Extended evaluation of the German Spinal Study (DWS) with the objective of identifying suitable guideline values

Status:

completed 06/2012

Aims:

The published results of the German Spine Study (DWS, see Projects BGIA 4105, "Exposure assessment within the so-called German Spine Study - EPILIFT " and BGIA 4140, "Evaluation and interpretation of the 'German Spine Study' (DWS)") permit the conclusion that there are cumulative models that are better suited to display the risk of discogenic diseases of the lumbar spine than the "Mainz-Dortmunder" Dose model (MDD). Those models are characterized by lowered threshold values for the daily dose and (at the same time) for the compressive force and (at the same time) for the forward inclination of the trunk, and by the inclusion of further modes of material handling such as pulling and pushing. A more differentiated interpretation of the results of the German Spine Study is now to vary the parameters stated (daily dose, compressive force, trunk inclination, mode of material handling) separately from each other, in order to permit scientific discussion of the legal definition of occupational disease No 2108 BKV and the derivation of suitable threshold values.

A further objective of this analysis was to achieve a reasonable reduction in the extensive survey instrument used by the technical inspectorates and described in the German Spine Study, and with reference to the MDD, to adapt this instrument to the demands of a method suitable for use in practice.

Activities/Methods:

During project FF-FB0155, "Extended evaluation of the German Spine Study (DWS) with the objective of identifying suitable threshold values", which was conducted by the DGUV in conjunction with further research establishments, the IFA was involved in reanalysis of the results of the German Spine Study. The IFA's tasks included the provision of compressive force values and of formulae for estimation of the compressive forces for the loads found in the survey form used by the technical inspectorate.

For this purpose, regression equations were to be determined based upon the compressive force values simulated at the IfADo for the combinations of load mass, load position and body posture occurring at the beginning and end of a material handling operation. These equations were then to be reduced in number by reasonable merging of combinations. This reduction was to be accompanied by continual review of the consistency of the daily dose values calculated by means of these formulae with the corresponding simulated IfADo values.

In addition, the incidence of relevant "discrete" loads was to be described, in order to enable any key indicator loads to be identified for formally recognized occupational disease BK 2108.

Results:

A method was developed which contains, for estimation of the compressive force upon the intervertebral disc, both tabular values (for example for eight postures of the upper body, shoveling activities, specific activities in nursing and geriatric care) and a set of formulae (lifting, holding, carrying of loads in various modes) and also modulating factors for the consideration of material handling distant from the body, asymmetrically and with one hand. A progressive reduction of the number of formulae with review of the validity after each step ultimately yielded a set of eleven formulae representing a reasonable compromise between precision and ease of application.

Discrete loads were described for the load modes of lifting, holding, carrying, pulling and pushing of loads, and for different forms of trunk inclination, in each case in the form of annual and daily doses (percentiles) and separately for the different case and control groups.

The instrument developed here may be regarded as an essential basis for a method suitable for determining the exposure in the field during future investigation procedures for BK 2108.

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