Importance of Upper Extremity: Hand function is interconnected with the entire upper extremity, including the shoulder complex, elbow, forearm, wrist, and digits.
Role of Various Parts:
Shoulder Complex: Positions the hand.
Elbow: Moves hand closer or farther from the body.
Forearm: Orients the palm for prehension or release.
Wrist: Provides final orientation and position during manipulation.
Digits: Form based on the task's demands.
Motor and Sensory Functions: Both are crucial for effective hand function.
Sensation: Essential for detecting and manipulating objects.
Functional Position
Typical Functional Position:
Wrist: Slight extension.
MCP, PIP: Slight flexion.
Thumb: Opposition.
DIP: Can be in slight flexion or extension, compensated by MCP or PIP.
Grasp and Prehension
Categories:
Power Grip: Requires strength.
Precision Grip: Requires fine motor control.
Power Grip
Cylindrical Grip: Holding a bottle, hammer, or grip bar.
Spherical Grip: Holding a ball, doorknob, apple, or baby’s head.
Hook Grip: Holding a suitcase handle or shopping bag.
Special Feature: MCPs in extension, IPs in flexion.
Precision Grip
Palmer Pinch: Pad of thumb to pad of other fingers.
Tip Pinch: Tips of thumb and another finger form an “O” shape.
Example: Picking up a needle.
Lateral Pinch (Key Pinch): Pad of thumb to side of index finger.
Muscle Involvement: Adductor pollicis, flexor pollicis brevis, first dorsal interosseous.
Lumbrical Grip: MCP in flexion, PIP and DIP in extension.
Example: Holding a hamburger or notepad.
Importance of Sensory Function
Sensory Impairment: Can significantly affect hand function. Without sensation, manipulating objects becomes challenging.
Example Exercise: Collecting items with blocked vision to understand the role of sensation.
Summary
Hand function is complex and involves coordination of multiple parts of the upper extremity with both motor and sensory functions playing critical roles.