Nerve and Tendon Injuries Flashcards
How are tendons arranged macroscopically?
Components
- Muscle origin (from bone)
- Muscle belly
- Musculotendinous junction
- Tendon ± Sesamoid bone (e.g. patella) ± Tendon sheath
What are the different macroscopic layers found in tendons?
Fascicles of long spiralling collagen bundles
- Endotenon - cover COLLAGEN BUNDLES
- Epitenon - cover TENDON
- Paratenon - fills space between tendon and its sheath
-
Tendon sheath - Connected to tendon by vincula
- Synovial lining + fluid - allows gliding lubrication and nutrition
Why is movement so important for tendon health?
Immobility reduces
- Water content
- Glycosaminoglycan concentration and strength
Weakens tendon!!!
Can give some examples of types of tendon injuries?
- Degenerative - e.g Achilles tendon
- Inflammatory - e.g. De Quervan’s Tenosynovitis
- Enthesiopathy - e.g. Tennis elbow
- Traction apophysitis - e.g. Osgood Schlatter’s disease
- Avulsion +/- bone fragment - e.g. mallet finger
- Tear - Intrasubstance (Achilles), musculotendinous junction (plantaris syndrome)
- Laceration/Incision
- Crush/Ischaemia
- Nodules - e.g. trigger finger
What is an apophysis?
A layer of bone over a growth plate; an area of structural weakness in a growing child or adolescent
What is traction apophysitis?
Powerful Tendons attaching to apophyses can cause chronic traction injuries. Once growth plates fuse, the problem will disappear
How do tendons heal?
- Initiated by fibroblasts (from epitenon) and macrophages
- 3 phases - inflammatory, fibroblastic (collagen-producing), remodelling
- Weakest - 7-10 days
- Most of original strength - 3-4 weeks
- Max Strenght - 6 months
What are the basic principles of tendon rehabilitation?
-
Early movement (stress) - increases healing & strength, & reduces adhesions
- Active
- Passive
What are the different layers within the macrostructure of nerves?
- Endoneurium - covers AXONS
- Perineurium - covers FASCICLES (nerve bundles)
- Epineurium - covers NERVE
- Myelin sheath - surrounds neuron (Schwann cell, oligodendrocyte)
What type of nerve injuries can occur?
- Neurapraxia
- Axonotmesis
- Neurotmesis
What is neurapraxia?
- Reversible conduction loss
- “Nerve in Continuity” - Axon remains intact, but myelin has been damaged
- Often caused by local ischaemia and demyelination - e.g. compression
- Prognosis good - weeks or months
What is Axonotmesis?
- “Tube in Continuity” - Epineurium intact but disruption of axon continuity
- Caused by stretching, crush or direct blow
- Wallerian degeneration - follows injury; part of the axon separated from the neuron’s cell body degenerates distal to the injury - occurs with nerve fibre crush or cut
- Fair Prognosis - sensory recovery>motor recovery
What is neurotmesis?
- Complete nerve division
- Caused by Laceration or avulsion
- Endoneurial tubes disrupted - no guidance for nerves to repair, unlike axonotmesis
- Prognosis poor - no recovery unless surgically repaired
What is dysasthesia?
Disordered sensation
- Anaesthetic (numb)
- Hypo- & hyper-aesthetic
- Paraesthetic (pins & needles)
What is paresis?
Muscular weakness
How do nerves heal?
Very Slow
- Proximal axonal budding occurs - after about 1 month delay
- Regeneration - 1 mm/day or 1 inch/month
- Pain returns first
-
Prognosis depends whether nerve is
- Pure - only sensory or only motor
- Mixed - both sensory and motor within same nerve
- Distal/Proximal - proximal worse
What is wallerian degeneration?
A process that results when a nerve fiber is cut or crushed, in which the part of the axon separated from the neuron’s cell body degenerates distal to the injury.
How does achilles tendon rupture occur?
- Pushing off with weightbearing forefoot whilst extending knee joint
- Unexpected dorsiflexion of ankle
- Violent dorsiflexion of plantarflexed foot
Who is more at risk of Achilles tendon rupture?
- Males
- 30-40yrs old
How does achilles tendon rupture present?
- Sudden Pain + Popping Sound - in achilles area - feel like they’ve been hit in the heel
- Palpable tender gap - particularly in first 24 hrs
- Unable to heel raise
- Positive Simmonds Test
How would you investigate suspected achilles tendon rupture?
Clinical Diagnosis - simmond’s test
Imaging
- MRI
- X-ray - check for fractures if suspected?
How would you manage someone with a ruptured achilles tendon?
Acute referral to orthopaedics
Conservative
- PoP cast in equinus position - 10 wks
Operative
- Open repair + earlier mobilisation - Re-rupture rate lower
What is a vinculum?
Band of connective tissue, similar to a ligament, that connect a flexor tendon to a phalanx bone. They contain tiny vessels which supply blood to the tendon
Risk factors for achilles tendon rupture
- quinolone use (e.g. ciprofloxacin) is associated with tendon disorders
- hypercholesterolaemia (predisposes to tendon xanthomata)
