1. Department of Orthopaedic Surgery, Cheju National University College of Medicine, Jeju, Korea.
2. Department of Orthopaedic Surgery, Chung-Ang University College of Medicine, Seoul, Korea.
3. Department of Preventive Medicine, Gyeongsang National University College of Medicine, Jinju, Korea.
4. Occupational Health Programme, World Health Organization European Centre for Environment and Health, Bonn, Germany.
5. Department of Orthopaedic Surgery, Kyungpook National University College of Medicine, Daegu, Korea.
6. Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul, Korea.