Cutting edge Orthopedics

Supracondylar Humerus Fractures • 5  Mechanism of Injury Extension Type Extension-type supracondylar fractures are typically due to a fall on an outstretched hand with the elbow fully extended [5, 8, 19]. In children 3 years of age and younger, falls typically occur off of objects about 3–6 ft high in the home (i.e., bed, couch, etc.) [4]. Children aged 4 and greater typically fall off playground equipment, most commonly the monkey bars [4]. The non-dominant upper extremity is more commonly injured [3, 4], which may be due to an attempt to regain balance with the dominant hand, such as trying to continue holding onto the monkey bars [4]. During a fall on an outstretched hand with the elbow extended, hyperextension of the elbow typically occurs. The olecranon engages in the olecranon fossa and acts as a fulcrum for linear forces transmitted through the anterior capsule. The tensile load anteriorly results in bending about the olecranon fossa and, ultimately, disruption of the anterior cortex and anterior peri- osteum [5]. In addition to the posterior displacement characteristic of the Type IIA extension- type injury, the distal fragment may displace in a posteromedial or posterolateral direction [5]. Posteromedial displacement is more common, and the medial periosteum typically remains intact [5, 19]. Conversely, with posterolateral displacement, the lateral periosteum usually remains intact [5]. In Type III fractures, the posterior cortex is fully disrupted, and Type IV fractures have complete loss of the anterior and posterior periosteum, which is typically determined with intra- operative fluoroscopy [5, 17]. acture with lized poste- IA fracture to the ante- d elbow in line should ourtesy of Fig. 4.4 Lateral view of a Gartland Type IIB fracture demonstrating an intact posterior hinge with rotation deformity (Courtesy of Joshua M. Abzug, MD) Fig. 4.5 Lateral view of a Gartland Type III fracture with complete displacement of the distal fragment (Courtesy of Joshua M. Abzug, MD) Fig. 5: Lateral view of a Gartland Type III fracture with complete displacement of the distal fragment (Courtesy of Joshua M. Abzug, MD).