High resolution magnetic resonance imaging application in anatomy: the extensor digitorum muscle insertion on the first phalanx.

Classical dissection may give unsatisfactory results because of the presence of artifacts due to both the embalming process and displacement of the anatomical structures. This spatial disturbance could explain the divergent descriptions found in the literature about the presence, or the absence, of an insertion of the extensor digitorum muscle (ED) at the first phalanx (P1). Preliminary experiments by Van Sint Jan et al. (1996) found the same contradiction: dissections did not show a real tendon attachment, whereas a functional experiment seemed to show that "something" should exist between ED and P1 to explain the results. This paper presents the results of an in vitro MRI study of this anatomical area. A 7-T NMR microscope was used to collect accurate, noninvasive data. Subsequently, surface rendering was performed to visualize the structures in a three-dimensional manner. The results of this MRI study, together with functional data obtained in an earlier study, showed that no real insertion of ED on P1 exists. However, some collagenic fibers were occasionally-observed running from the ventral aspect of ED to both P1 and the metacarpo-phalangeal joint capsule. Those few collagenic fibers would play a secondary role in the extension of P1.