Unicortical Locking Screws Provide Comparable Rigidity to Bicortical Compression Screws in Tranverse Mid-Shaft Clavicle Fracture Plate Fixation Constructs

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