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Introduction
Rodding surgery involves internal "splinting" of the long bones by means of the insertion of a metal rod. Under general anesthesia, a long bone (e.g., a leg or arm bone) may be cut in one or several places, straightened and "threaded" onto a metal rod. The surgery generally requires an incision long enough to expose the bone where it is deformed. Alternatively, small incisions can be made at the end of the deformed bone, and the rod may be introduced through the skin and moved through the bone under x-ray guidance. When the bone is acutely fractured, rodding can often be done without opening the fracture site.
Rodding is most often used to treat children with moderate to severe osteogenesis imperfecta. In teens and adults, rodding and other surgery is usually reserved for difficult fractures that are not healing well or for alignment problems.
Purpose of Rodding
Rodding is recommended to control repeated fractures of a long bone, and to improve bone deformities that interfere with function. A curved or bowed long bone is not in itself a reason for rodding unless it worsens, repeatedly fractures, becomes painful because of stress fractures, or interferes with function. Rodding does not necessarily prevent fractures; the bone may still fracture, but the rod will provide an internal splint that can help keep the bone in alignment. Fractures may also occur in an area of the bone that grows beyond the end of the rod. Rodding may allow the person to be more active after a fracture, and to avoid prolonged periods of casting and inactivity. This, in turn,
can help break cycles of inactivity leading to fractures. But not everyone with OI needs intramedullary rods.
Ambulation (walking) may be improved after rodding surgery, for example, if a child is ready to walk but is unable to progress because of repeated fractures. However, the severity of OI, and not the technical results of surgery, is primarily responsible for whether ambulation is an appropriate goal. Rodding surgery by itself will not guarantee that the child with a severe form of OI will learn to walk.
Timing of Surgery
Babies with severe forms of OI have numerous fractures at birth and repeated fractures over the following months. The fractures are usually treated with splints or casts rather than surgery. Surgery may be needed over the following years if repeated fractures of one or more long bones occur. The timing of surgery depends on the size of the bone to be rodded. It has to have a large enough diameter to accept a rod. The bones in OI may be thin and flat, so they may appear wider in diameter on x-ray than they actually are. Children with moderately severe forms of OI also have numerous fractures at birth, but few new fractures until they start to stand and walk, which is when repeated fractures of the upper thigh bone (femur) may occur; at this time, surgery may be required.
Rodding is usually undertaken as a scheduled elective procedure. However, it can also be undertaken soon after a fracture to avoid a second period in a cast. The fracture may provide an opportunity to perform a rodding without opening the fracture site.
Types of Rods
The type of rod selected for a particular person usually depends on the size of the bone to be rodded. The rod should usually be small enough to fit into the bone canal and it shouldn't be so large or stiff that it completely shields the bone from stress. Some stress on the bone is useful for maintaining bone density.
There are two major types of rods: non-expanding and expanding.
Non-expanding rods are very versatile, and are made in many sizes. They are inserted to support the full length of the long bone. In some cases, the rod is advanced across the growth areas, which are near the ends of the bone, to provide better support. The smooth surface of the rod does not reduce the growth of the bone. However, this type of rod does not grow with the child, and may need to be replaced as the bone grows if bowing occurs beyond the point where the rod endsrods consist of a smaller rod inserted into a larger hollow rod (like a telescope).
Expanding rods can lengthen as the bone grows, which may prevent the need for replacement. However, they are thicker than non-expanding rods, and are therefore only appropriate for larger bones, such as the femur (thigh bone). The bone must also be strong enough to allow the rod to be "anchored" at either end, and this type of rodding surgery requires incisions around the joints.
Many proper names are used to refer to rods. Some names refer to the people who invented them or the place where they were invented. For example, Bailey-Dubow rods are named after two of the first inventors of expanding rods, while Sheffield rods are a similar type of expanding rod named after the place where they were first made. Rods may also be referred to by their manufacturers' name, such as Rush, Zimmer or Howmedica. Though rods with different names may have their own special features, such as a hook or a threaded end, in general, they can all be classified as either expanding or non-expanding.
