Octacalcium Phosphate/Gelatin Composite (OCP/Gel) Enhances Bone Repair in a Critical-sized Transcortical Femoral Defect Rat Model.

BACKGROUND: Bone grafting is widely used to treat large bone defects. A porous composite of a bioactive octacalcium phosphate material with gelatin sponge (OCP/Gel) has been shown to biodegrade promptly and be replaced with new bone both in animal models of a membranous bone defect and a long bone defect. However, it is unclear whether OCP/Gel can regenerate bone in more severe bone defects, such as a critical-size transcortical defect. QUESTIONS/PURPOSES: Using an in vivo rat femur model of a standardized, transcortical, critical-size bone defect, we asked: Compared with a Gel control, does OCP/Gel result in more newly formed bone as determined by (1) micro-CT evaluation, (2) histologic and histomorphometric measures, and (3) osteocalcin staining and tartrate-resistant acid phosphatase staining? METHODS: Thirty-four 12-week-old male Sprague-Dawley rats (weight 356 ± 25.6 g) were used. Gel and OCP/Gel composites were prepared in our laboratory. Porous cylinders 3 mm in diameter and 4 mm in height were manufactured from both materials. The OCP/Gel and Gel cylinders were implanted into a 3-mm-diameter transcortical critical-size bone defect model in the left rat femur. The OCP/Gel and Gel were randomly assigned, and the cylinders were implanted. The biological responses of the defect regions were evaluated radiologically and histologically. At 4 and 8 weeks after implantation, CT evaluation, histological examination of decalcified samples, and immunostaining were quantitatively performed to evaluate new bone formation and remaining bone graft substitutes and activity of osteoblasts and osteoclast-like cells (n = 24). Qualitative histological evaluation was performed on undecalcified samples at 3 weeks postimplantation (n = 10). CT and decalcified tissue analysis was not performed blinded, but an analysis of undecalcified specimens was performed under blinded conditions. RESULTS: Radiologic analysis revealed that the OCP/Gel group showed radiopaque regions around the OCP granules and at the edge of the defect margin 4 weeks after implantation, suggesting that new bone formation occurred in two ways. In contrast, the rat femurs in the Gel group had a limited radiopaque zone at the edge of the defect region. The amount of new bone volume analyzed by micro-CT was higher in the OCP/Gel group than in the Gel group at 4 and 8 weeks after implantation (​​4 weeks after implantation: OCP/Gel versus Gel: 6.1 ± 1.6 mm 3 versus 3.4 ± 0.7 mm 3 , mean difference 2.7 [95% confidence interval (CI) 0.9 to 4.5]; p = 0.002; intraclass correlation coefficient [ICC] 0.72 [95% CI 0.29 to 0.91]; 8 weeks after implantation: OCP/Gel versus Gel: 3.9 ± 0.7 mm 3 versus 1.4 ± 1.1 mm 3 , mean difference 2.5 [95% CI 0.8 to 4.3]; p = 0.004; ICC 0.81 [95% CI 0.47 to 0.94]). Histologic evaluation also showed there was a higher percentage of new bone formation in the OCP/Gel group at 4 and 8 weeks after implantation (​​4 weeks after implantation: OCP/Gel versus Gel: 31.2% ± 5.3% versus 13.6% ± 4.0%, mean difference 17.6% [95% CI 14.2% to 29.2%]; p < 0.001; ICC 0.83 [95% CI 0.53 to 0.95]; 8 weeks after implantation: OCP/Gel versus Gel: 28.3% ± 6.2% versus 9.5% ± 1.9%, mean difference 18.8% [95% CI 11.3% to 26.3%]; p < 0.001; ICC 0.90 [95% CI 0.69 to 0.97]). Bridging of the defect area started earlier in the OCP/Gel group than in the Gel group at 4 weeks after implantation. Osteocalcin immunostaining showed that the number of mature osteoblasts was higher in the OCP/Gel group than in the Gel group at 4 weeks (OCP/Gel versus Gel: 42.1 ± 6.5/mm 2 versus 17.4 ± 5.4/mm 2 , mean difference 24.7 [95% CI 16.2 to 33.2]; p < 0.001; ICC 0.99 [95% CI 0.97 to 0.99]). At 4 weeks, the number of osteoclast-like cells was higher in the OCP/Gel composite group than in the Gel group (OCP/Gel versus Gel: 3.2 ± 0.6/mm 2 versus 0.9 ± 0.4/mm 2 , mean difference 2.3 [95% CI 1.3 to 3.5]; p < 0.001; ICC 0.79 [95% CI 0.35 to 0.94]). CONCLUSION: OCP/Gel composites induced early bone remodeling and cortical bone repair in less time than did the Gel control in a rat critical-size, transcortical femoral defect, suggesting that OCP/Gel could be used as a bone replacement material to treat severe bone defects. CLINICAL RELEVANCE: In a transcortical bone defect model of critical size in the rat femur, the OCP/Gel composite demonstrated successful bone regeneration. Several future studies are needed to evaluate the clinical application of this interesting bone graft substitute, including bone formation capacity in refractory fracture and spinal fusion models and the comparison of bone strength after repair with OCP/Gel composite to that of autologous bone.

