Intramuscular Pocket Research Articles

“Intramuscular Breast Augmentation in Secondary Mastopexy Augmentation.”

Background: Breast augmentation with implants is one of the most performed aesthetic surgical procedures performed worldwide. We describe this new option for breast implant secondary procedures, the intra pectoralis major pocket, as a feasible and reproducible surgical technique. Methods: A retrospective chart review was conducted on all patients who underwent revision augmentation or mastopexy augmentation procedure between 2005 and 2022 by the senior author. The intramuscular pocket is dissected between the pectoral muscle fascicles where almost is not bleeding. Results: Patients were followed for an average of 21.5 months. A total of 319 patients underwent revisionary breast augmentation/mastopexies performed by the senior author. Indications for reoperation were based both on specific patient dissatisfaction with their original surgery and surgeon’s physical examination and assessment. In 196 cases we performed the intramuscular pocket. None of the intramuscular had capsular contracture or animation deformity in the follow up period. Conclusions: The intramuscular technique is a valuable and safe technique for secondary breast augmentation.

Biocompatibility and histological responses of eggshell membrane for dental implant-guided bone regeneration.

Guided bone regeneration (GBR) utilizing eggshell membrane (ESM) as a potential biomaterial for dental implant therapy augmentation was explored in this study. ESM, an environmentally friendly waste product, possesses collagen-rich characteristics. The biocompatibility and histological responses of ESM were investigated in a rat model. Twelve young adult Wistar rats were used in this study. ESM samples were implanted in subcutaneous and intramuscular pockets, and samples were collected at 48 hours, 4 weeks, and 8 weeks post-implantation. Histological analysis revealed the changes in ESM over time. Results showed that ESM maintained its structural integrity, induced a moderate cellular response, and exhibited slow degradation, indicating potential biocompatibility. However, the lack of organized collagen arrangement in ESM led to the formation of irregular and polymorphic spaces, allowing cell migration. Encapsulation of ESM by newly proliferating collagen fibers and multinucleated giant cells was observed at later time points, indicating a foreign body reaction. Crosslinking might improve its performance as a separation membrane, as it has the potential to resist enzymatic degradation and enhance biomechanical properties. In conclusion, ESM demonstrated biocompatibility, slow degradation, and lack of foreign body reaction. While not suitable as a complete separation membrane due to irregular collagen arrangement, further research involving crosslinking could enhance its properties, making it a viable option for guided bone regeneration applications in dental implant therapy. This study highlights the potential of repurposing waste materials for medical purposes and underscores the importance of controlled collagen structure in biomaterial development.

Pre-cultured, cell-encapsulating fibrin microbeads for the vascularization of ischemic tissues.

There is a significant clinical need to develop effective vascularization strategies for tissue engineering and the treatment of ischemic pathologies. In patients afflicted with critical limb ischemia, comorbidities may limit common revascularization strategies. Cell-encapsulating modular microbeads possess a variety of advantageous properties, including the ability to support prevascularization in vitro while retaining the ability to be injected in a minimally invasive manner in vivo. Here, fibrin microbeads containing human umbilical vein endothelial cells (HUVEC) and bone marrow-derived mesenchymal stromal cells (MSC) were cultured in suspension for 3 days (D3 PC microbeads) before being implanted within intramuscular pockets in a SCID mouse model of hindlimb ischemia. By 14 days post-surgery, animals treated with D3 PC microbeads showed increased macroscopic reperfusion of ischemic foot pads and improved limb salvage compared to the cellular controls. Delivery of HUVEC and MSC via microbeads led to the formation of extensive microvascular networks throughout the implants. Engineered vessels of human origins showed evidence of inosculation with host vasculature, as indicated by erythrocytes present in hCD31+ vessels. Over time, the total number of human-derived vessels within the implant region decreased as networks remodeled and an increase in mature, pericyte-supported vascular structures was observed. Our findings highlight the potential therapeutic benefit of developing modular, prevascularized microbeads as a minimally invasive therapeutic for treating ischemic tissues.

