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Emerging Innovations With The Lapidus Bunionectomy

With an improved understanding of hallux valgus pathoanatomy, new fixation options and emerging technique modifications, the Lapidus bunionectomy has become increasingly popular. Accordingly, this author examines the latest advances with the procedure and emphasizes key principles as well. 

If you have been practicing podiatric medicine and surgery for some time, you know procedures and treatments will be in vogue for a while, and then may fall out of favor. For example, 20 to 25 years ago, external fixation was the thing to do. Now, it seems surgeons only utilize ex fix for select trauma and possibly for some Charcot reconstructions.

With respect to bunion surgery, there seems to be three main surgery techniques that podiatric surgeons utilize most often. Distal metatarsal osteotomies (i.e. chevron/Austin) are the most common and there are surgeons who primarily perform the scarf bunionectomy. Lastly, while the Lapidus buionectomy is not a new technique, its use by podiatric surgeons has ebbed and flowed over the years. Now the Lapidus procedure is seeing a resurgence of popularity in our profession.

Those who utilize the scarf procedure are less likely to ever perform a Lapidus bunionectomy as these surgeons feel they can correct all deformities with a scarf bunionectomy. For those who primarily perform the Austin type bunionectomy, they will typically perform a Lapidus procedure when the intermetatarsal angle is very large or if there is significant first ray mobility.

A Closer Look At The Advantages And Drawbacks Of The Lapidus Procedure

For the true hardcore Lapidus believers (whom I call “Lapidonians”), they will fix most bunions if not all with the Lapidus bunionectomy. Their argument against choosing any type of metatarsal osteotomy to fix a bunion is: “Why make a straight bone crooked?” Lapidonians also opine that the surgery corrects the deformity where it originates, addresses more than one plane of deformity, is much more powerful in its correction due to the proximal location and, now with newer fixation methods, weightbearing can begin immediately. With early weightbearing, there may be less resistance to perform the surgery by members of our profession and that may be a factor in the increasing popularity of the Lapidus.  

Surgeons have traditionally recommended the Lapidus bunionectomy as the treatment of choice for patients with hypermobility of the first ray. In recent times, it has been difficult to determine the exact nature of first ray hypermobility. To that end, rather than use the terminology “hypermobility,” it may be more appropriate to use “instability of the medial column” instead. The determination of medial column instability may include a physical examination to determine excessive sagittal and transverse plane mobility as well as lateral radiograph findings of elevation of the first metatarsal base at the cuneiform, cortical hypertrophy of the second metatarsal shaft and cuneiform split.

When we discuss improvements upon established surgical techniques, we typically see improved methods for fixation, joint preparation and reduction of complications.

The Lapidus bunionectomy has its inherent problems. There is a longer learning curve than with distal metatarsal osteotomies. Advances in technology and modifications of the technique are specifically designed to reduce complications of nonunion, malunion and recurrence of deformity. When we discuss nonunion—and this applies to any fusion surgery—adequate joint preparation and stable fixation are paramount. Certainly, the patient’s metabolic state and extrinsic factors such as nutrition, smoking and lack of adherence play key roles. It is my opinion, however, that nonunions are more due to surgeon error rather than the patient’s fault. Certainly, there are exceptions.

How Lapidus Fixation Is Evolving

Let’s talk about the fixation of a Lapidus bunionectomy. You know that with adequate joint preparation and stability of fixation, you will get a union. I have personally used just about everything available as far as fixation devices go. I will tell you they all work and they all don’t work. What I mean is I have had and seen failures of union with K-wire fixation, crossing screw fixation, staple fixation, locking plates with and without lag screws, and external fixators. The moral of the story is that we should be relying more on preparation than hardware.

Unfortunately or fortunately, depending how you look at it, we as a group of surgeons are always looking for better fixation. We want beefy, strong implants with mega amounts of compression. We want early or immediate weightbearing. The truth of the matter is that we don’t know how much compression is necessary and if too much compression can impede healing. Regardless, we still want as much compression as humanly possible.

