Analysis of stress upon hip joint cartilage during working tasks associated with exposure

Status:

completed 09/2015

Aims:

Wear of the major joints (osteoarthritis) in the hip and knee is among the most serious diseases of the musculoskeletal system, and is associated with major health constraints and economic repercussions. In the current literature, indications are growing that occupational risk factors such as the lifting and carrying of heavy loads or frequent climbing of stairs and ladders are a factor in the incidence of hip osteoarthritis. The biological plausibility of these factors, which was not previously known, was to be examined in the course of a biomechanical and orthopaedic study of the mechanical stresses upon the hip joint cartilage during tasks associated with exposure to such stresses (DGUV Study FF-FB-192: Stresses and strains in hip joint cartilage during occupational activities). The IFA project focussed upon analyses of workplaces and recording of the underlying kinematic and dynamic conditions of stress upon the hip joint.

Activities/Methods:

In the course of a research project conducted jointly with the DGUV's BGU Murnau accident clinic, biomechanical movement and stress analyses of typical work tasks were conducted at the IFA with experts from affected sectors. Following preparation, the measurement data then served as input variables for N-body simulation and finite-element analysis (FEA) for the determining of hip joint forces and pressure distribution upon the joint cartilage surface. This part of the project was conducted at the BGU Murnau, the project partner.

In the first phase and in cooperation with the accident insurance institutions, the IFA used available bodies of measurement and other data in order to identify affected sectors and workplaces, and conducted a survey of prevention experts at the accident insurance institutions. The results were used to create a number of different model task scenarios, for example for the lifting, carrying and handling (on the level) of loads (25 to 50 kg) and for the climbing of stairs and ladders, and to simulate these scenarios with suitable structures in the IFA's biomechanics laboratory.

Results:

The highest hip joint forces, at 6.4 times body weight, were measured during handling of a 50 kg load. During walking (at a speed of 1.1 m/s), the test subjects attained on average a maximum force of 3.7 times body weight. During lifting and carrying of the 50 kg load, the maximum hip joint forces were 4.9 to 5.6 times body weight. Lifting and carrying of a 25 kg load (3.5/4.1 times) led to no significant increase in the hip joint loading compared to walking. Equally, the maximum hip joint forces during the climbing of stairs without additional load and during the climbing of ladders did not differ significantly from those for walking.

The maximum peak pressure at the hip joint surface in all tasks studied, 22.8 MPa, was attained during handling of a 50 kg load. This is approximately 1.5 times the maximum pressure arising during walking (15 MPa). By contrast, the contact surface area and the pressure distribution were substantially dependent upon the hip joint position/flexion.

The data obtained will in future support the acquisition of more valid exposure data and research into the mechanically induced pathomechanisms of hip joint disorders

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