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Unidirectional porous hydroxyapatite (UDPHAp) is an artificial bone substitute with a unique microstructure consisting of 100–300-µm oval pores that present the material unidirectionally. UDPHAp has a compression strength of 14 MPa and a porosity of 75%, which promotes cell migration and capillary formation within the material. Despite these advantageous properties, bone remodeling and bone formation with UDPHAp remain unclear. To examine long-term remodeling and differences in bone formation based on the defect site, trapezoidal prism-shaped UDPHAp blocks were implanted into rectangular-shaped cortical bone defects in the proximal tibia of Japanese white rabbits. Histological analysis performed at 52 and 104 weeks after implantation revealed that bone and capillaries had formed within the implanted UDPHAp material. Bone formed within the UDPHAp implanted in the cortical defect of rabbit tibia and remodel up to two years. The percentage of new bone area within UDPHAp was larger in cortical lesions than that in medullary lesions. These findings suggest that UDPHAp is a promising material for the repair of non-critical-sized cortical bone defects.

We examined the balance between bone formation and material resorption in β-tricalcium phosphate, with unidirectional pores (porosity of 57%) and micropore structure. Using an animal bone defect model, rapid bone formation reached to the center of the material, while the material remained at the same period. Histomorphometric analysis showed that the sum total area of formed bone and material gradually increased with time throughout the experiment. These results indicate that the balance between bone formation and material resorption in this material is satisfactory.

Unidirectional porous hydroxyapatite (UDPHAp) bone substitute comprises a microstructure of cross‐sectionally oval pores with diameters ranging from 30 to 300 µm. Bone remodeling within the UDPHAp is expected upon implantation into bone; however, the mechanism and factors influencing this bone growth remain unclear. The objectives of the present study were to assess the vasculature and microstructure of newly formed bone and to determine how bone formation is affected by load transfer and UDPHAp pore size. Formation of osteon‐like structures, defined by the presence of lacunae, canaliculi and a central lumen containing capillaries, was observed within the implanted UDPHAp material in all animals after six weeks. The number of osteocytes and osteon‐like structures in areas adjacent to the cortex of recipient bone was significantly higher than in areas next to the medullary cavity throughout the recovery period. Notably, osteon‐like structures tended to form in smaller diameter pores. Continuous bone remodeling might be promoted by the rapid formation of unidirectional capillaries and the osteocyte lacunae‐canalicular system. Load transfer and smaller pore size could positively affect cortical bone regeneration. © 2018 The Authors Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2665–2672, 2018.

The single-joint HAL provided safe and effective assistance to scapular plane shoulder flexion-extension among healthy adults.

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Five shoulders in four patients affected by advanced osteonecrosis of the humeral head were treated with autologous concentrated bone marrow grafting. Bone marrow sample was aspirated from the iliac crests, concentrated by a centrifugation technique, and injected into the necrotic site. The shoulders were evaluated radiologically with X-ray scoring and clinically with measurement of range of motion and pain score (visual analogue scale, VAS). The mean follow-up period was 49.4 (range, 24–73) months. The concentration ratio of nucleated cells was calculated and the number of transplanted mesenchymal stem cells (MSC) was estimated by a colony-forming assay. All four shoulders with stage 3 disease achieved joint sparing. One shoulder with stage 4 disease required replacement surgery. Clinical evaluation of the spared joints showed improvement in range of motion in two cases and deterioration in two cases. VAS scores were 0 after surgery in three cases. The mean concentration ratio was 2.73, and the mean number of transplanted MSC was 1125. The outcomes of autologous concentrated bone marrow grafting for advanced osteonecrosis of the humeral head were varied. Further research is needed to determine the effectiveness and the indications of the present surgery.

'Asymptomatic MCL injury on MRI' had little correlation to ligament dysfunction. It might represent the transition period to MCL thickening called "adaptation."