Seven cases of benign bone tumors, a case of spinal fusion and. seven rases of un-united fractures of shafts of long bones, were treated with a.llogenir bone matrix gelatin (BMG) implants and were followed up for more than one year. All tumor cases were cured by osteo-induction from BMG, while only three of the seven fractures united. Two of the failures were reimplanted with BMG and failed again. Not a single case developed post-operative infection nor immunologic reaction. The BMG used was obtained from the same preparation, so that deterioration of its biological activity by endogenous protease was not likely. BMG small BMG cubes were used in tumor cases and slabs in fractures. The small cubes . were mixed with pieces of gel-foam and parked into the post-operative bony cavities while the slabs were arranged layer by layer at the fracture sites. This might be one of the reasons why the tumor rases had higher rate of cure Another reason was that non-unions needed prolonged, continuous and firm internal and external fixation post-operatively while the tumor cases needed not The amount of BMP calculated from BMG was not enough for early and solid osteogenesis. In the authors'opinion, with the use of new biomaterial, it should be followed by new method of application, but the principles of surgery should not be changed

Objective To discuss the levels of evidence provided by different study designs.Methods Websites of N Engl J Med, JAMA, Lancet, and BMJ were accessed to identify research articles (systematic review and meta-analysis included) published in 2009. A standardized data collection form was established using Epidata 3. 1 software to extract the "title", "country of lead author", "clinical problem" (such as treatment, diagnosis, etc. ) and "study design" of eligible studies. Descriptive statistics was conducted with SPSS 13.0. Results Over all, 844 studies were included, among which 35.7% were RCT,9. 4% systematic review and Meta-analysis, and 54. 9% other types of studies. Regarding clinical problems,34. 2%, 19. 7%, 13.7%, 6. 0% and 5. 1% of the included researches addressed the issues of treatment,etiology/risk factors, prevention, disease frequency and prognosis, respectively. The study designs that were most frequently adopted to explore these problems were RCT (70.6%), cohort study (44. 6% ), RCT (68. 1% ), cross-sectional study ( 56. 9% ), and cohort study ( 93.0% ), respectively. Conclusions High-level evidence does not come exclusively from RCT and systematic review, as each type of study may have its unique value in health related research. The clinical problem of interest, the previous work that has been done to approach the same issue, as well as other factors should be taken into account when deciding whether the selected study design is appropriate.