168 A high proportion of accidents and a significant amount of ill health are
associated with manual handling operations. Most manual handling accidents reported are sprains or strains, very commonly of the back. These
musculoskeletal disorders arise from the incorrect application andor prolongation of bodily force. Poor posture and extensive repetition of
movement can be important factors in their onset. Other types of injury associated with manual handling operations include fractures, cuts, bruises,
amputations and thermal injury. Many manual handling injuries tend to be cumulative in origin rather than
attributable to any single handling incident. A full recovery is not always made and the outcome can be physical impairment or even permanent disabilities.
The costs to an individual and the employer are therefore far reaching. So our strategy for preventing injury must be preventative and not reactive.
18.3.1 The Back
The spine is a superb and intricate example of engineering excellence, not just the central support system for the body and protection for the spinal cord,
but essential to walking and many other body movements. However, like any other engineering structure it does not respond well to overloading or
maltreatment, either in the form of sudden dynamic overload, repetitive overloads or performing outside its design parameters.
The spine comprises twenty-four bony segments vertebrae with five fused segments forming the sacrum and three to five fused or partially mobile
segments forming a vestigial tail. Between the moveable segments are interposed twenty-three cartilaginous discs which function as excellent shock
absorbers. The curved sequences of the spine allow it to absorb shocks 100 times more efficiently than if it was a straight stack.
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Source: US Federal Government via Wikimedia commons
Figure 18.1 – The Back
The discs contain fluid, excellent for shock absorption, but constant compression squeezes the fluid content making the disks flatter, less flexible
and less elastic. A healthy young disc has a breaking strain of 800kg, stronger than the vertebrae, reducing to 450kg in the elderly.
As a result of repetitive stresses or sudden traumatic stress the central fluid cell may creep through fissures in the fibrous cartilage and eventually
prolapse, emerging from the disc to press excruciatingly on adjoining nerves. Contrary to common belief, discs do not slip Once this occurs, treatment may
be limited to rest, analgesics and physiotherapy. Surgery has a restricted role; it is not practicable to approach the spine from the front and the structure
is so complex and sensitive that any repairs from the rear are limited. Back injuries often result in people taking weeks or months off work, and can
easily recur. It is important that workers are supported by a return to work programme that encourages rapid rehabilitation and keeps them from them
slipping into a state of permanent disability.
170
18.3.2 Making a Manual Handling Assessment
