**1. Introduction**

Hallux Abductus Valgus (HAV) is a pathological subluxation of the first metatarsophalangeal joint (IMPJ) with lateral deviation of the proximal phalanx of the hallux bone (PPH) toward abduction and valgus direction in both the transverse and frontal planes of motion, respectively. There is also deviation of the first metatarsocuneiform joint (IMCJ) through the first metatarsal bone (IMTT) toward

adduction and valgus direction in both transverse and frontal planes of motion, respectively. There are occasionally bony enlargements of the first metatarsal head (also called a "bunion") [1–3]. The IMPJ bears 80% of the body load without help of any structure in heel-off phase, and this makes it a more sensitive joint to biomechanics deformities such HAV [1].

The etiology of HAV can have multiple origins, and there are intrinsic and extrinsic factors in play [4–9]. Intrinsic factors include hyperpronation [5,10], soft tissue weakness [1], and hyperlaxity with medial longitudinal arch collapse [11,12]; Windlass mechanism failure [7], first ray hypermobility [8], and female sex [13–15] have been linked with HAV growth. As extrinsic factors, the use of high-heel shoes has also been detected as a possible cause of HAV development: The typical high-heeled shoe for women can lead to bad body repercussions and be detrimental to bone mineralization [16], rear foot instability [17], body mass center changes [18], biomechanics gait changes [19,20], and general damage health [21].

Some authors have reported increases in concentrate load under the forefoot with high heeled shoes [22–25], and this condition can predispose the subject to HAV development [26]. A few studies have speculated that the current narrow box of high-heeled shoes are not the only cause of HAV because isolated high-heel shoes might cause weight to be placed on the forefoot, and this may overstretch the toes and lead to the development of splayfoot [1,27,28]. However, this has not been reported in the literature.

The 2D [29] and 3D kinematic movements of PPH and I MTT bone deviation during gait in subjects with and without HAV has shown the relationship between the rearfoot and midfoot eversion with respect to the first ray hypermobility and the presence on HAV [10,30]; other groups have studied the kinematic effects of improvements in taping in subjects with HAV during gait [31] or the negative effects of HAV surgery to normal ambulation [32]. Other work studied the kinematics effects on IMPJ using foot orthoses that incorporated forefoot and rearfoot posting—the results showed no negative effects on mobility [33]. One prior study [34] identified kinetic evidence of wearing 5 cm-heeled shoes during gait can lead to HAV development and an increase in hallux dorsiflexion in the final push-off phase; however, no report has described the transverse or frontal plane motion of the PPH or IMTT.

Therefore, the goal of this study is to determine how the heel height affects PPH and IMTT bone deviations either in the three planes of motion in static conditions and during the dorsiflexion of the IMPJ sequence (push-off phase of the dynamic condition) regardless of toe box of the shoe. The results can show if there is some movement related to HAV deviation that is characterized by PPH in abduction (away to medial body line) in transverse plane and valgus deviation in frontal plane toward the IMPJ [2] and/or the adduction deviation of the IMTT (toward medial body line) regarding the second MTT in transverse plane and the presence of the valgus in the frontal plane toward the IMCJ [2].
