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Osteogenesis Imperfecta

(see also: Pyknodyostosis)


  • disease characterized by failure of maturation and organization of collagen fibers;
    • defect in collagen (procollagen to type I collagen sequence and abnormal cross linking) leading to decreased collagen secretion, bone fragility;
    • there may be an inability to form normal bone due to a defect in osteoblastic function;
  • with the formation of abnormal bone, there is a secondary, though not precisely understood, increase in resorption of bone with a secondary increase in bone turnover;
  • osteoid mineralization, osteoclastic activity, and intramembranous bone formation are not affected;
  • classification of osteogenesis imperfecta:
    • note that there is a wide variety in the OI phenotype, but all share in osseous fragility and propensity for fracture;

diff dx

Clinical Features

  • short stature, scoliosis, tooth defects, hearing defects, propensity for fractures, and ligamentous laxity;
    • other abnormalities associated with abnormal collagen formation are evident, such as blue sclerae, abnormalities of tooth formation and skull shape, and occasional deafness;


  • results from marked loss of bone and leads to significant lack of growth of bone in length, and multiple deformities secondary to these fractures;
  • femur fractures are most common but tibial frx may show most severe angulation;
  • frxs may occur at any age, but frx occurance frequently decreases as age increases (often fractures cease at puberty);
  • some adults affected with this disorder will only give a history of occassional fractures and mild osteopenia;
  • fractures tend to heal readily w/ exuberant callus, but the callus formed is of poor quality (identical in structure with the rest of the skeleton);
    • hence it is easily deformed by forces associated with wt bearing;
  • ref: Fractures at Diagnosis in Infants and Children With Osteogenesis Imperfecta


  • laxity of the ligaments results in hypermobile joints & increased incidence in joint dislocation;


  • hearing defects 2nd to inner and middle ear abnormalities may develop, & affected children require regular audiologic examinations;


  • protrusio acetabuli may occur in type III and may narrow pelvic outlet, and can cause constipation or even partial obstruction of rectosigmoid colon;


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  • Sofield osteotomy:
    • indicated for OI patients w/ repetitive frx or progressive angular deformity in a weightbearing bone;
    • involves multiple realignment osteotomies and internal fixation with a load sharing IM device is the treatment of choice;
  • reference:
  • bone deformities caused by microfrx on tension side are common;
    • when severe enough to interfere with bracing or allow recurrent frx, multiple realignment osteotomies (Sofield), fixed w/ expandable IM rods is performed;
    • note that these patients may be at risk for malignant hyperthermia;
    • all substantial deformities should be corrected simultaneously to limit immobilization time;
    • postop bracing to avoid recurrent deformity must be considered;