DISTURBANCES OF GROWTH IN THE UPPER EXTREMITY Mechanism of Development.—The yielding of the soft bone to the muscular traction is the chief cause of the deformity, while a lesser influence may be due to the weight (in creeping) or the adaption of the bones to the lateral contours of the body.
Biology teaches us that the upper extremity in order to change from a dorso-ventral fin to a grasping organ must undergo philogenctically a number of rotations, eircumductions, and torsions. This fact, together with the observations of Iloll that such rotations also take place during embryonal life, offers a suita He explanation of the postfetal, co•kscrew like distortions which the humerus and forearm of a softened upper extremity present. This condition arises mainly from traction of the dominating group of muscles (grasping motion). (Biological prevalence of the pronator and flexor muscles.) As a rule the deformities follow the already existing physiologic curvatures and torsions.
Marked cases necessitate surgical intervention (osteotomy), to which, however, recourse should not be had until full recovery from the disease, because of the danger of a repetition of the deformity. The weak bony tissue is very frequently exposed to fractures which usually result in deformities (see Spontaneous fractures).
Two deformities arc occasionally noticeable at the elbow and are called cubitus valgus and cubitus virus.
Cubites yelps is the term for an outward deviation of the forearm (with radius and ulna parallel).
Cubites cares is the opposite deformity. Cuhitus valgus is to a cer tain degree a physiological feature and, in general, is the result of adop tion of the arm to the broader pelvis (Heubschcr). Abnormal softness of the bones would naturally change such normal conditions to patho logic disturbances. But on the other hand, distortions at the lower part
of the diaphysis of the humerus, as well as fractures in this region, may create similar deformities.
The rather frequent occurrence of overextension in the elbow-joint is certainly to be connected with the abnormal laxity of the articular ligaments. Such children present, furthermore, an abnormal laxity of other joints, voluntary dislocation of the metacarpo-phalangeal joint, voluntary dislocations of the fingers, and flexibility of the ankle. Thera peutic intervention is hardly called for in such cosmetic defects.
It must be noted that children should be taught not to increase the flexibility of joints either intentionally or in a playful mood (cracking fingers) .
Madelung's deformity of the hand consists in a curvature of the lower end of the radius towards the thumb, producing an apparent volar deviation of the hand. Heredity seems to play an important part (Eisto•). De Witt-Stetten reports a case of opposite deformity with dorsal devia tion of the hand (hirmisson).
Occasionally we come across habitual or voluntary dislocations of the metacarpo-phalangeal joint of the thumb which may attain to such a degree that surgical intervention becomes necessary. In cases where laxity of ligaments is combined with a slipping of the tendons of the extensors, marked disturbances in important muscular action of the thumb are elicited (inability to extend and abduct the thumb). Capsular folding and replacing of the dislocated tendons relieve these symptoms.
Dislocation of the tendons of the extensors occurs occasionally in other fingers and necessitates similar operations.