Good morning. My name is Doug Brockmeyer, and the session we are covering today is Return to Play After Sports Injury. My assignment was to talk about atlantoaxial injury, and I felt the best way to get at it is to talk about osodontoidium, and in particular, the incidental osodontoidium, and whether after its diagnosis or treatment you can return to normal life activities or sporting events. I have no disclosures. It's true that some incidental findings in neurosurgery are innocuous, including arachnoid cysts, Chiari malformations, PARS defects, etc., but some are potentially dangerous, such as unruptured aneurysms or perhaps colloid cysts with large ventricles. The question is, is an osodontoidium dangerous, and should it be treated no matter what, and what are the risks of treatment versus conservative therapy, and can people resume normal activities or sports without treatment once the diagnosis of an osodontoidium has been made? By definition, the osodontoidium is a round or oval ossicle that lies above and separate from the body of C2. Its origin has been debated for many years, and it's been divided into congenital and traumatic etiologies. The evidence supports both, but it seems that the most likely cause of most osodontoidiums are a non-united odontoid synconstrosis fracture as a child or a non-united type 2 odontoid fracture as an adult. This picture is to remind us of the complexity of the anatomy at the craniocervical junction and the potential cause of a congenital osodontoidium from failure of the proatlas to unite to the C2 sclerotome. Traditional teaching has taught us that occipital cervical instability has major supporting structures which include the cup-shaped joints, tectorial membrane, the capsular ligaments with other minor stabilizing structures, and C1-2 stability has been driven by the integrity of the odontoid and the presence of the transverse ligament and the strength of the capsular ligaments. However, it is difficult to know which one of these structures plays the major roles. Later I will present evidence to suggest that the capsular ligaments are the major stabilizing structures at occiput C1 and all three of the structures of the odontoid transverse ligament and capsular ligaments are responsible for lanoaxial stabilization. What makes the craniocervical junction and the cervical spine unstable at OC1? We talked about abnormal joint anatomy, malalignment of the supporting bone structures, and ligament islaxity or perhaps disruption of the supporting ligaments. At C1-2, lack of odontoid integrity specifically in osodontoidium can cause instability along with ligament islaxity or perhaps an incompetent transverse ligament. This slide demonstrates the motion inflection and extension with an osodontoidium with the osfragment traveling back and forth with the arch of C1. By design, the C1-2 joint has evolved to facilitate rotation, and if the odontoid is incompetent, it is ill-suited to prevent translational motion, which is actually the most dangerous. Recent evidence from our group at the University of Utah using finite element modeling and biomechanical analysis has brought some new information on this subject. First, we started by creating and validating a normal finite element model for a normal healthy 17-year-old female. We then went on to create validated finite element models for four pediatric and four adult patients. We then used this data in an average fashion in order to arrive at which structures are most responsible for cranioscerical motion. This is an example of three finite element models, one in a 26-year-old and a 59-year-old and a 64-year-old, all females, showing the gross appearance of our modeling system. Using simulation scenarios, once the models are validated, you can remove structures or weaken structures in order to determine their specific roles in cranioscerical motion. In A, we show an intact model. B, we show the transverse ligament in a blue color removed. In C, the tectorial membrane is removed. And in D, both the tectorial membrane and transverse ligament have been removed. This is a video showing normal motion in axial rotation with a 13-month-old female from our pediatric model. After reduction of the strength of the lanoaxial capsular ligaments by three orders of magnitude, this is the amount of motion that we get. These models are also replicated in a 24-year-old female with a 30-pound translational force applied to the occiput. Again, it shows that the combined removal of the tectorial membrane and transverse ligament shows significant motion. This is the summated data from five patients and the experimental studies. Looking at the red bars, we see that weakening of the lanoaxial capsular ligaments by three orders of magnitude shows significant increase of motion between C1 and C2 in flexion. Removal of the transverse ligament shows an increase in motion, but was not found to be significant. In axial rotation, weakening of the lanoaxial capsular ligament shows significant increases in motion. Taken together, those results indicate that the lanoaxial capsular ligaments, as well as odontoid integrity, are major responsible factors for lanoaxial stability. This slide shows the relationship of the lanoaxial joint to the base of the odontoid, and you can imagine that a defect in the base of the odontoid through this area, as well as capsular weakness, can cause significant motion. Again, a line drawn through the capsule and the base of the odontoid could easily show and be responsible for the C1-2 motion. This is shown on the coronal picture on the right as well. So are there circumstances where long-term stability may exist with an os odontoidium? Do clinical studies document this? The classic study by Fielding