Focusing particularly on the needs of obese patients, neurosurgeon Aaron Clark, MD, PhD, discusses anterior and lateral approaches to lumbar interbody fusion. He describes advantages of ALIF; recent research on surgical complications (with relevance for pre-op patient counseling as well as procedure planning); and steps to achieving deformity correction goals.
Hello. My name is Peter Sung. I'm a pediatric neurosurgeon that UCSF Benning off Children's hospital. Thank you dr Metz for inviting me. Thank you for logging in. Um My talk today is on the pediatric cranial cervical junction obviously. Um we're not in a interactive environment but this is my email. Please email me for any questions or cases um that um they come up. I have no disclosures just to start off with some anatomy and the pediatric cervical spine. The folk um of the cervical spine due to the relatively large head of the child is at the cervical cranial junction at C. 12. This is of course a distinction with the adult cervical spine where the fulcrum isn't a sub actual spine. And due to the developmental complexity here, not only is the force is concentrated at the cranial cervical junction, cranial cervical junction in Children but also due to the embryology, there could be a variety of pathology at the queen of cervical junction. In terms of the biomechanics, we know that the vast majority of the rotation between the cervical spine is at C. 12 whereby the dense serves as a axis of rotation. We look at the anatomical relationships between the oxford and see one there's really is very little rotation in this cup like orientation of the joint but there is some flexion extension and then there's also a little bit of lateral bending. The vast majority of The movement across this complex is rotation at c. and this really works as of one unit. The between the oxygen and C. Two. Or the cranial cervical junction whereby C. One really is the washer. The major ligament is stability and the major uh muscular stability that is conferred across the cranial cervical junction really are structures that go from the occipital to the C. Two in the back and the oxygen put this the cli vous to the back to see one in the front while the segmental structures themselves such as the epochal membrane. Mhm. And the joint capsules do confer some stability along with the posterior acceptable Atlanta membranes and the Atlanta axial membranes. It's really the big muscles that span the back and the textural ligament that goes from the occipet to see to that confers major stability. Of course the dense itself is held against the interior reno see one with the transfers ligament as a major mm hmm, translational stability of this joint. And keeping this in mind. We can see later on in terms of the ligament, the structures and disruptions and the measurements that we take at this area can incorporate from occipet to see too. And not just limited within the segmental or not relationships between O. C. One and C. One and C. Two. So in terms of the classification of cranial cervical abnormalities. We can have of course acquired trauma or neo plastic which is rare but occasionally it can happen. We can have a host of genetic or metabolic disorders. And we can have congenital deformities either of the occipital bone with basil and imagination of the atlas with a play asia or occipital assimilation. In addition we can also have chiari malformation which is uh neurological with descent of the surveil our tonsils into the cervical spine which also carries associated only anomalies that we will touch on. So the indications for treatment is of course neurological compression uh and instability along with the spectrum. Also we have to look at the anterior pathology. The anterior compression also figures largely into our treatment paradigm in terms of the neurological uh assigned simp symptoms. Obviously there's a host of these because of the brain stem of cervical spinal cord uh and cranial nerves. But also I just want to highlight often that you know, Children can present with just a head tilt due to um either bring some compression or subtle cranial nerve um um difficulties that they have a little bit of a head tilt and that can be the harbinger of a major cranial cervical uh abnormality. So m. R. I were looking for the compression of this neurological structures, court signal change and the development of a new syringes can represent subtle compression and alteration of CSF dynamics. So in terms of the bony criteria for clinical and stability across the cranial cervical junction, there are a variety of measurements. Um I think because of the diagnostic uncertainty oftentimes these patients are in politi trauma of course they're not following commands. Uh All these relationships have been developed and obviously on occasion we would have a very obvious case like this where there is over cranial cervical instability or distraction in a pretty much a lethal injury. Just going over some of these criteria of course we have the dental dental interval which we can accept up to 6 mm and we are mindful that if there is greater than 10 millimeters of disruption of the Atlanta will uh dental interval. The relationship with the occipital can also be uh disrupted and that the electoral membrane can be lifted up and we have occipital cervical instability. And not just limited to uh see 12 here we can see that there is a major Atlanta axial instability and this textural membrane is stretched off of the cli vous and then the posterior occipital is lifted up. In addition with this severe um core compression from the dense in this case the patient had a trans oral decompression and the occipital cervical fusion and not just the C. 12 fusion due to the laxity. The potential laxity of the electoral membrane which involves the occipital. So um talking about the dense Bazian interval is looking at the relationship between the climate and the tip of the dens. It's uh 10 to 12.5 millimeter is a upper limit of normal of course. In Children