A Novel Bone-Screw-Fastener Demonstrates Greater Maximum Compression Force Prior to Failure Compared to a Traditional Buttress Screw.

Abstract

Objectives: This study compared the maximal compression force prior to thread stripping of the novel bone-screw-fastener (BSF) compared to the traditional-buttress-screw (TBS) in synthetic osteoporotic and cadaveric bone models. Methods: Maximum compression force of the plate-bone interface prior to loss of screw purchase during screw tightening was measured between self-tapping 3.5mm BSF and 3.5mm TBS using calibrated load cells. Three synthetic biomechanical models were used: a synthetic osteoporotic diaphysis (model 1); a 3-layer biomechanical polyurethane foam with 50-10-50 pounds-per-cubic-foot (PCF) layering (model 2), and a 3-layer polyurethane foam with 50-15-50 PCF layering (model 3). For the cadaveric metaphyseal model, three sets of cadaveric tibial plafonds and three sets of cadaveric tibial plateaus were used. A plate with sensors between the bone-plate interface was used to measure compression force during screw tightening in the synthetic bone models, while an annular load cell that measured screw compression as it slid through a guide was used to measure compression in the cadaver models. Results: Across all synthetic osteoporotic bone models, the BSF demonstrated greater maximal compression force prior to stripping compared to the TBS (model 1, 155.51N(SD=7.77N) vs 138.78N(SD=12.74N), p=0.036; model 2, 218.14N (SD=14.15N) vs 110.23N(SD=8.00N), p<0.001; model 3, 382.72N(SD=20.15) vs 341.09N(SD=15.57N), p=0.003. The BSF had greater maximal compression force for the overall cadaver trials, the tibial plafond trials, and the tibial plateau trials (overall, 111.27N vs 97.54N(SD 32.32N), p=0.002; plafond, 149.6N vs 132.92N(SD 31.32N), p=0.006; plateau 81.33N vs 69.89N(SD 33.38N), p=0.03. Conclusion: The novel bone-screw-fastener generated 11-65% greater maximal compression force than the traditional-buttress-screw in synthetic osteoporotic and cadaveric metaphyseal bone models. A greater compression force may increase construct stability, facilitate early weight bearing, and reduce construct failure.