Porous Threaded Titanium Implant Screws have Higher Insertional Torque Compared to Standard Screws

Purpose Posterior pelvic ring screw back out and loss of fixation may result from poor screw purchase, prevalent in geriatric pelvic ring injuries where the cancellous bone is often osteoporotic. To reduce screw back out, there has been increasing use of porous threaded titanium implant (PTTI) screws for posterior pelvic fixation rather than standard cannulated, buttress threaded screws. This study aims to assess the insertional torque of helical PTTI screws compared to standard cannulated screws as there is limited evidence regarding the biomechanical fixation profiles among screws.Methods Fifteen orthopaedic trauma surgeons inserted screws into a validated surrogate for osteoporotic cancellous bone. Insertional torque was measured during screw placement in three separate scenarios for each surgeon: (1) placement of a standard 7.3-millimeter (mm) screw into a new bone model, (2) placement of a PTTI screw into a new bone model, and (3) placement of a PTTI screw over a previously placed 7.3mm screw hole from which it was removed (rescue screw). The insertional torque was calculated across all surgeons and analyses were conducted comparing scenarios (1) and (2), and (1) and (3).Results The average insertional torque of 7.3mm screws was 0.358 ± 0.223 Nm and the maximum insertional torque was 0.627 ± 0.365 Nm. The average insertional torque for the PTTI screws was 0.929 ± 0.551 Nm, 2.59 times more than that of the 7.3mm screw (p < 0.001) while the maximum insertional torque was 1.877 ± 0.671 Nm, 2.99 times that of the standard screw (p < 0.001). When placed into the prior 7.3mm screw hole (rescue), the PTTI screws generated an average insertional torque of 0.711 ± 0.405, still 1.99 times greater than that of the 7.3mm screw (p < 0.001), and maximum torque of 1.607 ± 0.427 Nm, 2.56 times greater than the standard screw (p < 0.001).Conclusion Significantly greater maximum and average insertional torque were generated with the PTTI screws compared to the standard screws, even when used as a rescue screw in cancellous bone models. Further studies assessing clinical outcomes and failure rates with PTTI screws will better define their clinical utility.