ABSTRACT
Objective To observe the effect of sustained release type Ⅰ collagen-vascular endothelial growth factor (VEGF) on healing of bone-tendon junction injuries.Methods Partial patellectomy was conducted in 72 rabbits divided equally into control group,type Ⅰ collagen group,and collagen type Ⅰ-VEGF group.The scaffold was planted into the bone-tendon interface.Animals were sacrificed at 4,8 and 12 weeks.New bone formation into the patella-patella tendon surface was detected using X-ray films and histological observations.Quality of bone healing was assayed using biomechanical testing.Results At postoperative 4,8 and 12 weeks,X-ray films showed bone formation of type Ⅰ collagen group [(4.1 ± 0.4) mm2,(12.1 ± 0.5) mm2,(13.0 ± 1.2) mm2 respectively] and of collagen type Ⅰ-VEGF group [(3.8 ± 0.4) mm2,(11.0 ± 0.5) mm2,(13.1 ± 1.0) mm2 respectively] were more than that of control group [(2.1 ± 0.6) mm2,(4.1 ± 0.3) mm2,(6.6 ± 0.6) mm2 respectively] (P ＜ 0.05).Histology identified few new bone,massive fibrocyte accumulation and disrupted alignment of tendon fiber in control group,massive new bone formation,neat and orderly alignment of collagen fiber tissues and massive aggrecan expression at postoperative 4 and 8 weeks (fibrous cartage repair in largely) in collagen type Ⅰ-VEGF group,and massive new bone formation but worse alignment of tendon collagen fibers and less aggrecan expression (fibrous repair in largely) in type Ⅰ collagen group.Biomechanical test showed the ultimate tensile strength increased over time in all groups,with significantly higher value at 12 weeks than that at 4 and 8 weeks.At the same time point,ultimate tensile strength ranged in an order as follows:collagen type Ⅰ-VEGF group ＞ collagen type Ⅰ group ＞ control group (P ＜ 0.05).Conclusion Sustained release type Ⅰ collagen-VEGF can accelerate early healing of bone-tendon junction injury and improve the histological and mechanical properties.