Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 24 On the Bones of the Forearm: the Ulna and Radius

Articulation of ulna to humerus: description of its depression and processes at this point

In the first place, they are attached to the lower end of the humerus by altogether different types of joint. 20 The ulna is articulated to the groove or trochlea (K, L, M of figs. 1 and 2, ch. 23) by depressions 21 carved to fit this purpose, and by suitable processes. On its upper end where it is quite thick and solid and like the lower end of the humerus has no epiphysis, 22 it has two conspicuous processes, one of which is prior or anterior to the other (the anterior is C [proc. coronoideus] the posterior D [olecranon] in figs. 1, 2, 5, 11). The anterior is the one that faces the depression (N in fig. 1, ch. 23) [fossa coronoidea] carved in the anterior surface of the humerus next to the upper region of the trochlea, and with its projections it exactly fits that depression. This process is wide,


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obtusely angled, quite hard, and solid. The posterior process more or less resembles the shape of the anterior, entering the depression (O in fig. 2, ch. 23) [fossa olecrani] that is seen carved out in the posterior area of the humerus next to the upper region of the trochlea; but since this depression is much deeper and wider than the anterior, the posterior process rightly turns out to be thicker and broader than the anterior, even more resembling an obtuse angle. The Athenians called this the w)lekra/nion, the Dorians ku/biton, Hippocrates a)gkw/n; Galen calls it sometimes w)lekra/nion, sometimes a)gkw/n. 23 These words are confused by translators, to the great inconvenience of those who read Latin; not only do they frequently translate them with the single word cubitus, they also apply the word to the ulna, to everything situated between the humerus and the wrist, to the joint of the humerus with the radius and ulna, to the inner area of this joint, and to the angle of the elbow, 24 though it makes a great difference what the author whom they are translating meant by each of these words. For this reason, to avoid making an already difficult subject more obscure, I earnestly beg the reader patiently to allow me always to use the same word throughout, and not to desire everything to be confused for the sake of some abundance 25 of language or obscure special jargon. We shall therefore call these processes of the ulna the anterior and the posterior, which many have called “the hump,” gibber, and “the lump,” gibbus, without considering that in their simplicity they have also named the tubercles of the humerus at the sides of the trochlea (P, S in figs. 1 and 2, ch. 23), 26 the lower heads of the femur (E, F in figs. 1 and 2, ch. 30), 27 and several other bony processes gibberi. 28 Between these processes of the ulna (C, D, then E in figs. 1, 2, 5) 29 in the region where they face each other, a great depression [incisura trochlearis] is carved out which receives the trochlea of the humerus, matching it in every way. First, it is hollowed like a semicircle or even a little deeper than a semicircle: it resembles our C or the C [lunate sigma] of the Greeks, whence the ancient Greeks called this sigmoeidh/j, sigmoid, from the shape of this character. This depression is not just casually shaped like a C, but in order for it to match the trochlea of the humerus exactly, it protrudes in the middle with a blunt, wide bulge (F, F in fig. 11) which runs lengthwise along this depression and is so pushed down and depressed at each side (G, G and H, H in the same fig.: cf. K, L, M in figs. 1 and 2, ch. 23) that it may be compared to the rope or line that is turned on the wheel of a pulley. For just as a smoothly rounded line is turned upon the smooth channel of the pulley’s wheel, fitting (so to speak) its concavity, so this protuberance in the hollow of the ulna fits the depression of the trochlea, and the depressed and hollowed sides of the protrusion in turn are matched by the rising sides of the trochlea’s groove. That this fit may be more precise, the inner side of the depression of the ulna is more deeply hollowed than the outside, evidently because the inner side of the trochlea juts out and protrudes much farther than the outer. This entire depression of the ulna is smooth and coated with cartilage, and with its processes is so fitted to the trochlea 30 that if you imagined it even to the slightest degree more protuberant, more deeply carved, increased, or reduced, you would at once have marred an entire joint that was skilfully constructed for the sole purpose of flexing and extending the forearm without risk of dislocation. In addition, that structure which is made by the mutual entry of bones is not only extremely pleasant to view, but it also complements the strength of the ligaments 31 binding the joint. To make strong ligaments surround the joint, 32 the surface of the processes not facing the depression (C and D in fig. 11) is rough and uneven — though the processes are rough not just for ligaments but also for muscles. The posterior surface of the posterior process 33 [olecranon] protrudes quite unevenly and is somewhat hollowed out so that it may more strongly receive the insertion of muscles [m. triceps brachii, m. anconeus] that extend the forearm (b, c, d in the 13th table of muscles). Likewise, the anterior part of the front process of the forearm [proc. coronoideus] is rough so that a more powerful insertion of the posterior of the muscles that flex the forearm (G in the 8th table of muscles) [m. brachialis] might be effected and the muscles that flex the second (Q in the 5th table of muscles) [m. flexor digitorum superficialis] and third (C in the 6th table of muscles) [m. flexor digitorum profundus] joints of the fingers might more readily take their origin thence. This anterior region of the front process is not the only one to be roughened: next to the root of this process, Nature equipped the ulna with some rough tubercles (L in figs. 5 and 11) [tuberositas ulnae] for the sake of these muscles. In addition, to have this joint surrounded with stronger ligaments, in the lowest part of the depression of the ulna that resembles the letter C there is seen a small depression on either side (I, K in fig. 11) pushed in like a kind of angle; and the C-shaped depression itself gives way there from its circumference and becomes rough, surely for no other purpose than that the origin of strong ligaments might be supported from this part of the ulna that is covered with small closed foramina [foramen nutriens].



Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them] | Chapter 24 On the Bones of the Forearm: the Ulna and Radius