Population bioequivalence (PBE) is a statistical approach recommended by FDA to evaluate the consistency of particle size distribution of numerous nanoparticle products.However, when particle size distribution (PSD) profile exhibits multiple peaks or other complex distributions, the traditional descriptors D50 and SPAN are no longer suitable to describe PSD.Earth mover''s distance (EMD) is a new statistical metric for assessing the difference between distributions.In this study, we used EMD to measure the discrepancy between PSD and then PBE was applied to perform statistical test to establish equivalence.Our results showed that the proposed method can effectively reject an unequivalent product and pass an equivalent product, thus indicating its helpfulness in guiding the optimization of formulation and preparation process.

Objective:To investigate the characteristics of fragility fractures of pelvis(FFP) in the elderly and compare the clinical efficacy between conservative treatment and minimally invasive surgery.Methods:A retrospective study was conducted in the 56 elderly FFP patients who had been treated at Department of Orthopaedics, The General Hospital of Chinese People＇s Liberation Army from January 2017 to January 2019. They were 16 males and 40 females, with an age of 73.4 years (from 65 to 93 years). By the American Society of Anesthesiologists (ASA) classification, there were 12 cases of grade Ⅰ, 16 cases of grade Ⅱ, 20 cases of grade Ⅲ, and 8 cases of grade Ⅳ; by the FFP classification, there were 6 cases of type Ⅰ, 10 cases of type Ⅱ, 36 cases of type Ⅲ, and 4 cases of type Ⅳ. The morphological characteristics and injury mechanisms of FFP were analyzed. According to the treatment methods, the patients were divided into a conservative treatment group of 32 cases and a minimally invasive surgery group of 24 cases. The 2 groups were compared in terms of complication incidence, mortality and the Koval attenuation rate of walking ability after one-year follow-up.Results:There were mostly the fractures of pubic branches on both sides of the pubic symphysis and compression fractures of the sacral wing caused by lateral crush injury. The 2 groups were comparable due to no significant differences in the preoperative general data between them other than FFP classification ( P>0.05). By one year after treatment, the conservative treatment group had a complication incidence of 34.4% (11/32), a mortality of 9.4% (3/32) and a Koval attenuation rate of walking ability of 13.8% (4/29) while the minimally invasive surgery group had a complication incidence of 20.8% (5/24), a mortality of 4.2% (1/24) and a Koval attenuation rate of walking ability of 8.7%(2/23), showing no significant difference between the 2 groups ( P>0.05). Conclusions:The injury mechanism of geriatric FFP is mostly lateral compression injury. The fracture sites are mostly located on both sides of the pubic symphysis, pubic branches and the sacral wing of anterior and posterior rings simultaneously. Although there may be no significant difference in complication incidence, mortality or Koval attenuation rate of walking ability between conservative treatment and minimally invasive surgery after one year, the minimally invasive surgery deals with more unstable fracture types.