[Analysis of degradation failure of poly L-lactic acid fixators used in meniscus tears].
OBJECTIVE
Biodegradable poly L-lactic acid (PLLA) fixators used in the repair of meniscal tears may cause adverse reactions inside the knee due to delayed degradation. This study was designed to determine the reasons for late degradation of PLLA fixators.


METHODS
Three unused and three used meniscal PLLA fixators (BioStinger) were analyzed. The latter were removed from three patients due to persisting symptoms within six months after knee arthroscopy. Fourier transform infrared (FTIR) spectroscopy was performed and external and internal surfaces of the samples were examined by scanning electron microscopy (SEM) and X-ray fluoroscopy (XRF). Chemical structural analyses of two samples (one from each group) were made by 1H-nuclear magnetic resonance (1H-NMR) spectroscopy. Degradation times of two samples (one from each group) by oxidative hydrolysis in hydrogen peroxide solution were recorded.


RESULTS
Chemical structure of used and unused fixators did not differ in FTIR analysis. With increasing temperatures, unused and used fixators showed degradation with and without melt flow, respectively. In SEM analysis, inner sections of unused fixators were homogeneous, whereas those of the used ones exhibited crystals which were found to be sodium and potassium chloride salts in XRF analysis. The 1H-NMR spectrum of used and unused samples showed the normal pattern of lactic acid polymer. The unused and used fixators degraded in hydrogen peroxide solution in 10 days and 30 days, respectively.


CONCLUSIONS
Both fixators had the same chemical structure in FTIR and NMR analyses. Formation of salt crystals seemed to be the most important cause of degradation failure, while changes in the physical properties of fixators were thought to be associated with delayed degradation.
Ceyhan
Taşkin
T
Department of Orthopedics and Traumatology, Special Cevre Hospital, Istanbul, Turkey. tceyhan@tnn.net
Aşik
Mehmet
M
Atalar
Ata Can
AC
Apohan
Nilhan Kayaman
NK
D020341:Absorbable Implants / Q000009:adverse effects; D001182:Arthroscopy; D001672:Biocompatible Materials / Q000009:adverse effects / Q000737:chemistry; D005471:Fluoroscopy / Q000379:methods; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects; D019344:Lactic Acid / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008592:Menisci, Tibial / Q000473:pathology / Q000601:surgery*; D008855:Microscopy, Electron, Scanning / Q000379:methods; D011091:Polyesters; D011108:Polymers / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D000070600:Tibial Meniscus Injuries; D016896:Treatment Outcome
D001672:Biocompatible Materials; D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide)