<prompt> Denis classification is used to asses -Stability of spineDegree of calcium contentDegree of tumor invasionAmount of femur head subluxation in dysplastic hips  <response>: Ans. is a i.e., Stability of spine Denis Classification for Spinal stability: In assessing spinal stability, three structural elementsmust be considered:i The posterior osseoligamentouscomplex or posterior column consisting of thepedicles, facet joints, posterior bony arch, interspinousand supraspinous ligaments;ii The middle column comprising the posterior half of the vertebralbody, the posterior part of the intervertebral disc andthe posterior longitudinal ligament; andiii The anteriorcolumn composed of the anterior half of the vertebralbody, the anterior part of the intervertebral disc andthe anterior longitudinal ligament. Allfractures involving the middle column and at least oneother column should be regarded as unstable. Fortunately,only 10 per cent of spinal fractures are unstableand less than 5 per cent are associated with corddamage. 