Musculoskeletal Growth and Repair: Bones and Tendons Flashcards
What are the components of the muscle/tendon unit?
- Muscle origin (from bone)
- Muscle belly
- Musculotendinous junction
- Tendon
- +/- sesamoid bone
- +/- tendon sheath
- Tendinous insertion (into bone - Sharpey’s fibres)
Describe the structure of tendons
- Longitudinal arrangement of cells
- Mostly tenocytesand fibres (collagen type 1 - triple helix)
- Fascicles of long narrow spiralling collagen bundles
- Collagen bundles are covered by endotenon, fascicles are covered by paratenon and the tendon is covered by the epitenon
How do tendons get their blood supply?
The viniculum branches into a fine network of blood vessels in the paratenon
What are the features of a tendon sheath?
- Tendons connected to sheath by vincula
- Synovial lining + fluid (gliding lubrication and nutrition)
- E.g. flexor tendons in distal palm and fingers
What is the function of the tendon sheath?
Flexibility and strength in tension
How can tendons be injured/
Degeneration, inflammation, enthesiopathy, traction apophysitis, avulsion +/- bone fragment, tear - intrasubstance, tear - musculotendinous junction, laceration/incision, crush/ischaemia/attrition and nodules
Describe the features of Achilles tendon degeneration
- Intrasubstance mucoid degeneration
- Swollen, painful, tender
- May be asymptomatic
- ?Precursor to rupture
Describe the features of de Quervain’s stenosing tenovaginitis
- Inflammation of EPB + APL tendons passing through the common tendon sheath at the radial aspect of the wrist
- Swollen, tender, hot and red
- Positive Finklestein’s test
Describe the features of enthesiopathy
- Inflammation at insertion to bone
- Muscle/tendon: usually at muscle origin rather than tendon insertion e.g. lateral humeral epicondylitis
- Ligament: Plantar fascilitis
Describe the features of traction apophysitis e.g. Osgood Schlatter’s disease
- Insertion of patellar tendon into the anterior tibial tuberosity
- Adolescent active boys
- Recurrent load
- Inflammation
Describe the features of avulsion +/- bone fragment
- Failure at insertion
- Load exceeding failure of strength while muscle is contracting
- Mallet finger
- Insertion of extensor tendon into dorsum of base of distal phalanx of the finger
- Forced flexion of extended finger
What are the management options for avulsion?
- Conservative: limited application and retraction of tendon
- Operative: reattachment of tendon (through bone) and fixation of bone and ligament
What is an intrasubstance rupture?
When load exceeds failure strength e.g. Achilles tendon rupture
Which clinical features would suggest an Achilles tendon rupture?
- Positive “Simmond’s” (squeeze) test
- Palpable tender gap
Give an example of a musculotendinous junction tear
Medial head of gastrocnemius at musculotendinous junction with Achilles tendon
What are the management options for a tendon rupture?
- Conservative: mobilise or splint/cast (where ends can be opposed)
- Operative: high risk rupture, high activity and ends cannot be opposed
What are the features of a tendon laceration?
- Males>females
- Young adults
- Need repaired surgically
- e.g. finger flexors (FDS) and FDP
What are the features of cortical bone?
- Diaphysis
- Resists bending and torsion
- Laid down circumferentially
- Less biologically active
What are the features of cancellous bone?
- Metaphysis
- Resists/absorbs compression
- Site of longitudinal growth (physis)
- Very biologically active
Why do bones fail?
- High energy transfer in normal bones
- Repetitive stress in normal bones (stress fracture)
- Low energy transfer in abnormal bones (osteoporosis, osteomalacia, metaastatic tumour and other bone disorders)
Describe the components of stage 1 in fracture healing
- Inflammation
- Begins immediately after fracture
- Haematoma and fibrin clot
- Platelets, PMNs, neutrophils, monocytes and macrophages
- Byproducts of cell death - lysosomal enzymes
- Fibroblasts
- Mesenchymal and osteoprogenitor cells (transformed endothelial cells from medullary canal and/or periosteum)
- Angiogenesis
How can we manage stage 1 of a fracture?
- NSAIDs
- Loss of haematoma: open fractures and surgery
Name the platelet concentrates
- Platelet derived growth factor
- Transforming growth factor-beta
- Insulin like growth factor
- Vascular endothelial growth factor
Describe the features of stage 2 in fractures
- Soft callus
- Begins when pain and swelling subside
- Lasts until bony fragments are united by cartilage or fibrous tissue
- Some stability of fracture
- Angulation can still occur
- Continued increase in vascularity
Which kind of bone graft is the best?
Autogenous cancellous bone graft
Describe the features of stage 3 in fractures
- Hard callus
- Conversion of cartilage to woven bone
- Long bone fracture: endochondral and membranous bone formation
- Increasing rigidity: secondary bone healing and obvious callus
What are the features of stage four of fractures?
- Conversion of woven bone to lamellar bone
- Medullary canal is reconstituted
- Bone responds to loading characteristics
What are the causes of delayed union?
High energy injury, distraction, instability, infection, steroids, immune suppressants, smoking, warfarin, NSAIDs and ciprofloxacin
What are the features of non union?
- Failure to heal
- Failure of calcification of fibrocartilage
- Instability
- Abundant callus formation
- Pain + tenderness
- Persistent fracture line
- Sclerosis
What are the management options for delayed healing?
- Different fixation
- Dynamisation
- Bone grafting
