1. Defective And Excessive Development

The former class includes those cases in which one, or more, or all of the extremities, or some part of one of them, is wanting, or in which their development is arrested. In the upper extremity it may happen that there is no humerus, or that one or both of the bones of the fore-arm are absent, or, if present, are in a rudimentary state. The hand will then be found articulated to the humerus, or to the scapula, according to the special deficiency of the intermediate bones. The hand itself may not exist at all, or only a part of it may be developed. In the case of partial deficiency of the hand, a correspondence is observed, both in the carpus, the metacarpus, and the fingers, with the character of the defective development in the fore-arm: when the radius is wanting, the thumb and forefinger, with so much of the carpus as belongs to them, are wanting too; and the other fingers, and their carpal elements, do not exist when there is no ulna; but when either bone of the fore-arm is in a rudimentary state some trace of the corresponding part of the hand, an incomplete finger, for instance, can also be found. Again, the hand may terminate at the metacarpus, or in one or more incompletely formed fingers; and, lastly, in some cases, a fusion of the bones of the metacarpus and fingers is observed.

Deficiencies of the same kind occur in the skeleton of the lower extremities. Only in them a peculiar fusion of the bones takes place, which is known by the name of the Siren monstrosity. The bones, in this case, are also rotated on their axes forward.

The chief instances of excess of development are those in which supernumerary fingers and toes, or the last phalanx of an additional finger or toe exist; they occur in persons who may be otherwise well formed. The development of additional long bones and limbs, whether complete or incomplete, indicates a tendency to duplication in the whole body.

2. Morbid Varieties In Point Of Size

Under this head may be included that disproportion in length affecting all the limbs, or the thoracic or abdominal extremities only, which dates from the period of their original formation; it is of most importance when it affects the bones of a single extremity or of one segment of an extremity. Thus the humerus or one of the bones of the fore-arm may be found shortened in a remarkable degree, and in the latter case some anomaly will exist in the articulation of the carpus, etc, to the fingers and toes: sometimes a bone exceeds its natural growth, and reaches a monstrous and disfiguring size.

A bone is liable to an interruption of its growth at any period, or it may be the seat of atrophy; in either case, the whole, or part, of an extremity, will present an instance of acquired smallness of size. Instances of this kind are frequently met with after exhaustive processes of disease and repair, either in bones or in the soft parts adjoining them, after inflammation and suppuration in them, fracture, caries, necrosis, and rickets, after unreduced dislocations, neuralgia, paralysis, etc.

3. Deviations Of Form

These are very numerous, independently of those which arise from defect or excess in the original formation of the bones. The bones are variously misshapen in dwarfs, in cases of hyperostosis, after the loss of the substance produced by caries, from osteoporosis, etc.; and their form is altered still more after fractures which have united with the fragments displaced, and after permanent dislocations; but the most remarkable deformities of all are the various bend-ings and curvatures of the long bones which are produced by rickets, etc, especially in the lower extremities.

4. Solutions Of Continuity

Every form of solution of continuity is exceedingly common in the bones of the extremities, but fracture is the most so. The whole subject has been considered in general already, and it only remains to treat in particular of fractures of the neck of the femur and of the patella.

Fractures of the neck of the femur are, for practical purposes, divided into those within the capsular ligament and those external to it. The former may occupy any spot intermediate between the head of the bone and the insertion of the capsular ligament. Its plane is sometimes transverse, but more commonly it is oblique: in the latter case, it either runs through the base of the neck near the insertion of the capsule, or, which is more frequent, passes somewhat further out and traverses the great trochanter.

Moreover, the two kinds of injury may be complicated together, the same fracture being partly within and partly without the capsule; and again, there may be one fracture within the capsule, and a different one external to it, running through the trochanters.

The diagnosis of these factures has for a long time engaged much of the attention of surgeons; but the fracture within the capsule has been the chief subject of investigation, with reference to the question of its reuniting by means of bony callus.

So rarely is this fracture reunited by bone, that many have doubted the fact; and on this account, as well as from the frequency of the accident, it is important to be acquainted with the changes which, in different cases, take place in the fragments.

It is often observed in very decrepit persons, that even after a long period no trace of inflammation and exudation is discoverable upon the fractured surfaces. The capsule is slightly reddened and swollen; but the only change in the surfaces of the fragments is, that they are smoothed off in a marked degree by absorption. There are some cases in which, though the fragments present no mark of reaction, they are absorbed to such an extent, that the head of the femur forms a flattened or concavo-convex disk, and its neck has almost entirely disappeared.

Sometimes partial necrosis takes place in the fragments, and the subsequent reaction degenerates into suppurative inflammation of the bone and articular capsule, and caries within the joint.

Usually the fragments, thus diminished more or less in size by absorption are covered with a fibroid (ligamentous) tissue. This covering is, in fact, callus, arrested in the progress of its development to bone, but in which now and then a few isolated splinters, or needle-like growths of new bone, do form. The fibroid tissue occasionally serves to bind the fragments closely together; but more commonly it is drawn out into ligamentous cords, which are inserted into the margins of the fractured surfaces and compose altogether a tolerably complete capsule: such a capsule connects the fragments but loosely together, and their surfaces are movable over one another. Or, again, there may be no ligamentous bands formed, and the surfaces of the fragments, unconnected with one another, but covered with the fibroid exudation, may articulate together within the old capsule. The false joint resulting has a freedom of motion proportioned to the quantity of the fragments which has been removed by absorption.