Polyethylene in knee arthroplasty: A review

Polyethylene (PE) has been used extensively in knee arthroplasty since the mid 20th century. Progress in material manufacturing and processing has led to newer polyethylenes over last few decades with different material properties. It has been established that PE wear in knee arthroplasty causes particle induced osteolysis which is the main reason for late failure and requires revision surgery. Although there are various causes of wear, the properties of PE have long been a matter of investigation as a contributory factor. The advent of newer highly cross linked PE has been shown to improve wear rates in hip arthroplasty but the benefits have not been shown to be of the same degree in knee arthroplasty. The laboratory and clinical studies so far are limited and slightly conflicting in their conclusions. The risks of using highly cross linked PE in knee arthroplasty include tibial post fracture, disruption of locking mechanism, liner fracture which can lead to increased wear and osteolysis. The current evidence suggests that highly cross linked polyethylenes should be used with caution and only considered in younger active patients. The results of a recently completed randomized trial to compare the conventional with high molecular weight PE in knee arthroplasty are awaited.     

Metastatic parathyroid carcinoma treated with radiofrequency ablation: A novel therapeutic modality

Parathyroid carcinoma (PCA), accounting for less than one per cent of all endocrine malignancies, is a rare cause of primary hyperparathyroidism. A diagnosis of parathyroid carcinoma may be challenging in the presence of localised disease and involves a histological diagnosis based on capsular, vascular, or perineural invasion or the presence of metastasis. Distant metastasis remains a rare presentation, with the lung being the most common site. Surgery remains the treatment of choice as radiotherapy and chemotherapy have proved to be of limited benefit in metastatic disease. This case reports suggests that radiofrequency ablation has the potential to be a novel and effective treatment option in these patients.     

Initial experience with a self-expanding retrievable stent for recanalization of large vessel occlusions in acute ischemic stroke

Introduction  

Quicker recanalization results in better clinical outcomes in patients with acute ischemic strokes. We describe our experience with the use of a self-expanding, fully retrievable stent in acute intracranial occlusions.     

Perception of cancer recurrence risk: More information is better

Objective

Breast cancer is the most common cancer among women worldwide. Given the advances in extending survival, the number of recently diagnosed breast cancer patients and longer-term breast cancer survivors is growing. The goals of this study were to better understand (1) perceptions of provider cancer recurrence risk communication, (2) perceived risk of breast cancer recurrence in cancer patients and survivors, and (3) accuracy of perceived risk.

Methods

A survey was conducted on women with a prior breast cancer (n = 141).

Results

Approximately 40% of women perceived that providers had not talked about their breast cancer recurrence risk; although only 1 person reported not wanting a physician to talk to her about her risk. Women were largely inaccurate in their assessments of risk. Greater worry, living in a rural area, and longer time since diagnosis were associated with greater inaccuracy. Women tended to think about distal recurrence of cancer as often of local recurrence.

Conclusions

Perceived risk of breast cancer recurrence was inaccurate, and patients desired more communication about recurrence risk.

Practice implications

Consistent with findings from other studies, greater efforts are needed to improve the communication of cancer recurrence risk to patients. Attention should be paid to those from rural areas and to distal cancer recurrence in women with a previous history of breast cancer.     

Role of N-vinyl-2-pyrrolidinone on the thermoresponsive behavior of PNIPAm hydrogel and its release kinetics using dye and vitamin-B12 as model drug

Temperature-sensitive hydrogels hold great promise in biological applications as they can respond to changes in physiological temperature to produce a desired effect like controlled drug delivery. In this study, a series of poly(N-isopropylacrylamide-co-N-vinyl-2-pyrrolidinone) thermosensitive hydrogels were synthesized by radical copolymerization of NIPAm with 1-vinyl-2-pyrrolidinone (NVP). By altering the initial NIPAm/NVP mole ratios, copolymers were synthesized to have their own distinctive lower critical solution temperature which was established using differential scanning calorimetry. The swelling behavior of the hydrogel was analyzed gravimetrically and it was observed that reswelling rate increases with increasing NVP mole ratio. Further characterizations of the hydrogels were performed using Fourier transform infrared spectroscopy and scanning electron microscopy. Release kinetics with respect to temperature was studied using methylene blue dye solution and vitamin B12. Kinetic modeling of the release profile revealed that the release mechanism is a non-Fickian diffusion mechanism. These results suggested that this material has potential application as intelligent drug carriers. The quantities of residual monomers in the PIV4 hydrogel were determined by HPLC method, and the results show almost complete conversion.     

Polymeric micelle nanocarriers for targeted epidermal delivery of the hedgehog pathway inhibitor vismodegib: formulation development and cutaneous biodistribution in human skin

Background: The aim was to investigate cutaneous delivery and biodistribution of the hedgehog pathway inhibitor, vismodegib (VSD), indicated for basal cell carcinoma (BCC), from polymeric micelle formulations under infinite/finite dose conditions.

Methods: VSD-loaded micelles were characterized for drug content, particle size, and shape; a micelle gel was characterized for its rheological behavior. Cutaneous deposition and biodistribution of VSD were determined using porcine and human skin in vitro with quantification by UHPLC-MS/MS.

Results: The optimal micelle solution (Z_av 20–30 nm) increased the aqueous solubility of VSD by >8000-fold; drug content was stable after 4 weeks at 4°C. Application of micelle solution and micelle gel (0.086% w/v) to human skin for 12 h under infinite dose conditions resulted in statistically equivalent VSD deposition (0.62 ± 0.11 and 0.67 ± 0.14 μg/cm², respectively). Cutaneous biodistribution in human skin under infinite (micelle solution and gel) and finite (micelle gel) dose conditions showed that the VSD concentrations obtained in the basal epidermis, at depths of 120–200 μm, were ?3800- and ?2300-fold greater than the IC₅₀ reported for hedgehog signaling pathway inhibition in vitro.

Conclusion: Cutaneous delivery of VSD from micelle-based formulations might enable targeted, topical treatment of superficial BCC with minimal risk of systemic exposure.