New Internal Technology in Limb Lengthening

The development of internally-placed, remote-controlled, magnetic intramedullary nails presents an exciting shift in treatment options for pediatric patients with a limb length discrepancies.1 This condition typically occurs from proximal focal femoral deficiency and fibular hemimelia.1 An internal lengthening device may be superior to the conventional external fixator lengthening, as it is less cumbersome, presents no major concern for pin site infections, is less painful and requires less patient input.

Limb Lengthening X-rays

Note the presence of adequate bony consolidation at the femoral lengthening osteotomy site. This femur was lengthened successfully with the internal magnetic ellipse nail without any malunion. Prior to the magnetic nail insertion, this patient had been treated for a valgus knee deformity with medial distal femoral hemiepiphyseodesis.

“Patients and their parents find this approach much more acceptable than a traditional external device, like the Taylor spatial frame. The patient can bend his or her knee and wear normal clothes; no one would know the child has the device. Clinically, because there are no pins, wires or screws attached to bone through the skin, there is a reduced risk of infection and less muscle and bone tethering,” explains Scott Sorenson, M.D., pediatric orthopaedic surgeon, Bone and Joint Institute.

Following an osteotomy and placement of a distractible intramedullary nail that contains a magnet, the daily treatment consists of applying an external, motorized magnet to the surface of the skin. The magnet communicates with and rotates the internal nail magnet, causing the nail to elongate. The goal is to distract the nail 0.25 millimeters four times a day. Each distraction takes two to three minutes. Dr. Sorenson adds, “As with other types of limb lengthening devices, patients experience minor aches and pain from muscle and nerve tissues being stretched.”

Taylor Spatial Frame

Note the cumbersome size with the Taylor Spatial Frame and the quantity of pins and wires entering into the bone through the skin.

Dr. Sorenson trained at an institution that has successfully used the PRECICE magnetic nail (Ellipse Technologies, Inc.) in several adolescent patients with a simple non-angular limb length discrepancy (Figure). He explains, “The nails are designed to lengthen up to 6.5 centimeters. For patients with discrepancies larger than 6.5 centimeters or accompanied by angular deformity, a Taylor spatial frame is the preferred treatment.”

Dr. Sorenson notes that the devices are not without risks. “There is the potential for rotation or curvation to emerge during limb lengthening with the internal intramedullary nail. This has been reported in about 5 percent of cases. To avoid these types of problems, it’s imperative to very precisely place the nail and to closely monitor each patient during lengthening.”

These patients are seen in clinic every two weeks during the lengthening treatment period. Two to three months after lengthening is complete and bone consolidation is confirmed by X-ray, the device is removed. Dr. Sorenson comments, “Although more clinical data are needed to fully characterize the safety and effectiveness of these types of devices, it is a potential paradigm shift for treatment of patients with uncomplicated non-angular limb length discrepancies.”


Scott Sorenson, M.D.Scott Sorenson, M.D.
Assistant Professor, Orthopaedics and Rehabilitation
Pediatric Orthopaedic Surgeon
PHONE: 717-531-7123
E-MAIL: ssorenson@hmc.psu.edu
FELLOWSHIP: Pediatric orthopaedic surgery, Scottish Rite Children’s Medical Center, Atlanta, Ga.
RESIDENCY: Orthopaedic surgery, Penn State Health Milton S. Hershey Medical Center, Hershey, Pa.
MEDICAL SCHOOL: University of Utah School of Medicine, Salt Lake City, Utah

Connect with Scott Sorenson, M.D. on Doximity


Reference:

  1. Sabharwal S, Nelson SC, Sontich JK. 2015. What’s new in limb lengthening and deformity correction. J Bone Joint Surg. 97:1375-1384.

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