Plate fixation has recently gained popularity among the various surgical methods used to treat Neer type II distal clavicle fractures. The use of a low-profile distal clavicle locking plate is logically considered a better option when there is no significant difference in the fixation strength between insertions of 3.5- and 2.7-mm diameter screws. Therefore, the purpose of this biomechanical study was to investigate any differences in fixation strength among varying sizes of screws that are used to treat distal clavicle fractures. The study was performed with 20 paired shoulder girdles from 10 fresh frozen cadavers. To create a type IIA fracture of Neer classification, osteotomy was performed perpendicularly to the longitudinal axis of the clavicle at the medial end point of the conoid ligament. Two custom-made fixtures designed to be attached to both upper and lower sides of the Instron were fabricated for the evaluation. The mean maximum pull-out strength for fixation using 3.5-mm diameter screws was 241.9 ± 67.8 N, whereas the mean pull-out strength in fixation with 2.7-mm diameter screws was 228.1 ± 63.0 N. There was no statistically significant difference between the two groups. Distal fragment fixation with distal clavicle locking plates using two 2.7-mm diameter screws showed comparable biomechanical pull-out strength at the time-zero setting to fixations with a hook plate using two 3.5-mm diameter screws. Therefore, the fixation of the distal fragment with a low-profile plate and 2.7-mm screws may be preferred as an alternative option if the distal fragment of the fractured clavicle is not extremely small.
Keywords: distal clavicle; fracture; pull-out strength; screw diameter.
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