[Clinical results and the mechanism of bone healing for the repair of bone defects due to tumor resection with novel interporous TCP].

OBJECTIVE To investigate the clinical results and the mechanism of bone healing for the repair of bone defects following tumor resection with novel interporous TCP bone graft, and to test the hypothesis of "structural transplantation". METHODS From January 2003 to December 2005, 61 cases of various bone defects following the curettage of the benign bone tumors were treated with interporous TCP, with 33 males and 28 females, including bone fibrous dysplasia in 8 cases, bone cyst in 23 cases, eosinophilic granuloma in 12 cases, enchondroma in 13 cases, non-ossifying fibroma in 2 cases, and osteoblastoma in 3 cases. Tumor sizes varied from 1.5 cm x 1.0 cm to 7.0 cm x 5.0 cm. The plain X-ray, single photon emission computed tomography (SPECT) and histology examination were obtained at various time points after operation. The in vivo biodegradation rate of the implanted TCP was evaluated based on a semi-quantitive radiographic analyzing method. Histopathology examination was performed in 1 revision case. RESULTS All the patients were followed up for 5 to 24 months after operation. They all had good wound healing and bone regeneration. There was neither significant reverse reaction to the transplanted material nor locally inflammatory reaction in all of the cases. The bone defects were repaired gradually from 1 to 6 months after operation (bone healing at average 2.6 months after surgery) with a bone healing rate up to 96.7%. There was only 1 recurrence case (eosinophilic granuloma in ischium) 3 months after operation. Given revision operation, this case gained bone healing. Radiographically, the interface between the implanted bone and host bone became fuzzy 1 month after implantation, indicating the beginning of new bone formation. Three months later, the absorption of the interporous TCP was noticed from peripheral to the center of the implanted bone evidenced by the vague or fuzzy realm. New bone formation could be seen both in peripheral and central areas. Six months later, implanted bone and host bone merged together and the bone defect was totally repaired, with 78.9% degradation rate of the implanted TCP. Twelve months later, the majority of the implanted bone was absorbed and bone remodeling was established. In the cases that were followed up for 24 months, the function of affected extremity was excellent with good bone remodeling without recurrence. In 2 cases, SPECT showed that nuclide uptake could be observed in implanted site and the metabolic activity was high both in the central as well as the peripheral areas of the graft 1 month after implantation, which was an evidence of osteogenesis. Pathologically, the interporous TCP closely contacted the host bone inside the humerus 1 month after grafting. The interface between the implanted bone and host bone became fuzzy, and vascularized tissue began growing inside the implanted graft as a "lining" structure. CONCLUSION The interporous TCP proves to be effective for clinical reparation of bone defects following tumor resection. The inside three-dimensional porous structure simulates the natural bionic bone structure which is suitable for recruitment related cells in-growth into the scaffold, colonizing and proliferation companied with the process of vascularize, finally with the new bone formation. The novel interporous TCP may boast both bone conductive and bone inductive activities, as an appealing "structural transplantation" bone graft.