Elastic stable intramedullary nails.
History of Intramedullary Nails
The first intramedullary mechanisms were rigid implants; however, more flexible devices appeared in the 1930s with the Klinischer nail and the Rush nail. (1) The Klinischer nail achieved great stability by occupying the entire medullary cross-sectional area of the bone. Nevertheless, it was not very useful in treating children because of difficulties with avoiding the physes. The Rush nail was a more evolved fixation device and is considered the prototype for modern elastic intramedullary fixation. The goal of the Rush nail was to attain 3-point fixation on the inner aspect of the bony cortex. The Rush nail was relatively flexible and was prebent to the proper alignment prior to insertion into the body. Although the Rush nail was the foundation for modern intramedullary fixation, it did have disadvantages. The Rush nail displayed poor rotational stability, and in many circumstances was not adjustable enough to permit insertion points in the metaphysis (located between the epiphysis and the diaphysis of the developing bone).
In the 1980s, surgeons in Nancy, France created an ESIN based on the idea of the Rush nail. This new ESIN used a 3-point fixation like the Rush nail, but drastically improved stability by using 2 pretensioned nails inserted from opposite sides of the bone. With this design, the surgeons were able to create a fixation device that was both elastic and stable) The nails can be made of titanium or steel. If titanium is used, the diameter of the nail must be greater than that of a steel nail because of the flexibility of titanium and its ability to distort in shape. (2) The titanium nails permit stability, which is essential for achieving optimal results. (3) (See Fig. 1.)
[FIGURE 1 OMITTED]
Use of Intramedullary Nails
The technique of elastic stable intramedullary nailing has become one of the most popular methods of fixation for pediatric femoral fractures in North America. (4) Fractures of the femur are the most incapacitating fractures in children. (2) Parsch (5) states that "intramedullary fixation of femoral shaft fractures leads to satisfactory results of alignment and union."
There are several types of fractures that can occur in long bones; however, the ideal fractures for the ESIN are transverse or short with minimal comminution. It also is recommended that the nails be used in children between the ages of 5 and 12 who demonstrate a need for operative stabilization. (4) No clinical indication for the use of ESIN to treat femoral fractures exists in children younger than 5 years. Hip spicas--bandages applied in overlapping opposite spirals to immobilize a limb--are proven to treat femoral fractures adequately in children younger than 5 years of age. The upper age limit for using ESIN is more difficult to determine. According to several studies, the insertion of the nail can cause avascular necrosis at the head of the femur in teenagers. Thus, ESIN fixation should be avoided when the proximal femoral physis is active. The physis is the area of the bone that permits growth and lengthening. Also, when there is questionable stability of the fracture, a cast or brace may be used to ensure correct placement and stability in unison with the nail. (1)
Insertion of the Nail
Typically the ESIN is inserted into the femur retrograde. (4) First, a small incision is made in the skin to insert the rods. Then, an incision is made on the medial or lateral portion of the distal femur. The second incision starts 3 cm above the physis and extends distally for 2.5 cm. (2,3) The flexible rod is previously bent and is forced to straighten out during insertion into the medullary canal because of the shape of the bone. The forced straightening of the previously bent rod tends to angulate the fracture in the direction of the curved rod. As the rod attempts to return to its initial curved position, it is offset by a second rod that matches the shape and diameter of the first rod. The 2 rods have equal and opposing forces that work to stabilize the fracture. It is important to note that the rods usually will be removed. (4)
Results and Complications
Advantages of the ESIN include earlier mobilization and increased rate of return to function compared with nonoperative methods. Also, there is less soft tissue disruption and minimal scarring compared with other surgical processes. (4) The results found in children between the ages of 5 and 14 were optimal. Generally, hospital stays were shortened to only a few days, and the fracture healed on average in 8 to 10 weeks. The presence of the nails did not seem to impair bone healing. (1)
There are various complications associated with elastic stable intramedullary nailing, with the most common being pain and skin irritation at the insertion site. This is caused by bent or prominent nail ends. Pain and irritation at the entry site can be reduced by permitting the ends of the nails to lie along the edge of the metaphysis. However, the nails should not be bent away from the bone. Other complications can include nonunion or delayed union of the bone, generally related to using nails of insufficient diameters. (4) This, however, is very uncommon, and can be avoided by ensuring that the size of the appliance is modified to fit the weight and musculature of the patient. It is also estimated that the diameter of the nails be no more than 40% of the width of the canal. (3) It is advised that the nails be removed after 6 months. (2)
Narayanan et al (6) performed a study to analyze complications associated with the use of titanium elastic stable intramedullary nails over a 5-year period. Of 78 children with 79 femoral fractures treated with this technique, 41 noticed pain and irritation at the insertion site, 8 had radiographic malunion, 2 were refractured, 2 experienced transient neurological deficit and another 2 suffered from superficial wound infections. Malunion and loss of reduction requiring reoperation were related to the use of nails of mismatched diameters. (6) Many of these problems are minor and often preventable.
Overall, elastic stable intramedullary nailing has become a popular technique for fixation for pediatric femoral fractures. ESIN are safe and minimally invasive with few complications and do not hinder bone growth. Children who undergo this procedure also have shorter hospital stays and a swifter return to daily function and activities.
(1.) Barry M, Paterson JMH. Flexible intramedullary nails for fractures in children. J Bone Joint Surg Br. 2004;86(7):947-953.
(2.) Metaizeau J-P. Stable elastic intramedullary nailing for fractures of the femur in children. J Bone Joint Surg Br. 2004; 86(7):954-957.
(3.) The Titanium Elastic Nail System Technique Guide. West Chester, Pa: Synthes; 1998.
(4.) Narayanan UG. Canadian Orthopaedic Association (2005). Elastic Stable (Flexible) Intramedullary Nailing of Paediatric Femoral Fractures. Available at: www.coa-aco. org/articles/publications/scientific/elastic_stable.asp. Accessed November 23, 2005.
(5.) Parsch KD. Modern trends in internal fixation of femoral shaft fractures in children. A critical review. J Pediatr Orthop B. 1997;6(2):117-125.
(6.) Narayanan UG, Hyman JE, Wainwright AM, Rang M, Alman BA. Complications of elastic stable intramedullary nail fixation of pediatric femoral fractures, and how to avoid them. J Pediatr Orthop. 2004;24(4):363-369.
Lisa Landell is a radiography student at Quinnipiac University in Hamden, Conn.
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|Title Annotation:||STUDENT SCOPE; orthopedic fixation devices in pediatric femural fractures|
|Date:||Jan 1, 2007|
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