Radial Head Dislocation and Subluxation in Osteogenesis Imperfecta

2694

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 membrane, 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 dysplasia 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. As this is a hospital- tinguished between radial head dislocation and radial head 9 based study, the study group probably does not provide a rep- subluxation . The other radiographic criteria used in this study resentative cross-section of the entire population of patients are related to normal anatomical descriptions. with osteogenesis imperfecta but most likely is skewed toward Using anteroposterior and lateral radiographs of the those who are more severely affected. In some patients, humerus and forearm, we recorded the presence and direction radiographs from only one upper limb were available. For this of radial head dislocation or radial head subluxation, the 2697

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. 2-A Fig. 2-B Lateral (Fig. 2-A) and anteroposterior (Fig. 2-B) plain radiographs of the right elbow of a patient with type-V osteogenesis imperfecta, showing anterolateral dislocation 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 both anteroposterior and lateral radiographs, the longitudinal axis of the proximal part of the radius does not pass through the capitellum, deﬁning radial head dislocation.

presence of a dysplastic capitellum, the presence of a dysplastic we defined it as dysplastic (Fig. 3-B). The normal radial head is radial head or radial neck, and the presence of interosseous disc-shaped, and its articular surface is a shallow cup for membrane ossification and/or radioulnar synostosis. A nor- articulation with the capitellum of the humerus. The articular mally aligned radial head was said to be present when a line circumference of the head is smooth and is widest medially, coincident with the longitudinal axis of the proximal aspect of where it articulates with the radial notch of the ulna. The neck the radius passed through the center of the capitellum on both of the radius is the constricted part distal to the radial head 10 anteroposterior and lateral radiographs. If this line passed and is overhung by it, especially on the lateral side (Fig. 3-A). through the capitellum but not through its center, we classified If the radial head and/or the radial neck did not correspond the finding as radial head subluxation (Figs. 1-A and 1-B). If to this description, we defined it as a dysplastic radial head or this line did not pass through the capitellum, we defined it as a radial neck (Fig. 3-B). In young patients in whom the capi- radial head dislocation (Figs. 2-A and 2-B). Radial head tellum or the radial head ossification centers had not yet ap- dislocation and radial head subluxation are grouped under peared, only the clearly identifiable abnormalities were noted. the term malaligned radial head. The normal interosseous membrane originates approximately 11 The normal capitellum is a rounded, convex projection, 3 cm distal to the radial tuberosity and extends to the wrist . less than half a sphere, and formed of the anterior and inferior If the interosseous membrane was not radiolucent, we defined surfaces of the lateral part of the condyle of the humerus10 (Fig. it as calcified (Fig. 4). A radioulnar synostosis is a fusion be- 3-A). If the capitellum did not correspond to this description, tween those two bones11 (Fig. 5). 2698

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 III Frequency of Radial Head Dislocation and Subluxation by Type of Osteogenesis Imperfecta

Type of Osteogenesis Imperfecta* I III IV V VI VII All (N = 142) (N = 116) (N = 166) (N = 36) (N = 22) (N = 7) (N = 489)

No. (%) of limbs with radial head dislocation 2 (1) 10 (9) 11 (7) 21 (58) 0 (0) 0 (0) 44 (9) No. (%) of limbs with radial head subluxation 1 (<1) 15 (13) 11 (7) 10 (28) 0 (0) 2 (29) 39 (8) All 3 (2) 25 (22) 22 (13) 31 (86) 0 (0) 2 (29) 83 (17)

*The frequency of radial head dislocation and radial head subluxation differed signiﬁcantly among the types of osteogenesis imperfecta (p < 0.001).

The location (proximal, middle, and distal third), direc- measured the angle between the long axis of the proximal tion, and magnitude of humeral, radial, and ulnar bowing and distal parts of the bone for both the anteroposterior and deformities were recorded for each type of osteogenesis im- the lateral radiograph (Figs. 6-A and 6-B). The magnitude of perfecta. If bowing occurred in several locations or had sev- the deformity was defined by the largest angle measured in eral directions, we classified the finding as multiple bowing. We either radiograph7.

