So, the next speaker will be Dr. Wilson from Stanford. He's going to talk to us about the distal perineal nerve decompression after sciatic nerve injury secondary to total hipertroplasty. Great. Thank you. So, I'm going to talk about a study that we did looking at distal perineal nerve decompressions following sciatic nerve injuries after total hipertroplasties. I don't have any disclosures that are relevant for this talk except to say that since this abstract was submitted, this is now published in the Journal of Neurosurgery. So, it's available for review for anyone who's more interested. So, sciatic nerve injury is not uncommon with total hipertroplasty. It complicates about a half percent of all of them. And if we think about how many total hipertroplasties are done in this country, it's about 300,000. And so, that means if you just take that simple fact, over 1,500 sciatic nerves are going to be injured related to this procedure in our country on a yearly basis. So, this is a problem that we're going to commonly encounter. And the question is, how do we best treat this? And the major morbidity really results from the loss of perineal nerve innervated function. So, the foot drop is the major morbidity that's associated with these injuries. And for a number of reasons, the perineal division actually tends to be more commonly injured than the tibial division. Despite that, if they're injured equally, the morbidity still really results primarily from the perineal function. And so, that's oftentimes the target of what we're trying to treat. And unfortunately, recovery after these types of injuries is relatively poor. In the literature, the range varies from about a half to a third that recover to at least MRC grade 3 function, with most reporting on the low end of that. Most studies really report that it's about 30 to 35%. The average time to maximal recovery for these lesions is about a year and a half. For complete lesions and for partial lesions, it's roughly one year. So, we hypothesize that following proximal sciatic nerve injury that the common perineal nerve may become secondarily entrapped. So, similar to other types of proximal nerve injuries, when you result in paralysis that leads to soft tissue swelling or nerve injury itself leading to swelling of the nerve, nerves can potentially become entrapped at common entrapment sites. And so, in this particular injury, that would be at the fibular tunnel for the perineal nerve. And if this is an entrapment point following this type of injury, maybe this is serving as a barrier to potential axonal regeneration or even a potential site for conduction block. And so, the second part of the hypothesis was, well, if that's potentially the case, would a decompression of the common perineal nerve at the fibular tunnel relieve that entrapment and ultimately lead to better functional recovery? So, we reviewed a series out of two centers. This was done at the Mayo Clinic in Minnesota and at Washington University in St. Louis, and found a total of 53 patients who had a perineal nerve decompression at the fibular tunnel for this specific indication. We excluded any of the patients who had less than six months postoperative follow-up time, which left us with a total of 37 in the cohort that we ultimately reviewed. And for those 37 patients, the preoperative median dorsiflexion was MRC grade zero. And I'll point out a couple of other features, which is the average BMI for this group, for this cohort, was 30. One of the only prognostic factors that's been found in this group is that obesity seems to decrease the likelihood of good outcomes. And so, we have an obese cohort on average. And then the second thing is, as I pointed out previously, the average time to maximal recovery varies between about a year and a half after the injury, and the median time to decompression in these patients was slightly over a year. So, for the majority of these patients, they had had a fairly prolonged period where they were given an opportunity to show progressive improvement. The specific indications for surgery were not necessarily dictated, but both of the practices at both of the institutions was typically to look for a TINEL sign at the fibular neck as an indication that maybe there has been progressive recovery to that point, and that may be the point that now is entrapped and serving as a barrier. So, 73% of the population of the cohort had a TINEL sign. And then we also looked for any motor unit potential. So, even a single motor unit potential was considered positive for the purposes of this study. And we looked for those in the short head of the biceps, tibialis anterior, and the peroneus longus. So, when we looked at this cohort, we saw that a good number, 65% of these patients had good dorsiflexion outcome, which we considered to be MRC greater than or equal to 3 at their latest follow-up. And recovery to MRC at least 4- happened for 41% of patients, with the median dorsiflexion grade at latest follow-up being 3. So, we then wanted to look to see, well, could we tease this out a little bit further, and could we come up with anything that was predictive of which of these patients would go on to have a good surgical outcome? And we analyzed a variety of factors. And what we found was that preoperative motor unit potentials in either the tibialis anterior or the peroneus longus were the only predictors of what we analyzed as being predictors of a good surgical outcome. So, we think that this may represent an improvement in comparison to conservative management. So, this is one of the studies that summarizes the data that I presented in the kind of the introduction of this discussion. About 33% of patients managed nonoperatively demonstrate recovery with only as high as 50% in a couple of studies. I think the biggest critique of this study would be that we don't have a natural history comparison group. So, this is only a surgical arm. But if we think about comparing that to what's available in the literature, this does seem to represent an improvement in what's typically accomplished. The average time to maximum recovery's been shown to be a year and a half for complete lesions and a year for partial lesions. And again, the only identified risk factor for poor recovery is obesity. So, we may have a population here that was already predisposed to having poor outcomes, being obese, being more than a year out from their injury and not showing improvement. And so, we may actually have had a cohort that was already slanted towards poorer outcomes, and yet we still showed potentially better outcomes than what most natural history studies show. So, why decompress at the fibular tunnel? Well, this is a potential known point of compression. Paralysis may lead to chronic leg swelling, which may be the point of entrapment. This may serve as a barrier to axonal regeneration. And secondarily to that, this may also improve nerve glide, which is reduced after these types of injuries. So, I think at the end of the day, it's really a question of risk-reward. So, in this study, we didn't have any patients who had worsening neurologic function. We had only one patient who had a superficial wound infection that was treated with the only oral antibiotics. So, this overall seems to be a very low-risk