Robert Frykberg, DPM, MPH discusses the key determinants in accurately selecting the best level of amputation for the diabetic neuropathic foot infection as well as important risk factors to consider when surgically planning a transmetatarsal amputation.
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MALE SPEAKER: The transmetatarsal amputation has been called the diabetic’s operation. Where I trained back in Boston, this was the operation du jour as we’ll go over. The transmetatarsal amputation as I tell my patients has saved tens of thousands of legs currently and before the onset or the incidence of modern day revascularization. Where I trained, it was a critical part of our management and where I trained, the originators of this operation had trained my surgeons who trained me. So transmetatarsal amputation is near and dear to my heart.
We showed this already. I don’t need to belabor the fact that you have to evaluate your patients and understand the underlying pathophysiology inherent in all of these patients. You must recognize these risk factors, these problems and especially underlying vascular disease as well as infection. I’m sorry. That’s not projecting as well as I like to be. Anyway, these are complicated patients and as you’ve heard, many of our operations fail and they fail because we haven’t properly assessed our patients.
I showed this to you earlier already and it bears repeating, risk factors: neuropathy, ischemia, infection, ulceration. Any risk factor for ulceration is also a risk factor for subsequent amputation and vice-versa, okay? We saw the stairway to amputation. I’m sorry, there’s so many repeats in here. But maybe it’ll serve you well. I learn by repetition. So maybe you can, too. And remember that amputations are limb salvaging procedures. I used to think they were failures.
In one regard, they can be considered failures for us, but they are limb salvaging procedures. [00:02:02] As long as you can intervene along one of these stairways or one of these paths to amputation so that you can limit the amount of tissue loss and limit the extent of the amputation necessary. As Dr. Marino had just said, you want to limit your amputation as distal as possible because the more proximal you get, the more complications will ensue.
So what are the indications for a diabetic LEA or a limb amputation? Fulminant infection, chronic osteomyelitis, very, very, very common, gangrene or chronic ulceration with underlying osteomyelitis, extensive tissue loss, non-reconstructable ischemia in the presence of a chronic wound or gangrene and sometimes even severe deformity or instability.
I’ve done ankle level amputations on patients with chronic, unstable Charcot ankles where they might have failed previous reconstructions or became infected. And so it’s a difficult decision to make, but it’s a decision that needs to be made for the benefit of the patient. I think Dr. Anderson made a good point earlier. You have to keep track of the time and when is it best to say, “It’s time to amputate. We’ve tried enough things. You need to get on with your lifestyle.” And many times, the amputation, even if it’s a major amputation is the best thing for the patient. Our business is to try to avoid major amputation and we work very diligently in that regard.
The key determinants for level selection and success at these levels are of course peripheral arterial disease. Generally, we certainly want an ABI higher than 0.5, but this was just a classic one in the literature. [00:04:01] Unfortunately, we’re often operating on people with ABIs even post-revascularization of 0.6 or 0.7. TcPO2, greater than 30, these are from the literature. These are cutoff points that can predict success or failure. Skin perfusion pressure also 30 millimeters or higher, that’s the cutoff point. Pulse volume recording, very, very accurate, it’s an old method which I always rely on in conjunction with these other methods and I really use pulse volume recordings at the level that I’m assessing or predicting that I will do the amputation to determine whether or not it has a good chance of healing and that goes back to the old Gary Givens study in 1979.
Obviously, infection, major key determinant, you want to make sure of course that the level that you’re amputating is free from infection. That’s why generally we do these operations in stages. We control infection first with an open amputation or a drainage or what have you. Once we’ve got things under control, we do our revascularizations. We make our assessments. We do our advanced imaging and then make I hope an educated decision on to the level that would best suit these patients. And of course, gangrene, tissue loss also determines a level of your amputation.
