An Investigation of an Industrial Accident Resulting in Lumbar Spine Lesions at the Level of L5/S1

Description
The plaintiff was attending to duties at his work station that involved a one arm pulling action, with simultaneous opposite leg action on a treddle release mechanism. The variously defective release mechanism demanded a much stronger pulling action than would normally be required. This resulted in the handle breaking with the plaintiff being thrown backwards. He suffered a rupture of the intervertebral disc at the L5/S1 level. The claim by the plaintiff was complicated by his involvement in a strength sport with the defendants maintaining that it, rather than the workstation malfunction, predisposed the injury. Perform Enhance recommended an investigation into the movement patterns and disc behaviour generated by the sustained bilateral muscle recruitment demanded by the plaintiffs sport, and the explosive unilateral muscle recruitment demanded by the faulty workplace station.

Procedures
Investigation was undertaken at the following levels.

1. Reconstruction of the workstation in the laboratory to enable precise goniometric measurement of the plaintiff in situ.
2. Filming of test subjects in the laboratory as they operated the reconstructed workstation.
3. Film digitizing to establish precise movement patterns at the instant of handle breakage.
4. Isokinetic and force plate testing to determine muscular force necessary to dislodge handles at various breaking points. Friction co-efficients of the feet against the floor were also obtained.
5. Bioanimation with anatomical dissolve to reveal the behaviour of underlying skeletal and muscular tissue, to provide detail of the action of L5 on S1, and the reaction of the nucleus pulposus to loading.

Conclusion
It was demonstrated that the herniation of the disc nucleus commenced during the initial pulling action prior to handle breakage. It would almost certainly have been exacerbated during the explosive asymmetrical muscular action at the instant of handle breakage. It was accepted that the repetitive action necessary at this workstation, and the cumulative impact at this spinal level over an extended period of time, rather than the impact of the fall, caused the injury. It was also accepted that his sport, employing a symmetrical and sustained muscular pull, was not to blame.