Can a coracoclavicular screw added to the clavicular hook plate reduce subacromial stress? A finite element analysis

The aim of this study was to investigate the stresses on the plate and the clavicle in the standard clavicular hook plate model and the clavicular hook plate models with a coracoclavicular (CC) screw by finite element analysis (FEA).

The FEA models were created with the combination of acromion, clavicle, coracoid process, 8-hole clavicular hook plate and screw components. Model 1 was created as a standard clavicular hook plate model and plates were implanted to the clavicle and the acromion by six locking screws. Model 2 was created by a cortical screw placed in the coracoid process through the third hole of the plate (CC screw) and fixation of hook plate by five locking screws. The upward-pull force was applied to clavicle at the insertion of sternocleidomastoid muscle with three axes. The stress exerted by acromion on the hook of the plate, stresses on the plate, clavicle, and CC screw were analyzed.

When the screw holes were compared, in Model 1, the highest stress was found in the last hole of the plate. In Model 2, the highest stress was detected on the CC screw. The stress on the clavicle was found to be 0.14 Mpa in Model 1 and 0.21 Mpa in Model 2. In Model 1 and Model 2, the stress exerted by acromion on the subacromial part of the plate was found to be 2.05 KPa and 1.66x10-6 KPa, respectively.

The results of this study show that addition of CC screw to the standard clavicular hook plate shares the loading and reduces the stress on the hook of the plate.