Collagen and bone Flashcards
Osteogenesis Imperfecta Osteopetrosis
1
Q
What is osteogenesis imperfecta?
A
- A hereditary condition resulting from a DECREASE in the AMOUNT of Normal TYPE 1 COLLAGEN due to
- 1) DECREASE COLLAGEN SECRETION
- 2) PRODUCTION of ABNORMAL COLLAGEN
- leads to ** INSUFFICIENT OSTEOID PRODUCTION :(**
- Physeal osteoblasts can’t form sufficent osteoid
- Periosteal osteoblasts can’t form sufficient osteoid so CAN’T remodell normally
** nb type 1 and “I” in Imperfecta **
2
Q
What is the genetics of osteogenesis imperfecta?
A
- 90 % have gene mutation
- COL 1A1 and COL 1A2
- causes-> ABNORMAL collagen x linkage via a Glycine subsitution in the PROCOLLAGEN molecule
- Both Autosomal dominant and Autosomal Recessive
- can be severe or mild (tarda form)
3
Q
What are the orhtopaedic manifestations of osteogenesis imperfecta ?
A
-
Bone fragility and fracture
- Heal in normal fashion intially but does not remodel
- -Can lead to Progressive bowing
- Ligamentous laxity
- Short stature
- Scoliosis
- Codfish vertebra- compression fractures
- Basilar invagination( protrusion of the Odontoid process into the foramen magnum)-> apnea altered consciousness, ataxia
- Olecranon apophyseal avulsion fractions
4
Q
What other non-orthopaedic clinical manifestation occur ?
A
- Blue sclera
- Hearing loss
- Brownish opalescent teeth- dentinogenesis imperfecta
- Wormanian skull bones- puzzle piece intrasutural skull bones
- Increased risks of malignant hyperthermia
5
Q
What is the classification for osteogenesis imperfecta?
A
Originally by SILLENCE
- 4 Types but more added since
-
Type 1
- AUTOSOMAL DOMINANT
- Blue sclera
- mildest form
- presents at preschool age (tarda)
- Hearing effected 50%
- Divided into A or B if teeth involved
-
Type 2
- AUTOSOMAL RECESSIVE
- Blue sclera
- LETHAL :( in perinatal period
-
Type3
- Autosomal recessive
- NORMAL SCLERA
- fractures at birth
- Progressively Short sature
- Most severe survival form
-
Type 4
- Autosomal dominant
- NORMAL SCLERA
- Moderate severity
- Bowing bones and vertebral fractures common
- Hearing normal
- Divided A or B on teeth
- Type 5-7 added later, these have no type 1 collagen mutation but ABNORMAL BONE on microscopy
6
Q
What are the symptoms of osteogenesis imperfecta?
A
Mild cases
- Multiple fractures during childhood
Severe
- Fractures Present at birth - can be fatal
- No of fractures typically decreases as pt ages adn ussually stops after puberty
Basilar invagination
- presents with apnea,altered consciousness, ataxia and myelopathy
- usually in 3-4th decade of life, but can be as early as teenagers
7
Q
What are the signs of osteogenesis imperfecta?
A
- Multiple fractures leads to
- saber shin - appearamce of tibia
- Bowing of long bones
8
Q
What are the radiological findings?
A
- Thin cortices
- Generalised osteopenia
- Saber shins
- Skull radiographs reveal WORMIAN bones
9
Q
What is found on histology ?
A
- Increased HAVERSIAN canals and osteocytes lacunae
- Increased no of osteoblasts and osteoclasts
- Decrease no of trabeculae
- Decreased a cortical thickness
- Replicated cement lines
10
Q
What is diagnosis based on in osteogenesis imperfecta?
A
- Clinician findings, typical radiographs and fhx
- There is no commercial test due to variety of gene mutations
11
Q
How would you tx a pt with osteogenesis imperfecta with a fracture ?
A
Non op
-
Observation.
- if Child <2yrs tx as child without OI
Surgery
- Fixation with telescoping rodes
- if pt >2 years
- allow continued growth
12
Q
What could be done to prevent fractures in osteogenesis imperfecta?
A
- Bracing
- to decrease deformity and lessen fractures
-
BISPHOSPHONATES
- indicate in most Osteogensis imperfecta to reduce Fractures
- Function is to increase cortical thickness by inhibiting osteoclasts- chronic use = metaphyseal bands on X-ray
- Growth hormone
-
Bone marrow transplantation
- used with some succes
13
Q
How are long bone bowing deformities tx?
A
Operative
- Realignment OSTEOTOMY With rod fixation
- in severe deformity to reduce fracture rates
- Telescopic rod= Sheffield rod ,
- Non telescopic= Williams’s rods, rush rods
14
Q
When and how would you tx scoliosis in a pt with Osteogensis imperfecta ?
A
- If curve > 45 degrees Bracing is ineffective
Operative
- POSTERIOR SPINAL FUSION for curves **> 45o **in mild form or >35o degrees in severe
- Technique is a challenge due to porosity of bone
- Use allograft instead of iliac autograft due to paucity of bone
- Anterior spinal fusion only indicated in very young children to prevent crankshaft
- Assoc with LARGE Blood LOSS
15
Q
How is basilar invagination tx?
A
Operative
- decompression and posterior fusion
- radiographic changes of invagination with cord compression with physical exam findings of myelopathy
17
Q
What is the pathophysiology of Osteopetrosis?
A
- Inability to cause acidification in the clear zone and therefore prevent bone resorption
- leads to dense bone and obliterated medullary canal
- may be linked to defect in thymus
19
Q
what are the signs and symptoms of autosomal recessive osteopetrosis ?
A
Symptoms
- Frequent fractures
- progressive blindness and deafness
- Severe anaemia - encroachment of bone into bone marrow starts in early infancy
Signs
- Macrocephaly
- hepatosplenomegaly
- caused by compensatory extramedullary haemopoiesis
- Dental abscess & osteomyelitis of mandible
21
Q
What is seen on radiographs with osteopetrosis?
A
- Erlenmeyer flask proximal humerus and distal femur
- rugger jersey spine w very dense bone
- loss of medullary canal ‘ bone within bone appearance’
- block femoral metaphysis- see pic
22
Q
What is seen in the histology of osteopetrosis?
A
- Defective osteoclasts
- osteoclasts lack ruffled border and clear zone
- islands of calcified cartilage with mature trabeculae
24
Q
What is Ehlers-Danlos syndrome?
A
-
Connective tissue disorder characterised by
- hyperelasticity/fragile skin
- joint hypermobility and dislocation
- generalised ligamentous laxity
- poor wound healing
- early onset arthritis
- soft tissue
- Soft tissue & bone fragility
- mitral valve collapse- aortic root dilation
- DDH
- clubfoot
- pes planus
- scoliosis
- high palate
27
Q
What are the signs and symptoms of ehler’s danlos syndrome?
A
Symptoms
- Double jointed
- easily damaged bruised/stretchy skin
- easy scarring & poor wound healing
- increaed joint mobility, joint popping, early arthritis
- esp shoulders, patellae, ankles
- Chronic musculoskeletal pain- 50%
Signs
- a score of 5 or more on 9 point Beighton-Horan scale = hypermobility
- hyperextension little finger past 90o = 1 point each
- passive abduction of each thumb to foream= i point each
- hypertension of knee = 1 point each
- hyperextension of elbow= 1 point each
- forwarad flexion of trunk w palms flat on floor w knees extended = 1 point
28
Q
What is seen on radiographs of Ehlers danlos syndrome?
A
- Look for subluxations/dislocations
- kyphoscoliosis