90. Nanoroughened microstructured orthopedic implant surfaces induce osteogenesis via soluble signaling factors produced by MSCs

BACKGROUND CONTEXT There is a growing clinical need to create implants with material properties that promote accelerated osseointegration and reduced recovery time for interbody fusion healing. We have shown that machined Ti-based implants possessing biomimetic surface topographies can direct osteoblast differentiation of multipotent bone marrow stromal cells (MSCs) in vitro and improve osseointegration in vivo in both animals and in humans following dental implant placement. PURPOSE This study examined the hypothesis that MSCs grown on nanotextured microstructured Ti6Al4V surfaces produce factors that regulate osteogenic differentiation of MSCs not on the surface. STUDY DESIGN/SETTING Not applicable. PATIENT SAMPLE Not applicable. OUTCOME MEASURES Not applicable. METHODS Ti6Al4V discs were grit-blasted and acid-etched, producing complex topography at the macro/micro/nanoscale (MMN; Medtronic/Titan Spine). All cultures were grown in MSC growth media (GM). Co-cultures were used to examine paracrine effects of factors released by human MSCs cultured on MMN surfaces. MSCs were grown on tissue culture polystyrene (TCPS) or MMN discs in 24-well plates. At 24 hours, inserts containing MSCs were placed into the wells and cultured in GM for 7 days, then moved to fresh GM for 24 hours. Alternatively, MSCs were cultured on MMN surfaces and TCPS for 7 days. Inserts with MSCs were added to the wells on day 7 and the co-culture was incubated for another 4 days. Inserts were moved on day 11 and cultured for 24 hours. In each experiment, a group of MMN discs received GM+15µg/mL BMP2 blocking antibody (abBMP2). BMP2, OPN, OPG, OCN, IL6, and VEGF-A in the conditioned media (CM) were assayed by ELISA and normalized to DNA. Athymic mice were divided into 3 groups: inactive demineralized bone matrix (iDBM), iDBM+rhBMP2 (MMN-CM concentration), and iDBM+MMN-CM proteins. MMN-CM was derived by culturing MSCs on MMN surfaces for 10 days and lyophilizing the CM from days 5-10. Gel capsules were implanted bilaterally into intramuscular pockets created in the hind limbs (N=8 capsules/group). Legs were harvested at 35 days. Bone formation was assessed by micro-CT and histomorphometry. RESULTS MSCs grown directly on MMN discs and on inserts above MMN discs increased production of OCN, OPN, BMP2, and VEGF-A compared to MSCs above TCPS, MMN discs+abBMP2, and insert control. Blocking BMP2 after surface mediated differentiation reduced OCN, OPN, and BMP2 compared to MMN groups. Total DNA content was increased on MMN discs+abBMP2. Micro-CT revealed greater mineralized tissue in MMN-CM groups compared to iDBM and iDBM+BMP2. There was more live bone in the MMN-CM group compared to iDBM. CONCLUSIONS MSCs cultured on nanoroughened microtextured biomimetic Ti6Al4V surfaces differentiate and produce local factors that can induce MSC differentiation above the surface through paracrine signaling factors such as BMP2. Reducing BMP2 function via abBMP2 inhibits MSC differentiation in contact with the surface and above the surface, indicating that BMP2 produced by cells on the surface is involved in the surface-dependent osteogenic differentiation process. Factors produced by the MSCs increased bone formation in a mouse model compared to control and BMP2-only treatment groups, suggesting that the engineered biomimetic surface topography may improve bone formation. FDA DEVICE/DRUG STATUS Interbody Fusion Implants (Approved for this indication)

Chirurgie glutéale secondaire : technique chirurgicale et résultats

The interest in the posterior aspect of the body keeps increasing, thus trigerring an increase in the number of gluteal augmentations with implants, also trigerring a proportional increase in postoperative complications and secondary gluteal surgeries. Nevertheless, there are currently few publications on this subject. The purpose of this study is to identify methods to treat and prevent gluteal augmentation complications. In this study, the author reviews 14 cases of secondary gluteal surgeries. Some patients simply have their implants removed. For others, the solution to get rid of excess skin relies on buttock lifting or the creation of a purse with an elastic thread. A new deeper plane intramuscular pocket surgery can also be performed. Moreover, capsuloplasty is often required to treat malpositions. Finally, a "hybrid or composite augmentation" can be completed by grafting autologous fat into the subcutaneous fat layer in combination with the implants. Out of the 14 secondary gluteal surgery cases, the implants were removed in five cases, eight cases involved deeper insertion of implants and one case with a capsuloplasty; five cases benefited from a hybrid or composite augmentation and two cases of a butt lift. Minor postoperative complications occurred in four cases. A better knowledge of the gluteal area anatomy, a good understanding of the gluteal surgical techniques coupled with a good mastery of the composite or hybrid technique for the gluteal augmentation as well as a good management of malpositions, seromas and delayed healing can enhance secondary gluteal surgery success.

