ELBOW-JOINT, ABNORMAL CON DITION OF.—Placed in the middle of the long lever which the upper. extremity repre sents, the elbow-joint is of necessity exposed to numerous accidents, the most remarkable of which are fractures and luxations. These, re duced or unreduced, produce immediate and remote effects, to which it is our business in this place to advert. Congenital malforma tions sometimes, though very rarely, are to be met with affecting this articulation, and require some brief consideration.
The several structures too, which enter into the composition of the elbow-joint, are each and all occasionally affected by acute and chronic inflammations, the consequences of which we cannot omit to notice, and many of these have their reputed source either in struma or syphilis, while others are attributed to an ar thritic or to a rheumatic diathesis.
1. Accident.— Fractures.—Fractures of the bones of the elbow-joint may be classed as to their situation and direction : first, as they affect the lower extremity of the humerus ; and, secondly, as they engage the upper extremities of the bones of the fore-arm.
1. Simple fractures of the humerus near the elbow-joint may be transverse or oblique. When this hone is fractured transversely at its lower part immediately above its condyles, or in young subjects through its lower epiphysis, in either case the olecranon process is pulled backwards and upwards by the triceps, while the part of the humerus superior to the fracture, that is, almost the whole of the bone, is carried forwards, and forms such a projection below as much resembles a luxation forwards of the true articular extremity of the bone ; the prominence in front is also considerably increased by the in clination forwards of the upper extremity of the lower short fragment, which is pulled in this direction by the supinators and pronators taking their fixed point below. The prominence for wards, furlied by the angle of contact between the upper and lower fragments of the humerus, is covered in front by the brachialis anticus and biceps; and there is a projection behind formed by the olecranon process equally well marked ; so that, in comparing the posterior aspects of the two articulations, we see the ole cranon process at the affected side exceed by its projection backwards that of the uninjured arm an inch or more : when to all this we add the observation that the antero-posterior diameter of the arm is evidently augmented, we have here many of the signs which might lead one to sus pect the existence of the luxation of the bones of the fore-arm backwards. There is this differ ence however, namely, that in fracture a crepitus can be felt, and the deformity is not accompa nied with any changes of the normal relations existing between the olecranon and the con dyles.
Oblique fractures near the elbow-joint are usually prolonged into the articulation, and may be either external or internal. The frac ture may traverse in an oblique line from without inwards, and from above downwards; and then the external condyle and capitulum of the humerus will be detached from the shaft of that bone, and will constitute the external or inferior fragment ; or the fracture may take place obliquely from above downwards, and from within outwards, so as to comprehend the trochlea of the humerus and internal con dyle in the inner fragment. In the first case, or external fracture, the posterior muscles of the fore-arm will have a tendency to pull the condyle downwards and backwards ; and in the second, the internal fragment with the trochlea will be drawn downwards and for wards by the pronator muscles.
Oblique fractures, extending into the elbow joint, detaching the external condyle of the os humeri, maybe detected by the following sym ptoms. There is considerable swelling and pain upon pressure on the external condyle and the motions of the elbow-joint, both of ex tension and flexion, are performed with pain; but the principal diagnostic sign is the crepitus produced by communicating a rotatory motion to the fore-arm. If the portion of the frac tured condyle be large, it is drawn a little backwards, and it carries the radius with it ; but if the portion be small, this circumstance does not occur ; if the fracture of the external condyle take place immediately above it and within the synovial sac, it is stated by Sir A. Cooper that no union will take place except by means of ligament.* The oblique fracture of the external condyle is frequently met with in children ; a fill on the hand forwards may cause it, the impulse being transmitted along the radius to the capitulum and outer condyle of the humerus. The connexion of the radius with the ulna at this period of life is so loose that no resistance is afforded to the forcible ascent of the radius when a sudden fall for wards on the palm of the hand occurs ; and hence in the young subject particularly an oblique fracture of the outer condyle of the humerus can readily happen : at a late period of life, the connexions between the bones of the fore-arm are so strong and unyielding, that from a similar fall forwards on the hand, it is the lower extremity of the radius which would be obliquely fractured.