External landmarks and boundaries
The anterior wrist region is clearly separated from the dorsal region by the radial and ulnar margins. The proximal and distal boundaries are drawn as two transverse lines located 2 cm upward and downward from the level of the tip of the radial styloid process.
Three transverse skin creases are easily visualized on the anterior surface. The most important bony landmarks are the styloid processes of the radius (radius) and ulna (ulna). From the ulnar margin, the pisiform bone (os pisiforme) is palpable, as well as the hook of the hamate (hamulus ossis hamati).
When muscles are contracted, the following tendons are visible under the skin:
- Palmaris longus (tendo m. palmaris longus) — located along the midline and serves as a key to finding the median nerve at the border with the forearm. Distally, it blends into the palmar aponeurosis (aponeurosis palmaris).
- Flexor carpi radialis (tendo m. flexor carpi radialis) — located on the radial side, attaching to the base of the 2nd metacarpal bone.
- Flexor carpi ulnaris (tendo m. flexor carpi ulnaris) — runs from the ulnar side to the pisiform bone.
Layer-by-layer Structure
- Skin in this region is thin and fairly mobile.
- Subcutaneous adipose tissue is moderately developed and has a loose structure. Clinically, it is important to remember that due to this structure, edema fluid accumulates here rapidly.
- Deep fascia (fascia propria) is a thickened continuation of the forearm fascia.
Flexor tendons pass beneath the deep fascia. The tendon of m. flexor carpi radialis is enclosed in a separate synovial sheath, the upper blind end of which projects 1–2 cm above the flexor retinaculum.
Guyon's canal and neurovascular projections
The deep fascia of the wrist region splits at the lateral margin of the pisiform bone, forming Guyon's canal (canalis ulnaris). The ulnar neurovascular bundle passes through it. Within the canal, the ulnar artery (a. ulnaris) lies more superficially and laterally, while the ulnar nerve (n. ulnaris) is located deeper and more medially. The ulnar margin of the pisiform bone is a classic point for performing ulnar nerve block anesthesia.
Radial artery (a. radialis) is projected at the lateral margin of the wrist, 0.5–1 cm lateral to the flexor carpi radialis tendon. At this site, the vessel lies directly on the radius, making it an ideal point for palpating the pulse.
The wrist joint itself is projected along the middle transverse skin crease. The joint line forms an arc whose apex rises 1 cm higher than the line connecting the tips of the styloid processes.
Flexor retinaculum and carpal tunnel
The deep layer of the anterior region forms the flexor retinaculum (retinaculum musculorum flexorum) — the thickest and strongest ligament of the hand, consisting of robust transverse fibers. It has superficial and deep layers.
The ligament bridges across the carpal bones, forming a sturdy carpal tunnel (canalis carpi). The supports for this bridge are bony prominences:
- Laterally (on the radial side): tubercle of the scaphoid bone (tuberculum ossis scaphoidei) and tubercle of the trapezium (tuberculum ossis trapezii).
- Medially (on the ulnar side): pisiform bone (os pisiforme) and hook of the hamate (hamulus ossis hamati).
The tendons of the superficial and deep digital flexors (tendines mm. flexor digitorum superficialis et profundus), the tendon of the long flexor of the thumb (tendo m. flexor pollicis longus), as well as the median nerve (n. medianus) pass in transit through the carpal tunnel from the forearm to the hand.
Briefly: answers to topical questions
What structures pass through the carpal tunnel (canalis carpi)?
The flexor tendons and the median nerve pass through the carpal tunnel (canalis carpi).
- Median nerve (n. medianus) — located superficially and between the tendons within the connective tissue.
- Tendons of the superficial and deep flexors of digits II–V — occupy the medial part of the canal.
- Tendon of the flexor pollicis longus (m. flexor pollicis longus) — located lateral to the digital flexor tendons.
Which nerves provide cutaneous innervation to the anterior wrist region?
Cutaneous innervation of the anterior wrist region is provided by branches of the medial and lateral cutaneous nerves of the forearm.
- Medial cutaneous nerve of the forearm (n. cutaneus antebrachii medialis) — innervates the medial part of the wrist.
- Lateral cutaneous nerve of the forearm (n. cutaneus antebrachii lateralis) — innervates the lateral part of the wrist, particularly the thenar eminence region.
What fascial spaces communicate with the carpal tunnel?
The carpal tunnel serves as a connecting link between the fascial spaces of the palm and forearm. It communicates with the following spaces:
- Pirogov-Parona space — located in the forearm (proximal direction).
- Middle fascial compartment of the hand (including the sub-tendinous fascial space) — located on the palm (distal direction).
- Lateral fascial compartment of the hand — purulent processes from it can also spread through the carpal tunnel.
What branches does the radial artery give off in the anterior wrist region?
In the anterior wrist region, the radial artery gives off the superficial palmar branch.
- Superficial palmar branch of the radial artery (ramus palmaris superficialis a. radialis) — a branch of the radial artery (a. radialis).
- It participates in the formation of the superficial palmar arch (arcus palmaris superficialis) via an anastomosis with the trunk of the ulnar artery (a. ulnaris).
Class and exam questions
Where and how is the radial artery palpated?
The radial artery is palpable 0.5–1 cm lateral to the flexor carpi radialis tendon. At this point, it lies directly on the surface of the radius.
What passes through the carpal tunnel (canalis carpi)?
The digital flexor tendons and the median nerve (n. medianus) pass through the carpal tunnel.
How is Guyon's canal formed and what does it contain?
Guyon's canal (canalis ulnaris) is formed by the splitting of the deep fascia at the lateral margin of the pisiform bone. It contains the ulnar neurovascular bundle (artery laterally, nerve medially).
How to determine the projection of the wrist joint?
It is projected along the middle transverse wrist crease. The joint line forms an arc whose apex is 1 cm above the line connecting the styloid processes.
What else to study on this topic
- Synovial sheaths of the flexor tendons of the hand and wrist
- Anatomical snuffbox: boundaries and contents
- Extensor retinaculum (retinaculum mm. extensorum) and its osteofibrous canals
- Branching of the radial and ulnar arteries: superficial and deep palmar arches
- Projections of the dorsal and superficial nerve branches of the wrist region
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