et al., published in 1980 in the JBJS, followed five patients between one and three years, one of which died. The four patients that were followed remained asymptomatic. Another paper, 1995, suggested that patients were safe to be followed in a conservative fashion without surgery with a, quote, stable os. The Spearings and Brackman article, published in 1982, followed 20 patients managed conservatively, 16 patients with either neck pain or incidental finding. All 16 patients were followed for a mean of seven years without incident. The other four patients presented with myelopathy after minor trauma, and they were followed, and the patients did well overall. However, was there sufficient long-term evidence from these studies to determine whether an os odontoidium could be managed conservatively? This is especially important in younger patients where they have significant lifespans ahead of them. This is a bar graph showing patient ages from the large series of os odontoidium patients, showing the majority of the patients present between six and 15 years of age. If we go by the definition of widened Pujabi for clinical instability, it means the loss of ability of the spine under physiologic loads to maintain its pattern of displacement, so that there is no initial or additional neurological deficit, no major deformity, and no incapacitating pain. The questions that come from this are, how large of a physiologic load can be tolerated in the presence of an os odontoidium? What behavior and activity modifications are sufficient to mitigate the risk of potential instability, and how should the risk of unexpected trauma be factored in? Here's a case illustration of a 15-year-old boy presented with two bouts of transient quadriparosis, one after falling into a pool, and a second wrestling with a friend. After the second bout, medical attention was sought, and he underwent evaluation, which showed gross instability at C1-2. On close questioning, his mother remembered him, quote, falling out of a crib at an early age, and he couldn't move his arms and legs for two weeks. What is the support for surgical management of an incidental os odontoidium? One paper published in 2010 demonstrated 10 patients with acute spinal cord injury due to os odontoidium, three which were previously asymptomatic, and seven who had previous myelopathic symptoms. Our large series published in 2008 was 78 patients, and the total number of patients 78 patients had 44% present with myelopathy at the time of referral, and three had deterioration after an os odontoidium was previously identified. Overall, the way we approach this with our surgical risk assessment is that factors arguing for surgery are a young age, favorable surgical anatomy, and if the patient is significantly unstable. Factors arguing against surgery are older patients, unfavorable anatomy, or if the patient is stable on flexion extension films. This implies that the capsular ligaments over time are strong enough to support the linoaxial joint, and no significant clinical instability is present. Modern treatment typically consists of an instrumented fusion between C1 and C2. You can see here various presentations in a large series, and the vast majority of which were treated with trans-reticular screw fixation. That technique is shown on the left-hand slide. The right-hand slide shows the typical Goel-Harms technique with C1 lateral mass screws and C2 PAR screws coupled with a rod and top-loading screw system. What did the experts say about return to play after successful fusion for an os odontoidium? This was a paper published in 2016 from a consensus from the Spine Trauma Study Group, which included 50 neurosurgeons from 12 countries. First, they defined different surgical risk factors. First, they defined different sports by level of activity and contact, including high-contact, intermediate, and non-contact activities. High-contact activities included tackle football, wrestling, rugby, hockey, gymnastics, etc. The scenario placed before the group was of an 18-year-old minor league hockey player who's driven into the boards and has incomplete quadriparosis, which resolves over the next hour, and burning sensation in his hands, which revolves over the next day. Plane X-rays show normal alignment, but reveals an os odontoidium. He undergoes a posterior C1-2 fusion, which heals, and he has a normal neurological examination. This group of experts in that scenario stated that some element of contact restriction should take place with this patient, with 20 respondents saying he should refrain from high-level contact or would permit him high-level contact, 44% saying intermediate-level contact, 38% saying non-contact. For the same scenario, the percentage of surgeons choosing each recommended time frame for return to maximum level of sporting activity, the majority of the experts stated that at least two to three months, preferably three to six months, should go by before the patient can return to normal activities. I present a case recently cared for at our hospital of a 33-year-old woman who had an aortic arch repair. She's had neck pain for two years, and her last surgery is for a pacemaker. She has no evidence of myelopathy, but her cardiologist ordered a CT scan. Parasagittal images and sagittal images showed an os odontoidium with favorable surgical anatomy. She does not want surgery unless it is absolutely necessary. Here are her reflection extension films showing approximately 10 millimeters of motion between flexion and extension, period. I will let you be the judge as to which management strategy we'll pursue. Thank you very much for your attention.

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surgical management of os odontoidium