Impacts of external rotators and the ischiofemoral ligament on preventing excessive internal hip rotation: a cadaveric study.

BACKGROUND: This study examined the biomechanics of preventing excessive internal hip joint rotation related to the hip flexion angle. METHOD: An intramedullary nail with a circular plate equipped with a protractor was installed in the femur of nine normal hips. The circular plate was pulled by 3.15 Nm of force in the internal rotation direction. The external rotators were individually resected, finally cutting the ischiofemoral ligament. The cutting order of the external rotators differed on each side to individually determine the internal rotation resistance. The external rotators were resected from the piriformis to the obturator externus in the right hips and the reverse order in the left hips. Traction was performed after excising each muscle and ischiofemoral ligament. Measurements were taken at 0°, 30°, and 60° of hip flexion, and the differences from baseline were calculated. RESULTS: For the right hip measurements, the piriformis and ischiofemoral ligament resection significantly differed at 0° of flexion (p = 0.02), each external rotator and the ischiofemoral ligament resections significantly differed at 30° of flexion (p < 0.01), and the ischiofemoral ligament and piriformis and inferior gemellus resections significantly differed at 60° of flexion (p = 0.04 and p = 0.02, respectively). In the left hips, the ischiofemoral ligament and obturator externus, inferior gemellus, and obturator internus resections significantly differed at 0° of flexion (p < 0.01, p < 0.01, and p = 0.01, respectively), as did each external rotator and the ischiofemoral ligament resections at 30° of flexion (p < 0.01). CONCLUSION: The ischiofemoral ligament primarily restricted the internal rotation of the hip joint. The piriformis and obturator internus may restrict internal rotation at 0° and 60° of flexion.

Effect of interleukin-17A inhibitor in Japanese patients with psoriatic arthritis compared with tumor necrosis factor-alpha inhibitor.

OBJECTIVES: The patient of severe psoriatic arthritis (PsA) is mainly treated with oral methotrexate, ciclosporin, and anti-tumor necrosis factor-alpha inhibitors (TNFi). Recently, anti-interleukin-17A inhibitors (IL-17Ai) have been used in the treatment of PsA. This study aimed to evaluate the efficacy and safety of IL-17Ai in Japanese patients with PsA compared with those of TNFi. METHODS: This was a longitudinal and retrospective study. The study population included 31 Japanese patients with PsA. All enrolled patients fulfilled the Classification Criteria for Psoriatic Arthritis. All patients were treated with TNFi or IL-17Ai. The assessed clinical manifestations were C-reactive protein (CRP)-based Disease Activity Score in 28 Joints (DAS28-CRP), disease activity in psoriatic arthritis (DAPSA), 20% achievement of American College of Rheumatology core set, swollen joint count (SJC), tender joint count (TJC), and visual analog scale (VAS). Functional ability of patients with PsA was analyzed using the modified health assessment questionnaire (mHAQ) score. We evaluated the parameters at baseline and weeks 12, 24, and 52. RESULTS: The change in SJC, TJC, VAS, mHAQ, and DAPSA had no significant difference at weeks 12, 24, and 52. The improvements of CRP and DAS28-CRP were significantly higher in TNFi group only at week 12. The biologics retention rate was significantly higher in TNFi group by the log-rank test. No critical adverse events occurred. CONCLUSIONS: Our study presented that IL-17Ai had treatment effects comparable to TNFi. IL-17Ai might have the potential to become an alternative to the previous drug, but more large-scale studies are expected.

Impact of simultaneous hydrolysis of OCP and PLGA on bone induction of a PLGA-OCP composite scaffold in a rat femoral defect.

