Fractures of the humerus and elbow joint
First, some anatomy. We’ve covered the basic anatomy of the shoulder joint above, here we’ll consider the anatomy of the humerus and the elbow.
Proximal anatomy
Remember that the humerus has a surgical and an anatomical neck, with a greater tubercle which serves as an insertion point for three muscles: supraspinatus, infraspinatus and teres minor. There is also a minor tuberculum which is the insertion point for subscapularis. Running between the two tubercles is the sulcus intertubercularis, which serves as a groove for the long head of the biceps. As we move inferiorly, there is the insertion points for the deltoid muscle, along with the origins of the lateral head of the triceps posteriorly. On the anterior surface is the insertion of biceps brachii, pectoralis major and latissimus dorsi
Distal anatomy of the humerus As we move down towards the elbow joint there are the two epicondyles (medial and lateral) associated with the medial and lateral humeral condyles (known as capitulum humeri laterally, and trochlea humeri medially). On the posterior surface we can see the olecranon fossa and the sulcus for the radial nerve (mid shaft) and ulnar nerve (medially).
The head of the humerus forms an angle of 150-180 degrees with the axis of the humeral shaft (the so called collo diaphyseal angle). The head also shows retrotorsion of 15-30 degrees, lying posterior in relation to the distal condyles.
Blood supply to the head of the humerus is via the anterior and posterior circumflex humeral arteries, these can be damaged in fractures of the head of the humerus, as can the axillary nerve which loops around the humeral head. In mid shaft fractures the radial nerve is the most at risk, and it is also at risk of compression injuries. Finally the ulnar nerve in the ulna canal is most at risk of distal humeral fractures.
Proximal anatomy of the Radius and Ulna and anatomy of elbow joint The Ulna articulates with the trochlea of the humerus, with an olecranon posteriorly and a coronoid process anteriorly to provide stability and ligament insertion points. Laterally there is a radial notch where the radial head articulates.
The radius articulates with capitulum of the humerus and it should always align. The radial neck is angulaged 15 degrees and the bone has a tuberosity for the biceps insertion.
The key ligaments in the elbow joint are:
- Medial (Ulnar) collateral ligaments
- Anterior bundle