Functional hallux limitus

Functional hallux limitus is generally defined as a deformity of the first metatarsophalangeal joint that acts to restrict the range of movement of dorsiflexion during the propulsive phase of gait. (Chapman C.,1997)
Different authors refine this basic definition further, some adding a further qualification that it is defined by a reduction of the range of dorsiflexion to less than 65 degrees. (Camasta C A.,1996). If the range is reduced to less than 5 degrees then the term Hallux rigidus is generally applied and is a subdivision of the clinical spectrum of functional hallux limitus. For the sake of completeness we should record that the normal range is generally 65-75 degrees of dorsiflexion.
We should also define the difference between the structural and functional varieties of this condition. The functional variety of the condition is diagnosed only if the restriction in the range of movement is apparent during weightbearing (and by definition is not present during passive, non-weightbearing movement). The structural variety exhibits a restriction of movement in both eventualities. (Dananberg H J et al 1996),
The assessment and diagnosis of functional hallux limitus is made either on clinical examination and history or with the assistance of formal gait assessment. As far as the latter is concerned, it is manifest as a biomechanical disability that has the predisposition to result in a comparatively ineffective propulsive mechanism (of varying degrees of severity) during the toe-off phase of the gait cycle. It can be accompanied by forefoot metatarsalgia together with other abnormalities of gait pattern (Townley and Taranow, 1994)
The definition of a successful treatment is :
To eliminate pain, restore motion, and maintain the strength and stability of the great toe, but must also reconstitute the normal distribution of weightbearing stresses sustained by the transverse metatarsophalangeal arch of the forefoot. (Townley and Taranow, 1994, p.575).
Aetiology of the condition
This is, to some extent a matter of controversy, as there are thought to be a number of independent but not mutually exclusive theories on the issue. (Laing P.,1995). Many authorities agree that the basic pathology stems from first ray hypermobility which, in itself is secondary to abnormal pronation. (Jahss M.,1982)
In lay terms this means that the ray is moving when it should be stable. The fundamental issue here is one of abnormal pronation. During propulsion the subtalar joint is pronated and the midtarsal joint is mobile when it should be locked. This allows the first metatarsal to be hypermobile.. this results in the first metatarsal dorsiflexing when it should be plantarflexing. The less the ability of the first metatarsal to plantarflex, the less becomes the ability of the first metatarsophalangeal joint to move and the greater becomes the need for compensatory mechanisms to come into play.
How the condition affects the gait cycle
The restriction of flexion in the movement of the of the first metatarsophalangeal joint manifests itself in a number of ways that can be either directly attributable to the condition or also compensatory mechanisms that allow for normal propulsive gait to be accomplished.
At the most basic level, the condition affects the ability of the foot to move fully over the hallux when the forefoot is planted on the ground. The degrees of impairment are variable (right up to hallux rigidus) and tend to progress with both age and length of time that the condition has been present. (Root M L et al 1987),
Typical signs associated with functional hallux limitus can be pronation of the feet while standing and walking. They will have varying degrees of reduced propulsivity from their gait. They can have either an abductory twist during the gait cycle or can demonstrate an abnormally abducted angle of gait and associated delay in the heel off segment of the gait cycle. (Light M R.,1996)
The early stages of the condition (typically in the younger patient) can go unnoticed and undiagnosed but as the condition becomes more advanced and obvious, compensatory changes in the gait cycle can become more apparent and pronounced. Progressive hypopropulsion, varying degrees of pelvic tilt and rounded shoulders are the more progressive accompaniments of the severe condition as the body attempts to compensate for the mechanical disadvantage of the condition. (Dananberg. HJ 1993)
The use of orthoses for functional hallux limitus
Because we have presented evidence to suggest that the basic functional abnormality in functional hallux limitus