Extensor hallucis capsularis tendon
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The extensor hallucis capsularis tendon, also known as secondary extensor hallucis longus, accessory extensor tendon of the first metatarsophalangeal joint, extensor ossis metatarsi hallucis or extensor ossis primi internodii hallucis is an accessory tendon or muscle of the ankle and an anatomical variant. Prevalence has been estimated up to 90% 1-3 and in ~14% it might be suitable to be used as a tendon graft 3.
- origin: extensor hallucis longus muscle or tendon
- insertion: dorsomedial aspect of the first metatarsophalangeal joint capsule and/or base of the first proximal phalanx
- agonist of the extensor hallucis longus, dorsiflexion
- stabilization of the first metatarsophalangeal joint capsule during hallux extension
The extensor hallucis capsularis tendon originates from the extensor hallucis tendon or muscle and travels along the anterior aspect of the ankle medially and parallel to the extensor hallucis longus within the extensor compartment to insert onto the first metatarsophalangeal joint capsule 1-3.
The extensor hallucis capsularis tendon is thin usually ≤4 mm in width that can be found medial to the extensor hallucis longus tendon.
History and etymology
The extensor hallucis capsularis tendon was first reported by the Irish anatomist Alexander MacAlister (1844-1919) 6 in 1886 2,5.
The tendon can be used as an autologous tendon graft and has been found especially useful in hallux dysfunction 1-3.
- 1. Aparisi Gómez M, Aparisi F, Bartoloni A et al. Anatomical Variation in the Ankle and Foot: From Incidental Finding to Inductor of Pathology. Part I: Ankle and Hindfoot. Insights Imaging. 2019;10(1):74. doi:10.1186/s13244-019-0746-2 - Pubmed
- 2. Jarusriwanna A, Thamphongsri K, Chuckpaiwong B. Frequency and Characteristics of Extensor Hallucis Capsularis: A Cadaveric Study. J Med Assoc Thai. 2016;99(11):1215-9. - Pubmed
- 3. Boyd N, Brock H, Meier A, Miller R, Mlady G, Firoozbakhsh K. Extensor Hallucis Capsularis: Frequency and Identification on MRI. Foot Ankle Int. 2006;27(3):181-4. doi:10.1177/107110070602700305 - Pubmed
- 4. Park J, Choi Y, Park K et al. Independent Muscle of Extensor Hallucis Capsularis: A Cadaveric Case Report. Surg Radiol Anat. 2020;43(7):1041-4. doi:10.1007/s00276-020-02592-7 - Pubmed
- 5. Macalister A. Notes on muscular anomalies in human anatomy. Proc R Irish Acad 1866; 9:444-69.
- 6. Prof. Alexander Macalister, F.R.S. (1844–1919). Nature. 1944;153(3888):554-554. doi:10.1038/153554b0