Hallux Valgus And Frontal Plane Deformity: Why I Still Don’t Get It

I just read the DPM Blog written by Patrick DeHeer, DPM, last week on hallux valgus and frontal plane deformity. However, after reading the blog, I still have to admit I do not get it.¹

In his blog, Dr. DeHeer is asking why any surgeon would still not accept the notion that the first metatarsal is “pronated” in hallux abducto valgus (HAV) deformity.¹ Dr. DeHeer touts a recent published study from Campbell and colleagues and proclaims: “The arguments against HAV as a three-dimensional deformity with a frontal plane component are hyperbole at this point.” ²

Hyperbole? Consider the proclamation made by Dr. DeHeer in reference to the Campbell study: “The parameters of this study adequately mitigate the doubters’ criticisms of previous studies. Once and for all, we can put this issue to bed.”

Intrigued about this allegedly groundbreaking piece of research from Campbell and colleagues, I read the paper and quickly discovered it was a pilot study.² Furthermore, I realized Dr. DeHeer did not discuss or report a number of significant findings from this study, findings that have important implications for those who are interested in this subject of frontal plane correction of HAV deformity.

Before I proceed, it is important to point out the commercial influences on this debate. Dr. DeHeer appropriately discloses his relationship with Paragon 28, which is marketing a new technology to correct alleged frontal plane pronation of the first metatarsal in HAV deformity. Another company, Treace Medical, has patented the technique for frontal plane pronation correction of HAV as well as the technology for a Lapidus procedure to correct this deformity. Paul Dayton, DPM, and other authors of papers on this subject are owners of this Treace Medical patent.^3,4 I own a company that markets ankle-foot orthoses. My interest in this subject is the co-authorship of a paper documenting the direction and range of motion of the first ray, a study that has been challenged by Dr. Dayton and Dr. DeHeer.⁵ That is why I have written often on this subject and continue to do so.^6-8

The study published by Campbell and coworkers clarifies in the title that this is a pilot study.² It is not even close to being a groundbreaking, irrefutable body of research as suggested by Dr. DeHeer. As Campbell and coworkers state in their conclusion: “Last, this work must be considered a methodological study because many more participants should be examined before any normative values are established.”

Although Dr. DeHeer states that the Campbell study utilizes “weightbearing computed tomography (CT) scans and 3D computer-aided design (3DCAD) imaging,” we should note that the authors clearly clarify that their methodology utilized “simulated weight bearing,” which employed a pedal device which pushed against the patient’s foot, which was oriented horizontal to the ground.² The position of the foot to the leg and the position of the foot to the pedal device was not controlled, and the study did not describe it.

Campbell and colleagues recognize the importance of evaluating position of the first metatarsal relative to the second metatarsal and the rest of the foot, not relative to the ground in patients with HAV deformity.² I have argued this point several times in the past as previous studies ignored this critical factor.^6-8 Indeed, the Campbell study showed that in patients with HAV deformity, the first metatarsal was “pronated” (actually everted) relative to the second metatarsal 8.2 degrees more than the control group. Eight degrees of frontal plane rotation would be the equivalent of moving the arm of a clock 1.2 minutes. The naked eye would probably not be able to discern such a minor rotation of the first metatarsal.

The only explanation for the first metatarsal being pronated or everted relative to the second metatarsal in a static position of the foot would be if the first ray was plantarflexed from its neutral position. This is based upon the well accepted notion that the first ray rotates upon an axis, which allows dorsiflexion with inversion and plantarflexion with eversion.^5,9 In HAV deformity, it is well accepted that the first ray is dorsiflexed, not plantarflexed in static stance.^5-7

Conversely, the first ray could be rotating about an entirely new axis, never verified in any sound kinematic study, which would allow dorsiflexion/eversion or plantarflexion with inversion of the first ray. Dayton and colleagues have actually posed this radical challenge to the axis of the first ray although the authors had no kinematic data to support such an unfounded conclusion.¹⁰ The fact is that the axis, direction and range of motion of the first ray is probably the most well accepted and thoroughly verified principle in lower extremity biomechanics. Currently, there have been no less than nine valid studies of first ray range of motion and kinematics, and all have verified the axis originally described by Hicks and coworkers, which dictates that the first ray moves in a direction of dorsiflexion/inversion and plantarflexion/eversion.^5,11-19

It is possible that the people in the Campbell study could have inverted their hindfoot as they pushed down on the positioning device.² This would have plantarflexed and everted or “pronated” the first ray. This entire question could have been answered if Campbell and colleagues had published data measuring the sagittal plane position of the first metatarsal relative to the second metatarsal. Inexplicably, they failed to do so.   