Fig. 3-A Fig. 3-B Anteroposterior radiographs of the right and left elbows of a patient with type-V osteogenesis imperfecta, showing a normal (Fig. 3-A) and a dysplastic (Fig. 3-B) capitellum, radial head, and radial neck. The dotted line on the lateral side of the distal part of the humerus represents the contours of the capitellum. The dotted line on the proximal part of the radius represents the contours of the radial head and radial neck. 2699

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

standard deviations, and comparisons between the means in two groups were performed with a Student t test or a Mann- Whitney U test, as appropriate. Comparison between means in more than two groups was performed by a one-way analysis of variance. Odds ratios derived from logistic regression analysis were used to evaluate factors that were independently associated with radial head malalignment. A p value of <0.05 was considered significant. Results n this series of 489 upper limbs, we observed eighty-three limbs (17%) with radiocapitellar joint malalignment (Table I III). Radial head dislocation was present in 9% and radial head subluxation was present in 8% of the limbs. The frequency of radial head malalignment differed among osteogenesis imperfecta types, ranging from 0% in type VI to 86% in type V. The frequency of radial head dislocation was similar to that of radial head subluxation for all types except for type V and type VII. In type V, radial head dislocation was more prevalent (58% of the upper limbs in the group) than radial head subluxation (28%). This was opposite to the findings in the seven limbs in the type-VII group, in which the radial head was more often subluxated (two upper limbs) than dislocated (no upper limb). Logistic regression analyses revealed that the prevalence of radial head dislocation increased with age, regardless of the type of osteogenesis imperfecta and the sex of the patient (Table IV). Radial head dislocation was also more prevalent in types III, IV, and V than in type I, which was selected as the referencetypeforthepurposeofthelogisticregression analysis. The type of osteogenesis imperfecta, but not age, was also independently associated with radial head subluxation (Table IV). As radial head malalignment seemed to be more frequent in type-V osteogenesis imperfecta than in the other types, we attempted to characterize the differences among the types more Fig. 4 closely. The direction of dislocation was significantly different Radiograph of the left forearm of a patient between type V and the other types (p < 0.001). We found that in type-V osteogenesis imperfecta, nineteen (90%) of twenty- with type-V osteogenesis imperfecta show- one limbs with radial head dislocation had dislocated in an ing a calcified interosseous membrane. anterior, lateral, or anterolateral direction (Figs. 2-A and 2-B), whereas this had occurred in only two (9%) of the twenty-three Clinical Evaluation limbs with radial head dislocation in the other types of The results of clinical examinations were included in this study osteogenesis imperfecta. For types other than type V, posterior if they had been performed within six months of the radio- and posterolateral dislocations were most often seen, charac- graph. Measurements of the range of motion in pronation and terizing sixteen (70%) of twenty-three such limbs, whereas supination as well as hand grip force were obtained by ex- such dislocations occurred in only two (10%) of twenty-one perienced occupational therapists. Three measurements of limbs with radial head dislocation in type-V osteogenesis grip force were performed in the same session, and the mean of imperfecta. No pure medial but five anteromedial or poster- the three was noted. Grip force results were converted into age- omedial radial head dislocations (Figs. 7-A and 7-B) were 12 specific z-scores with use of published reference data . observed, and all of them were in limbs with osteogenesis imperfecta of a type other than type V. Statistical Analysis In type-V osteogenesis imperfecta, all radial head sub- Results of discrete measures were displayed as frequencies, and luxations were anterior, lateral, or anterolateral, following the significance between the groups was assessed by the chi- the same directions most frequently seen in dislocations. For square test. Continuous variables were assessed as means and other types of osteogenesis imperfecta, twenty-four (83%) of 2700

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 IV Effect of Age, Sex, and Type of Osteogenesis Imperfecta on the Frequency of Radial Head Dislocation and Subluxation According to Logistic Regression Analysis

Radial Head Dislocation* Radial Head Subluxation† Yes No P Value‡ Odds Ratio Yes No P Value‡ Odds Ratio

Mean age (yr) 13.18 9.22 <0.001 1.1 11.04 9.4473 0.09 1.1 Sex (F/M) 25/19 228/217 0.19 1.7 21/18 232/218 0.83 0.9 Type of osteogenesis imperfecta (no. of limbs) All types 44 445 <0.001 39 450 0.001 III 10 106 0.02 6.6 15 101 0.003 22.5 IV 11 155 0.04 5.2 11 155 0.03 10.6 V 21 15 <0.001 91.7 10 26 <0.001 48.9 VI 0 22 0.998 0 0 22 0.998 0 VII 0 7 0.999 0 2 5 0.002 67.0

*A significant association was found between radial head dislocation and age and type of osteogenesis imperfecta; no significant association was found between radial head dislocation and sex. †A significant association was found between radial head subluxation and type of osteogenesis imperfecta; no significant association was found between radial head subluxation and age and sex. ‡P values indicate the significance of the association after adjustment for the other two explanatory variables.

