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Limb anatomy and medical imaging 

Limb anatomy and medical imaging
Chapter:
Limb anatomy and medical imaging
Source:
Oxford Textbook of Rheumatology (4 ed.)
Author(s):

Mike Benjamin

, Dennis McGonagle

, Maribel I. Miguel

, David A. Bong

, and Ingrid Möller

DOI:
10.1093/med/9780199642489.003.0065_update_001
Previous versions of this chapter are available. To view earlier versions of this chapter view the full site here.

This chapter provides a generalized framework for helping the clinician to understand basic principles of functional anatomy in the limbs in relation to medical imaging, particularly ultrasonography (US). Certain basic design principles that are evident in the limbs are explained: for example, that larger muscles lie proximally, and that tendons are more numerous and longer distally. While the upper limb is ultimately geared to moving the hand with ease and precision in three-dimensional space, the lower limb is both an organ of propulsion and a column supporting body weight. It is important to note that when the foot is on the ground this has an important influence on muscle function. Fundamental principles of muscle design and action are explained, including the distinction between prime movers, antagonists, synergists, and fixators; the fact that movements and not muscles are represented in the cerebral cortex; the all-or-nothing principle of fibre contraction; the modifying influence of gravity on muscle action; and issues relating to fibre architecture. The less appreciated functions of tendons are included and the difference between an enthesis and an enthesis organ is explained. The similar appearance of nerves and tendons in dissections and even in MRI and US images is explained and the importance of fascia is highlighted—particularly its role as an ’ectoskeleton’. Brief mention is made of adipose tissue and blood vessels, and planes of movement between adjacent structures are described in order to inform the ultrasonographer who deals with structures in real time.

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