Acute Deformity Correction and Lengthening Using Magnetic Intramedullary Lengthening Nails

Introduction: Our aim was to determine the results of using intramedullary (IM) lengthening nails for simultaneous lower limb lengthening and acute deformity correction.

Methods: Medical records of 25 patients (18 femora, 11 tibiae) were retrospectively reviewed. Mean age was 17 years (range, 8-49 years). Most patients were 20 years or younger (26 of 29 segments). Patients underwent simultaneous lengthening and acute deformity correction with IM magnetic lengthening nails between January 2012 and August 2015.

Results: Mean follow-up was 2 years (range, 0.4-4 years). Mean lengthening goal was 4.7 cm (range, 1-8 cm). Mean angular deformity was 7° (range, 4°-11°). Mean rotational deformity was 18° (range, 10°-45°). Mean distraction index was 0.7 mm/day (range, 0.4-1.2 mm/day). Mean consolidation index was 43 days/cm (range, 17-108 days/cm). All segments achieved desired deformity correction. Preoperative and postoperative mean mechanical axis deviation was 1.3 cm (range, 0-3.5 cm) and 0.8 cm (range, 0-2.5 cm), respectively. Femora had mean preoperative and postoperative lateral distal femoral angle (frontal plane) of 85° and 89°, respectively. Femora had mean preoperative and postoperative posterior distal femoral angle (sagittal plane) of 76° and 84°, respectively. Tibiae had mean preoperative and postoperative medial proximal tibial angle (frontal plane) of 94° and 89°, respectively. Tibiae had mean preoperative and postoperative posterior proximal tibial angle (sagittal plane) of 72° and 79°, respectively. Rotational malalignment was corrected in all cases based on clinical examination of rotational profile. Two femora (7%) did not achieve lengthening goals due to knee rotatory subluxation and delayed regenerate healing.

Conclusion: With preoperative planning and intraoperative fixator-assisted nailing technique, IM lengthening systems allow for lengthening and simultaneous acute angular, rotational, or combined deformity correction. One limitation is that the apex of deformity must be located at/near the lengthening osteotomy site. It is unclear whether deformities with magnitudes >15° can be accommodated.