Unicortical Locking Screws Provide Comparable Rigidity to Bicortical Compression Screws in Clavicle Plate Fixation Constructs

Background: Clavicle fixation carries neurovascular injury risk. The purpose of this study was to compare bicortical compression and unicortical locked clavicle plate constructs biomechanically. Materials and Methods: Ten 4th-generation composite transverse mid-shaft clavicle osteotomy specimens were assigned to two groups, and each clavicle was fixed with an eight-hole 2nd generation 3.5 mm pelvic reconstruction plate placed superiorly. Group one in-cluded five fixed with bicortical compression screws and group two included five fixed with unicortical locking screws. All were tested on a 4-axis servohydraulic testing frame in three modes: axial rotation, anterior/posterior bending, and cephalad/caudad bending. Results: Mean construct stiffness for AP bending was 1.255 ± 0.058 Nm/deg (group 1) and 1.442 ± 0.065 Nm/deg (group 2); (p=0.001). Mean construct stiffness for axial rotation was 0.701 ± 0.08 Nm/deg (1) and 0.726 ± 0.03 Nm/deg (2); (p=0.581). Mean construct stiffness for cephalad bending was 0.889 ± 0.064 Nm/deg (1) and 0.880 ± 0.044 Nm/deg (2); (p=0.807). Mean construct stiffness for caudal bending was 2.523 ± 0.29 Nm/deg (1) and 2.774 ± 0.25 Nm/deg (2); (p=0.182). Conclusions: With transverse clavicle fractures, unicortical locking fixation provided comparable rigid-ity to bicortical compression fixation in axial rotation, cephalad bending, and caudal bending; it provided greater rigidity in AP bending.