperative management of flexor tendon injuries
Closed partial ruptures involving < 60% tendon width
- direct repair of partial ruptures requires epitendinous sutures only (studies show no need for core sutures)
6 main principles of tendon repair
- Smooth tendon ends
- Placement of sutures on tension side of tendon
- dorsal side for flexor and extensor tendons - Secure knots
- Minimal gapping
- locking loops and epitendinous sutures minimise gap formation
- gap > 3mm = increased risk of repair failure - Preservation of blood supply
- Sufficient repair strength to allow early controlled motion
Tendon repair failure
- Most common in first 2 wks = inflammatory and proliferative phases
- Most common at knot
- Gapping is 1st step in repair failure
2 layers of flexor tendon repair
- 4-strand core suture with 3.0 or 4.0 nonabsorbable braided material like Ethibond or Ticron
- Continuous/ running epitendinous suture with 6.0 nonabsorbable monofilament material like Proline
- continuous suture decreases tendon CSA and improves gliding
- epitendinous suture increases repair strength by 20%
- epitendinous suture minimises gap formation
Optimal core strands for flexor tendon repair
- Direct correlation between repair strength and number of core sutures crossing repair site
- Optimal is 4-strand core suture
- 6 and 8-strand core sutures are stronger but they devascularise tendon due to too much suture material
4 main options to improve tendon gliding
- Debulk tendon
- Repair only 1 slip of FDS
- Repair only FDP and don’t repair FDS
- Pulley venting
- studies show up to 25% of A2 pulley and 100% of A4 pulley can be released down 1 side without bowstringing
Postoperative rehabilitation of flexor tendon repair
- Early controlled motion with dynamic splinting
- Kleinert protocol = active extension and passive flexion
2 indications for extended immobilisation post flexor tendon repair
- Children
2. Non-compliant patients
4 indications for tendon reconstruction
- Failure of repair
- Acute segmental rupture
- Delayed diagnosis > 3 wks = tendon retraction and scarring
- Inadequate tendon post tenolysis
5 prerequisites for tendon reconstruction
- Supple skin
- Sensate digit
- Adequate vascularity
- Healthy bed
- Supple joints
2-stage tendon reconstruction technique
Stage 1 - insertion of silicone tendon rod - anchored distally - early ROM to allow formation of pseudosheath Stage 2 - performed 3-4 mo after Stage 1 - removal of tendon rod and insertion of tendon graft - Pulvertaft weave proximally
Indication for tendon transfer
Chronic ruptures where muscle is too contracted or nonfunctional
Indication for tenolysis
- Normal passive ROM but severely restricted active ROM due to adhesions
- Trial aggressive therapy first
Complications with flexor tendon repair
- Wound problems and infection
- Adhesions (most common) = decreased excursion and ROM
- Joint stiffness
- Re-rupture = re-rupture rate 20%
- Weakness
- Deformity
- swan neck deformity
- trigger digit
- quadrigia effect
