Unidirectional Porous β-Tricalcium Phosphate: A New Bone Filling Substitute for Treatment of Distal Radius Fracture in the Elderly Population

Clinical Application of Unidirectional Porous Hydroxyapatite to Bone Tumor Surgery and Other Orthopedic Surgery

Unidirectional porous hydroxyapatite (UDPHAp) was developed as a remarkable scaffold characterized by a distinct structure with unidirectional pores oriented in the horizontal direction and connected through interposes. We evaluated the radiographic changes, clinical outcomes, and complications following UDPHAp implantation for the treatment of bone tumors. Excellent bone formation within and around the implant was observed in all patients treated with intralesional resection and UDPHAp implantation for benign bone tumors. The absorption of UDPHAp and remodeling of the bone marrow space was observed in 45% of the patients at a mean of 17 months postoperatively and was significantly more common in younger patients. Preoperative cortical thinning was completely regenerated in 84% of patients at a mean of 10 months postoperatively. No complications related to the implanted UDPHAp were observed. In a pediatric patient with bone sarcoma, when the defect after fibular resection was filled with UDPHAp implants, radiography showed complete resorption of the implant and clear formation of cortex and marrow in the resected part of the fibula. The patient could walk well without crutches and participate in sports activities. UDPHAp is a useful bone graft substitute for the treatment of benign bone tumors, and the use of this material has a low complication rate. We also review and discuss the potential of UDPHAp as a bone graft substitute in the clinical setting of orthopedic surgery.

Retrospective Comparative Study of Clinical Outcomes and Cost-Effectiveness with Bone Substitutes on Volar Locking Plate Fixation of Unstable Distal Radial Fractures in the Elderly

Background: This multicenter retrospective study aimed to compare clinical outcomes and cost-effectiveness with bone substitutes on volar locking plate (VLP) fixation of unstable distal radial fractures (DRF) in the elderly. Methods: The data of 1,980 patients of ≥65 years of age who underwent surgery for the DRF with a VLP in 2015-2019 were extracted from a database (named TRON). Patients lost to follow-up or who received autologous bone grafting were excluded. The patients (n = 1,735) were divided into the VLP fixation alone (Group VLA) and VLP fixation with bone substitutes (Group VLS). Propensity score matching of background characteristics (ratio, 4:1) was performed. The modified Mayo wrist scores (MMWS) were evaluated as clinical outcomes. The implant failure rate, bone union rate, volar tilt (VT), radial inclination (RI), ulnar variance (UV) and distal dorsal cortical distance (DDD) were evaluated as radiologic parameters. We also compared the initial surgery cost and total cost for each group. Results: After matching, the backgrounds of Groups VLA (n = 388) and VLS (n = 97) were not significantly different. The MMWS values of the groups were not significantly different. Radiographic evaluation revealed no implant failure in either group. Bone union was confirmed in all patients in both groups. The VT, RI, UV and DDD values of the groups were not significantly different. The initial surgery cost and total cost in the VLS group were significantly higher than those in the VLA group ($3,515 vs. $3,068, p < 0.001). Conclusions: In patients of ≥65 years of age with DRF, the clinical and radiological outcomes of VLP fixation with bone substitutes did not differ from those of VLP fixation alone, yet the additional use of bone augmentation was associated with higher medical costs. The indications for bone substitutes should be more strictly considered in the elderly with DRF. Level of Evidence: Level IV (Therapeutic).

Unidirectional porous beta-tricalcium phosphate and hydroxyapatite artificial bone: a review of experimental evaluations and clinical applications

In Japan, where allograft bone transplantation is not widespread, prospects for artificial bones are very high. Therefore, artificial bones with various compositions, porous structures, and porosities have been developed and employed for clinical use. Both Affinos^® and Regenos^® (made of beta-tricalcium phosphate and hydroxyapatite, respectively) are artificial bones with a unique unidirectional porous structure, in which pores with a diameter suitable for tissue penetration (25–300 μm) are aligned in one direction. The unidirectional porous structure allows rapid penetration of blood deep into the materials by a capillary effect. In animal experiments, Affinos^® showed well-balanced resorption and was replaced with the host’s own bone from an early stage after implantation and new bone formation and remodeling were observed in the cortical bone and medullary cavity. When implanted for clinical situation, resorption from an early stage and good replacement with the patient’s own bone were also observed. Regenos^® has an internal osteon-like material and a vascular-like structure that is maintained within the pores even after long-term implantation, as noted in an animal experiment. When implanted for clinical situation, good osteoconductivity was observed from an early stage of implantation. In addition, the material was observed to be slowly absorbed over time in some cases. We have discussed the beneficial effects of combining teriparatide and platelet-rich plasma impregnation and the potential prospects of these artificial bones.