Tubular adenoma of the main pancreatic duct.

We report a case of tubular adenoma of the duct of Wirsung with focal villous changes. To our knowledge, this is the 13th reported case of this uncommon neoplasm and the first with a primarily tubular histologic pattern. The patient presented with abdominal pain and diarrhea and was found on endoscopic retrograde cholangiopancreaticography to have a mass in the head of the pancreas, which was confirmed by endoscopic ultrasound. Clinical and pathological features of the 12 previously reported cases are reviewed. Intraoperative testing failed to rule out adenocarcinoma which, in addition to difficulties presented by local anatomic relationships of the tumor, supports wide surgical resection as the preferred surgical solution.

Cytogenetic, telomere, and telomerase studies in five surgically managed lumbosacral chordomas.

Lumbosacral chordomas are rare skeletal sarcomas of the spine that originate from the remnant notochord. The understanding of this human cancer is limited to observations of its clinical behavior and its embryonic link. Thus, we performed chromosome and molecular analyses from five surgically harvested chordomas in an effort to document genetic and biochemical abnormalities which might aid in understanding the tumor biology of this understudied neoplasm. Cytogenetic analysis of the five chordomas revealed normal results in four patients and random abnormalities in only one tumor cell in the 100 cells studied from the fifth patient. A repeat telomeric probe (TTAGGG)50 was hybridized to genomic DNA isolated from chordoma cells (and HeLa cells) and digested with HinfI. The tumor DNA was paired with leukocyte DNA from age-matched controls and revealed telomere elongation in four of the four chordoma patients studied with molecular genetic techniques. Conversely, telomere length reduction has been reported during in vitro senescence of human fibroblasts, giant cell tumor of bone, colon cancer, intracranial tumors, childhood leukemia, Wilms tumor, and in HeLa cells. Telomerase activity (telomerase is required to maintain telomere integrity) was also determined by visualizing the extension of radioactive telomeric repeats on DNA sequencing gels. The telomeric fragments were assembled during incubation of the cytoplasmic extract containing telomerase. Telomerase activity was observed in HeLa (positive control and commercially available cell line), giant cell tumor of bone (positive control tumor cells from living patients), and in chordoma cells from one of the two chordoma patients (but to a lesser degree compared with HeLa). As expected, the chordoma patients' fibroblasts exhibited no telomerase activity.

Evaluation of recombinant human bone morphogenetic protein-2 as a bone-graft substitute in a canine segmental defect model.

A study was performed in dogs to evaluate the dose-response characteristics and effectiveness of recombinant human bone morphogenetic protein-2 with a collagen sponge carrier in a segmental defect model. Twenty-seven dogs underwent bilateral radial osteotomies with creation of a 2.5-cm diaphyseal defect. All received autogenous cancellous bone graft in one defect and a collagen implant in the other. These implants contained recombinant human bone morphogenetic protein-2 at the following doses: group 1 at 0 microg (three dogs, 0 microg/ml total implant volume), group 2 at 150 microg (three dogs, 50 microg/ml), group 3 at 600 ,g (three dogs, 200 microg/ml), group 4 at 2,400 microg (three dogs, 800 microg/ml), group 5 at 0 microg (five dogs, 0 microg/ml), group 6 at 150 microg (five dogs, 200 microg/ml), and group 7 at 600 microg (five dogs, 50 microg/ml). The defects were stabilized with external fixators. The dogs in groups 1-4 were killed at 12 weeks postoperatively, and those in groups 5-7 were killed at 24 weeks postoperatively except for one dog in group 7, which was killed at 48 weeks. Evaluation included monthly radiographs, biomechanical testing, and nondemineralized histology. All 27 radii with autogenous cancellous bone graft and all 19 implants treated with recombinant human bone morphogenetic protein-2 achieved radiographic and histologic union and gross stability. The eight radii treated with collagen carrier alone went on to radiographic and histologic nonunion and were grossly unstable at death. A dose-dependent occurrence of cyst-like bone voids was noted radiographically and histologically. Biomechanical performance tended to be better at the lowest dose studied at 12 weeks, and all three doses performed better than the placebo (p < 0.05) at 12 and 24 weeks. By 24 weeks, radiolucent areas corresponding to histologic bone voids persisted radiographically, although there was evidence of early bone remodeling. This remodeling progressed to 48 weeks in the single animal followed to this time point, although bone voids remained. These radiologic findings were confirmed histologically. Recombinant human bone morphogenetic protein-2 in a collagen sponge carrier has significant osteoinductive activity in this canine segmental defect model. A dose-response relationship is evident, with heterotopic bone and cyst-like void formation at higher doses and a minimum effective dose of 0-150 microg. At 12 and 24 weeks postoperatively, biomechanical parameters achieved by defects treated with recombinant human bone morphogenetic protein-2 were comparable with those of autograft controls and were significantly stronger than those of the placebo (p < 0.05).

