Musculoskeletal Growth/Injury and Repair - Bone and Tendon Flashcards
What are ligaments?
•Dense bands of collagenous tissue - often condensations of joint capsules
What do ligaments span and where are they anchored?
- Span a joint
* Anchored to the bone at either end
What is the function of ligaments?
Maintain joint stability through a range of motion
How do ligaments allow a range of stable movements?
- Different portions of ligaments tensions at different joint positions
- Multiple ligaments over a joint
Describe the structure of a ligament
- They are made from collagen fibres (type 1)
- They contain fibroblasts
- They have sensory fibres - proprioception, stretch and sensory
- They have vessels on the surface - they can bruise
- They are crimped to allow stretch
What are the difference between tendons and ligaments?
•COMPOSITION •Ligaments have: -lower percentage of collagen -higher percentage of water and proteoglycans -less organised than collagen fibres -rounder fibroblasts
Why do ligament ruptures occur?
•Forces exceed the strength of the ligament - can be expected, unexpected, rate of load
What 2 kinds of ligament rupture can occur?
- Complete - exceed strength of ligament
* Incomplete - partially exceed strength of ligament
What can be the outcome of ligament rupture?
- Loss of joint stability
* Loss of proprioception
What are the 3 phases of ligament healing?
- Haemorrhage
- Proliferative phase
- Remodelling
Describe the haemorrhage phase
- Blood clot
- Reabsorbed
- Replaced with heavy cellular infiltrate
- Hypertrophic vascular response
Describe the proliferative phase
- Production of scar tissue
* Disorganised collagenous connective tissue
Describe the remodelling phase
- Matrix becomes more ligament-like
* Major differences in composition, architecture and function persist
Why might a ligament rupture treated conservatively (non-operatively)?
- Partial rupture
- No instability
- Poor candidate for surgery
Why might a ligament rupture treated operatively?
- Instability
- Expectation - sportsmen
- Compulsory - multiple
What operative procedures are available for tendon repair?
- Open repair
- Augmentation - with tapes
- Replacement - can be done with tendon
How are muscles and tendons connected?
Muscle origin (from bone) ->muscle belly -> musculotendinous junction -> tendon (with tendinous sheath) -> tendinous insertion (with Sharpey’s fibres)
What may a tendon have within it?
A sesamoid bone e.g. the patella
Describe the structure of a tendon
- Longitudinal arrangement of cells and fibres
- Collagen bundles covered by ENDOTENON
- Fascicles covered by PARATENON
- Tendon covered by EPITENON
What are the types of cells and fibres present in tendons?
- Cells - mostly tenocytes
* Fibres - collagen type 1 (triple helix)
Describe the blood supply to tendons?
- Doesn’t run down the length of tendon like in bone
* Blood comes through vincula and the paratenon
How are tendons connected to their sheath?
By vincula
How do the tendon sheath maintain lubrication and nutrition?
•Synovial lining and fluid production
What is the function of tendons?
To pull on bones to bend joints and provide propulsion
What happens if tendons are immobile for a length of time?
•Reduction in water content and glycosaminoglycan concentration and strength
How might tendons become injured?
- Degenerations
- Inflammation
- Enthesiopathy - issues around where tendons fix into bones
- Traction apophysitis - in children
- Avulsion ± bone fragment
- Tear - intrasubstance (rupture)
- Tear - musculotendinous junction
- Laceration/incision
How would Achilles tendon degeneration present?
- Intrasubstance mucoid degeneration
- May be swollen, painful or asymptomatic
- Sometimes precursor to rupture
- Rheumatoid arthritis considered elsewhere
How might inflammation of a tendon (de Quervain’s stenosing tenovaginitis) present?
- Tendons of EPB + APL passing through common tendon sheath at radial aspect of wrist
- Swollen, tender, hot, red
- Positive Finklestein’s test
What is enthesiopathy?
- Inflammation at insertion to bone
- Muscle or tendon - usually at muscle origin rather than tendon insertion (tennis elbow)
- possible t get enthesiopathies in ligaments - plantar fasciitis
What is Osgood Schlatter’s disease?
•Type of traction apophysitis (injury)
•Insertion of patellar tendon into anterior tibial tuberosity
•Adolescent active boys
•Recurrent load
•Inflammation
Apophysitis - inflammation or stress injury to area around growth plates
What is avulsion ± bone fragment?
- Pulling off of tendons
- Load exceeds failure strength while the muscle is contracting
- Mallet finger - forced flexion in an extended finger
What is the treatment of avulsion?
- Depends on tendon and site
- Conservative - limited application (can be done in finger) as tendon likely to have retracted
- Operative - reattach tendon (through bone) and fixation of bone fragment
What is an intrasubstance rupture?
