Allogenic Cancellous Bone versus Injectable Bone Substitute for Endoscopic Treatment of Simple Bone Cyst and Intraosseous Lipoma of the Calcaneus and Is Intraosseous Lipoma a Developmental Stage of a Simple Bone Cyst?

Simple bone cysts (SBCs) and intraosseous lipoma (IOL) of the calcaneus are rare tumor entities that are primarily diagnosed due to unspecific heel pain, incidental findings, or rarely due to pathological fractures. Compared to traditional open tumor resections, endoscopic resection of these benign tumors aims to minimize surgical morbidity and maximize surgical efficiency without compromising safety. Grafting is regularly performed to reduce the risk of recurrence and stimulate osseous consolidation of the lytic lesion. As the incidence is low and treatment strategies are heterogeneous, there is no clear consensus for the treatment of simple cysts or intraosseous lipomas of the calcaneus. The objectives of this study are (a) to present medium to long-term results after endoscopic resection and grafting with allogenic cancellous bone or bioresorbable hydroxyapatite and calcium sulfate cement, and (b) to add further evidence to the discussion of whether calcaneal SBC and IOL are the same entity at different developmental stages. Between 2012 and 2019, a total of 25 benign bone tumors consisting of 17 SBCs and 8 IOLs were treated by A.T. with endoscopic resection and grafting, comprising the largest cohort to date. For grafting, 12 patients received allogenic cancellous bone (group A) and 13 patients received injectable bone substitute (group B). Pre- and postoperative imaging using plain X-rays and MRI was retrospectively analyzed with a mean follow-up time of 24.5 months to assess tumor size, osseous consolidation (modified Neer classification), and tumor recurrence. A retrospective chart analysis focusing on adverse intra- and perioperative events and other complications associated with the surgical procedure was performed using the modified Clavien-Dindo classification (CD1-3). A total of 12/13 cases with allogenic bone grafting showed a Neer Type 1 osseous healing of the tumorous lesion after endoscopic resection, whereas only 5/11 cases with injectable bone substitute showed sufficient healing (types 1 and 2). There were three recurrent cysts (Neer 4) and two persistent cysts (Neer 3) after using injectable bone substitute. Two CD1 complications were observed in group A (prolonged wound drainage, sural neuritis) and eight complications were observed in group B (6× CD1, 2× CD3). At least two IOLs diagnosed preoperatively using MRI were ultimately identified as SBCs upon histopathologic examination. Allogenic cancellous bone grafting after endoscopic resection of calcaneal SBC or IOL showed a very low rate of complications and no tumor recurrence in our series. On the other hand, depending on the material used, injectable bone substitute showed a high rate of "white-out" (excessive drainage), resulting in multiple complications such as prolonged wound healing, insufficient permanent defect filling, recurrence, and revision surgery. Over time, calcaneal SBC may transform into IOL, exhibiting distinct features of both entities simultaneously during ossoscopy and histopathological analysis.

In vivo study of bovine hydroxyapatite-gelatin-hydroxypropyl methylcellulose with alendronate as injectable bone substitute composite in osteoporotic animal model

The injectable bone substitute (IBS) is a self-setting local drug delivery system that adjusts the shape of the bone gap in the fracture. This study aimed to examine the effectiveness of IBS composites of bovine hydroxyapatite (BHA) and alendronate (Ale) in accelerating bone growth in osteoporotic rats. IBS was made by mixing BHA with gelatin 5%, hydroxypropyl methylcellulose (HPMC) 2%, and Ale 10%. The physical properties of IBS were viscosity, injectability, and density tests. Twenty-four female Wistar rats were divided into four groups. After 8 weeks, 2 mm gap was made in the right femur of all rats and filled with IBS. The healing process was observed after 6 weeks with X-ray imaging and H and E staining. The obtained results showed viscosity, injectability, and density value of IBS from 30.4 to 39.4 dPa.s, 98.22%-98.64%, and 0.6325-0.8409 g/cm³, respectively. X-ray imaging and histology results proved the condition of osteoporosis in rats with ovariectomy. The addition of BHA-Gel-HPMC-Ale significantly affected the number of osteoblasts, osteocytes, and osteoclasts (P < 0.05). After 45 days of observation, the addition of BHA-Gel-HPMC-Ale showed the highest mean number of osteoblasts, osteocytes, and osteoclasts, which were 25.00 ± 3.00, 64.33 ± 11.15, and 5.67 ± 0.58 compared to BHA-Gel-HPMC and positive control groups. The BHA-Gel-HPMC-Ale IBS has the potential to reverse osteoporosis. Nevertheless, the underlying potential of these biomaterials to reverse osteoporosis needs further research.

