Calcaneus

“ Origin by a strong tendon from the medial sesamoid bone of the femur (Fig. 61, 4) and by muscle-fibres from the surface of the shaft for a short distance proximad of this.
The two heads unite by their contiguous borders at the junction of the first and second thirds of the tibia. The common muscle narrows rapidly and ends in a flat tendon which joins the tendon of the soleus to form the so-called tendon of Achilles (tendo calcaneus) (Fig. 90, t) . This has its
Insertion into the proximal end of the calcaneus (Fig. 90, 4) near its ventral border. ”

“ Dislocation of the talus from its articulations with the bones of the leg above and the calcaneus and navicular below, is a comparatively common injury, and results from a violent wrench of the foot. It may be incomplete or complete. When the foot is plantar flexed at the moment of injury, the displacement is generally forward with a tendency outward. The talus comes to rest on the third cuneiform and cuboid bones, the foot being abducted, inverted, and displaced medially. ”

“ Talipes Calcaneus is rare as a congenital deformity. It is usually the result of infantile paralysis of the muscles of the calf. The patient walks on the heel, and the anterior half of the foot is drawn up. Valgus or varus are associated with it; the more common form is talipes calcaneo-valgus.
Talipes Cavus (Pes Cavus) , or hollow foot, is a condition in which the arch of the foot is greatly exaggerated. It is rarely congenital but is frequently seen in connection with clubfoot, especially in its paralytic forms. In its mildest form, it exists in a highly arched foot, often hereditary. ”

“ Gunshot Wound of the Heel,
with Lodgment of the Missile.
That the inner border of the foot lay next to the plate is shown by the articulation between astragalus, scaphoid, internal cuneiform, and first metatarsal.
The metallic particles show the course of the ball from the posterior calcaneo-astragaloid ligament to below the anterior inferior border of the calcaneus.
As the shadow of the ball is enlarged and the shadow of the fragments blurred, their position is not near the plate and their location is therefore on the external plane of the calcaneus, with the ball lying near the sole. ”

“ Treatment should first be directed towards the equinus or calcaneus element of the deformity, for if these are corrected the cavus condition tends to disappear. Exercises and massage should be persevered with, and boots without heels should be worn. The contracted structures in the sole may require to be divided, either subcutaneously or by the open method, as a preliminary to forcible correction, and the hallucis tendon may be brought through the head of the first metatarsal. In aggravated cases the talus and the heads of the metatarsal bones may be excised. ”

“ In man the plantaris is inserted into the calcaneus along with the gastrocnemius.
Relations.—The muscle is covered throughout by the two heads of the gastrocnemius (Fig. 90, m; Fig. 91, k) , except at the proximal end (Fig. 90, l) , where it is in contact with the integument. Inner surface in relation with the popliteus (Fig. 92, k) , the soleus (Fig. 90, o) , the flexor longus digitorum (Fig. 91, n) , and flexor longus hallucis (Fig. 91, m) .
M. soleus (Fig. 90, o) .—A flat fusiform muscle lying beneath the plantaris. ”

“ In the backward variety, the plantar flexion is first increased and the foot is then strongly flexed in the opposite direction. In the forward type, forced dorsal flexion will effect reduction. The foot should be placed upon a posterior molded splint for three weeks, after which passive motions are begun. If the reduction is impossible, an arthrotomy with excision of the astragalus may be necessary.
Total Dislocation of the Astragalus. This form of dislocation is much more frequent than those of the ankle joint proper, or of the articulation between the astragalus, calcaneus, and scaphoid. ”

“ In falling down, the calcaneum is pushed backward making the long-heeled foot, while the bones forward of the astragalus must advance more or less in their direction, thus adding to the foot’s length at both ends, and making the leg appear to be set far toward the middle. The ends must necessarily be separated before the middle of the arch can sink, and this is why its flattening is accompanied by the long heel. ”

“ The ankle, or tarsus, consists of the same seven bones as in man, and these bones are so arranged, or bound together by ligaments, as to form a transverse and an antero-posterior arch. In no ape or monkey, however, do the lower ends of the inner metatarsals form the anterior point of support of the antero-posterior arch, as in man. The calcaneum, except in the gorilla, is shorter compared with the spine than in man. The phalanges of the foot are the same in number as in man, except that the great toe of the orang-utan has often but one. ”

“ This type of astragalus is altogether peculiar to the artiodactyls, all of which possess it; it is unlike that of any other mammal whatever and may be recognized [360] at a glance. The calcaneum, or heel-bone, has a large convex facet, by means of which it articulates with the fibula, or external leg-bone; there is no such articulation in the perissodactyls. The lower end of the calcaneum is narrow and fits into a step cut in the cuboid, which is thus every whit as peculiar and characteristic as the calcaneum and astragalus. ”

“ Large conical calcar on tibiotarsal articulation; ill defined, scattered tubercles on tarsus and along ventrolateral edge of foot; toes bearing discs slightly wider than long, smaller than those of fingers; relative length of toes Iwebbing formula of toes I2—23⁄4II13⁄4—3-III2-—3+IV3+—2-V. Skin on dorsum, head, and dorsal surfaces of limbs smooth ”

