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Want more information on anatomy before you begin looking at conditions? Head to our articles on Muscles of the Upper Arm, Muscles of the Forearm and Bones of the Upper Limb for more information!
Supracondylar Fracture of the Distal Humerus
Supracondylar fractures of the distal humerus (breaks just above the condyles, the rounded ends at the bottom of the bone) are usually caused by a fall onto an outstretched hand (FOOSH) with a hyperextended elbow (an elbow forced back beyond its normal straight position). They occur most commonly in children and make up around 60% of elbow fractures in this age group. The distal fragment is usually displaced posteriorly. This condition presents with pain, deformity and reduced function of the elbow joint.
Complications of a supracondylar fracture of the distal humerus include:
Damage to ulnar, radial or median nerves (all described later in this article). In the usual extension-type fracture (where the distal fragment is displaced backwards), the median nerve is the one most often damaged, often its anterior interosseous branch (a deep branch in the forearm that supplies the muscles that bend the thumb and the tips of the index and middle fingers). In the less common flexion-type fracture (where the distal fragment is displaced forwards), the ulnar nerve is most often damaged.
Gunstock deformity results from fracture malunion (the bone heals in the wrong position) causing cubitus varus: the carrying angle (the angle between the upper arm and forearm when the elbow is straight and the palm faces forward) is reduced or reversed, and the forearm deviates medially towards the body when the elbow is extended.
Volkmann’s ischaemic contracture (a permanent shortening of the forearm muscles): damage to the brachial artery (the main artery of the upper arm) leads to compartment syndrome (raised pressure inside a muscle compartment that cuts off its blood supply). The muscle then dies (infarction) and is replaced by scar-like (fibrotic) tissue. This complication presents with elbow flexion, forearm pronation (palm turned down), wrist flexion, metacarpophalangeal joint extension (the knuckles bent back) and interphalangeal joint flexion (the finger joints bent).
This condition is diagnosed with an X-ray. Doctors first check the hand’s blood supply and nerve function: a hand that is cold, pale or without a pulse needs urgent assessment by orthopaedic surgeons. A fracture that has not moved out of position (an undisplaced fracture) is treated with a cast or splint while the bone heals. A displaced fracture usually needs a closed reduction (putting the bone back into position without cutting open the skin) with wires placed through the skin to hold it there, and sometimes an open operation.
Diagram - An X-Ray of a normal humerus. The black line (the anterior humeral line) should normally pass through the middle third of the capitulum (highlighted green), but if it doesn't, it indicates that there is a supracondylar humerus fracture
Creative commons source by Tracy Kilborn, Halvani Moodley, Stewart Mears and Mikael Häggström [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
A high injury to the radial nerve usually occurs due to a mid-shaft humeral fracture. This is because the radial nerve runs in the ‘radial groove’ of the humerus, so can be damaged by this mechanism. It presents with:
- Wrist drop due to loss of wrist extension.
- The fingers rest flexed at the metacarpophalangeal joints (the knuckles) because they cannot extend.
- Paraesthesia (altered sensation, such as numbness or pins and needles) over the dorsal aspect (back) of the 1st, 2nd and 3rd digits (the thumb, index and middle fingers; digits are numbered from the thumb), excluding the fingertips.
Elbow extension is spared in the majority of high radial injuries, due to the branch that innervates (supplies) triceps brachii, the muscle that straightens the elbow, being given off proximal to (above) the site of injury.
Most radial nerve injuries with a humeral fracture (about 70 to 85% in systematic reviews) recover without surgery, so treatment is usually a splint and rehabilitation exercises while the nerve recovers, alongside treatment of the fracture. Surgery on the nerve is considered if the fracture is open, scans suggest severe nerve damage, or there are no signs of recovery after a few months. The first signs of recovery can appear anywhere from 2 weeks to 6 months after the injury, and full recovery can take longer. In some people the nerve does not recover.
