1.1 Ethical approval
The study was approved by the ethical committee of the Chinese PLA General Hospital. Written informed consent for this study was 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, the pathological biopsy was performed. (3) No treatment was performed before admission.
Exclusion criteria: (1) Lesions were 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, the simple cyst presents with a round or oval low-density 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 the thin-wall sclerotic edge. Bone debris collapse sign can be found when pathological fracture happens1 13.
1.4 Patients data
Eighty-three children with bone cysts were retrospectively studied. They were admitted to the Department of Pediatric Surgery 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 patients were shown in Table 1. There was no statistical significance in age, gender constitution, weight, and height among the three groups.
Table 1 General clinical data in 83 cases among three groups
1.5 Surgical procedures
ABM Injection14: After general anesthesia with endotracheal intubation, the operative area were sterilized and laid with sterile sheets. Under the guidance of X-ray fluoroscopy, a core-inside trocar was punctured to the bone surface adjacent to the cyst. Then it was pierced into the center of the cyst slowly. When the inside core of the trocar was withdrawn, the liquid of the bone cyst outflowed. Next, ABM extracted from the Iliac crest was injected into the bone cyst cavity slowly. After the completion of the ABM injection, the trocar was removed. The puncture points were covered with sterile dressings. The diagram of ABM injection was shown in Figure 1a.
ESIN Implantation14: After general anesthesia with endotracheal intubation, the operative area were sterilized and laid with sterile sheets. Under the guidance of X-ray fluoroscopy, a 1 cm incision was made at the epiphysis of the long diaphysis away from the bone cyst. A hemostatic forceps was used to dissect the subcutaneous tissue to the bone cortex. An electric drill was used to drill a hole in the bone cortex. The ESIN, pre-bent into a "C" shape, was slowly inserted into the medullary cavity along the drill hole with the guidance of X-ray fluoroscopy. When the ESIN was properly implanted, the outer portion of the nail was bent and cut for complete subcutaneous embedding. Then the incision was sutured and wrapped with sterile gauze. The diagram of ESIN implantation was shown in Figure 1b.
ESIN+ABM method: After one to three times of ABM injection with the interval of three-month in each time, the ESIN was implanted.
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 cyst cases of lower extremities, they were encouraged to weight-free exercise in bed in the early period of recovery in order to avoid pathological fracture.
Figure 1 The diagrams of autologous bone marrow injection(1a) and elastic stable intramedullary nail implantation (1b). 1a. The bone marrow blood was extracted from the ilium using a bone penetration needle (short solid arrowhead) and injected into the femoral cyst with the guidance of the X-ray fluoroscopy. 1b. The holding device (hollow arrowhead) was used to implant the elastic intramedullary needle (long solid arrow) into the femur with the guidance of the X-ray fluoroscopy.
1.6 Follow-up and outcome appraisal indicators
The therapeutic effect of treatment was evaluated by the criteria of Capanna12 for the bone cyst. All children received preoperative X-ray, CT, or MRI examinations. The 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 the double-blind evaluation. When there was a 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 the cortex sclerosis thickens. Small transparent areas present in the original cyst site. (3) Recurrence: In the early stage of the treatment, a 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 cases and residual cure cases. The 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.