The majority of humeral shaft fractures treated with ORIF use an anterolateral or posterior plating and the principles of absolute stability where severe comminution or bone loss is not present. Bridge plating incorporating the principles of relative stability may be required in the presence of significant bone loss or severe comminution. Fixation is achieved with 3.5- or 4.5-mm compression plates incorporating 6 to 8 cortices above and below the fracture, where space permits. Absolute stability is preferred in simple patterns. Transverse fractures are reduced and compression applied to the fracture site through the plating technique. Spiral oblique fractures can be compressed with lag screws perpendicular to the fracture plane with additional compression provided through the plating technique. Comminuted fractures that demonstrate large butterfly fragments may also be reduced and compressed with lag screws prior to compression plating.

The anterolateral approach to the humerus can be utilized for the majority of these fractures. This surgical approach is comprised of a distal extension of the deltopectoral interval.
Most fractures can be treated using the midportion of the incision without requiring a proximal extension to the deltopectoral interval. The skin is divided sharply over the biceps, centered on the fracture site. The cephalic vein must be identified and mobilized to avoid injury. The fascia overlying the biceps is then divided in line with the skin incision to reveal the interval between the biceps (musculocutaneous nerve) and the brachialis (dual innervation) muscles. The biceps is then mobilized, typically in the medial direction. Care must be taken to avoid injury to the lateral antebrachial cutaneous nerve if the incision is carried distally within 5 cm of the antecubital fossa. The brachialis may then be divided longitudinally in its midline, as this muscle receives dual innervation (medially from the musculocutaneous nerve and laterally from the radial nerve). Reduction is obtained and anterolateral or lateral compression plating stabilizes the fracture.

Structures at risk during this approach include the cephalic vein, the lateral antebrachial cutaneous nerve and the radial nerve. The cephalic vein is generally easily visualized in the anterior subcutaneous tissue immediately after skin incision has been made. Blunt dissection will allow for mobilization and subsequent protection of the vascular structure during the remainder of the case. The radial nerve lies in the spiral groove of the posterior humerus in the middle third and courses laterally to pierce the lateral intermuscular septum approximately 10 cm from the radiocapitellar joint. Care must be taken to avoid overpenetration of drill bits and screws in the location of the spiral groove to avoid iatrogenic radial nerve injury during fixation. In the distal portion of the incision, the radial nerve may be identified laterally between the brachialis and brachioradialis muscles.

If a proximal extension must be utilized in order to provide fixation in the proximal third of the humerus, the deltopectoral interval may be utilized. The internervous plane between the deltoid (axillary nerve) and the pectoralis major (medial and lateral pectoral nerves) is utilized. Care must be taken in the deep dissection to incise the periosteum of the humeral shaft lateral to the long head biceps tendon and the pectoralis major insertion. A small portion of the anterior insertion of the deltoid may be sharply reflected, if necessary. Excessive retraction on the deltoid must be avoided to prevent traction injury of the axillary nerve. When proximal plate fixation extends to or past the level of the bicipital groove, the anterior humeral circumflex artery must be identified and ligated.

Occasionally, a direct lateral approach may be utilized for fixation of humeral shaft fractures in the distal third or if the radial nerve warrants direct exploration and visualization due to potential injury. Skin incision is centered over the lateral supracondylar ridge on the lateral portion of the arm. Deep dissection takes place between the brachioradialis anteriorly and the triceps posteriorly. Proximally, the radial nerve is encountered as it courses from posterior to anterolateral at the lateral intermuscular septum approximately 10 cm from the radiocapitellar joint. The nerve may be explored in a posterior and proximal direction as it approaches the spiral groove and distally in a lateral direction as it travels between the brachioradialis and brachialis muscles. If the incision must be carried distally, the interval between the anconeus muscle (radial nerve) and extensor carpi ulnaris is utilized.

A posterior approach to the humeral shaft may be required for distal third fractures or fractures extending into the metadiaphysis of the distal humerus (so-called Holstein-Lewis fractures). There is no internervous plane for this approach, as it utilizes muscle-splitting of the triceps or medial and lateral windows between the triceps and the respective intermuscular septa. A skin incision is centered posteriorly over the triceps muscle and tendon from 8 cm distal to the acromion to the tip of the olecranon. The spiral groove of the humerus lies in the middle third of the bone and will typically be located 14 to 15 cm from the lateral epicondyle. A sterile tourniquet is usually required to facilitate a surgical field conducive to identifying the radial nerve and profundi brachii vessels in the spiral groove. The incision is carried down sharply through skin and the fascia overlying the triceps. Proximally, the fascia between the long and lateral head of the triceps is divided and the long head is retracted medially while the lateral head is retracted laterally. Distally, the fibers of the triceps muscle and tendon can be split longitudinally in line with the incision. The radial nerve and profundi brachii vessels must be located in the spiral groove and traced distally and proximally to allow for protection during the case. Fixation is accomplished using a long posterior or posterolateral plate. As before, absolute stability is preferred using compression through the plate in combination with lag screws, where necessary. If absolute stability cannot be accomplished, bridge plating is then carried out. Once fixation is complete, it is helpful to provide documentation of where the radial nerve crosses the plate (i.e., which hole) following fixation in case revision surgery is required in the future.