While I do not suggest holding focus on any one area of the body it is essential to understand all parts to be able to see the whole unit as a whole unit! Due to a recent clinical interaction that forced me to pick out the spaces that are created with the long head of triceps brachii as a common boundary I will take a little time to speak about these spaces!
As always we will start with the anatomy – the triceps brachii has three heads: the long head, the medial head, and the lateral head (click here for the specific origins). All three heads converge to form the triceps tendon and attach to the olecranon process of the ulna. We are clearly focusing on the long head of triceps brachii…but why? The unique part of the long head is that it has an attachment to the scapula at the infraglenoid tubercle (the other two heads run from the posterior/dorsal side of the humerus to the triceps tendon). Since I can’t stop there – the long head of triceps runs in between teres major and teres minor. By essentially splitting these two muscles, the long head of triceps creates the quadrangular space and the triangular space while also creating the triangular interval between its own lateral border and the humerus.
The three spaces above require some further explanation. The triangular space is a passage for the circumflex scapular artery and vein which provide which provide supply and drainage to the infraspinatus, teres major, teres minor, long head of triceps, and a portion of the deltoid. The quadrangular space is a passage for the posterior humeral circumflex artery and vein (supplying/draining teres minor and the deltoid) as well as the axillary nerve (C5-C6 and providing motor tone to the teres minor and deltoid). The triangular interval provides passage for the profunda brachii artery and associated veins (supply/drainage for the triceps brachii and anconeus as well as the nutrient artery to the humerus) as well as the radial nerve (C5-T1 also providing motor tone to the triceps and anconeus as well as the posterior compartment of the forearm).
Alright, we know there are three spaces that share the long head of triceps as a common boundary, we also know that nerves and fluid vessels pass through them…so what? Well, if there is an alteration in the position/tone of the long head of triceps brachii there is going to be a related change in all of the aforementioned spaces which will alter nerve, artery, vein, and lymphatic functions that pass through these spaces. Simple enough right?
What made me have to think about these spaces? I had a young child that had a very localized rash on the posterior aspect of the right brachium – not a bad rash but a rash nonetheless. Knowing that the rash was indicative of a drainage issue I had to reason that one of the spaces was altered and compressing the drainage of the posterior aspect of the brachium. In this case it was the triangular interval which will carry supply and drainage to the area (all three spaces are affected however the only one displaying alteration in the skin was the triangular space). The long head of triceps was displaying a dis-coordination and the correction lay in coordinating the sacpula/humerus/ulna via the long head of triceps as the soft tissue line that was showing altered force transmission. Also, reasoning that the triangular interval led the drainage in to the axilla I had to also consider the axillary vein and the subclavian vein as the continuation of the drainage pathway. The reasoning process was the important part and the result was that the rash disappeared on its own within a few days.
What is the point of this? The understanding of functional anatomy is what provides the solution to health issues. In my view, whatever it is worth (especially as I am still a student), the in depth understanding of functional anatomy is the foundation that Osteopathy stands on. If the functional anatomy is not understood then the results will show that. Dig on!