Definition

Sesamoiditis is inflammation and pain of the sesamoid apparatus under the first metatarsal head.

Overview

Sesamoiditis occurs when repetitive or excessive pressure is placed on the sesamoid bones, eroding the dorsal cartilage and leaving the subchondral bone exposed. Increased pressure and stress at the sesamoids can be caused by an everted rearfoot which drives the medial forefoot into the ground, or an everted forefoot (forefoot valgus). Sesamoiditis pain is often intractable. Effective treatment should reduce stress on the sesamoids which will reduce the inflammatory response.

Clinical Goal for Orthotic Treatment

To transfer force off of the painful sesamoid(s) to decrease pressure on the sesamoid apparatus.

Prescription

To prescribe this device check “Sesamoiditis” under the Pathology Specific Orthoses section (Part A) of the prescription form.

Sesamoiditis Prescription Recommendations

• Polypropylene Shell – semirigid with no distal bevel
  • The lack of distal bevel increases the thickness of the distal edge of the orthosis. This transfers force from the metatarsal head to the 1^st metatarsal neck and the lateral forefoot.
• Wide Width
  • A wider width through the arch increases surface area under the arch, effectively reducing pressure on the metatarsal heads.
• Minimum Cast Fill
  • Minimum cast fill creates an orthosis that conforms closely to the arch of the foot and shifts pressure proximally from the metatarsal heads to the arch area.
• Medial Skive – 2mm
  • The medial heel skive creates a stronger supinatory moment arm around the subtalar joint (STJ) axis to reduce excessive subtalar joint (STJ) pronation and heel eversion
• Inversion – 3 degrees
  • Inversion of the positive cast increases arch height shifting pressure from the first metatarsal head to the arch of the foot.
• EVA Cover to Toes
• Reverse Morton’s Extension
  • Transfers pressure from the first metatarsal head and sesamoids to the other metatarsal heads.

Summary

Sesamoiditis is caused by increased ground reactive force (GRF) under the first metatarsal head resulting in inflammation and pain of the sesamoids. Orthoses designed to treat this condition should reduce pressure on the first metatarsal head by transferring pressure proximally to the metatarsal necks and/or laterally to the other metatarsal heads. ProLab clients can contact a Medical Consultant with questions about the treatment of this pathology.

References

1. Chalmers AC, Busby C, Goyert J, et al. Metatarsalgia and rheumatoid arthritis-a randomized, single blind, sequential trial comparing two types of foot orthoses and supportive shoes. J Rheumatology, 27:1643-7, 2000.
2. Postema K, Burm P, Zande M, et al. Primary metatarsalgia: The influence of a custom molded insole and a rockerbar on plantar pressure. Prosthet Orthot Int 22:35-44, 1998.
3. Munuera PV, Domínguez G, Lafuente G. Length of the sesamoids and their distance from the metatarsophalangeal joint space in feet with incipient hallux limitus. J Am Podiatr Med Assoc. 2008 Mar-Apr;98(2):123-9.
4. Largey A, Canovas F, Bonnel F. Degenerative changes of the metatarso-sesamoido-phalangeal complex. Morphologie. 2008 Mar;92(296):37-46. Epub 2008 May 21. French.
5. Munuera PV, Domínguez G, Reina M, Trujillo P. Bipartite hallucal sesamoid bones: relationship with hallux valgus and metatarsal index. Skeletal Radiol. 2007 Nov;36(11):1043-50. Epub 2007 Sep 2.
6. Seder JI. Sesamoiditis, JAPMA June 64 (6) 444-6, 1974
7. Reeves M. Sesamoiditis, Journal American Veterans Medical Association Sept:15 199(6) 682, 1991