So the TMA was popularized by McKittricks… the McKittrick brothers in Boston in the Annals of Surgery in 1949. These were the days before revascularization and they proposed this diabetics operation for severe forefoot ischemia, forefoot sepsis, single or multiple gangrenous toes, partial prior amputations of the foot and for primary closure of difficult wounds. [00:06:00] And many times we’ll use the TMA to close large defects of the forefoot that were necessitated by infection or amputation and will use the TMA with a long flap to primarily close over these wounds. So it’s been very valuable in that regard. And more often than not, we’re doing the procedures for that very reason.
So the largest study to date, believe it or not, is the McKittrick study published in 1949. There is the series of the initial 215 TMA patients. Remember, they did TMAs rather than the more or the lesser procedures that we would do now like toe amputations or ray amputations after revascularization because they didn’t have revascularization. So even the gangrenous or infected toe… great toe could lead to a TMA because they would assess that carefully and if there was no rubor or infection in the area of the TMA, that’s where they would go and they were very successful on that regard.
They reported a long-term success in 67% of cases over two years. They did have their failures, of course, requiring proximal amputation or early death. Remember, this was in the ‘40s. Then, the functional results were deemed excellent. They didn’t have special footwear, but they treated them with lambswool. They were very careful. Remember, this is at the Deaconess Hospital in Boston where Elliott P. Joslin had practiced.
Podiatry was part of the team back in the ‘30s. How many hospitals can say that? So they paid very good attention to protective footwear dressings in that. That’s why the TMA at the Deaconess Hospital in Boston was so successful when it wasn’t successful in other centers because they didn’t pay attention to the post operative care, the podiatric care or the footwear. So they were very good.
These are some of the images from that paper and exactly like we would see today, exactly like we would see today. [00:08:02] More often than not, we’re doing these hybrid TMAs because we have large plantar wounds that we have to close many times from ray amputations that become infected or with adjacent osteomyelitis. But this would be a classic demonstration, the classic shape of a TMA as we’ll see further here more of the same.
So this 215 patients, there’s still not a study with 215 TMA patients. This was retrospective, but still, that’s the largest study to date. And of course, what’s used as an alternative, the transtibial amputation in patients with infection, gangrene and tissue loss. But, of course, they stabilized first as you saw in some of those images to allow the infection to stabilize, remove the gangrene and then do a definitive, final closure.
The classic TMA operation which I do, I don’t like fish mouth TMAs. It goes against my grain, but it’s more or less a rounded incision in the forefoot, a rounded incision plantarly going as far towards the sulcus as possible and using that long plantar flap to come up, so your suture line is more dorsal, medial lateral dorsal, not on the end. I just do not like fish mouth type TMAs because this is the classic way and I was trained in the classic way.
Now, the results, they had an initial 72% success rate. Remember, most of their patients had gangrene or PAD. They used this in neuropathic patients for excision of infection and they also used it in non-neuropathic patients who had infections in the forefoot. But they had out of the 215 patients, 155 successes. Of course, they had some failures and reamputations and some of their patients weren’t healed and some went up to the transtibial operation. [00:10:02] But still, 72% success rate mirrors everything that we do today, but they were very, very good at making that preoperative assessment. Dr. Marino mentioned how your preoperative assessment and your incision planning is so critical to the success of these operations.
So on modern studies, healing rates were studied between 50% and 74%. Complications are high and you have to expect complications. Revisions and reoperations is common as was mentioned, up to 30% major amputation rate depending on the series, depending on the country where they come from. And the predictors for non-healing as reported were ESRD, peripheral arterial disease, A1Cs of over 10 and of course leukocytosis generally over 12.
Gibbons, I mentioned this paper before, 1979. It’s amazing how I go back to the future because this paper was done looking at amputations and I’ll be brief on this. They looked at their success rate for healing amputation. They tried to find a predictive factor that could let them determine will this patient heal or not. They didn’t have TcPO2s and perfusion pressures. They didn’t have angiograms back in ‘79, but modern day vascular surgery was at its infancy.
