The progress of early phase bone healing using porous granules produced from calcium phosphate cement

Abstract

Objective Bone grafting is a vital component in many surgical procedures to facilitate the repair of bone defects or fusions. Autologous bone has been the gold standard to date in spite of associated donor-site morbidity and the limited amount of available donor bone. The aim of this study was to investigate the progress of bone regeneration and material degradation of calcium phosphate granules (CPG) produced from a calcium phosphate self-setting cement powder compared to the use of autologous bone grafting in the treatment of "critical size defects" on load-bearing long bones of minipigs. Methods A critical size defect in the tibial metaphysis of 16 mini-pigs was filled either with autologous cancellous graft or with micro- and macroporous carbonated, apatic calcium phosphate granules (CPG) produced from a calcium phosphate self-setting cement powder. After 6 weeks, the specimens were assessed by X-ray and histological evaluation. The amount of new bone formation was analysed histomorphometrically. Results The semi-quantitative analysis of the radiological results showed a complete osseous bridging of the defect in three cases for the autograft group. In the same group five animals showed a beginning, but still incomplete bridging of the defect, whereas in the CPG group just two animals developed this. All other animals of the CPG group showed only a still discontinuous new bone formation. Altogether, radiologically a better osseous bridging was observed in the autograft group compared to the CPG group. Histomorphometrical analysis after six weeks of healing revealed that the area of new bone was significantly greater in the autograft group concerning the central area of the defect zone (p < 0.001) as well as the cortical defect zone (p < 0.002). All defects showed new bone formation, but only in the autograft group defects regenerated entirely Conclusions Within the limits of the present study it could be demonstrated that autologous cancellous grafts lead to a significantly better bone regeneration compared to the application of calcium phosphate granules (CPG) produced from a calcium phosphate self-setting cement powder after 6 weeks. In the early phase of bone-healing, the sole application of CPG appears to be inferior to the autologous cancellous grafts in an in vivo critical size defect on load-bearing long bones of mini-pigs.

Bone marrow concentrate for autologous transplantation in minipigs

“…In the central part of the bone defect, the mean percentage of newly deposited bone in the NCC + CPG group was 31.4 ± 7.0% (range 21.4 -43.2%) and 35.4 ± 6.2% (range 25.4 -49.3%) in the cortical part as shown in ▶ Table 3. In comparison to our previously published data, the area of new bone was greater in the NCC + CPG group compared to CPG alone concerning the central area of the defect zone as well as the cortical defect zone (26).…”

“…In order to exclude the possibility that the bone healing can be ascribed to the cal-cium phosphate granules (CPG) alone, we compared the bone healing rate of NCC plus CPG with a control group, where CPG was used alone (26). In comparison to our previously published data, the area of new bone was greater in the NCC + CPG group compared to CPG alone concerning the central area of the defect zone as well as the cortical defect zone.…”

“…In comparison to our previously published data, the area of new bone was greater in the NCC + CPG group compared to CPG alone concerning the central area of the defect zone as well as the cortical defect zone. Using the CPG data as a historical control, we conclude that the improved healing can be attributed to the addition of NCC to the defect because CPG alone does not seem to lead to relevant de novo bone healing in the defect model used (26). Hernigou et al described a positive correlation between the volume of mineralized callus at four months postoperatively and the number (r 2 = 0.3; p = 0.04) and concentration (r 2 = 0.6; p = 0.01) of CFU-F in the graft (22).…”

“…The defect was packed with NCC and micro-and macro-porous, carbonated calcium phosphate granules s (CPG) as bone substitute material. A control group where CPG was used solely to fill the defect has been described previously (26). The CPG used had a pore size of 50-550 μm with 2 to 4 mm in size and was produced from calcium phosphate self-setting cement powder (26).…”

“…A control group where CPG was used solely to fill the defect has been described previously (26). The CPG used had a pore size of 50-550 μm with 2 to 4 mm in size and was produced from calcium phosphate self-setting cement powder (26). The animal model and the detailed surgical procedure have been described earlier (27,28).…”