(C) FRACTURES OF THE LOWER END OF THE HUMERUS (ELBOW) These are of great importance in children and occur in about 20 per cent. of all fractures.
The numerous epiphyseal lines cause the structure of the newly formed bone to he more porous in this locality, and therefore more ex posed to dislocation and separation, because the periosteum which other wise protects the cartilaginous epiphyses is lacking inside the joint.
The variations of fractures which we observe in this locality are very numerous, depending upon the mechanism of the fracture and upon the strength of the ligaments, which latter are better able to withstand the attacking force than the bone and therefore lead to a tearing out of their insertions.
The different positions of the arm, as, for instance, in falling, and the varying stages of ossification form another differentiating factor.
Fractura Supracondylica This is more frequent in older children, who are exposed to more severe injuries, and in whom the different parts of the end of the humerus are better united. The most frequent cause is a fall from a considerable height upon the hand with the elbow extended (Figs. 155a, 155h, Plate 15). In adults and older children the same injury will cause a backward luxation of the forearm in the elbow-joint. In children with flexible bones this fracture takes its place. The bone usually breaks obliquely, more rarely transversely, the upper fragment is forced against the skin and perforates it if the force causing the injury is considerable. The lower fragment is dislocated upward and backward by the traction of the triceps. In some rare cases of falls upon the flexed elbow the upper end may be dislocated backward, when the line of fracture has the opposite direction.
Examination may be quite difficult when there is muck swelling and hemorrhage, especially so because in small eldhlren we cannot count upon subjective symptoms. Usually the oleeranon appears to be dis located upward and backward, but its point is found in a straight line with both epicondyles the same as it is normally, while in 'taxation it is found considerably above this line. Attempts at motion show abnormal] motility (even sideways) of the broken-off lower end of the humerus. If we have no X-ray apparatus handy we will have to use
light narcosis with ether in unruly children. In small children we will usually observe an intra-articular fracture (Figs. 156, 157, 15S, Plate 1G).
Of these the most frequent are: (a) Separation of the External Condyle and Epicondyle In falling upon the palm of the hand and with the force acting somewhat obliquely, the impetus of the radius may tear off the external condyle. Kirmisson explains the frequency of this by the broad surface which this bone offers, and also by the delayed ossification of the external condyle compared with the internal one. The torn-off piece of bone is still hanging by the intact periosteum, appears higher, and is twisted around in some cases and may be dislocated in any direction.
Should the epieondyle also be affected and the lateral ligament be torn off, then this fracture may be combined with a sideways dislocation of the joint.
The fracture may also extend into the trochlea, tearing this off, thus causing a picture similar to that found in the higher, supracondylar fractures (transverse intra-articular fracture) (Figs. 157, 15S, Plate 16) or separation of the condyles only (T-fraeture). In still other variations the part of the joint formed by the bones of the. forearm may also be destroyed.
In some rare cases of direct injury, such as a fall upon the internal condyle, it may be broken off alone or with the trochlea; but these eases as well as fractures of the olecranon and of the head of the radius are much rarer in children.
The diagnosis in these cases is quite difficult, especially without ski agraphy. Painful motion in the elbow-joint is common to all these frac tures. The joint is always swollen, and filled with blood except in the extra-articular avulsions. Motion in the joint is painful and limited (ab normal motility, occasional interposition of the separated piece of bone, crepitation). Should either complete or incomplete dislocations be joined to these fractures, then the deformity will be still more pronounced.