This study is aimed to construct a multi-parameter early-warning model based on usage of mannitol, using multi-factor regression and combining with previous clinical experience, literature, expert opinions. The investigators will evaluate the predictive value of the model for mannitol usage and gypsum cutting open through cohort study verification.

The investigator will retrospect the data of operative patients with limb fracture in Pediatric Orthopedics Unit of Shanghai Xinhua Hospital in 2016 to collect the basic information about this kind of patient, including age, gender, kind of fracture, temperature and color of skin, swell, artery pulse, laboratory test indicators, method of fixation, and the usage of mannitol. Then, combining the professionals' suggestions, the investigator will use multi-factor regression to identify the independent risk factors of blood circulation disorder. According to the independent risk factors, the early-warning model of blood circulation disorder will be built, and the rating scale as well. Finally, the critical value of blood circulation disorder after limb fracture will be set by receiver operating characteristic curve.

Inclusion Criteria:

• Age from 0 to 14 years;
• Children with limb fractures diagnosed by X-ray film;
• The surgical method is open reduction and wire-pin fixation or steel plate internal fixation;
• Children with postoperative plaster fixation;
• Children whose guardian signed informed written consent.

Exclusion Criteria:

• Children with nerve damage which have caused dysfunction such as sensory and motor;
• Children with fracture in other parts or organic diseases.

Children with limb fractures diagnosed by X-ray film