Rods can be made of stainless steel or titanium. Titanium has different properties than stainless steel. In general, a rod needs to be stiff enough to support the bone, but not too stiff that it causes disuse atrophy of the bone. The orthopedic surgeon matches the rod properties to the specific needs of the individual, considering bone size and demands placed upon the bone.
Surgery and Aftercare
Rodding procedures are most often undertaken in the thigh bone (femur) and shin bone (tibia). Occasionally, the arm bone requires rodding as well. The spine may be rodded to reduce a scoliosis. With modern anesthesia, children can undergo surgery for longer periods of time, thereby enabling several bones to be rodded at one time (e.g., the femur and tibia of one leg).
The length of the recovery period is determined by the extent of the surgery, the patient's age and activity level. After the surgery, the limb is often supported by a lightweight cast or a splint for about four weeks. An above-the-knee cast is used following tibia surgery. The knee may be bent so that the child can sit in a wheelchair or stroller. Casting following femoral surgery is more difficult. A hip spica, which extends from the ribs down the affected leg, may be required. However, an above-the-knee splint may be sufficient. Some physicians prefer to avoid body or spica casts, choosing lightweight plaster or fiberglass splints instead. Bracing may be used after the removal of the cast to provide added support for standing and walking. This functional brace is worn to protect the limb as the patient becomes more active.
Some physicians may prescribe physical therapy during the recovery period to keep up muscle tone in limbs not affected by the surgery. Other times, physical therapy, sometimes in the swimming pool, is employed after the cast is removed to help the individual regain strength.
Potential Complications
Rodding is major surgery, and as with any major surgical procedure, there are potential complications. These include bleeding problems, problems getting the areas where the bone is cut to unite, rod migration, and problems with the nerves or blood supply in the affected limb. The more serious complications are rare, but they should all be discussed with the surgeon before the procedure is undertaken. Even in the absence of complications, rods may need to be changed as a child grows.
Rod Replacement
The question of replacing a rod comes up when the tip of the rod migrates toward the bone cortex (the outer part of the bone) as a child grows. Whether the rod needs to be replaced depends on the quality of the bone seen on x-ray, as well as the presence of pain, or the appearance that a fracture is impending. In an adult in whom further growth will not occur, the rod should be trimmed or revised only if there is pain or a significant deformity interfering with function.
Non-expanding rods may need to be replaced as the child's bones outgrow them. If a rod protrudes or is painful, or if the bone fractures or looks like it might fracture in an area unprotected by the rod, it is probably time for a replacement. A significant bone deformity that occurs around a rod is another indication for rod replacement.
Sometimes the bone quality is good enough that a rod can be removed from an adult. Also, if there are no longer significant demands placed on the bone, rod removal without replacement may be appropriate. In general, however, the rod should be replaced if the bone looks like it may fracture again.
Summary
There are many considerations in determining whether rodding is necessary and, if so, when and how it should be done. Because OI is so variable, the treatment plan needs to be specific for each individual. Overall, the rodding procedures are successful in improving function with a low frequency of complications.
This fact sheet was prepared by the Osteogenesis Imperfecta Foundation in collaboration with
Peter Smith, M.D, pediatric orthopedist, Shriners Hospital for Children, Chicago, IL.
This information is brought to you by the
NIH Osteoporosis and Related Bone Diseases~National Resource Center (ORBD~NRC)
and the Osteogenesis Imperfecta Foundation
National Institutes of Health
Osteoporosis and Related Bone Diseases
National Resource Center
1232 22nd St., NW
Washington, DC 20037-1292
Tel: 800/624-BONE or 202/223-0344
Fax: 202/293-2356, TYY: 202/466-4315
http://www.osteo.org
E-mail: orbdnrc@nof.org
The National Resource Center is supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases with contributions from the National Institute of Child Health and Human Development, National Institute of Dental and Craniofacial Research, National Institute of Environmental Health Sciences, NIH Office of Research on Women's Health, Office of Women's Health, PHS, and the National Institute on Aging. The Resource Center is operated by the National Osteoporosis Foundation, in collaboration with the Paget Foundation and the Osteogenesis Imperfecta Foundation.
11/01
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