Nanostructured endodontic materials mixed with different radiocontrast agents-biocompatibility study.

The aim of this study was to investigate the biocompatibility of nanostructured materials based on highly active calcium silicates mixed with different radiocontrast agents in comparison to MTA+ using in vitro and in vivo model. Morphology of materials' samples was analyzed using SEM while the phase compositions were identified by XRD. pH values of materials' suspensions were conducted by pH-meter. The cytotoxicity of materials' solutions was tested by MTT test (100, 50, 25 and 12.5 mg/ml). LDH and 3H-thymidine assay were utilized for biocompatibility investigations of materials' eluates (24 h, 7 day and 21 day). Eighteen Guinea pigs were used for intramuscular implantation, as teflon tubes with freshly prepared materials were placed into intramuscular pockets. All samples were composed of round and needle-like particles equally distributed with Ca/Si ratio ~2.7 at%, with the presence of hydrated calcium silicate phases. The pH values of ALBO-MPCA1 and ALBO-MPCA2 were high alkaline, while in case of MTA+ they were lower and continuously declined (p < 0.05). Investigated materials didn't exhibit dose-dependent effect on metabolic activity of L929 cells (p > 0.05). Significant differences in the percentage of cytotoxicity between diluted and undiluted extracts between all tested materials after 24 h and 7 day were noticed (p < 0.05). Increase in L929 cells proliferation was noticed in case of undiluted eluates of ALBO-MPCA1 and ALBO-MPCA2 after 7 day (p < 0.05). There were no statistically significant differences in the intensity of inflammatory response between investigated materials and control group after 60 day (p > 0.05). Evaluation of biocompatibility of both ALBO-MPCA1 and ALBO-MPCA2 indicate their potential clinical use.

Fabrication of Vascularized Bone Flaps with Sustained Release of Recombinant Human Bone Morphogenetic Protein-2 and Arteriovenous Bundle.

It is a common treatment strategy in the clinic to transplant a vascularized bone flap for a large bone defect. But it is difficult for peripheral blood vessels to grow into the central region of a large bone construct. In this study, we fabricated a vascularized bone flap from a three-dimensional (3D)-printed biodegradable poly(lactide-co-glycolide) (PLGA)/β-tri-calcium phosphate (β-TCP) scaffold using the combination of an arteriovenous (AV) bundle and recombinant human bone morphogenetic protein-2 (rhBMP-2). A degradable porous PLGA/β-TCP scaffold was prepared by adopting 3D plotting and a low-temperature deposition technique. rhBMP-2 chitosan microspheres (CMs) were fabricated and loaded into the scaffolds to induce ectopic bone formation. In Group SBV (scaffold+rhBMP-2+vessel), a femoral AV bundle was implanted into the central tunnel of the composite before embedding into intramuscular pockets. In Group SB (scaffold+rhBMP-2), the composite was directly implanted into intramuscular pockets. Bone formation was evaluated by imaging analysis (X-rays and microcomputed tomography) and histological analysis (Hematoxylin and Eosin staining and Masson staining) after 4 and 12 weeks, respectively. Vascularization was also assessed by imaging analysis (Microfil angiography) and histological analysis (CD31 immunohistochemical staining). The 3D-printed PLGA/β-TCP scaffold had good cytocompatibility. Ectopic bone formation in the scaffold could be successfully induced by the controlled release of rhBMP-2 through CMs. Comparing groups SBV and SB, vascularization of the composite was significantly enhanced by AV bundle implantation at 4 and 12 weeks. Moreover, rhBMP-2-induced bone formation was also significantly improved by the AV bundle at 4 and 12 weeks. The AV bundle not only improved vascularization and bone formation of the construct, but also provided a defined vascular axis to connect with the vascular system of the bone defect by microsurgical techniques. It provided a new potential treatment strategy to repair large bone defects, especially for those with low vascular supply.