twenty-nine limbs with radial head subluxation were lateral, More than 95% of the limbs could be assessed for an posterior, or posterolateral. However, with the numbers stud- abnormal calcification of the interosseous membrane or a ied, this difference in the direction of subluxation was not dysplastic appearance of the capitellum, radial head, or radial found to be significant (p = 0.053). No medial or anteromedial neck. A dysplastic capitellum was significantly associated with subluxations and only one posteromedial subluxation were malalignment in all types of osteogenesis imperfecta (p = 0.008 observed in osteogenesis imperfecta types other than type V. for radial head dislocation in type V, and p < 0.001 for radial

Fig. 5 Lateral radiograph of the right elbow of a patient with type-I osteogenesis imperfecta showing a radioulnar synostosis. 2701

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. 6-A Fig. 6-B Anteroposterior (Fig. 6-A) and lateral (Fig. 6-B) radiographs of the right forearm of a patient with type-V osteogenesis imperfecta, demonstrating the method used to measure the magnitude of the ulnar deformity. The lines represent the axes of the proximal and distal parts of the bone for both views. a is the ulnar deformity angle on the anteroposterior radiograph. b is the ulnar deformity angle on the lateral radiograph. The magnitude of ulnar deformity in this case is b, because it is the larger angle measured.

head dislocation and radial head subluxation in the other types synostosis was not associated with malalignment in type V, and of osteogenesis imperfecta), except for radial head subluxa- was linked only to radial head dislocation in the other types of tion in type V, which may be attributed to the small number of osteogenesis imperfecta (p < 0.001). limbs with radial head subluxation in patients with type-V dis- The direction of bowing deformities in the humerus and ease. A dysplastic radial head or radial neck was associated with forearm bones could be evaluated in 87% of the limbs. In type- malalignment in all types of osteogenesis imperfecta (p < V osteogenesis imperfecta, malalignment of the radial head was 0.02 for both type V and the other types). Calciﬁcation of the associated only with ulnar bowing (p = 0.02 for radial head interosseous membrane was found only in type V and was dislocation and p = 0.03 for radial head subluxation) but not associated with both radial head dislocation (p = 0.01) and with radial bowing. In this type, eight of nineteen limbs with radial head subluxation (p = 0.03) in this group. Radioulnar radial head dislocation had ulnar bowing in multiple direc- 2702

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. 7-A Fig. 7-B Lateral (Fig. 7-A) and anteroposterior (Fig. 7-B) radiographs of the right elbow of a patient with type-IV osteogenesis imperfecta, showing a posteromedial dislocation of the radial head.

tions, and seven of nine limbs with radial head subluxation range of motion was not linked to radial head dislocation in had ulnar bowing in a lateral or anterior direction. The mag- type-V osteogenesis imperfecta and was not linked to radial nitude of the ulnar bowing in the limbs with radial head head subluxation regardless of type. The presence of radial dislocation (mean, 23°) was significantly higher (p = 0.02) than head dislocation was associated with lower grip force, both in that in the upper limbs without radial head dislocation (mean, type V (an average grip force z-score of –3.8 with radial head 12°). In osteogenesis imperfecta other than type V, the direc- dislocation compared with –2.2 without dislocation; p = 0.008) tion and location of radial and ulnar bowing but not of and in type-III or IV osteogenesis imperfecta (an average grip humeral bowing was related to malalignment. However, the force z-score of –4.0 with radial head dislocation compared magnitude of the radial bowing was not linked with malalign- with –2.6 without dislocation; p = 0.05). ment. The magnitude of the ulnar bowing was significantly higher in the presence of radial head dislocation (26°) and Discussion radial head subluxation (19°) than in the absence of radial head n this series of patients with osteogenesis imperfecta, mal- malalignment (11°) (p < 0.01). alignment was present in a substantial number of patients I Additionally, we assessed the relationship between radial and the prevalence of malalignment depended on the type of head malalignment and functional studies, namely, hand grip osteogenesis imperfecta. Radial head malalignment was par- force and forearm motion in pronation and supination. ticularly frequent in type V. In the so-called classic types I Sufficient numbers of studies were available only for patients through IV, the frequency of radial head dislocation seemed with type-III, IV, and V osteogenesis imperfecta. Information to mirror the severity of the disease (type III > type IV > type I). was available for 25% to 47% of the eighty-three limbs affected Previous work from our institution had expanded the by radial head malalignment, depending on the criterion used. Sillence classification of osteogenesis imperfecta by delineating 1 In osteogenesis imperfecta other than type V, the range of three additional types of the disorder (types V, VI, and VII) . motion in pronation and supination was significantly lower The present study highlights the utility of the expanded when radial head dislocation was present (p < 0.001). This classification, as it shows that type V is also a distinct entity 2703

