Distal humerus fractures in adults are relatively uncommon injuries, representing only about 3% of all fractures in adults. In a study of 4536 consecutive fractures in adults seen in the Massachusetts General Hospital emergency department, only 0.31% were supracondylar (bicolumn) fractures of the distal humerus. Although these injuries are relatively rare, most orthopedic surgeons are called upon to evaluate and treat patients with these injuries and, therefore, must be equipped to achieve optimal outcomes. [1, 2, 3]
We live in a society with a growing elderly population and a young population in which extreme sports and high-speed motor transportation are popular; therefore, the incidence of these fractures is likely to increase. In young adults, most distal humerus fractures occur from high-energy trauma, sideswipe injuries, motor vehicle accidents, falls from heights, and gunshot wounds. In elderly persons with more osteoporotic bone, most of these injuries occur from falls.
Numerous classification schemes have been devised to categorize and discuss supracondylar fractures. In 1936, Reich originally classified these fractures into T and Y variations.  In 1969, Riseborough and Raidin described four categories based on degree of displacement, comminution, and rotation.  As surgeons became more adept at surgical reduction and internal fixation, the Arbeitsgemeinschaft für Osteosynthesefragen–Association for the Study of Internal Fixation (AO-ASIF) group described a classification based on fracture pattern and degree of comminution (see Classification).
Surgical treatment of supracondylar fractures has evolved significantly over the past few decades. In the 1960s and 1970s, most surgeons condemned surgical treatment because of high failure rates with loss of fixation, nonunion, and elbow stiffness. The "bag of bones" treatment was used when bone quality or fracture pattern was not sufficient to gain stable fixation. This led to generally poor and unpredictable results.
In the 1970s, treatment began to shift from casting and the "bag of bones" technique to surgical intervention with limited internal fixation. Again, results generally were poor, owing to lack of adequate stabilization for early motion.
In the early 1980s, the AO-ASIF group reported good and excellent results in 27 of 39 patients with comminuted fractures of the distal humerus. These by far were the best results reported in the treatment of these difficult fractures at that time. This led to an increased enthusiasm for surgical reduction and fixation. Additional surgical approaches were developed, along with more versatile fixation hardware, leading to improved surgical results. The "bag of bones" approach has now largely been replaced by total elbow arthroplasty, allowing improved and more predictable results.
For proper evaluation, planning, and execution of surgical treatment of these fractures, the surgeon must have a solid understanding of the relevant anatomy from both a functional and a surgical perspective. (See the images below.)
Functionally, the elbow joint behaves as a constrained hinge. The olecranon of the ulna articulates around the trochlea of the humerus. The trochlea normally is tilted in 4° of valgus in males and 8° of valgus in females, thus creating the carrying angle of the elbow. The trochlea also is externally rotated 3-8° from a line connecting the medial and lateral epicondyles, resulting in external rotation of the arm when the elbow is flexed 90°.
A second plane of motion occurs with the elbow joint in supination and the forearm in pronation; this range of motion is allowed by the radial head articulation with the capitellum and the ulnar notch.
The surgical anatomy closely mirrors the functional anatomy. For stable elbow motion, the trochlea must be restored to its normal position, acting as a tie rod between the medial and lateral columns of the distal humerus. This forms the triangle of the distal humerus, which is crucial for stable elbow function (see the image below).
Both columns must be securely attached to the trochlea. Every attempt should be made to restore the proper valgus tilt and external rotation of the trochlea so as to achieve stability, full motion, and a normal carrying angle. The coronoid is important to elbow stability and should be reduced and fixated if displaced.
The olecranon fossa, a very thin wafer of bone, does not require restoration if badly comminuted. If the medial and lateral columns can be securely fixated to the trochlea, early motion should be tolerated. The medial column diverges from the humeral shaft at approximately 45°, continues, and ends in the medial epicondyle. Because nothing articulates with the anteromedial epicondyle, the entire surface is available for internal fixation hardware. Care must be taken to protect and transfer the ulnar nerve anteriorly.
The lateral column diverges from the humeral shaft at approximately 20° and is largely cortical bone with a broad flat posterior surface; thus, it is ideal for plate placement. At the posterior capitellum, cancellous screws must be used to avoid interrupting the anterior capitellar cartilage. Biomechanical studies have demonstrated the strongest construct of fixation of bicondylar fractures to be a direct medial plate and posterolateral plate with screws directed at 90° angles. This provides the varus and valgus rotational stability to the construct, thus allowing early range of motion.
The mechanism by which supracondylar humerus fractures occur has been a topic of debate. Historically, the mechanism has been accepted to be an axial load on the elbow, with the olecranon acting as a wedge splitting the medial and lateral columns of the distal humerus. However, mechanical studies performed on cadavers have shown that supracondylar (bicolumn) fractures are more likely to be produced with the elbow flexed beyond 90°. The fracture pattern is related to the degree of elbow flexion and the direction and magnitude of the force applied.
Single-column fractures are relatively rare and account for only 3-5% of distal humerus fractures. Lateral-column fractures are more common than medial-column fractures. These fractures represent the distal extent of the respective column, including a portion of the articular surface. These are described as high or low, depending on the proximal extent of the fracture line and the extent of joint surface involvement. Milch previously described these as medial or lateral condyle fractures. 
Bicolumn fractures are far more common distal humerus fractures. In some reports, these account for as many as 70% of distal humerus fractures in adults. These fractures involve disruption of both the medial and the lateral column, thus disrupting the humeral triangle and resulting in disassociation of the articular surface from the humeral shaft. Successful treatment is most challenging in these fractures.
Outcomes have improved dramatically over the past few decades as surgical technique and instrumentation have improved. Nevertheless, these patients must be informed early in their evaluation that the elbow probably will never be normal.
The goal is to provide a comfortable elbow that functions as near to normally as possible. Most activities of daily living require a flexion range of 30-130°, which allows eating and personal hygiene. Compensating for lack of extension will be easier than compensating for lack of flexion, and compensating for lack of pronation will be easier than compensating for lack of supination.
The final motion achieved appears to be related to the degree of initial trauma energy and to successful restoration of stability allowing early range of motion (ROM). High-energy trauma (eg, gunshot wounds, sideswipe injuries, or injuries from motor vehicle accidents) results in more soft-tissue damage and increased scarring, which is more likely to result in restricted ROM.
Some reports indicate that capsular release performed at the time of initial fixation for these high-energy distal humerus fractures improves the long-term ROM. Flexion usually returns first, within 2-4 months, and final extension may progress up to 12 months after the injury. Use of dynamic extension splints in gaining final extension has been shown to be of some benefit.
Numerous outcome evaluation schemes are available, but in low-energy trauma, a successful outcome is generally considered to be a 15-140° arc of motion with full supination and pronation and no pain or minimal pain. In high-energy trauma, these results are more difficult to obtain. Activity-related pain is present in approximately 25% of patients; however, it does not appear to be directly correlated with the amount of initial energy of trauma or with final ROM.
Farley et al studied outcomes in 444 children with supracondylar humerus fractures according to the type of treating orthopedic surgeon (pediatric or nonpediatric).  Outcome factors included the following:
Open reduction rate
Postoperative nerve injury
Need for physical therapy
Residual nerve palsy at final follow-up
For severe fractures, significantly more fractures were treated with open reduction in the pediatric orthopedic surgeon group than in the nonpediatric group, but there were no other significant outcome differences between the two groups. 
A comparative study of techniques for treating supracondylar humerus fractures in children was carried out by Pescatori et al.