Over the past few years, we have seen the emergence of a plethora of anatomic Lapidus plates that incorporate a lag screw. One of the newest internal fixation devices that I have seen and used is the Phantom Lapidus Intramedullary Nail System (Paragon 28) (see radiograph at left). The manufacturer claims this type of device can generate a higher compressive force across the fusion site in comparison to traditional plates and screws.1 Another new method for fixation of a Lapidus bunionectomy is orthogonal plating, which employs two plates: one dorsal and one plantar medial. Authors have described this fixation as improving stability and negating the need for a compression screw.2 This will give more bone-to-bone contact for fusion. This type of fixation is amenable to immediate weightbearing, which is encouraged.2

Key Principles In Joint Preparation

One can prepare the joint for fusion with hand instrumentation with an osteotome and/or curette. This is a good choice when there is concern about over-shortening the metatarsal with a patient who already has a short first ray. Moreover, if the patient has concomitant second metatarsophalangeal joint (MPJ) pathology from lesser metatarsal overload, our main goal is to have a functional and weightbearing first metatarsal. Certainly, maintaining length is beneficial for that. In addition, if you believe thermal necrosis of bone is a potential issue, then joint preparation with hand instrumentation avoids that problem.  

The surgeon can also resect the joint with a saw. The benefit is that you will easily get beyond the subchondral bone and have raw cancellous bone-to-bone contact, which will give you the best chances of a rapid fusion. Some concerns about this technique include over-shortening of bone, angular cuts may be off and more planing and loss of bone may occur. When doing planar joint resections, you are married to one position and if you don’t like it, then there is more fiddling to do. Improper joint preparation also leads to malunion with the elevated first ray as the most common condition (see right photo). We have all had this problem even when we thought everything looked perfect intraoperatively and with intraoperative fluoroscopic imaging.

One of the newer methods available for joint preparation is using a jig/osteotomy guide system (see left photo). When a patient is having orthopedic surgery outside of the lower extremity, jigs are commonplace. For example, surgeons have used jigs for years to allow for precise planning and execution of osteotomies for knee replacements. In the future, computer-assisted devices may be the norm.

Jigs and osteotomy guides in foot surgery are not new concepts. How many of you have used or still use a Reese osteotomy guide for a chevron osteotomy? How many use a K-wire for an axis guide when doing a chevron osteotomy or a base wedge osteotomy? I still do that even though I have been cutting chevron osteotomies for more than 20 years. I personally think doing whatever we can do as surgeons to help us achieve reproducible results and good outcomes every time we do surgery is a good goal to have. If using an osteotomy guide helps, then I am all for it.

Pertinent Considerations For Lapidus Modifications

One of the more frustrating problems that we encounter after performing a Lapidus bunionectomy is recurrence of the deformity. The dogma is that the instability of the first ray comes from the first tarsometatarsal joint. So if we fuse the joint, how can we get recurrence of deformity? Well, the answer is that instability also involves the more proximal joints (naviculocuneiform and intercuneiform joints).

Attempts to modify the traditional Lapidus procedure have included placing a screw from the medial cuneiform to the intermediate cuneiform, Endobutton (Smith and Nephew) fixation between the metatarsals, screw fixation between the first metatarsal and middle cuneiform, and a screw fixating the first and second metatarsals. We can consider all of these techniques as a modified Lapidus bunionectomy. Complications have occurred with many of these types of added fixation maneuvers. The Endobutton fixation technique can lead to a stress fracture. The fixation between the cuneiforms does not hold well due to the soft nature of cancellous bone. What seems to be the best technique is a screw from the medial first metatarsal into the base of the second metatarsal. Surgeons typically use a fully threaded screw without lagging.

So how do you know when you should add a screw between the metatarsals? Fleming and colleagues described and studied the intercuneiform hook test.3 The goal of their research was to determine the frequency of intercuneiform instability in patients receiving a Lapidus bunionectomy for having clinically noted hypermobility and large intermetatarsal angles. After correction and fixation of the first tarsometatarsal joint, under fluoroscopy, surgeons used a hook to see if they could cause separation between the cuneiforms and ultimately see an increase in the intermetatarsal angle. If the authors had a positive hook test, then they would consider adding fixation between the first and second metatarsals. In their study of 38 Lapidus procedures, Fleming and coworkers noted the incidence of proximal instability (positive hook test) was 73.68 percent. That is a surprisingly large percentage of proximal instability. This finding suggests to me that we all may be under-fixating our Lapidus bunionectomies.  

If you don’t have any fancy instruments to test for proximal instability, I will give you a tip for a simple maneuver. Under fluoroscopy, if you pinch into the first intermetatarsal space between your thumb and index finger, you are stressing your completed fusion with hardware in place, and can determine if there is splaying of the metatarsals/splitting of the cuneiforms. That would be the “poor man’s” hook test.

