Michael Trepal, DPM discusses the anatomy of the sesamoid complex and common dysfunctions associated with it. Dr Trepal also reviews common pathology as well as discusses treatment options and long term outcomes.
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Michael Trepal, DPM
Vice President for Academic Affairs
Dean and Professor
Department of Surgery
New York College of Podiatric Medicine
New York, NY
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Male Speaker: Next speaker will continue this process of experience. That’s Dr. Michael Trepal. Dr. Trepal is a professor of surgery at the New York College of Podiatric Medicine and serves as the Vice President for Academic Affairs. He is a Clinical Assistant Professor in the Department of Surgery at New York Medical College and Clinical Assistant Professor in the Department of Orthopedics of Surgery at SUNY Downstate. I have known Dr. Trepal in his capacity as vice president for academic affairs at New York College. He has certainly attempted to elevate the level of education for our students and make our profession proud of what podiatric medicine and education is all about. He certainly has done things internationally and always bring something to the table when we ask him to speak. Today we’ve asked Dr. Trepal to talk on sesamoid function. There’s two little Ps on the bottom that can create major havoc. Please welcome Dr. Michael Trepal.
Dr. Michael Trepal: Thank you Dr. Schoenhaus for that very nice introduction. As I’ve mentioned yesterday, I want to thank the committee, the scientific committee and the organizers from PRESENT for facilitating this collaboration between the New York College, which has served as the scientific sponsor towards the [ME] [01:32] credits of this meeting for a couple of years now. But this year, the PRESENT has gone much further and that is facilitated what we’re calling the Second International Transatlantic Seminar, the NYCPM entered into a very, very productive affiliation with National University of Ireland Podiatry College, one of many international affiliations that we have. The world is a small place. Inter-collegiality and professional discourse back and forth is a wonderful opportunity to share knowledge and to educate each other. You will see over the course of this meeting several exceptional speakers, colleagues from across the pond who have come over here to share their great wealth of knowledge. I know you’ve got already some of the lectures already and those that you’re going to go get will greatly add to this collaboration into this great meeting. So today I’m asked to speak upon the sesamoid complex. These little guys on the bottom of the foot as Dr. Schoenhaus said can really create some havoc here. I have no financial relationship related to this lecture. We have several objectives here to talk about anatomy and functions, some of the pathology associated with it, and then describe some of the strategies to deal with this. Sesamoid is a bone embedded within the tendon. The granddaddy sesamoid, although we don’t usually think of it that way, is the patella. Sesamoid bone has a mechanical function. It’s designed to alter the pole of the tendon. It’s designed to change the angle of inclination of the tendon. It prevents it from flapping the tendon as it goes across the joint. So it adds an increased propulsive capability in the foot at the first MTPJ and also at the knee in the form of the patella. Now thankful that we’re not a horse because when a horse fractures its sesamoid, it’s shut. Some of the horse fans may remember back in 1975, Ruffian was going to – I think they made a movie about this horse too. But Ruffian was going to be the American Pharaoh of today. All set to win the triple crown and that while running around the track at Belmont, fractured the sesamoid which sits up higher in the horse’s hoof. And you can see in the lower right hand side there what the result of the fractured sesamoid was to Ruffian. Now some of the patients that we treat with sesamoid disease you might wish to do the same thing. But it might get rid of the problem for that patient but not necessarily the best. Sesamoids have an interesting history. Named way back 2000 years ago by Galen because it resembled the sesame seed. That’s where it comes from. It has some interesting attributions associated with it. In fact, going back into some Jewish theology, it has actually been referred to as the luz bone, representing the repository of the soul after death. So people think there are brains or something in their feet. Maybe there’s something to it. It appears embryologically in the 8th week of fetal development. It starts to countrify about somewhere around the 12th week and then fully ossifies during 8 to 12 years of age.