So they looked at ABIs and they looked at pulse volume recordings and they found that only 3% of patients where the moderate or strong forefoot PVR failed to heal. That was the only predictive factor. So they said if you had a forefoot PV or a pulse volume recording wave that was moderate or strong at that level, you could predict healing and this is a very good PVR waveform. Those waveforms are not Doppler waveforms. Those are PVR waveforms. And as you can see on this side, they tend to flatten out. [00:12:00] If you have the PVR that’s… I call it flat line PVR, you’re not going to be successful in that area unless you revascularize that. So that’s why I use PVR as one of my final arbiters for making that determination
Politte did a large study of 101 feet, 90 patients with a minimum of six-month follow up rate. They had a healed stump in 57% of their cases. Palpable pedal pulse predicted healing… what is that? I rarely get a palpable pedal pulse nowadays. It’s optimal if you can. And, of course, ESRD, renal failure dialysis predicted non-healing and they also said and noted that TMA is associated with high complication rates in the diabetic and the PAD population.
This is a large study by Peter Blume out of New Haven, retrospective 91 TMAs in 80 patients primarily diabetic, many of whom had ischemia. I’m sorry. You can’t really see. These are Group 1 that’s also initially healed. Group 2 is also initially did not heal. Sixty-two TMAs initially healed at three months, but 74% of those were revascularized. Twenty-nine TMAs remained unhealed for three months. And finally, after six months, 63% of the patients were healed and these statistics are repeated over and over again from one study to another. So non-healing TMA was related to, again, end stage renal disease as well leukocytosis over 12.
Okay. So we’re seeing the same theme over and over again and that’s the way to assess what are the important factors for you to look at. Look at their prior literature. This study of Younger which is a small study, but it was out of Vancouver and they looked at their failures versus their healed TMAs drawn from a total cohort of 68. [00:14:00] And they looked for what is a good predictor of risk factor that we can use to assess whether somebody is likely to have a successful transmetatarsal amputation or will fail. And what they found for predictors for failure in A1C of… their average A1C was 10.6 in those who failed versus 7.8 in those who healed. And those patients needing to debridement] after a TMA, meaning a dehiscence that needed to be revised also reflected a poor chance for healing.
Now, there was no any power. There was no multivariate comparisons in here, but still a small study that gives you further clinical information for being able to assess preoperatively what factors might be important in determining success of your operation.
And Dukowitz in 2009, I think this one is from Israel, again, a retrospective study over 10 years, 54% had no complications and 46% had complications. This you have to expect, higher complication rates in poorly controlled diabetes, i.e. high A1C levels. And there was no significance between complication rates and PVD, coronary artery disease, congestive heart failure or chronic kidney disease. So, again, we’re seeing the same thing as we saw in the Younger study, uncontrolled diabetes at the time and it’s done like A1Cs of 10, 12, 14, 17, 18, whatever we see does not predict success in this regard. Sometimes we’re just forced to do what we have to do with the patients that we have.
This was a systematic review and metaanalysis published in the Foot and Ankle Surgery journal, Foot and Ankle Surgery in 2016. Looking at a number of TMAs, 1,400 patients with TMAs were identified in the literature in this. [00:16:01] And they looked at random effects model.
By looking at that, they found reoperation rate, estimated at almost 25% reoperation rate, reamputation rate estimated at close to 30%, very valid. I think that comes along with clinical experience. And a major amputation rate at about 30%, which is what we’ve seen in other studies too. So by looking at a number of studies, you kind of get a feel for what can you expect by doing these operations. And what do you need to prepare yourself for before you’re definitely going to be having complications.
And what they suggested was that the TMA versus other minor amps should be conducted based on patient-specific factors. Patient-specific factors. Do they have renal failure? Are they uncontrolled diabetics? What is their vascular status? How much tissue loss is there? Because they couldn’t identify any common theme throughout all the literature. Even though I’ve discussed some similarities with you, if you look at multiple studies, they all have different risk factors even though one of them might have been reflective of success and one is not reflective of success in another. So it really comes down to your clinical assessment and experience, based on the literature, based on your knowledge of the patients and underlying complication factors.
