Critical size defect in the goat's os ilium. A model to evaluate bone grafts and substitutes.

Bone defects and their treatment are a well known problem in orthopaedic surgery. A critical size defect is a suitable model to study bone replacement materials. This study describes a critical size defect in the goal and the evaluation of three bone fillers (particulate autograft, particulate allograft, and a polyethylene oxide/polybutylene terephthalate copolymer) in this defect. The goat allows for implantation of large implants and has a metabolic rate more comparable with that of humans than small animals. The critical size defect, located in the goat's iliac wing, is easily reproducible and allows qualitative and quantitative evaluation of bone grafts and bone graft substitutes. After 3 months of healing, the unfilled defects showed 13.5% bone in the defect, the autografted defects 36.3%, and the allografted 18.5%. The copolymer gave only 1.5% bone in the defect; this is in contrast to previous reports. The described model allows for the evaluation of bone graft substitutes before introduction into clinical practice.     

Plastic surgery in post-osteomyelitic defect of the mandible

An analysis of results of plasty of postosteomyelitic defects of the mandible in 235 patients has been made. The outcomes of the operation were found to depend on its kind, on the transplant conservation methods and terms of substitution of the defects after sequestrectomy.     

Repair of mandible defect with tissue engineering bone in rabbits

BACKGROUND: The aim of the present study was to investigate the effect of tissue engineering bone composed of bone marrow-derived osteoblasts and demineralized bone in repairing mandible defect. METHODS: Bone marrow-derived osteoblasts of 20 rabbits were cultured and seeded into scaffold of allogeneic demineralized bone to construct tissue engineering bone graft in vitro, which was used to repair the 10 x 5-mm bone defect made in the same rabbit mandible edge. Implant of demineralized bone alone was as the control. Rabbits were killed according to the schedule: five after 2 weeks, five after 4 weeks, five after 8 weeks, five after 12 weeks, and the implants were harvested for gross, radiographic, and histological observation. RESULTS: New bone formation at the margin region of defect and osteogenesis at the centre were observed in the implant of tissue engineering bone, and the bone formation pattern included osteogenesis, osteoconduction, and osteoinduction. In the implant of demineralized bone alone, the major bone formation pattern was 'creeping substitute'. CONCLUSIONS: The tissue engineering bone graft constructed by autogenous bone marrow-derived osteoblasts and allogeneic demineralized bone was better than demineralized bone alone in bone formation capability, which might be an ideal graft for bone defect repair.     

人体下颌骨节段性缺失的三维有限元模型的建立

目的：建立人体下颌骨颏部节段性缺失的三维有限元模型,为下颌骨缺损重建的生物力学研究提供一个仿真平台。方法选取1例牙列完整、咬合关系正常的男性志愿者进行下颌骨螺旋CT扫描,运用Mimics10.01软件读取Dicom格式的CT数据,并形成正常人下颌骨的三维几何模型,然后导入HyperMesh软件中,形成下颌骨的实体模型,并利用HyperMesh软件自带的切割工具对下颌骨颏部进行完全离断,离断后的左右下颌骨由模拟牵张器连在一起,生成的实体模型在HyperMesh软件中完成网格划分及对材料属性进行赋值,并最终形成下颌骨颏部节段性缺失的三维有限元模型。结果：建立了完全截骨牵张成骨的人下颌骨节段缺失的三维有限元模型,可模拟弧形牵张成骨,并可观察牵张过程中任意点的应力及位移情况。结论：人体下颌骨颏部节段性缺失的有限元模型的建立,为弧形牵张成骨重建下颌骨颏部节段缺失的生物力学分析奠定基础。     

放射性下颌骨坏死术后缺损的游离腓骨肌皮瓣重建

目的 评价游离腓骨（肌）皮瓣重建放射性下颌骨坏死术后缺损的临床效果。方法 以带肌袖和不带肌袖的游离腓骨（肌）瓣重建放射性下颌骨坏死手术切除后的骨缺损，以皮岛修复瘘周软组织缺损，记录腓骨截骨、组织瓣存活情况，供区、受区并发症，术后张口度和余留牙咬合情况，对颌面部外形和功能重建进行评价。结果 随访3～16个月，4例带肌袖腓骨肌皮瓣、5例不带肌袖腓骨皮瓣重建下颌骨缺损均获成功。下颌骨截骨长度6、0～17．0cm，切取腓骨长度8．6～17．0cm。腓骨截成三段2例，二段5例，截成二段后折叠2例。无1例发生严重供区或受区并发症。所有病例外形恢复良好，双侧下颌角处于同一平面，无中线偏斜，开口度2．5～3．3cm，余留牙咬合正常。义齿修复后咀嚼功能满意。结论 游离腓骨（肌）皮瓣存活率高，外形和功能恢复好，适合于放射性下颌骨坏死术后颌面部软硬组织缺损的即刻重建。     

