David Davidson, DPM provides a detailed look at the path physiology of the lesser metatarsal phalangeal joint. Dr Davidson will also review common diseases of the joint as well as treatment options currently available.
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David Davidson, DPM
Center for Wound Care & Hyperbaric Medicine
Degraff Memorial Hospital
Buffalo, New York
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David Davidson Dr. Davidson has disclosed that he is a Consultant/Advisor and is an independent contractor for Vilex, KCI and Advanced BioHealing
Male Speaker: Given by a good friend of mine from Buffalo, New York, David Davidson. He loves the snow that’s why he’s out there. He treats a lot of fractures, a lot of disorders of the forefoot, rearfoot, ankle. He has been on our lecture platform a number of times. You’ll find him very entertaining, very educational, very enlightening. Dr. Davidson is going to share some thoughts on the Treatment of Lesser Metatarsal Phalangeal Disease. Please welcome Dr. Davidson.
David Davidson: Thank you. It doesn’t feel like 2:00 but it must be because that was my original time. I applaud you. It is 5:00, almost and I applaud for your stamina. I, again, Harold, thank you for inviting me to be here again. This is an outstanding meeting and the turnout is just mind boggling as always. I want to talk to you a little bit. I want to give you a review of some of the lesser metatarsal problems that we see, and you’re going to see, and you’re probably seeing already in your program. Basically, before we talk about the disease, we really have to review some of the anatomy and pathophysiology of the lesser MP joints. We have to go back to our first year at school, anatomy. The lesser MP joint is really a very intricate structure. First of all, the position of the toes is maintained by the balance between the extrinsic and intrinsic muscles and combination with what we call passive restraints. I’m going to go quickly because I know you guys are very knowledgeable. There’ll be a test after. The extrinsic EDL becomes that central dorsal structure of each toe, slip inserts into the base of the mid phalanx. There’s two lateral slips that we join to attach into the base of the distal phalanx. The central position of the extensor digitorum longus is maintained by a hood. The brevis attaches to the long extensors at the MP joint. That hood, by the way, dorsiflex that MP joint during gait. Of course, then we have the FDL which inserts down the plantar into the bases of the distal phalanges of each of the lesser toes. The brevis divides and inserts into the center of the mid phalanx. Both those tendons flex the distal and proximal IP joints. The interosseous muscles, which I never really quite understood as I were studying it and I probably still don’t understand at all. The interosseous muscle inserts into the base of the proximal phalanx and into the plantar plate. We’re going to talk about plantar plate in a few minutes and that extensor sling. Of course, the other muscles I didn’t quite understand in school, the lumbricals which insert into the extensor sling. The extrinsic tendons passed plantar to the axis of motion acting as flexors, and of course, the plantar plate that we’ve all heard so much about. Recently, there’s been some really good innovations in surgical and the surgical approach to repair this, which we’ll talk about. It basically provides resistance to hyperextension. Now, we talk about the plantar fat pad a lot. We talk about it a lot usually when we’re talking about heel pain. Don’t forget that the plantar fat pad is really important in the whole plantar surface of the foot, especially at the MP joints, because that fat pad dissipates the stresses of standing and in ambulation. As we get older, the first thing we lose is the plantar fat pad. We see a lot of these elderly people basically just walking on those metatarsal heads, which creates a huge problem. Those dynamic forces act to maintain the position of the proximal phalanx at the head of the metatarsal. There really is a very delicate balance between the extensor to determine longus and those recurrent extrinsic muscles. Changes can occur. If we don’t have that balance, changes can occur as a result of deformity, some sort of altered function of the stabilizing structures. There can be an external event. As you can see here, systemic, multiple systemic, we’ll talk about that. For example, synovitis, peripheral synovitis. When you’re looking at the MP joints, how do we do this? This is pretty basic. But I’ll go through this again really rapidly here. Physical exam inspection, what’s the position of the IP joints? What’s the position of the toe and the metatarsal? Is there dorsal keratoses? Are there plantar keratoses? On palpation, are there soft tissue masses? Is there a bony prominence? Is there a flexible or rigid digital deformity? If you really have those experienced fingers, you can actually palpate thickened synovium in chronic problems.
