Orthotic Posting

In order to better understand the advantages of using heel stabilisation as a method of correcting foot posture and joint alignment, it is essential to gain a deeper knowledge of the process of orthotic posting first.

Employed with the purpose of managing the pronation and supination of the foot, posting is a process which involves making modifications to the anatomy of the orthotic, by tilting certain aspects of the shell or insole to control motion and joint forces.

The goal is to improve the stability of the medial column by taking into account the plantar angles of the forefoot and heel, the intended level of control and the ranges of motion available.

This could be done either on the positive cast (intrinsic) or on the orthotic shell (extrinsic), which can be combined at the rearfoot and forefoot in different ways, to produce a countless number of orthotic designs. 

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More suitable for supporting a varus or valgus forefoot deformity, intrinsic posting does not entail the addition of any material to the outside of the shell which results in an orthotic that is less bulky.

Intrinsic forefoot posting incorporates changes to the forefoot of the positive cast, specifically to the distal one-third of the shell. This is done through the addition of plaster to the plantar surface of the metatarsalphalangeal (MTP) joints.

Although such an orthotic can be used with great ease, especially with tight footwear, it does not efficiently control the compensatory pronation commonly associated with foot conditions.

Another method used in this regard is intrinsic rearfoot casting. This involves the removal of plaster from the medial portion of the plantar heel of the positive cast thereby creating a flattened area in the heel cup of the shell.

While the increased supination that follows may correct the hyperpronation for a certain period of time, such a device fails to provide for the optimal positioning of the joints and the foot, which is necessary to facilitate the optimal functioning of the entire musculoskeletal system.

Extrinsic posting requires the addition of wedges to the outer shell of the orthotic device.

In the case of extrinsic rearfoot posting, material is applied to the calcaneal region of the shell to angle it either medially or laterally, and to control movement of the calcaneus during the stance phase of gait.

An extrinsic forefoot post, on the other hand, comprises of wedging the forefoot into its desired position. Such a method helps to effectively distribute ground-reactive forces but may not allow the metatarsal heads to reach the surface and could instead lead to constriction of the metatarsalphalangeal joints.

Studies have proven the superiority of mediolongitudinal-arch-supported orthotics such as the MASS4D® orthotic over forefoot- and rearfoot-posted orthotics**.

MASS4D® does advocate the use of lateral posting to aid in controlling excessive supination and calcaneus invention. It’s important to further emphasise that certain foot positions that are truly rigid in nature are managed with corrective posting techniques.

Heel stabilisation and the full contact 3-point base involving the calcaneus, the first and fifth MTP allow for decreased pressure on the lateral metatarsal heads and increased pressure under the first metatarsal head at toe-off, therefore making it a much more effective device in comparison.

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References:

1. Brad Hodgson, Laurie Tis, Steven Cobb, Shawn McCarthy, and Elizabeth Higbie (2006) The Effect of 2 Different Custom-Molded Corrective Orthotics on Plantar Pressure. Journal of Sport Rehabilitation: January 17, 2006, Vol. 15, pp. 33-44
2. Robert A. Donatelli (2006) Sports-Specific Rehabilitation: October 1, 2006, Chapter 10, pp. 159-165
3. Warren Turner, Linda M. Merriman (1997) Clinical Skills in Treating the Foot: 1997, Chapter 24, pp. 273-276

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