The use of biodegradable implants in the fixation of small animal cancellous bone fractures

Surface and bulk modifications to photocrosslinked polyanhydrides to control degradation behavior

A unique class of surface-eroding polyanhydrides was developed and explored for use in medical applications requiring high-strength biomaterials (e.g., orthopedics). In particular, dimethacrylated anhydride monomers were synthesized that photopolymerize quickly to render densely crosslinked polymer networks that degrade from the surface only by hydrolysis of labile anhydride linkages. Previous research on these materials has shown that the rate of hydrolysis of the degradable linkages is dependent on the hydrophobicity of the network composition. This article demonstrates the versatility in controlling the degradation process and resulting cellular response in these materials through the incorporation of new chemistries and the formation of polymer-polymer composite structures. Specifically, the rate of mass loss was controlled by the addition of hydrophobic linear polymers [e.g., poly(methyl methacrylate)] or monovinyl monomers based on hydrophobic natural components (e.g., cholesterol, steric acid). In addition, a newly established photografting method was used to modify the network surface chemistry with cholesterol- and stearic acid-based polymer grafts to control the degradation front and cellular interactions at the polymer-tissue interface. Finally, a porogen leaching method was used to form porous polyanhydride constructs, which can be subsequently filled with osteoblasts photoencapsulated in a hydrogel, as potential synthetic allograft materials for tissue engineering bone.

Poly-L-lactic acid rod fixation results in foot surgery

The purpose of this study was to evaluate the effectiveness and possible complications of polylactic absorbable devices in surgical procedures involving fixation of the foot. This was a prospective study in which biodegradable rods of poly-L-lactide were used in the fixation of 41 metatarsal osteotomies and digital arthrodeses and one midtarsal fusion in 23 patients. The follow-up time ranged from 6 months to 23 months. Ages ranged from 18 to 70 years with a mean age of 42 years. Clinical and radiographic examination was scheduled for each patient postoperatively at 1 week, 3 weeks, 6 weeks, 3 months, 6 months, 1 year, and 2 years. The gender distribution was 18 female and 5 males. Two patients who had three procedures were lost to follow-up. All of the procedures were evaluated for failure of fixation, radiographic osteolysis, foreign-body reaction, sinus formation, and infection. We noted one failure of fixation and two complications unrelated to the type of fixation. There were no foreign-body reactions, sinus formulations, or infections. We conclude that the poly-L-lactic acid rod is a viable method of fixation for these procedures.

Biodegradable implants as intramedullary nails. A survey of recent studies and an introduction to their use

The high stiffness of metallic implants often requires a removal of the implant through a second operation, after fracture healing has occurred, to prevent disuse osteoporosis from occurring. An absorbable implant, lending sufficient strength and stiffness for support of the fracture during the healing period, would then gradually decay, and shift acting forces over to the healing bone. This paper presents a background to the development of such an implant of self-reinforced polylactic acid, and some recent results from different studies using these rod shaped implants for intramedullary nailing of both experimental and clinical fractures on animals. A short description of the operational technique for use of these implants is also given.

A histomorphological study on self-reinforced polyglycolide (SR-PGA) osteosynthesis implants coated with slowly absorbable polymers

A total of 150 osteotomies of rabbits' distal femur were fixed with absorbable self-reinforced polyglycolide (SR-PGA) rods coated with slowly absorbable polymers. In order to reduce the degradation rate of the SR-PGA construction rods were coated with n-butyl-2-cyanoacrylate, polydioxanone (PDS), poly-beta-hydroxybutyrate (PHBA), or poly-l-lactide (PLLA). Biocompatibility and the rate of biodegradation were evaluated in histological, histomorphometric, microradiographic, and oxytetracycline labeling studies. PDS, PHBA, and PLLA coatings showed good biocompatibility although there were scattered fluid accumulations around the rod in each group. Cyanoacrylate coating seemed to inhibit cartilage regeneration and cause the formation of considerable amount of connective tissue around the implant. The PGA core of the rod had totally degraded in 24 to 36 weeks in each coating group. Cyanoacrylate and PDS coatings were not detectable after 6 weeks while PHBA and PLLA coatings were still observed after 48 weeks. There were five (14%) non-unions in the cyanoacrylate coating group, one (3%) in the PHBA coating group caused by a purulent infection and none in the PDS and PLLA coating groups.

Fixation of cancellous bone and physeal fractures in dogs and cats. A comparison of the use of self-reinforced biodegradable devices to the use of metallic devices and external fixations

The use of self-reinforced biodegradable devices made of polyglycolide in the cancellous bone and physeal fractures of dogs and cats was compared to the use of metallic devices and external fixations on similar fractures. The series consisted of 64 dogs and 22 cats divided into 6 comparable groups. The patients in the 2 groups fixed with biodegradable devices started to use their operated limbs earlier than in the other groups. The same 2 groups also healed clinically (showed no lameness) earlier than the other groups. Radiographically there was no statistical difference between the 6 groups. On the basis of this study it may be concluded that the fixation with self-reinforced biodegradable devices is as suitable for the fixation of cancellous bone and physeal fractures of dogs and cats as the fixation with metallic devices or external fixation. This biodegradable technique has additional benefits allowing the patients to feel less pain in their operated limbs and making secondary operations to remove the devices unnecessary.

Fixation of cancellous bone and physeal fractures in dogs and cats. A comparison of the use of self-reinforced biodegradable devices to the use of metallic devices and external fixations

The use of self-reinforced biodegradable devices made of polyglycolide in the cancellous bone and physeal fractures of dogs and cats was compared to the use of metallic devices and external fixations on similar fractures. The series consisted of 64 dogs and 22 cats divided into 6 comparable groups. The patients in the 2 groups fixed with biodegradable devices started to use their operated limbs earlier than in the other groups. The same 2 groups also healed clinically (showed no lameness) earlier than the other groups. Radiographically there was no statistical difference between the 6 groups. On the basis of this study it may be concluded that the fixation with self-reinforced biodegradable devices is as suitable for the fixation of cancellous bone and physeal fractures of dogs and cats as the fixation with metallic devices or external fixation. This biodegradable technique has additional benefits allowing the patients to feel less pain in their operated limbs and making secondary operations to remove the devices unnecessary.

Biodegradable implants in the fixation of physeal fractures in cats and dogs

In a preclinical and a clinical study physeal fractures of cats and dogs were fixated with biodegradable implants. The preclinical part consisted of 4 cats with experimental physeal fractures of the distal femurs and the clinical part of 6 cats and 8 dogs with different physeal fractures. All fractures were fixated with selfreinforced polyglycolic acid (PGA) implants of different sizes. No external support was applied after the fixation. All cats and dogs used their operated legs during the first postoperative week and they could walk without lameness in 6 weeks. The fracture healed without delay or malformations. The retardations of the growth of the physeal regions were considered minimal.