The instability of wrist joint and total wrist replacement.

Total wrist arthroplasty are not used as widely as total knee and hip replacement. The functional hands are requiring surgeons to design a durable and functional satisfying prosthesis. This article will list the main reasons that cause the failure of the prosthesis. Some remarkable and representative prostheses are listed to show the devolvement of total wrist prosthesis and their individual special innovations to fix the problems. And the second part we will discuss the part that biomechanical elements act in the total wrist replacement (TWA). Summarize and find out what the real problem is and how we can find a way to fix it.

[Method development for analysis of short-and long-chain perfluorocarboxylates in sewage].

A method using weak anion exchange cartridge for solid phase extraction before high performance liquid chromatography-negative electronspray ionization-tandem mass spectrometry [WAX-SPE + HPLC-ESI(-)-MS/MS] detection has been developed to measure C2-C14 perfluorocarboxylates (PFCAs) in sewages. When the weak anion exchange (WAX) cartridges were used for solid phase extraction (SPE), the better recoveries of short- and long-chain PFCAs (C2-C14) were achieved as the sewage samples were acidified to pH = 3.0 by formic acid, 2% formic acid was used for washing solvent and 1% ammonium hydroxide in methanol was used for elution solvent. The WAX cartridges used for SPE overcame the disadvantages of reverse phase solid phase extraction cartridges, i.e. the recoveries of short-chain PFCAs (C2-C5) were very low. The validity of this method was demonstrated by determination of short- and long-chain PFCAs (C2-C14) in influent of municipal wastewater treatment plant A and B in Shanghai, China. The results indicate that the recoveries of all PFCAs in influent of plant A and B are 56%-121% and 54%-120%, respectively; the recovery relative standard deviations (RSD) of plant A and B are < 11% and < 14%, respectively; and the method detection limits (MDL) and method quantitation limits (MQL) are 0.2-1.0 ng/L and 1.0-5.0 ng/L, respectively. In addition, the perfluorooctanoate (743 ng/L and 837 ng/L, respectively) and trifluoroacetic acid (139 ng/L and 489 ng/L, respectively) are the most and the second most PFCAs found in both plant A and B.