A Pediatric Medial Epicondyle Fracture Cadaveric Study Comparing Standard AP Radiographic View With the Distal Humerus Axial View

Abstract

Background: Controversy exists with regard to the amount of fracture displacement that warrants surgical fixation of medial epicondyle fractures. Inaccurate determination of degree of displacement on plain radiographs may account for the disputed management. Recently, a novel distal humerus axial radiograph technique has been developed to improve the accuracy of radiographs. The purposes of the study are 2-fold; to identify the anatomic orientation of the medial elbow epicondyle physis in children and to compare the accuracy of determining fracture displacement between axial radiographs and standard anterior-posterior (AP) radiographs in a cadaveric medial epicondyle fracture model. Methods: Twelve pediatric elbow computed tomographic scans and 19 pediatric elbow magnetic resonance imaging scans were analyzed for the orientation of the medial elbow physis. After determining the correct orientation, 15 adult cadaveric medial epicondyle fracture models were created at displacements of 2, 5, 10 mm, and maximum displacement with elbow at 90 degrees of flexion. A linear mixed model regression analysis was used to compare displacement based on the axial versus the AP radiographic methods. Results: The medial epicondyle physis was found to be a posterior structure angled distally at ~36 degrees (range, 10.7 to 49.6) and angled posteriorly at 45 degrees (range, 32.2 to 59). The AP radiograph significantly underestimated displacement relative to the axial radiograph at 5 mm [mean difference, −1.6; 95% confidence interval (CI), −2.9 to −0.3], at 10 mm (mean difference, −4.5; 95% CI, −5.8 to −3.2 mm), and at maximal displacement (mean, 15 mm; range, 13 to 20 mm) (mean difference, −7.1; 95% CI, −8.3 to −5.8). Conclusions: The medial epicondyle physis of the distal humerus is a posterior structure angled distally and posteriorly. When displacement was >5 mm, the distal humerus axial radiograph technique was significantly more accurate than the AP radiograph technique at determining actual fracture displacement in our adult cadaveric fracture models. Therefore, we recommend clinicians to include the axial radiograph view during the evaluation of patients with medial epicondyle fractures. Clinical Relevance: This study provides further insight into the location and orientation of the medial humeral epicondyle physis, and further supports the improved accuracy of the distal humerus axial radiograph at detecting displacement in medial epicondyle fractures.

A Corresponding Point Measurement System Provides Reliable Measurement of Displacement for Medial Epicondyle Fractures

“…The lower reliability noted here relative to 2 previous cadaveric studies 23,32 likely represents the difference between the less than perfect real-world imaging with overlying soft-tissue swelling and a controlled cadaveric study. Once a measurement is deemed reliable, it should also reflect the true degree of separation between the 2 measurement points.…”

Fracture-Separation of the Medial Humeral Epicondyle Caused by Arm Wrestling: A Systematic Review

“…23 Several studies demonstrated that standard radiographic views of the elbow were unable to accurately portray the true displacement. 8,42 In particular, because the anterior displacement is significantly underestimated, 15 an internal oblique radiograph, 23 an axial view of the distal humerus, 51 and 3-dimensional computed tomography 15 are recommended to measure the true displacement of the fragment. Consequently, application of the Watson-Jones classification to the MHE fracture caused by arm wrestling, which determines the degree of displacement of the MHE fragment in the anteroposterior view, is not appropriate.…”

“…7 The epiphysis of the MHE is a posterior structure on the distal humerus and faces backward and downward, with a reported median coronal plane angle of the physis of 36 and a median axillar plane angle of 45 . 8 Numerous muscles, including the flexor carpi radialis, flexor carpi ulnaris (FCU), palmaris longus, flexor digitorum superficialis, and part of the pronator teres, originate from the MHE, forming the flexor-pronator muscle complex (Figure 1). The pronator teres originates from not only the common tendon of the flexor-pronator muscle complex but also from the medial supracondylar ridge just proximal to the MHE, medial intermuscular septum of the arm, antebrachial fascia, and ulna.…”

“…7 The epiphysis of the MHE is a posterior structure on the distal humerus and faces backward and downward, with a reported median coronal plane angle of the physis of 36° and a median axillar plane angle of 45°. 8…”

Use of Digital Tomosynthesis in Assessing Accurate Medial Epicondyle Fracture Displacement as Compared With Conventional Radiography and Computed Tomography

“…Soft tissues were dissected and a medial epicondyle fracture was created by a pediatric orthopaedic surgeon under direct visualization using an osteotome, taking care to simulate the relatively posterior and oblique orientation typical of a medial epicondyle fracture. 23 Each fracture fragment was displaced anteriorly and inferiorly to varying degrees and secured in place with 2 stout radiolucent sutures to maintain roughly constant position throughout the imaging process. More secure Kirschner-wire (k-wire) fixation would have been ideal but produced too much imaging artifact.…”