Evaluation of bovine-derived bone protein with a natural coral carrier as a bone-graft substitute in a canine segmental defect model.

The efficacy of a bone-graft substitute (bovine-derived bone protein in a carrier of natural coral) in the healing of a segmental defect of a weight-bearing long bone was evaluated. Twenty dogs, divided into two groups, underwent bilateral radial osteotomies with creation of a 2.5 cm defect. On one side of each dog, the defect was filled with autogenous cancellous bone graft. Contralateral defects received, in a blinded randomized fashion, cylindrical implants consisting of natural coral (calcium carbonate) or calcium carbonate enhanced with a standard dose of bovine-derived bone protein (3.0 mg/implant; 0.68 mg bone protein/cm3). The limbs were stabilized with external fixators, and all animals underwent monthly radiographs. They were killed at 12 (group 1) or 24 (group 2) weeks, and regenerated bone was studied by biomechanical testing and histology. Radiographic union developed in all 20 radii with autogenous cancellous bone grafts and in all 10 of the radii with the composite implants. None of the radii with implants of calcium carbonate alone showed radiographic evidence of union. This represented a statistically significant difference between implant types. In addition, calcium carbonate implants both with and without bone protein demonstrated radiographic evidence of near total resorption of the radiodense carrier by 12 weeks. This resorption facilitated radiographic evaluation of healing. Mean values for biomechanical parameters of radii with the composite implants exceeded those for the contralateral controls at 12 and 24 weeks; the difference was statistically significant at 12 weeks. Histology revealed scant residual calcium carbonate carrier at either time in the defects with calcium carbonate implants; however, a moderate amount was present in defects with the composite implants. In these specimens, the residual carrier was completely surrounded by newly formed bone that may have insulated the calcium carbonate from further degradation. The present study used a carrier of granular calcium carbonate reconstituted with bovine type-I collagen to deliver an osteoinductive protein to the defect site. This carrier is of nonhuman origin (eliminating the risk of disease transmission or antigenicity) and resorbs rapidly. In this model, bovine-derived bone protein in a natural coral carrier performed consistently better than the gold standard autogenous cancellous bone graft in terms of the amount of bone formation and strength of the healed defect. This may have implications for removal of hardware or resumption of weight-bearing in certain clinical situations. These data also indicate that coralline calcium carbonate alone represents a poor option as a bone-graft substitute in this critical-sized segmental defect model.

Porous ceramics as bone graft substitutes in long bone defects: a biomechanical, histological, and radiographic analysis.

Three porous ceramic bone graft materials were compared with regard to their ability to heal a 2.5 cm defect created surgically in a bilateral canine radius model. The ceramic materials were analyzed at 12 and 24 weeks after surgery and included tricalcium phosphate, hydroxyapatite, and collagen hydroxyapatite, which contained a mixture of 35% tricalcium phosphate and 65% hydroxyapatite with added collagen. Each material was evaluated alone and with added bone marrow aspirate. All the implants were compared with a graft of autogenous cancellous bone in the contralateral radius. Biomechanical testing and radiographic evaluation revealed that the addition of bone marrow aspirate was essential for tricalcium phosphate and hydroxyapatite to achieve results comparable with those of cancellous bone. Collagen hydroxyapatite performed well without the addition of bone marrow, although the addition of marrow did have a positive effect. Further qualitative radiographic and histological analysis demonstrated that tricalcium phosphate was the only ceramic that showed any sign of degradation at 24 weeks. This observed degradation proved to be an important factor in evaluating radiographs because the radiodensity of collagen hydroxyapatite and hydroxyapatite interfered with the determination of radiographic union. At 24 weeks, tricalcium phosphate with bone marrow was the material that performed most like cancellous bone. In this study, the biomechanical and radiographic parameters of tricalcium phosphate with bone marrow were roughly comparable with those of cancellous bone at 12 and 24 weeks. Tricalcium phosphate was the only implant that showed significant evidence of degradation at 24 weeks by both histological and radiographic evaluations, and this degradation took place only after a degree of mechanical competence necessary for weight-bearing was achieved.

