The Initial Study Of The Early Effect Of Tendon-Bone Healing Using Calcium Phosphate Cement

Objective To explore the early effect of tendon-bone healing using calcium-phosphate cement(CPC),we built the extra-articular tendon-bone healing mould in rabbits and performed the animal experiments about histology and biomechanics.Methods The posterior limbs of 30 healthy adult New Zealand white rabbits were divided into experimental groups( CPC groups) and control groups (non-CPC groups) by random.A bone tunnel,with a diameter of 3.0 mm,was established in the distal tibia.The flexor digitorum longus tendon was chosen as transplanted tendon ,and was embeded into the bone tunnel.CPC was injected into the gap of tendon-bone in experimental groups.Nothing was used in the gap of tendon-bone in control groups.All rabbits were feeded in cages respectively.Two rabbits each were killed to collect the samples for the histological observation of the interface at the postoperative end of weeks 1,2,3,4 and 6.In order to perform the biomechanical test,ten rabbits every time were killed sequentially at the postoperative end of the second and fourth weeks.Paired t-test was used to analyse the data of biomechanical experiments with statistical software 13.0(a=0.01).Results 30 rabbits survived very well,and there were no infection in the incisions.The histological results indicate:some fibroblasts,osteoblasts and collagen fibers were observed in the gap of the interface in the CPC groups,while there were only few fibroblasts in the control groups at the end of the first week.In the second weekend,we could observe many fibroblasts,osteoblasts and collagen fibers.There were early connection between bone tunnel and collagen fibers in the CPC groups.At the same time fibroblasts in the control groups increased.Few osteoblasts and collagen fibers appeared in the gap of interface.In the third week,there were many fibroblasts and osteoblasts.The transplantated tendon was integrated with collagen fibers.Osteoblasts proliferated actively.A wrap of new bone existed on the surface of residual bone cement.In the control groups,there were much more fibroblasts,osteoblasts and collagen fibers. Connective tissues contacted with bone tunnel loosely.In the fourth week, fibroblast reduced and were maturating into fibrocytes.A lot of collagen fibers were connected with bone tunnel tightly.Much new bone and calcium salts cemental line were observed at the side of bone tunnel.Fibroblast decreased and collagen fibers multed.A little loose connective tissue contacted with bone tunnel.Some osteoid tissue was observed.In the sixth week,an abundance of ordered new collagen fibers were observed in the gap of interface.They were integrated with tendon and bone.Much more New bone was observed at the side of bone tunnel in CPC groups.In non-CPC groups,a number of fibroblasts maintained,and collagen fibers increased obviously.A small quantity of loose connective tissue contacted with bone tunnel.Some osteoid tissue and new bone could be observed.In the second and fourth weeks,the maximal pull-out loading of biomechanics in the experimental groups were much more superior than in the control groups. Paired t-test proved that there was significant difference between the CPC group and non-CPC group.Conclusion CPC can shorten the time of ossification and enhance the tendon-bone healing directly or indirectly.At the early period of time,the junction between tendon-bone remains fibril connection.It is a kind of indirect healing,not the direct insertion similar to the normal one of tendon-bone.But it is changing into the direct insertion.