Forefoot extensions are defined as starting in the front of the plastic, and can be used to: (1) accommodate or off weight, (2) wedge (varus or valgus), (3) support, (4) cushion, and (5) restrict.
The images below are two commonly used forefoot extensions applied to maintain varus or valgus support past the end of the plastic. These wedges can be various thicknesses or degrees. Remember on average 1/16 of an inch is 1 degree correction.
Forefoot extensions are used on 60-70% of my walking orthoses, and 100% of my athletic orthoses (when there is room in the shoe of course). The Classic Morton's extension is a forefoot extension under the 1st metatarsal head to re-balance the metatarsals due to a long 2nd metatarsal. Forefoot extensions can be a vital orthotic component to hold varus and valgus corrections as the patient runs onto the ball of the foot. Any painful metatarsal can be cushioned or off loaded, and this works well with metatarsal pads proximal to the soreness.
Some of the general rules I use for forefoot extensions are (1) try to keep the thickness of one side the same as the other side (if you have 2-3 mm difference ask the patient if they think that it affects their gait), (2) if you make a hole for a painful possibly dropped metatarsal by accommodating either side, you must add a met pad or support proximally to prevent worsening of the collapse, (3) if you are adding varus or valgus wedging to both sides, try to make them asymmetrical as 95% of the time this function is different from right to left.
Forefoot extensions by themselves do not limit motion of the MPJs, as there is still motion between the plastic and extension distally. However, adding bulk to the forefoot, in patients especially who have difficulty pushing off, can become very restrictive. Ask all of your forefoot extension patients if it is harder to push off or roll through their feet. If I need bulk, I cut striations in the material (as demonstrated in my heel lift post weeks ago) to make it easier to push off.
