Orthopaedic surgery has rapidly advanced in the past couple of centuries from amputation saws on mutilated limbs to altered forms of external splint ages and tractions, to technologically advanced precise internal fixation implants and devices that have permitted early mobilization and pain-free movements. Most of the emphasis in modern orthopaedic implant development is on designing devices that are strong, compatible to body fluids & tissues with optimum cost and life. In the past few decades, extensive research has been carried out and major improvements have been noticed in the development of bioabsorbable osteosynthetic devices. Biodegradable implants have brought in a paradigm from mechanical replacement (bionic engineering) to true biologic solutions to reconstructive problems.
With a host of bioabsorbable implants accessible in the market, awareness of the properties, uses and constraints of these devices should be known. We have tried to analyze the applicable world available literature on bioabsorbable implants and depict it with an orthopaedician’s view point.
Drawbacks of metallic implants
Metallic osteosynthetic implants have been widely used worldwide. However, there are inbuilt issues with the application of these metallic devices viz. pain, local irritation, stress shielding phenomenon etc. Risk of endogenous infection accompanies metallic implants. Metallic ions released by implants have long term implications, which are still to be discovered. It is therefore advisable to opt for implant removal after bone union which requires a second surgery.
In 1962, American Cyanamid Co. introduced fthe irst synthetic absorbable suture, developed from polyglycolic acid (PGA). Polygalactin 910 – a 90:10 copolymer of glycolide and lactide has been used as the competitive suture ‘Vicryl’ since 1976. Over several years of use of these synthetic absorbable sutures and experimental studies of their biocompatibility it has been reported that apart from a mild non-specific inflammation, it has no other allergic, toxic, carcinogenic, or other side effects.
Use of PGA in bone surgery for reinforcing pins, screws, and plates began in the late sixties. Thereafter, many developments in manufacturing biodegradable implants appropriate for osteosynthesis have come forth.
Many experimental studies have been undertaken to test the use of bioabsorbable implants in different animals and the results have been encouraging.
Form , strength and qualities
Polyglycolic acid (PGA) is a Sturdy, tough, crystalline polymer with an average molecular weight of 20,000 to 145,000 and a melting point of 224-230°C. Polylactic acid on the other hand is a polymer with initial molecular weights of 180,000 to 530,000 and a melting point of about 174°C. For orthopaedic implants, poly-L-lactic acid (PLLA) has been used more widely as it keeps its initial strength longer than poly-D-lactic acid (PDLA).
Implanted PGA screws have been reported to totally vanish within 6 months. PLLA, however, has a longer degradation time and are reported to remain in tissues for as long as 5 years post implantation.
For Orthopaedic implant application, the main challenge in developing bioabsorbable implants is having enough initial strength and sustaining this strength in the bone. This led to use of self reinforcing (SR) technique, whereby the material was sintered together at high temperature and pressure, resulting in primary strengths 5 to 10 times higher than those implants manufactured with melt moulding technique. Today , bio¬absorbable implants show no disparity in the stiffness, linear load & failure mode when co-related with metallic devices. There is many more ortho implant manufacturer in India and abroad. Siora Surgical Pvt Ltd is a well-known name in ortho implants manufacturing. The company has launched another website for Indonesian users www.siiora.co.id and the company has a parent website www.siiora.com, which can be accessed globally.