Three-year-old boy, with no family history of congenital deformities or pathology detected during pregnancy. Physical examination revealed hypoplasia of the right forearm with absence of the third, fourth and fifth digital rays and ulnar deviation of the hand by 60 degrees. Mobility of the thumb and index finger was adequate with good prehensile strength. Sensitivity was considered normal in the two-point discrimination test. Radiologically there was ulnar and radial hypoplasia at the expense of the distal third, with radiohumeral synostosis, absence of early carpal bones and absence of the third, fourth and fifth rays. The total length of the radius was 5.8 cm and 3.0 cm for the ulna, while in the healthy forearm it was 12.0 cm for the radius and 12.4 cm for the ulna, which comparatively corresponded to a deficiency of 48.3% for the radius and 24.1% for the ulna. The humerus on the affected side had a length of 15.5 cm and on the healthy side 17 cm. A diagnosis of right upper limb longitudinal formation failure, postaxial, Bayne's grade IV, with moderate humeral longitudinal shortening was established.

We decided to perform bone elongation of the forearm bones by placing a uniplanar transfixion distractor designed by JMY México® according to the characteristics proposed by Matev (13). Although the lengths of the radius and ulna were different, the distraction of both bones was performed simultaneously. In the first surgical stage, two parallel pins were placed proximal and two distal to the site chosen in the diaphysis of both bones for osteotomy, leaving only the posterior cortex and with a margin between the proximal and distal pins of 3 cm. An incomplete circular osteotomy covering 300 degrees of the circumference was performed and the rest of the cortex was left intact.
The postoperative course was uneventful. On the fourth postoperative day we started the distraction phase at a rate of 2 mm per day for the first 15 days and then at 1 mm per day for 45 days until a total elongation of 7.5 cm was achieved in 60 days. The total length achieved for the radius was 13.3 cm and for the ulna 10.5 cm. Four weeks after completion of distraction we observed adequate longitudinal bone formation radiologically. However, we left the distractor in place until 8 weeks after stopping distraction, at which time we found that there was excellent bone structure in the gap.

The second surgical time was performed at this time to remove the distractor and to perform centralisation of the hand over the distal radial epiphysis. To facilitate this procedure it was necessary to perform a diaphyseal resection of the radius. The new bony fixation was performed with Kischner pins. No osteotomy of the ulna was necessary because its elongation was in the direction of the vector traction and no deviation was observed.

The postoperative evolution was satisfactory, with discrete oedema of the hand that subsided after a short time; the patient recovered the mobility of the fingers and did not suffer any alteration of sensibility.
Six months after completion of the forearm procedure, we placed the distractor in the humerus diaphysis with the same technical procedure as previously described, although it is important to note the anatomical risk points of the nerves and vessels in order to perform the technique meticulously and avoid injury to these structures. In the semicircular corticotomy, we preserved the posterior portion of the periosteum to save the radial nerve; the pins were placed in parallel, two proximal and two distal, with a 3 cm margin between them to perform the corticotomy. Four days later, we started the elongation process at a rate of 1 mm per day, until a gain of 6 cm was achieved. We decided to overcorrect the bone to balance it with the growth of the contralateral arm. At the end of the procedure, we left the distractor in place for 8 weeks, during which time we verified by radiology the adequate bony healing of the gap created for humeral longitudinal growth.

Finally, 8 weeks after completion of the humeral distraction, the time chosen to remove the distractor, we performed the elbow arthrodesis, leaving the elbow joint in a functional position.