So with all I’ve said, how do we perform the TMA? Well, as I said, I prefer the classic TMA with the long plantar flat. These images come out of a chapter by Lee Sanders, one of our former colleagues who published in Frank LoGerfo’s textbook on surgery and peripheral arterial disease. And Lee is pretty much talking about the standard way to perform it with a one a plantar flat and resecting the forefoot.
More common than this, I rarely do the classic TMA because we almost always have a soft tissue defect on the bottom of the foot. [00:18:07] Like in ulcers, smacked up in the middle or we’ve lost a lot of tissue on one side or another. So we’re usually having to cut out the infected ulcer, bring the flaps together and then bring them dorsally.
And in fact, I prefect these operations because the closure is much better in appearance after you’ve resected out that wedge. And sometimes I’ll resect out a wedge if I have too many overhanging edges of skin on that plantar flap or it just doesn’t appear right. I’ll resect a wedge out of the plantar aspect. So I call that a hybrid TMA.
I don’t know if this is going to play. There we go. I’m not going to spend a lot of time on this. But this is what I would call a hybrid TMA. And this is probably a few years old, whoever took it, I had a lot of coffee. But you could see this is more common than not. It’s rare that we do not have a plantar skin defect. So we’ll make our transverse incision on top, we go right to bone on the side. And I go… I split the metatarsal, the first metatarsal and the fifth metatarsal right in half. And those are my lines for the plantar flap.
Come across as distally as possible as you can see depending on tissue loss, gangrene and perfusion. And then we excise the plantar ulcer, we go around this so that that plantar ulcer or that necrotic tissue is going to leave with the forefoot.
Steve, am I going to be able to do anything with this and have control on this? Can we move forward a little bit? No, I don’t want to move forward on… I don’t want to move forward on that, but I would just want to know… can we move forward on the video? Can we do that at all? Or is that impossible? Can you just move forward on the bottom? Can we get the screen? [00:20:00] I wanted to get to the… I guess it’s not going to work. I guess not. Okay, we’ll leave it here.
Anyway, that was the… we don’t have the time to spend on looking at the entire video unfortunately. But I use this Gigli saw. When I’m in Italy, I have to say it correct, Gigli saw. And they get very impressed with I say Gigli. Because it’s quick, it’s easy and I prefer doing that than cutting each one individually with a saw. So you usually have to trim off the… if there’s any plantar edges on the metatarsals. And on the first and the fifth metatarsal, you want to bevel them plantarly and laterally immediately so that you don’t have any prominent edges.
If you have trouble with the plantar flap, not having enough tissues to close, which can happen, you just have to cut back a little bit further. But that’s where the amputation planning comes in the front. You want to plan it so that you can affect a primary closure, unless you’re doing an open TMA. And sometimes you have to do an open TMA for drainage. The important thing about that is try not to do a guillotine TMA if you can avoid it.
The first time I did that I regretted it because I had no plantar flap. So there was nothing to close and you have to use tissue substitutes in that. So if you have good plantar skin, but necrotic toes and necrosis on the top, do your TMA, but plan out your plantar TMA. So you’re always planning stage B or operation B while you’re doing A and you’re always planning for stage 3 while you’re doing 1 and 2. So you need to think about what you’re doing in the future because most of these people are going to have repeat operations.
Okay. So we’ve done this study. It’s a prospective study, 106 patients, only one female, and this is going back as far as we can go, 2003, when I started here. [00:22:02] Average age is 64 years. The mean follow up is six years. Primarily diabetic patients with a mean ABI of 0.87, this would be after revascularization as well, with a median of 0.84. We had about 22% of our patients had died in a median of 8.5 years after the TMA. 66% of our patients primarily healed. That fits right in line with most of the other studies that I’ve said. The average time to heal is a long time because of dehiscences, about five months.
