Differential gene expression analysis in fracture callus of patients with regular and failed bone healing.

OBJECTIVE: Although several systemic and local factors are known to impair fracture healing, there is still no explanation, why some patients with sufficient fracture stability, showing none of the existing risk factors, still fail to heal normally. An investigation of local gene expression patterns in the fracture gap of patients with non-unions could decisively contribute to a better understanding of the pathophysiology of impaired fracture healing. For the first time, this study compares the expression of a large variety of osteogenic and chondrogenic genes in patients with regular and failed fracture healing. METHODS: Between March 2006 and May 2007, a total of 130 patients who were surgically treated at the Berufsgenossenschaftliche Unfallklink Ludwigshafen were screened for the study. Tissue samples of patients with normal and failed fracture healing were collected intraoperatively. Patients were divided into groups depending on the fracture date, and only patients with fractures two to four weeks old and patients with non-unions more than 9 months old were included in the final analysis. For the gene expression analysis, a customised cDNA array - containing 226 genes involved in osteo- and chondrogenesis - was used. RESULTS: In the cDNA array analysis, the expression of eight genes was significantly elevated two-fold or more in the group with failed fracture healing relative to the normal controls. Conversely, no genes were found to be expressed at a higher level in the control group. The identified genes are supposed to be involved in extracellular matrix assembly, cytoskeletal structure, and differentiative and proliferative processes. CONCLUSIONS: The differences in gene expression pattern indicate a change in the composition and structure of the extracellular matrix, and a possible turn in the healing programme towards fibrous scar tissue formation, leading to non-union.

Cigarette smoking decreases TGF-b1 serum concentrations after long bone fracture.

TGF-b1 serum concentrations are considered to be one of the most promising markers of fracture healing. Previously, we demonstrated significant differences in the post-traumatic time courses of patients with timely and delayed fracture healing. The aim of this study was to evaluate possible differences in the serum concentrations of TGF-b1 in cigarette-smoking vs. non-smoking patients with timely and delayed fracture healing in order to understand pathophysiological pathways through which smoking impairs fracture healing.Serum samples were collected from 248 patients undergoing surgical treatment for long bone fractures within 1 year of surgery. Samples from 14 patients with atrophic-type delayed fracture healing were compared with 14 matched patients with normal bone healing. Each group included seven smokers and seven non-smokers. Post-operative serum concentrations were analysed at 1, 2, 4, 8, and 12 weeks as well as 1 year after surgery. The patients were monitored both clinically and radiologically for the entire duration of the study.All patients increased TGF-b1 serum concentrations after surgery. In patients with normal fracture healing, significantly higher TGF-b1 levels were observed in non-smokers (70 ng/ml) than in smokers(50 ng/ml) at the 4th week after surgery (p = 0.007). Also at the 4th week, in patients with delayed healing, significantly lower TGF-b1 levels were observed in smokers than in non-smokers (38 ng/ml vs.47 ng/ml, p = 0.021). However, no significant differences between non-smokers with delayed healing and smokers with normal healing (p = 0.151) were observed at the 4th week after surgery. TGF-b1 serum concentrations reached a plateau in all groups from the 6th to the 12th week after surgery, with a slight decrease observed in the final measurement taken 1 year after surgery.This study demonstrates that, after fracture, TGF-b1 serum concentrations are reduced by smoking,and this reduction is statistically significant during the 4th week after surgery. Our findings may help reveal the mechanism by which smoking impairs fracture healing. Furthermore, these results may help to establish a serological marker that predicts impaired fracture healing soon after the injury. Surgeons will not only be able to monitor the bone healing, but they will also be able to monitor the success of additional treatments such as ultrasound and bone morphologic proteins (BMPs).

Treatment of tibial shaft non-unions: bone morphogenetic proteins versus autologous bone graft.

Fractures of the tibial shaft are likely to result in delayed union or non-union; 10-30% of these fractures will not heal properly and are commonly treated with autologous bone grafting. BMP-7 is a recombinant bone growth factor that can be applied locally as an alternative or in addition to autologous bone grafting, and this study aimed to compare the efficiency of the two procedures. From January 1995 to December 2002, 82 people with delayed union of a tibial fracture at least 4 months after primary stabilisation underwent autologous bone grafting. Successful healing was defined as radiological bony consolidation. Between May 2002 and June 2005, 26 similar cases were treated after the failure of the graft with local implantation of BMP-7, and were followed up for at least 1 year. Of the 82 people receiving autologous bone grafts only, 24 (28%) still had no signs of consolidation after 4 months and required revision surgery. Of the 26 people with BMP-7 implantation after failed graft, bony consolidation was seen after 4 months in 24 cases and only 2 (8%) required revision surgery. The BMP-7 group, although including more complicated cases, showed a significantly higher (p = 0.025) success rate compared with the group that did not receive BMP-7.