Outcomes in omphalocele correlate with size of defect

BackgroundOmphaloceles can be some of the more challenging cases managed by pediatric surgeons. Single center studies have not been meaningful in delineating outcomes due to the length of time required to accumulate a large enough series with historical changes in management negating the results. The purpose of this study was to evaluate factors impacting the morbidity and mortality of neonates with omphaloceles.MethodsA multicenter, retrospective observational study was performed for live born neonates with omphalocele between 2005 and 2013 at nine centers in the United States. Maternal and neonatal data were collected for each case. In-hospital management and outcomes were also reported and compared between neonates with small and large omphaloceles.ResultsTwo hundred seventy-four neonates with omphalocele were identified. The majority were delivered by cesarean section with a median gestational age of 37 weeks. Overall survival to hospital discharge was 81%. The presence of an associated anomaly was common, with cardiac abnormalities being the most frequent. Large omphaloceles had a significantly longer hospital and ICU length of stay, time on ventilator, number of tracheostomies, time on total parenteral nutrition, and time to full feeds, compared to small omphaloceles. Birth weight and defect size were independent predictors of survival.ConclusionThis is the largest contemporary study of neonates with omphalocele. Increased defect size is an independent predictor of neonatal morbidity and mortality.Level of EvidenceLevel II.     

Bone tissue engineering in a critical size defect compared to ectopic implantations in the goat.

Since the application of the autologous bone graft, the need for an alternative has been recognized. Tissue engineering (TE) of bone by combining bone marrow stromal cells (BMSCs) with a porous scaffold, is considered a promising technique. In this study we investigated the potential of tissue engineered bone to heal a critical sized defect in the goat. Orthotopic bone formation was compared to ectopic bone formation in comparable constructs. TE constructs were prepared from goat BMSCs and porous biphasic calcium phosphate ceramic scaffolds. These constructs and scaffolds without cells were implanted paired in critical sized iliac wing defects. Comparable samples were implanted intramuscularly. After 9 (n=7) and 12 (n=8) weeks implantation, the samples were analyzed histomorphometrically. After 9-weeks implantation in the iliac wing defect, significantly more bone apposition was found in the TE condition. After 12 weeks, the defects were almost completely filled with bone, but no significant advantage of TE was determined anymore. This contrasted with the intramuscular samples where TE implants showed significantly more bone at both time points. In conclusion, bone TE is feasible in critical sized defects. However, when appropriate osteoconductive/inductive materials are applied the effect of cell seeding may be temporary.     

Experimental study on size matching in a canine living-donor lobar lung transplant model.

OBJECTIVE: In an effort to address the donor-shortage issue, living-donor lobar lung transplants have been performed with satisfactory results. The use of small grafts is potentially problematic because it could cause high pulmonary artery pressure, resulting in lung edema. The purpose of this study was to evaluate the effect of small grafts on early pulmonary function and to identify the predictor for acceptable size discrepancy. METHODS: Seventeen pairs of mongrel dogs with various donor-recipient sizes were used. Body weight, height, chest circumference, and lung weight were measured as size parameters. Right middle, lower, and cardiac lobes were implanted as a right lung of the recipient and the left lower lobe was implanted as a left lung without use of cardiopulmonary bypass. Pulmonary function of the recipient was measured for 6 hours after reperfusion. RESULTS: A significant negative correlation was found between donor/recipient body-weight ratio and mean pulmonary artery pressure at 1 hour (r = -0.594, P =.025). A significant correlation was found between donor/recipient body-weight ratio and PaO(2) at 6 hours (r = 0.704; P =.007). There was no significant correlation between the other 3 size parameters and postoperative pulmonary function. All 8 recipients with a donor/recipient body-weight ratio of 1.2 or greater survived the 6-hour assessment period, and their PaO(2) exceeded 500 mm Hg at 6 hours. CONCLUSIONS: Donor/recipient weight ratio is an important predictor of early pulmonary function in a canine living-donor lobar lung transplant model.     

Rosai-Dorfman disease of the mandible.

Rosai-Dorfman disease (RDD) is a rare, non-neoplastic histiocytosis most commonly characterized by painless, massive cervical lymphadenopathy. Over half of all patients with lymph node involvement also demonstrate extranodal disease, with most affected individuals exhibiting lesions within the region of the head and neck. Oral manifestations of RDD are extremely rare, and almost always identified in association with nodal or other extranodal disease. However, rare examples of extranodal RDD, including oral RDD, without clinical or radiographic evidence of concomitant lymph node involvement, have also been described. We report a rare case of solitary, extranodal RDD arising within the mandible in a pregnant woman. To our knowledge, this case represents only the fourth documented example of solitary oral RDD. A review of the clinical and histopathologic features associated with RDD is also presented.     

Distraction osteogenesis in the irradiated rabbit mandible.

