Objective To analysis the change of hip joint in healthy infants by ultrasound,and establish the normal reference value of the developmental dysplasia of the hip(DDH). Methods A total of 8 000 healthy infants from 0 to 24 weeks were collected from the Multi-center study of 10 children′s medical centers. Among them,3 855 infants(2 065 females and 1 790 males) with complete data and follow-up were included in this study. All subjects were divided into 6 groups ( ＜4,4～7,8～11,12～15,16～19 and≥20 weeks group). α angle,femoral head length and width,femoral head coverage ratio by acetabulum ( FHC) were measured in the coronal view on the neutral position;distance from pubis to femoral head ( P-H) and distance from ischium to femoral head ( I-H ) were measured in the transverse view on neutral position;distance from femoral head topubis ( H-P) was measured in the posterolateraltransverse view on the flexion position. The results of each group changes with age were analysised. Results ① The α angle of healthy infants from 0 to 20 weeks were increased with age,the difference among the groups were statistically significant( P ＜0.05),but there was no significant difference between 16～19 and ≥20 weeks group( P ＞0.05). ②The femoral head length and width of all age groups were increased with age,the difference among all the groups was statistically significant( all P ＜0.05). ③ FHC from 0 to 20 weeks were increased with age,the difference among the groups were statistically significant( P ＜0.05) except between 16～19 and ≥20 weeks group( P ＞0.05). ④ The P-H and I-H in all age groups showed no statistically significant ( all P＞0.05). ⑤The H-P of all age groups were increased with age,the difference between the groups were statistically significant(all P ＜0.05).Conclusions The development of hip joints have the certain regular developmental pattern in healthy infants less than 5 months of birth and are relatively constant after birth more than 5 months. The ultrasound normal reference value of the hip joints can be used for the early diagnosis of the DDH.

Cognition and pain share common neural substrates and interact reciprocally: chronic pain compromises cognitive performance, whereas cognitive processes modulate pain perception. In the present study, we established a non-drug-dependent rat model of context-based analgesia, where two different contexts (dark and bright) were matched with a high (52°C) or low (48°C) temperature in the hot-plate test during training. Before and after training, we set the temperature to the high level in both contexts. Rats showed longer paw licking latencies in trials with the context originally matched to a low temperature than those to a high temperature, indicating successful establishment of a context-based analgesic effect in rats. This effect was blocked by intraperitoneal injection of naloxone (an opioid receptor antagonist) before the probe. The context-based analgesic effect also disappeared after optogenetic activation or inhibition of the bilateral infralimbic or prelimbic sub-region of the prefrontal cortex. In brief, we established a context-based, non-drug dependent, placebo-like analgesia model in the rat. This model provides a new and useful tool for investigating the cognitive modulation of pain.
Action Potentials ; drug effects ; physiology ; Analgesics ; pharmacology ; therapeutic use ; Animals ; Disease Models, Animal ; Electric Stimulation ; Female ; In Vitro Techniques ; Naloxone ; pharmacology ; Narcotic Antagonists ; pharmacology ; Optogenetics ; Pain ; drug therapy ; pathology ; physiopathology ; Pain Measurement ; drug effects ; Pain Threshold ; drug effects ; physiology ; Patch-Clamp Techniques ; Physical Stimulation ; Prefrontal Cortex ; drug effects ; metabolism ; pathology ; Pyramidal Cells ; drug effects ; physiology ; Rats ; Rats, Sprague-Dawley ; Time Factors