procedure. And on the converse side of that, it may potentially have significant benefits. And so, when you're weighing the two of those against each other, this seems like a reasonable thing to consider. And the predictors that we found would be units in the peroneus longus and tibialis anterior. And the counterargument may be, well, maybe those are the patients that would have gone on to recover anyway. And I think that is a reasonable critique. But I think given the low risk of the operation and the potential benefits that we've shown, this may still be reasonable to consider, with the idea being that if at least they show units in the biceps, the short head of the biceps, peroneus longus or tibialis anterior, they've at least recovered beyond the initial site of injury. And so, logically, it may make sense that there's now a point of entrapment that you may benefit them from. So, with that, I'll thank you and take any questions. Thank you for that. I presume that those that recovered were already regenerating. And your evidence for that, although soft was Danell's, better was the MUP from one of the muscles. Did you, in this series, make any effort to visualize the injury itself by MRI, by ultrasound, by exploration? And then you did have some failures. Maybe if you had done something about the injury to begin with, you would have had those. So, why... I mean, look, I favor this procedure in which Jeremy Hill is involved at a proximal level. Don't misunderstand me, because Tano Malasi and I agreed years ago this was a good thing to do. But we both agreed that whenever you could, you should study the actual lesion, because there can be a suture around the nerve, there could be a fragment bone in the nerve, there could be a lot of things up there that would be helped by a more direct procedure. So, did you attempt to visualize the injury? Yeah, so these... Thank you for pointing that out. So, I didn't talk about it here, but the vast majority, I can't say all, I don't remember the number off the top of my head, but the vast majority of these patients had MR imaging or some sort of X-ray or CT to visualize to see if there is any extrinsic compression related to clip, suture, some sort of focal injury that could be identified. The real problem, though, is that the majority of these patients are referred to see us in a very delayed fashion. So, well after a year after their initial injury, and so targeting, the thought was targeting proximal sites of injury after a year may not be as beneficial, and so figuring out these people who have demonstrated that they've recovered beyond the initial site of injury, now maybe we can augment how they're recovering. I don't think this argues against the idea that you should explore proximally, particularly if they're referred early enough, and I think they may be complementary strategies. Yes, if I were an orthopedic surgeon, and my patient after a hip procedure woke up with paralysis of any kind, I would insist on some study to visualize the nerve, and I can speak from personal experience, because I woke up after my last hip was done with a complete femoral nerve palsy, and what I insisted on was the proper studies to look at my nerve. Fortunately, it didn't have to be reoperated on, it recovered, began to recover on day five. But, you know, now they're sent to Susan, or wherever you were, now why isn't she or you getting a study on them to see the injury? I don't understand that management, because you're going to have failures just with your simple decompression, and maybe if something was done to the injury itself, that would be less or non-existent. I don't know, I'm just sort of pursuing that line. Dr. Osegar. Just to comment a couple things. One is, many of these injuries involve both the tibial and the perineal components, and then those are really severe, because the loss of sensation on the sole of the foot can be a very bad problem in terms of ulceration and so forth, and loss of parts of the foot. It can be a very painful injury as well. I would expect those injuries to be worse, and perhaps fall in the category of the patient having no motor use potentials, and it might be hopeless to decompress the perineal nerve. Do you have any sense of how many of those patients received? Yeah, I would agree with that. I think that that tends to be true. We didn't analyze that as an independent predictor, but the overwhelming majority of these patients that were included in this study had normal or near-normal tibial function. So they were really predominant perineal nerve injuries. So you could at least conceivably consider something similar, actually, for the tibial nerve if you saw that there was recovery to decompression of the soleal sling or something. But I think that those injuries where you really have profound tibial and perineal nerve deficits tend to be very bad injuries and don't recover very well. So then I think you're really left with the idea of proximal exploration, if that's... In addition, repair of the sciatic nerve at the client level, even including the graft group, will provide plantar flexion in over 65% of patients as long as it's done within nine months of the injury. And you can look up our data on that. So with tibials involved, I think you've really got to think about dealing with which... Dr. Howard-Bergle. I just want to thank you for the paper. This has been my practice for a while, and I sort of try to explain to the patient the same thing a lot, because she will discuss. And again, most of my patients come with imaging, Dr. Klein. So the ones that are higher up, there's clearly something going on, and then you take care of it at the gluteal level. The ones where the MRI looks fine or the CT often, because they've got some hardware, and then you can see the nerve coming in and it looks okay, they clearly have evidence it's coming back. I often quote the Dellon paper. I don't know if you put that in your manuscript, where the... Did the animal study, cut the nerve on both sides, sew it back together, put a cup downstream, and the side that had the cup didn't recover as well. It's not a really strong statistical paper, but it is clinical evidence, I mean, a lab evidence. Conceptual evidence, yeah. Makes sense, too. One more comment with the proximal injury. When we look at a scenario like this, where we have motor units disabled, you've got a great deal of nerve, but you don't have a lot of energy, and it's not a very normal injury. It's a different scenario than when we have no axons, and we're worried about the generation from top down. We know there's got to be a component of the neuroflexic injury. So in that case, I think a decompression of the proximal injury, and reverse of the neuroflexic, we're not looking for axons to come down. Yeah. And I think the jury's still out. Like I said, I think these can be complementary techniques, potentially. Yeah. But a word of caution, though. The people that have done that study are used to do this procedure. That's correct. So out there, we need to be very careful, because we do see a lot of complications just for decompression from outside institutions. So we need to be very careful.

distal perineal nerve decompression

sciatic nerve injuries

total hip replacement surgeries

foot drop

recovery rate