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Osteogenesis Imperfecta

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Topic updated on 03/03/16 3:44pm
Introduction
  • A hereditary condition resulting from a decrease in the amount of normal Type I collagen  
  • Pathophysiology
    • can result from 
      • decreased collagen secretion
      • production of abnormal collagen 
    • leads to insufficient osteoid production 
      • physeal osteoblasts cannot form sufficient osteoid 
      • periosteal osteoblasts cannot form sufficient osteoid and therefore cannot remodel normally
  • Genetics
    • 90% have an identifiable genetic mutation 
      • COL 1A1 and COL 1A2   
        • causes abnormal collagen cross-linking via a glycine substitution in the procollagen molecule
    • both autosomal dominant and autosomal recessive forms 
    • can be severe or mild (tarda form)
  • Orthopaedic manifestations
    • bone fragility and fractures
      • fractures heal in normal fashion initially but the bone does not remodel
      • can lead to progressive bowing
    • ligamentous laxity
    • short stature
    • scoliosis
    • codfish vertebrae (compression fx)
    • basilar invagination 
    • olecranon apophyseal avulsion fx
  • Non-Orthopaedic manifestations
    • blue sclera
    • hearing loss
    • brownish opalescent teeth (dentinogenesis imperfecta)
    • wormian skull bones (puzzle piece intrasutural skull bones) 
    • increased risk of malignant hyperthermia
Classification
  • Sillence originally classified into four types
    • however most likely a continuum of disease
    • additional types have been added
    • 90% of patients can be grouped into the Sillence Type I and IV 
Sillence Classification of Osteogenesis Imperfecta (simplified)
Type
Inheritence
Sclerae
Features
Type I Autosomal dominant blue Mildest form.  Presents at preschool age (tarda). Hearing deficit in 50%. Divided into type A and B based on tooth involvement
Type II Autosomal recessive blue Lethal in perinatal period
Type III Autosomal recessive normal Fractures at birth. Progressively short stature. Most severe survivable form
Type IV Autosomal dominant normal Moderate severity. Bowing bones and vertebral fractures are common. Hearing normal. Divided into type A and B based on tooth involvement

                                Type V, VI, VII have been added to the original classification system                                       (these have no Type I collagen mutation but have abnormal bone on microscopy and a similar phenotype)

Type V   Hypertrophic callus after fracture. Ossification of IOM between radius and ulna and tibia and fibula
Type VI   Moderate severity. Similar to type IV
Type VII   Associated with rhizomelia and coxa vara
 
Presentation
  • Symptoms
    • mild cases
      • multiple fractures during childhood 
    • severe cases 
      • present with fractures at birth and can be fatal  
      • number of fractures typically decreases as patient ages and usually stops after puberty
    • basilar invagination 
      • presents with apnea, altered consciousness, ataxia, or myelopathy
      • usually in third or fourth decade of life, but can be as early as teenage years
  • Physical exam
    • multiple fractures leads to
      • saber shin appearance of tibia 
      • bowing of long bones 
Imaging
  • Radiographs
    • thin cortices
    • generalized osteopenia
    • saber shins 
    • skull radiographs reveal wormian bones
Evaluation
  • Histology 
    • increased diameter of haversion canals and osteocyte lacunae
    • replicated cement lines
    • increased number of osteoblasts and osteoclasts
    • decreased number of trabeculae
    • decreased cortical thickness
  • Diagnosis
    • diagnosis is based on family history associated with typical radiographic and clinical features
    • Labs
      • no commercially available diagnostic test due to variety of genetic mutations
      • laboratory values are typically within normal range
    • possible methods diagnosis include
      • skull radiographs to look for wormian bones
      • fibroblast culturing to analyze type I collagen (positive in 80% of type IV)
        • can be used for confirmation of diagnosis in equivocal cases
      • biopsy
        • collagen analysis of a punch biopsy
        • iliac crest biopsy which shows a decrease in cortical widths and cancellous bone volume, with increased bone remodeling.
Treatment of Fractures
  • Fracture prevention
    • early bracing 
      • indicated to decrease deformity and lessen fractures
    • bisphosphonates
      • indicated in most cases of OI to reduce fracture rate and pain
      • functions to increase cortical thickness by inhibiting osteoclasts
      • does not affect development of scoliosis
      • chronic use causes horizontal metaphyseal bands seen on radiographs  
    • growth hormone
    • bone marrow transplantation 
      • has been used with some success
  • Fracture treatment
    • nonoperative
      • observation
        • indications
          • indicated if child is <2 years (treat as child without OI)
    • operative
      • fixation with telescoping rodes
        • indications
          • consider in patients > 2 years
          • allow continued growth
Treatment of Long Bone Bowing Deformities
  • Operative
    • realignment osteotomy with rod fixation (Sofield-Miller procedure) 
      • indications
        • severe deformity to reduce fracture rates
      • techniques include
        • nontelescopic devices (Rush rods, Williams rods)
        • telescopic devices (Sheffield rod, Bailey-Dubow rod, Fassier-Duval rod)
Treatment of Scoliosis
  • Nonoperative
    • observation 
      • indications
        •  if curve is <45 °
    • bracing is ineffective
  • Operative
    • posterior spinal fusion  
      • indications
        • for curves > 45 ° in mild forms and > 35 ° in severe forms
      • technique
        • challenging due to fragility of bones
        • use allograft instead of iliac crest autograft due to paucity of bone
        • ASF only indicated in very young children to prevent crankshaft
        • associated with a large blood loss
Treatment of Basilar Invagination
  • Operative
    • decompression and posterior fusion
      • indications
        • radiographic features of invagination and cord compression with physical exam findings of myelopathy
      • techniques
        • resection of bony compression via transoral approach

