Increasing Severity of Radial Longitudinal Deficiency Correlates With the Degree of Proximal Ulnar Hypoplasia

Classification systems and treatment for children with radial longitudinal deficiency are classically focused on the hand and wrist. However, the elbow can affect the function of these patients secondary to stiffness or instability. The objective of this study was to determine if a correlation exists between severity of radial longitudinal deficiency (RLD) and degree of proximal ulnar hypoplasia.

A single-institution retrospective review was performed at a pediatric hospital. One hundred elbows were identified in 72 patients who met the inclusion criteria. Measurements such as the coronoid height, olecranon coronoid angle (OCA), and the anterior coverage index were obtained from lateral radiographs of children with RLD. Ten elbows had posterior subluxation of the ulnohumeral joint radiographically. Eleven patients had thrombocytopenia absent radius (TAR) syndrome.

There was a significant mean difference for OCA between RLD types. Type 4 RLD (mean [M] = 17.9; standard deviation [SD] = 11.3) had a significantly lower OCA than type 0 (M = 26.4; SD = 5.9) and type 1 (M = 31.0; SD = 5.0). A subanalysis of the 58 elbows with type 4 RLD demonstrated that those with TAR (n = 11) had significantly higher anterior coverage index total scores (M = 1.7; SD = 0.3) than those with type 4 without TAR (M = 1.5; SD = 0.2).

The degree of proximal ulnar hypoplasia is correlated with increasing severity of RLD, with significantly lower OCA and coronoid height observed in the elbow radiographs of patients with type 4 RLD compared with type 0 and type 1. Children with TAR have less proximal ulnar dysplasia and higher anterior coverage index than children with type 4 RLD without associated TAR.

Prognostic IV.