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Saturday, March 18, 2000

Limb-lengthening using IM nails has satisfactory outcomes

Limb lengthening in 13 patients using an internal fixator - a Gradual Elongation Intramedullary Nail (GEN) - was satisfactory and showed this method to be more stable, more comfortable and require less lengthening time than an external fixator, said authors of scientific paper 139 presented Thursday.

The Ilizarov fixator, a circular frame and tensioned wires, has many benefits that accelerate bone union through early weight bearing and allows correction of angulation, translation and rotation dur-ing the lengthening period, the researchers said. However, there are disadvantages such as pin site infection, limitation of joint motion by soft tissue fixation, patient discomfort because of bulky size and greater risk of neurovascular injury, they said.

Developed by J.M. Guichet, MD, in 1986, the GEN diaphyseal lengthening system gradually lengthens long bone using an intramedullary nail. The researchers said the major advantage of an internal fixator is stability during distraction. In the course of lengthening with an external fixator, the femur tends to go into varus and anterior angulation, while the tibia tends to go into valgus and anterior angulation. They said GEN also minimizes complications caused by an external fixator such as pin tract infection and unsatisfactory cosmesis, and assure the patient's comfort and the surgeon's convenience of implantation.

The disadvantages are that partial consolidation defect requiring bone graft can occur as a result of the impossibility in controlling the lengthening speed because it can't be shortened once it has been distracted. Also, it can't be used in cases of open growth plate, in preexisting angular deformity or in the narrow medullary canal.

They reviewed 22 cases in 13 patients (five males and eight females) who had leg length discrepancy due to the sequelae of poliomyelitis, post-traumatic leg length discrepancy, familial short stature and Turner's dwarfism. The average age at the time of operation was 23.8 years (range: 14-44 years).

The latency period ranged from five to 10 days (average, seven days). During the distraction period, alternative in-ward and outward maneuvers (about 20 degrees) applied on the distal part of the lower limb allowed lengthening of the apparatus. Five back and forth movements three times a day (1 mm a day) were initiated after the latency period

All limbs were tested manually by applying valgus and varus stresses on the distal art of the lower limb. They also evaluated the results with the clinical and radiographic criteria.

There were six cases of bi-lateral femoral lengthening-four due to familial short stature and two due to Turner's dwarfism. The average length of gain was 5.7 cm and the average percentage of increase was 15.7 percent. There was one case of unilateral femoral lengthening due to sequelae of poliomyelitis. The length of gain was 3.8 cm and percentage of increase was 7.8 per-cent.

There were 12 cases of bi-lateral tibia lengthening; the average length of gain was 5.6 cm and percentage increase, 18.7 percent. The three cases of unilateral tibial lengthening had average length of gain of 2.9 cm and percentage of increase of 9.4 percent.

Co-authors of the study are Soo Bong Hahn, MD, professor; Hui Wan Park, MD, professor; and Hong Jun Park, MD, fellow, all of the department of orthopaedic surgery, Yonsei University College of Medicine, Seoul, Korea.

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2000 Academy News March 18 Index B

Last modified 18/March/2000 by IS