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Magnetically-Activated Intramedullary Limb Lengthening Nail: Tibia

February 10, 2018

Contributors: John E Herzenberg, MD; John E Herzenberg, MD

This video describes the case presentation of a 17-year-old boy with fibular hemimelia who had a 5-cm limb-length discrepancy of the right tibia. The patient underwent insertion of a magnetically-activated lengthening nail in his right tibia for a planned 5-cm lengthening. The length of the nail was selected, and the skin was marked to show the osteotomy site, nail length, and location of other nail components. The osteotomy site was confirmed to be 4 to 6 cm from the weakest part of the nail. Under tourniquet control, the patient underwent fibular osteotomy, Vulpius lengthening, prophylactic anterior compartment fasciotomy, and splitting of the patellar tendon to allow for nail insertion. The tourniquet was then released. Multiple drill holes were created at the tibial osteotomy site to prevent tibial reaming from causing a fat embolism, to provide a place for the reamings to exit, and to allow the reamings to function as bone graft to promote healing.. The nail insertion starting point was determined by inserting a 1.8-mm wire and confirming its trajectory via fluoroscopy. A 2.4-mm diameter Steinmann pin and a 8-mm diameter anterior cruciate ligament reamer to broach the canal were then inserted. The canal was reamed in 0.5-mm increments with the use of a flexible reamer until the canal was reamed 2 mm wider than the nail diameter. The tibial osteotomy was completed, and the nail was inserted beyond the level of the osteotomy, being careful to not apply too much force, which may damage the lengthening mechanism. Proximal and distal locking screws and a proximal syndesmotic screw (through the fibular head) were inserted. A temporary extra-articular calcaneotibial screw was inserted followed by a distal syndesmotic screw. The lengthening nail magnet was identified via fluoroscopy. The nail was tested in the operating room by using the external remote controller to distract the nail 2 mm and shorten the nail 1.5 mm. Three months after insertion, the 5-cm tibial lengthening goal was achieved. Satisfactory healing was observed 10 months postoperatively. The patient did not experience any complications. In the first 100 segments (71 femora, 29 tibiae) treated with lengthening nails at our center, lengthening goals were achieved in 28 of 29 tibiae (97%) and 68 of 71 femora (96%). Mean follow-up was 1.5 years. The mean tibial consolidation index was 46.8 days/cm, and the mean femoral consolidation index was 30.5 days/cm. Complications occurred in 55% of the tibial segments and 30% of the femoral segments.