Qualitative analysis of the viability of autogenous fat grafts grafted in different environments of interstitial pressure. Preliminary results and description of a new experimental model in mini-pigs.

To evaluate the feasibility of an experimental model of autologous fat graft (AFG) in different interstitial pressure (IP) environments. Three mini-pigs(Minipig-BR) with age of 8 months (weight: 25-30 kg) were used. AFG were collected from the bucal fat pad, and grafted in the intramuscular pocket (biceps femoralis muscle). IP model was based on a fusiform ressection followed by primary closure "under tension". A blood pressure catheter located in the intramuscular region connected to a pressure module was applied to quantify IP. The mean operative time was 236 min (210 - 272 min). All the AFG and muscular segments were removed successfully. Average interstitial pressure CP and H were 3 and 10.6 mmHg respectively. The AFG were biopsied for histopathological analysis 30 days after graft. Hematoxylin-eosin staining and immunohistochemical analyzes (TNF-alpha, CD31 and Perilipine with monoclonal antibodies) were employed. The data show that minipigs model could be used as a recipient site for autologous fat graft techniques and allow the development of studies to explore the AFG intake and pathophysiology response.

Abstract: Augmentation Gluteoplasty - the XYZ Technique

INTRODUCTION: A woman with small breasts but proportionate waist and hips still has a feminine body, but one with flat buttocks and large shoulders or narrow hips will never have a totally feminine body, regardless of how beautiful her breasts are. So, the most important detail of a feminine body is the balance of its contour. PURPOSE: The objective of this work is to share our experience performing the XYZ technique for buttocks enhancement described by Raul Gonzales, in 2004. With this technique we can easily insert an implant into the gluteus maximus with no risk of sciatic nerve compression and no limitations in the size of implant. METHODS/TECHNIQUES: The incision is done directly over the intergluteal crease, preserving the sacral cutaneous ligament. After the skin drawing, of an inverted heart, the subcutaneous tissue is undermined just over the muscle fascia till the end of the drawing. Next step is a 6 cm muscle incision in the same direction of the muscle fibers. The undermining should split the muscle at the middle, and the same amount of muscle should be left in front of and behind the implant. The point X is found introducing a finger into the muscle incision 2–3 cm deeper. This is half of the thickness of the muscle and this is our plane of undermining. Point Y is in the iliac crest 5 cm beyond the upper-posterior iliac spine and is our superior limit of undermining. The point Z, the lower limit of the undermining, is reached rotating the underminer from point Y towards the femur trochanter. Usually this pocket is enough to accept relatively large round implants as well as 350 or 400 cc in a medium-sized patient. Once the implants are placed into the pockets the incision is closed from the muscle fascia till the skin, avoiding communication between the intramuscular pocket and the supra-facial subcutaneous one, to avoid seroma formation. RESULTS: We have been using this technique routinely since 2006 in more than 300 patients. CONCLUSION: With this technique we can easily find the 3 stop points of the undermining to insert an implant into the gluteus maximus avoiding the most common complication: the palpable implant for a too shallow pocket in the lateral areas.

Gluteal Augmentation with Silicone Implants: A New Proposal for Intramuscular Dissection.

Gluteoplasty has gained notoriety over the last decades, which has motivated the development of various surgical techniques. Nevertheless, the fear of dissection of the intramuscular plane without direct visualization may inhibit learning and development of gluteal augmentation with implants. Moreover, literature detailing the technical steps of intramuscular dissection for the construction of the implant pocket is scarce. This study presents a new approach to intramuscular dissection for gluteal augmentation with silicone implants, a variation of the conventional surgical technique. We performed a retrospective analysis of a series of 12 female patients submitted to a variation of the intramuscular dissection technique for gluteal augmentation with silicone implants. Data from patients, implants, follow-up time, postoperative complications, and the degree of patient satisfaction were obtained. This technique follows the principle of alternating spatulas to perform the blunt dissection of the implant pocket. In this series, the proposed technique is controlled and safe for intramuscular dissection, which can be used for both experienced and training surgeons. This technique is based on well-known anatomical points and references. We observed that the implant was well positioned and covered, the patients were satisfied with the result, and the number of complications was low. This variation of the intramuscular dissection technique for gluteal augmentation with silicone implants provides an easily reproducible and safe procedure that involves well-controlled technical steps, especially during dissection of the intramuscular pocket. In this series of patients, training surgeons learned faster, results were satisfactory, and the number of complications was low. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

The Osteogenic Potential of Human Nondifferentiated and Pre-differentiated Mesenchymal Stem Cells Combined with an Osteoconductive Scaffold - Early Stage Healing.

