Next Lesson - Conditions of the Hand
Core
Want more information on anatomy before you begin looking at conditions? Head to our articles on Bones of the Hand, Muscles of the Forearm and Bones of the Upper Limb for more information!
Scaphoid fractures account for 70-80% of all carpal bone fractures. They are caused by a fall onto an outstretched hand (FOOSH) and are most common in young adults.
A scaphoid fracture presents with pain in the anatomical snuffbox (a region just below the base of the thumb) that is exacerbated by movement. Complications include a high risk of non-union and avascular necrosis due to the scaphoid bone having a retrograde blood supply (meaning if there is a fracture that disrupts blood supply, the bone may not heal).
The fracture may not show on the initial X-Ray, but the patient should be treated as if a fracture is present. Then a repeat X-ray may be done 10-14 days later, as the fracture can become visible due to bone resorption along the fracture line, although early MRI or CT is often used to confirm the diagnosis. Treatment may or may not require surgery but a splint or cast is used to increase chances of union of the bone fragments.
Image - An X-Ray showing a scaphoid fracture. The red arrow shows the fracture line
Creative commons source by Gilo1969 [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
A Colles’ fracture is an extra-articular fracture of the distal radius with dorsal angulation and impaction (meaning if the fracture looked like this >, the larger end would be on the dorsal side). It is caused by a FOOSH, with a pronated forearm and dorsiflexed wrist.
This condition presents with pain, a 'dinner fork' deformity and swelling. An associated ulnar styloid process fracture is relatively common. Treatment may include casting or surgery.
Image - A drawing of a Colles' fracture
Creative commons source by The Practice of Surgery by Mumford, James Gregory (1910) [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
A Smiths’ fracture is an extra-articular fracture of the distal radius with volar/palmar angulation and impaction (meaning the open bit of the > shaped fracture is on the palmar side). It is caused by a fall onto a flexed wrist or a blow to the back of the wrist. This condition is relatively rare but usually occurs in young males or elderly females.
It presents with pain, a 'garden spade' deformity and swelling. Complications include malunion leading to permanent garden spade deformity, which can in turn lead to carpal tunnel syndrome. Treatment may include casting, closed reduction or surgery.
Carpal tunnel syndrome is the compression of the median nerve as it passes through the carpal tunnel from the forearm into the hand. Risk factors for this condition include: being female, obesity, pregnancy, rheumatoid arthritis and hypothyroidism. It can also present in those who frequently rest on the palmar side of the wrist e.g. when typing. It presents with paraesthesia in the palmar aspect of digits 1-3 and the lateral half of the 4th digit. There is weakness of abduction and opposition of the 1st digit.
Sensation to the palm is spared as the palmar cutaneous branch of the median nerve does not enter the carpal tunnel. Adduction of the 1st digit is typically spared as it is supplied by the ulnar nerve, whereas weakness mainly affects abduction and opposition of the thumb.
Non-surgical treatment includes bracing or splinting and NSAIDs to reduce inflammation and manage pain, as well as avoiding or modifying harmful activities. If the symptoms are more severe, however, surgery followed by exercises to regain full movement is the usual treatment plan.
Diagram - The location where the median nerve is compressed in carpal tunnel syndrome
Creative commons source by Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
Ulnar Nerve Compression in Guyon’s Canal
Ulnar nerve compression in Guyon’s canal is also known as ‘Handlebar palsy’ and is caused by entrapment of the ulnar nerve as it passes superficial to the flexor retinaculum through a tunnel between the pisiform and the hook of hamate. This condition is relatively common in cyclists, hence the name ‘Handlebar palsy’.
Symptoms depend on the branch compressed. Sensory involvement causes paraesthesia in the little finger and ulnar half of the ring finger. Motor involvement weakens the intrinsic hand muscles, including finger abduction and adduction and thumb adduction. The forearm flexor digitorum profundus is supplied proximal to Guyon’s canal and is spared by an isolated lesion here.
Assess the cause of compression, including repetitive pressure, a ganglion or another structural lesion. Reduce pressure and aggravating activities; a short-term wrist splint may help. Persistent symptoms, progressive weakness or a structural cause may require specialist assessment and decompression.
Diagram - A schematic sensory-branch pattern in an isolated Guyon canal lesion. Yellow marks the palmar little finger and ulnar half of the ring finger, including their distal dorsal fingertips. The dorsal ulnar hand and proximal medial palm are spared because their cutaneous branches leave the nerve before it enters the canal. Guyon canal lesions may be sensory, motor or mixed; the shaded pattern does not describe every lesion.
Diagram supplied for SimpleMed, 1 October 2026. Anatomy reference: ulnar nerve anatomy.
A penetrating wrist injury can damage the median nerve. Weakness of the thenar muscles impairs thumb opposition and may produce an adducted thumb with flattening of the thenar eminence as wasting develops. The lateral two lumbricals, supplying the index and middle fingers, may also be affected; their weakness is distinct from the thenar changes.
Sensation over the lateral palm is spared only if the palmar cutaneous branch remains intact. It leaves the median nerve proximal to the carpal tunnel, but a penetrating wound may injure it separately. Sensory sparing cannot be assumed from the label “wrist injury”.
A penetrating wound with signs of median nerve injury needs prompt hand-surgery assessment for exploration and repair if the nerve has been cut. Splinting and hand therapy support recovery as advised by the treating team. Corticosteroid injection for carpal tunnel compression is a different treatment and does not repair a divided nerve.
Image - A hand with ape hand deformity
Creative commons source by Emily Barrett [CC BY 3.0]; resized for this article
A low injury to the ulnar nerve occurs due to a penetrating injury at the wrist. It presents with a ‘low ulnar claw’ - hyperextension at the metacarpophalangeal joints, and flexion at the interphalangeal joints of the 4th and 5th digits. There may also be paraesthesia in the little finger and ulnar half of the ring finger, including their palmar surfaces and distal dorsal skin.
Dorsal ulnar hand sensation may be spared if the dorsal cutaneous branch, which leaves the ulnar nerve in the forearm, remains intact. A penetrating wound can damage that branch separately. Palmar digital sensation in the little finger and ulnar half of the ring finger may be lost; the entire ulnar border is not necessarily spared.
A penetrating wrist wound with signs of ulnar nerve injury needs prompt hand-surgery assessment for exploration and repair if the nerve has been cut. Splinting and hand therapy may support recovery. Pressure modification is relevant to compression neuropathy; corticosteroid injection does not repair a traumatic nerve division.
A low ulnar lesion spares the forearm flexor digitorum profundus. Its continued pull on the ring and little fingers can make clawing more pronounced than in a high lesion that also weakens their deep flexor. This is the ulnar paradox; its prominence varies with lesion completeness.
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
Reviewed by: Dr. Thomas Burnell
Edited by: Dr. Maddie Swannack
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