Background:Early accelerated motion programs that include continuous passive knee motion or guarded motion immediately after anterior cruciate ligament (ACL) reconstruction are
advocated because athletes have a strong desire to quickly return to a pre-injury level of function. However, studies found that accelerated motions after ACL reconstruction with hamstring grafts may
result in greater graft-tunnel micromotion, which could increase the bone resorption and inhibit early osteointegration of grafted tendon. As known, the osteointegration of grated tendon is critical
to the ultimate success of ACL reconstruction with hamstring tendons.
Injectable calcium phosphate cement (CPC) has been demonstrated that could aid in the bond of grafted tendon and bone tunnel, and in the osteointegration of grated tendon. For improving the slow
degradation of CPC, we constructed a new porous CPC composite with bone growth factor (CPCXB), which could more effectively enhance osteointegration of grafted tendon than CPC alone.
However, little is known about whether CPC or CPCXB could consistently promote the osteointegration of grafted tendon during an accelerated motion after ACL reconstruction. Thus, we designed this
study to test that, and we supposed that the application of CPCXB would result in more new bone formation than the application of CPC in the grafted tendon osteointegration process.
Methods:ACL reconstruction was performed bilaterally in 42 rabbits. CPC or CPCXB composite was separately injected into knees. On the basis of clinical rehabilitation programs, an
accelerated protocol, including 4-week continuous passive exercise (CPM) and 4-week treadmill exercise, was performed on the 1st day after surgery. After 8-week exercise, the rabbits were sacrificed
for micro-CT testing, histological analysis, and mechanical testing.
Results:The micro-CT examination showed that both new bone volume and new bone microarchitecture in the CPC or CPCXB group was superior to that of the control group within CPM plus
treadmill motion. What’s more, the micro-CT results in the CPCBX group were significantly better than those in the CPC group. Histological observations also showed there were more new cartilage and
new bone in the interface in the CPCXB group. Biomechanically, the ultimate load to failure of CPC and CPCXB group was higher than that of the control group.
Conclusions:Both CPC and CPCXB composite may persistently enhance the osteointegration of grafted tendon with accelerated motion. But the CPCXB achieves a better effect. This study
provided more experimental insights for the application of injected CPCXB in ACL reconstruction.