Plaster of Paris is constantly being used in the treatment of affections of joints and ligaments. I merely remind my readers of the above-mentioned method of stretching shortened muscles by fixing the affected joint in its extreme position in plaster of Paris, which is renewed when the shortened muscles have had time to be stretched by their own tonus, of Sayre's jacket in the treatment of scoliosis, of the value of fixation in plaster of Paris in assuring a normal position after fracture, of the necessity, for this reason, e.g., with fracture of the fibula, of making the patient continue to wear this plaster when he is once able to use his foot. In all these cases plaster of Paris is of great importance, and its proper application requires a certain amount of skill.
Lastly, I must mention the "portable apparatus" often used both for the upper and lower extremities, which have this in common, that they consist of two metal splints placed along the extremity, which are held in position by leather straps and are jointed at the required places. These appliances, which in many respects differ widely, serve various purposes. Their use makes it possible to keep the weight of the body from the joints of the lower extremity (which is often necessary with children after tubercular arthritis), when the splints must, of course, extend from under the feet (where they are fastened to a laced boot) to the pelvis, which they support by means of various contrivances. In other cases an apparatus of this sort may be used to limit movements, e.g., in flail joints, after inflammation, or after certain fractures (see Patella Fracture). It is then provided with simple mechanical arrangements suitable to the case. One can also, with the help of these appliances, stretch shortened muscles and other soft parts, either by screw power or by elastic power. In the latter case it is best to use solid rubber tubing in varying numbers of layers, more or less tightly applied, which is placed between hooks at suitable places for the purpose of attachment. [A solid rubber tube of this sort which has done good service happens to be in front of me now, and measures 6 mm. in diameter.] The same varied contrivances applied to the lower extremity, and provided with the necessary levers, enable the patient to give himself passive movements at the foot and knee with the help of a pair of ropes. Lastly, they are used when one wishes to compensate for paralysed muscles or muscle groups and improve mobility by so-called artificial muscles (i.e., by means of the elastic tubing above mentioned). For example, when an extensor group is paralysed it is compensated for as far as possible by the constant action of an artificial muscle of this sort, which extends when the antagonistic flexors are not active and provides the necessary condition for their mechanical work. It is the duty of the doctor to see that the appliances fit the patient properly, and that, as far as possible, they do not hamper the circulation nor press on the muscles, and that the elastic, if any is present, is of the right strength. Even skilful instrument makers are apt to err in this respect for obvious reasons, the elastic generally being much too weak. The manufacture of orthopaedic appliances has made enormous progress of late years, especially in Hessing's ambulatory splints, which fulfil the necessary requirements better than any earlier apparatus.