A hot topic in the area of surgical procedures for treatment of hallux abducto valgus (HAV) is the possible need for correction of frontal plane deformity of the first metatarsal. This concept has been presented several times in past years at the Annual Scientific Conference of the American College of Foot and Ankle Surgeons and will be presented again this year.1
The rationale for this new surgical approach is an assumption that the first metatarsal is “pronated” or everted with the HAV deformity. Thus, authors have proposed that a frontal plane correction, rotating the first metatarsal in the direction of inversion, is required to correct the deformity adequately.
For most of us who were well schooled in the pathomechanics of HAV deformity, this concept makes no sense at all. One has to ask: Who came up with this idea?
Scranton and Rutkowski in 1980 were among the first to describe a “pronated” position of the first metatarsal in HAV deformity.2 Eustace and colleagues documented a similar observation in 1993.3 Fourteen years later, Okuda made several radiographic measures of patients with HAV deformity and concluded that the first metatarsal was everted.4 In 2013, Okuda described a “abduction-supination osteotomy” of the first metatarsal for correction of HAV.5 Around the same time, DiDomenico presented a frontal plane correction of the everted alignment of the first metatarsal when performing a Lapidus procedure for HAV deformity.6
A series of papers authored by Dayton and coworkers, all published in the Journal of Foot and Ankle Surgery, have driven home the concept that the first metatarsal is everted in most patients with HAV and that this frontal plane deformity requires correction that is best combined with a Lapidus procedure.7-11 In these papers, the authors repeatedly challenge the original description of the axis of motion of the first ray of the human foot, originally described by Hicks.12 The justification for this challenge is the citation by Dayton and colleagues of two studies published almost 40 years ago by D’Amico and Schuster as well as Oldenbrook and Smith.13,14
The observation of isolated eversion of the first metatarsal with HAV deformity and the challenge of the Hicks description of the first ray axis of motion highlights the fallacy of the need to invert the first metatarsal in HAV surgery. I have a keen interest in this controversy as I participated in a study that clearly refuted the theory of motion of first ray motion as proposed by D’Amico and Shuster as well as Oldenbrook and Smith.15 Our study was designed by Root and conducted by a group of students at the California College of Podiatric Medicine in 1980. In this study of 24 cadaver specimens, we showed that the first metatarsal always inverts with dorsiflexion and everts with plantarflexion relative to the remainder of the foot.
In our paper, we addressed the errors made by others who observe an everted position of the first metatarsal when the foot moves into maximum end-range pronation.15 While the first ray dorsiflexes and inverts with foot pronation, movement of the entire foot into eversion/pronation carries the first ray into an overall position of eversion relative to the weightbearing surface. Herein is the major error in assuming that one must correct the first metatarsal into inversion in HAV surgery.
Radiographic measures of deformity and pathologies of the human foot measure angular relationships between segments of the foot itself. For example, the lateral talus-first metatarsal angle (Meary’s angle) or the AP talocalcaneal angle (Kite angle) measure the relationships of segments within the foot. The intermetatarsal angle in HAV deformity measures the transverse plane relationship of the first and second metatarsals. Surgical procedures correct the alignment of the first metatarsal relative to the second metatarsal. The axis of the first ray, described by Hicks, measures the direction of the first metatarsal motion relative to the second metatarsal. This axis dictates that the first metatarsal inverts with dorsiflexion, a fact that more recent studies have verified using more modern and accurate techniques than those utilized by Hicks.16,17
In all of the radiographic studies of HAV patients that have demonstrated an everted positon of the first metatarsal, the observation occurred with the foot on the ground and the plane of reference was the ground itself, not the second metatarsal. In static stance, the first ray drives into dorsiflexion by ground reaction forces. According to the well-proven notion of the Hicks axis, the first metatarsal will invert with dorsiflexion. If the foot itself moves into pronation, the first ray will potentially end up pronated or everted to the ground even though it is actually inverted relative to the second metatarsal and the remainder of the foot. Therefore, this everted position of the first metatarsal in patients with HAV is the result of a foot deformity, not a first metatarsal deformity.
Understanding the influence of overall foot position, it is not surprising that weightbearing radiographs consistently show an everted position of the first metatarsal in patients with HAV deformity. Studies have verified that the only way the first ray could move into eversion is if the first ray is actually plantarflexed from its neutral position (rarely seen in patients with HAV) or if the entire foot has pronated and carried the first ray into eversion (much more common with HAV deformity).15 In order to correct this everted position of the first metatarsal in patients with HAV deformity, a surgical procedure must correct pronation of the entire foot.
