1.1 Ethical approval
The study was approved by the ethical committee of Chinese PLA General Hospital. Written informed consents for study were obtained from all children‘s parents.
1.2 Inclusion and Exclusion criteria
Inclusion criteria: (1) Age was under 14 years old. (2) Diagnosis was ascertained by X-ray, CT or MRI images. For the suspicious ones, pathological biopsy was performed. (3) No treatments were performed before admission.
Exclusion criteria: (1) Lesions complicated with other neoplasms. (2) Pathological fractures occurred in the processes of internal and external fixations.
1.3 Criteria for diagnosis
In X-ray plains, simple cyst presents with a round or oval lowdensity area with mild plumping. Its long axis is mostly parallel to the shaft. Bone ridge separation is visible inside of the bone cyst. The boundary of the cyst is clear and sharp, mostly with thin-wall sclerotic edge. Bone debris collapse sign can be found when pathological fracture happens1 13.
1.4 Patients data
83 children with simple bone cysts were retrospectively studied. They admitted to the department of pediatric orthopedic of Chinese PLA general hospital from January 2010 to December 2016. Twenty-eight cases were treated with ABM. Twenty-eight cases were treated with ESIN. Twenty-seven cases were treated with ABM combined with ESIN. The general data of the patients were shown in Table 1. There were no statistical significances of age, gender constitution, weight and height among the three groups.
1.5 Surgical procedures
ABM Injection14: General anesthesia with endotracheal intubation was applied, the child was routinely sterilized and toweled. Before injection, 0.4% lidocaine wainjected on the bone surface for local anesthesia. Under X-ray fluoroscopy guidance , a core-inside needle was punctured to the bone surface. The needle tip slowly pierced into the cortex, with the core withdrawing, light-colored liquid slowly drilled out. Then the needle sheath advanced further with X-ray guidance to the central of the cyst cavity and fastened well. Next, after local anesthesia of the anterior superior iliac spine region, ABM was extracted then slowly injected into the bone cyst cavity. After injection completion, the puncture needle was removed. The puncture points were covered with sterile dressings.
ESIN Implantation14: Anesthesia and X-ray fluoroscopy guidance were the same with ABM. A 0.5 cm incision was made at the epiphysis of the long diaphysis away from the bone cyst. Hemostatic forceps bluntly dissected subcutaneous tissue to the bone cortex. The nail drilled a hole in the cortex. The ESIN, pre-bent into a "C" shape, was slowly inserted into the medullary cavity along the drill hole with the guidance of fluoroscopy X-ray. After the ESIN is properly implanted, bending and cutting the outer portion of the nail for a completely subcutaneous embedding. The incision was sutured and wrapped with sterile gauze.
ESIN+ABM method: After one to three ABM injections with three-month intervals, ESIN implantation was followed.
All cases were given postoperative antibiotics of cefuroxime sodium for two days. The affected limbs were fixed with plaster for six to eight weeks. All cases were encouraged to early exercises after surgery. For cases of lower extremities lesions, in order to avoid pathological fracture, they were encouraged weight-free exercises in bed in the early period of recovery.
1.6 Follow-up and outcome appraisal indicators
The therapeutic effect of treatment was evaluated by the criteria of Capanna12 for bone cyst. All children received preoperative X-ray, CT or MRI examinations. Pathological biopsy was carried out if necessary. All patients were followed up with X-ray examinations. Preoperative and Postoperative images evaluation were performed for all the patients. In the process of Capanna evaluation, two experienced clinicians conducted double-blind evaluation. When there was difference in the scores of the same patient, the third specialist participated. The evaluation criteria of Capanna12 for bone cyst: (1) Complete cure: The cyst cavity is completely filled with new bone. No residual lesion is observed. (2) Residual Cure : Lesion area is mostly replaced by newly growing bone tissue. The mixture of newly growing bone with the surrounding cyst wall bone can be seen. The cyst wall of cortex scleroses and thickens. Small transparent areas present in the original cyst site. (3) Recurrence: In the early stage of the treatment, good effect can be observed. Subsequently, transparent areas in the original cyst cavity emerged again. Bone cortex around the cyst becomes thinner. (4) No response: X-ray shows no favorable changes and healing tendency.
Effective cases included complete cure and residual cureones. Effective rate was calculated by the proportion of effective cases to the total number of the cases being treated.
1.7 Statistical analysis
SPSS 20.0 statistical analysis software was used for statistical analysis. One-way ANOVA test was used in the analysis data of admission times, age, and height. Kruskal-wallis rank-sum test was used in the analysis of weight, follow-up duration and therapeutic times for cure ones. Chi-square test was used in the analysis of gender composition, effective rate, cure rate and the site of cyst. P<0.05 was considered statistical significance.