“ Little by little, but with much excelsior and twine, the muscles are gradually built up. Leave the bones bare at the points where nature does. The hind leg must have its tendon of Achilles before it can be finished. To make this, drill a hole through the end of the calcaneum, or heel bone; pass a long wire through for half its length, twist the two halves tightly together until they will reach half-way up the thigh, then wrap tow around the twisted wire from the heel bone up, making the tendon larger as you proceed. ”

“ Dr. Mayer considers that this spur or hook is a true nail, in the cavity of which is a semi-cartilaginous bone representing the last joint of a toe; this is jointed to a small bone representing the metatarsus, the little projection from the swollen joint above is the tarsus, and the slender bone above is the tibia or leg-bone, imbedded in the muscles, and terminated by a slender curved and pointed filament of cartilage jointed to it, which probably represents the evanescent rudiment of a femur or thigh-bone. ”

“ It is more difficult to trace the fate of these structures in existing vertebrates than it is with the carpal bones. In man the astragalus probably contains the tibiale, tibiale marginale and intermedium, the latter structure possibly accounting for the occasional os tri- gonum, already mentioned in the subsection on embryology. The fibulare and fibulare marginale probably form the calcaneum, though it is unlikely that the epiphysis at the back of that bone represents any integral part of a generalized tarsus. ”

“ The limbs are small in proportion to the size of the body, and are adapted for swimming or for shuffling along the ground; they are plantigrade and the bones are all solid. In living forms the anterior limbs have five digits and the posterior four, the fifth being represented only by a short metatarsal. The first three digits in each case are clawed. The calcaneum has a large backwardly-projecting process. ”

“ Hence any deviation from this line, one way or the other, indicates more or less dislocation of the tibia. There is a pellet of fat under the ligament, which answers a ‘packing’ purpose—sinking in when the knee is bent; rising when the knee is extended, and bulging on either side of the tendon, almost enough to give the feel of fluctuation.
In a well-formed leg the ligamentum patellæ, the tubercle [Pg 51] of the tibia, and the middle of the ankle should be in the same straight line. ”

“ The ligaments need no new invention on his part but only a more human degree of development, and in particular the calcaneo-navicular ligament and internal lateral of the ankle undergo in the human foot great development, and the long plantar ligament, originally part of the tendon of the gastrocnemius, comes in to the aid of the arch and goes to bind it together, so that these humbler structures follow in the wake of the changing and enlarging bones. ”

“ Ribs are very little developed. Clavicles are present. The ilia are very greatly elongated. The anterior limb has four well-developed digits and a vestigial pollex, and is of moderate length; the radius and ulna have fused. The posterior limb is greatly elongated and is pentedactylate; the tibia and fibula are fused, while the calcaneum and astragalus are greatly elongated, and it is largely owing to them that the length of the limb is so great. The group includes the Frogs and Toads, the predominant Amphibia of the present time. ”

“ Three metacarpals were picked up, all measuring about 7 inches long and 1 inch in breadth at the narrowest part of the shaft; and these are all adult specimens. Two adult metatarsals measure, the one 8 inches in length and the other only 7·3, while in breadth they both measure only ·9 of an inch. A complete adult radius measures only 9 inches in length. A lower end of a humerus is only 2·5 inches broad. Among six calcanea the largest measured 5·5 inches, and the shortest 4·3. In one specimen the orbit is 2·4 inches diameter, and in another 2·8 inches, which is decidedly large. ”

“ And yet that same cartilage, with the foot removed from the ground, is as pleasantly yielding to pressure of the thumb as the most exacting of us could wish for. In any case, then, where doubt exists, the foot should be lifted to the knee, and the cartilage carefully examined with the foot in that position. If, then, at any spot above the normal contour of the os pedis we meet with hardness or rigidity, we are to look upon that foot with suspicion. Nevertheless, providing our conscience is sufficiently elastic, the animal may be passed sound so far as the existence of a side-bone is concerned. ”

“ The ankles have to, and soon do, acquire an increased suppleness and strength, in claw practice.
Perhaps the most difficult task for the beginner is [Pg 290] to learn the art of walking and balancing upon flexed ankles, while traversing across steep faces. To strike all the points in neatly and strongly sideways, and with a flexed ankle, so that the flat of the sole may meet the surface cleanly and without a scrape, takes some practice; but slab climbers, who have suppled their ankles by foot-clinging upon steep rock angles, will find themselves a day or two’s frog-marching to the good on ice. ”

“ With regard to alteration in gait, we may say at once that side-bones in heavy animals are not often the cause of lameness. In fact, where the foot is well developed, when neither the foot as a whole nor the phalangeal bones give evidence of disease, and where the pasterns are fairly oblique and well formed, this alteration of the cartilages may be looked upon as of no serious import at all. Neither is the side-bone due to blows or other injuries likely to be productive of lameness—that is, always supposing, of course, that the foot in other respects is of good shape. ”

“ Symptomatology.—Ossification of the cartilages is known by grasping the free borders with the fingers and attempting their flexion; the rigid inflexible ossified cartilage is thus easily recognized.
Lameness during weight-bearing occurs in the majority of cases at some time. Much depends on the conformation of the foot and whether the involvement affects one or both cartilages as to the degree and duration of lameness which marks this affection. In narrow and contracted heels it is reasonable to expect more lameness than in well formed feet. ”