We had a 62% complication rate. This goes in line with every other study that we related to you already. And those complications are usually dehiscence, infection, some delayed healing, some necrosis, and 28% of our patients required a more proximal amputation like Chopart or Syme or a BKA, depending on the individual circumstances.
These are the results for dichotomous testing, all were non-significant PAD versus no PAD, A1c high or low, we didn’t see anything exactly there that could predict success. We looked at white blood count 12 and below and we saw similar rates of healing and complication rates and even smoking, there was not any significant difference. Maybe our population is very homogenous in that regard, so we weren’t able to find distinguishing characteristics between them.
But we did find some significant associations that would either predict healing or failure. One was MRSA from tissue cultures. And this is a predictor for healing. So if you have an odds ratio that’s less than 1, that means it’s protective against healing. So a 60% increased chance of failure with MRSA. And this was a surprise to us, but we’ve seen that in other studies as well. [00:24:01]
A predictor of proximal amputation, white blood count. Whereas the people who had proximal amputation had a white count of 13 versus 10 in the patients who were successful. This is consistent with other literature as well. And so it was a 13% or 14% increase for every point increase in white blood count. As you can see, that was significant.
And then we did an interaction time with those with peripheral arterial disease and MRSA. Remember, just peripheral arterial disease was not significant because so many people had PAD. But if you had PAD and MRSA, a sixfold increased risk for more proximal amputation. So this is kind of insightful to us, but our patients are very homogenous in this large population. We didn’t see all the same risk factors at all the other studies had shown.
So in summary of our study, PAD, A1c, leukocytosis, kidney disease and smokers all have longer healing times. Yes, they did have longer healing times, but it was not significantly different from those without those risk factors.
And while PAD ended with longer healing times, there was no association with healing failure, complications or proximal amputation. But MRSA conferred nearly a 60% increased risk for not healing the TMA. White blood count confers a 14% increased risk for proximal amputation for each 1,000 points elevation. That’s the odds ratio, 1.03. And the interaction of PAD and MRSA confers a sixfold risk for proximal amputation. So PAD with MRSA is bad. High white count, bad. So you have to make sure that those patients are well controlled.
So our population was predominantly older and diabetic with a number of comorbidities as you can see. [00:26:03] Although 66% of the patients healed, post-operative complications were common. And nearly 30% required more proximal amputation. Again, you can expect that this is going to be the case because we’ve seen in multiple studies as I’ve already mentioned. MRSA was the only individual risk factor identified associated with failure. And again, I’ve already mentioned the fact that PAD with MRSA is not good.
So we tend with the thorough study that I’ve already mentioned. That it’s all based on individual risk factor. No one factor or combination of factors will predict success in all cases or failure in all cases. you have to base your approach to treatment based on patient-specific factors like tissue loss, extensive infection. And remember that reliable predictors of success are often elusive. So you really have to develop good clinical acumen, good clinical judgment, put your imaging studies together with your perfusion studies, with level of infection and make your choice. But you always want to operate in a clean environment when you can with careful forethought.
So in summary, TMA are effective limb salvage procedures, but complications are common, as I said, and very close follow up is required. Appropriate evaluation of vascular status and infection are key elements in operative planning and level selection. Careful control of glycemia in diabetic patients is required. Even though the results are inconsistent, you want to keep your patients in good control. The better control they are, the more likely you’ll have success.
And remember, I think I’ve said this several times. Therapeutic footwear, education and constant surveillance will reduce your recurrences. They’re critical to success. [00:28:00] Remember the Deaconess experience was different than experience in most other parts of the country and the world with a TMA. Why? Because they had a podiatry team. They had a multidisciplinary team back in the 1930s and the ‘40s. So they were very good at managing these patients after the operation once they healed.
And, of course, they did this with the team approach as we’ve said throughout this meeting. Much better outcomes with team approach, work with your vascular surgeons, work with your ID specialist, work with your hospitalist internist, orthopedist as necessary.
Thank you very much.
END OF CLIP