Validation of Clinical Assessment of Spinal Stiffness

"The clinical stiffness tests will be applied twice to the same patient by the same operator to verify intra-operator variability and twice by two operators at the same time to verify inter-operator variability.~The verification of diagnostic accuracy with respect to the radiographic reference standard will be carried out retrospectively by using the data already available and systematically collected in electronic format during medical visits and physiotherapy sessions."