Processing and characterization of absorbable polylactide polymers for use in surgical implants

Abstract

Absorbable fibers of linear poly-alpha-hydroxy acids have been used successfully in providing temporary scaffolds for tissue regeneration. In some surgical applications, degradation rates for poly(glycolide) (PGA) are too high, but implants of poly(L-lactide) (PLLA) fibers may degrade too slowly for optimal function. Polymers produced by copolymerization of L-lactide with varying amounts of D-lactide may offer an alternative choice for absorbable fiber based implants. Poly(L/D-lactide) stereocopolymers with L/D lactide molar ratios of 95/5, 90/10, and 85/15 were considered. Melt-spun/hot-drawn fibers with L/D molar ratios of 90/10 and 85/15 and draw ratios ranging from 3.0 to 8.9 were further evaluated by mechanical testing, differential scanning calorimetry, birefringence, x-ray diffraction, and in vitro exposure to pH 7.4 phosphate buffered saline at 37 degrees C. Fabrication was reproducible and results indicated that tensile strength, modulus, an birefringence all increased with increasing draw ratio up to a draw ratio of 6.7 and declined thereafter; elongation to failure decreased for the entire range studied. For fibers with a draw ratio of 6.7, there was a 10% relative difference in crystallinity between the 90/10 and 85/15 lactide fibers (90/10 was higher). Wet strength retention after 12 weeks in vitro exposure was approximately 10% for the 90/10 fibers and 30% for the 85/15 fibers. The intermediate wet strength retention of lactide stereocopolymer fibers when compared to reported values for PGA and PLLA fibers, suggests these materials may be useful in absorbable surgical implants for tissue repair and regeneration.

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…Nonetheless, the most popular synthetic polymers used in medicine are the linear aliphatic poly(a-hydroxyesters) such as PLA, polyglycolic acid (PGA) and their copolymers-poly(lactic-co-glycolic) acid (PLGA) ( Table 4). These materials have been extensively studied; they appear to be the only synthetic and biodegradable polymers with an extensive FDA approval history [46,105,[121][122][123][124][125]. They are biocompatible, mostly non-inflammatory, as well as degrade in vivo through hydrolysis and possible enzymatic action into products that are removed from the body by regular metabolic pathways [45,100,105,[125][126][127][128][129][130].…”

Degradable polymeric materials for osteosynthesis: Tutorial

“…Self-reinforcement can be described as a moulding-extrusion process and consists in polymer fibres orientation into a matrix made of the same polymer (Tormälä et al, 1986;. The shaped devices can have initial strength close to metal ones (Tunc, 1991;Ashammakhi et al, 2004).…”

Early Experience with Biodegradable Implants in Pediatric Patients

“…Some of the earlier biodegradable implants caused problems because they typically were created from one type of polymer. Some degraded too quickly causing tissue reactions or they took too long to degrade offering no real advantages over metal [3,4,39]. In addition, biodegradable implants induce a nonsymptomatic but histopathologically recognizable tissue response that seems to be a phenomenon inherent in the degradation and absorption processes [32].…”