when we have incomplete ossification of the tip of the dense this can be a problematic uh measurements where we can't see it basically. And in terms of its dynamic stretching, it's very has to have very little uh flex uh change in uh flexion extension less than two millimeters to one millimeter. In adults. Here is a a measurement device by looking at the embassy in axial interval or B. A. I. Whereby we're looking at the relationship between of the cli vous to the back of the dense. If it's stretched forward then of course the textural membrane could be involved And we have instability in it. It's an anterior measurement. It's not a posterior measurement. We tolerate up to 12 mm anterior early but there's no posterior translational measurement and we have no flexion extension data on this uh radiographic criteria of cranial cervical instability. Now we can look at the joint itself between the oxygen and see one. And this measurement is the upper limit of normal is felt to be between three and five millimeters. Obviously if this is lifted up as we talked about it's the uh or this joint is separated is not just the joint capsule that had been keeping this firmly intact is the technical membrane and the front and the muscular turn the back. Um So this is a direct measurement. Best thing on cT data there's a couple of ratios. One is um powers ratio whereby if the cranium kind of moves forward relative to see one uh then that's considered unstable. And the X line. Also the cranium must move forward relative to this line between the cli voce And the back of c. two. Then it's felt to be unstable as the cranium is shifted forward. We also looked at some relationships um but not just between the occipet and C. One or C. Two. But rather a relationship that we can easily measure, measuring the C. 12, separation relative to see 23. As you can see this is a major distraction injury. It is separated at the same time process. And we have massive sea except cranial cervical dislocation. But you can see that the C. One is super separated from sea to relative to the preserved uh C. 23 relationships. So this gave us the idea of looking at this ratio to determine whether we have quinoa cervical instability. And when we look at the M. R. I. Abnormalities of the cranial cervical junction and trauma. The vast majority is in the cranial cervical junction and not in the sub actual spine. Uh Kind of illustrating our first slide whereby we have a very large cranium and as the rocks on the cervical spine. This is where the folk um of uh the energy is transmitted mostly in the cranial cervical spine uh junction. There is a variety of of of injuries. We can have a little epidural hematoma along the cli vous. We can have a separation between C. 12. We can have major muscle contusions on the back. As illustrated by this case. We can have an atypical membrane abnormality such as in this patient where the applicant membrane is torn and we have some fluid, bloody fluid in the synovial joint here one capsule is separated. The other capsule is intact. We can see this capsule on the right side is uh the patient is uh distracted on the other side, it is still intact. This is another capsule er separation and then we move on to when there wherever there is bilateral capsule separation. When we look at these injuries, there's always technical membrane injury either is lifted off with the cli voce with a massive anterior hematoma or it actually becomes torn itself. Such as in this case where the technical membrane is torn and of course there's massive distraction cord injury and a big human homa uh and the musculature. So there is a spectrum of injury across the cranial cervical junction. We can have isolated muscular abnormalities, we can have ligaments abnormalities and involved a pickle ligament. We can have one joint that's disrupted. But whenever we get to where bilateral joints have disrupted or we have spinal cord injury or we have complete ao dislocations detectable membrane is always involved and we consider whenever the technical membrane is involved that we're moving from the stable to the unstable, stable spectrum. So all sectoral injuries also had a toe joint disruptions and all patients require fusion had electoral membrane injury in our study furthermore, when there's electoral membrane injury and they were not operated on and treated conservatively. The two or three patients that had this all had some degree of basilar impression. Um They didn't go on to have oversight instability and this settled down. But um we can see that um there is some a permanent change in the bony relationship whenever we have textural membrane involvement and trauma. So we despise this ratio when we looked at the ratio between the distance of C. 12 and 23. C 12 is distracted greater than 2.5 Times this uh the c. 2 3 distance. Then uh all these patients had electoral membrane abnormalities. So Here's an example where we have c. 1 to distraction. And this is distracted integral membrane injury. Really we think that it's because whenever there's laxity in the front and all these Children are actually supine when they got these X rays. So when they're supplying and detectable membrane is lax the back of the head, puts a little folk rem or um factor and clearly uh on top of c. one. And when the stabilizing membrane or ligament of detectable ligament is loose between the Oxford NC to this allows the C. One to be jacked up, thereby we see this distraction of C 12 as a relative comparison to see 23 indicative of anterior textural membrane injury. So this ratio is easily identifiable. We're not looking for the dense, we're not looking for the cli vous. And sometimes these really complicated uh patients with a bunch of lines and intubation. And also we're not measuring a distance, so eliminates the film distance variable in terms of the millimeters that we have talked about with the other measurements. And it allows us to identify technical manual brain injury on M. R. I. With 100% specificity. And