What Joint Should Surgeons Rotate In HAV Correction?

Several surgical hardware companies are offering technologies that provide a new approach to correcting hallux abducto valgus (HAV) deformity. The goal is to correct a perceived “pronation” deformity of the first metatarsal.¹ Herein is the first myth of this new approach to bunion surgery. The term pronation describes a triplane motion of a skeletal segment in the direction of dorsiflexion, eversion and abduction. With a HAV deformity, the first metatarsal moves in the direction of adduction, not abduction.

The new HAV surgical approach involves rotating the first metatarsal in the direction of inversion, based upon a perception that this bone becomes everted as the deformity progresses.^2,3 However, there are multiple quality studies validating the direction of range of motion of the first ray of the human foot and showing that the first metatarsal would have to move in the combined direction of plantarflexion with eversion.^4-6 This would contradict the well-accepted notion of excessive dorsal mobility of the first ray in patients with HAV deformity.

Proponents of frontal plane correction of the first metatarsal in HAV surgery are only able to explain the contradictory motion of the first metatarsal (dorsiflexion/eversion) by challenging the well-accepted, well-proven notion of the axis of motion of the first ray, despite providing no data to support such a challenge.^2,7 As a co-author of one of the studies validating the true axis of rotation of the first ray, I question the validity of the unfounded notion of first ray “pronation” in HAV deformity.^8-10

Among the many flaws in the new theory of frontal plane eversion of the first metatarsal in HAV deformity is the reliance on plain radiographs using the axial sesamoid view of the foot.³ The positioning device physicians use for the axial sesamoid view will dorsiflex the hallux and plantarflex the first ray. Clearly, this will automatically cause the first metatarsal to evert. Secondly, studies showing evidence of “pronation” of the first metatarsal in patients with HAV deformity fail to take into account the position of the entire foot when the imaging studies were performed.^3,11

The first metatarsal position relative to the supportive surface is more dependent on position of the entire foot rather than motion at the two discreet joints of the first ray (first tarsometatarsal (TMT) joint and medial naviculocuneiform joint). Indeed, there is accumulating evidence that patients with HAV deformity have significant pronation of the joints proximal to the first ray, which can have profound influence on the perceived position of the first metatarsal with weightbearing imaging studies.^12,13

Consider the study by Kimura and coworkers, who used three-dimensional models to measure motion of the bones of the medial column of the foot in patients with HAV deformity in comparison to healthy controls.¹⁴ By comparing non-weightbearing and weightbearing computed tomography (CT) images, one can evaluate the effect of loading on overall motion at each joint of the medial column. As expected, at the first TMT joint, the first metatarsal moved in a significantly greater direction of dorsiflexion, inversion and adduction in HAV patients in comparison to healthy controls. This follows the axis of motion of the first ray described by Hicks, Kelso and others.^4-6 At the naviculocuneiform joint, the medial navicular actually moved in the direction of eversion in patients with HAV deformity and in the direction of inversion in healthy controls although the magnitude was only a few degrees. At the talonavicular joint, the navicular moved on the talus in the direction of eversion in both subject groups and the magnitude of frontal plane motion at this joint exceeded the frontal plane motion at the joints of the first ray located more distally.  

To sum up the Kimura and colleagues study, frontal plane motion with loading in patients with HAV deformity resulted in: 

• the first metatarsal moving 4.9 degrees into inversion; 
• the medial cuneiform moving 1.5 degrees into eversion; 
• the navicular moving 9.6 degrees into eversion; and  
• the net motion of the entire medial column being 6.2 degrees of eversion.

This study suggests that in patients with HAV deformity, the overall significant contribution of eversion motion occurring at the talonavicular joint overrides the inversion motion of the first TMT joint, thus placing the first metatarsal everted to the ground in static stance. Ironically, a surgical procedure to invert the first metatarsal at the first TMT joint would actually accentuate the frontal plane deformity at this joint in HAV patients according to the study by Kimura and colleagues.¹⁴ To accurately reduce the frontal plane eversion deformity of the medial column in patients with HAV deformity, corrective rotation would have to take place at the talonavicular joint. A derotational Lapidus procedure to invert the first metatarsal in HAV surgery not only accentuates the already present inversion deformity at the first TMT joint, it also neglects the true location of eversion, which is actually coming from the talonavicular joint.  

This raises a significant question: Do we need to correct rearfoot alignment in order to achieve better outcomes in HAV surgery? I welcome your comments.

Dr. Richie is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt University in Oakland, Calif. He is a Fellow and Past President of the American Academy of Podiatric Sports Medicine. Dr. Richie is a Fellow of the American College of Foot and Ankle Surgeons.

References

1. 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;39(12):1449-1456.
2. Dayton P, Kauwe M, Feilmeier M. Clarification of the anatomic definition of the bunion deformity. J Foot Ankle Surg. 2014; 53(2):160–163.
3. Hatch D, Santrock RD, Smith B, Dayton P, Weil L Jr. Triplane hallux abducto valgus classification. J Foot Ankle Surg. 2018; 57(5):972–981.
4. Hicks JH. The mechanics of the foot. Part I: the joints. J Anat. 1953; 87(4):345–357.
5. Kelso SF, Richie DH Jr, Cohen IR, Weed JH, Root ML. Direction and range of motion of the first ray. J Am Podiatr Med Assoc. 1982; 72(12):600–605.
6. Johnson C, Christensen JC. Biomechanics of the first ray part 1. The effects of the peroneus longus function. A three dimensional kinematic study on a cadaver model. J Foot Ankle Surg. 1999; 38(5):313–321. 
7. DeHeer P. Hallux valgus and frontal plane deformity: why are some surgeons still not getting it? Podiatry Today. 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. Accessed December 2, 2019.
8. Richie D. Questioning the notion of frontal plane correction for HAV deformities. Podiatry Today. Available at https://www.podiatrytoday.com/blogged/questioning-notion-frontal-plane-correction-hav-deformities. Published Dec. 6, 2016. Accessed December 2, 2019.
9. Richie D. New study fuels controversy over frontal plane HAV correction. Podiatry Today. Available at https://www.podiatrytoday.com/blogged/new-study-fuels-controversy-over-frontal-plane-hav-correction. Published Jan. 30, 2018. Accessed December 2, 2019.
10. Richie D. Hallux valgus and frontal plant deformity: why I still don’t get it. Podiatry Today. Available at https://www.podiatrytoday.com/blogged/hallux-valgus-and-frontal-plane-deformity-why-i-still-dont-get-it . Published October 17, 2018. Accessed December 2, 2019.
11. Kim Y, Kim SK, Young KW, Naraghi R, Cho HK, Lee SY. A new measure of tibial sesamoid position in hallux valgus in relation to coronal rotation of the first metatarsal in CT scans. Foot Ankle Int. 2015;36(8):944-952
12. Shibuya N, Kitterman RT, LaFontaine J, Jupiter DC. Demographic, physical, and radiographic factors associated with functional flatfoot deformity. J Foot Ankle Surg. 2014;53:168–172.
13. Galica A, Hagedorn TJ, Dufour AB, et al. Hallux valgus and plantar pressure loading: the Framingham foot study. J Foot Ankle Res. 2013;6:1-18. 
14. Kimura T, Kubota M, Taguchi T, Suzuki N, Hattori A. Evaluation of first-ray mobility in patients with hallux valgus using weight-bearing CT and a 3-D analysis system. A comparison with normal feet. J Bone Joint Surg Am. 2017; 99(3):247-55.