Anatomy clinical correlates: Arm, elbow and forearm

The majority of things we do every day require the use of our arms and forearms. Sometimes we forget how heavily we rely on our arms, and are quickly reminded how important they are when injury occurs. So, let's take a look at common injuries occurring to the arm and forearm.

Alright, let's begin by looking at fractures of the humerus, the main bone of the arm. The most common kind are fractures of the surgical neck of the humerus, which occur more frequently in elderly people with osteoporosis who have structurally weaker bones. The cause is usually indirect trauma, like falling on the hand with an extended arm.

Surgical neck fractures can result in damage to nearby structures, such as the axillary nerve causing cutaneous deficits in the proximal lateral arm, as well as damage to the anterior and posterior circumflex humeral arteries.

Next, there are humeral shaft fractures, which are usually caused by direct trauma. Now, remember that the radial nerve passes through the radial, or spiral, groove on the back of the humerus, so a common complication of midshaft humeral fractures is radial nerve injury.

Radial nerve injury results in damage to the extensors of the wrist and potential wrist drop, as well as cutaneous sensation dysfunction of the dorsal hand, forearm, and upper arm. Additionally, the deep brachial artery travels with the radial nerve in the spiral groove and can also be damaged. Finally, distal humeral fractures are a result of trauma to the elbow region, or hyperextension injuries.

In a supracondylar fracture, which is a fracture above the epicondyles, an anteriorly displaced portion of the fractured humerus on the medial supracondylar region could injure the median nerve, resulting in wrist flexion weakness and cutaneous deficits of the anterior 3 and a half digits, as well as the brachial vessels.

An anterior displaced fracture of the lateral supracondylar region could cause damage to the radial nerve, again causing weakness of wrist and hand extensors and posterior forearm and hand sensory loss.

Distal to the supracondylar region, a fracture of the medial epicondyle of the humerus can result in damage to the proximal ulnar nerve. This can occur due to hyperflexion injuries, falling or direct trauma to the medial elbow, or laceration injuries. As a result, there’s sensory loss over the 5th digit and half of the fourth digit, as well as weakness in flexion of the wrist and 4th and 5th digits, making it difficult to make a fist. This is sometimes called a claw deformity, and creates an ‘ok’ gesture when trying to make a fist.

Ok, now, let’s have a look at the elbow region, and discuss another kind of wear-and-tear injury called epicondylitis. Epicondylitis is when there is inflammation and small tears of the tendons that attach to the epicondyle.

Lateral epicondylitis usually results from repetitive use of forearm extensor muscles, which is commonly seen in tennis players, and results in pain around their muscle origin on the lateral epicondyle that radiates down the posterior forearm.

The same thing can happen with the medial epicondyle, which results in medial epicondylitis, or, and here’s another sports injury, “golfer’s elbow”. Medial epicondylitis occurs from repetitive use of forearm flexor muscles, which is commonly seen in golfers, hence golfer’s elbow. This results in pain on the medial epicondyle that radiates down the anterior forearm, which worsens when trying to make a fist, like when squeezing a stress ball.