This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
In amputation one has to deal with a part of the body that is approximately cylindrical in shape and that contains only a single bone entirely surrounded by soft parts. The circular method is more applicable to amputation of the arm below the insertion of the deltoid than to any other part of the body, but nevertheless in some cases, particularly in muscular arms, difficulty may be experienced in turning back the cuff. In such cases the cuff is slit by the surgeon and the operation becomes one of square skin flaps. For this reason flap amputations are usually to be preferred.
The arm may be amputated at any place, high up or low down. Artificial appliances for the upper extremity are comparatively useless; hence the height of division of the bone is determined by the injury.
As it is desirable to retain the head of the bone and tuberosities, if possible, in order to preserve the shape of the shoulder and retain the attachment of the muscles, amputation may be done through the surgical neck. This is just below the epiphyseal line. In performing a flap amputation the soft parts should cover or cap the bone like a hemisphere: therefore the total length of the flaps should be equal to one-half the circumference of a sphere whose diameter is the diameter of the limb at the point of section of the bone. If the diameter of the limb is 4 inches, then the total length of the flaps should be approximately 6 inches. If the flaps were of equal length then each would be 3 inches long. If there was only one flap, it would be 6 inches long.
It is an axiom in surgery that in flap amputations the artery should be contained in the shorter flap. The operator should accurately know the course of the artery and avoid making his flaps in such a manner as to bring the vessel in the angle of the wound. Otherwise the artery is liable to be split. In a high amputation the external flap may be long and the internal short. In the middle of the arm anteroposterior flaps are preferred and the artery is included in the posterior flap. If the amputation is in the lower third and the flaps are anteroposterior, then the artery of necessity is in the anterior flap.
Above the middle of the arm the deltoid, coracobrachialis, and biceps muscles are free and therefore retract markedly when cut. In the middle the biceps only is free and the same is the case in the lower third. The triceps and brachialis anticus are attached to the bone and therefore retract but little when cut. Surgeons have called attention to the necessity of being careful to see that the radial (musculospiral) nerve is properly divided, otherwise it may be torn by the saw. The groove in which it lies may be unusually deep and necessitate a special effort to divide it. On the face of the stump the artery is to be looked for to the inner side of the bone in the upper two-thirds of the arm and anteriorly in the lower third. Lying on it will be the median nerve and to its inner side the ulnar nerve. At the level of the insertion of the deltoid the radial (musculospiral) nerve, accompanied by the (superior) profunda artery, will be posterior or toward the outer side. The superior ulnar collateral (inferior profunda) artery is given off at the level of the insertion of the coracobrachialis muscle, which is about opposite the insertion of the deltoid. It accompanies the ulnar nerve. A nerve may be seen lying between the biceps and brachialis anticus. It is the musculocutaneous which becomes superficial just above the bend of the elbow (Fig. 288).
Fig. 288. - Amputation just above the middle of the arm.
Five cm. (2 in.) above the elbow the inferior ulnar collateral (anastomotica magna) artery may be expected to be encountered passing down and in over the brachialis anticus muscle.