1. From the University of Modena, Modena, Italy.
2. Researcher, Institute of Orthopaedics and Traumatology University of Modena. Address requests for reprints to Dott. Barca at Clinica Ortopedica Policlinico, Largo del Pozzo 70, 41100 Modena, Italy.
3. Institute of Orthopaedics and Traumatology, University of Modena.
4. Researcher, Chair, Department of Biometrix and Medical Statistics, University of Modena.