Consider a pediatric patient with femoral anteversion who has a resulting in-toed gait deformity. A compensation for femoral anteversion that occurs within the foot is subtalar joint pronation, which unlocks the midtarsal joint and results in forefoot abduction. With femoral anteversion, there will be an abduction deformity within the foot itself while the entire foot is actually adducted or in-toed from a more dominant deformity at the hip. No competent surgeon would correct the in-toed deformity in this child by operating on the foot itself when the cause of the transverse plane deformity lies more proximal. Furthermore, no surgeon would perform a procedure that would abduct the forefoot in this child with in-toed gait when this segment is already abducted.
The identical situation arises in patients with HAV deformity. Pronation of the entire foot causes the first metatarsal to be positioned in a pronated or everted position on the ground. The problem, therefore, is the position of the entire foot, not the first metatarsal. Why would a surgeon try to correct the frontal plane deformity of the foot by addressing the metatarsal itself? The first ray has compensated with dorsiflexion and inversion. Why would a surgeon rotate the first metatarsal further in the direction of inversion when the first metatarsal is already inverted relative to the rest of the foot?
Surgical procedures for HAV correct deformity of the first metatarsal relative to the second metatarsal and the rest of the foot, not relative to the ground. Therefore, surgeons should evaluate and correct the position of the first metatarsal relative to the second metatarsal, not to the ground. When one carries out accurate analysis of this relationship with weightbearing computed tomography studies of patients with HAV, it is clear that there is no frontal plane deformity of the first metatarsal.18 The proper way to correct the perceived everted position of the first metatarsal in patients with HAV deformity is to correct the overall foot alignment and not rotating the first metatarsal by itself in a direction contrary to its natural axis of motion.
1. American College of Foot and Ankle Surgeons. Available at http://www.acfas.org/uploadedFiles/_ACFAS_Home/Education_and_Professional_Development/Annual_Scientific_Conference/ASC_2017/2017%20Prelim%20Program_FINAL_11_1_16.pdf .
2. Scranton PE, Rutkowski R. Anatomic variations in the first ray part 1: anatomic aspects related to bunion surgery. Clin Orthop Rel Res. 1980; 151:244–255.
3. Eustace S, Obyrne J, Stack J, Stephens MM. Radiographic features that enable the assessment of first metatarsal rotation: the role of pronation in hallux valgus. Skeletal Radiol. 1993; 22(3):153–156.
4. Okuda R, Kinoshita M, Toshito Y, Jotoku T, Kitano N, Shima H. The shape of the lateral edge of the first metatarsal head as a risk factor for recurrence of hallux valgus. J Bone Joint Surg. 2007; 89(10):2163–2172.
5. Okuda R, Yasuda T, Jotoku T, Shima H. Proximal abduction-supination osteotomy of the first metatarsal for adolescent hallux valgus: a preliminary report. J Orthop Sci. 2013; 18(3):419–425.
6. DiDomenico LA, Fahim R, Rollandini J, Thomas ZM. Correction of frontal plane rotation of sesamoid apparatus during Lapidus procedure: a novel approach. J Foot Ankle Surg. 2014; 53(2):248–251.
7. 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 tarsal metatarsal arthrodesis for hallux abducto valgus: a case series and critical review of the literature. J Foot Ankle Surg. 2013; 52(3):384–454, 2013.
8. Dayton P, Feilmeier M, Hirschi J, Kauwe M, Kauwe JS. Observed changes in radiographic measurements of the first ray after frontal plane rotation of the first metatarsal in a cadaveric foot model. J Foot Ankle Surg. 2014; 53(3):274–278.
9. Dayton P, Feilmeier M, Kauwe M, Holmes C, McArdle A, Coleman N. Observed changes in radiographic measurements of the first ray after frontal and transverse plane rotation of the hallux: does the hallux drive the metatarsal in a bunion deformity? J Foot Ankle Surg. 2014; 53(5):584–587.
10. Dayton P, Kauwe M, Feilmeier M. Clarification of the anatomic definition of the bunion deformity. J Foot Ankle Surg. 2014; 53(2):160–163.
11. Dayton P, Kauwe M, DiDomenico L, Feilmeier M, Reimer R. Quantitative analysis of the degree of frontal rotation required to anatomically align the first metatarsal phalangeal joint during modified tarsal-metatarsal arthrodesis without capsular balancing. J Foot Ankle Surg. 2016;55(2):220-5.
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14. Oldenbrook LL, Smith CE. Metatarsal head motion secondary to rearfoot pronation and supination: an anatomical investigation. J Am Podiatr Assoc. 1979; 69(1):24–28.
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18. Collan L, Kankare JA, Mattila K. The biomechanics of the first metatarsal bone in hallux valgus: A preliminary study utilizing a weight bearing extremity CT. Foot Ankle Surg. 2013; 19(3):155–161.