目的 对肋骨骨折的法医临床鉴定时间进行探讨。方法 对40例定期复查的肋骨骨折鉴定案件的CT表现和时间相关性进行研究。结果 26例被鉴定人外伤后2、4、6w CT检查所见的肋骨骨折部位数量有增多趋势,外伤4w后检查所示骨折部位数量趋于稳定。复查发现的肋骨骨折有79.3%表现为肋骨内侧或者外侧局部轻微的骨皮质断裂不完全性骨折,20.7%未能观察到骨折线,仅表现为局部密度增高和骨痂生长。结论 对肋骨骨折鉴定案例,在外伤4w后复查CT再进行人体损伤程度鉴定,可以有效避免损伤认定发生遗漏或鉴定意见出现错误。

Objective Rib fracture is a common injury in clinical forensic identification. According to the current injury degree and disability grade identification standard, different counts of rib fracture will result in different identification of injury degree and disability grade. The theoretic exploration of identification time of rib fracture can give an appropriate identification time for forensic clinical identification staff and avoid missed diagnosis or mistakes.Methods A retrospective study of 40 injury cases involved in rib fracture from 2011 to 2013 in Lishui was conducted. Chest multi-slice CT scanning was performed right immediately, and 2, 4, 6 weeks after injury, respectively. The correlation between the CT findings and timing was studied. The count and location of rib fracture were calculated for each CT examination. The missed diagnosis cases were classified. Bone fractures associated with both fracture line and callus growth and bone fracture with callus growth only in CT scanning were differentiated. The reason for the change of rib fracture count was analyzed.Results Of the 40 cases, 14 and 26 cases showed no changes and an increase in rib fracture sites, respectively. In the newly found 87 rib fractures by reexamination, 62% of them (54) were anterior to the anterior axillary line, 25%(22) were between the anterior axillary line and the posterior axillary line, 17%(11) were posterior to the posterior axillary line. Fracture lines and callus growth could be seen in 69 of the 87 rib fractures. All of them were incomplete fractures, which manifested as mild local interrupted bone cortex in the internal or external sites of ribs. Only local callus growth without obvious fracture lines could be seen in the other 18 fracture sites, which all located on the 2~7 anterior ribs. The count of rib fracture increased in 26 patients with CT scanning in 2 and 4 weeks following injury, while it tended to be steady after 4 weeks.Conclusions Fracture healing can be divided into three stages, including organization of hematoma stage, porotic stage and callus remodeling stage. In the early stage of rib fracture, the fracture line becomes more obvious by the breathing movement, organization of hematoma and the process of osteoclast eliminating the dead bone. But rib fracture may be missed diagnosis because of the unobvious fracture line in the early stage after injury. Rarefaction of bone and thin of bone cortex are main factors which is caused by the old age or the position of anterior rib to make the fracture line unobvious to display in CT images. As the repairing of fracture and calcium deposition in the callus, a gradual increase in density can be found in CT scanning. The direction of the fracture line close to the axle of the CT scanning could cause missed diagnosis of the hairlike fracture line. The thickness of layer over 1mm of CPR and MPR images would easily cause missed diagnosis. Our study shows that injury degree identification followed by CT examination in 4 weeks after injury in individuals with rib fractures is recommended because rib fracture site could be confirmed by callus growth. Missed diagnosis or mistakes can effectively be avoided in this way.