Landmarks Medical and Surgical

by Luther Holden; James Shuter

Thyroid cartilage.—The projection and depth of the notch in the thyroid cartilage, or ‘pomum Adami,’ varies in different persons. Between the notch and the hyoid bone there is a large bursa, which facilitates the play of the cartilage beneath the bone in deglutition. The notch does not appear till puberty, and is throughout life much less distinct in the female than the male. The finger can trace the upper borders and cornua of the thyroid cartilage: its lower cornua can be felt by the side of the cricoid.

On each side of the thyroid cartilage we can recognise the lateral lobes of the thyroid gland. On the upper and front part of the gland we can distinctly feel the pulsation of the superior thyroid artery. This pulsation, coupled with the fact that the gland rises and falls with the larynx in deglutition, gives the best means of distinguishing a bronchocele from other tumours resembling it.

Below the angle of the thyroid cartilage we feel the interval between it and the cricoid, which is occupied by the cricothyroid membrane. In laryngotomy we cut through this membrane transversely close to the upper edge of the cricoid cartilage, in order that the incision may be as far as possible from the attachment of the vocal cords.

25. Cricoid cartilage.—The projection of the cricoid cartilage is a point of great interest to the surgeon, because it is his chief guide in opening the air-passages, and can always be felt even in infants, however young or fat. It corresponds to the interval between the fifth and sixth cervical vertebræ. The commencement of the œsophagus lies behind it: here, therefore, a foreign substance too large to be swallowed would probably lodge, and might be felt externally.

Again, a transverse line drawn from the cricoid cartilage horizontally across the neck would pass over the spot where the omo-hyoid crosses the common carotid. Just above this spot is the most convenient place for tying the artery.

26. Those who have not directed their attention to the subject are hardly aware what a little distance there is between the cricoid cartilage and the upper part of the sternum. In a person of the average height sitting with the neck in an easy position, the distance is barely one inch and a half. When the neck is well stretched, about three-quarters of an inch more is gained. Thus, we have (generally) not more than seven or eight rings of the trachea above the sternum. None of these rings can be felt externally. The second, third, and fourth are covered by the isthmus of the thyroid gland. The trachea, it should be remembered, recedes from the surface more and more as it descends, so that, just above the sternum in a short fat-necked adult, the front of the trachea would be quite one inch and a half from the skin.

27. Trachea.—In the dead subject nothing is more easy than to open the trachea: in the living, this operation may be attended with the greatest difficulties. In urgent dyspnœa you must expect to find the patient with his head bent forward, and the chin dropped, so as to relax as much as possible the parts. On raising his head, a paroxysm of dyspnœa is almost sure to come on, threatening instant suffocation. The elevator and depressor muscles draw the trachea and larynx up and down with a rapidity and a force which may bring the cricoid cartilage within half an inch of the sternum. The great thyroid veins which descend in front of the trachea are sure to be distended. There may be a middle thyroid artery. In children the lobes of the thymus may extend up in front of the trachea, and the left vena innominata may cross it unusually high. Thus the air-tube may be covered by important parts which ought not to be cut. Considering all these possible complications, the least difficult and the best mode of proceeding is to open the trachea just below the cricoid cartilage; and if more room be requisite, to pull down the isthmus of the thyroid gland, or in children to divide the cricoid itself. It is important that all the incisions be made strictly in the middle line, the ‘line of safety.’

28. Sterno-mastoid muscle.—The sterno-mastoid muscle is the great surgical landmark of the neck. It stands out in bold relief when the head turns towards the opposite shoulder. Its inner border overlaps the common carotid, which can be easily compressed for a short time against the spine about the level of the cricoid cartilage. The artery extends (generally) as high as the upper border of the thyroid cartilage and corresponds with a line drawn from the sterno-clavicular joint to midway between the angle of the jaw and the mastoid process.

Between the sternal origins of the sterno-mastoid is the fossa above the sternum, more or less perceptible in different necks. As it heaves and sinks alternately, especially in distressed breathing, it was called by the old anatomists ‘fonticulus gutturis.’ In beautiful necks, as seen in the ‘Venus,’ it is filled up by fat.

Notice the interval between the sternal and clavicular origins of the sterno-mastoid. A knife introduced a very little way into this interval would wound, slanting inwards, the common carotid, slanting outwards, the internal jugular vein. These facts are of importance in performing the subcutaneous section of the tendon of this muscle.