Now there’s variations in this ontological process. If you have any aberration or within ontogeny you get failure to fusion and you still have to get morphological changes within that sesamoid. Not worst case but extreme case scenario, it fails to ossify completely. So there you would have a congenital absence of the sesamoid but much more commonly the ossification centers failed to unite and you can get various patterns of bipartism or tripartism or quadropart – I’ve seen as much as four. I have never seen a five partite sesamoid. Interestingly enough, there’s this high correlation of bipartite medial sesamoids and feet with hallux valgus as compared to normal feet. Now a caution, again when you review literature, don’t confuse correlation with causation. The fact that you see a higher incidence of bipartite sesamoids in patients with hallux valgus, it’s not enough to take the next step to say that course did one way or the other. Maybe the hallux valgus goes—well, was hardly the bipartism. But it correlates but necessarily been proved as a causative factor. Again here’s an extreme case of failure to ossify resulting in a congenital absence of the sesamoid. Here’s a congenital absent tibial sesamoid whether that had an effect on the derivation or the contribution to the derivation of the bunion in that, I’ll let you decide. But certainly I think it’s reasonable to conclude that it did. And the adult anatomy in the sesamoid I think were fairly – should be fairly adept at understanding its rich investiture of ligaments, the adductor tendon, the abductor tendon, the two branches of the flexor hallucis brevis, its relationship to the crista. It’s very important function because we do a lot of surgery over there. Also there is a rich vascular plexus around those sesamoids. If you look in the right hand side there, if you look down in the interspace there, we do a lot of surgery. We monkey around a lot in the interspace and it’s that branch of the first metatarsal artery that’s sitting right lateral to the fibula sesamoid that frequently gets bagged if you’re going to be sticking a scalpel down in that area. Now I’ve waxed and waned over the years about the need for doing fibula sesamoidectomy as part of bunion procedures and I’m at the leave them alone stage unless there’s grossly arthritic pain directly attributable to it. One of the reasons is because of disruption of the vasculature down in there. We’ll talk about others in a few minutes. Now again we talked about the sesamoids as their main function of stability of the joint. It is for propulsion to occur. It’s critically important that first dynamically the flexor hallucis brevis stabilizes the proximal phalanx against the metatarsal. Secondarily you get the flexor hallucis longus who will then stabilize the distal phalange across the proximal phalange. So there is a dynamic phase here of which those muscles fire in sequential order. The sesamoids provide the mechanical advantages for that to occur. So pathomechanically when the sesamoid or the flexor brevis is not functioning, the first step that you see is the dorsiflexion of the proximal phalange. This is the development of the hammed hallux. This is what can happen when the sesamoidal complex goes array. There’s lots of other cause there. You get dorsiflexion in the proximal phalanx. Secondary overpull of the flexus longus. Secondary overpull of extensor hallucis. Therefore you end up with that progressive hallux hammertoe. If you look at this, again I’m not going to talk too much about sesamoids and bunion surgery. That’s another talk at another time. But all too frequently we think that the sesamoid is just the sesamoid moving laterally and we all too frequently forget about the position of the first metatarsal in the frontal plane that it rotates. We look to plantar flex at the sagittal plane and we certainly look to correct the first metatarsal on the transverse plane. But we all too infrequently look to correct it on the frontal plane. Is it that the sesamoid has rotated around the hallux laterally? Or has the metatarsal rotated in the frontal plane among the sesamoidal complex? Again, we can talk about this in another time, another place about how derotating the capital fragment is part of a bunion procedure. We’ll put lot of talks about this routinely and then this preoperative analysis of it. But think that in mind when you’re looking at this. Now, what can happen? Sesamoids that disappear, this patient here would give anything to get their sesamoid back. So with this one.
