2694 COPYRIGHT Ó 2007 BY THE JOURNAL OF BONE AND JOINT SURGERY,INCORPORATED Radial Head Dislocation and Subluxation in Osteogenesis Imperfecta By Alice Marcdargent Fassier, MD, Frank Rauch, MD, Mehdi Aarabi, MD, Chantal Janelle, MD, FRCS, and Francxois Fassier, MD, FRCS Investigation performed at Shriners Hospital, Montreal, Quebec, Canada Background: Upper limb deformity in children with osteogenesis imperfecta may substantially impair function. The aims of this retrospective work were to study the prevalence of radial head malalignment (dislocation or subluxation) in different types of osteogenesis imperfecta and to identify factors linked to it. Methods: We assessed 489 upper limbs from 254 patients (with a mean age of 9.6 years and including 130 female patients) who had various types of osteogenesis imperfecta. Radiographs representing a single time-point for each patient were assessed for the presence and direction of radial head malalignment and associated abnormalities (dysplasia of the capitellum or of the radial head or neck, calcification of the interosseous mem- brane, or radioulnar synostosis). Deformations of the humerus, radius, and ulna were assessed with regard to location, direction, and magnitude. The forearm range of motion in pronation and supination and the hand grip force were measured in a subset of patients. Results: We observed radial head dislocation or subluxation in forty-four and thirty-nine upper extremities, respec- tively. The frequency of radial head malalignment was significantly higher in type-V osteogenesis imperfecta (86%) than in the other types (0% to 29%) (p < 0.001). Dysplasia of the humeral capitellum, radial head, or radial neck was associated with malalignment in all types of osteogenesis imperfecta, with the exception of capitellum dys- plasia in type V. Malalignment in type V was associated with calcification of the interosseous membrane, an abnormality that was specific for type V. In the other osteogenesis imperfecta types, malalignment was commonly linked with radial and ulnar deformation and was associated with decreased forearm range of motion in supination and pronation and a lower grip force. Conclusions: Radial head malalignment is common in osteogenesis imperfecta, especially in type V. Malalign- ment is associated with bowing characteristics and impaired function of the upper limb. These findings may provide support for surgical correction of radial and ulnar bowing in selected patients with osteogenesis imperfecta. Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence. steogenesis imperfecta is a heritable disorder charac- to multiple rib and long bone fractures at birth. Type III is the terized by bone fragility, short stature, and bone most severe form for surviving children and is associated with deformities associated with typical extraskeletal man- progressive bone deformities and scoliosis. Type IV is a O ifestations such as dentinogenesis imperfecta. It is most often moderate form and includes patients who do not conform to 1 caused by mutations affecting collagen type I . Disease severity the previous categories. From this last and rather heteroge- ranges from intrauterine fractures and perinatal lethality to neous group of patients, three additional types of osteogenesis very mild forms with rare fractures. Sillence et al. separated imperfecta (types V, VI, and VII) have recently been delineated, 2 osteogenesis imperfecta into four types . Type I includes on the basis of the absence of collagen type-I mutations and the patients with a mild nondeforming form and a normal or specific clinical and histologic features of the bones. Type-V mildly short stature. Type II is a perinatally lethal form related osteogenesis imperfecta is characterized by hyperplastic callus Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated. J Bone Joint Surg Am. 2007;89:2694-704 d doi:10.2106/JBJS.F.01287 2695 THE J OURNAL OF BONE &JOINT S URGERY d JBJS. ORG RADIAL HEAD DISLOCATION AND SUBLUXATION IN V OLUME 89-A d N UMBER 12 d D ECEMBER 2007 OSTEOGENESIS IMPERFECTA TABLE I Classification of the Types of Osteogenesis Imperfecta Type Severity Characteristics I Mild Normal stature, few or no bone deformities, vertebral fractures, triangular face, blue sclera, and able to walk II Perinatally Multiple fractures at birth lethal III Severe Short stature, scoliosis, triangular face, grayish sclera, and may be able to walk with aid IV Moderate Short stature, scoliosis, white sclera, and able to walk but may require aid V Moderate Moderately short stature, hyperplastic callus, ossification of interosseous membrane of the forearm and leg leading to limited mobility, and white sclera VI Moderate- Moderately short stature, frequent fractures, vertebral