Effect of the simultaneous hydrolysis of octacalcium phosphate (OCP) and poly (lactic-co-glycolic acid) (PLGA) was investigated on its osteoconductivity. PLGA soaked in phosphate buffered saline with 0%, 20%, and 40% OCP at 37°C for eight weeks indicated that when the OCP dose was increased, 1) the weight loss of PLGA increased, 2) the glass transition temperature of the PLGAs decreased, 3) the saturation degree in the saline moved to nearly saturated condition with respect to hydroxyapatite (HA) but was undersaturated with respect to OCP, and 4) OCP tended to convert to HA by X-ray diffraction and Fourier transform infrared spectroscopy. OCP/PLGA composites of 20% and 40% with more than 92% porosity were produced by combining OCP granules with 1,4-dioxane-solubilizing PLGA followed by lyophilization and then subjected to four- and eight-week in vivo implantation tests in 3 mm diameter rat femora defects. Microfocus X-ray computed tomography, histochemical and histomorphometric analyses showed that while bone formation was very limited with PLGA implantation, the extent of repair tended to increase with increasing OCP content in the PLGA, coupled with PLGA degradation, and bridge the defects with trabecular bone. Tartrate-resistant acid phosphatase-positive osteoclast-like cells were accumulated four weeks after implantation, while osteocalcin-positive osteoblastic cells appeared later at eight weeks, especially in 40% OCP/PLGA. These results suggest that OCP hydrolysis, with phosphate ion release, enhances PLGA hydrolysis, probably through the acid catalysis function of the protons supplied during the hydrolysis of OCP, thereby inducing PLGA biodegradation and new bone formation in the femoral defects. STATEMENT OF SIGNIFICANCE: Octacalcium phosphate (OCP) enhances osteoblasts and osteocytes differentiations during its hydrolysis accompanying inorganic ions exchange in this material. The present study found that the advancement of OCP hydrolysis under physiological conditions had an effect on poly (lactic-co-glycolic acid) (PLGA) degradation through its chemical environmental change around OCP, which was ascertained by the decreases in weight loss and glass transition temperature of PLGA with increasing the dose of OCP co-present. Rat femur-penetrated standardized severe defects were found to repair through bridging the cortical region defect margin. PLGA degradation could be enhanced through an acid catalyst function by protons derived from inorganic phosphate (Pi) ions through OCP hydrolysis under bone forming condition, resulting in showing a prominent bone regenerative capacity in OCP/PLGA composite materials.

Chemical Stability-Sensitive Osteoconductive Performance of Octacalcium Phosphate Bone Substitute in an Ovariectomized Rat Tibia Defect.

The purpose of this study was to investigate whether the chemical condition of osteoporotic serum affects the chemical stability of octacalcium phosphate (OCP) and its osteoconductive property. The in vitro chemical dissolution in osteoporotic ovariectomized (OVX)-simulated conditions was analyzed. OCP and its composite form with gelatin (OCP/Gel), containing specific amounts of OCP (either 17% or 44% by weight), were used as experimental materials. The degrees of supersaturation (DS) of the OVX-simulated buffer solutions, containing distinct inorganic phosphate (Pi) ion concentrations, after immersing OCP or OCP/Gel, were determined. The rod-shaped OCP/Gel was then implanted into the OVX and Sham rat tibia defects, exhibiting a similar shape and size, and assessed at 4, 8, and 12 weeks. Increasing Pi concentration in OVX-simulated buffer solution increased the DS, with respect to OCP, upon the introduction of OCP and 44% OCP/Gel, but decreased the DS to a slightly saturated condition with 17% OCP/Gel, indicating that increasing the OCP in the Gel matrix tends to inhibit the hydrolysis of OCP into hydroxyapatite (HA). Histomorphometric analyses of bone formation and the appearance of osteoblasts and osteoclast-like cells, together with OCP resorption, confirmed that while 44% OCP/Gel showed higher bone formation than 17% OCP/Gel at intramedullary bone defect sites in Sham rat tibia, both OCP/Gels tended to enhance cortical bone formation in the OVX group, concomitant with the higher resorption of OCP within 17% OCP/Gel. The appearance of osteoclast-like cells in the OVX group increased as the OCP dose decreased from 44% to 17% in the Gel matrix, with an approximately 4 times higher bone formation rate, 8-12 weeks after the implantation. Additional in vitro assays showed that bone marrow mesenchymal stem cells isolated from OVX and wild-type (WT) rats treated with OCP had similar proliferation and differentiation rates, up to 21 days. These results show that OCP can enhance cortical bone repair even in osteoporotic bone if suitable thermodynamic metastable dissolution conditions are provided in relation to the mass of OCP.