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Background While hemiarthroplasty (HA) is considered the treatment of choice for displaced femoral neck (FN) fractures in elderly patients, HA has been partly performed as an alternative treatment option for unstable intertrochanteric (IT) fractures. However, there is a paucity of data regarding the risk and availability of HA for unstable IT fractures compared to HA for displaced FN fractures in elderly patients. Therefore, we performed this case-control study to determine whether HA for unstable IT fractures provides clinical results and survival comparable to HA for displaced FN fractures in elderly patients. Hypothesis HA for unstable IT fractures in elderly patients provides clinical results and 1-year survival comparable to HA for displaced FN fractures in the same aging group. Materials and methods We identified 80 patients aged 75 years or older, who underwent cementless bipolar HA for unstable IT fracture (AO/OTA type 31-A2.2/3 and A3.3). Their clinical results and 1-year survival were compared to the matched control group of 80 patients with displaced FN fractures (Garden type 3 and 4) treated with the same procedure. Perioperative results, postoperative complications, and 1-year survival were investigated between the two groups. Functional outcome was assessed by walking status and Harris hip score (HHS) 6 months after surgery. Results Operating time was significantly longer in the IT group than the FN group (97.3 min [50 to 255] vs. 79.3 min [40 to 175], P = 0.016). However, the two groups did not significantly differ regarding perioperative results, such as total blood loss, transfusion, intraoperative fracture, length of hospital stay, and postoperative complication. No statistically significant differences in walking status and HHS were observed between the groups. No significant difference in cumulative survival was observed between the two groups (P = 0.836), with a 1-year survival rate of 80% (95% confidence interval [CI], 71.8 to 87.5) in the IT group and 82% (95% CI, 73.1 to 89.4) in the FN group. Conclusion HA for unstable IT fractures in elderly patients showed clinical results and 1-year survival comparable to HA as the treatment of choice for displaced FN fractures in the same aging group. Level of evidence Level III, case-control study.

In this study, microstructures of a heat-affected zone (HAZ) of an SA 508 steel were identified by Mossbauer spectroscopy in conjunction with microscopic observations, and were correlated with fracture toughness. Specimens with the peak temperature raised to 1350 °C showed mostly martensite. With the peak temperature raised to 900 °C, the martensite fraction was reduced, while bainite or martensite islands were formed because of the slow cooling from the lower austenite region and the increase in the prior austenite grain size. As the martensite fraction present inside the HAZ increased, hardness and strength tended to increase, whereas fracture toughness decreased. The microstructures were not changed much from the base metal because of the minor tempering effect when it was raised to 650 °C or 700 °C. However, fracture toughness of the subcritical HAZ with the peak temperature raised to 650 °C to 700 °C was seriously reduced after postweld heat treatment (PWHT) because carbide particles were of primary importance in initiating voids. Thus, the most important microstructural factors affecting fracture toughness were the martensite fraction before PWHT and the carbide fraction after PWHT.