Flexor Tendon Injuries

• Applied Anatomy & Examination

• Tendon Healing

• Management

Flexor Tendon Injuries

Applied Anatomy

Anatomy

• Musculotendinous units

• Synovial sheaths & Fibrosseous canals

• Pulleys

• Vascular supply

• Zones

Tendon Structure

• Composite material consisting of collagen fibrils embedded in a matrix of proteoglycans– Type I collagen (95%)– Type III and IV collagen (5%)

• Tenocytes are arranged in parallel rows between bundles

Tendon Structure

Tendon Structure

• Endotenon circumscribes each fascicle – Permits fascicular gliding

• Epitenon surrounds the tendon– Contains capillary blood supply

Tendon Structure

Epitenon

Endotenon

Paratenon

Tendon Structure

• Paratenon is the adventitia that covers the flexor tendon in the palm– Consists of visceral & parietal layer– Continuous with synovial mesotenon – Supplies tendon nutrients– Allows tendon gliding

Applied Anatomy

• FDS

• FDP

• FPL

• N & V

FDS

FDP

FPLFDP

Verdan Zones

Zone 5

Zone 5/4

Zone 4

Zone 3

Zone 1/2

Zone 2 – Campers Chiasma

Tendon Nutrition

Nutrient Supply

• Dual Source via Perfusion and DiffusionA. Perfusion from blood supplied by longitudinal

vessels as well as the vincula system.

B. Diffusion within the sheath is via synovial fluid.

• Diffusion is more important within the digital sheath. (Lundborg 1978, 1980)

Vascular Supply

Synovial Sheaths

Digital Sheaths

• Analogous to paratenon – Visceral layer surrounds

tendons

– Parietal layer contains thickenings that comprise the flexor sheath and pulley system

– Contains synovial fluid

Pulleys

Pulleys- A2 & A4

Biomechanics

• Moment arm-pulleys– Loss of pulleys increase

excursion necessary for desired flexion

Strickland OCNA 1983

Biomechanics

• Forces generated during tendon function– Passive flexion 2-4 N– Active with mild resistance 10N– Active with moderate resistance 17N– Strong grasp 70N– Tip pinch 120N– Power grip 200N

– (FDS 30% < FDP, loads increased by edema/scar)

Schiund et al JHS 1992

Biomechanics

• 9 cm of tendon excursion is required for composite wrist & digital flexion– 2.5 cm for full digital flexion with wrist

stabilized

• Tendon excursion and joint rotation are controlled by pulley system

Summary

• Intrasynovial flexor tendon repair- leave sheath intact

• Preservation of A2 & A4 pulleys

• Digital arterial ladder branch is identified and preserved

Summary

• Thick skin flaps retracted with sutures

• Create windows in the membranous portion of the

flexor tendon sheath

• Blind passage of instruments into the tendon sheath should be avoided

Management of Flexor tendon Lacerations

• History

• Physical Examination

• Surgical Repair

• Rehabilitation

Examination

• Colour, Capillary Refill, Temperature

• Compare to non-injured hand

Circulation

Nerves - Sensory

Diagnosis of Flexor Injury

• Posture of Hand/ Normal cascade

• Passive tenodesis test

• Forearm compression test

• Independent testing of FDS & FDP

• Partial damage

Normal Flexion Cascade

Flexor Tendon Testing

FPL