Humeral Lengthening with a Magnetic-Powered Lengthening Nail

Introduction: Different types of external fixation have been used for humeral lengthening, and successful outcomes have been reported in literature. Motorized intramedullary (IM) lengthening nails have evolved as an alternative to external fixation for lengthening of the lower limbs. This study is the first report on using this new IM lengthening technology for humeral lengthening.

Methods: A multicenter, retrospective study was conducted that included 6 humeri in 5 patients (2 males and 3 females; mean age, 20 years) who underwent lengthening with IM lengthening nails at 2 centers in the USA. The etiology was humeral growth arrest post-bone cyst (2 segments), post-septic growth arrest (2 segments), and multiple hereditary exostosis (2 segments in 1 patient). The outcomes measured were length achieved, distraction index (DI), consolidation index (CI), complications, and functional outcomes. Consolidation was described as healing of 3 out of 4 cortices.

Results: Mean follow-up period was 1.4 years (range, 0.7-1.9 years). All segments achieved the lengthening goal; mean lengthening amount was 5.1 cm (range, 4.5-5.8 cm). Mean DI was 0.7 mm/day (range, 0.5-0.8). Mean CI was 36 days/cm (range, 25-45 days/cm). No complications were observed. At the last follow-up, all patients had maintained preoperative shoulder and elbow range of motion. QuickDASH score and upper extremity functional index showed postoperative improvement compared with the preoperative scores.

Conclusion: IM lengthening nails can provide the same results and fewer complications than humeral lengthening with external fixation. IM lengthening nails are able to provide accurate control over the lengthening process.