Pathological diagnosis plays an important role in the assessment of destructive bone lesions. Before the treatment, a certain amount of tissue is obtained through needle biopsy for pathological diagnosis, which is of major significance for the selection of treatment plan and efficacy evaluation [1, 2, 7, 8]. Pathological specimens are generally obtained by incisional biopsy and needle biopsy. Although the accuracy of incisional biopsy is high and it allows obtaining a sufficient amount of lesion tissue , it presents several hindrances, e.g. high surgical cost, large trauma, and contamination of the surrounding normal tissue by the lesions . Compared with incisional biopsy, percutaneous biopsy has become the main method for preoperative biopsy of vertebral bone destruction diseases because of its simple operation, a smaller number of complications, and high accuracy . However, there are still many problems regarding the previous puncture methods, e.g. insufficient collection of lesion tissue, a greater number of complications, high cost, and low diagnostic accuracy [11,12,13,14,15,16,17].
Based on previous clinical experience, our team found that the modified OSBF is suitable for the biopsy of vertebral destruction lesions, and may significantly improve the shortcomings of traditional biopsy methods. Currently, PVP is widely used to treat vertebral osteoporotic compression fractures [18,19,20], and its matching threaded rod may be used to obtain the lesion tissue of the vertebral body [21, 22]. However, only a small amount of lesion tissue might be obtained through the gap of the thread, which cannot be used for biopsy. The diameter of the OSBF in the PVP is relatively large. Therefore, if it is employable for a needle biopsy, a more significant sample of the lesion may be obtained. Thus, we used the grinding technique to polish the smooth edge of OSBF into a jagged edge and it was successfully used for a needle biopsy in diseases associated with vertebral destruction.
In this study, the accuracy of needle biopsy in patients with primary tumors and tumor-like changes in the spine was of 91.8%, which was smaller than the accuracy of needle biopsy in patients with vertebral metastases (95.8%), these results are similar to what is found in the current literature [23,24,25,26,27]. For the primary tumor and tumor-like changes of the spine, the lesion site often lacks typical pathological features so that the diagnosis requires an increasing amount of typical lesion tissue [28, 29]. For vertebral metastases, pathologists have already known the possible malignant tumors and the source of the lesions , which is also the objective reason why many researchers believe that the accuracy of the tumor and tumor-like changes of the spine is lower than that of the vertebral metastases. Kamei et al  performed needle biopsies on 128 patients. The accuracy rate of primary tumor biopsy was 78.6%, and the accuracy of biopsy of metastatic tumors was 97.0%. Yang et al  performed needle biopsies on 247 patients. Needle biopsies yielded an accuracy of 84% for primary tumors and 97% for metastatic cancer. We used a modified OSBF to perform biopsies on 49 patients with primary tumor and tumor-like changes in the spine. The biopsy diagnosis of 45 patients was consistent with the final clinical diagnosis, which resulted in an accuracy rate of 91.8%, higher than that in previous studies.
The lesions found in vertebral infectious diseases are basically non-specific considering pathological manifestations, only showing the infiltration of a large number of inflammatory cells and no tumor cells. Granuloma and caseous necrosis are sometimes found in the lesions of some patients with specific vertebral infections. Therefore, the pathological manifestations of puncture specimens in patients with spinal infections may only be used as a reference for final diagnosis. We routinely perform pathogen examinations on patients suspected of having an infection before the operation. 11 patients in this study presented spinal infections, from which, 7 were positive for puncture pathogen culture, with a diagnostic accuracy of 63.6%. Eugenio et al  performed needle biopsies on 31 patients with spinal infection and the diagnostic accuracy rate is 58%, their results are similar to those found in our research. The timing of specimen collection, storage after collection, time of inspection, different test methods, and abuse of broad-spectrum antibiotics all lead to low culture positive rates . Therefore, the diagnostic accuracy of needle biopsy in those cases is lower than that of spinal tumors.
Previous studies with CT-guided vertebral biopsy have found that the diagnostic accuracy for sclerosing lesion biopsy is significantly lower than for osteolytic lesions [27, 31, 32]. An analysis of the reason is that for sclerosing lesions, there is hyperplasia of the vertebral cortical bone, therefore, traditional puncture instruments usually may not be able to penetrate the cortical bone smoothly. When compared with osteolytic lesions, sufficient and typical lesion tissue might not be obtained, so that the diagnostic accuracy of the needle biopsy is low. We modified the OSBF used in PVP to sharpen its smooth edges into sharp jagged edges while preserving the rigidity and strength of the serrations, ensuring that the modified OSBF may easily rotate and cut the hyperplastic cortical bone, and can reach the center of the lesion. Therefore, in our study, the diagnostic accuracy in osteolytic lesions was of 93.2%, while the diagnostic accuracy of sclerosing lesions was of 92.1%. There was no statistically significant difference between the two but both were considered to be of a high level.
It is reported that the accuracy of CT-guided biopsy diagnosis is lower in the thoracic spine . However, in our study, the accuracy rates of the thoracic and lumbar biopsy were 93.8% and 94.5%, respectively, both of which were at a high level. This finding confirmed that the modified OSBF has a high value for application in the biopsy of diseases promoting vertebral destruction. The accuracy of the biopsy diagnosis in the sacral vertebrae is 83.3%, which was considered to be low in our study. The reason may be that metastases are more common in the thoracic vertebrae and lumbar vertebrae, and the primary tumors are more common in the sacral vertebrae. As previously mentioned, the accuracy of biopsies of spinal primary tumors and tumor-like biopsies is lower than that of spinal metastases.
Guo et al  performed needle biopsies on 171 patients with bone tumors under the guidance of imaging techniques. The final biopsy accuracy rate was of 80.33%. Wu et al  performed needle biopsies on 151 patients presenting diseases that promote bone destruction guided by guidance imaging techniques and the final diagnostic accuracy was of 77%. Finally, Yang et al  performed needle biopsies on 247 patients with vertebral lesions under the guidance of imaging tools and 197 cases (80%) were correctly diagnosed. In the present study, we performed needle biopsies on 152 patients with vertebral bone destruction. A total of 149 patients were correctly diagnosed. The diagnostic accuracy was of 92.5%, which was considered to be of a high level. Because when we use the modified OSBF puncture, we were able to adjust the angle and depth of the cannula channel according to the intraoperative CT image to drill the lesion multiple times. Moreover, the modified OSBF has a larger diameter, and the strip lesion tissue may be obtained after each drilling. Therefore, we could obtain a sufficient amount of typical lesion sample, which is the reason for the high accuracy in our biopsy diagnosis.
For some patients in this study, the best timing for surgery was lost at the time of the visit, resulting in the necessity of radiotherapy and chemotherapy. Some patients with vertebral metastases abandoned the treatment. Although patients who had not undergone surgery had no postoperative pathological diagnosis, a final diagnosis could be made based on the patient's clinical data, response to treatment, and follow-up. Due to the complexity of the tissue structure around the vertebral body, the surgeon of the puncture biopsy should be skilled in the spine anatomy. The puncture should be carried out under the accuracy of the CT, avoid damage to the blood vessels and nerves. The patient's blood regulations and coagulation routine examination should be completed before the puncture biopsy, avoiding the constantly bleeding or hematoma. The surgeon should avoid repeating multiple puncture, reducing the surrounding tissue damage, reducing the low back pain after puncture activity. The puncture device may also be applied to the biopsy of bone tumors in the limbs. The working principle is similar, and the operation method is simpler than those of the standard technique. This study also presents some limitations, e.g. the limited number of cases and no control group, those limitations will be overcome in future researches.