compression, and white sclera severe VII Moderate Mildly short stature, short humeri and femora, coxa vara, and white sclera formation, calcification of the interosseous membrane of the The aims of the present retrospective study were to investigate forearm and/or the leg, and an irregular pattern of bone the prevalence of radial head malalignment in the different 3 lamellation seen under polarized light microscopy . The diag- types of osteogenesis imperfecta and to identify factors linked nosis of type-VI osteogenesis imperfecta is based on specific to such malalignment. histologic findings in the bone, including a mineralization 4 defect affecting bone but not cartilage tissue .TypeVIIisa Materials and Methods moderately severe form of osteogenesis imperfecta with short etween January 1992 and June 2004, 376 patients with 5 humeri, short femora, and coxa vara . A recent study found B osteogenesis imperfecta were seen at least once in our 6 that type VII is caused by a mutation in the CRTAP gene . institution. Patients were included in the present study if they Table I summarizes the current classification of osteogenesis could be diagnosed as having a specific type of osteogenesis imperfecta. imperfecta, did not have a recent or unhealed upper limb Deformities of the upper extremity in osteogenesis im- fracture, and had had at least one radiographic assessment of perfecta have been studied far less frequently than those of the upper limb at our clinic. Patients in whom radial head the lower limbs, probably because they are less frequent and alignment was impossible to define on the radiographs were have less obvious functional implications. However, Amako excluded. Two hundred and fifty-four patients (130 female and et al. showed that upper limb deformities in children with 124 male patients) fulfilled these inclusion criteria. The mean osteogenesis imperfecta are not only a cosmetic problem but age was 9.5 years (range, 1.5 months to 23.5 years). Seventy-six may substantially impair functional activities of daily living7. patients (30%) had type-I; sixty (23.5%), type-III; eighty-six TABLE II Distribution of Upper Limbs in Study Patients According to Age, Sex, Side, and Type of Osteogenesis Imperfecta Type of Osteogenesis Imperfecta* I III IV V VI VII All Mean age (yr) 10.0 8.8 8.8 12.3 12.8 8.0 9.6 Sex Male 72 48 78 20 18 0 236 Female 70 68 88 16 4 7 253 Side Right 71 58 83 18 11 3 244 Left 71 58 83 18 11 4 245 Total 142 116 166 36 22 7 489 Percentage of all types 29 24 34 7 5 1 100 *A significant difference was found among the types of osteogenesis imperfecta with respect to age (p = 0.046) and sex distribution (p < 0.001). 2696 THE J OURNAL OF BONE &JOINT S URGERY d JBJS. ORG RADIAL HEAD DISLOCATION AND SUBLUXATION IN V OLUME 89-A d N UMBER 12 d D ECEMBER 2007 OSTEOGENESIS IMPERFECTA Fig. 1-A Fig. 1-B Anteroposterior (Fig. 1-A) and lateral (Fig. 1-B) radiographs of the left elbow of a patient with type-IV osteogenesis imperfecta, showing lateral subluxation of the radial head. The straight line represents the longitudinal axis of the proximal part of the radius. The dotted line represents the contours of the normal capitellum. The cross represents the center of the capitellum. On the anteroposterior radiograph, the longitudinal axis of the proximal part of the radius passes through the capitellum but not in the center, defining radial head subluxation. (34%), type-IV; eighteen (7%), type-V; ten (4%), type-VI; reason, results are presented relative to the number of upper and four (1.5%), type-VII osteogenesis imperfecta. The clas- limbs rather than relative to the number of patients. The dis- sification of patients according to the type of osteogenesis tribution of examined upper limbs according to age, sex, side, imperfecta was primarily based on clinical characteristics. and type of osteogenesis imperfecta is shown in Table II. However, in all patients with types V, VI, and VII, the diagnosis had been confirmed by the absence of collagen type-I muta- Radiographic Assessment tions and specific findings on histologic analysis of the iliac There are no established radiographic criteria to assess radial bone. head malalignment and associated abnormalities. Neverthe- For each patient, we selected radiographs from a single less, dislocation is commonly defined as the complete disrup- time-point, when documentation of the relevant skeletal areas tion of a joint, whereas subluxation is a minor disruption of 8 was best. Anteroposterior and lateral radiographs of 489 upper a joint in which some articular contact remains . According extremities were available. Most of these radiographs were to the criteria defined by Sachar and Mih, we therefore dis- made as part of routine skeletal surveys.