Of course, stability, the anterior drawer test which we talk about at the ankle, we rarely talk about at the MP joints, but it still is a test that we use to easily to determine whether that joint is stable or it’s not. Some causes of acquired subluxation of that MP joint. Neuromuscular disorders, such as you can see, systemic inflammatory disorders such as RA, other calcium deficiency disorders, diabetic neuropathy, et cetera, and of course abnormal biomechanics and avascular necrosis, better known as Freiberg’s infraction of the lesser MP joint, and of course, posttraumatic syndrome. Freiberg’s infraction, first described in 1914 by Dr. Albert Freiberg, where he described a collapse of the articular surface of the second metatarsal head. The original article talked about six cases of young women that presented with painful gait and localized discomfort at the second MP joint. All six cases had very similar radiographic findings, which basically show what he described again as collapse of the articular surface of the metatarsal head. In three of the six patients, there were loose bodies in the joint. Many people felt then and still feel that the inciting events, the cause of aseptic necrosis was some sort of injury to the blood supply of the metatarsal head during the growth phase, but we’re really not quite sure. It is seldom associated with any other systemic problem as other types of avascular necrosis could be. Interesting, you need to understand that the cartilage that’s destroyed during Freiberg’s is basically just the dorsal third of the metatarsal head where you can see especially with the picture on your right, that the cartilage of that metatarsal head, I don’t know if you could see this. I should have probably made this larger. But this Freiberg’s infraction metatarsal head, severely deformed cartilage of the dorsal third of the metatarsal head, the plantar surface has perfectly smooth cartilage. Case history, 16-year-old female with the chief complaint of second MP joint pain. Onset, two years before she came so see me, she’s had history of digital fractures, toe-off pain during running became increasingly more difficult which is why she came into the office. There was minimal response to conservative treatment, which basically was offloading that joint. Past medical history is unremarkable. She did have limited motion of the second MP joint. She had effusion but no instability. She had pain when you really push out, get up on the toes, and hyperpronated feet, which basically was not contributory to the Freiberg’s. Differential diagnoses, you can see the list. The usual diagnosis testing are simple x-rays, MRI maybe, diagnostic injections. You could in fact, if you’re not sure whether this is a mechanical problem or a structural problem or an inflammatory problem, not a problem with you giving a steroid injection to see the response. If it’s strictly inflammation, obviously their pain is going to go away. This is a pretty typical x-ray of a Freiberg’s. MRI, as you can see, not the greatest pictures in the world but you can see deterioration of the articular surface of the second metatarsal head. Diagnosis basically was stage 2 Freiberg’s disease. Again, conservative treatment failed. The question is how are we going to resolve this surgically? My friend, Rich Bouche, who's a colleague of ours in Seattle, that’s a napkin from the restaurant where he was sitting once, trying to figure how he was going to resolve this Freiberg’s infraction patient surgically, took a picture of this napkin. Basically, you can see, remember we said with Freiberg’s, the dorsal metatarsal cartilage is destroyed. The plantar 2/3 is perfectly smooth. What the procedure was, doing a V-osteotomy.
As you can see by that top picture on the napkin, tilting the bone up, so you’re now bringing the normal plantar articular surface dorsally which can articulate with the toe, then sliding it down and fixating it to have a relatively normal weightbearing surface. That’s exactly what we did. We did an osteotomy, tilted it up and put a screw in to hold it in place. What we’re doing is taking the metatarsal head, the cartilage is normal down here, tilting it up so now normal cartilage is adjacent to the base of the proximal phalanx, pre and post. We talked about soft tissue injury. Obviously, any kind of trauma may disrupt that balance we talked about when we showed you those boring anatomy slides, leading to abnormal wear and tear, plantar plate tear. Another case history, 36-year-old female who was referred to me because of a rather significant second MP joint deformity with concurrent pain. Onset, six months. This lady was line dancing, developed sudden onset pain, pain with prolonged walking had become more severe. Her past medical history also was unremarkable. Limited range of motion. She definitely had a joint effusion and significant instability and pain with active motion of course as I said before. Again, differential diagnosis is pretty much the same. Plantar plates here is virtually impossible to determine. It’s basically an objective diagnosis. X-rays aren’t going to show you much except you can see a little bit of instability of that MP joint. MRIs, if you suspect a plantar plate tear and you ordered an MR, my suggestion is make sure the radiologist knows that that’s what you’re suspecting because even an MRI, it’s very difficult sometimes to determine a plantar plate tear. Treatment options for plantar plate tear obviously are rest and immobilization, offloading with shoe modifications or orthotics, physical therapy. Steroid injections is in there because there’s literature that shows that, although I’m leery of giving steroid injections, a lot of steroid injections in and around the MP joints for obvious reasons. Steroid injections, repeated steroid injections frequently will cause problems with the musculature, the balance between. You can get tears of the lumbricals interosseous and sometimes plantar plate tears as a result of a steroid injection, nonsteroidal anti-inflammatory of course or surgery. This is not an incision, but this is the patient’s plantar plate. What we used to do to repair this is a plantar incision. I’m never unhappy with doing plantar incisions for anything as long as you’re doing it carefully. This incision is distal to the weightbearing surface of the metatarsophalangeal joint. But clearly, you can see there’s a very extreme longitudinal tear. There’s a system for plantar plate tears, grade 0, 1, 2, 3 and 4. I guess we have a grading system for just about anything in medicine these days. Arthrex came out with a really good surgical technique to repair plantar plate through a dorsal incision. It’s basically doing a Weil osteotomy, retracting, just opening up that MP joint space enough so you can visualize the plantar plate. They have really good instrumentation now that will allow you to grab that plantar plate and suture it to the base of the proximal phalanx. It’s a really good surgical technique. I suggest there’s a rather long learning curve to this procedure. I think most of the companies have labs that will certainly be able to bring their equipment and to have you use it. It’s a relatively new surgical technique to avoid the plantar incision if you’re worried about plantar incisions I guess. Systemic inflammatory disorders, the most prominent that we see is rheumatoid arthritic problems with psoriatic problems, lupus and other seronegative diseases. Basically, it’s the inflammatory arthritis causes actual damage to the cartilage erosion as well as damage to the adjacent musculature, which results in joint deformity or loss of function.
