what-when-how
In Depth Tutorials and Information
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Importance of the flex line in the forefoot
If a full-length foot orthosis is chosen, it is critical to ensure that the fore-
foot area, especially the medial/lateral line where the forefoot flexes in gait,
is not so stiff that it prevents sufficient dorsiflexion of the toes. A stiff
forefoot area will resist toe dorsiflexion and could have significant effects
on gait. The patient may attempt to obtain the required 'dorsiflexion', or
rather forward motion of their centre of mass, from elsewhere, such as
the knee or hip. Alternatively, they may simply lift their foot off the ground
vertically and much earlier, resulting in a rather apropulsive and inefficient
gait. If the material is very stiff, it is also likely to elevate forefoot plantar
pressures. As a general rule, the forefoot area should be more flexible
than the sole unit of the footwear the patient is wearing, assuming the
footwear is deemed suitable.
There may be occasions when reducing toe dorsiflexion is advanta-
geous, for example in cases of painful dorsal osteophytes or metatarsal
head capsule pain. This is best achieved using a stiff sole unit on the
footwear rather than a stiff orthosis.
Biomechanical objectives of foot orthoses
Foot orthoses are used for a wide range of clinical symptoms but underly-
ing these symptoms are three biomechanical objectives:
1.
To alter foot motion.
2.
To alter stress experienced by internal hard and soft tissues.
3.
To alter the distribution and magnitude of load applied to the plantar
surface.
These are highly interdependent objectives. By influencing the movement
of the foot as it contacts the ground, bears load and pushes off from the
ground into the next step, a foot orthosis can influence the end position
and range of motion of specific joints in the foot. These will impact on the
precise orientation of bones relative to each other and orientation of the
foot relative to the supporting surface. Through these changes a series of
other biomechanical effects might be expected. The size and shape of the
contact area between two articulating bones will change, and the stress
experienced by ligaments and joint capsule structures, which stretch as
the joint moves, will be affected. Not reaching the absolute end range of
motion at a joint is likely to place less stress on passive ligamentous struc-
tures and the joint capsule, whose purpose is to resist motion, reducing
the potential for ligament and capsular damage. Any increase in the
