Biomechanical evaluation of different screw fixation methods for Ogawa type I coracoid process base fracture

Background The internal fixation of Ogawa type I coracoid fractures is relatively difficult, and there is no consensus on the fixation method, which is also prone to screw cutout. This study aims to evaluate the biomechanical properties of 5 different screw internal fixation methods for Ogawa type I coracoid process base fracture through biomechanical experiments. Hypothesis The biomechanical effects of the 5 fixation methods are different. Methods Fifteen fresh adult scapula specimens were randomly selected to create models of Ogawa type I coracoid process base fracture. Five fixation methods were used: single hollow screw fixation entirely within the bone (M1), single hollow screw fixation partially exiting below the vertical part of the coracoid process (M2), single hollow screw fixation partially exiting above the vertical part of the coracoid process and extending to the scapular spine (M3), dual hollow screw fixation entirely within the bone (M4), and dual hollow screw fixation combining M1+M3 (M5). All specimens were randomly divided into 5 groups of 3, each corresponding to a fixation method. Biomechanical experiments of compression, tension, and rotation were conducted to assess the stability of each fixation method. Results There was no significant difference in bone mineral density among the groups ( P = .873). At the compression end point, M2 sustained the lowest force and M4 the highest, with the ranking M2 < M3 < M1 < M5 < M4; the intergroup difference was statistically significant ( P = .022). At the tension end point, M3 sustained the lowest force and M5 the highest, with the ranking M3 < M2 < M1 < M4 < M5; the intergroup difference was statistically significant ( P = .019). At the torsion end point, M2 showed the lowest torque and M5 the highest, with the ranking M2 < M3 < M1 < M4 < M5; the intergroup difference was statistically significant ( P = .032). Conclusion The dual-screw fixation methods (M4 and M5) demonstrated the best stability in treating Ogawa type I coracoid process base fracture, with no significant difference between M5 and M4. For single-screw fixation, the entirely intraosseous method (M1) was more stable than the "in-out-in" methods, and the mode with partial downward exit (M2) should be avoided.