08/01/2024
Use of Morton's Extensions and Reverse Morton's Extensions on Foot Orthoses for Hallux Limitus/Rigidus and Other Pathologies
In 1935, Dudley J. Morton described how the first metatarsal segment of some feet could be "hypermobile". As a result of his discovery, Morton designed an in-shoe orthosis with a first metatarsal head extension to treat this condition (Morton DJ: The Human Foot: Its Evolution, Physiology and Functional Disorders. Columbia University Press. Morningside Heights, New York, 1935). Today, this first metatarsal head extension on a foot orthosis is known as a "Morton's Extension".
The Morton's Extension (ME) is helpful in treating patients with plantar 2nd metatarsal head symptoms if the first ray has decreased dorsiflexion stiffness (i.e. is "hypermobile"). The ME will increase the ground reaction force (GRF) plantar to the first metatarsal head which will decrease the GRF plantar to the 2nd metatarsal head. The ME is also helpful in limiting hallux dorsiflexion during gait which may help relieve the pain in some patients with hallux limitus/hallux rigidus deformity.
On non-weightbearing clinical examination, if hallux dorsiflexion produces pain in the 1st metatarso-phalangeal joint (MPJ), then I will use a ME to help limit hallux dorsiflexion during gait which typically helps relieve pain at the 1st MPJ in these patients during gait. One must be careful, however, when using a ME on a foot orthosis, since the addition of an ME to a foot orthosis may produce excessive subtalar (STJ) supination during gait.
The opposite of the ME is the Reverse Morton's Extension (RME) which consists of a forefoot extension plantar to the 2nd through 5th metatarsal heads. The RME is a very useful addition to orthoses for the treatment of sesamoiditis, peroneal tendinopathy, lateral ankle instability and also functional hallux limitus.
For functional hallux limitus, if hallux dorsiflexion is non-painful on non-weightbearing examination, then I will use the RME added to an orthosis to help encourage greater hallux dorsiflexion and better function during gait. Of course, care must be taken if too thick of an RME is used in the orthosis since it can, on occasion, cause sub-2nd/3rd metatarsal head pain or increased STJ pronation during gait.
Both the ME and RME modifications are very useful foot orthosis modifications which, with proper clinical use, can mean the difference between success or failure with custom foot orthoses. Every podiatrist and foot-health clinician should be aware of the clinical usefulness of both the ME and RME orthosis modifications in order to optimize their patient's gait and minimize their pain and disability.
