Biomechanical analysis of plate systems for proximal humerus fractures: a systematic literature review

Abstract

BackgroundProximal humerus fractures are the third most common in the human body but their management remains controversial. Open reduction and internal fixation with plates is one of the leading modes of operative treatment for these fractures. The development of technologies and techniques for these plates, during the recent decades, promise a bright future for their clinical use. A comprehensive review of in vitro biomechanical studies is needed for the comparison of plates’ mechanical performance and the testing methodologies. This will not only guide clinicians with plate selection but also with the design of future in vitro biomechanical studies. This review was aimed to systematically categorise and review the in vitro biomechanical studies of these plates based on their protocols and discuss their results. The technologies and techniques investigated in these studies were categorised and compared to reach a census where possible.Methods and resultsWeb of Science and Scopus database search yielded 62 studies. Out of these, 51 performed axial loading, torsion, bending and/or combined bending and axial loading while 11 simulated complex glenohumeral movements by using tendons. Loading conditions and set-up, failure criteria and performance parameters, as well as results for each study, were reviewed. Only two studies tested four-part fracture model while the rest investigated two- and three-part fractures. In ten studies, synthetic humeri were tested instead of cadaveric ones. In addition to load–displacement data, three-dimensional motion analysis systems, digital image correlation and acoustic emission testing have been used for measurement.ConclusionsOverall, PHILOS was the most tested plate and locking plates demonstrated better mechanical performance than non-locking ones. Conflicting results have been published for their comparison with non-locking blade plates and polyaxial locking screws. Augmentation with cement [calcium phosphate or poly(methyl methacrylate)] or allografts (fibular and femoral head) was found to improve bone-plate constructs’ mechanical performance. Controversy still lies over the use of rigid and semi-rigid implants and the insertion of inferomedial screws for calcar region support. This review will guide the design of in vitro and in silico biomechanical tests and also supplement the study of clinical literature.Electronic supplementary materialThe online version of this article (10.1186/s12938-018-0479-3) contains supplementary material, which is available to authorized users.

Biomechanics of Upper Extremity Double Plating

“…The various plate systems designed for the proximal humerus have been compared in numerous biomechanical studies which showed the superiority of locking implants over conventional implants [24]. In a study by Hessmann et al, using a 3-part fracture model with 8 formalin-fixed human humerus pairs, DP with a laterally placed and a second anteriorly placed third-tubular plate was compared to the locking PHILOS plate [25].…”

Winkelstabile Plattenosteosynthese

“…Ein Großteil der Humeruskopffrakturen findet im höheren Patientenalter statt und ist mit geringerer Knochendichte verbunden; winkelstabile Plattenosteosynthesen mit vorgeformten Implantaten, wie beispielsweise das von der AO zugelassene Proximal Humeral Internal Locking System (PHILOS, Firma Synthes), haben hier in biomechanischen Testungen eine deutliche Überlegenheit nicht winkelstabilen Implantaten gegenüber gezeigt. Je nach Frakturmorphologie und Knochenqualität ist zusätzlich eine Augmentation der Schrauben mit Zement möglich oder die zusätzliche Implantation eines Allografts zur Wiederherstellung einer medialen kortikalen Abstützung [15] (▶ Abb. 5).…”

Cement augmentation of calcar screws may provide the greatest reduction in predicted screw cut-out risk for proximal humerus plating based on validated parametric computational modelling

“…Numerous in vitro biomechanical studies have demonstrated enhanced primary stability of proximal humerus plating with cement-augmented screws. 9 , 12 However, the clinical findings have been controversial regarding the benefit of bone cement augmentation with the proximal humerus internal locking system (PHILOS; DePuy Synthes, Zuchwil, Switzerland). 13 - 15 These variable results may be related to heterogenicity of augmentation techniques and the screw configurations used.…”