we propose this as a criteria for oc to instability in Children. So in moving beyond trauma a bit, we're talking about the other different categories of reno cervical abnormality. This is a child with dysplasia whereby uh we can see that there is instability across the cranial cervical junction. Technical membranes lifted up. And this child has a positive of bone. As you can see it's all cartilage in the front and this required uh uh fusion. And these Children are highly unstable uh and they also have post zero compressive injury. So I always try to um do these cases um uh in the halo. So uh in terms of the skeletal dysplasia there was a market close patient, they have oc to instability like this uh laxity hyper plastic seed then for magnum as well see one stenosis. So uh they're very short stature and the scariest part of the operation for me is actually the flip. So we always do pre flip motor evoked baselines flip them in the halo. So they're completely stable and do the operation in the halo. Um and we do put the halo back on as a postoperative adjunct but they get it mostly because of the flip and not because of the additional rigidity that's necessarily required after we instrument them. So in terms of additional cranial cervical uh pathology one of the most challenging one is due to osteogenesis imperfecta whereby uh we have softening of the cranial cervical bones and the brain basically settles on top of C. Two. And this can be measured by a line from posteriors klein oy to the indian if it's less than three centimeters it's felt that we have um basilar impression. Uh So one of the largest series of literature's with by dr McKenzie's, a lot of these are reducible with traction if they're not reducible to the pathologies address concurrently with the anterior decompression, these Children don't have a problem with fusion but they're fused bone is also very soft. And unless you get rid of the anterior pathology even with the fusion they tend to gradually settle and um the goal of treatment family has no oftentimes is palliative and because over time uh the anterior pathology that gets worse and worse. And so I've always tried to um do a transferrable decompression on these um otherwise um it can become a problem years down the line. So we can also have um assimilation disorders whereby um uh the atlas is assimilated to the oxen put and this also causes an anterior pathology where the cli voce has a segmental abnormality which causes it to project the uh tip of sea to upwards. Another source of basilar impression if the cli voces settling down along the anterior part of C. One with a simulation of C. One into the cli voce. So this is a case of um anterior outlets assimilation. And we have the associated compression of the brainstem. And we know this is a severe compression of the brain cemetery because we also have a ceramics. Although this is not the most dramatic uh compression that we can see as illustrated by our other case. Previously we know that there is significant compression here because of the syringe that CSF dynamics is altered here. So this is where by the entire pathologies reduced by posterior open reduction and and fixation. And the sufferings of course results with uh and more normal um oh entire subarachnoid space and reduction of the vascular impression. So while we can have anterior segmental issues we can also have posterior segmental issues whereby the C. One is assimilated into the occipital back here and just can put uh abnormal stress or or abnormal development of this transverse ligament. And when you see this patient inflection we can see that there's a lentil axial instability here. This patient is treated with this construct. So in terms of surgical technique I think uh you know a trans particular screw is always nice and confers the best uh stability uh in terms of the uh C 12 fixation. Oftentimes we do have anatomy that is quite unsuitable for a either a harsh screw or a trans particular screw in the occipital the sea to construct. So dr wright came up with this technique whereby trans laminar screws are employed. C two obviously is the biggest spinals process in the cervical spine. This includes Children and they often have enough space to uh incorporate trans laminar screws. So this is our attempt at trans laminar screw and a very young child. You can see that there's significant crowding at the spinals process such as such that one of the screws uh is directed more financially and this patient could have a tiny little breach here. But the other screw uh is able to reach the length of the lamb mina. And this is the patient whereby the anterior pathology is again able to be reduced with trans laminar screws in the occipital cervical construct. So moving on to just uh beyond just talking about bony compression. Um We can often have ah chiari malformations whereby the entire posterior fossa is really involved in terms of there is the chiari which is the counselor Uh descent into the cervical spine. We also we know that the tonsils should end at the cervical spine or 4 mm above or below the frame and magnum. Um But oftentimes we just have a chiari malformation that we deal with surgically but oftentimes the chiari malformation comes with the bazaar and resignation and the plate in Bosnia. And and you can't just decompress is post clearly with a purely purely compressive operation. Uh This anterior pathology has to be addressed. So this is a case where the patient preoperative lee, you can see that there is existing anterior pathology. There's a significant chiari malformation, curious decompress and the mazar infection is much worse with cranial nerve dysfunction. So we would like to be able to predict this before we do a posterior decompression so that um we do have some measurements. Uh if the density is sticking back more than nine along the cliff level to see two lines have to worry that this patient will need a concurrent Fusion to prevent worsening of the anterior pathology or the Cliven angle