An Anatomical Study of Extensor Expansion of ThumbFunding None.
Introduction The presence of extensor expansion of the thumb has been reported in the literature and its mode of formation and contribution from the palmar muscles has been studied earlier. Yet, some authors deny its presence in the thumb.
Objective This article evaluates the presence of the extensor expansion of thumb (EET) and its formation and contributions from palmar muscles.
Methods Dissection was carried on the dorsum of the hand on 80 free upper limbs. The dorsum of thumb was carefully cleaned to look for the presence of extensor expansion. When present, its mode of formation and the contributing muscles were looked into. The mode of insertion of the extensor tendons onto the phalanges was also observed.
Results In all specimens, EET had tendons of extensor pollicis longus (EPL) and extensor pollicis brevis (EPB) along its central axis. It received expansion from abductor pollicis brevis (APB; 100%) and flexor pollicis brevis (FPB; 41.2%) on the lateral side, and adductor pollicis (AP; 100%) and first palmar interosseous (PI; 50%) on the medial side. Attachment of EPL to distal phalanx (DP) was seen in 45%, and to both phalanges in 55%. EPB insertion onto proximal phalanx alone, DP alone, and both phalanges was in 46.2, 25, and 23.75%, respectively.
Conclusion Extensor expansion was noted in all limbs studied. It is formed by the extensor tendons of the thumb with expansions from APB and AP on its margins. Contribution from the first PI and FPB was found to be variable. Differences in insertion of EPL and EPB to the phalanges were also noted.
08 April 2020 (online)
Thieme Medical and Scientific Publishers Private Ltd.
A-12, Second Floor, Sector -2, NOIDA -201301, India
- 1 Komatsu I, Lubahn JD. Anatomy and biomechanics of the thumb carpometacarpal joint. Oper Tech Orthop 2018; 28 (01) 1-5
- 2 Standring S. Gray’s Anatomy. The Anatomical Basis of Clinical Practice. 41st ed. New York: Elsevier Churchill Livingstone; 2016: 854-882
- 3 Joshi SS, Joshi SD, Athavale SA, Kishve PS, Jadhav SD. Dorsal digital expansion of thumb. Anat Soc India 2008; 57 (02) 135-139
- 4 Romanes GJ. Cunningham’s Textbook of Anatomy. 16th ed. Oxford, New York, Tokyo: Oxford University Press; 2017: 111-123
- 5 Spinner M. Kaplan’s Functional and Surgical Anatomy of Hand in Thumb. 3rd ed. PA, USA: J.B. Lippincott Company;
- 6 Kulkarni NV. Clinical Anatomy (A Problem Solving Approach). Vol. 1. 3rd ed. New Delhi: Jaypee Brothers Medical Publishers; 2016. Chapter 19 195
- 7 Lamb DW, Hooper G, Kuczynski K. The Practice of Hand Surgery in Restoration of Thumb. 2nd ed. Oxford: Blackwell Scientific Publications; 1989: 376-379
- 8 Shafer ES, Syrrington J, Bryce TH. Quain’s Elements of Anatomy in Mycology. 11th ed. New York, Toronto: Longman’s and Green and co; 1923: 142
- 9 Sabnis AS. Anatomical variations of long tendons of the thumb. Intl J Curr Res Rev 2013; 05 (07) 42-46
- 10 Esther Yamuna N, Dhanalakshmi V, Ganga NV. Study of variations in the extensor tendons of forearm and hand. Int J Anat Res 2017; 5 (04) 4504-4509
- 11 Abdel-Hamid GA, El-Beshbishy RA, Abdel Aal IH. Anatomical variations of the hand extensors. Folia Morphol (Warsz) 2013; 72 (03) 249-257
- 12 Ravi PK, Tewari J, Mishra PR, Tripathy SK, Nanda SN, Gantaguru A. Variations of extensor pollicis brevis tendon in Indian population: a cadaveric study and review of literature. J Clin Orthop Trauma 2019; 10 (02) 278-281
- 13 Roy AJ, Roy AN, De C. et al. A cadaveric study of the first dorsal compartment of the wrist and its content tendons: anatomical variations in the Indian population. J Hand Microsurg 2012; 4 (02) 55-59
- 14 Hollinshead WH. Anatomy for Surgeons. Vol. III. 3rd ed. PA, USA: Harper and Row Publishers; 1989: 423-426