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Commentary & Perspective | ||||||||
Commentary & Perspective on Leg lengthening has been performed with use of an intramedullary nail to stabilize the femur in skeletally mature patients. In this report, the authors lengthened femora over a humeral intramedullary nail in nine children who ranged in age from eight to eleven years. The advantages of this technique include minimizing the possibility of angular deformity of the femur during and after lengthening and the ability to remove the lengthening device as soon as the desired length has been achieved. Once the desired lengthening has been achieved, the intramedullary nail is locked and the external fixator is removed. The consolidation phase of the lengthening is prolonged, usually twice as long as the lengthening phase. Having performed this technique in patients undergoing femoral lengthening, I can attest to the efficacy of the procedure. I have found that new bone develops much more quickly with an intramedullary nail in place. In addition, there is little risk of refracture after removal of the lengthener. This technique has revolutionized the treatment of limb length discrepancy due to femoral deficiency. Gordon et al. adapted this technique, reputed to be safe and efficacious in adults1, for use in children. In comparison with adults, differences in the anatomy of the femoral head and neck in children necessitate differences in this technique when performed in children. The blood supply to the femoral head in children is totally dependent upon the retinacular blood vessels because the proximal femoral physis is a barrier to the intramedullary flow of blood from the metaphysis to the epiphysis. The traditional entry point for the insertion of an intramedullary nail into the adult femur is through the piriformis fossa; however, this site is exactly where the blood vessels to the immature femoral head reside. Therefore, in a skeletally immature child, the insertion of an intramedullary femoral nail through the piriformis fossa risks injury to the blood supply of the femoral head, with the resultant risk of avascular necrosis. We use locked intramedullary nails for the treatment of fractures of the femur in children; however, the nail is inserted through the tip of the greater trochanter2-4. The patient is placed in the supine position with a bump under the ipsilateral hip. A small lateral incision is made over the greater trochanter. A guide-wire is inserted into the tip of the greater trochanter with use of the C-arm to ensure accurate insertion. To avoid injury to the blood supply of the femoral head, we do not use an awl to enter the lateral portion of the greater trochanter, as Gordon et al. did. Once the guide-wire is inserted, we use a 9-mm cannulated rigid reamer to make an entry hole in the trochanter. The remainder of the surgical technique is identical to that performed in adults for lengthening of the femur over an intramedullary nail. We initially used a straight femoral nail that is small enough to be used in children. Gordon et al. used a humeral nail for femoral lengthening, because this nail is curved and the diameter is small. The fact that the nail is curved enables easier insertion through the greater trochanter and theoretically prevents inadvertent insertion of the nail through the piriformis fossa. A new femoral nail that is curved proximally and can be inserted through the tip of the greater trochanter is currently available in both adult and pediatric diameters. *The authors have identified a complication associated with inserting a femoral nail through the tip of the trochanter—namely, premature closure of the apophysis of the greater trochanter and narrowing of the femoral neck. Narrowing of the femoral neck should not occur with use of the trochanteric entry site because the growth of the neck remains normal. Gordon et al. found that there was a mean increase of only 1 mm in the articulotrochanteric distance in the patients in their series. This change is minimal, although with longer follow-up, one may see a further increase in the articulotrochanteric distance. I believe that this increase is not likely to be significant. The authors' pin-care regimen was limited to asking patients to shower, and all patients in this series had pin-tract problems. We teach our patients to clean their pins several times daily, and, in addition, we use cephelexin prophylactically in all children from the time of the operation until pin removal. We have seen very few pin-tract problems. I agree with the findings of this study—namely, that intramedullary nailing of the femur in skeletally immature patients is safe when the nail is introduced through the tip of the greater trochanter. The authors used a humeral nail because it is narrower than a femoral nail and is curved proximally, which facilitates entry of the nail into the trochanter. They also demonstrated that the blood supply to the femoral head is not disturbed with this approach, and therefore the risk of avascular necrosis of the femoral head should be minimal. The use of a small-diameter nail allows the femur to be lengthened over the nail with use of a lengthener. The proximal screws are inserted into the femur posterior to the nail and can be inserted over guide-wires with use of cannulated drills. The distal screws are inserted as close as possible to the distal femoral physis to accommodate the longest possible nail. The tip of the nail should be as distal to the osteotomy as possible to avoid angular deformity after the desired length has been achieved. This technique has been shown to be effective in adults, and the current authors have used it to treat leg-length discrepancy in children with efficacy and safety. The author did not receive grants or outside funding in support of the research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated. References 1. Paley D, Herzenberg JE, Paremain G, Bhave A. Femoral lengthening over an intramedullary nail. A matched-case comparison with Ilizarov femoral lengthening. J Bone Joint Surg Am. 1997;79:1464-80. | ||||||||
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