Give me my sesamoid back because they create an obvious stability about the joint and missing them kind of lead to bad things. Terms of our clinical examination in evaluating these patients, everything starts at chair side. Proper palpation. There’s a lot of entities that can create pain about the first metatarsal phalangeal joint. How many times have you had a patient referred to you? The PCPs and the intern, is any pain around the first MPJ automatically is gout. Patients come in and where does it hurt? It hurts on the bottom. Who told you you had gout? My internist. Nothing can be further from the truth. We need to palpate this area very carefully, each sesamoid individually to see what you’re looking at. Look at the patient superstructurally. If things just don’t stop, we can’t have tunnel vision and just look at the foot. Examine the shoe. Understand their weight-bearing capability. Imaging studies, certainly for traditional x-rays, you want to get a DP. You want to get a lateral view and you want to get an axial view to see what the sesamoids and what the metatarsal sesamoidal complex is doing on the frontal plane. What is the relationship of the sesamoids to the crista? Of course we have advanced imaging studies that are available to us. MRI imaging. I always like to make a point to mark for vitamin E capsule or ask the radiologist to mark the point of pain to see exactly what structurally is happening in relationship to where the patient’s complaint is. CT scans can be also utilize. Again, you can get all kinds of fancy. Sometimes they don’t give you much more information other than to jack up the radiology bill considerably. But again, if we’re looking at cortical issues, I think CT can give you a wealth of information. As I get better with ultrasound, I’m using it more frequently, there’s a steep learning curve there, certainly have not plateaued in my own ability to do this and to comprehend it. One thing that I know, if I’m going to understand the image, I have to be the technician to take this. The other thing that you can do with ultrasound is you can get real-time movement here. You can put the joint for range of motion. You can dorsiflex, plantarflex the first metatarsal phalangeal joint and see if – you need to do two planes. You want to do a transverse plane and a longitudinal plane over the sesamoid to give you about the most information. But clearly I’m not there yet to have total confidence in my capability to do it but I think I’m making progress. Additional test to see how the patient functions. If you have access to computerized gate analysis, use it. Whether it’s in your own office, I know this tends to be an expensive thing or someone else’s, it can give you a wealth of information as to how that foot is functioning. Here’s an example of a patient who came in. You would think that this foot is overloading. Look at that lesion. But it didn’t gel. You got a bunion deformity there. You got a hypermobile first ray. That didn’t make sense that that was overloading to me underneath it. Again, see the patient standing. That’s certainly a hypermobile first ray. The first metatarsal is deviating dorsally and medially. So we got the computerized gait. Surely, well I look it as the propulsive stance there on this. We don’t have a lot of time to go onto these numbers. But if you look at the propulsive phase propulsion between the left and the right foot, you can see that on the left-hand side I think it’s 34% on the left-hand foot, underneath the metatarsal during the propulsive phase. Only 17% on the right side under the foot. This is not lowering. This was a structural problem. It was not a functional problem. It wasn’t going to necessarily solve this with an orthotic or anything else. This was a structural problem. The alignment of that sesamoid underneath the crista and the hypertrophic sesamoid. So use all the modalities that we have available to do it. There is a whole host. Larry Olorf wrote an article describing all the vast pathologies that affect this. Sometimes it’s very difficult. The main categories of degenerative joint disease. Good old garden variety osteoarthritis of it. Wear and tear of it. Excessive loading. First MTPJ dysfunction ends up with degenerative joint disease of the sesamoidal complex. Not surprising that this patient would have sesamoid pain looking at an x-ray that looks like that. Again, the radiologist, if you send out to a good imaging center, they’re going to confirm in their radiology report your diagnosis of it. An example of chronic fragmentation of the fibula sesamoid that wasn’t quite demonstrable on traditional x-ray.
So utilizing the imaging studies can help to really pinpoint where and exactly this correlate, where this patient’s plantar metatarsal pain was occurring. Common fractures. But these are frequently misdiagnosed. A non-foot expert. A patient goes into the emergency room. A first year medical resident looks at a bipartide sesamoid and it immediately calls it a fracture when indeed that’s not the fact what the patient had. I think we all know that when you’re looking at an x-ray and again this is why it’s important to take multiple views, look at the irregularity on the upper right-hand screen. More consistent with a fracture as opposed to a bipartite sesamoid. Again, transition overtime. If it’s a fracture and you have serial x-rays, you’re going to see healing of it overtime. Again, fracture, irregularity there on the imaging. If you’re going to go towards T1 and T2 and you compare it, you’re going to see the acute inflammation that you see in the upper right-hand screen on a T2 image. T1 