This question is addressed to the contemporary surgeons engaged with scoliosis surgery. Nowadays, there is a mass practice of instrumentations involving and fixing many spinal segments with a big number of pedicle screws. This changes the distribution of forces on the spine and creates stress risers at both ends of the instrumentation. So many screws correct the deformity very well, the construct is stable but will change the biomechanical life of the bone. Is it not better to remove the screws after the fusion is complete (after 2-3 years) in order to normalize the load distribution and assure a good bone remodelling? What is your opinion and experience ?
i rater do not see so much Problem with the implants staying in place as they are useually included in the Fusion mass and one ned to remove bone in order to get the implants out. Secondly i believe that the potential Advantages do not outweigh the risks of the second surgery
Thank you, Dr. Frank. In the past when we used Harrington rods and outer bracing for at least 6 months, we removed the rods after 2-3 years. The bony fusion was excellent in all cases where the rods did not break earlier. The correction was not so good. Nowadays, the modern multiple implants give an excellent primary correction, but little space for prompt grafting. Stress risers are present at both ends of the construct. I wonder what will happen in 30-40 years when the postmenopausal osteoporosis occurs. I do not think anyone can predict now or has any experience ?
Your concerns are real, and there are very few long term outcome studies. The studies are difficult to do as they involve recruiting patients 20 years or more out from surgery.I agree that the junctional zones are the greatest concern. (the stress shielding over the instrumented spine does not seem to be a problem) Our approach is preoperative digital planning (surgimap) to attempt to leave the patient in optimal sagittal balance post op, since it seems optimal sagittal balance is the best prophylaxis against junctional stress and falloff.
Dr. King,
In my practice I use hooks at both ends of the rods which are fixed to the spine with multiple pedicle screws. The idea is to ensure smooth transition of loads offsides of the construct. Some association with the biiomechanical concept of AO plates for fixation of long bone fractures. In most of the cases I consider removal of the implants when the bony fusion is complete. I believe this a good strategy to save inconveniences for the future generation of colleagues. Regards
Dr. King,
My idea for convertibility of fixation in scoliosis instrumentation is as old as 1996. This was a poster presented at the 20th Congress of SICOT, Amsterdam, 18-23 August 1996. At that time the original CDI already turned out to be very rigid and scoliosis surgery accepted more flexible implants. Later on, there was an avalanche of new instrumentations (more or less rigid). At present implants with multiple fixing elements are very popular but raise concerns about stress risers, stress shielding,etc. I still believe my idea (1996) has not lost its rationality.
https://www.researchgate.net/publication/257066773_TanchevP_LStefanov_DDikov_ADzherov_Convertibility_of_fixation_in_scoliosis_management_20th_World_Congress_of_SICOT_Amsterdam_The_Netherlands_18-23_August_1996_Book_of_Abstracts_p_270
Conference Paper Tanchev,P., L.Stefanov, D.Dikov, A.Dzherov: Convertibility o...
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