Flexor digitorum superficialis
From Ganfyd
| Flexor digitorum superficialis | |
|---|---|
 Muscles of the anterior forearm, including flexor digitorum superficialis | |
| System: | Muscle |
| Function: | Flexes proximal interphalangeal joints of the fingers, secondarily flexing the metacarpophalangeal joints and wrist (region) |
| Origin: | Humeral head - common flexor origin, medial ligament of the elbow Ulnar head - medial border of coronoid process of ulna Radial head - anterior oblique line of the radius |
| Branches: | |
| Insertion: | Sides of the middle phalanges of the fingers |
| Arterial supply: | |
| Venous drainage: | |
| Lymphatic drainage: | |
| Innervation: | Median nerve (C7, C8) |
| Vertebral levels: | |
| Search for Flexor digitorum superficialis in Gray's. | |
Flexor digitorum superficialis (flexor digitorum sublimis, FDS) is a flexor of the fingers. It lies between the deep and superficial muscle groups of the forearm.
Contents |
Surface Anatomy
The tendons of flexor digitorum superficialis form a fullness on the medial side of palmaris longus.
Shape
Flexor digitorum superficialis (FDS) arises from three heads - humeral, ulnar and radial. The muscle lies deep to flexor carpi ulnaris. The three heads unite early in the course of the muscle, then divide into two planes of fibres - superficial and deep. The two planes themselves divide into two tendons, to provide tendons to the four fingers. The tendons pass beneath the flexor retinaculum in the carpal tunnel in their superficial and deep pairs, surrounded by a common flexor synovial sheath with the tendons of flexor digitorum profundus. They then pass beneath the palmar aponeurosis before entering osseofibrous digital tunnels to enter the digits. The insertion of each tendon is complex and described below.
Humeral head
The humeral head of FDS arises from the medial epicondyle of the humerus via the common flexor origin, as well as the ulnar collateral ligament of the elbow and intermuscular septa between it and the other superficial flexor muscles.
Ulnar head
The ulnar head of FDS arises from the medial side of the coronoid process of the ulna (the 'sublime tubercle') above the origin of pronator teres.
Radial head
The radial head of FDS arises from the oblique line of the radius from the radial tuberosity to the insertion of pronator teres.
Superficial fibres
The superficial plane of fibres divides into the tendons for the middle finger and ring finger
Deep fibres
The deep plane of fibres divides into the tendons for the index finger and the little finger
Actions
- Flexion of the proximal interphalangeal joints of the fingers
- Flexion of the metacarpophalangeal joints
- Flexion of the wrist
Joints Affected
Origin
Humeral head:
- Common flexor origin of the forearm
- Ulnar collateral ligament of the elbow
- Intermuscular septa
Ulnar head:
- Medial side of the coronoid process of the ulna
Radial head:
- Oblique line of the radius
Insertion
- Sides of the middle phalanges of the fingers.
The course of the FDS tendon in the finger is complex, partially due to its interaction with the tendon of flexor digitorum profundus (FDP). At the base of the proximal phalanx, the FDS tendon splits to surround the FDP tendon. The two halves of the FDS tendon are attached to the sides of the middle phalanx, whilst FDP passes through the centre to reach the distal phalanx.
The flexor tendons are supplied by vessels from the phalanges, which pass within folds of connective tissue - the vincula tendinum.
Nerve Supply
- Median nerve (C7, C8)
Relations
- Lies between the superficial flexor muscles and deep flexor muscles of the forearm
Clinical Relevance
- FDS and FDP function should be tested in finger injuries. If PIPJ function is intact, FDS is intact; if the DIPJ is isolated and still flexes, FDP is intact.
Variations
- The radial head may be absent
- The little finger portion may be absent
- May have slips from the ulnar tuberosity to the portions for index and middle finger
- May have slips from the deep fibres to FDP
- May have slips from the ulna or annular ligament to the portion for the little finger
