Biomaterial Database

Reinforcement of osteosynthesis screws with brushite cement. 1999

P Van Landuyt, and B Peter, and L Beluze, and J Lemaître

Department of Materials Science, Swiss Federal Institute of Technology, Lausanne. pascal.vanlanduyt@epfl.ch

The fixation of osteosynthesis screws remains a severe problem for fracture repair among osteoporotic patients. Polymethyl-methacrylate (PMMA) is routinely used to improve screw fixation, but this material has well-known drawbacks such as monomer toxicity, exothermic polymerization, and nonresorbability. Calcium phosphate cements have been developed for several years. Among these new bone substitution materials, brushite cements have the advantage of being injectable and resorbable. The aim of this study is to assess the reinforcement of osteosynthesis screws with brushite cement. Polyurethane foams, whose density is close to that of cancellous bone, were used as bone model. A hole was tapped in a foam sample, then brushite cement was injected. Trabecular osteosynthesis screws were inserted. After 24 h of aging in water, the stripping force was measured by a pull-out test. Screws (4.0 and 6.5 mm diameter) and two foam densities (0.14 and 0.28 g/cm3) were compared. Cements with varying solid/liquid ratios and xanthan contents were used in order to obtain the best screw reinforcement. During the pull-out test, the stripping force first increases to a maximum, then drops to a steady-state value until complete screw extraction. Both maximum force and plateau value increase drastically in the presence of cement. The highest stripping force is observed for 6.5-mm screws reinforced with cement in low-density foams. In this case, the stripping force is multiplied by 3.3 in the presence of cement. In a second experiment, cements with solid/liquid ratio ranging from 2.0 to 3.5 g/mL were used with 6.5-mm diameter screws. In some compositions, xanthan was added to improve injectability. The best results were obtained with 2.5 g/mL cement containing xanthan and with 3.0 g/mL cements without xanthan. A 0.9-kN maximal stripping force was observed with nonreinforced screws, while 1.9 kN was reached with reinforced screws. These first results are very promising regarding screw reinforcement with brushite cement. However, the polyurethane foam model presents noninterconnected porosity and physiological liquid was not modelized.

UI	MeSH Term	Description	Entries
D008422	Materials Testing	The testing of materials and devices, especially those used for PROSTHESES AND IMPLANTS; SUTURES; TISSUE ADHESIVES; etc., for hardness, strength, durability, safety, efficacy, and biocompatibility.	Biocompatibility Testing,Biocompatible Materials Testing,Hemocompatibility Testing,Testing, Biocompatible Materials,Testing, Hemocompatible Materials,Hemocompatibility Testings,Hemocompatible Materials Testing,Materials Testing, Biocompatible,Materials Testing, Hemocompatible,Testing, Biocompatibility,Testing, Hemocompatibility,Testing, Materials,Testings, Biocompatibility
D011140	Polyurethanes	A group of thermoplastic or thermosetting polymers containing polyisocyanate. They are used as ELASTOMERS, as coatings, as fibers and as foams.	Polyisocyanates,Ostamer,Pellethane,Spandex,Ostamers,Pellethanes,Polyisocyanate,Polyurethane,Spandices
D001843	Bone Cements	Adhesives used to fix prosthetic devices to bones and to cement bone to bone in difficult fractures. Synthetic resins are commonly used as cements. A mixture of monocalcium phosphate, monohydrate, alpha-tricalcium phosphate, and calcium carbonate with a sodium phosphate solution is also a useful bone paste.	Bone Cement,Bone Glues,Bone Pastes,Bone Glue,Bone Paste,Cement, Bone,Cements, Bone,Glue, Bone,Glues, Bone,Paste, Bone,Pastes, Bone
D001863	Bone Screws	Specialized devices used in ORTHOPEDIC SURGERY to repair bone fractures.	Bone Screw,Screw, Bone,Screws, Bone
D002130	Calcium Phosphates	Calcium salts of phosphoric acid. These compounds are frequently used as calcium supplements.	Phosphates, Calcium
D004868	Equipment Failure	Failure of equipment to perform to standard. The failure may be due to defects or improper use.	Defects, Equipment,Device Failure,Failure, Equipment,Malfunction, Equipment,Medical Device Failure,Misuse, Equipment,Device Failure, Medical,Device Failures, Medical,Failure, Medical Device,Failures, Medical Device,Defect, Equipment,Device Failures,Equipment Defect,Equipment Defects,Equipment Failures,Equipment Malfunction,Equipment Malfunctions,Equipment Misuse,Equipment Misuses,Failure, Device,Failures, Device,Failures, Equipment,Malfunctions, Equipment,Misuses, Equipment
D013718	Tensile Strength	The maximum stress a material subjected to a stretching load can withstand without tearing. (McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed, p2001)	Strength, Tensile,Strengths, Tensile,Tensile Strengths
D016062	Porosity	Condition of having pores or open spaces. This often refers to bones, bone implants, or bone cements, but can refer to the porous state of any solid substance.	Porosities
D019544	Equipment Failure Analysis	The evaluation of incidents involving the loss of function of a device. These evaluations are used for a variety of purposes such as to determine the failure rates, the causes of failures, costs of failures, and the reliability and maintainability of devices.	Materials Failure Analysis,Prosthesis Failure Analysis,Analysis, Equipment Failure,Analysis, Materials Failure,Analysis, Prosthesis Failure,Analyses, Equipment Failure,Analyses, Materials Failure,Analyses, Prosthesis Failure,Equipment Failure Analyses,Failure Analyses, Equipment,Failure Analyses, Materials,Failure Analyses, Prosthesis,Failure Analysis, Equipment,Failure Analysis, Materials,Failure Analysis, Prosthesis,Materials Failure Analyses,Prosthesis Failure Analyses