Intramedullary fixation of distal femoral diaphyseal osteotomies with absorbable self-reinforced poly-L-lactide and metallic intramedullary rods assessed by plain radiographs, quantitative computed tomography, and magnetic resonance imaging: An experimental study in rabbits

Abstract

Osteotomies of distal femoral diaphysis were fixed intramedullary with self-reinforced poly-L-lactide acid (SR-PLLA) rods in 19 and with metallic rods in 34 adult rabbits. The follow-up times were 8, 16, 24, and 48 weeks. Plain radiographs, computed tomography (CT), quantitative computed tomography (QCT), and magnetic resonance imaging (MRI) were used to evaluate the bone changes at two different levels of the osteotomy region. There were no significant differences in cortical bone density compared to the intact in the SR-PLLA fixed femurs at the osteotomy site. In the metallic-fixed femurs, the density values were significantly lower as compared to the contralateral femurs. There was a significant reduction of the cortical bone density values in SR-PLLA fixed femurs compared to the intact control side outside the osteotomy area at 8 (p = 0.01), at 16 (p = 0.0001), and at 24 weeks (p = 0.0003). In the metallic-fixed femurs significant reductions at 8 weeks (p = 0.02), at 16 weeks (p = 0.01), at 24 weeks (p = 0.009), and at 48 weeks (p = 0.002) were found compared with the intact control. MRI depicted well the SR-PLLA cases allowing studies without removal of the implant. On the contrary, abundant disturbing metallic artifacts were detected during investigation of the metallic-fixed femurs. In conclusion, our results indicated that CT is useful to evaluate the quality of reduction and internal fixation. Furthermore, the constant presence of internal metallic fixation seems to eventually cause osteoporosis in the cortical region of the femur. However, this stress protection effect of intramedullary fixation on the femoral diaphysis seems to be avoided by using an absorbable SR-PLLA rod, thus resulting in a better quality of bone when the osteotomies are healed.

Repair of Radial Fractures in Toy Breed Dogs with Self‐Reinforced Biodegradable Bone Plates, Metal Screws, and Light‐Weight External Coaptation

“…Implant‐induced osteoporosis has a multifactorial pathogenesis where early‐onset osteonecrosis is elicited mainly through cortical vascular insufficiency because of the original injury, open fracture fixation, and plate induced compression. However, later on, stress protection because of excessive rigidity of the metal implants in comparison with bone may contribute to development of osteoporosis 3,4,27 . Long‐term plate application of metal plates for fixation of radial fractures in dogs resulted in no significant differences in radial cortical bone density more than 1 year after plating between the plated radius and the contralateral radius in 14 dogs 28 .…”

“…Biodegradable implants provide adequate fixation during fracture healing and are absorbed slowly. The bending modulus of the implant is similar to cortical bone and stresses are gradually transferred to the healing bone during implant degradation, which diminishes the risk of osteoporosis and stimulates both bone growth and remodeling 3,4 . The self‐reinforced (SR) structure of biodegradable implants, where a matrix is reinforced by fibers of the same substance, has enabled production of devices that have initial strength values comparable with that of steel 5 .…”

Transplantation of a vascularized rabbit femoral diaphyseal segment: Mechanical and histologic properties of a new living bone transplantation model

“…Although the rabbit femur is well-established as a model for osteologic research, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] no study has made use of vascularized bone transplantation there. In addition, biomechanical data on vascularized bone transplantation in rabbits 26,27 and other animals [28][29][30] are scarce.…”

Influence of anionic monomer content on the biodegradation and toxicity of polyvinyl-urethane carbonate-ceramic interpenetrating phase composites

“…Self-reinforced polylactides (SR-PLLA) which contain oriented fibers of the same chemical composition, represent the currently used materials in the fabrication of biodegradable implants for fracture repair. They have been produced in an attempt to provide adequate initial stiffness and strength to the device [10][11][12]. To date, pins and screws made of SR-PLLA have been used in the fixation of ankle fractures [13], craniofacial fractures [14] and sub-capital femoral neck osteotomies [15].…”