The evaluation of a degradable Magnesium alloy Bio-Transfix nail system compounded with bone morphogenetic protein-2 in a beagle anterior cruciate ligament reconstruction model

To evaluate a porous ZK60 magnesium alloy Bio-Transfix nail system compounded with bone morphogenetic protein-2 (BMP-2) on tendon-bone healing in a beagle anterior cruciate ligament reconstruction model. Three dogs were utilized to assist in nail design; the remaining 18 dogs were randomly divided into porous ZK60 magnesium alloy Bio-Transfix nail system compounded with BMP-2 group (BMP-2 group), porous ZK60 magnesium alloy Bio-Transfix nail group (porous group), and non-porous ZK60 magnesium alloy Bio-Transfix nail group (control group). Imaging examinations including X-ray, Micro-CT, and MRI were examined to detect the dynamic bone growth after anterior cruciate ligament reconstruction separately at 4 days, 4, 8 and 12 weeks postoperatively. Fail-to-load test, histology examination, and energy spectrum were further conducted to determine the condition of tendon-bone healing. With the degradation of ZK60 magnesium alloy Bio-Transfix nail system, imaging examinations confirmed the new bone growth surrounding the implant; the BMP-2 group showed the least hydrogen accumulation among the groups. Fail-to-load test demonstrated that BMP-2 group presented higher fail-to-load strength than the porous group and control group. Scanning electron microscope results indicated that most of the ZK60 magnesium alloy Bio-Transfix nails have degraded and lost original appearance at 12 weeks postoperatively, only BMP-2 group showed a non-complete degradation; meanwhile, the BMP-2 group presented with a better new bone-implant growth among groups. The porous ZK60 magnesium alloy Bio-Transfix nail system nail with BMP-2 compounded could ideally induce new bone growth and promote tendon-bone healing, which has the potential value to be generalized in anterior cruciate ligament reconstruction surgery.