Despite the huge research into stem cells and their regenerative properties for bone healing, there are still unanswered questions including the recipient's respond to the presence of the stem cells, the fate of stem cells inside the bone defect and the possible advantage in utilizing pre-differentiated cells. To address these problems, we used human multipotent mesenchymal stromal/stem cells (MSCs), GMP Grade, in a rat model of bone formation. In a "bioreactor concept" approach seven Wistar rats were implanted with 0.2 g of synthetic bone scaffold seeded with 2 × 106 MSCs, seven Wistar rats were implanted with 0.2 g of synthetic bone scaffold seeded with 1 × 106 predifferentiated osteoblasts and 1 × 106 pre-differentiated endothelial cells and 14 Wistar rats were implanted with 0.2 g of synthetic bone scaffold without seeded cells into an intramuscular pocket on the left side of their back. The right side of each rat was used as a control, and 0.2 g of synthetic bone scaffold was implanted into the intramuscular pocket alone. To see the early stage healing the samples were harvested 14 days after the implantation, MSCs were detected by positive DAPI and MTCO2 staining in 43% of all the samples implanted with MSCs, and no inflammation signs were present in any implanted animal. New vessels could be found in both groups implanted with MSCs, but not in the control group of animals. However, hematoxylin-eosin staining could not detect newly created bone within the implant in any of the groups. These results were in line with COLL1 staining, where we could detect positive staining only in three cases, all of which were implanted with un-differentiated MSCs. According to our findings, there were no benefits of using the pre-differentiated of MSC.

Properties and Osteogenicity of Two Calcium Sulfate Materials with Micro or Nano Morphology.

Calcium sulfate dihydrate (CaSO4 x 2H2O, CSD) was widely used as the artificial bone graft. In this study, two kinds of CSD materials were characterized with XRD, TG/DTA, FT-IR, and SEM. They were both composed of CSD. Spherical shape particles were observed for nano-CSD with diameters of 52-300 nm. The micro-CSD were thin sheet particles with dimensions of 5-10 μm. At 56 days post-implantation in vivo, nano-CSD had good tissue compatibility. A frequently used bioactive material DBM, which was the combination of nano-CSD (nano-CSD-DBM) and micro-CSD (micro-CSD-DBM) in a 1:1 weight ratio separately. Composite materials were implanted in intramuscular pockets in nude mouse model. New bone mineralization could be both observed in the surgery site. Collagen I was also widely distributed by immunohistochemistry assay. And new bone area of nano-CSD-DBM was 28 ± 4.6% at 4 weeks post-operation. But new bone area of micro-CSD-DBM was 16 ± 3.7% (less than nano-CSD-DBM). Nano-CSD showed increased degradation rate with obvious anginogenicity. And nano-CSD-DBM showed more excellent bone induction property as bone substitute implant.

Intramuscular Transplantation Improves Engraftment Rates for Esophageal Patient-Derived Tumor Xenografts.

Recently, there has been an increase in the availability of targeted molecular therapies for cancer treatment. The application of these approaches to esophageal cancer, however, has been hampered by the relative lack of appropriate models for preclinical testing. Patient-derived tumor xenograft (PDTX) models are gaining popularity for studying many cancers. Unfortunately, it has proven difficult to generate xenografts from esophageal cancer using these models. The purpose of this study was to improve the engraftment efficiency of esophageal PDTXs. Fresh pieces of esophageal tumors obtained from endoscopic biopsies or resected specimens were collected from 23 patients. The tumors were then coated in Matrigel and transplanted in immunocompromised mice subcutaneously (n = 6) and/or using a novel implantation technique whereby the tumor is placed in a dorsal intramuscular pocket (n = 18). They are then monitored for engraftment. With the novel intramuscular technique, successful engraftment was achieved for all 18 patient tumors. Among these PDTXs, 13 recapitulated the original patient tumors with respect to degree of differentiation, molecular and genetic profiles, and chemotherapeutic response. Lymphomatous transformation was observed in the other five PDTXs. Successful engraftment was achieved for only one of six patient tumors using the classic subcutaneous approach. We achieved a much higher engraftment rate of PDTXs using our novel intramuscular transplant technique than has been reported in other published studies. It is hoped that this advancement will help expedite the development and testing of new therapies for esophageal cancer.