We know healthy people demonstrate dorsiflexion/inversion of the first ray during walking.^14,15 Perhaps patients with HAV deformity have a different axis of rotation of the first ray? Newer studies with three-dimensional CT imaging have verified that patients with HAV deformity will demonstrate dorsiflexion with inversion of the first ray when standing.^16,17 The only true weightbearing CT study of HAV patients failed to show any significant “pronation” of the first metatarsal.¹⁸ Two high quality kinematic studies of HAV patients walking demonstrate that these patients have greater dorsiflexion and inversion (opposite of “pronation”) of the first metatarsal in comparison to healthy people.^19-20 All of these studies have occurred in state of the art biomechanics labs and been published in prestigious peer-reviewed journals.^14-20 This is hardly a collection of “biomechanical hypotheses” as Dr. DeHeer alleged in his DPM Blog.

Dr. DeHeer did not discuss a critical finding from the Campbell study.² This study found no correlation between the amount of pronation of the first metatarsal and the amount of intermetatarsal angle deformity measured from plain radiographs of the patients. Therefore, there does not appear to a mechanism causing “pronation” of the first metatarsal, which is linked to medial deviation of the first metatarsal. In other words, the two motions do not appear to be coupled. Thus, there could not be a new axis of rotation of the first ray to explain the pronation motion/position of the first metatarsal in HAV deformity measured in this study. In other words, pronation of the first metatarsal appears to occur from a mechanism different and separate from the mechanism that causes medial subluxation of the first metatarsal in HAV deformity. It is very possible that this other mechanism is position or alignment of the foot itself. 

Clearly, the Campbell study shows the magnitude of frontal plane pronation of the first metatarsal in HAV deformity is not predictable based upon other plain radiographic criteria.² The authors state:

“To our knowledge, there is currently no reliable and reproducible method of assessing pronation from plain radiographs. Erosion of the inferior metatarsal head crista from sesamoid subluxation and measurements taken relative to the floor that do not account for whole foot pronation make measurements done in this fashion suspect.”

When it comes to making surgical decisions in regard to correcting first metatarsal pronation, Campbell and coworkers also caution surgeons about basing this solely on plain radiographs, which only measure the alignment of the first metatarsal to the floor:²

“If first ray pronation is measured relative to the floor, the resulting measurement is the sum of the true pronation of the first metatarsal and pronation of the whole foot. As we learn to better surgically treat bunions and how the first metatarsal deformity affects the whole foot structure, correcting first metatarsal pronation relative to the floor may result in excessive supination of the metatarsal.”

Thus, plain radiographs, especially axial sesamoid views, which dorsiflex the hallux and plantarflex the first ray, will overestimate the amount of “pronation” of the first metatarsal that occurs in HAV deformity. The recent paper from Hatch and coworkers (owners of the frontal plane Lapidus patent) classify triplane HAV deformity based almost entirely upon the plantar axial sesamoid image of the foot.^3-4

Indeed, using first metatarsal alignment to the floor measures, Dayton and colleagues found they needed to rotate the first metatarsal 22 degrees into inversion to correct frontal plane pronation deformity of the first metatarsal.¹⁹ This excessive supination correction would overcorrect the everted position of the first metatarsal by almost threefold, according to the Campbell study.²

In his article, Dr. DeHeer makes sweeping condemnation of the efficacy of traditional bunionectomy procedures practiced by the majority of podiatric surgeons around the country.¹ He cites a 73 percent recurrence rate for the Austin bunionectomy, based upon a very strict hallux valgus angle threshold in one single study.²² Dr. DeHeer cites another systematic review of 229 studies of outcome of HAV surgery recently published in the Journal of Bone and Joint Surgery (JBJS).²³ However, he fails to mention that the overall rate of recurrent deformity for distal first metatarsal osteotomies was 4.1 percent and shaft osteotomies was 5.6 percent. Notwithstanding, ignoring this high-quality study in JBJS, Dr. DeHeer is recommending abandonment of the two most popular bunionectomy procedures in the country, ostensibly in favor of the aforementioned frontal plane pronation correction procedures. He states:

“Why do those adamant about continuing to employ the Austin or scarf bunionectomy procedures ignore the data? Why do they try to spin outdated literature to support antiquated notions? It beats me.”