image, you’re going to see that dark line there as you notice in the upper left-hand screen. So we need to differentiate fracture versus bipartitism. When you look at it in addition to the history of acute trauma or something else, you’re going to be evaluating the ends of the two fragments there. In a bipartite situation they’re going to be more rounded as opposed to a fracture. Avascular necrosis of it can occur. It goes by several names. We’re probably talking about the same condition whether you call it osteonecrosis, osteocondrosis, or an osteochondritis. Overload. This is a mechanical problem. More often you’re going to see the sesamoid in a plantarflexed first ray. Or biomechanically perhaps the problem is in the second metatarsal that is elevated. Or perhaps iatrogenically by prior excision. Sesamoiditis is a waste basket term. It has an ICDE 10 hour code associated with it. That’s a generic term to describe pain in about the sesamoid and frequently using cases where you don’t – it’s a waste basket term, like metatarsalgia. Soft tissue injury. This was a hyperextension of the joint, the intersesamoidal ligament ruptured. You can see the diastasis of the two sesamoids together. So this brings us now to treatment. What do we do? Making the diagnosis as the first leg here. First obviously you want to treat the underlying cause if possible. Generally speaking if there’s pain, we try to offload it. We can inject with anti-inflammatories. We can surgically excise. Described in the literature but less frequently performed procedures of shaving, grafting, or in some cases for fracture, open reduction and internal fixation. I think nobody knows better than us as podiatric physicians and surgeons back to the good old days about how we can offload through functional foot orthosis through garden variety paddings, get to offload it. Injections of steroid. Ultrasound guidance can help you. I think again it’s a learning curve here. But if you have it available and you can use it, I think you can be more precise in your placement of your injection into the exact area. Terms of surgical excision of it, one or two tibial, fibula or other, it’s with caution I think. Getting down there into the interspace is not an easy thing, particularly if the sesamoid is arthritic. It can be a brutal procedure. It can be very tugging and grasping and yanking out it. As I said, I used to do it pretty routinely with bunions and now is the exception rather than the rule for me. I’m much more interested in derotating the metatarsal head and putting the metatarsal back on the sesamoid rather than taking it out. One of the tricks I now do is an article I read back about 10 years ago and that’s the joystick method. To get that sesamoid out, take a Steinmann pin or a thick K-wire and shish kebab that sesamoid and then you can use it as a joystick to kind of rotate it and to sever all the sesamoid. I think if you use this, you’ll find it’s fairly effective in doing it. When excising the tibial sesamoid, we’re generally going to do it more from a medial approach than in a plantar approach although you can do it plantarly. Of course we want to be careful of destabilizing the first metatarsal phalangeal joint with the fear of developing a hallux valgus deformity. So there is our approach there. You see the sesamoid underneath it. This particular patient, the tibial sesamoid was the culprit. A V-shaped capsulotomy is my procedure of choice.
I can then imbricate it postoperatively after the sesamoid it removed. I can imbricate the capsule, tighten up, do a capsulorrhaphy immediately. Now, the incidents of hallux abductus following tibial sesamoid, not a lot of great literature out there about it. This one, again retrospective. Very small power. Eight out of 19 developed HIV. 42%. That’s a decent number of a complication. So you want to make sure that the sesamoid really needs to come out. This is 2005. Again, retrospective level four evidence. Isolated tibial sesamoidectomies. Fairly high power. 229. Only follow up on 32. The procedure used a medial approach with the repair of the FHB. They looked at the short form 36 course in the study and they found in this particular which was probably a better quality or better powered study, no incidents of HIV. Looking at the time to work. In 26 procedures, seeing that the quickest return to work was a fibula for a plantar lateral approach. The longest was taking out the tibial. In taking out the tibial and fibular sesamoids, one needs to be careful because you’re destabilizing it and almost in variably if you don’t do anything else, will end up with a clawed hallux or hallux malleus for sure in that. Generally if you’re going to take out both, you need to get strong consideration to fusing the hallux into phalangeal joint at the same time because what you’re doing is converting that into a rigid lever. Tag it all in foot and ankle. Retrospective review. Removing both sesamoids in 36 feet as a primary treatment for hallux valgus noted no deleterious. Again, I want to just leave with this one last thing. Total sesamoidectomy for painful hallux rigidus. Destabilizing the joint, removing the pressure of the interosseous pressure on that as a primary treatment for hallux rigidus, not for the other indications. This is the only article I could find about it. Again, for a medial incision and reported no incidents of hallux malleus which I find hard to believe. So we talked about sesamoids, anatomies, some of the functions, some of the diagnostic capabilities, some of the cautions and some of the treatment approaches that we have and I thank you very much for you time.