The Shade Procedure: For Lower Lid Deformities

Early procedures designed to address fat herniation deformities in the lower lid relied on resection of herniated orbital fat. In some cases, this approach results in an abnormal depression of the periorbital soft-tissue profile and reduced globe prominence. The shade procedure was developed to address these concerns. Sixty-five patients underwent lower lid blepharoplasty either alone, in combination with upper lid blepharoplasty, or with face lift using the shade technique over the past 11 years. The shade procedure treats the fat herniation contour change by repositioning the fat as an apron over the orbital rim and elevating depressed midface fat and muscle. Essential components for both efficacy and safety relate to developing a symmetric apron of herniated fat and orbital septum; limited dissection (5 to 10 mm) of an intramuscular pocket at the inferior orbital rim; translocation and fixation of the fat apron over the orbital rim; elevation and secure fixation of the superior quadratus and zygomaticus muscle flap to the medial and lateral orbital periosteum and the normal thickness orbital septum; release of the septum and capsulopalpebral fascia from the tarsus; and lateral canthopexy. Two patients developed ectropion postoperatively requiring reoperation. No hematomas, facial nerve palsy, or skin slough occurred. An independent lay rater group judged the operative results to be improved in all cases (average, 4.3 on a five-point Likert scale). The shade procedure should be considered for patients with lower lid fat herniation, particularly when depression at the inferior orbital rim accompanies convex prominence of the lower lid profile.

Osteogenic Potential of Postnatal Skeletal Muscle–Derived Stem Cells Is Influenced by Donor Sex

This study compared the osteogenic differentiation of F-MDSCs and M-MDSCs. Interestingly, M-MDSCs expressed osteogenic markers and underwent mineralization more readily than F-MDSCs; a characteristic likely caused by more osteoprogenitor cells within the M-MDSCs than the F-MDSCs and/or an accelerated osteogenic differentiation of M-MDSCs. Although therapies involving stem cells will require both female and male cells, few studies have investigated whether sex-related differences exist in their osteogenic potential. Here, we compared the osteogenic differentiation of female and male mouse skeletal muscle-derived stem cells (F- and M-MDSCs, respectively), a potential cell source for orthopedic tissue engineering. F- and M-MDSCs were stimulated with bone morphogenetic protein (BMP)4, followed by quantification of alkaline phosphatase (ALP) activity and expression of osteogenic genes. F- and M-MDSCs were also cultured as pellets in osteogenic medium to evaluate mineralization. Single cell-derived colonies of F- and M-MDSCs were stimulated with BMP4, stained for ALP, and scored as either Low ALP+ or High ALP+ to detect the presence of osteoprogenitor cells. F- and M-MDSCs were transduced with a BMP4 retrovirus (MDSC-BMP4 cells) and used for the pellet culture and single cell-derived colony formation assays. As well, F- and M-MDSC-BMP4 cells were implanted in the intramuscular pocket of sex-matched and sex-mismatched hosts, and bone formation was monitored radiographically. When stimulated with BMP4, both F- and M-MDSCs underwent osteogenic differentiation, although M-MDSCs had a significantly greater ALP activity and a larger increase in the expression of osteogenic genes than F-MDSCs. In the pellet culture assay, M-MDSCs showed greater mineralization than F-MDSCs. BMP4 stimulation of single cell-derived colonies from M-MDSCs showed higher levels of ALP than those from F-MDSCs. Similar results were obtained with the MDSC-BMP4 cells. In vivo, F-MDSC-BMP4 cells displayed variability in bone area and density, whereas M-MDSC-BMP4 cells showed a more consistent and denser ectopic bone formation. More bone formation was also seen in male hosts compared with female hosts, regardless of the sex of the implanted cells. These results suggest that M-MDSCs may contain more osteoprogenitor cells than F-MDSCs, which may have implications in the development of cellular therapies for bone healing.

