Open reduction and Kirschner wire fixation method using a cylindrical block of unidirectional porous β-tricalcium phosphate for tongue-shaped calcaneal fracture: Report of three cases.

Background: The artificial bone grafts are performed on the defect after reduction of the calcaneal fracture. Generally, it is an artificial bone graft with an implant, and there are a few reports of an artificial bone graft without an implant.

Cases: We report three cases (42-year-old male, 67-year-old male, 21-year-old female) of a tongue-shaped calcaneal fracture treated using a cylindrical unidirectional porous β-tricalcium phosphate artificial bone (Affinos®, Kurare co Ltd., Hyougo, Japan) to surgically repair bone defects after reduction. The bone defect is often observed when fracture is reduced in calcaneal fracture. There were significant bone defects, which were then fixed using Affinos® (forming a cylindrical shape block; diameter 10 mm x height 20 mm) to support the bone fragment, an artificial β-tricalcium phosphate bone with a porosity of 57 % (pore size 25-300 μm), characterized by a novel unidirectional porous structure. Postoperative early rehabilitation started with partial load from 5 weeks after surgery and was full weight bearing at 9 weeks after surgery. There was no correction loss and good bone fusion was obtained. By 12 months postoperatively, patients were able to be walking without pain and absorption and bone fusion around the artificial bone were observed maintaining the morphology immediately after reduction. The result was a good clinical result of one excellent (92 points) and two good (81 and 84 points) 1 year after surgery in the postoperative AOFAS Ankle-Hindfoot Scale.

Conclusion: Affinos® has a frost-like structure, which endows it with good tissue invasive properties because of the capillary effect. Moreover, it has excellent osteoconduction capability. In these 3 cases, Affinos® showed good strength, affinity, absorption, and bone substitution in a tongue-shaped calcaneal fracture. Further prospective studies are required to confirm our findings.