Evaluation of ground cortical autograft as a bone graft material in a new canine bilateral segmental long bone defect model.

The recent orthopaedic literature reflects a growing number of bone graft substitutes and osteogenic growth factors under investigation in a number of animal models. We attempted to establish a well-controlled, large animal model of a segmental defect in a weight-bearing long bone by developing a bilateral diaphyseal radial defect model in the canine. We also evaluated the effectiveness of ground cortical autograft as a graft material. Twenty-three adult mongrel dogs underwent bilateral radial osteotomies with creation of a 2.0-2.5-cm diaphyseal defect on each side. All dogs received cancellous autograft (CAN) on one side, nine received no graft material (DEF) on the opposite side, and 14 received morselized cortical autograft (CORT) on the opposite side. Radii were stabilized by external fixation. Animals were followed radiographically at 6-week intervals to evaluate the healing process. Thirteen dogs were sacrificed at short-term follow-up (8-12 weeks postsurgery) and 10 at long-term (16-24 weeks). Biomechanical torsion testing to failure and histological evaluation were performed on each defect. All CAN radii achieved union (100%) while only one of nine DEF radii (11%) and none of 14 (0%) of CORT radii achieved union. Statistically significant differences in biomechanical parameters between both test groups and their corresponding autograft control radii were found. Histology revealed fibrous nonunions in the DEF and CORT radii. These results demonstrate that the bilateral canine radial defect model represents a consistent and reproducible model for bone healing of segmental defects in weight-bearing long bones and that ground cortical autograft is an ineffective graft material.

Bovine-derived bone protein as a bone graft substitute in a canine segmental defect model.

OBJECTIVES: To evaluate the efficacy of a bone graft substitute in healing of a segmental defect of a weight-bearing long bone. DESIGN: An established canine model was used to perform a blinded, prospective, randomized study of the performance of bone graft substitute implants. This performance was compared with that of an accepted treatment modality (autograft) in a paired fashion. SETTING: An accredited animal research facility. SUBJECTS AND INTERVENTION: Twenty-eight dogs underwent bilateral radial osteotomies with creation of a 2.5-centimeter defect. On one side, the defect in every dog was filled with autogenous cancellous bone graft (ABG). Contralateral defects received, in a blinded, randomized fashion, cylindrical implants of demineralized bone matrix (DBM) allograft or DBM plus a constant dose (3.0 milligrams) of bovine-derived bone protein (DBM + BP). The defects were stabilized by external fixation. Subjects underwent monthly radiographs and were killed at six, twelve, or twenty-four weeks. Regenerate bone was studied by biomechanical testing and histology. Six animals were studied to determine the dose-response characteristics of the protein preparation. Three received implants containing 0.3 milligram of BP (group 1) and three received 1.0 milligram of BP (group 2). These animals were killed at twelve weeks of follow-up. RESULTS: All twenty-eight ABG radii (100 percent) progressed to radiographic union, as did thirteen of thirteen (100 percent) DBM + BP radii compared with only four of fifteen (27 percent) of DBM radii. The difference between union rates was statistically significant (p < 0.05). Mean values for most biomechanical parameters of DBM + BP radii exceeded those of their contralateral ABG controls at twelve and twenty-four weeks, whereas those for DBM implants did not. Histology revealed microscopic evidence of normal bone healing in all ABG and DBM + BP radii, whereas most DBM radii demonstrated nonunions. In the dose-response arm of the study, six of six ABG radii (100 percent) achieved union; zero of three (0 percent) of group 1 and two of three (67 percent) of group 2 radii achieved grossly stable unions. Biomechanical testing was consistent with radiographic results, indicating that the 3.0-milligram dose was the most effective of those studied. CONCLUSIONS: The DBM + BP composite implants were more effective at healing critical-sized segmental defects than DBM alone in this canine model when a 3.0-milligram per implant dose of BP was used. Biomechanical and histologic properties of the regenerated bone formed by DBM + BP implants was comparable to that of cancellous autograft.