is greater than 130° in terms of this flatness. This is another potential indicator that we all need to address. The anterior pathology uh concurrently either with a uh with a poster of fusion and open reduction of this. So here's an example of this 11 year old childhood chiari. We have the anterior pathology patient also had presented with downward nystagmus in a taxi. Um uh There's also some clip profile fusion here. Um ah But we were able to do AC. 3 uh lateral mass uh screws uh with occipet two CC three contract because of the fusion here um with a wire underneath, seek around the spinal process of C. Two. And you can see with just with this construct we're able to get a nice post decompression or reduction of the anterior pathology and a subsequent fusion. So just want to point out again that the bony relationships and ligaments integrity can be subtly manifested by a ceramics. What do we mean? This is a patient with anterior pathology. Ambassador impression between these two scans. You can see we've developed a significant ceramics. Well this means that this either the posterior composite uh chiari or the anterior relationships has worsened. So that CSF is now completely blocked from the cranial cervical junction and we can develop a searing. So when we look at progression of cranial cervical um abnormalities or um instability. We want to look at the neural elements and we want to not forget to scan the rest of the spine to look for our sufferings which could indicate progression of the cranial cervical pathology. So to summarize with basil impression and chiari, select the bazaar imagination and terra pathology with chiari one nr ceramics presents cranial cervical instability and they should be treated with post here open reduction infusion uh with the really scary interior pathology. I think we still would advocate the transfer of to me if um if um uh for me it's sometimes it's just the brainstem. It's just a ribbon. And um just doing a posterior reduction may not be enough or if something happens during surgery. just have no room, no margin of air talking a little bit about down syndrome, which of course can have instability at the cranial cervical junction or between C 12. We can have a lax transverse ligament, we can have a little motion greater than 10 millimeters And we can have court signal change from dense abnormalities. Or are also I think this is a very challenging group of patients when they have, when they need cranial cervical fusion or C12 fusion because we do know that they have a noted difficulty with grab graft, the re absorption and lack of of fusion and uh problems with non union. This is an example of a patient and they can present quite young. So this patient is four months of age and we have cranial cervical dislocation at this uh uh point already. And uh and a fusion was attempted posterior lee without instrumentation. Uh just halo uh with the C. One lemon ectomy of this has resulted in a non union. And then at 13 months I met these patients and we did a rib graft. We did micro plates and we did many craniofacial plates and screws to screw it in place. But you can see over time this graph still absorbed, we absorb and consequently we use bowman photogenic protein on this patient. This is the first reported case use of bowmore photogenic protein in a pediatric patient that we reported. And it's just you know, there was just um no other way to really achieve a fusion on this patient. And, yep so with the use of boom Morfogen IQ protein um we got a massive um fusion and so I was looking at this and I was like wow! Um it held this way, it didn't grow through the skin. So we can also have unstable also down 20. Um without down syndrome of course, where this patient has an unstable aas. So I'm showing this picture just to remind people that when we have scoliosis, it's not necessarily just a spine problem. We're mindful that keep the hydrocephalus here composite chiari can cause a serious and causes scoliosis. And this one patient is treated with endoscopic third ventricular qasemi whereby we diverted CSF through the base of the third ventricle and then the chiari resolved in the searing. Also resolved just talking a little bit more about chiari. Yes, I think it's very ah we have to be mindful when we're really sophisticated when we think about the differences and scoliosis, which this patient has a little bit that this patient actually has a syringe but we cannot find a chiari here. The council did not descend into the cervical spine and then um we're like, you know, with this image, it's just really hard to see with the BFF eF fiesta type of milligram image. And we just can't tell what's happening here. And why does this patient have scoliosis, Why does this patient have a chiari that won't go away. And we finally were able to do a cardiac gated image. And I'm just going to show us this real quick. That can show us that this in fact, is a membrane that we cannot see on traditional images. Uh but if we uh um gated it with uh we gated it with cardiac imaging, you can see that this is a membrane that would just like to act just like a chiari to disrupt the cranial cervical junction CSF demand which causes this patient's Syrians. So, this is a very cool way to image uh and CSF dynamics and the processes that kind of goes on in the cranial cervical junction of course beyond bony relationships. Right? Mm hmm. And this is the membrane that we can see inter operatively above this man's record. All right. So, in conclusion, there's a lot of cervical abnormalities in terms of the stability. We need to think of it as one unit, we need to think of its relationship to neurological structures. And we're not able to be really uh sophisticated and really be encompassing and holistic. If we just look at the bony relationship but just look at the intra intra spinal slash intracranial relationships. And we also have to think about CSF dynamics. So, thank you very much. Thank you for your attention and have a great day. Stay safe