Despite the fact that the new frontal plane correction surgical procedures for HAV are untested and unproven, Dr. DeHeer writes in his blog:

“Regardless of the root cause to those still digging in their heels, either we practice evidence-based medicine, or we practice biomechanical hypotheses. I will choose evidence-based surgical research every day and twice on Sunday.” 

Since there is no evidence-based surgical research validating positive outcomes from frontal plane inversion of the first metatarsal in HAV surgery, podiatric surgeons should continue to trust procedures that have been subjected to such scrutiny. For example, Klemola and colleagues published a head-to-head comparison of a distal chevron osteotomy to arthrodesis of the first metatarsocuneiform joint in patients with HAV.²⁴ Subsequently, they published a five-year follow-up on these surgical patients.²⁵ Remarkably, this Lapidus-type surgical procedure rotated the first metatarsal into eversion, not inversion as advocated by commercial interests here in the United States. 

Indeed, Campbell and coworkers raise caution to the readers of their article:²

“The pronation resulting from the rotation sequence required the selection of points to determine the bodies’ orientations. Future work may address measures of pronation using software that relies only on the bone geometry.”

They point out that the technology used for this study is not available to the average surgeon and that standard of care does not require it. According to Campbell and coworkers, “The pronation obtained from the creation of the solid model from the CT scan requires the application of specialized technology and the investment of processing time; we are not advocating the need for this as a current standard of care.”

Finally, the most important conclusion made from Campbell and colleagues poses a caution regarding the detection of first metatarsal pronation in HAV deformity regarding based upon plain radiographs or clinical assessment.

“Until such time as widespread clinically useful first ray angular measurements can be made available to surgeons, caution is advised in the use of any measures based on clinical assessment or plain radiographic evaluation.”

Final Notes

In summary, a new paper published by Campbell and coworkers evaluated the frontal plane alignment of the first metatarsal relative to the second metatarsal in 10 patients with HAV deformity in comparison to 10 healthy controls.² In this study, using simulated weightbearing and 3D imaging, the first metatarsal appeared “pronated” (everted) by 8.2 degrees relative to the second metatarsal. This is equivalent to looking at the head of the first metatarsal and rotating it like the arm of a clock a total of 1.2 minutes. This minimal rotation would be impossible for the human eye to detect.

In terms of the frontal plane HAV controversy, the new study from Campbell and colleagues does not close the book or “put the issue to bed” as Dr. DeHeer asserts in his recent DPM Blog. It simply raises more questions and cautions against doing surgical procedures that correct frontal plane deformity based upon plain radiographic criteria.

References

1. DeHeer P. Hallux valgus and frontal plane deformity: why are some surgeons still not getting it? Podiatry Today DPM Blog. Available at https://www.podiatrytoday.com/blogged/hallux-valgus-and-frontal-plane-deformity-why-are-some-surgeons-still-not-getting-it . Published Oct. 12, 2018.
2. Campbell B, Miller MC, Williams L, Conti SF. Pilot study of a 3-dimensional method for analysis of pronation of the first metatarsal of hallux valgus patients. Foot Ankle Int.2018; 1071100718793391.
3. Hatch D, Santrock RD, Smith B, Dayton P, et al. Triplane hallux abducto valgus classification. J Foot Ankle Surg. 2018; 57(5):972–981.
4. USPTO patent full-text and image database. Available at https://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2&f=G&l=50&co1=AND&d=PTXT&s1=9,622,805&OS=9,622,805&RS=9,622,805 .
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8. Richie D. New study fuels controversy over frontal plane HAV correction. Podiatry Today DPM Blog. Available at https://www.podiatrytoday.com/blogged/new-study-fuels-controversy-over-frontal-plane-hav-correction . Published Jan. 30, 2018.
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