Information for Medical Professionals
We’re going to talk about the Plon-Arnold modified Wilson osteotomy, which is a minimally invasive procedure for bunions. It is a V-shaped osteotomy. Here is your V and the apex points proximally so this is the apex and here is the V. It is in the transverse plane and the head of the first metatarsal is then displaced laterally to reduce the intermetatarsal angle. Here is what it looks like from the dorsal lateral point of view. Here is the apex and here is the dorsal osteotomy and the plantar osteotomy. Its indications are for a mild to moderate hallux abducto valgus deformity. The first metatarsal phalangeal joint should be flexible or you won’t get a good result and mild to moderately increased metatarsus primus varus angle. If you use it for a severe bunion you won’t get as good a result and if it is track bound you will not get as good a result.
The procedure was originally described by an orthopedic surgeon named Wilson in England in 1963. It was basically an oblique osteotomy from distal medial to proximal lateral. It was suggested by Dr. Weil of Chicago to doctors Kessler, Plon and Arnold in the 70s, that it might make an interesting minimally invasive procedure. Plon and Arnold modified the procedure from an oblique osteotomy to a V-shaped osteotomy to give it a bit more stability. They made a fail-safe hole at the neck of the metatarsal to start the osteotomy. It is designed to be performed under local anesthesia in the office. You can do it with a ankle block or with local infiltration and a modified Mayo block.
These are the keys, the most important part is the instrumentation. This is a short Shannon burr. You can combine the procedure with an Aiken osteotomy so you use the short Shannon for the Aiken. This is a medium Shannon burr or Shannon 44 with which you make the osteotomy of the neck of the first metatarsal and this is a 3 millimeter wedge burr which can be used to remodel the hyperostosis, the dorsal medial eminence. This is a Locke elevator which I use to free up the capsule from the head of the first metatarsal. You can also smooth the bump with a short cottle nasal rasp. This is a very interesting piece of equipment. It is called an eye magnet. This is not a procedure for beginners and it should be performed with fluoroscopy. This is mine from 1986, my handheld fluoroscope which, thank goodness still works. The equipment for performing the osteotomy should be a high torque low speed machine.
I like to draw landmarks before I start. This is the plantar medial cortex, this is the dorsal medial cortex, this is the lateral cortex, this is the Extensor Hallucis Longus tendon and here is your osteotomy, the V pointing proximally. This is the dorsal part of the osteotomy and this is your first metatarsal phalangeal joint. I start by making an incision with a number 15 blade halfway between the dorsal medial and the plantar medial cortices. This is for the fail-safe or pilot hole. Then I begin making the pilot hole with a Shannon 44 burr from medial to lateral, halfway between the dorsal and plantar cortices and this shows it on the saw bones. I am trying to make it at a 90-degree angle to the long axis of the second metatarsal because that is the long axis of the foot for all intents and purposes. You can change the osteotomy angle from proximal medial to distal lateral to reduce shortening but you’ll find that it is more difficult to displace the metatarsal head laterally if you do that. Here we are starting. We have done the fail-safe hole from medial to lateral from the medial cortex through the lateral cortex with one burr and then switch burrs. Here is the burr, here is what it looks like. It is basically parallel to the supporting surface of the ground. You can plantarflex it slightly if you want to. Here I have made a second incision a little dorsal to the first incision for the purpose of remodeling the bump. I used to make it dorsally. Now our Spanish colleagues have taught us that you are less likely to cause any damage if you do it plantarly.
So now I make the second incision plantarly. It is easier to remodel the first metatarsal head through a second incision than through the original incision and here you can see the two incisions. Really, you don’t have to make it much wider than the width of a number 15 blade. You can make it wider if you need to.
Here I am putting in the Locke elevator and pushing it through under the capsule to free up the medial eminence and this is a Shannon 44. I am beginning to reduce the bump and the medial eminence with a Shannon 44 and then I continue using a three-millimeter wedge burr because it is easier to remove bone. I remove part of the bump before I perform the osteotomy and then after I’ve completed the osteotomy I’ll remove whatever is left. The reason I do that is because you do not need to remove the whole bump. Once you displaced the head laterally you will find that a lot of the eminence does not need to be removed and I will show that in a few minutes.
And here we are starting the osteotomy. We are pivoting from the original osteotomy site and we are going in a dorsal distal direction cutting the dorsal half of the lateral cortex and then we continue the osteotomy across the dorsal cortex from lateral to medial. Again we are pivoting through that osteotomy site through the original fail-safe hole and then we finished the dorsal cut in the dorsal medial portion of the cortex so we have now completed half of the osteotomy.
