Nerve and Tendon Injuries

Question 1

How are tendons arranged macroscopically?

Answer 1

Components

• Muscle origin (from bone)
• Muscle belly
• Musculotendinous junction
• Tendon ± Sesamoid bone (e.g. patella) ± Tendon sheath

Question 2

What are the different macroscopic layers found in tendons?

Answer 2

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

Question 3

Why is movement so important for tendon health?

Answer 3

Immobility reduces

• Water content
• Glycosaminoglycan concentration and strength

Weakens tendon!!!

Question 4

Can give some examples of types of tendon injuries?

Answer 4

• 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

Question 5

What is an apophysis?

Answer 5

A layer of bone over a growth plate; an area of structural weakness in a growing child or adolescent

Question 6

What is traction apophysitis?

Answer 6

Powerful Tendons attaching to apophyses can cause chronic traction injuries. Once growth plates fuse, the problem will disappear

Question 7

How do tendons heal?

Answer 7

• 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

Question 8

What are the basic principles of tendon rehabilitation?

Answer 8

• Early movement (stress) - increases healing & strength, & reduces adhesions
  
  • Active
  • Passive

Question 9

What are the different layers within the macrostructure of nerves?

Answer 9

• Endoneurium - covers AXONS
• Perineurium - covers FASCICLES (nerve bundles)
• Epineurium - covers NERVE
• Myelin sheath - surrounds neuron (Schwann cell, oligodendrocyte)

Question 10

What type of nerve injuries can occur?

Answer 10

• Neurapraxia
• Axonotmesis
• Neurotmesis

Question 11

What is neurapraxia?

Answer 11

• 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

Question 12

What is Axonotmesis?

Answer 12

• “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

Question 13

What is neurotmesis?

Answer 13

• 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

Question 14

What is dysasthesia?

Answer 14

Disordered sensation

• Anaesthetic (numb)
• Hypo- & hyper-aesthetic
• Paraesthetic (pins & needles)

Question 15

What is paresis?

Answer 15

Muscular weakness

Question 16

How do nerves heal?

Answer 16

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

Question 17

What is wallerian degeneration?

Answer 17

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.

Question 18

How does achilles tendon rupture occur?

Answer 18

• Pushing off with weightbearing forefoot whilst extending knee joint
• Unexpected dorsiflexion of ankle
• Violent dorsiflexion of plantarflexed foot

Question 19

Who is more at risk of Achilles tendon rupture?

Answer 19

• Males
• 30-40yrs old

Question 20

How does achilles tendon rupture present?

Answer 20

• 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

Question 21

How would you investigate suspected achilles tendon rupture?

Answer 21

Clinical Diagnosis - simmond’s test

Imaging

• MRI
• X-ray - check for fractures if suspected?

Question 22

How would you manage someone with a ruptured achilles tendon?

Answer 22

Acute referral to orthopaedics

Conservative

• PoP cast in equinus position - 10 wks

Operative

• Open repair + earlier mobilisation - Re-rupture rate lower

Question 23

What is a vinculum?

Answer 23

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

Question 24

Risk factors for achilles tendon rupture

Answer 24

• quinolone use (e.g. ciprofloxacin) is associated with tendon disorders
• hypercholesterolaemia (predisposes to tendon xanthomata)