Mild OI |
Prenatal |
No intra-uterine long bone fractures or bowing |
Postnatal |
Rarely congenital fractures |
Normal or near normal growth velocity and height |
Straight long bones i.e. no intrinsic long bone deformity |
Fully ambulant other than at times of acute fracture |
Minimal vertebral crush fractures |
Lumbar spine bone mineral density Z-score usually >−1.5 (−1.5 to +1.5) |
Annualized fracture rate of less than or equal to 1. |
Absence of chronic bone pain or minimal pain controlled by simple analgesics. |
Regular school attendance, i.e., does not miss school due to pain, lethargy, or fatigue |
Moderate OI |
Prenatal |
Rarely fetal long bone fractures or bowing (but may increase in the last trimester) |
Postnatal |
Occasionally congenital fractures |
Decreased growth velocity and height |
Anterior bowing of legs and thighs |
Bowing of long bones related to immobilization for recurrent fractures |
Vertebral crush fractures |
Lumbar spine bone mineral density Z-score usually > −2.5 to <−1.5) but a wide range |
Annualized prepubertal fracture rate greater than 1 (average 3 with a wide range) |
Absent from school due to pain more than 5 days per year. |
Severe OI |
Prenatal |
Shortening of long bones |
Fractures and/or bowing of long bones with some under-modeling |
Slender ribs with absent or discontinuous rib fractures (cases intermediate between severe and extremely severe have few rib fractures but crumpled long bones) |
Decreased mineralization |
Postnatal |
Marked impairment of linear growth |
Wheel-chair dependent |
Progressive deformity of long bones and spine (unrelated to fractures) |
Multiple vertebral crush fractures |
Lumbar spine bone mineral density Z-score usually <−3.0 (wide range with age comparison as measurement is size/height dependent) |
Annualized prepubertal fracture rate greater than 3 fractures per annum (age dependent) |
Chronic bone pain unless treated with bisphosphonates |
School attendance characterized by absences for fracture care and fatigue or pain |
Extremely Severe OI |
Prenatal |
Shortening of long bones |
Fractures and/or bowing of long bones with severe under-modeling leading to crumpled (concertina-like) long bones |
Thick continuously beaded ribs due to multiple sites of fracture or thin ribs (previously described as OI type 2-A and 2-B, respectively) |
Decreased mineralization |
Postnatal |
Thighs held in fixed abduction and external rotation with limitation of movement of most joints |
Clinical indicators of severe chronic pain (pallor, sweatiness, whimpering or grimacing on passive movement) |
Decreased ossification of skull, multiple fractures of long bones and ribs. Small thorax. |
Shortened compacted femurs with a concertina-like appearance |
All vertebrae hypoplastic/crushed |
Respiratory distress leading to perinatal death |
Perinatally lethal course |