Bioresorbable Pins Research Articles

A Biomimetic Artificial Disc with Improved Mechanical Properties Compared to Biological Intervertebral Discs

AbstractPatients with serious spinal disc disorders will benefit from a novel artificial disc system that is suitable for clinical use in replacement arthroplasty. The disc is composed of a biomimetic three‐dimensional (3D) fabric with a triaxial fiber alignment that has superior mechanical properties when compared to conventional implants. This disc improves on the constitutional imperfections of biological intervertebral discs by eliminating the risk of rupture and delamination. The fabric bonds firmly to disc bodies, and functions in combination with bioactive bioresorbable pins and scaffolds as a stand‐alone system that maintains the position of the disc and promotes bone growth at the interface. The disc has high biocompatibility and can maintain biomimetic “J‐shaped” stress–strain behavior for up to sixty‐three million alternating stresses, which is the equivalent of natural biological movements for a period of more than 30 years. This technology exemplifies how, in the best biomaterials, biological flexibility may occasionally overcome artificial rigidity.

New bioresorbable pin for the reduction of small bony fragments: design, mechanical properties and in vitro degradation

The design, material properties, and in vivo degradation characteristics of a new resorbable pin for the reductions of small bony fragments are described. The Polypin ®, made of 70:30 poly( L, DL-lactide), had an initial bending strength of 155–163 MPa, as measured by a three-point bending test. Ethylene oxide (EO)- and gamma-sterilization did not substantially affect its initial mechanical properties. The initial molecular weight ( M w ) of 523,000 to 600,000, however, decreased 60–75% after gamma-sterilization. Incubation of the EO-sterilized pins in 37 °C saline solution produced a complete loss of bending strength at 18 months. An accelerated test at 70 °C led to a complete loss of strength after only 96 h. Degradation of the gamma-sterilized pin at 70 °C was about 30% faster than that of the EO-sterilized pin. Bending strength and molecular weight were unaffected by storage at room temperature for 46 months. The relatively slow strength loss rate of the Polypin ® potentially extends the application of resorbable devices to slow-healing fractures. The new pin design allows application of light interfragmentary compression, thus reducing the risk of pin loosening, and an X-ray marker is provided.

Bioresorbable Pins and Screws in Paediatric Traumatology

Bioresorbable implants are suited to the treatment of joint and shaft fractures in children. These conclusions were drawn from clinical and experimental investigations at the University of Heidelberg. Since 1990 13 fractures, including 5 medial malleolus fractures, 2 retropatella flake fractures, 1 metacarpal fracture, 2 lateral condyle, 2 epicondyle fractures and a secondary dislocated forearm fracture were treated with BIOFIX pins. 11 of these cases were without complications. There was one case of infection, and due to material failure the stability was insufficient in one case. In a post-mortem study torsional fractures were produced in femora of children between 5 and 15 months. The fractures were then fixed with one resorbable screw and put under torsional loading until the bone refractured. The post-fixation force (torsional) amounted to 77% of the original fracture force, and the degree of rotation at fracture was post-fixation 84% of the original. The stability of bioresorbable screws in the treatment of femoral spiral fractures in children can therefore be confirmed.