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

with regard to radial head malalignment. The most obvious such patients, whereas calcification of the interosseous mem- specific characteristic of radial head malalignment in type V brane likely is the most critical factor in type V. Prospective is its association with calcification of the interosseous mem- studies are needed to shed more light on these etiological aspects. brane. This calcification was noted in the first description of Although this is by far the largest study on radial head type-V osteogenesis imperfecta by Glorieux et al., who also malalignment in osteogenesis imperfecta, the present analy- noted that the frequency of radial head dislocation seemed sis has a number of limitations. Most importantly, this is a 3 unusually high in this disorder , an impression confirmed by retrospective review of radiographs and patient charts. This the present study. In addition, we found that an anterior and/or may have introduced some selection bias, as radiographic lateral direction of malalignment was typical of type V. Dys- documentation of the upper limb is probably better in patients plastic deformation of the capitellum and radial head or neck who presented with clinical problems in that anatomic area. was also frequently encountered in type V but was not specific Nevertheless, most of the patients more severely affected with for this type. Such dysplastic deformations are also well known osteogenesis imperfecta had regular skeletal surveys of all 9,13-15 from the literature on congenital radial head dislocation . extremities, regardless of clinical manifestations. Radial head malalignment in osteogenesis imperfecta A retrospective and cross-sectional study such as thepres- types other than type V predominantly occurred in a posterior ent one is not a suitable basis for specific treatment recom- and posterolateral direction, also the usual direction of dislo- mendations. Nevertheless, we note that multiple locations and cation in congenital radial head dislocation16. The association directions of forearm deformities and an ulnar bowing mag- between radioulnar synostosis and radial head dislocation is nitude of >20° were frequently associated with radial head dis- another similarity to congenital radial head dislocation13.Bow- location in patients with osteogenesis imperfecta other than ing of both forearm bones was frequently encountered in those with type V. It therefore appears reasonable to hypo- patients with radial head malalignment, which is not surprising thesize that the appearance of radial head dislocation could as fractures are more frequent in the more severe types of be prevented by surgical correction of such deformities. In osteogenesis imperfecta, in turn leading to a higher prevalence type-V osteogenesis imperfecta, such an approach appears less of malalignment. In the presence of malalignment, ulnar bow- promising, as the calcification of the interosseous membrane ing was noted predominantly in a posterior or posterolateral seems to be an important etiological factor. Further studies are direction. Thus, radial head malalignment and ulnar bowing necessary to test whether straightening of the forearm bones commonly had the same direction. It is still unclear whether this indeed prevents radial head dislocation and improves upper association reflects a causal relationship or is a mere coincidence. extremity function. n The present data indicate that patients with radial head NOTE: The authors thank Guylaine Bedard for illustrations appearing on the figures and Kathleen dislocation had functional impairment with regard to grip Montpetit, occupational therapist, for sharing her experience with patients with osteogenesis imperfecta. force and the forearm range of motion in pronation and supination. Similar findings were reported in a small group of 15 patients with congenital radial head dislocation . The factors causing radial head malalignment in osteo- Alice Marcdargent Fassier, MD genesis imperfecta were not directly addressed in this study, but Pediatric Orthopaedics Clinical Fell, McGill University, 1529 Cedar our observations may nevertheless give rise to hypotheses Avenue, Montreal, QC H3G 1AG, Canada. E-mail address: about the etiology of this problem. Schematically, radial head [email protected] malalignment might be due to congenital, developmental, or Frank Rauch, MD traumatic factors. A traumatic etiology is thought to be rare Chantal Janelle, MD, FRCS in general, but it might be more frequent in patients with 17,18 Francxois Fassier, MD, FRCS osteogenesis imperfecta, who can have high fracture rates . Genetics Unit (F.R.), Pediatric Orthopaedics (C.J. and F.F.), However, this possibility could not be investigated on the basis and Hand and Upper Limb Surgery (C.J.), Shriners Hospital of the present study material. In our series, we did not find the for Children, 1529 Cedar Avenue, Montreal, QC H3G 1A6, so-called ulnar bow sign (anterior bow of the ulna) described Canada. E-mail address for F. Rauch: [email protected]. E-mail address for C. Janelle: [email protected]. E-mail address for F. by Lincoln and Mubarak, which can help to identify a 18 Fassier: [email protected] Monteggia-like lesion or dislocation . Posterior or posterolateral ulnar bowing was the only deformity significantly Mehdi Aarabi, MD linked to radial head dislocation in osteogenesis imperfecta Department of Orthopaedic Surgery, Toronto East General Hospital, other than type V (p < 0.01). Progressive long-bone bowing is 825 Coxwell Avenue, Toronto, ON M4C 3E7, Canada. E-mail address: probably a major factor leading to subluxation or dislocation in [email protected]