Diagram: the cutaneous innervation (skin nerve supply) of the upper limbs. The area supplied by the radial nerve is shown in pink
Creative commons source by Henry Gray (1918) Anatomy of the Human Body, modified by Fred the Oyster [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
A high injury to the ulnar nerve (one at the elbow) classically occurs due to a medial epicondyle fracture (a break of the bony bump on the inner side of the lower humerus). It can also follow other elbow injuries, such as a supracondylar fracture, or long-term compression of the nerve in the cubital tunnel (the channel behind the medial epicondyle). It presents with:
- A ‘high ulnar claw’ when asked to extend all the fingers (often less marked than the claw from a low lesion, meaning a damaged area at the wrist; see the ulnar paradox below):
- Hyperextension of the 4th and 5th digits at the metacarpophalangeal joints.
- Flexion of the 4th and 5th digits at the proximal interphalangeal joints (the middle joints of the fingers), but not at the distal interphalangeal joints (the joints nearest the fingertips). This is because the ulnar-innervated part of flexor digitorum profundus (the deep forearm muscle that bends the fingertips) supplying these fingers is paralysed in a complete high lesion.
- Paraesthesia of the 5th digit, the medial half of the 4th digit and the medial border of the hand.
Management of a high ulnar nerve injury depends on whether the nerve is intact (still in one piece, but perhaps bruised or stretched) or divided (cut right through). Splinting and observation may be appropriate for an intact injured nerve; a divided nerve needs specialist assessment for repair. Recovery may take many months, and the final outcome can take two years or longer to become clear.
Clawing may be less pronounced in a high ulnar lesion than in a low lesion. This is because a high lesion also weakens the ulnar-innervated part of flexor digitorum profundus supplying the ring and little fingers. Reduced flexion of the fingertip joints makes the claw less marked: this is the ulnar paradox (a higher, more serious injury gives a milder claw). The appearance varies with the extent of the lesion.
Image: a healthy hand imitating ulnar clawing. The photograph does not document a nerve lesion or establish whether a lesion is high or low.
Creative commons source by Mcstrother [CC BY 3.0]; resized for this article
A high injury to the median nerve (one at the elbow) classically occurs due to a supracondylar humeral fracture. The nerve can also be compressed at the elbow or in the forearm. It presents with:
- Weak or lost forearm pronation (turning the palm to face down)
- Weak wrist flexion, and a thumb that cannot oppose (bring the thumb across the palm to touch the other fingertips) or bend at its end joint, because the thenar muscles (the muscles at the base of the thumb) and flexor pollicis longus (the muscle that bends the end of the thumb) are paralysed
- The traditional textbook ‘Hand of Benediction’ description on attempting a fist (only the ring and little fingers curl fully, while the index and middle fingers stay straight) is not a reliable clinical sign. In practice:
- Index interphalangeal flexion (bending of the finger joints) may be impaired, but index metacarpophalangeal flexion (bending at the knuckle) can remain through the ulnar-innervated interossei (small muscles between the metacarpal bones of the hand). Middle-finger flexion may also remain through variable innervation and connections between the deep flexor tendons (the tendons of flexor digitorum profundus). Absence of the traditional posture does not exclude a high median nerve lesion.
- Flexion of the 4th and 5th digits is preserved, because the ulnar nerve supplies the part of flexor digitorum profundus that bends them.
- Extension and adduction of the 1st digit (the thumb) are preserved, because the radial and ulnar nerves supply the muscles that do these movements.
- Paraesthesia of the palmar aspect of the lateral hand, of the 1st, 2nd and 3rd digits and of the thumb side (lateral half) of the 4th digit.
Management depends on the mechanism and extent of nerve injury. Splinting and observation may be appropriate for an intact injured nerve, while a divided (cut) nerve requires specialist assessment for repair. Recovery is variable and may take many months; the final outcome can take two years or longer to become clear.
Image: a heraldic drawing of the traditional hand of benediction posture. This is not a reliable depiction of the clinical appearance of a high median nerve lesion.
Illustration source from A Complete Guide to Heraldry by Arthur Charles Fox-Davies [public domain]
Edited by: Dr. Thomas Burnell and Dr. Maddie Swannack
Reviewed by: Dr. Marcus Judge
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