No abstract

As part of ongoing studies in polyurethane biostability and biodegradation, we have investigated an in vitro system to test strained poly(etherurethane urea) (PEUU). Recently, we utilized this system to reproduce in vivo stress cracking in strained Pellethane. In this study, strained PEUU was tested to determine whether it degrades through a common mechanism with Pellethane and to further examine the steps involved in this degradation. Biaxially strained PEUU elastomers were treated with an alpha 2-macroglobulin (alpha 2-Mac) protein solution followed by an oxidative H2O2/CoCl2 treatment. Characterization of the strained PEUU specimens was performed with attenuated total reflectance-Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), electron spectroscopy for chemical analysis, and contact angle analysis. The results from these characterization techniques provide conclusive evidence that biodegradation of PEUU and Pellethane occurs through a common mechanism. Chemical changes to the PEUU include cleavage of the polyether soft segments and urethane linkages, leaving the hard segment domains unaffected. SEM analysis shows that this chain cleavage leads to the development of severe pitting and cracking of the PEUU surface. In addition, the in vitro degradation accurately reproduces the in vivo degradation chemically and physically. This result verifies that the primary species responsible for biodegradation of PEUUs, in vivo, are hydroxyl and/or hydroperoxide radicals. alpha 2-Mac pretreatment increases the rate of degradation compared to direct treatment in H2O2/CoCl2. As the PEUU soft segment chains are cleaved, the degradation products are extracted into the treatment solution or environment. Finally, a new biodegradation mechanism of PEUUs is presented that involves crosslinking of the polyether soft segments.

Recent research in psychosocial oncology has pointed to the traumatic nature of the stress experienced by cancer survivors. Most of this research has focused on children, young adults survivors and their families. This investigation proposes a conceptual model for understanding general psychological distress (anxiety, hostility and depression) and symptoms of posttraumatic stress (hyper-arousal, avoidance and intrusiveness) that may be associated with cancer survivorship among older adults. Findings from a survey of 180 older adult, long-term cancer survivors are used to illustrate the key features of this model. Results of multivariate analysis show that most older adult long-term cancer survivors do not demonstrate clinical levels of posttraumatic stress disorder (PTSD), although over 25% evidence clinical levels of depression. However, many survivors display important symptoms of psychological distress that are related to the continuing effects of cancer and its treatment. Current cancer-related symptoms are the strongest predictors of depression (beta=0.27, p=0.046) and the PTSD sub-dimension of hyper-arousal (beta=0.377, p=0.004). These effects persist even when the effects of other stressors and non-cancer illness symptoms are statistically controlled. Additionally, it appears in this sample that symptoms of PTSD are significantly correlated with traditional measures of psychological distress.

Fluoroscopically guided epidural steroid injections are a safe and well-tolerated intervention for cervical or lumbar pain and radiculopathy. Minor complications are uncommon, and most involve increases in pain. Transforaminal injections may result in fewer minor complications than interlaminar injections.

No abstract