Palmar Aponeurosis
Strong, well-defined part of deep fascia of the palm. Triangular. Covers long flexor tendons and superficial palmar arch. Mainly longitudinal fibres with some transverse fibres.
Morphological note: Represents the degenerated distal tendon of palmaris longus. Absent palmaris longus (~15%) → aponeurosis still present but thinner.
Apex
- Narrow proximal end, directed towards wrist
- Blends with flexor retinaculum
- Superficial fibres continuous with tendon of palmaris longus
Base
- Broad distal end, directed towards roots of fingers
- Divides into four longitudinal slips (one per medial four digits) just proximal to metacarpal heads
- Each slip → two slips → blend with fibrous flexor sheath of corresponding digit
- Digital nerves, vessels, and lumbrical tendons emerge through intervals between the four slips
Borders
| Border | Continuity | Additional Feature |
|---|---|---|
| Medial | Deep fascia over hypothenar muscles | Gives origin to palmaris brevis |
| Lateral | Deep fascia over thenar muscles | — |
Palmar Septa
Fibrous septa pass posteriorly from borders of aponeurosis:
| Septum | Attachment |
|---|---|
| Lateral palmar septum | 1st metacarpal (medial aspect) |
| Medial palmar septum | 5th metacarpal |
| Intermediate palmar septum | 3rd metacarpal |
Palm divided into:
- Thenar compartment (lateral) — between lateral and intermediate septa
- Midpalmar compartment (medial) — between intermediate and medial septa
- Hypothenar compartment — medial to medial septum
Intermediate septum = lateral wall of midpalmar space + medial wall of thenar space → important in palmar infection spread.
Functions
- Fixes skin of palm → prevents sliding during grip
- Protects flexor tendons, superficial palmar arch, digital nerves and vessels
- Provides origin for palmaris brevis (medial border)
Applied Anatomy
Dupuytren’s Contracture
Progressive fibrosis and contracture of palmar aponeurosis — predominantly medial (ulnar) part.
| Feature | Detail |
|---|---|
| Pathology | Interstitial fibrosis → thickening and shortening of medial aponeurosis |
| Most commonly affected | Ring finger; little finger next |
| Deformity | Proximal and middle phalanges progressively flexed; cannot be straightened |
| Distal phalanx | Unaffected — aponeurosis does not reach it |
| Associations | Alcoholic liver disease, epilepsy, diabetes, trauma |
| Treatment | Conservative (early); surgical fasciectomy (grossly impaired function) |
Key point: Distal phalanx NOT flexed — slips attach to fibrous flexor sheath, not distal phalanx.
The palmar aponeurosis is the strong, well-defined part of the deep fascia of the palm. It is triangular in shape and covers the long flexor tendons and the superficial palmar arch. It is made up mainly of longitudinal fibres with a few transverse fibres intersecting them.
Morphological note: The palmar aponeurosis represents the degenerated distal tendon of palmaris longus. When palmaris longus is absent (~15% of individuals), the aponeurosis is still present but thinner.
Apex
- The narrow proximal end, directed towards the wrist
- Blends with the flexor retinaculum
- Superficial fibres are continuous with the tendon of palmaris longus
Base
- The broad distal end, directed towards the roots of the fingers
- Just proximal to the heads of the metacarpals, divides into four longitudinal slips — one for each of the medial four digits
- Each slip further divides into two slips which blend with the fibrous flexor sheath of the corresponding digit
- Digital nerves, vessels, and lumbrical tendons emerge through the intervals between the four longitudinal slips
Borders
| Border | Continuity | Additional Feature |
|---|---|---|
| Medial border | Continuous with deep fascia over hypothenar muscles | Gives origin to palmaris brevis muscle |
| Lateral border | Continuous with deep fascia over thenar muscles | — |
Palmar Septa
From the borders of the palmar aponeurosis, fibrous septa pass backwards to divide the palm into compartments:
| Septum | Origin | Attachment |
|---|---|---|
| Lateral palmar septum | Lateral border of aponeurosis | 1st metacarpal (medial aspect) |
| Medial palmar septum | Medial border of aponeurosis | 5th metacarpal |
| Intermediate palmar septum | Near medial border, oblique | 3rd metacarpal |
These septa divide the palm into:
- Thenar compartment (lateral) — between lateral and intermediate septa
- Midpalmar compartment (medial) — between intermediate and medial septa
- Hypothenar compartment — medial to medial septum
The intermediate palmar septum forms the lateral wall of the midpalmar space and the medial wall of the thenar space — clinically important in spread of palmar infections.
Functions
- Fixes the skin of the palm — prevents skin from sliding during gripping; improves firmness of grip
- Protects underlying structures — long flexor tendons, superficial palmar arch, digital nerves and vessels
- Provides origin for palmaris brevis (from medial border)
Applied Anatomy
Dupuytren’s Contracture
A progressive fibrosis and contracture of the palmar aponeurosis, predominantly affecting its medial (ulnar) part.
| Feature | Detail |
|---|---|
| Pathology | Interstitial fibrosis → thickening and shortening of the medial part of the aponeurosis |
| Finger most commonly affected | Ring finger (most common); little finger next |
| Deformity | Proximal and middle phalanges progressively flexed and cannot be straightened |
| Distal phalanx | Unaffected — aponeurosis does not reach it |
| Cause | Idiopathic; associated with alcoholic liver disease, epilepsy, diabetes, trauma |
| Treatment | Conservative (early); surgical fasciectomy (partial or complete) when hand function is grossly impaired |
Key distinguishing point: In Dupuytren’s contracture, the distal phalanx is NOT flexed — the contracture only involves the proximal and middle phalanges because the palmar aponeurosis slips attach to the fibrous flexor sheath, not to the distal phalanx.
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