Tag Archives: posterior interosseous nerve

Psoriatic Arthritis of the Elbow

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About chronic synovitis of the elbow in a patient with psoriatic arthritis.

Sometimes patients come to our attention without a specific clinical history, referring just joint pain.

In case of this joint swelling and gross chronic synovitis always think to a rheumatic disorder. Remember that on MRI, psoriatic synovitis appears indistinguishable from that of rheumatoid arthritis. According to the EULAR (European League Against Rheumatism) recommendations – “A definitive diagnosis of rheumatic diseases can be made by assessing the medical history, by performing a physical examination or ordering specific laboratory tests and undertaking imaging investigations”.

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Coronal Ge Stir (left) and T1W Mri scans (0.3 Tesla).

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Coronal GeStir (left) and Sagittal T2w (right) Mri scans (0.3 Tesla). A gross synovitis with pseudonodular distension of the bicipitoradialis bursa is evident.

The Mri examination shows diffuse irregularity of the cortical bone surfaces and entheseal region of tendons and ligaments, with distension of adjacent bursae by fluid collection. All of these findings are well depicted on ultrasound exam.

This patient also suffered for a painful synovial impingement along the course of the posterior interosseous nerve at Frohse’s arcade, best seen with the dynamic ultrasound examination.

With the elastosonography exam you can discriminate the real fluid quote of this chronic synovitis.

Avoid joint aspiration in this kind of situations: it’s like putting a needle into the marmalade! 

Take home message? Keep calm and call a rheumatologist.

Dr. Jeckyll and Mr. Frohse

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‘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.

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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.