The Mechanical Benefit of Medial Support Screws in Locking Plating of Proximal Humerus Fractures

Abstract

BackgroundThe purpose of this study was to evaluate the biomechanical advantages of medial support screws (MSSs) in the locking proximal humeral plate for treating proximal humerus fractures.MethodsThirty synthetic left humeri were randomly divided into 3 subgroups to establish two-part surgical neck fracture models of proximal humerus. All fractures were fixed with a locking proximal humerus plate. Group A was fixed with medial cortical support and no MSSs; Group B was fixed with 3 MSSs but without medial cortical support; Group C was fixed with neither medial cortical support nor MSSs. Axial compression, torsional stiffness, shear stiffness, and failure tests were performed.ResultsConstructs with medial support from cortical bone showed statistically higher axial and shear stiffness than other subgroups examined (P<0.0001). When the proximal humerus was not supported by medial cortical bone, locking plating with medial support screws exhibited higher axial and torsional stiffness than locking plating without medial support screws (P≤0.0207). Specimens with medial cortical bone failed primarily by fracture of the humeral shaft or humeral head. Specimens without medial cortical bone support failed primarily by significant plate bending at the fracture site followed by humeral head collapse or humeral head fracture.ConclusionsAnatomic reduction with medial cortical support was the stiffest construct after a simulated two-part fracture. Significant biomechanical benefits of MSSs in locking plating of proximal humerus fractures were identified. The reconstruction of the medial column support for proximal humerus fractures helps to enhance mechanical stability of the humeral head and prevent implant failure.

Screw augmentation reduces motion at the bone-implant interface: a biomechanical study of locking plate fixation of proximal humeral fractures

“…The use of medial support screws has been advocated in cases of medial comminution. 1,6,20,21 Furthermore, the augmentation of head screws to compensate for low BMD has been shown to increase failure loads and stiffness after locking plate fixation of proximal humeral fractures. 5,10,14,16 Significant reductions in the complication rate with augmentation have yet to be proven.…”

Biomechanical evaluation of hybrid double plate osteosynthesis using a locking plate and an inverted third tubular plate for the treatment of proximal humeral fractures

“…The osteotomy was standardized with a fracture gap of 10 mm below the humeral neck. Group 1 was operated on with two additional medial support screws in accordance with the studies of Katthagen et al and Zhang et al ( Fig 2A ) [ 18 , 21 ]. Group 2 was treated using an additional plate osteosynthesis ( Fig 2B ).…”

“…The clinical implications of this biomechanical study largely relate to optimizing the treatment of proximal humerus fractures. In the given study, human cadaveric specimens were treated with calcar screws (group 1) or double-plate osteosynthesis (group 2), using a proximal humerus injury model with a two-part fracture as described previously [ 17 – 21 ]. The following hypotheses were investigated:…”

Experimental and Theoretical Validation of Double Column Internal Fixation Theory for Distal Femoral Fractures

“…Многочисленные публикации различных авторов подтверждают, что меди-альная стабильность при переломах метаэпи-физарных отделов длинных трубчатых костей конечностей играет важную роль в обеспечении общей стабильности остеосинтеза и является фактором, способствующим предотвращению развития несостоятельности имплантатов или их переломов. В частности, w. Zhang с соавто-рами и P. yang с соавторами пришли к выводу о том, что металлоконструкции, обеспечиваю-щие медиальную стабильность при переломах проксимального отдела плечевой кости, прояв-ляют лучшие биомеханические показатели по сравнению с пластинами без медиальной под-держки [25,26]. w.B.…”