*** RODDING ***

Some questions and answers on rodding

1. What does « rodding » of a bone mean?
   
       It is the introduction of a metallic device (nail or rod) in the medullary canal (the internal cavity)
       of a long bone.



2. What are the goals of rodding surgery?
   
   
   • As an internal “tutor” it may reduce the risk of fracture and help the bone grow straight.
   • In case of fracture it will reduce the risk of displacement of the bone and ease the treatment.



3. Do all OI children need rods?
   
       No.
       Children who do not fracture often and have straight bones do not need rods.



4. What are the indications for rodding?
   
       OI children who have curved bones or who fracture often may benefit from rodding surgery.



5. What are the different types of rods?
   
       Basically 2 types:
       Telescopic (rod that elongates with bone growth)
       and non-telescopic (regular) rods (see table 1).



6. When to choose a telescopic rod?
   
       Only if there is enough growth potential.
       Such telescopic rods are not indicated in adolescents
       or in patients with “popcorn” physes (little growth potential)



7. When to perform rodding surgery in OI children?
   
       If rodding is deemed necessary (see 3 and 4) then as soon as a child (with bowed legs)
       pulls up to stand, it is time to rod lower extremity long bones.



8. Diameter - Is the rod diameter important?
   
   Yes, too small, the rod will not protect the bone (tutor effect).
   Too large, the rod brings too much rigidity; the bone around the rod does not work and may “disappear”.



9. Sequence
   
   
   • If the 4 long bones of the lower extremities need rodding, the “regular” sequence is to rod 1 leg at a time (femur and tibia) and the other leg a week or 2 later, to avoid need for blood transfusion.
   • Other combinations can be decided by the treating surgeon, depending on the severity of each bone deformity.



10. What complications can occur with rodding?
    
        Besides problems related to the general anesthesia,
        possible surgical complications are:
    • infection,
    • migration of the rod,
    • mechanical failure (fracture of the rod), failure to elongate
    • growth arrest in one bone (epiphysiodesis).
    • fracture at the tip of the rod.



11. Is a spica mandatory after rodding of the femur?
    
        A spica is recommended if fixation in the bone is weak.
        Only the surgeon can decide during the surgery if this (heavy) postoperative
        immobilization is necessary.



12. Why a rod, not a plate?
    
        Plates and screws create a very stiff and short bone segment and the bone is likely
        to break above or below the plate.
        Plates and screws remain contraindicated in most OI cases (despite better bone with Bisphosphonates).



13. Is it safe for people who have rods in their legs to have an MRI?
        
    (Question and Answer originally published as Question of the month by the OIF in their Newsletter)
        MRI stands for Magnetic Resonance Imaging. It is a test that uses a strong magnetic field and pulses of radio waves to make pictures of organs inside the body. It provides information that cannot be seen on an x-ray. It is true that metal objects interfere with the test. People are asked to remove all metal objects such as watches and rings before entering the machine. Even so, people with OI who have rods and other surgical metal can still safely have an MRI if needed. There may be some shadowing directly around the rods, but images are generally good in the areas above or below the rod, and useful information can be obtained.
         Titanium rods interfere the least with the MRI signal. Most rods are stainless steel or alloy, and they do interfere somewhat with the imaging around the rods. Stainless steel rods may cause pain during the test. A CT scan has less interference but isn’t good for looking at the spinal cord or disc.  The doctor who orders the MRI can talk to the radiologist supervising the test to be sure that it will yield enough information, given the type and location of the rods.
        It's a good idea for everyone to keep a record of rods including when they were implanted, the type of rod and the type of metal it was made out of.
    



14. Surgery and Bisphosphonates?
    The bisphosphonates are fixed to the bones within 48 hours after injections. It is therefore recommended to wait 2 days for a surgery after a bisphosphonates injection.
    
    After an osteotomy (bone cut to realign a limb) it is safe to wait 4 months (or clear radiological signs of healing) before the next medical treatment.



Some terms explained
term	explanation
Nail	Same as rod
IM rod	Intra-medullary rod Rod in the the internal cavity of a long bone.
Telescopic rods	A rod that can elongate during growth Dubow-Bailey rod Fassier-Duval rod
Non-telescopic rods	Kirschner wires Rush rods Williams rods Elastic rods
Sliding rods	Two regular rods inserted one from the top, the other from the bottom of the bone, migrating away from each other during growth.
Spica	A plaster cast that extends from the toes to the lower ribs It not only immobilizes the leg but in fact the whole person. This cast prevents the patient from sitting therefore bone loss (osteoporosis) affects the spine.
Femur	The long bone in the upper leg.
“popcorn” physes	Normally the healthy growth plate appears as a line on X-rays in children. In severe OI, the structure of the growth plate is so disturbed that its appearance on X-rays is of "popcorn". In such cases, growth of long bones is markedly retarded.

You can download a factsheet on Rodding Surgery from the website of the OIF.


Female (left) and Male(right) ends of F-D rod



X-ray picture of F-D rods inserted in both femurs.

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last updated March 2012
We are happy to acknowledge the cooperation of Prof.dr. F. Fassier, who provided most of the text
The pictures were made available to us by Pega Medical inc. , the manufacturer of the F-D Rods.