University of Pennsylvania Orthopaedic Journal Volume 19 Tips and Techniques- Surgical Fixation of Extra-articular Distal Humerus Fractures with a Posterolateral Locking Compression Plate (LCP). John Scolaro, MD, Jonas L. Matzon, MD, Samir Mehta, MD Introduction The appropriate treatment of extra- articular distal humerus fractures is controversial. While functional bracing has been shown to result in good outcomes, some surgeons continue to favor operative fixation. 1 Specifically, they cite concerns of radial nerve injury, difficulty in controlling fracture alignment, and long-term elbow stiffness with bracing. 2 Jawa et al compared functional bracing with plate fixation and found that operative treatment achieves more predictable alignment and potentially earlier return of function while risking iatrogenic nerve injury, infection and re- operation. 2 However, in this study, the operative technique was not uniform, with various exposures and fixation strategies. When operative fixation is indicated for humeral shaft fractures, plate osteosynthesis is the gold standard to which other methods must be compared. 3 Most authors recommend using a 4.5-mm low-contoured dynamic compression plate (LC-DCP) with 4.5-mm diameter screws and obtaining eight cortices of purchase both proximal and distal to the fracture. 3,4 However, adhering to these principles becomes difficult in distal humeral shaft fractures, especially those around the metaphyseal transition zone between the shaft and the supracondylar ridges. Schatzker and Tile advised plating the humerus posteriorly in order to utilize the flat posterior surface to achieve adequate distal fixation. 4 However, fractures at the metaphyseal junction are problematic because plates of adequate length can impinge on the olecranon fossa. Moran attempted to solve this dilemma by using an oblique posterior plate orientation with a 5-8˚ angle off-center from the long axis of the humerus and angling the most distal screw proximally. 5 While improving distal fixation, the obliquity of the plate limited proximal fixation, which was problematic in comminuted or segmental fractures. 5 In 2005, Levy reported excellent results in 15 patients using an alternative method of osteosynthesis with a modified lateral tibial head buttress plate. 6 This modified Synthes plate had an angular offset of 22˚, which allowed the plate to contour to the posterolateral column and also to extend proximally up the humeral shaft. We describe the use of a small fragment pre-contoured extra-articular distal humeral locking compression plate (LCP) for treatment of extra-articular distal humeral fractures. Anatomy The anatomy of the middle and distal humerus is important to understand before surgical fixation is contemplated. Injury to the radial nerve may occur at the time of the initial trauma from the fracture itself 7 or may be iatrogenic at the time of the attempted surgical fixation. 8 The radial nerve arises from the posterior cord of the brachial plexus and must always be accounted for when treating distal humeral shaft fractures with proximal extension or proximal fixation. From the middle to distal third of the humerus, the radial nerve courses in a caudal and lateral direction around the posterior humerus to define the spiral groove. In a cadaveric study by Gerwin et al., the nerve crossed the humerus approximately 20.7 ± 1.2 cm proximal to the medial epicondyle and 14.2 ± 0.6cm proximal to the lateral epicondyle. 9 In 95% of cases, the radial nerve pierces the lateral intramuscular septum within 5mm of the junction of the middle and distal third in a line joining the lateral border of the acromion and the lateral epicondyle. This guideline can be useful clinically when surgically approaching the posterior aspect of the humerus. 10 Branches to the lateral head of the triceps were noted from the radial nerve as it passed along the posterior aspect of the humerus. Branches to the medial head were not noted to occur until the nerve had reached the distal-lateral portion of the humerus