From the Research
The ulnar nerve is responsible for digit hand abduction, specifically innervating the dorsal and palmar interossei muscles, which are the primary muscles that abduct and adduct the fingers. The ulnar nerve also innervates the hypothenar muscles and the medial two lumbrical muscles, originating from the C8-T1 nerve roots of the brachial plexus, traveling down the medial aspect of the arm, passing behind the medial epicondyle of the humerus, and continuing into the hand 1. Damage to the ulnar nerve can result in weakness of finger abduction, which can be tested clinically by asking a patient to spread their fingers against resistance, as demonstrated in a study on little finger abduction and adduction testing in ulnar nerve lesions 2. Additionally, ulnar nerve injury often presents with sensory deficits in the fifth digit and medial half of the fourth digit, as well as weakness in grip strength due to compromised intrinsic hand muscle function.
Some key points to consider include:
- The ulnar nerve is responsible for innervating the muscles that control finger abduction and adduction
- Damage to the ulnar nerve can result in weakness of finger abduction and sensory deficits
- The ulnar nerve originates from the C8-T1 nerve roots of the brachial plexus and travels down the medial aspect of the arm
- Ulnar nerve injury can be tested clinically by asking a patient to spread their fingers against resistance
- Awareness of anatomical variations, such as the motor Riche-Cannieu Anastomosis, is clinically important when interpreting clinical examination findings and managing patients with ulnar nerve injuries 1, 3.
It is essential to note that the ulnar nerve displays many anatomical variations, often with significant clinical implications, and knowledge of these variations is crucial to clinical practice 3. However, the ulnar nerve remains the primary nerve responsible for digit hand abduction, and damage to this nerve can have significant consequences for hand function and overall quality of life.