Posttraumatic syndrome, we know that direct injury to the joint may frequently damage the cartilage. You may have fragmentation. It’s going to create abnormal joint mechanics. You get swelling, tenderness, pain, joint instability and trauma leads to what we call posttraumatic arthritis. Treatment options of course are rest, immobilization, modifications to the shoes, orthotics, physical therapy, again, the dreaded steroid injections which usually I stay away from, and nonsteroidal anti-inflammatories or surgical intervention if necessary. All types of orthotics, all types of pads, gel pads, and so forth to balance the MP joints if we have to, digital crests we use frequently as in the lower right. The surgical options for this type of deformity are arthroplasty, metatarsal head resection with or without the base, and don’t shudder when you see those because I see this all the time from our orthopedic colleagues, arthrodesis or joint replacements. The problem is if you resect all the metatarsal heads and/or resect all the phalangeal bases, this is the kind of a picture you’re going to see. What are we going to have as a result? Well, we’re really going to have a very unstable foot and a very poor cosmetic result. Both of these procedures create significant instability. Arthrodesis of the lesser MP joints is not written out very much, but I’m starting to see more and more of the companies come out with new products, special staples which you can use, but this is a easy way to fuse the joint and it has a really good, with compression staple, and you really can get a relatively decent clinical result. Understand if you’re fusing this kind of a joint, you’re eliminating any kind of normal function through that joint, so you need to compensate with the patient for that limitation of function. Joint replacement at the lesser MP joints is really quite common. You have a choice of the base of the phalanx or the head of the lesser metatarsal. This is just the Vilex tray, which is out there, you could take a look at. We’re going to use this tray in one of our workshops tomorrow morning. It has both types, both phalangeal bases or metatarsal head components to it. Really, a pretty simple procedure and there’s very similar products from some of the other companies. Quickly, linear incision, expose the joint, longitudinal incision through the capsule to expose the metatarsal head, expose the metatarsal head and remodel it. Remove any dorsal spurs there are. Then, in this case, we’re using a phalangeal base. We’re resecting the base of the phalanx. The Vilex system uses a guide wire that we put through the center parallel to the shaft to the proximal phalanx. This is observed with fluoroscopy to make sure that that K-wire is driven right through the center portion of the bone and it’s parallel. All the proper implants slides over the guide wire and the implants screwed into the phalangeal base. That’s our final look. Just like first MP joint or any other joint, if you remove one side of the joint and replace it with metal or titanium, you basically eliminate the bone against bone contact, and therefore, eliminating the discomfort that the patient has. This is the preop dorsal view. You can see the deformity of the second metatarsal head. This is the reshaped metatarsal head with the phalangeal component in place. There’s a metatarsal head component which is placed into the head of the metatarsal very similar to the way it’s done in the base of the phalanx. Which do you choose? Do you choose the metatarsal base? Do you choose the metatarsal head? In my experience, with lesser MP joints as well as first MP joint, the phalangeal base is technically a much easier procedure to do than the metatarsal component. I choose to, most of the time, do a phalangeal base component, understanding that whether you just have to eliminate one side of the joint to eliminate the patient’s symptoms.
Many of our colleagues will tell you that they choose the side of the joint that is most deformed. That basically is a very quick review of lesser MP joint pathologies and treatment. I hope this will drive you all back to your books to relearn the anatomy and function. As I said earlier, the lesser MP joints are balanced very difficult. It’s very intriguing balance of soft tissue and bone to create really good stable, stable MP joints. Thank you.