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Safety

Repetitive Motion Injuries

Repetitive Motion Injuries (RMIs), also known as Cumulative Trauma Disorders (CTDs) or Repetitive Strain Injuries (RSIs), represent the most common category of occupational illness in the modern clinical laboratory. Unlike acute injuries caused by slips or falls, RMIs are insidious; they develop slowly over time due to the microscopic accumulation of tissue damage. The daily routine of a laboratory scientist involves thousands of small, precise movements - uncapping tubes, pipetting, keyboarding, and fine-focus adjustment. Without ergonomic intervention, these repetitive micro-traumas can lead to debilitating musculoskeletal disorders, resulting in chronic pain, loss of function, and career-ending disability

Pathophysiology of RMIs

The physiological mechanism of RMI involves the interplay of three primary risk factors: Repetition, Force, and Posture

  • Micro-trauma and Inflammation: Muscles and tendons are designed to contract and relax. When a specific muscle group is used incessantly without adequate recovery time (repetition), microscopic tears occur in the tissue. The body responds with inflammation. If the activity continues, the inflammation becomes chronic, leading to scar tissue formation (fibrosis)
  • Tendonitis and Tenosynovitis: Tendons, which connect muscle to bone, are poorly vascularized compared to muscle. This low blood supply means they heal slowly. Repetitive friction of a tendon sliding through its synovial sheath (as in pipetting) can cause the sheath to swell (tenosynovitis) or the tendon itself to degrade (tendinosis)
  • Nerve Compression: Swelling in confined anatomical spaces can entrap nerves. The classic example is the Carpal Tunnel, a narrow passageway in the wrist housing the median nerve and nine flexor tendons. Inflammation of the tendons compresses the nerve, causing paresthesia (numbness/tingling) and muscle weakness

Common Laboratory RMIs

Carpal Tunnel Syndrome (CTS)

  • Mechanism: Compression of the median nerve at the wrist
  • Laboratory Causes: Pipetting (thumb depression), keyboarding with wrists bent (extension/flexion), and gripping ultrasound probes or transducer heads
  • Symptoms: Numbness in the thumb, index, and middle fingers; shooting pain in the wrist; weakness in grip strength

De Quervain’s Tenosynovitis

  • Mechanism: Inflammation of the tendons on the thumb side of the wrist (abductor pollicis longus and extensor pollicis brevis)
  • Laboratory Causes: The “pinch grip” required for opening specimen tubes, twisting caps, or thumb actuation of pipettes
  • Symptoms: Pain at the base of the thumb, difficulty gripping, and a positive Finkelstein’s test (pain when making a fist around the thumb and bending the wrist)

Lateral Epicondylitis (Tennis Elbow)

  • Mechanism: Inflammation of the tendon insertion point on the outside of the elbow
  • Laboratory Causes: Repetitive wrist extension and rotation, such as aggressive decapping of tubes or prolonged microtomy (turning the flywheel of a microtome)
  • Symptoms: Pain on the outer elbow, weakened grip

Neck and Shoulder Tension Syndrome

  • Mechanism: Static loading of the trapezius and levator scapulae muscles
  • Laboratory Causes: “Microscope Posture” - jutting the chin forward and hunching the shoulders to look into eyepieces. Also caused by working in a Biosafety Cabinet (BSC) with restricted arm movement
  • Symptoms: Chronic stiffness, tension headaches, and burning pain in the neck and shoulders

Task-Specific Risk Factors & Mitigation Strategies

Pipetting

Pipetting is the single most significant ergonomic hazard in the laboratory. A laboratory scientist may perform thousands of pipette strokes per day

  • Risk Factors: High thumb force (plunger resistance), repetitive thumb abduction, and static holding of the pipette (grip force)
  • Ergonomic Solutions
    • Electronic Pipettes: These eliminate the force required for plunger depression and tip ejection
    • Multichannel Pipettes: Reduce the total number of strokes required
    • Posture: Keep the wrist neutral (straight), not bent. Keep elbows close to the body, not “winged” out. Use pipettes with a finger hook to allow the hand to relax the grip between cycles

Microscopy

Microscopy forces the body into a static, constrained posture for extended periods

  • Risk Factors: Anterior neck flexion (looking down), unsupported arms, and contact stress on forearms from the sharp edge of the bench
  • Ergonomic Solutions
    • Adjustability: Use a chair with adjustable height to ensure the eyes align naturally with the oculars. Use tilting/telescoping eyepieces to bring the microscope to the user, not the user to the microscope
    • Arm Support: Use padded forearm rests or “arm boards” to support the weight of the arms, relieving tension on the shoulders (trapezius)
    • Variation: Apply the “20-20-20 Rule”: Every 20 minutes, look away for 20 seconds at something 20 feet away. Physically get up and stretch every hour

Biosafety Cabinets (BSC) & Fume Hoods

Working inside a hood restricts movement and vision

  • Risk Factors: The glass sash forces the user to extend arms forward (reaching) and often blocks the view, forcing neck flexion. The sharp edge of the sash/airfoil can cut into the forearms (contact stress)
  • Ergonomic Solutions
    • Proper Positioning: Position work supplies at least 4 inches back from the sash but within comfortable reach to avoid overextension. Use a height-adjustable chair to ensure the sash opening is at armpit level
    • Padding: Use foam edge guards on the front of the BSC to prevent contact stress on the forearms/wrists
    • Lighting: Ensure the cabinet is well-lit to prevent leaning forward to see (visual strain)

Computer Workstations

Laboratory Information System (LIS) data entry is a major component of workflow

  • Risk Factors: Monitor too high/low, keyboard requiring wrist extension (“claw hands”), and mouse usage requiring reaching
  • Ergonomic Solutions
    • Monitor: Top of the screen should be at or slightly below eye level. Distance should be arm’s length
    • Input Devices: Keyboard and mouse should be on the same level. Use a wrist rest to maintain a neutral wrist posture (floating, not anchored). Keep the mouse close to the keyboard to prevent shoulder strain

Administrative Controls for RMI Prevention

While engineering controls (better equipment) are ideal, administrative controls (changing work habits) are crucial for RMI management

  • Job Rotation: Rotate staff between tasks. Do not assign one person to pipette for 8 hours straight. Alternate between high-repetition tasks (setup) and low-repetition tasks (resulting/analysis)
  • Micro-Breaks: Encourage “stretch breaks” of 30-60 seconds every hour to restore blood flow and reset muscle length
  • Early Reporting: Create a culture where staff report early symptoms (tingling, soreness) immediately. Early intervention (ice, rest, splinting) can prevent the progression to surgical conditions
  • Training: Train staff to recognize neutral posture. A $5,000 ergonomic microscope is useless if the user still hunches over it out of habit