Taking it one step further, spot welding the base of the first and second metatarsals has been popular in the past few years. The technique would include roughing up the medial border of the second metatarsal base and lateral aspect of the first metatarsal base. If there is not intimate bone-to-bone contact between the two bones, then use bone grafting. I would avoid using the resected “bunion” bone as this is not good bone. I would use the allogeneic bone of your choice stocked in your facility. You would pack the bone in the crevice between the metatarsals so consider using putty or something more malleable that can seep deep down between the bones.

Are Bunions Triplane Deformities?

The final and probably the most important advancement that I would like to talk about in the Lapidus bunionectomy is the theory that bunions are triplane deformities and not just a medial drift of the first metatarsal (transverse plane) and sagittal plane deformities. Unless you have been hiding under a rock, you have been exposed to the idea of frontal plane deformity in hallux valgus. You cannot go to a foot surgery seminar without a discussion of this concept. Dayton and coworkers popularized this theory in their series of papers beginning in 2013.4 If you have not read Dayton’s work, then you should put that on your “to do” list.

As with all things that we do, I do not believe in absolutes and even though I am a believer in frontal plane deformity in hallux valgus, not all bunions have triplane deformity or need to be addressed. This is where proper preoperative assessment of bunions with more emphasis on sesamoid position is necessary. You may consider getting sesamoid axial views that can help determine how much, if any, frontal plane deformity is present.  

Intraoperative decision making will be crucial when doing a Lapidus procedure. After the joint is mobile and free of ligamentous constraints, you can rotate the metatarsal under fluoroscopy and determine whether frontal plane deformity is a factor. If you use a joint distractor to prepare your joint, insert two K-wires, one in the cuneiform and one in the metatarsal. You can rotate the K-wire in the first metatarsal in the frontal plane. Rotate the metatarsal K-wire laterally (toward the fifth toe) to reduce the varus deformity (see above right photo). If you feel frontal plane deformity is playing a role, then you can prepare your joint and rotate the metatarsal prior to fixation. However, do so with caution as overcorrection of the frontal plane deformity can lead to a stiff joint (see left photo).

In Summary

The improvements over the past few years for the Lapidus bunionectomy have included advances in understanding pathoanatomy of hallux valgus in that there can be a third plane of deformity in the frontal plane. This has led to innovations with osteotomy guides and fixation techniques. Remember, there are no absolutes in surgery. I personally don’t think every bunion deformity needs frontal plane correction nor do I believe every bunionectomy needs to be a Lapidus bunionectomy. If you know what you are looking for, you can make appropriate decisions as far as what to correct and how to correct it.

Finally, understanding and addressing proximal instability and utilizing adjunctive fixation techniques with spot welding between the metatarsals has improved outcomes in my experience, and reduces the chance of recurrence. Remember, we are not robots or technicians. We make intraoperative observations and address them accordingly. Accordingly, after you fixate a Lapidus bunionectomy and have the correction you like, take a few seconds to do a hook test for evaluation of proximal instability. If indicated, it only adds a few minutes to add one more screw.

Dr. Fishco is board-certified in foot surgery and reconstructive rearfoot and ankle surgery by the American Board of Podiatric Surgery. He is a Fellow of the American College of Foot and Ankle Surgeons, and a faculty member of the Podiatry Institute. Dr. Fishco is in private practice in Phoenix.

References

1.     Phantom Intramedullary Nail. Test report (TR-17060501) on file at Paragon 28.
2.     Perren SM. Evolution of the internal fixation of long bone fractures. The scientific basis of biological internal fixation: choosing a new balance between stability and biology. Bone Joint Surg (Br). 2002; 84(8):1093-1110.
3.     Fleming JJ, Kwaadu KY, Brinkley JC, Ozuzu Y. Intraoperative evaluation of medial intercuneiform instability after Lapidus arthrodesis: intercuneiform hook test. J Foot Ankle Surg. 2015; 54(3):464-472.
4.     Dayton P, Feilmeier M, Kauwe M, Hirschi J. Relationship of frontal plane rotation of first metatarsal to proximal articular set angle and hallux alignment in patients undergoing tarsometatarsal arthrodesis for hallux abducto valgus: a case series and critical review of the literature. J Foot Ankle Surg. 2013; 52(3):348-354.

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William Fishco, DPM, FACFAS
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