The human calcaneus gets fractured simply from stumbling, gliding and falling down. Calcaneus fractures are painful, difficult and expensive injuries. Constructive caracteristics and properties of the calcaneus define the risc of fracture. Those have to be found out and taken into consideration in the development of an optimized damping of shoes.
Analysing data from all accidents in 2000 - 2002; in-vitro-experiments; simulation and modelling calcaneus strain in falling down situation; optimizing construction and damping properties of shoes, development of testing standards incl. testing device and limit values.
Results of epidemiological data show that low impact accidents can result in a reasonable amount of calcaneal fractures. These types of fractures are equally severe in terms of surgical reconstruction, rehabilitation and impairment of work ability compared to high impact accidents.
The average person exposed to a low impact accident is 47 years old, male, non-obese and very often new to his work environment. The accident and the subsequent calcaneal fracture occur following a fall and not directly following a slipping movement which most of the time preceeds the accidental fall. Concerning the type of fall, very often falls from a ladder are observed.
Personal characteristics of the falling person (e.g. general health risk factors, use of pharmaceuticals, previous illnesses) and work place characteristics (e. g. work shift) seem to be less relevant than the actual accidental situation. The documentation of clinical data and documentation should be optimized to extract relevant preventive measures.
The experiments simulating accidental situations (SICASA) showed substantial passive loads at the calcaneus even at low falling heights when peripheral feedback was diminished. Following those experiments, safety shoe modifications were tested to evaluate possible shoe based strategies to unload the calcaneal bone in falling situations. The safety shoe modifications were first developed on the basis of single experiment approaches and former experiments with safety shoe prototypes. Modifications were constructed in extreme forms to provoke differentiating results. All modifications were based on the preventive strategies deflected from the former person based studies:
1. Regional cushioning of the foot (load reduction of the hind foot by implementing cushioning elements at different foot regions).
2. Flexibility and time shift of maximal load (optimizing energy absorption characteristics of the shoe by elongating the time between initial contact with the forefoot and impact at the hind foot)
3. sensorimotor control (enhancement of active energy compensation mechanisms)
The results showed that energy can already be absorbed to a grade degree at initial fore foot contact. Moreover all three aforementioned prevention strategies (cushioning, flexibility, sensorimotor control) should be ideally implemented in a state-of-the-art test situation for safety shoes. This test procedure should incorporate a variation of impact situations (fall situations) in terms of falling height and variation of initial foot contact (fore foot / hind foot).
It can be concluded that a typical accidental situation (fall and slip accidents) can be implemented in a standardized test procedure of foot protecting safety shoes. The already developed prototype of a testing apparatus allows qualitative and quantitative evaluations of safety footwear and simulates in-vivo situations of accidental falls with high impact loads of the rear foot complex (calcaneus). An optimization and validation of the apparatus in the future should further contribute to the development of a new harmonized European safety footwear standard for rear foot impact absorption.
-cross sectoral-Type of hazard:
Sturz- und Absturzgefährung, Persönliche Schutzausrüstung, UnfallverhütungDescription, key words:
Finding of parameters of calcaneus fracture, deriving prevention possibilities in creating shoe construction with appropriate damping, standardization