Mapping of Texture and Phase Fractions in Heterogeneous Stress States during Multiaxial Loading of Biomedical Superelastic NiTi.

Thermoelastic deformation mechanisms in polycrystalline biomedical-grade superelastic NiTi are spatially mapped using in situ neutron diffraction during multiaxial loading and heating. The trigonal R-phase is formed from the cubic phase during cooling to room temperature and subsequently deforms in compression, tension, and torsion. The resulting R-phase variant microstructure from the variant reorientation and detwinning processes are equivalent for the corresponding strain in tension and compression, and the variant microstructure is reversible by isothermal loading. The R-phase variant microstructure is consistent between uniaxial and torsional loading when the principal stress directions of the stress state are considered (for the crystallographic directions observed here). The variant microstructure evolution is tracked and the similarity in general behavior between uniaxial and torsional loading, in spite of the implicit heterogeneous stress state associated with torsional loading, pointed to the ability of the reversible thermoelastic transformation in NiTi to accommodate stress and strain mismatch with deformation. This ability of the R-phase, despite its limited variants, to accommodate stress and strain and satisfy strain incompatibility in addition to the existing internal stresses has significance for reducing irrecoverable deformation mechanisms during loading and cycling through the phase transformation.

Safety and efficacy of extended-release bupivacaine local anaesthetic in open hernia repair: a randomized controlled trial.

BACKGROUND: Pain relief remains a major problem in hernia surgery. SABER-Bupivacaine is an investigational extended-release formulation of bupivacaine in a resorbable matrix, which may provide up to 72 h of local pain relief. METHODS: A double-blinded, randomized controlled trial was undertaken to evaluate the safety and efficacy of SABER-Bupivacaine. Consented patients (n = 124) undergoing open inguinal hernia repair at five sites in Australia and New Zealand were randomized to receive either 2.5 (330 mg) or 5.0 mL (660 mg) of SABER-Bupivacaine or SABER-Placebo administered to the surgical wound at the end of the procedure. Analgesic efficacy and safety was evaluated. RESULTS: SABER-Bupivacaine appeared safe with no difference in the incidence of side effects compared with SABER-Placebo. The 5.0 mL dose of SABER-Bupivacaine reduced the mean area under the curve of pain intensity on movement compared with SABER-Placebo (2.47 versus 3.60; P = 0.0033) and decreased the number of patients requiring supplemental opioids by 26% (although not statistically significant; P = 0.0909). Normal wound healing was reported throughout the trial and at 3- and 6-month follow-up in every treatment group. CONCLUSION: After open inguinal hernia repair, SABER-Bupivacaine administered at the surgical site was safe and provided pain relief, reduced the need for supplemental (oral and parenteral) analgesia and did not impair wound healing.