BIOMECHANICAL EVALUATION OF SUBCORTICAL VERSUS BICORTICAL SCREW PURCHASE IN ANTERIOR CERVICAL PLATING

The purpose of this in vitro study is to compare the stabilities provi ded by anterior cervical H-plating with screws purchased either subcor tically or bicortically on porcine cervical spines. Nine porcine cervi cal spines (C3-C4) were challenged by 12 Nm in extension followed by 6 Nm in flexion in 6 consecutive steps, i.e., (1) when disc was intact, (2) after discectomy. Subsequently, a tricortical bone graft was inse rted to simulate interbody fusion. Each specimen was tested again (3) when plated with 16 mm screws to purchase subcortically and (4) after cyclic loading (f = 0.5 Hz, n = 1000), (5) when plated with 30 mm scre ws to pur chase bicortically and (6) after cyclic loading. Neutral zon e and range of motion were parameters normalized for comparison. The r esults showed comparable stability in constructs plated with screws pu rchased either subcortically or bicortically before cyclic loading. Cy clic loading deteriorated construct-bone relation in both groups, yet bicortically purchased screws rendered additional stability in anterio r cervical plating.