OpenDissectAll lessons › Upper limb · 6 min
The shoulder: rotator cuff, deltoid and the axillary nerve
Rotator cuff tears, dislocations and proximal humerus fractures: the shoulder in five steps.
The 3D model turns, lights up each structure and labels it while you read. Free, in your browser, with a short quiz at the end.
Start the lesson in 3D →1. Bones
A large humeral head sits on a small, shallow glenoid of the scapula: lots of movement, little bony stability. The clavicle is the only bony connection of the arm to the trunk.
Surgeon’s corner: Because the bony fit is poor, stability comes from the labrum, capsule and rotator cuff. Anterior dislocation is by far the commonest.
2. The rotator cuff
Four muscles wrap the head like a cuff (SITS): supraspinatus (abduction, on top), infraspinatus and teres minor (external rotation, behind) on the greater tuberosity, and subscapularis (internal rotation, in front) on the lesser tuberosity.
Surgeon’s corner: Supraspinatus tears most often (impingement under the acromion). Jobe test for supraspinatus, external rotation lag for infraspinatus, belly press and lift-off for subscapularis.
3. Deltoid
The deltoid caps the shoulder with three parts (clavicular, acromial and spinal) and inserts halfway down the humerus on the deltoid tuberosity. It is the main abductor after the first 15°.
Surgeon’s corner: The deltopectoral approach goes between the deltoid and pectoralis major, along the cephalic vein, leaving both muscles intact.
4. The axillary nerve
The axillary nerve runs backwards below the shoulder joint through the quadrangular space with the posterior circumflex humeral artery, then winds around the surgical neck of the humerus on the deep surface of the deltoid, about 5–7 cm below the acromion.
Surgeon’s corner: Always test the "regimental badge" sensation before and after reducing a dislocation. In a deltoid-split approach, never split more than 5 cm below the acromion.
5. Cephalic vein and axillary artery
The cephalic vein runs in the deltopectoral groove and dives through the clavipectoral fascia into the axillary vein. Deeper, the axillary artery runs with the cords of the brachial plexus behind pectoralis minor.
Surgeon’s corner: The cephalic vein is the landmark of the deltopectoral interval and the vein used for a port-a-cath cut-down or pacemaker leads.
The 3D model turns, lights up each structure and labels it while you read. Free, in your browser, with a short quiz at the end.
Start the lesson in 3D →