Flexor digitorum superficialis muscle

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Flexor digitorum superficialis (FDS) is a muscle in the forearm of humans that is involved in flexing the fingers. Specifically, it acts on the middle phalanges of the four fingers excluding the thumb. It is considered one of the most important muscles for hand function, playing a crucial role in gripping and manipulating objects.

Anatomy

The Flexor digitorum superficialis muscle originates from two main locations: the humerus bone (mediolateral epicondyle) and the ulna. It also has origins from the radius bone. From these points, the muscle extends down the forearm, passing through the carpal tunnel in the wrist, and eventually divides into four tendons. Each tendon inserts into the sides of the middle phalanges of the four fingers.

This muscle is unique because it has a split (bifurcated) tendon at its insertion point, allowing it to act on two joints of each finger: the proximal interphalangeal joints (PIP) and the metacarpophalangeal joints (MCP). The FDS is situated above the Flexor digitorum profundus muscle (FDP), which it partially covers.

Function

The primary function of the Flexor digitorum superficialis is to flex the middle phalanges at the PIP joints of the four fingers. Additionally, because of its attachment to the MCP joints, it also assists in flexing the fingers at these joints. This dual action makes the FDS essential for tasks that require gripping or holding objects. The muscle is innervated by the median nerve, which controls its movement.

Clinical Significance

Injuries to the Flexor digitorum superficialis can significantly impair hand function. Such injuries may occur due to trauma, repetitive strain, or during surgical procedures. Conditions like tendonitis can also affect the FDS, leading to pain and reduced mobility in the fingers. In some cases, surgical repair may be necessary to restore function.

Examination

Clinical examination of the FDS function involves specific tests to isolate this muscle's action from the Flexor digitorum profundus. One common test is to hold the finger at the base and ask the patient to flex at the PIP joint, which should be possible if the FDS is intact.

Treatment

Treatment for issues with the Flexor digitorum superficialis depends on the severity and cause of the problem. Non-surgical treatments include physical therapy, anti-inflammatory medications, and splinting. In cases where these methods are ineffective, surgical intervention may be required.

See Also

• Flexor digitorum profundus
• Carpal tunnel syndrome
• Tendonitis
• Median nerve