Prehension+Work Flashcards
What is prehension?
Ability of fingers and thumb to grasp and pick up objects
What are the elements of prehension?
- Area of contact involved
- Numbers of fingers involved
- Finger position
- Thumb position
- Wrist position
What happens to the wrist under radial nerve palsy?
Harder to extend wrist when fingers are flexed
What are the types of prehension?
- Grip
- Pinch
What are the types of grip?
- Power grip
- Precision grip
- Hook grip
- Cylindrical grip
- Lumbrical grip
What are the characteristics of power grip?
- Stability and larger force
- Wrist extension and ulnar deviation
- MP, PIP, DIP are flexed
- Thumb abducted around object
What are the characteristics of precision grip?
- Delicate control
- Thumb partially abducted
- Fingers partially flexed
- Force varies
- Grip modifies according to object
What are the characteristics of hook grip?
- Finger grasp
- PIP, DIP are flexed
- Thumb does not grip
What are the characteristics of cylindrical grip?
- Grasp large cylinder
- Thumb does not touch fingers
- Thumb abduction and opposition
- Finger flexion around object
What are the characteristics of lumbrical grip?
- Flexion of MP
- Extension of PIP and DIP
- Flexion of thumb MP with IP extension
What are the characteristics of tip pinch?
- Precision
- Opposition to fingertip
- Thumb MP and IP flexed
- Finger flexed
What are the characteristics of lateral pinch?
- Key pinch
- Thumb adducted
- Index flexed
What are the characteristics of palmar pinch?
- Pads of finger-thumb
- Thumb = opposition with IP in extension
- Finger DIP extension
How is prehension measured?
- Power grip = dynamometer
- Lateral-palmar-tip pinch = pinch meter
What is the most frequent pinch pattern?
Palmar pinch when holding an object (88%)
What are the most relevant prehension patterns for hand function?
- Palmar pinch (both hands)
- Lumbrical grasp (left hand)
- Cylindrical grasp (right hand)
What are the consequences of ulnar nerve palsy?
- Cause claw hand
- Intrinsic muscles are paralysed
- MP hyperextension
- PIP and DIP flexion
- Harder to pick up things with cylindrical grip and power grip
What are the consequences of median nerve palsy?
- Inability to oppose thumb
- Compensatory movement with thumb adductor
- Index finger flexes more
What are some worksite evaluation methods?
- Kinematic assessment
- Questionnaires
- Force evaluation
- Surface EMG
What variables are assessed during evaluation methods?
- Intensity of the exertion
- Frequency of exertion
- Duration per exertion
- Hand/wrist position
- Duration of the task per day
What is Dartfish?
Movement analysis software using imported video images
What are the risk factors for Work related musculoskeletal disorders (WRMD)?
- Work organization and technology
- Psychosocial factors
- Biomechanical factors
- Environmental
- Recent work changes
- Other employment
- Work history
What is extreme posture?
Flexed, extended, or twisting posture rather than neutral spine
What is prolonged static posture?
Muscles do not relax, posture held for >1 min
What can happen when the arm is elevated higher than 90° for several months?
It can cause shoulder pain and neck pain
What are types of repetition?
- Repetitive: greater than 2/3 of workday
- Frequent: 1/3 to 2/3 of workday
- Occasional: 1/3 or less of workday
What is exertion?
Force required to carry out a task
What happens when a small force increase is required for a repetitive task?
A small increase in force can cause physical symptoms
What determines the risk for injury?
Combination of required force and number of muscle contractions
What causes higher risk of injury?
High repetition, high force, and high posture
What are mechanical risk factors?
- Tool use
- Local pressure
- Impact/vibration
What are the general principles of tool use?
- Should effectively perform intended function
- Appropriate proportion to body size
- Appropriate for strength and capacity of worker
- Design should minimize fatigue
What are considerations for hand tools?
- Handle shape
- Handle length
- Handle diameter
- Texture
- Grip span
- Right or left hand
- Glove use
- Vibration
What is the daily average sitting duration?
13 hours
What are the ideal sitting position characteristics?
- Viewed object at eye level
- Straight wrists
- 90° elbows
- Good lumbar support
- 90° flexed hip
- Adjustable seat height
- 90° knee angle
- Feet flat on floor
- Inclining back rest
- Chair size should match size of worker
What are the benefits of perching?
Provides moderate support and movement, helps reduce spinal load and discomfort
What are the benefits of arm and wrist support?
- 16% reduction in disc pressure
- Lower EMG activity in trapezius
- Moderate evidence that arm rests reduce shoulder and neck pain
- Increased keystroke ability if wrists supported
What are the effects of hand rest and wrist support during typing?
- EDC fatigue after one hour of typing
- Biceps fatigue reduced by use of wrist support
What is good screen positioning?
Should be face to face, 60-70cm from worker, top of screen at eye level
What is good keyboard positioning?
Angled at 0 to 25°, indented keys with light resistance
What is the risk of using keyboards?
Excessive pronation and ulnar deviation
What are mouse biomechanics?
- Mouse is used 38-66% of time spent on computer
- 48% of mouse users keep finger in extension
- Risk for upper extremity disorders if mouse is far from keyboard
What percentage of cellphone users feel neck or hand pain at some point?
85%
