We usually place the patient supine in the operating table with the forearm across the chest, although the use of a radiolucent arm board or hand table can be also useful. Fluoroscopy enters parallel to the table from the feet. A small tourniquet is used as proximal as possible, making sure it will not interfere with the fixator frame; this is especially important in small persons. The field is prepared and draped, and the indicated repair-reconstruction procedure performed; the external fixation is generally the last steps of the whole surgery. In choosing the skin approach, it should be taken into account the lateral placement of the fixator and the necessity of identifying correctly the bony landmarks used for axis pin insertion (Fig. 27.2).

The tubercle present at the site of origin of the lateral collateral ligament, which represents the geometric center of curvature of the capitellum, is identified. Medially, the axis of rotation lies just anterior and inferior to the medial epicondyle; this corresponds to the center of curvature of the medial contour of the trochlea and is the locus of the humeral origin of the medial ulnar collateral ligament. If a medial exposure/cutaneous flap has been performed, the medial landmark is easily identified. When only a lateral approach is being used, the medial landmark can be palpated through the skin using the medial epicondyle as a reference that can be confirmed with the aid of a fluoroscope; a slight nonanatomic axis does not alter the elbow kinematics [11], so we usually do not perform a medial approach specifically for this purpose (Fig. 27.2) and have not had any complications on this regard.

Once the axis is located, the pointed tip of the axis target guide is placed on the medial side, with the cannulated stylus guide on the lateral side; the axis pin is then inserted through the guide in the distal humerus with a mallet or power tool.

The fixator frame is then placed on the axis pin with the distraction mechanism oriented distally; the proximal bar is aligned with the anterior humeral cortex.

The “absolute safe zone” (the inter-epicondylar distance proximal to the axis guide) demarcates the area of the humerus where the pins will be inserted. Before pin insertion, the skin should be positioned back anatomically where it will be sutured, and then a stab incision is performed for pin insertion. A 4 mm (3 mm in small bones) self-drilling self-taping pin is inserted proximally engaging both humeral cortices through the specific pin guide. A pin-rod coupling is placed and tightened with a wrench. A second pin is inserted distally using the same procedure including the pin guide, avoiding the olecranon fossa. Once both pins are rigidly coupled to the proximal rod, the axis pin can be removed.

Three millimeter self-taping self-drilling pins are used for the ulna. The technique is similar to that described for the humeral pins. We insert the proximal pin first and then the distal one, always with the aid of the pin guide. It can be difficult to “feel” the ulnar second cortex penetration, so we recommend checking with fluoroscope the correct position of the pins at the end of the procedure.