Double plating is associated with higher fixation strength than single plating in osteoporotic fractures of the scapular spine: a biomechanical study

Abstract

Introduction The number of atraumatic stress fractures of the scapular spine associated with reverse shoulder arthroplasty is increasing. At present, there is no consensus regarding the optimal treatment strategy. Due to the already weakened bone, fractures of the scapular spine require a high fixation stability. Higher fixation strength may be achieved by double plating. The aim of this study was to evaluate the biomechanical principles of double plating in comparison to single plating for scapular spine fractures. Methods In this study, eight pairs (n = 16) of human shoulders were randomised pairwise into two groups. After an osteotomy at the level of the spinoglenoid notch, one side of each pair received fracture fixation with a single 3.5 LCP (Locking Compression Plate) plate. The contralateral scapular spine was fixed with a 3.5 LCP and an additional 2.7 LCP plate in 90–90 configuration. The biomechanical test protocol consisted of 700 cycles of dynamic loading and a load-to-failure test with a servohydraulic testing machine. Failure was defined as macroscopic catastrophic failure (screw cut-out, plate breakage). The focus was set on the results of specimens with osteoporotic bone quality. Results In specimens with an osteoporotic bone mineral density (BMD; n = 12), the mean failure load was significantly higher for the double plate group compared to single plating (471 N vs. 328 N; p = 0.029). Analysis of all specimens (n = 16) including four specimens without osteoporotic BMD revealed no significant differences regarding stiffness and failure load (p > 0.05). Conclusion Double plating may provide higher fixation strength in osteoporotic bone in comparison to a single plate alone. This finding is of particular relevance for fixation of scapular spine fractures following reverse shoulder arthroplasty. Level of evidence Controlled laboratory study.

Single or Double Plating for Acromial Type III Fractures: Biomechanical Comparison of Load to Failure and Fragment Motion

“…In a study by Katthagen and colleagues, a similar LCP double plating approach was already investigated; however, their study differs from the present one in the type and dimension of plates used and the type and direction of the load (elevation instead of abduction of the arm). In their study, the double plating approach performed better than the single-plating approach in terms of failure load [ 15 , 18 , 20 ], which is consistent with the results of this study. From the combined view of Katthagen et al [ 15 , 18 , 20 ] and our study, we conclude that double plating is preferable from a biomechanical point of view in terms of failure load, stiffness, and fragment movements compared to a single-plating approach.…”

“…In their study, the double plating approach performed better than the single-plating approach in terms of failure load [ 15 , 18 , 20 ], which is consistent with the results of this study. From the combined view of Katthagen et al [ 15 , 18 , 20 ] and our study, we conclude that double plating is preferable from a biomechanical point of view in terms of failure load, stiffness, and fragment movements compared to a single-plating approach.…”

“…Although there is already a study that has investigated a double plate trial [ 20 ], our results complement this study, as we investigated a different movement of the arm, a more physiological positioning of the scapula, and also a cyclic movement to failure of the constructs. In addition, our study provides information about fragment movements in the direction of the muscle pull of the deltoid muscle.…”

“…Thus, the results of our study are more meaningful than those of other studies. Other studies mainly focused on testing the elevation of the arm [ 15 , 18 , 20 ], whereas our study is the first to test plate–bone constructs in a 40° abduction setting, enriching the biomechanical perspective of this fracture treatment.…”

“…In addition, our study provides information about fragment movements in the direction of the muscle pull of the deltoid muscle. Furthermore, our study investigated the comparison of the double-plate approach and additionally two single-plate constructs; this was not the case in other studies [ 15 , 18 , 20 ].…”