- E.g. Achilles tendon tear
* Loads exceeds failure strength
How might the Achilles tendon become ruptured?
- Pushing off with weight bearing forefoot whilst extending knee joint (53%) - sprints starts
- Unexpected dorsiflexion of ankle (17%) - slipping into hole
- Violent dorsiflexion of plantar flexed foot (10%) - fall from height
How does a ruptured Achilles tendon present clinically?
- Positive Simmond’s (squeeze) test - squeeze calf muscle causing plantar flex
- Palpable tender gap
How are musculotendinous junction tears treated?
Conservatively as most are partial tears
When is conservative treatment used for a tendon rupture?
- When ends can be opposed
- Mobilise (partial rupture)
- Splint/cast
When is operative treatment used for a tendon rupture?
- High risk rerupture
- High activity
- End cannot be opposed
How are tendon lacerations treated?
Surgically and early due to issues with retraction
How do bones grow?
BONE GROWTH
Describe cortical bone
- Main component of diaphysis
- Resists bending and torsion
- Laid down circumferentially
- Less biologically active
Describe cancellous bone
- Lies in metaphysis
- Resists/absorbs compression
- Site of longitudinal growth (physis)
- Very biologically active
What is a fracture?
- Break in the structural continuity of bone
* Crack, break, split crumpling, buckle
Why do bones fail?
- Normal bone - high energy transfer
- Normal bobe - repetitive stress (stress fracture) e.g. runners
- Osteoporosis, osteomalacia, metastatic tumour, other bone disorders - low energy transfer
How do fractures affect bone?
Disrupts blood supply
How well do bones repair?
Heal without scar in four stages
Describe the 1st stage of bone repair
INFLAMMATION
•Begins immediately after fracture
•Haematoma and fibrin clot released
•Platelets, PMNs, neutrophils, monocytes and macrophages are released
•By products of cell death - lysosomal enzymes which create soup designed to bring in new cells to initiate repair
•Angiogenesis
What cells move in to help repair in stage 1 of repair?
•Fibroblast
•Mesencymal and osteoprogenitor cells
- transformed endothelial cells from medullary canal and/or periosteum
-osteogenic induction of cels from muscle and soft tissue
How does angiogenesis occur in stage 1 of bone repair?
- Low levels of oxygen inside the bone drive angiogenesis
* Macrophages produce angiogenic factors under hypoxic conditions
How can stage 1 of repair be aided?
- NSAIDs
* Maintain haematoma
How can platelet concentrates be used to aid repair?
- Patients blood used for platelet therapy in order to replace the blood clot
- Platelet-derived growth factor (PDGF)
- Transforming growth factor-beta (TGF-B)
- Insulin like growth factor (IGF)
- Vascular endothelial growth factor (VEGF)
Describe the 2nd stage of bone repair
SOFT CALLUS •Begins when pain and swelling subside •Last until bony fragments are united by cartilage or fibrous tissue •Some stability of fracture •Angulation can still occur (bend) •Continued increase in vascularity
How can stage 2 be affected by us?
- Replace cartilage using demineralised bone matriculates (DBM)
- Skip soft callus stage and go straight to bone graft or bone substitutes
What is autogenous (same person) cancellous bone graft?
- Gold standard
- Osteoconductive - allows cells to grow in from either end
- Osteoinductive
What is allograft?
Tissue donation (cortical and cancellous bone)
How effective is allograft?
- It is osteoconductive but not osteoinductive
* Risk of disease transmission
Describe the 3rd stage of bone repair
•Conversion of cartilage to woven bone (as movement is limited) •In a typical long bone -endochondral bone formation -membranous bone formation •
Describe the 4th stage of bone repair
- Conversion of woven bone to lamellar bone (in adults always some swelling or change in the bone)
- Medullary canal is reconstituted
- Bone responds to loading characteristic Wolff’s Law
What is strain?
- Degree of instability is best expressed as magnitude of strain
- If strain is too low, mechanical induction of tissue differentiation fails
- Too high and healing process does not progress to bone formation
What is delayed union?
Failure to heal in expected time
What are some causes of delayed union?
- High energy injury
- Distraction
- Instability
- Infection
- Steroids
- NSAIDs
- Immune suppressants
- Smoking
- Warfarin
- Ciprofloxacin
What is done wen fractures aren’t healing?
- Consider alternative management
- Different fixation
- Bone grafting
- Dynamisation - removal of screws
What is non-union?
Failure to heal
How does non-union occur?
- Failure of calcification of fibrocartilage
- Instability - excessive osteoclasis
- Abundant callus formation - multiple bony masses
What are the signs of non-union?
- Pain and tenderness
- Persistent fracture line
- Sclerosis
