Anatomy and Function of the Thenar Muscles
Section snippets
Functional movements of the thumb
To fully appreciate the actions of the thenar muscles, the complex motions of the thumb must be understood. Thumb motion is facilitated through the coordination of intrinsic thenar and extrinsic musculature. The thumb musculature dynamically allows for precision pinching and power gripping. Because thumb stability is actively maintained by muscles rather than by articular constraints, most muscles attached to the thumb tend to be active during most thumb motions.3
The opposable thumb is
Anatomy
The most important functional determinant of a muscle is its architecture, the arrangement of muscle fibers relative to the axis of force generation.6 Muscle excursion is directly proportional to muscle fiber length. The force generated by a muscle is directly proportional to its cross-sectional area. Several investigators have studied the various physiologic properties of the thenar muscles and a summary of their findings is found in Table 2, Table 3, Table 4.6, 7
Despite their small size, the
Summary
The functional mobility of the thumb, especially in its action of opposition, is a uniquely human quality. The mobility, strength, and function of the thumb are greatly affected by the actions of the intrinsic muscles of the thumb. These highly specialized muscles, with their variable innervation patterns, help to make the human hand one of the true wonders of the natural world.
Acknowledgments
Special thanks to Dr Steven Green for his valuable insight.
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Cited by (36)
Palliative surgery for thumb involvement in ulnar paralysis
2022, Hand Surgery and RehabilitationCitation Excerpt :The FPB inserts on the lateral sesamoid bone of the MCP joint and the lateral tubercle at the base of the proximal phalanx. It also has an expansion to the EPL with the APB [1]. The superficial head acts in adduction and slight antepulsion.
Transferring the Motor Branch of the Opponens Pollicis to the Terminal Division of the Deep Branch of the Ulnar Nerve for Pinch Reconstruction
2019, Journal of Hand SurgeryCitation Excerpt :After harvesting the OPB, we observed no downgrade in thumb function according to the Kapandji score,18 possibly because the APB can compensate for paralysis of the OPB. These 2 muscles have the same function and fire at the same time during thumb opposition.34–36 It is also possible that, after we harvested its motor branch, the OPB remained innervated by intramuscular nerve interconnections with the motor branches of the APB and FPB, similar to what happens with the abductor digit quinti when its nerve is used for thenar muscle reinnervation.37
Intramuscular Tendon of the Adductor Pollicis and Underlying Capsule of the Metacarpophalangeal Joint: An Anatomical Study With Possible Implications for the Stener Lesion
2018, Journal of Hand SurgeryCitation Excerpt :Based on these observations, the occurrence of the Stener lesion in vivo might be related to the combined effects of the connection between the UCL and the AD musculotendinous structure and contraction of the AD. Previous anatomic research on the ulnar side of the thumb MCP joint has been limited to the UCL itself3,4 and the insertions of the AD.5–7 However, the layered relationship among musculotendinous structures of the AD, the UCL, and the MCP joint capsule, which is the deepest structure, has not been clarified.
The Dorsal Aponeurosis of the Thumb
2018, Journal of Hand SurgerySonographic Visualization of Thenar Motor Branch of the Median Nerve: A Cadaveric Validation Study
2017, PM and RCitation Excerpt :Postoperatively, US may also identify incomplete TCL transection, TCL regrowth, scarring and adhesions, and injury to the median nerve or its palmar cutaneous branch in patients with persistent, recurrent or new symptoms [5,17-21]. The thenar motor branch (TMB) of the median nerve (also referred to as the recurrent motor branch of the median nerve) is a critical structure within the carpal tunnel region because it supplies the primary motor innervation to the thenar muscles in most individuals [22-30]. As the median nerve courses through the carpal tunnel, it splits into radial and ulnar divisions (Figure 1A) [16,25,27,31,32].
The authors have nothing to disclose.