Effects on pulmonary physiology of reamed femoral intramedullary nailing in an open-chest sheep model.

We have recently developed an open-chest sheep model to monitor and study the effects of major orthopedic procedures on pulmonary physiology. In this pilot study, we focused on reamed intramedullary femoral nailing in animals without pulmonary injury. Details of the model are described herein. The control group consisted of sheep that underwent thoracotomy and invasive monitoring only, while the study group also underwent femoral osteotomy, reaming, and intramedullary nailing. Baseline, postthoracotomy, and post-reaming/nailing values were recorded for mean pulmonary arterial pressure, central venous pressure, left arterial pressure, dynamic compliance, arterial blood gas, mixed venous O2, cardiac index, and mean arterial pressure so that hemodynamic and oxygen transport data could be calculated. Postprocedure values were recorded at hourly intervals for 4 h. A physiologically stable, reproducible model was created. No statistically significant differences were found between the control and experimental groups, indicating no adverse effect of femoral reaming/nailing. In one animal, using echocardiography, pulmonary embolization was documented while reaming and inserting the intramedullary nail. Reamed femoral intramedullary nailing is not detrimental to sheep with otherwise normal lungs. This finding suggests that femoral reaming and nailing in trauma patients without associated pulmonary injuries and otherwise normal lungs may be carried out without risk of inducing significant respiratory complications.

Telomerase activity and oncogenesis in giant cell tumor of bone.

BACKGROUND: Benign giant cell tumor of bone (GCT) is a primary skeletal neoplasm with an unpredictable pattern of biologic aggressiveness and cytogenetic findings characterized by telomeric associations and telomeric reduction. The role of maintaining telomeric integrity is performed by telomerase. To determine if telomerase activity is present, cell extracts from fibroblasts and tumor cells from five patients with GCT were analyzed and compared with HeLa (a positive control cell line). METHODS: Telomerase activity was detected by visualizing the extension of radioactive telomeric repeats on DNA sequencing gels. Telomere reduction was assessed using southern blot analyses of the restriction enzyme Hinf I digested DNA with a radio-labeled telomere probe. RESULTS: Telomerase or telomerase-like activity was detected in the cell extracts from HeLa and tumor cells. However, GCT telomerase activity varied and was less than that observed in HeLa, but no activity was detected from fibroblasts. In addition, telomere reduction was seen in DNA isolated from both HeLa and GCT but not in fibroblasts or age-matched controls. CONCLUSION: Telomere reduction and telomerase activity may be oncogenic sustaining events required to maintain the transformed phenotype seen in GCT.

Growth factor modulation of distraction osteogenesis in a segmental defect model.

A model was established in 39 dogs to investigate the growth factor modulation of regenerate bone in distraction osteogenesis. A segment of the diaphysis of the radius was resected unilaterally. An osteotomy was made proximal to the segmental defect to create a transport segment. A monolateral external fixator was applied. After a latency period, the segment was transported across the defect. One week after the transport assembly contacted the distal pin clamp, an ipsilateral osteotomy of the proximal ulna was performed. In 20 dogs, transforming growth factor-beta was injected into the regenerate bone halfway through the transport period. Four dogs were sacrificed before docking, when the regenerate bone was still immature. In specimens harvested halfway through the transport period, evidence was found of intramembranous ossification during distraction. In specimens harvested after the transport assembly contacted the distal pin clamp, evidence was found that the mature regenerate formed by endochondral ossification. Therefore, a combined mechanism of ossification is proposed for this segmental defect model that includes mechanical stimulus for bone differentiation. The one-time administration of transforming growth factor-beta retarded the formation of a stable, united regenerate. It is concluded that transforming growth factor-beta caused an effect opposite to that which was desired.