Evaluation of tendon graft fixation using alpha-BSM calcium phosphate cement

Many ligament reconstruction procedures require tendon healing within a surgically prepared bone tunnel. The interface between the graft and tunnel wall is the "weak link" in the initial phase of this process. By providing additional fixation and serving as a carrier for bone-derived growth factors, calcium phosphate cements may augment healing. The purpose of this study was to evaluate alpha-BSM calcium phosphate cement as the sole method of fixation for tendon and bone-tendon-bone grafts in an in vitro porcine model.

Ten tendon grafts and ten bone-tendon-bone grafts were fixed within porcine femoral and tibial bone tunnels by use of alpha-BSM calcium phosphate cement. The grafts were then loaded to failure. The ultimate pullout strength and the site of failure were recorded for each specimen.

The bone-tendon-bone grafts achieved a mean pullout strength of 224.8 N (+/-79.9 N). Of the grafts, 6 failed at the cement-bone plug interface, 2 failed because of fracture of the bone plug, and 2 failed at the tendon-bone plug interface. The tendon grafts had a mean load to failure of 81.2 N (+/-23.7 N), and all 10 failed at the tendon-cement interface. The difference in fixation strength between these graft types was significant (P < .05).

Though inadequate as the sole means of graft fixation, alpha-BSM calcium phosphate cement can help to augment bone plug fixation during the early phase of tendon-bone healing. In addition, alpha-BSM may provide added graft fixation and increased stiffness and act as a growth factor carrier for both tendon grafts and bone-tendon-bone grafts in ligament reconstruction surgery.

This study evaluated the ability of alpha-BSM cement to augment tendon-bone healing because it may play a role as a growth factor carrier in future tendon healing models.