A comparative analysis of Socon CS and Socon pedicle screws in view of their use for treatment of osteoporotic fractures of the thoracolumbal spine--a biomechanical study

To compare the anchorage strength of Socon CS cannulated pedicle screws (B. Braun, Aesculap) with that of Socon screws in human cadaver vertebrae, using pull-out strength testing. Twelve samples involving T12 to L3 vertebrae were prepared and a total of 20 pedicle screws, 10 Socon CS and 10 Socon screws, were inserted in them. All screws were 55 mm in length and 6 mm in diameter. After placement, Socon CS pedicle screws were augmented with bone cement (Cimplant cement application kit, B. Braun, Aesculap). Both Socon CS and Socon screws were subjected to monotonous loading in the testing device ZWICK Z 020-TND with tensile stress applied in the screw axis. We evaluated the magnitude of strength resulting in screw loosening and the relationship between this strength and bone density of the sample. Bone density of measured samples corresponded either to osteopenia, i.e. T-score range of -1 to -2.5 SD (standard deviation) or osteoporosis, i.e. T-score -2.5 SD. The average bone density of all samples corresponded to a T-score of -3.1 SD. Bone-screw linkage was found to be associated with both bone-cement and screw-cement interface. Pull-out strength was significantly higher for the Socon CS than the Socon screws (t-test, p