Staged humerus lengthening with monolateral fixation followed by a circular frame: Technique of fixator change

Abstract

Monolateral external fixator (MEF) has been commonly used for limb lengthening in both upper and lower extremities. Since MEF can only lengthen or shorten the bone, sagittal, coronal, and torsional deformities need to be corrected acutely at the time of MEF application. Acute correction, particularly torsional correction, may endanger the radial or peroneal nerves. Gradual correction of torsion may be safely achieved using a circular external fixator (CEF) frame. We present a case study of humeral lengthening with derotation to describe a technique, whereby it is possible to first lengthen with MEF and then derotate with CEF. This is a case report of a 14-year-old boy with a history of neonatal sepsis and growth arrest of the proximal humerus that led to a short right humerus and loss of external rotation. Humerus lengthening was achieved (6.6 cm) using MEF. Conversion to CEF was done after the distraction phase and prior to regenerate bone consolidation. Two 2/3 rings were connected to the proximal and distal fixation half-pins, and then the six connecting struts were added. The rotation deformity correction was then performed gradually to achieve 60° of external rotation. The described technique to convert the MEF into CEF is versatile and can be employed in the clinic safely and without sedation.