Imaging diagnosis
Case 214
【Progress】
He was scheduled to keep elbow cast for a month.
【Discussion】
There are three protrusions palpable in an elbow joint. Elbow head trusion indicates ulnar olecranon. Lateral and medial protrusions indicate lateral epicondyle and medial epicondyle of humeral bone, respectively. Elbow joint is structured by three bones of upper arm and forearm: humerus, ulna and radius. Elbow joint indicates a general term of three joints (1-3). The joint between ulna and humerus is called a humeroulnar joint, a pure hinge joint which functions extension and flexion. A humeroulnar joint is formed of trochlea of humerus and trochlear notch of ulnar. A joint between radius and humerus is called humeroradial joint, a socket joint. It is formed of head of the radius and capitulum of the humerus. The joint between ulna and radius is called radioulnar joint.
How can these joints be identified or differentiated on MRI ? It looks difficult or tiresome to differentiate humerus from ulna and radius on axial MRI. The clue point for differentiation is to first identify two bones of ulna and radius. It is not so difficult to find two long bones running parallel. Then, ulna and radius can be identified in the elbow joint. The head of radius joints to capitulum of humerus. Trochlea of humerus joints with trochlea notch and olecranon of ulna. These knowledges are important to understand structure of knee joint visualized on MRI.
Elbow joint injures sport players when they use so often elbow joints (4-6). For example, when golf players attempt to hit a golf ball to the middle of the fairway, the ulnar collateral ligament is susceptible to be hurt, while when tennis players attempt to hit a ball to the lateral line of the court, the radial collateral ligament is susceptible to be hurt (5, 6). Baseball pitchers repeatedly throw a ball using flexor muscles which attaches to the medial epicondyle of the humerus. The major league pitchers tend to injure the ulnar collateral ligament. The little league pitchers tend to hurt medial epicondylar epiphysis rather than medial collateral ligament because epicondyle epiphysis is more susceptible to power burden than ulnar collateral ligament in childhood (5, 6).
In our case, he was not a little league baseball player but he dropped from the top of stairs, injuring both epiphyses of olecranon and trochlea.
【Summary】
We presented a twelve-year-old boy in our hospital after dropping from the top of the stairs. MRI of right elbow joint showed bone edema of epiphyses of olecranon and trochlea, indicating traumatic injuries. It is borne in mind that in order to differentiate humerus from ulna and radius, first, radiologists identify radius and ulnar running parallel and then, remind of main two joints of humeroulnar joint between humeral trochlea and trochlea notch & olecranon of humerus and between of head of radius and capitulum of humerus. Tennis player often injures lateral collateral ligament and golf player and pitcher often injures medial collateral ligament.
【References】
1.Appelboam, A, et al. Elbow extension test to rule out elbow fracture: multicentre, prospective validation and observational study of diagnostic accuracy in adults and children. BMJ. 2008; 337: a2428.
2.Palastanga, N, et al. (2012). Anatomy and Human Movement: Structure and Function (6th ed.). Elsevier. ISBN 9780702040535.
3.Ross, Lawrence M. et a;. (2006). Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System. Thieme. p. 240. ISBN 978-3131420817.
4.Thomas, B. P.; Sreekanth, R. (2012). "Distal radioulnar joint injuries". Indian Journal of Orthopaedics. 46 (5): 493–504.
5.Thomson, B. (2015, January 1). (5) Tennis Elbow Treatment By Trigger Point Massage. Retrieved February 17, 2015,
6.Dhami, S., & Sheikh, A. (2002). At A Glance - Medial Epicondylitis (Golfer's Elbow). Factiva.
2020.12.9