How Much Ulnar Lengthening in Kids with HME-Related Radial Head Dislocation?
Lengthening the ulna is a common method of treating radial head dislocations due to hereditary multiple exostoses (HME) in pediatric patients, but the optimal amount of ulnar lengthening remains unclear. In the June 17, 2020 issue of JBJS, Huang et al. demonstrate that using the proportional ulnar length of 1.1 as a guide to ulnar lengthening can promote spontaneous correction of the radial shaft deformity. The authors arrived at the 1.1 proportion by measuring the normal lengths of the ulna and radius in 20 pediatric patients of different age groups.
Huang et al. then treated 30 forearms (average patient age of 7.4 years) that had a radial head dislocation associated with HME. They excised the osteochondroma around the physis of the distal part of the ulna prior to lengthening. They then pulled the radial head down to the plane of the ulnar coronoid process with a Kirschner wire and lengthened the ulna to predicted proportional length using a modified Ilizarov frame. The technique also facilitated lengthening of the soft tissues of the elbow.
At the time of frame removal, reduction of the dislocated radial head was achieved in 28 forearms (93%). Forearm function also improved markedly, as did radial bowing and the radioarticular angle. The actual ulnar lengthening distance in these patients was greater than the predicted lengthening using the proportional method, but that contributed to the spontaneous remodeling of the radial shaft deformity, and there were no instances of wrist impingement.
The authors conclude that this study demonstrates that, in this clinical scenario, the “proportional ulnar length is a safe and effective parameter to use as the ulnar lengthening reference value.” But they also note that the small number of patients and the average follow-up of 63 months in this study should be expanded in future research.