ASHT - extensor tendon injuries Flashcards
How are extensor tendons different from flexor tendons? (5)
- Anatomy more complex
- tendons are flatter, more superficial, largely extra-synovial
- can rapidly adhere to underlying bones and joints
- often heal with a lag secondary to adheisions
- weaker than digital flexors
What nerves innervate digital extension?
extrinsics - radial n. innervated, intrinsics - median and ulnar n. innervated
where do EIP and EDM lie relative to EDC?
on the ulnar side of EDC
What is in 6 extensor compartments?
- APL/EPB
- ECRL/ECRB
- EPL
- EDC/EIP
- EDM
- ECU
extensor tendon zones?
ODD over joint
1. DIP
2. P2
3. PIP
4. P1
5. MPJ
6. metacarpals
7. extensor retinaculum
8. distal forearm
9. musculotendinous junction (also PIN injury?)
ORL tightness test
compare DIP flexion with PIP in fulll extension vs. flexed. + if DIP flexion is LESS when PIP extended (?active or passive?)
How does extension occur at Zone 1 DIP
combined action of EDC, lateral bands, and tenodesis or ORL. Collateral ligaments relax from flexed position, PIP extension initiated by EDC>tension on ORL then lateral bands rise dorsally and reach same tension at central extensor tendon
where is triangular ligament located?
Zone 2 - over the middle phalanx P2
where is transverse retinacular ligament? (TRL)
Zone 3 - PIP level. extends from lateral bands to flexor tendon pulley encompassing PIP joint laterally
what structures are in extensor zone 4?
P1: interossei, lateral bands
what makes up the dorsal hood?
fibers from the central slip, interossei, and lateral bands. action: extends MP joint. prone to scar adherence bc inelastic.
what structures are in extensor zone 5?
dorsal hood, sagittal bands
Sagital Bands injury
disrupts stability of the extensor tendons during flexon and bowstringing during extension - snapping or jumping
Mallet injury treatment
- prevent swan neck deformity.
6 weeks splint + 6 weeks remobilization,
PIP mobilization day 1.
if swan neck develops splint PIP in 30 degrees flexion.
Gradually increase flexion starting at 20* then increase 10* each week if no extension lag.
What causes Boutonniere deformity?
- central slip rupture
- triangular ligament rupture
- PIP synovitis (weakens lateral bands). Lateral bands slide volar
Can be 3 weeks until migration becomes apparent
Elson’s test
With PIP fully flexed and held in position pt is asked to extend fingertip (DIP). If central slip intact the lateral bands will be slack and it won’t extend. POSITIVE = DIP extension
Boutonniere vs. pseudo-boutonniere
Boutonniere: DIP hyperextension observable, significant ORL tightness
Pseudo-boutonniere: DIP joint passively flexible, often from PIP hyperextension injury, PIP flexion contracture, no injury to central slip, negative ORL test. Treat - flexion contracture
Swan neck deformity causes (4)
- terminal tendon rupture
- PIP hyperextension from lax volar capsule 2* synovitis or rupture of volar plate
- FDS rupture (loss of dynamic PIP stabilization)
- intrinsic tightness 2* MP pathology
Sagittal Band Rupture
- the sagittal bands prevent bowstringing of the EDC during extension, and centralize EDC at midline during flexion. Rupture is usually atraumatic and involving radial fibers (ulnar subluxation more likely). Can cause EDC to sublux ulnarly and cause incomplete extension. Treatment: immobilize MP at neutral (injured + adjacent) vs. RMO/RME 6-8 weeks in 15-20* relative extension
How much extensor tendon glide do you need to prevent adhesions?
5mm
Summary of Digital Extensor Rehab
- Zone 1-2 needs immobilization >=6 weeks
- all other zones may have better outcomes with early controlled AROM
- Injuries involving fractures, crush, or other shoft tissue involvement need early controllled AROM to decrease 2* complications
- Allowing 2-3 days before therapy minimizes inflammatory response