So then we go back with another burr, a third burr, into the original fail-safe hole or pilot hole and we are going to cut the plantar surface and you can see these are the sesamoids and so we start cutting again. We are pivoting from the original osteotomy site, we are cutting the inferior lateral cortex and then cutting from lateral to medial, cutting through the plantar cortex and then finally through the medial inferior cortex so that to complete the osteotomy and there’s the completed osteotomy. The only thing I do slightly differently is the inferior cut. I try to angulate it slightly distally just short of the sesamoids because by making it a little bit more distal angle it locks it in better and contributes to more stability. Then you displace the capital fragment laterally and before you might have removed this entire bump but then you would have a big shelf, proximal shelf so you remove a little bit of it push it over and then you can remodel whatever is left once you’ve displaced it. You can fixate it or you can do it non fixated. If you are not fixating it then you would jam the capital fragment on to the proximal part of the osteotomy and when you remove this there can be a proximal ledge. If you can palpate it you should try to remove it because the patient may feel it in their shoes, and you can do that with a short Shannon. The procedure, by the way, can be combined with an Aiken osteotomy, a lateral release and/or an Extensor Hallucis Longus lengthening and here I am remodeling the bump after I performed the osteotomy.
You can use K-wire fixation. There are many surgeons that do not use K-wires. I do because I get a more predictable result. So I used two K-wires and here is the first K-wire, and here is the second K-wire. As long as you put it in at an oblique angle, it will hold in most cases. If you do not use, that is okay.
We tape the foot for six weeks, I have the patient back four or five days later for a check-up and then once a week for five weeks and on the sixth week they take it off at home. You wrap with gauze. This is called Durapore tape, a hypoallergenic tape, and you can keep the great toe hyper adducted and it will help to hold the metatarsal in position. If you are using K-wires then you want to put gauze padding distal and proximal to the K-wires to relieve pressure against the wires because it will irritate the patient, so then you have a bulkier dressing. And if you’re concerned about cracking the shelf you can use a dancers pad to relieve or reduce pressure from the ground reactive forces so you are less likely to crack the dorsal cortex especially with an older person. The wires come out in three weeks and at the three week point I begin range of motion exercises. The patient uses their contra lateral hand to do exercises for six minutes, twice a day. A minute down and a minute up alternating for six minutes twice a day till I tell them to stop.
Advantages of minimally invasive surgery bunions; with smaller incisions, you have smaller scars. Think like a patient. The doctors say the scar heals from side to side not end to end but the patients like a nicer looking foot. With the smaller incisions you have less soft tissue trauma. In most cases less soft tissue trauma results in less post-operative pain. Most patients will not require narcotics, casts are not necessary. It can be performed under local anesthetic in an outpatient setting.
And I have got some before and after. This is pre-op and post-op and the key is to have nail polish on all your post-op patients because it looks better in your post-op. And here is the pre-op x-ray and Wilson osteotomy K-wire fixation Aiken osteotomy. Maybe I did an adductor, I do not remember. Its important to look at the lateral to make sure the head is in the right position, this is one-year post-op, you can see the head is not elevated and it looks pretty good and this is the same patient. Here is a second patient before and here is the osteotomy. You can see the V right here with K-wire fixation, and Aiken osteotomy. I try to leave the Aiken intact, the lateral cortex intact. This is one-year post-op, comparison. This lady had really a more severe bunion deformity with an overriding toe. I did her other foot years ago. It didn’t look beautiful but she said I want you to do it so I did it again, I mean I did the other foot and it came out pretty well. This is before and this is three months post-op and seven months post-op. It was just done in 2012. I will have her back for another x-ray one of these days and so it looks pretty good. What I did was a Wilson and a Aiken and an adductor release and osteotomies two and three and for the toes I did an osteotomy at the base of the proximal phalanx and at the neck of the proximal phalanx and I think I did the base of the proximal phalanx on the third toe. And this lady, the exciting part of this is not that she had a bunion but she came in to see me in 1988 and had her first bunion done and she came back within the last year twenty-four years later to have the second bunion done. So this is the pre-op of the left foot and the Wilson with the K-wire fixation and Aiken. But the interesting thing is I did her right foot in 1988. Here is pre-op and also I can’t tell if I did a fifth met here or not but I didn’t use K-wires back in 1988. But here is the procedure and it did heal one year later; and you can see the head has healed in a very nice position and this is what it looked like twenty-four years later. So here it is this is the pre-op in 1988, this is post-op in 2012. So the procedures do have longevity if you use the right procedure with the right foot.
If your interested in learning more about this type of surgery, I recommend this book: “Minimally Invasive Surgery of the foot and ankle, and Dr. Dominico is familiar with it, edited by Maffulli and Easley and a second version came out with just the forefoot, The Academy of Ambulatory foot and ankle surgery is the Academy that disseminates this information. If you are interested here is the website. Our next seminars in New Orleans in January 2014, if anybody has any questions please feel free to e-mail me, this is my website and my YouTube channel. Thank you very much.