Convened under the auspicious of esteemed endorsers - ISTA

amorphous and degrades faster in the body. However, the makeup of PLGA is typically random.The ratio of lactic to glycolic acid also affects the mechanical properties and degradation rate ofpolymer plastic. While PGA degrade faster than both poly (lactic) , the copolymer compositionof the plastics (PLGA) does not have a linear relationship to the degradation rate. Polyglycolidedegrades to glycolic acid and polylactide to lactic acid and eventually to pyruvic acid whichforms acetyl coA for a tricarboxylic acid cycle to yield energy and to form H2O and CO2.themain route for elimination is respiration but partly also through urine.In living tissue, the first hydrolytic scission occurs when PLGA exposed to H2O and oligomersand monomers are formed (Hollinger and Battistone, 1986). Histoiogically a capsule offibroblasts is first formed around the implant (seven days postimplantation); then a non-specificforeign-body reaction can be seen (large mononuclear cells, giant cells of mononuclear type,lymphocytes, few polymorphonuclear leucocytes). At 80 days post implantation, connectivetissue invades the screw, and phagocytic cells with polymeric debris can be seen. At 250 dayspostimplantation, the screw is biodegradated and replaced largely by connective tissue(Böstman et al. 1992c). In another study, at 36 weeks, approximately one third of the implantwas replaced by new trabecular bone, the major component being connective tissue, and thepolymeric debris had disappeared (Böstman et al. 1992a). Increased pH acceleratesdegradation of PGA (Chu 1981). The degradation time (hydrolysis) also depends on the initialmolecular weight, porosity, size, and shape of the implant (surface area/weight ratio)(Nakamura et al. 1989).Polyglycolic acid is immunologically inert, but it leads to slight non-specific lymphocyteactivation, as it induces inflammatory mononuclear cell migration (Santavirta et al. 1990).Non-specific inflammatory reactions in living tissue associated with the degradation of theimplant sometimes lead to a clinical complication, either to small fluid accumulation under theskin needing no treatment, or to painful fluid accumulation under the skin treated by aspirationwith a needle or to sterile sinus formation.Because semi-crystalline absorbable polymers such as PGA or PLLA degrade much faster inthe amorphous than in the crystalline phase, these polymers degrade inhomogenously losingmechanical strength as the amorphous phase degrades, followed by mass loss of slowlydegrading insoluble crystallites that may give rise to a tissue reaction, and possibly accumulatein the lymph nodes. Therefore, absorbable polymers with a low to moderate degree ofcrystallinity should be favored for medical applications.During Survey In literature there are some reports about sterile cyst formation following usingbioabsorbable screws in knee with granulation tissue reactionMethod:I report a case of an osteolytic tibial enlargement in association with a pretibial cyst formation8 months after successful anterior cruciate ligament reconstruction with 5 strand hamestringgraft and fixation with a PDLA interference screw. There was No joint inflammatory reaction,NO graft insufficiency, and NO functional problem. The operation was done in may 2008 withgood function in follow up , followed a cystic mass in entry of tibial tunnel in December , 2008 .The patient underwent cyst excision and curettage & bone graft of the tibial tunnelResult:2 months after the revision surgery, full recovery and return to pre injury level of activity wasachieved.Clinically there was no swelling or tenderness. Radiological evaluation showed bony healing.Conclusion:To my knowledge, the reported complication is a few obvious adverse reactions to a poly-D-L-file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]