PURPOSE: The potential use of distraction osteogenesis in mandibular reconstruction has been limited by its questionable efficacy in previously radiated bone. The purpose of this study was to evaluate the effects of irradiation on mandibular distraction osteogenesis (DO). MATERIALS AND METHODS: Six rabbits received a unilateral irradiation (group R) in the mandible with a total dose of 27.0 Gy in five 5.4 Gy fractions (equivalent to 50 Gy/25 fractions). The contralateral side served as control (group C). Bilateral osteotomy was made 3 months after completion of irradiation. After a 1-week latency period bone distraction was activated at a rate of 0.5 mm twice daily for 8 days, followed by a consolidation phase of 6 weeks. New bone underwent radiographic, densitometric, histological and histomorphometric analysis. RESULTS: Two rabbits were excluded from the study, one due to infection on both sides and death in another animal. After 6 weeks of consolidation, the irradiation group had no significantly lower BMD than control group. No difference was found between the percent area of new bone in both groups. New bone was more mature and organised of group C than in groups R. Larger chondroid islands were found evident in distracted bone of group R than group C. CONCLUSIONS: It seems that DO can be feasible in previously irradiated rabbit mandible.     

Use of a collagen-platelet rich plasma scaffold to stimulate healing of a central defect in the canine ACL.

The anterior cruciate ligament (ACL) of the knee fails to heal after primary repair. Here we hypothesize that a beneficial biologic repair response can be induced by placing a collagen-platelet rich plasma (collagen-PRP) material into a central ACL defect. A collagen-PRP scaffold was used to treat a central ACL defect in vivo. In the first experiment, the histologic response in treated and untreated defects was evaluated at 3 (n = 5) and 6 weeks (n = 5). In the second experiment, biomechanical testing of the treated ligaments (n = 8) was performed at 6 weeks and compared with the results of biomechanical testing of untreated defects at the same time-point (n = 6). The percentage filling of the defects in the treated ACLs was significantly higher at both the 3- and 6-week time-points when compared with the untreated contralateral control defects (50 +/- 21% vs. 2 +/- 2% at 3 weeks, and 43 +/- 11% vs. 23 +/- 11 at 6 weeks; all values mean +/- SEM. Biomechanically, the treated ACL defects had a 40% increase in strength at 6 weeks, which was significantly higher than the 14% increase in strength previously reported for untreated defects (p < 0.02). Placement of a collagen-PRP bridging scaffold in a central ACL defect can stimulate healing of the ACL histologically and biomechanically.     

Reconstruction of a large mandible defect utilizing a full-thickness vascularized calvarial bone graft

Historically, mandibular reconstruction has always been a challenging problem. Various methods have been used including alloplasts such as stainless steel and titanium plates, trays filled with bone fragments, vascularized and non-vascularized bone grafts [1, 2]. Most methods have had variable success until the advent of microsurgical techniques. With the high success rate now obtainable utilizing free tissue transfer, mandible reconstruction has become a procedure with a more predictable outcome and most other reconstructive methods have now been abandoned. In spite of this, clinical situations do arise, such as with the case presented, where for one reason or another, microvascular techniques are either not available, not applicable or have failed. A case of mandibular reconstruction using a vascularized full-thickness calvarial bone graft is presented in which the end result was very satisfactory, both aesthetically and functionally. Received: 2 September 1997 / Accepted: 27 October 1997     

Allogeneic mesenchymal stem cells regenerate bone in a critical-sized canine segmental defect

BACKGROUND: Mesenchymal stem cells from adult bone marrow are multipotent cells capable of forming bone, cartilage, and other connective tissues. In a previous study, we demonstrated that autologous mesenchymal stem cells could repair a critical-sized bone defect in the dog. The objective of this study was to determine whether the use of allogeneic mesenchymal stem cells could heal a critical-sized bone defect in the femoral diaphysis in dogs without the use of immunosuppressive therapy. METHODS: A critical-sized segmental bone defect, 21 mm in length, was created in the mid-portion of the femoral diaphysis of twelve adult dogs that weighed between 22 and 25 kg. Each defect was treated with allogeneic mesenchymal stem cells loaded onto a hollow ceramic cylinder consisting of hydroxyapatite-tricalcium phosphate. A complete mismatch between donor stem cells and recipient dogs was identified by dog leukocyte antigen typing prior to implantation. The healing response was evaluated histologically and radiographically at four, eight, and sixteen weeks after implantation. The radiographic and histological results at sixteen weeks were compared with the historical data for the control defects, which included defects that had been treated with a cylinder loaded with autologous mesenchymal stem cells, defects treated with a cylinder without mesenchymal stem cells, and defects that had been left untreated (empty). The systemic immune response was evaluated by the analysis of recipient serum for production of antibodies against allogeneic cells. RESULTS: For defects treated with allogeneic mesenchymal stem cell implants, no adverse host response could be detected at any time-point. Histologically, no lymphocytic infiltration occurred and no antibodies against allogeneic cells were detected. Histologically, by eight weeks, a callus spanned the length of the defect, and lamellar bone filled the pores of the implant at the host bone-implant interface. Fluorescently labeled allogeneic cells were also detected. At sixteen weeks, new bone had formed throughout the implant. These results were consistent with those seen in implants loaded with autologous cells. Implants loaded with allogeneic or autologous stem cells had significantly greater amounts of bone within the available pore space than did cell-free implants at sixteen weeks (p < 0.05). CONCLUSIONS: The results of this study demonstrated that allogeneic mesenchymal stem cells loaded on hydroxyapatite-tricalcium phosphate implants enhanced the repair of a critical-sized segmental defect in the canine femur without the use of immunosuppressive therapy. No adverse immune response was detected in this model.