Cross-species Comparison of Ectopic Bone Formation in Biphasic Calcium Phosphate (BCP) and Hydroxyapatite (HA) Scaffolds

Material-induced bone formation reported in canine, bovid, suid, and primate species does not often occur in lagomorph or rodent models. In this study, we test biphasic calcium phosphate and hydroxyapatite- induced bone formation in subcutaneous pockets of mice and intramuscular pockets in rats, rabbits, and dogs. All scaffolds are of similar size, and all animals were sacrificed at 90 days post-implantation. In dogs (N = 8), all implants showed bone formation with significantly more bone formed in biphasic calcium phosphates (30 +/- 6%, N = 8) as compared to hydroxyapatite (14 +/- 5%, N = 8) (p = 0.003). Hydroxyapatite implants did not induce bone formation in mice, rats, or rabbits. Biphasic calcium phosphate induced bone in 6 of 8 scaffolds implanted in 4 rabbits and 3 of 16 scaffolds implanted in 16 mice, whereas it did not induce bone formation in any of the 8 rats. The results presented herein suggest that the incidence of material-induced bone formation varies with animal species and is related to the implant material used.

Osteogenic protein-1 induces bone formation in the presence of bacterial infection in a rat intramuscular osteoinduction model.

Evaluate the ability of osteogenic protein-1 to induce formation of de novo bone in the presence of bacterial infection and metal in an intramuscular osteoinduction model in the rat. Prospective experimental design with assessment time points of up to 4 weeks. Intramuscular pocket surgically created along each side of the spine. One-hundred-twenty adult male Sprague-Dawley rats. Each intramuscular pocket received 0, 10, or 25 microg of osteogenic protein-1 combined with a lyophilized collagen carrier, and 0 or 5 x 10 colony-forming units of Staphylococcus aureus. Pockets in 48 animals received a metal implant. Animals were killed at 1, 2, 3, or 4 weeks. High-resolution radiographs of resulting nodules of bone/soft tissue were digitized, and areas of newly formed bone were quantified using an image analysis workstation. The nodules were decalcified for histology, and calcium content of the decalcifying solution was quantified by flame atomic absorption spectrophotometry. There were minimal levels of calcium and area of new bone formation in nodules from pockets containing collagen carrier without osteogenic protein-1, for both infection and noninfection conditions. Calcium content and area of newly formed bone were significantly greater: 1) in infected pockets with osteogenic protein-1, compared to infected pockets without osteogenic protein-1; and 2) in noninfected pockets with osteogenic protein-1, compared to infected pockets with osteogenic protein-1. The presence of metal did not have a significant effect. Osteogenic protein-1 maintained its osteoinductive capability in a contaminated intramuscular pocket in the rat, albeit at a lower level than without infection. This finding supports further study using a more clinically realistic model.

Compressive strength of calcium carbonate and hydroxyapatite implants after bone-marrow-induced osteogenesis

Natural coral and structurally similar porous hydroxyapatite (HA) have been used as bone substitutes. They are not osteoinductive but bone formation can be induced by marrow cells, even in extraosseal sites. In our previous study we induced bone formation in porous coral and HA after having implanted the materials in intramuscular pockets in rat. New bone formed only in HA or coral implants soaked with marrow cells; fibrous tissue ingrowth alone was observed in the controls (without marrow). In the present study we examined the effect of tissue ingrowth on the mechanical properties of coral and HA implants obtained in a similar process to that used before. At 12 weeks the compressive strength of HA was higher in the marrow group than in the controls; it was also higher than that of the wet unimplanted material. The HA blocks did not show resorption. Coral resorbed quickly and lost its compressive strength, which was originally higher than in HA. At three weeks the marrow group was stronger than the control specimens. After six weeks only the marrow group, but not the controls, could be tested. Bone ingrowth seemed to maintain the strength of the coral implant even if it was dissolving. The mechanical strength of both materials was comparable to that of cancellous bone.