Keywords
cubitus varus - cubitus valgus - lateral radiographs of the elbow
Introduction
A cubitus varus deformity is characterized by medial angulation of the distal humerus, while a cubitus valgus deformity is characterized by lateral angulation of the distal humerus. Although these deformities are present in both children and adults, they are more common in children. A common cause of cubitus varus and valgus deformities in adults is improper fracture healing from childhood fractures, especially after supracondylar fractures for varus and lateral condylar fractures for valgus.[1] Malunion of extra-articular fractures can also occur in adulthood.
These deformities are often identified in plain radiographs, specifically in the anteroposterior (AP) views of the elbow.[2] These views are taken from a superior perspective and encompass the distal humerus, elbow joint, and proximal ulna and radius. Thus, the AP views allow for optimal visualization of the cubitus deformity relative to the proximal radius and ulna. In lateral radiographs, it is generally more difficult to identify cubitus deformities because these views are taken from the side of the patient's arm while the elbow is at a 90-degree angle. Compared with lateral views, it is understandable why AP views are typically used to identify cubitus varus and valgus deformities. Often, these coronal deformities are overlooked unless correlated clinically or compared with contralateral radiographs ([Figs. 1A], [2A]). In this article, we describe few radiological signs to diagnose these coronal deformities.
Fig. 1 Illustrative case of the unaffected side. (A) True anteroposterior radiograph view of the elbow, showing the normal carrying angle (θ) formed between the axis of the humerus and the ulna shaft. (B) Radiographic lateral view of the same elbow, showing the teardrop sign. The radiocapitellar joint (dotted black line) and ulnar–humeral joint line (solid black line) are parallel, suggesting a normal elbow.
Fig. 2 Illustrative case on the affected side. (A) True anteroposterior radiographic view of the elbow, showing a subtly altered carrying angle compared with the normal side. (B) Radiographic lateral view of the same elbow, showing an altered teardrop sign. The radiocapitellar joint (dotted black line) is distal to the ulnar–humeral joint line (solid black line), suggesting cubitus varus. The reverse is true for cubitus valgus. (C) Postosteotomy of the distal humerus with a plate; we can observe that the joint lines are parallel, suggesting a corrected coronal deformity of the elbow.
Report
Many angles are used to define cubitus varus and valgus, one of which is the humerus–elbow–wrist angle. This angle is identified from AP views ([Fig. 1A]) by drawing a line through the center of the distal humerus and the center of the radius/ulna and measuring the angle between them.[3] However, there is no equivalent to compare in lateral radiographs, which would be beneficial as it could substitute the need to obtain contralateral AP radiographs to confirm the deformity. This technical note proposes a new method of evaluating lateral radiographs for cubitus varus and valgus by identifying a key landmark: the overlap of the trochlea and capitellum within the olecranon and coronoid processes.
To accurately assess cubitus varus and valgus deformities, it is essential to obtain a true lateral radiograph of the elbow. Proper patient positioning involves flexing the elbow at 90 degrees, ensuring the shoulder is aligned with the elbow, and keeping the forearm in a neutral position, with the X-ray cassette parallel to the humerus.[4] The radiograph should clearly display the bony landmarks, including the olecranon process, the trochlea, and the capitellum ([Fig. 1B]).
In a normal elbow, the lateral radiograph reveals a teardrop-shaped configuration formed by the superior supracondylar ridge, which descends into the olecranon fossa and extends into the trochlea. This teardrop shape is bordered by the olecranon and coronoid processes and is a critical landmark for assessing elbow alignment ([Fig. 1]). However, in the presence of cubitus deformities and intra-articular fracture malunions, this teardrop sign may be altered or absent, indicating a change in the normal angulation of the elbow joint. When evaluating a lateral radiograph for coronal deformities, it is important to trace the radiocapitellar and ulnotrochlear joint lines. These lines serve as reliable indicators of the elbow's alignment. In a typical scenario, the radiocapitellar line and the ulnotrochlear line should be relatively parallel and aligned.
In cases of cubitus varus, the radiocapitellar line is positioned more distally relative to the ulnotrochlear line, often accompanied by trochlear elevation and capitellar depression ([Fig. 2B]). Conversely, in cubitus valgus, the radiocapitellar line is more proximal, with trochlear depression and capitellar elevation. These positional changes disrupt the normal teardrop sign, providing a radiographic clue to the presence of deformity.
Discussion
The teardrop sign, alongside the alignment of the radiocapitellar and ulnotrochlear joint lines on a lateral elbow radiograph, provides a simple yet effective method for assessing cubitus varus and valgus deformities without requiring an AP radiograph when the technique of obtaining the lateral radiograph is confirmed to be correct. By adhering to proper radiographic techniques and thoroughly evaluating these key landmarks, clinicians can improve the detection and management of these elbow deformities, ultimately leading to better patient outcomes.
Limitations: This technique can be applied to coronal deformities of the skeletally mature distal humerus with no intra-articular involvement of the distal humerus, radial head, or olecranon. A true lateral view is very important to assess these radiological parameters. The teardrop can be absent in few elbows, despite which the joint line relations can aid in screening. Larger cohort studies are needed to determine its clinical utility and validate it.
Conclusion
With this technique, we can screen coronal deformities on lateral views without needing a contralateral radiograph. However, to quantify and compare angulation, a contralateral radiograph is mandatory. Additionally, this technique can be used in acute distal humerus fractures to confirm coronal reduction after fixation with columnar plates or after corrective osteotomy ([Fig. 2C]).
In orthopaedic practice, the assessment of cubitus varus and cubitus valgus deformities—commonly resulting from trauma or improper healing—is crucial for accurate diagnosis and treatment planning. This study proposes a radiographic parameter using a lateral radiograph to assess these angulations in adults as a screening tool without a contralateral radiograph.
