low lying medial triceps

The medial head of triceps is always the muscle most intimate to the ulnar nerve in the cubital tunnel. The medial head of triceps always bulks up and fills the lateral portion of the cubital tunnel during elbow flexion. As it does this it pushes the ulnar nerve towards the medial epicondyle of the humerus. If you have an intact osbornes fascia / ligament the ulnar nerve stays in the cubital tunnel and the medial head of triceps may squeeze it against the medial epicondyle. If the osborne fascia is deficient or if you scan proximal to the medial epicondyle the medial head of triceps gets underneath the ulnar nerve and pushes it out of the tunnel in the medial direction.
In most people this is a gently subluxation and in some the ulnar nerve snaps out vigorously.
I don’t personally understand the “snapping triceps” as I have never seen a medial head of triceps move in a snapping manner but I do see the ulnar nerve snap vigorously over the edge of the medial epicondyle causing neuritis and symptoms.

The exact size of the media head of triceps and the “low lying” nature of the muscle bulk I think is hard to estimate with ultrasound so I focus on what effect it has on the nerve during elbow flexion.
This emphasises the importance of the supine scanning position and dynamic assessment during full elbow flexion. It is the only way to get a great appreciation of the impact of the medial head of triceps in terms of subluxation and compression of the nerve. Another important thing to remember is the concept of the osborne ligament causing extrinsic compression which I call the “paceman sign” during elbow flexion.

Steve

Have you ever seen a “snapping” medial head of triceps?

I have never seen it, just vigorous snapping of the nerve as it flicks over the medial epicondyle.

I have always been confused about the term and wonder what would make it snap etc.

There are plenty of things that confuse me about ultrasound. This is just one example!

That would be awesome,

I have seen plenty of snapping nerves but never a whole medial head snapping over the medial epicondyle.

It must be a spectacular clinical scenario to palpate.

Steve