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I have read from several sources that both a long OR short first metatarsal causes hallux limitus/rigidus, without an explanation.

Does anyone have any proven evidence that this is the case, and explain how opposite deformities can result in the same process?

Thanks,

Nick

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Nick,

Most of the evidence relating metetarsal length variations and hallux limitus/rigidus stems from simple case series studies.

To my knowledge, the only case-control study addressing this was by Zgonis et al., who compared radiographic features in 51 hallux rigidus cases to 51 controls, and reported that the first metatarsal was slightly longer in the hallux rigidus group (mean of 68mm compared to 65mm). However, first metatarsal protrusion distance, which is a more functional indicator of the length of the first metatarsal as it takes into account transverse plane angulation, did not differ between the groups.

Cheers,

Hylton


Zgonis T, Jolly GP, Garbalosa JC, et al. The value of radiographic parameters in the surgical treatment of hallux rigidus. Journal of Foot and Ankle Surgery 2005; 44:184-189 (link)

Nick:

I don't think we have any "proven evidence" of anything about foot pathology and foot biomechanics, so hallux limitus is no different.

Feet that have long first metatarsals need to supinate more at the STJ during propulsion to allow the first metatarsal head to have a large enough reduction in ground reaction force (GRF) to allow the necessary first ray plantarflexion for adequate hallux dorsiflexion to occur during propulsion. If the foot with a long first metatarsal just supinates the normal amount at the STJ during propulsion, then it will develop functional hallux limitus since it must supinate more to unload the first metatarsal head sufficiently to allow hallux dorsiflexion to occur. In the foot with a long first metatarsal, an argument could be made that inadequate STJ supination is responsible for the structural hallux limitus deformity that develops over time due to the excessive dorsal 1st MPJ compression forces that result during propulsion when the hallux is unable to dorsiflex over a non-plantarflexing first ray.

With a short first metatarsal, structural hallux limitus does not seem to occur very commonly. Rather, than developing structural hallux limitus, functional hallux limitus occurs more commonly in feet with a short first metatarsal due to the excessive late midstance pronation moments and late STJ pronation motion that results. Late midstance pronation creates a situation where the STJ axis becomes more medially deviated, the increased STJ pronation moment causes the longitudinal arch to become flatter during late midstance which then increases the tensile force within the medial band of the central component of the plantar aponeurosis. In turn, this mechanical scenario results in functional hallux limitus. Recent research does not support the theory proposed by some podiatrists that functional hallux limitus is the primary etiology of longitudinal arch flattening during gait (Van Gheluwe B, Dananberg HJ, Hagman F, Vanstaen K: Effects of hallux limitus on plantar foot pressure and foot kinematics during walking. JAPMA, 96:428-436, 2006). Rather, it is the common scenario of medial longitudinal arch flattening and STJ medial deviation during late midstance which is responsible for the vast majority of cases of functional hallux limitus.

In other words, long first metatarsals cause more tendency toward structural hallux limitus than do short first metatarsal. Functional hallux limitus is nearly always present early on in life in individuals with long first metatarsals and these feet have a strong tendency to develop a structural hallux limitus. However, patients with short first metatarsals have more tendency toward functional hallux limitus developing as they grow older and don't seem to have a strong tendency toward developing the osseous changes associated with structural hallux limitus as they age.

Proven evidence?.....no....consistent with clinical observation and biomechanics principles?.....yes.

__________________
Sincerely,

Kevin

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Kevin A. Kirby, DPM
Adjunct Associate Professor
Department of Applied Biomechanics
California School of Podiatric Medicine at Samuel Merritt College

e-mail: kevinakirby@comcast.net

Private Practice:
107 Scripps Drive, Suite 200
Sacramento, CA 95825 USA
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