References 1. Rauch F, Glorieux FH. Osteogenesis imperfecta. Lancet. 2004;363:1377-85. 3. Glorieux FH, Rauch F, Plotkin H, Ward L, Travers R, Roughley P, Lalic L, Glorieux DF, Fassier F, Bishop NJ. Type V osteogenesis imperfecta: 2. Sillence DO, Senn A, Danks DM. Genetic heterogeneity in osteogenesis a new form of brittle bone disease. J Bone Miner Res. 2000;15: imperfecta. J Med Genet. 1979;16:101-16. 1650-8. 2704

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

4. Glorieux FH, Ward LM, Rauch F, Lalic L, Roughley PJ, Travers R. 11. Resnick D, Kransdorf M. Bone and joint imaging. 3rd ed. Philadelphia: Osteogenesis imperfecta type VI: a form of brittle bone disease with a Elsevier Saunders; 2005. Articular anatomy and histology; p 16-23. mineralization defect. J Bone Miner Res. 2002;17:30-8. 12. Rauch F, Neu CM, Wassmer G, Beck B, Rieger-Wettengl G, Rietschel E, 5. Ward LM, Rauch F, Travers R, Chabot G, Azouz EM, Lalic L, Roughley PJ, Manz F, Schoenau E. Muscle analysis by measurement of maximal isometric Glorieux FH. Osteogenesis imperfecta type VII: an autosomal recessive form grip force: new reference data and clinical applications in pediatrics. Pediatr of brittle bone disease. Bone. 2002;31:12-8. Res. 2002;51:505-10. 6. Morello R, Bertin TK, Chen Y, Hicks J, Tonachini L, Monticone M, 13. Almquist EE, Gordon LH, Blue AI. Congenital dislocation of head of radius. Castagnola P, Rauch F, Glorieux FH, Vranka J, Bachinger HP, Pace JM, J Bone Joint Surg Am. 1969;51:1118-27. Schwarze U, Byers PH, Weis M, Fernandes RJ, Eyre DR, Yao Z, Boyce BF, Lee B. CRTAP is required for prolyl 3-hydroxylation and mutations cause recessive 14. Echtler B, Burckhardt A. Isolated congenital dislocation of the radial osteogenesis imperfecta. Cell. 2006;127:291-304. head. Good function in 4 untreated patients after 14-45 years. Acta Orthop Scand. 1997;68:598-600. 7. Amako M, Fassier F, Hamdy RC, Aarabi M, Montpetit K, Glorieux FH. Functional analysis of upper limb deformities in osteogenesis imperfecta. J 15. Reichenbach H, H¨ormann D, Theile H. Hereditary congenital posterior Pediatr Orthop. 2004;24:689-94. dislocation of radial heads. Am J Med Genet. 1995;55:101-4. 8. Greenspan A. Orthopedic imaging: a practical approach. 4th ed. 16. Mardam-Bey T, Ger E. Congenital radial head dislocation. J Hand Surg Philadelphia: Lippincott, Williams and Wilkins; 2004. Radiologic evaluation of Am. 1979;4:316-20. trauma; p 55. 17. Kemnitz S, De Schrijver F, De Smet L. Radial head dislocation with plastic 9. Sachar K, Mih AD. Congenital radial head dislocations. Hand Clin. deformation of the ulna in children. A rare and frequently missed condition. 1998;14:39-47. Acta Orthop Belg. 2000;66:359-62. 10. Osteology. In: Williams PL, Warwick R. Gray’s anatomy. 36th ed. 18. Lincoln TL, Mubarak SJ. ‘‘Isolated’’ traumatic radial-head dislocation. J Philadelphia: WB Saunders; 1980. p 363-6. Pediatr Orthop. 1994;14:454-7.