09_musculoskeletal_risks_and_controls_20140117153117 Flashcards
Different joints allow different ranges of movement, as explained below, and also shown in Figure 9.3.
(a) Gliding joints, between the ribs and thoracic vertebrae, for example, allow bones to move or slide past each other. (b) Hinge joints, such as the knee and elbow, allow movements which alter the angle in one plane between two articulating bones. (c) Pivot joints, such as the axis and atlas in the neck, allow rotation. The elbow is also articulated between the radius and ulna to allow the lower arm to be twisted. (d) Ellipsoid joints, such as the wrist, are similar to ball and socket, but have less movement. (e) Saddle joints allow for back and forth or up and down movement, but no rotation. The thumb is the only example of a saddle joint. (f) Ball and socket joints, such as the hip, allow movement in all directions (including rotation). This occurs as the ball-shaped end of one bone (the femur) moves within a cup-shaped cavity of another (the pelvic girdle).
First class levers have the fulcrum in the middle. The effort and resistance are applied at opposite ends. An example is
the movement of the skull on the spinal column.
Second class levers possess the fulcrum at one end and the resistance in the middle. The effort is applied at the other end. An example is
seen when raising the body on the toes.
Third class levers are the commonest type in the body. The fulcrum is at one end of the lever and the resistance at the other end. The effort is applied to the middle. An example is
the flexion of the forearm.
Biomechanics applies the physical laws of mechanics to the human body, enabling estimation of the local mechanical stress on muscles and joints arising from adopting a posture or making a movement. Some important considerations are 8
Joints must be in a neutral position The work should be kept close to the body Bending forward should be avoided Twisting the trunk should be avoided Peak stresses are produced by sudden movementsPostures should be varied, as well as movementsThe duration of continuous muscular effort should be limited Short frequent breaks are better than longer infrequent breaks
Physiological studies permit estimates to be made of the energy demands on the heart and lungs resulting from muscular effort during movements, considering both localised fatigue from continuous localized muscular effort and general body fatigue from carrying out physical tasks over a prolonged period. Important principles include: 2
Limiting the energy expenditure in a task Resting after heavy tasks
Anthropometry is the study of the size and proportions of the human body. Anthropometric principles of importance to the ergonomics of posture and movements include: 2
Taking account of differences in body size when designing workstations, workplaces and accessories etc. Using anthropometric tables that are appropriate for the specific population.
The causes of WRULDs are not clear, but key risk factors are: 7
repetitive work uncomfortable working postures sustained or excessive force carrying out a task for a long period of time poor working environment (example: temperature and lighting) poor work organisation (example: work pressure, job demands, work breaks or lack of them) individual differences and susceptibility (some workers are more affected by certain risks).
Tendonitis (fingers/hand/forearm)
Inflammation of the tendon.
Tenosynovitis
Inflammation of the tenosynovium (tendon sheath) and tendon.
De Quervain’s
Tenosynovitis affecting thumb tendons.
Trigger finger
A stenosing tenosynovitis, locking a finger in either a bent or straight position Note: Stenosing is the narrowing of the tendon sheath.
Carpal tunnel syndrome
Tendonitis or tenosynovitis of the tendon passing through the carpal tunnel compresses the median nerve, affecting sensation on the palm side fingers and thumb.
Shoulder capsulitis (frozen shoulder)
Inflammation of the shoulder capsule, which is the connective tissue around the shoulder joint.
Epicondylitis (example: tennis elbow)
Tendonitis affecting the elbow or knee Note: a condyle is a knuckle joint.
Cervical spondylosis
Degenerative osteoarthritis of the joints between the centra of the spinal vertebrae in the neck. Note: the centra are the solid parts of a vertebra
Tension neck syndrome
Symptoms include: pain, tenderness and stiffness of muscles, signs of hardened bands or nodularities, and muscle spasm.
WRULD Risk factors
Repeating an action Uncomfortable working positions Using a lot of force Carrying out a task for a long period of time Poor working environment Underlying effects of the work and conditions Workers’ individual differences
The key legal requirements are:
The general requirements for risk assessment and management under the Management of Health and Safety at Work Regulations 1999, as amended. The general requirements for workstation and seating design under Regulation 11 of the Workplace (Health, Safety and Welfare) Regulations 1992, as amended.
Manual handling assessment chart (MAC) tool, factors to consider 8
Load weight/frequencyHand distancefrom lower backVertical liftregionTrunk twisting/sidewaysbendingPosturalconstraintsGrip on the loadFloor surfaceOtherenvironmentalfactors
Assessment of Repetitive Tasks (ART) tool, factors to consider 4
Stage A: Frequency and repetition of movements Stage B: Force Stage C: Awkward postures Stage D: Additional factors.
Structure of the spine
(Neck) Cervical area C1 – C7(Chest) Thoracic area T1 – T12(Lower back) Lumbar area L1 – L5(Tailbone) Sacrum and coccyx
The main functions of the spine are to: 3
Provide safe passage for the central nervous system, to and from the brain to the rest of the body. Provide the human with a range of movement and a deal of flexibility that a single fused bone would not. Act as a weight bearing structure for key body aspects, such as the rib cage, muscles, tendons, and nerves.
Intervertebral discs have three main functions:
To act as a shock absorber, cushioning the vertebrae from vibration and compression forces, and spreading the load out across the surface of the bone. Forming a strong link between the vertebrae (hence the term’ slipped disc’ is rather a misleading one). Allowing movement between the bones, while at the same time controlling the extent of the movement (in association with ligaments).
