Biomechanical Evaluation of Promising Different Bone Substitutes in a Clinically Relevant Test Set-Up

Abstract

(1) Background: Bone substitutes are essential in orthopaedic surgery to fill up large bone defects. Thus, the aim of the study was to compare diverse bone fillers biomechanically to each other in a clinical-relevant test set-up and to detect differences in stability and handling for clinical use. (2) Methods: This study combined compressive strength tests and screw pullout-tests with dynamic tests of bone substitutes in a clinical-relevant biomechanical fracture model. Beyond well-established bone fillers (ChronOSTM Inject and Graftys® Quickset), two newly designed bone substitutes, a magnesium phosphate cement (MPC) and a drillable hydrogel reinforced calcium phosphate cement (CPC), were investigated. (3) Results: The drillable CPC revealed a comparable displacement of the fracture and maximum load to its commercial counterpart (Graftys® Quickset) in the clinically relevant biomechanical model, even though compressive strength and screw pullout force were higher using Graftys®. (4) Conclusions: The in-house-prepared cement allowed unproblematic drilling after replenishment without a negative influence on the stability. A new, promising bone substitute is the MPC, which showed the best overall results of all four cement types in the pure material tests (highest compressive strength and screw pullout force) as well as in the clinically relevant fracture model (lowest displacement and highest maximum load). The low viscosity enabled a very effective interdigitation to the spongiosa and a complete filling up of the defect, resulting in this demonstrated high stability. In conclusion, the two in-house-developed bone fillers revealed overall good results and are budding new developments for clinical use.

Cement-augmented screw fixation for calcaneal fracture treatment: a biomechanical study comparing two injectable bone substitutes

“…Twenty-seven synthetic bone specimens of the right calcaneus (LD 9118; Synbone, Zizers, Switzerland) were used in this study. Previous studies have proven that the biomechanical properties are similar between synthetic bone and human specimens, and our pre-tests confirmed these findings [10]. A four-part fracture (Sanders type IIA) was generated using an oscillating saw by a technique that has been proven reproducible in other studies [11].…”

“…Self-setting CP cements form an osteoconductive, degradable bone cement by a dissolution-reprecipitation process [15]. The Graftys® used in this study sets under a pH of > 4.2 and produces a slowly degrading hydroxyapatite, mimicking the composition and crystallinity of the inorganic phase of the bone matrix [10]. The mean compressive strength of Graftys® was 19.0 ± 2.5 MPa in our previous tests (manufacturer information: 24 MPa after 24 h) [10].…”

Development and Bone Regeneration Capacity of Premixed Magnesium Phosphate Cement Pastes

“…Magnesium substitution in CaP cements as well as pure MPC has captured increasing attention in bone graft research during the last few years [8]. This material group exhibits several features which are relevant for the application in clinical situations.…”

“…The amount of the latter was equal to the amount in a powder-liquid-approach using 3.5 M (NH 4 ) 2 HPO 4 solution and a powder to liquid ratio of 3 to 1. Prefabricated cement pastes were then obtained by mixing the powder components with an oil-surfactant mixture in the ratio of 5.25:1 as described elsewhere [8]. During the individual experiments the CaMgP cement pastes were applied using a 4:1 double chamber cartridge system (Medmix, Risch-Rotkreuz, Switzerland) with a connected static mixer.…”

“…This behavior was proofed in a number of animal studies with models ranging from small defects in rabbits [5,6] up to partial load-bearing tibial defects in sheep [7]. Additionally, magnesium phosphate cements (MPC) turned out to show very good biomechanical features, which are even better than clinically well-established calcium phosphate bone fillers [8]. Since most of the implanted magnesium phosphate minerals are hydrated species, their processing and in vivo application usually follows a cementitious route, in which the starting minerals are mixed with an aqueous solution to form a paste.…”