Regenerative Repair of Long Intercalated Rib Defects Using Porous Cylinders of ??-Tricalcium Phosphate: An Experimental Study in a Canine Model

Abstract

In maxillofacial, spinal, and orthopedic surgery, bony ribs have been used as a source of donor bone. The resultant defects are not usually repaired, despite the pain or cosmetic morbidity experienced by the patient. The authors evaluated the efficacy of an osteoconductive beta-tricalcium phosphate and the contribution of the periosteum in rib bone regeneration. Two 8-cm-long intercalated rib defects were generated in each of 30 beagle dogs. In the first group (n = 15), one defect was implanted with 16 small, short, porous beta-tricalcium phosphate cylinders that were connected with a titanium wire, and the other defect was left untreated. In the remaining 15 dogs, the periosteum was devitalized by ethanol, and then the same surgical procedures were performed. Each group was subdivided into three groups (n = 5), and the animals were euthanized at 3, 6, and 12 weeks. Bone regeneration was assessed radiologically, histologically, and mechanically. In the defect implanted with beta-tricalcium phosphate on intact periosteum, newly formed bone was present on and in the beta-tricalcium phosphate cylinders and bridged both ends of the resected ribs at 12 weeks, with replacement of beta-tricalcium phosphate by new bone. Mechanical testing of these ribs revealed that they had 70 percent of the strength of normal ribs when compared in a bending stress test at 12 weeks after surgery. No regenerative bone bridging the rib defects was seen in the ethanol-devitalized or untreated groups. Porous beta-tricalcium phosphate cylinders placed in tandem on the intact periosteum might be useful for the repair of rib bone donated at surgery, presenting a new and unique method for regenerating rib defects.