about ultrasound findings of post-traumatic ulnar nerve subluxation
This is the case of a direct blow to a flexed elbow. The X-ray and Mri exams show a condylarfracture of the humerus, with a partial cortical bone detachment; a gross joint capsule distension is also evident.
Coronal Xbone-T1w Mri scan (0.3 Tesla) and Plain Radiography.
Coronal Stir (left) and T1w (right) Mri scans of the same patient (0.3 Tesla).
Why ultrasound in this case? Because after 1 month the patient feels pain on the posterior-medial aspect of the elbow, especially during the flexion-extension active movement, with distal pain irradiation to the forearm.
The dynamic ultrasound exam better depicts the clinical picture of a post-traumatic ulnar nerve subluxation at the sulcus ulnaris, togheter with a gross joint synovitis.
Axial T2w (left) and Stir (right) Mri scans of the same patient (0.3 Tesla).
‘Man is not truly one, but truly two’ – Robert Louis Stevenson’s Strange Case of Dr Jekyll and Mr Hyde
When I was studying the anatomy, I used to improve my memory combining the information I wanted to remember with a visual image, a sentence, or a word. The posterior interosseous nerve is the continuation of the deep branch of the radial nerve; he passes beneath the Frohse’s arcade, a fibrous arch between the two heads of the supinator muscle. The deep branch of the radial nerve and his continuation… two sides of the same coin… In the same period I was reading the Stevenson’s novel, so easy for me to combine the duplicity of the nerve with the main character of the book.
A compressive entrapment of the posterior interosseous nerve is called Radial Tunnel Syndrome and the arcade of Frohse is the most common site of compression.
Axial Ultrasound and T2w Mri scan (0.3 Tesla) of the Frohse’s arcade normal anatomy.
The early diagnosis of this pathological condition can be easily done with dynamic ultrasound examination; repeating all the clinical manouvres is possible to directly appreciate the nerve compression syndrome. First of all you need to know where the posterior interosseous nerve is located and how it appears under normal conditions; I suggest you to perform the axial scan. Take a look at the video below and enjoy your study.