Met Dome
Metatarsal (met) domes have long been used to reduce metatarsal head pressures to aid symptoms of metatarsalgia. HealthyStep has chosen a teardrop-shaped design because this profile has been far more researched than most other types of met domes.
This is a thermoplastic polyurethane (TPU) addition suitable for application to the underside of the X-Line and Alleviate Evolve ranges of insoles as well as the Arch Angel Fallen Arch, Active, and Hike insoles. It is also suitable for use on the anterior surface profile of the Vectorthotic and Alleviate Select.
£1.50
Product Description
Suitable for all HealthyStep’s total surface-contact orthoses.
X-Line
Condition Specific
Alleviate
Arch Angel Fallen Arch, Active and Hike Insole
How to fit met domes
HealthyStep’s clinical experts advise temporary fixation until patients have tried some walking around the clinic to assess comfort and symptom relief. Once the patient is happy with the placement of the metatarsal dome, fitting is simple. Just peel off the backing and apply it as indicated below.
It is also possible to apply the metatarsal dome to either the top of a Vectorthotic of Alleviate Select to the top shell surface or under the top cover as indicated below.
Although classically positioned just behind the central metatarsal heads, studies show that more proximal placements still produce similar effects. Therefore, the position of the best metatarsal dome placement can vary, depending on where the patient feels to gain the most comfort and benefit. Temporary fixation with a small piece of double-sided tape is recommended until the patient feels happy within a few minutes of walking, before finally setting the position.
Although usually beneficial for most causes of metatarsalgia, we recommend caution when metatarsal shaft stress fractures or pre-stress fractures are suspected/diagnosed. This is because met domes tend to increase metatarsal shaft loading time, which could be adverse for these fatigue fractures located within the shaft, rather than at the metatarsal neck.
Studies have reported a reduction in absolute peak pressures and peak pressure loading rates. with the use of metatarsal domes. This possibly results from increasing or maintaining the metatarsal angle of declination during late midstance when metatarsal stresses are rising. The 2nd and 3rd metatarsals should have the highest declination angles. We believe that curving and slightly raising the areas under the central metatarsal shafts is so beneficial, that all HealthyStep’s total-support contact insoles (flat-based) have a metatarsal support profile built-in.
By adding a met dome on HealthyStep’s insole, forces can be delayed from loading the metatarsal heads by redirecting stresses towards the metatarsal shafts. Maintaining appropriate metatarsal declination angles before heel lift is likely to assist the ability for digits to start to extend more freely, once the heel has lifted. This could offer an important benefit for patients who pronate across their forefoot excessively, causing too much splay. However, it can also be theorised that met domes assist in decreasing the radius of curvature (increasing the curve sharpness and shortening the span distance) of both the metatarsal heads in the horizontal plane and across the transverse vault profile across the metatarsal shafts in the forefoot.
Normally, the forefoot stiffens as it curves transversely just before and during heel lift (A). This prevents excessive forefoot splay, and increases the horizontal curve between the metatarsal heads, which helps stiffen the foot from the forefoot to the heel across the midfoot (B). There is an increasing foot-stiffening curvature both behind the metatarsal heads and across the tarsometatarsal joints during both late midstance and heel lift (C).
Through engineering laws, this effect can assist forefoot stiffening just prior to and during heel lift, making metatarsal head and metatarsophalangeal (MTP) joint stability easier to achieve. This effect might explain why metatarsal domes seem to be able to reduce multiple causes of metatarsalgia. These include plantar digital neurofibroma (Morton’s neuroma), MTP joint capsulitis and capsular tear, plantar plate tears, metatarsal neck-head bruising (bone marrow lesions), digital flexor tendinopathies, and cutaneous forefoot lesions such as corns and callus.
Thus, placing a met dome behind the metatarsal head can increase the transverse curvature (A) and horizontal curvature, limiting amounts of forefoot splay (B). This makes the curving of the transverse plane of the forefoot and midfoot easier while rising curvatures shorten the span distance under the foot, from left to right (C). These are all events that under the laws of engineering, will stiffen the foot to aid acceleration forward during heel lifting. Any anatomy under higher stress at this time is likely to receive benefits.
Although met domes tend to be attached centrally under the forefoot, other placements can be considered. If the metatarsalgia is more medial such as centred to the 2nd metatarsal head or the sesamoids of the hallux, the met dome can be attached more medially to the orthosis. Alternatively, if symptoms are more laterally orientated, such as located to the 4th and 5th metatarsal heads, consider a more lateralised placement for the met dome.