 

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Qbank (12 Questions)

TAG
(OBQ11.207) A 12-year-old girl has been diagnosed with a severe form of osteogenesis imperfecta that has resulted in thin bones and multiple fractures. She now presents for follow-up of scoliosis which was noticed by her mother 1 year ago. She has no back pain and is neurologically intact. Radiographs show a 42-degree right thoracic curve, which has increased from 31-degree from her previous radiographs taken 9 months earlier. What is the most appropriate management for her spinal deformity? Topic Review Topic

1. Observation alone with serial radiographic and clinical monitoring.
2. Posterior spinal fusion with instrumentation
3. Anterior spinal fusion with instrumentation
4. Fixation with telescoping rods
5. Custom-molded bracing with serial radiographic and clinical monitoring.

PREFERRED RESPONSE ▶
TAG
(OBQ11.216) A 10-year-old girl has bilateral knee radiographs as shown in Figure A. Which of the following conditions is most likely present? Topic Review Topic
FIGURES: A          

1. Osteogenesis imperfecta (OI)
2. Ellis-van Creveld (EVC) syndrome/chondroectodermal dysplasia
3. Marfan syndrome
4. Caffey disease
5. Juvenile idiopathic arthritis (JIA)

PREFERRED RESPONSE ▶
TAG
(OBQ10.265) Which of the following pediatric congenital disorders is caused by a glycine substitution in the procollagen molecule? Topic Review Topic

1. Scurvy
2. Osteogenesis imperfecta
3. Fibrous dysplasia
4. Diastrophic dysplasia
5. Ochronosis (alkaptonuria)

PREFERRED RESPONSE ▶
TAG
(OBQ09.68) Type I collagen defects are responsible for the clinical manifestations of osteogenesis imperfecta. Mutation of what gene or genes are most responsible for this? Topic Review Topic

1. FGFR3
2. FGFR2
3. COMP
4. COL1A1/COL1A2
5. Fibrillin

PREFERRED RESPONSE ▶
TAG
(OBQ08.263) An adolescent male with a known genetic mutation of COL1A1 presents to the emergency department with symptoms of unsteady gait and difficulty with buttoning his shirt. On physical exam, when the patient holds his fingers extended and adducted, the small finger spontaneously abducts. Snapping of the patient's distal phalanx of the middle finger leads to spontaneous flexion of the other fingers. What is the most likely cause of the patient's symptoms? Topic Review Topic

1. Basilar invagination
2. C6 cervical disc foraminal herniation
3. Atlantoaxial instability
4. Ossification of the posterior longitudinal ligament (OPLL)
5. Epidural abscess

PREFERRED RESPONSE ▶
TAG
(OBQ06.205) A mutation in the COL1A1 and COL1A2 genes is associated with all of the following manifestations EXCEPT: Topic Review Topic

1. Basilar invagination
2. Webbed neck
3. Olecranon apophyseal avulsion fractures
4. Scoliosis
5. Discoloration of sclerae

PREFERRED RESPONSE ▶
TAG
(OBQ05.220) A 12-year-old girl presents with a history of numerous long bone fractures in the past. Examination reveals normal-appearing sclera, and the dentin abnormality shown in Figure A. A radiograph of her lower extremities is shown in Figure B. The patient’s disorder is the result of which of the following? Topic Review Topic
FIGURES: A   B        

1. Vitamin D deficiency
2. Abnormal osteoclast function
3. Qualitative defect of type I collagen synthesis
4. Mutated fibroblast growth factor receptor
5. Defective N-Ac-Gal-6 sulfate sulfatase enzyme

PREFERRED RESPONSE ▶
TAG
(OBQ04.263) A child has a genetic disorder of the COL1A1 gene resulting in a decreased production of functional type I collagen. Which of the following radiographs is MOST consistent with his condition? Topic Review Topic
FIGURES: A   B   C   D   E  

1. Figure A
2. Figure B
3. Figure C
4. Figure D
5. Figure E

PREFERRED RESPONSE ▶
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