Winnipeg Regional Health Association Program of Genetics and Metabolism, University of Manitoba, Winnipeg, MB, Canada.
Skeletal Radiol. 2010 Jan;39(1):49-54. doi: 10.1007/s00256-009-0762-2.
Proximal radioulnar synostosis is a rare upper limb malformation. The elbow is first identifiable at 35 days (after conception), at which stage the cartilaginous anlagen of the humerus, radius and ulna are continuous. Subsequently, longitudinal segmentation produces separation of the distal radius and ulna. However, temporarily, the proximal ends are united and continue to share a common perichondrium. We investigated the hypothesis that posterior congenital dislocation of the radial head and proximal radioulnar fusion are different clinical manifestations of the same primary developmental abnormality.
Records were searched for "proximal radioulnar fusion/posterior radial head dislocation" in patients followed at the local Children's Hospital and Rehabilitation Centre for Children. Relevant radiographic, demographic and clinical data were recorded. Ethics approval was obtained through the University Research Ethics Board.
In total, 28 patients met the inclusion criteria. The majority of patients (16) had bilateral involvement; eight with posterior dislocation of the radial head only; five had posterior radial head dislocation with radioulnar fusion and two had radioulnar fusion without dislocation. One patient had bilateral proximal radioulnar fusion and posterior dislocation of the left radial head. Nine patients had only left-sided involvement, and three had only right-sided involvement.The degree of proximal fusion varied, with some patients showing 'complete' proximal fusion and others showing fusion that occurred slightly distal to the radial head: 'partially separated.' Associated disorders in our cohort included Poland syndrome (two patients), Cornelia de Lange syndrome, chromosome anomalies (including tetrasomy X) and Cenani Lenz syndactyly.
The suggestion of a developmental relationship between posterior dislocation of the radial head and proximal radioulnar fusion is supported by the fact that both anomalies can occur in the same patient. Furthermore, both anomalies can be seen in different patients with the same genetic diagnosis, further supporting the notion that these defects are developmentally related. Posterior dislocation of the radial head and radioulnar fusion are considered to be related primary developmental anomalies of radioulnar differentiation/segmentation. We speculate that the eventual specific defect of this spectrum is influenced by very subtle differences in developmental timing. This is in contrast to patients with transverse forearm defects who can also display radial head dislocation but in an anterior or lateral direction. This direction of dislocation is seen when an abnormal force is exerted on a normally formed radial head later in development or postnatally in disorders such as multiple osteochondromatosis and various mesomelic dysplasias, or as a result of trauma.
近桡尺骨融合是一种罕见的上肢畸形。在妊娠后 35 天（受精后），可以首次识别肘部，此时肱骨、桡骨和尺骨的软骨原基是连续的。随后，纵向分割产生了远端桡骨和尺骨的分离。然而，暂时地，近端仍然联合在一起，并继续共享共同的软骨膜。我们研究了这样一种假设，即桡骨头后先天性脱位和近桡尺骨融合是同一原发性发育异常的不同临床表现。
在当地儿童医院和儿童康复中心随访的患者中，我们搜索了“近桡尺骨融合/桡骨头后脱位”的记录。记录了相关的影像学、人口统计学和临床数据。该研究获得了大学研究伦理委员会的批准。
共有 28 名患者符合纳入标准。大多数患者（16 名）有双侧受累；8 名仅表现为桡骨头后脱位；5 名患者桡骨头后脱位伴桡尺骨融合，2 名患者桡尺骨融合无脱位。1 名患者双侧近桡尺骨融合伴左侧桡骨头后脱位。9 名患者仅单侧受累，3 名患者仅单侧受累。近侧融合程度不同，一些患者表现为“完全”近侧融合，另一些患者表现为融合发生在桡骨头稍远的地方：“部分分离”。我们队列中的合并症包括波兰综合征（2 例）、Cornelia de Lange 综合征、染色体异常（包括四倍体 X）和 Cenani Lenz 并指。
桡骨头后脱位和近桡尺骨融合之间存在发育关系的这一观点得到了以下事实的支持，即两种异常都可能发生在同一患者中。此外，相同的遗传诊断可在不同患者中出现两种异常，进一步支持了这些缺陷具有发育相关性的观点。桡骨头后脱位和桡尺骨融合被认为是桡尺骨分化/分割的相关原发性发育异常。我们推测，该谱中最终的特定缺陷受发育时间非常微小差异的影响。这与横向前臂缺陷的患者形成对比，这些患者也可以表现为桡骨头脱位，但脱位方向是前向或外侧。这种脱位方向发生在正常形成的桡骨头在发育后期或出生后受到异常力作用时，或者在多发性软骨瘤病和各种中胚层发育不良等疾病或创伤时。
