It will be necessary to move the arm about, and it should at first lie on its posterior, and next on its anterior surface.
1. A circular one around the arm two inches above the Condyles of the Humerus.
2. A circular, one around the forearm, two inches below the same points.
3. A longitudinal one along the median line in front, between the two circular incisions. Reflect and remove the included portion of skin, and expose the superficial fascia containing— In Front—
1. The Cutaneous veins. The Radial, on the outer side.
The Anterior and Posterior Ulnar, the latter coming from the posterior surface of the forearm, and the two uniting into one trunk. The Median, along the centre of the forearm, dividing into two branches, Median-cephalic externally and Median-basilic internally, and receiving at its bifurcation a deep vein from the venæ comites of the Brachial artery. The Radial vein joins the Median-cephalic, and the two form the Cephalic vein which runs up on the outer side of the arm. The united trunk of the Ulnar veins joins the Median-basilic, and the result is the Basilic vein passing upwards on the inner side of the arm.
2. With the Cephalic vein is the superior External Cutaneous branch of the Musculo-spiral nerve.
3. Behind the Median-cephalic vein the External Cutaneous nerve running down to the forearm.
4. The Internal Cutaneous nerve at the inner side of the arm dividing into numerous branches. One of these passes to the back of the forearm over the internal Condyle; the others pass some superficial to, and some beneath the Median-basilic vein, to the front of the forearm.
5. Cutaneous branches of the Radial Recurrent artery are found in front of the outer Condyle.
6. Lymphatics, and a gland in front of the elbow, and one above the inner Condyle. Behind will be found—
7. The Olecranon process covered by a bursa.
8. The nerve of Wrisberg between the internal Condyle and Olecranon, sending filaments inwards over the lower part of the arm, the inner Condyle, and the Olecranon. A communication may be traced with the Internal Cutaneous nerve.
9. The inferior External Cutaneous branch of the Musculo-spiral nerve giving twigs over the posterior surface of the arm and forearm. 10. Cutaneous twigs of the following arteries are seen: of the Interosseous Recurrent behind the outer Condyle ; of the Posterior Ulnar Recurrent and Inferior Profunda behind the inner Condyle.
Remove and expose the fascia lata which dips down to the external and internal Condyloid ridges to form the corresponding intermuscular septa, and is joined in front by the semilunar process of fascia derived from the tendon of the Biceps muscle.
Remove the preceding except the septa, and there will be now exposed—
1. The Supinator longus and Extensor carpi radialis longior muscles running down from the external Condyloid ridge.
2. The Brachialis anticus muscle and the lower part of the fleshy belly and tendon of the Biceps muscle in the centre, superficial to the preceding. These pass from the arm, the former to the Coronoid process of the Ulna, the latter to the Tuberosity of the Radius.
3. The origin of the Pronator radii teres muscle from the internal Condyloid ridge, and the common tendon of the Pronator radii teres, Palmaris longus, Flexor sublimis digitorum, and Flexor carpi ulnaris muscles from the internal Condyle.
4. A small piece of the Supinator brevis muscle in the floor of the triangular space. Behind—
5. The tendon of the Triceps muscle inserted into the Olecranon process.
6. The Anconeus muscle passing from the outer Condyle to the outer surface of the Olecranon process.
7. The common tendon of the following muscles from the external Condyle: Extensor carpi radialis brevior, Extensor communis digitorum, Extensor minimi digiti, Extensor carpi ulnaris. The origin of the Supinator brevis muscle from the same bony point.
8. The origin of the Flexor carpi ulnaris muscle from the inner surface of the Olecranon process, and the posterior margin of the Ulna.
9. The external and internal intermuscular septa. In Front—
10. A further portion of the External Cutaneous nerve, emerging on the outer side between the Biceps and Brachialis anticus muscles.
11. The Musculo-spiral nerve lying deeply between the Supinator longus and Brachialis anticus muscles, and dividing on a level with the external Condyle into Radial and Posterior Interosseous branches. Offsets from the trunk are traceable to the Supinator longus and Extensor carpi radialis longior muscles, and occasionally one supplying the Brachialis anticus muscle. With the nerve a branch of the Superior Profunda artery is seen.
12. The Brachial artery with its venae comites is seen internal to the Biceps tendon dividing opposite the head of the Radius into Radial and Ulnar branches. The Anastomotica Magna branch is found above the elbow, sending a small branch down beneath the Pronator radii teres muscle, and perforating the internal intermuscular septum.
13. The Median nerve lies internal to the Brachial artery, and gives off a branch above the elbow to the Pronator radii teres muscle. Behind—
14. The Anastomotica Magna and Inferior Profunda arteries are found in the space between the internal Condyle and Olecranon process.
15. The Ulnar nerve with the preceding.
Divide now— a. The origin of the Pronator radii teres muscle from the internal Condyloid ridge, and its inner tendinous head (which overlaps the Anterior Ulnar Recurrent artery) from the inner surface of the Coronoid process.
b. The common Flexor tendon from the internal Condyle.
c. The outer head of the Flexor carpi ulnaris muscle from the Olecranon process and posterior border of the Ulna. Turn all the preceding muscles downwards.
d. Detach the Supinator longus, and Extensor carpi radialis longior muscles from the external Condyloid ridge and pull them down.
e. Remove the Anconeus muscle.
f. Take away the Triceps muscle. Do this piecemeal, dissecting out in its substance the Superior Profunda artery. A branch will be found running to the back of the external Condyle between the muscle and the bone, and an arch across the back of the bone immediately above the Olecranon fossa to the inner side, joining with the Anastomotica Magna artery.
There will now be exposed—
In Front of the outer Condyle—
The Radial Recurrent artery, joining with the anterior branch of the Superior Profunda.
Behind the outer Condyle—
The Interosseous Recurrent artery anastomosing with the posterior branch of the Superior Profunda, and a branch from the Anastomotica Magna coming from the inner side. It sends a branch over the Olecranon to join the Posterior Ulnar Recurrent artery.
In Front of the internal Condyle—
A slender branch from the Anastomotica Magna artery, uniting with the Anterior Recurrent branch of the Ulnar artery.
Behind the internal Condyle—
The general anastomosis of the Superior and Inferior Profunda and Anastomotica branches of the Brachial artery with one another, and with the Posterior Recurrent branch of the Ulnar artery running up from the forearm.