Early-stage bone regeneration of hyaluronic acid supplemented with porous 45s5 bioglass-derived granules: an injectable system

In the present study, an injectable bone substitute system which utilized porous bioglass (BG)-derived granules supplemented with hyaluronic acid (Hya), was evaluated. Hya plays ultimate role in wound healing, promoting cell motility. The BG were synthesized by a simple and low sintering temperature process without any foreign phase incorporation. Furthermore, the physical properties in the porous scaffold were optimized to investigate thein vitroandin vivoperformance. The porous BG60 scaffolds system showed excellent bioactivity in anin vitrosimulated body fluid test in which the ions dissolved from the composite materials influenced apatite growth, countered the acidic pH, and increased material degradation. In anin vitrostudy with pre-osteoblasts cells (MC3T3-E1), the porous scaffold supported cell adhesion and proliferation. A post-implantation study conducted in femoral defects showed implant degradation and surprisingly fast bone formation just after 2 weeks of implantation. Initialin vivodegradation of Hya promotes releasing ions which regulates the bone forming cells, clues to tissue repair, and regeneration. On the other hand it also prevent the scattering of BG granule after grafting at implant site. The faster dissolution of the porous BG scaffold increased the resorption of the composite material and hence, facilitated bone tissue regeneration. Our findings suggest that the porous BG scaffold could potentially be used as an injectable bone substitute for fast, early bone regeneration applications.

Hydroxyapatite Nanoparticles as Injectable Bone Substitute Material in a Vertical Bone Augmentation Model

AIM

The aim of this in vivo study was to evaluate the utility of bone graft gel containing hydroxyapatite nanoparticles in promoting bone regeneration in a mouse model of vertical bone augmentation.

MATERIALS AND METHODS

Gel implants with high and low viscosity were compared for their bone regenerating ability. Bone formation at 12 weeks and material reactions were observed radiographically and histologically.

RESULTS

Radiological analysis showed that most bone augmentation area in the graft material occurred in the fourth week after surgery regardless of the viscosity of the gel, and then gradually decreased. The volume of bone augmentation area was greater in the high-viscosity implant group than in the low-viscosity implant group at all time points, the difference was statistically significant at 8 and 12 weeks. Histological evaluation indicated that the new bone area was significantly smaller in the high-viscosity implant group.

CONCLUSION

Gelatinous graft materials containing hydroxyapatite nanoparticles were confirmed to be useful in vertical bone augmentation.

Interaction between hydroxypropyl methylcellulose and biphasic calcium phosphate after steam sterilisation: capillary gas chromatography studies

The purpose of this study was to check the chemical stability of an injectable bone substitute (IBS) composed of a 50/50 w/w mixture of 2.92% hydroxypropyl methylcellulose (HPMC) solution in deionized water containing biphasic calcium phosphate (BCP) granules (60% hydroxyapatite/40% beta-tricalcium phosphate w/w). After separation of the organic and mineral phases, capillary gas chromatography (GC) was used to study the possible modification of HPMC due to the contact with BCP granules following steam sterilisation and 32 days storage at room temperature. HPMC was extracted from IBS in aqueous medium, and a dialytic method was then used to extract calcium phosphate salts from the HPMC. The percentage of HPMC extracted from BCP was 98.5%+/-0.5%, as measured by UV. GC showed no chemical modifications after steam sterilisation and storage.

In vitro evaluation of a new injectable calcium phosphate material

The purpose of this study was to develop an injectable bone substitute (IBS) for percutaneous orthopedic surgery. The multiphasic material used was composed of a 2% aqueous solution of methylhydroxypropylcellulose (MHPC) and biphasic calcium phosphate (BCP, 60% hydroxyapatite and 40% beta-tricalcium phosphate) in which MHPC served as the carrier for 80-200 microm of BCP granules. The best BCP/polymer ratio was determined by the rheological properties and higher BCP content of the material. Steam sterilization was more effective than gamma irradiation in maintaining the stability of the mixture and conserving its physiochemical and mechanical properties. The in vitro biocompatibility of the composite was checked by direct-contact cytotoxicity and cell-proliferation assays. A preliminary in vivo test was performed in the rabbit using intraosseous implantations in the femoral epiphysis. Histological analysis was done after 1, 2, 4, and 10 weeks. Bone ingrowth into the IBS, in close association with BCP granules, was observed after 1 week and increased regularly from the surface inward at 2, 4, and 10 weeks. At the same time, smaller BCP granules (less than 80 microns in diameter) were degraded and resorbed. This injectable biomaterial proved suitable for cavity filling. The water solubility and viscosity of the polymer allow cells to recolonize, with in situ bonding of the mineral phase.