Christopher Niedhart

BMP-2 Incorporated in a Tricalcium Phosphate Bone Substitute Enhances Bone Remodeling in Sheep

Bone morphogenetic protein-2 (BMP-2) is a well-known osteoinductive protein, which requires a carrier for local application. As an alternative to the previously described carriers, an in situ hardening, resorbable, and osteoconductive β-tricalcium phosphate cement (TCP) is tested. Trepanation defects in the bovine distal femoral epiphysis are filled with a composite consisting of TCP and 200 μg rhBMP-2 per cm3 TCP, autologous bone graft, pure TCP, or left empty. A radiological follow-up is performed after 7 weeks and 3 months. The sheep are euthanized and bone samples are analyzed by microradiography, histology, and histomorphometry. Microradiography and histology show similar results for pure TCP and the composite. The defects are filled with trabecular bone and newly formed bone is in close contact with the remaining TCP-particles. The majority of the cement is resorbed, in the composite group the amount of remaining cement particles is reduced. Defects treated with autologous bone graft are filled completely, while untreated defects shows only a small amount of bone originating from the rim of the defect. Histomorphometry of the defects treated with pure TCP shows a significantly increased bone content in comparison to defects treated with the composite or autologous bone graft. Analysis of the remaining cement particles shows significantly less cement in the TCP/rhBMP-2 group in comparison to pure TCP. The sum of bone and cement content in the rhBMP-2 group shows amounts comparable to the calcified structures found following autologous bone grafting. The addition of rhBMP-2 to the TCP leads to faster remodeling of the defect comparable to autologous bone graft, while defects treated with pure TCP are not completely remodeled.

In vivo testing of a new in situ setting β‐tricalcium phosphate cement for osseous reconstruction

A new in situ setting tricalcium phosphate cement was implanted in 1.5-mm trepanation defects in rat femurs. Empty cavities and autologous bone grafts were used as controls. Cement resorption and new bone formation were evaluated in undecalcified sections with histologic examination, contact microradiographies, radiodensitometry, and scanning electron microscopy after 1 and 3 weeks. The mechanical integrity was tested in a three-point bending test. The amount of new bone formation over time was determined by intravital fluorescence staining. With the in situ setting substance, a good filling of the whole trepanation defect was achieved without leakage of the paste-like cement. Slow resorption of the cement and new bone formation beginning at the edge of the defect were seen after 1 week. After 3 weeks, resorption was advanced and there was ingrowth of new bone, with close contact between cement particles and bone, as shown in histologic sections and with a calcium/phosphorus analysis by quantitative line scans of an electron microanalysis (SEM-EPMA). This new self-hardening cement is bioactive, resorbable, and osteotransductive. It may be usable for the filling of stable defects, such as cysts or benign tumors, or for bone supplementation in revision arthroplasty.

Osteonecrosis 15 years after femoral neck fracture and long-term low-dose inhaled corticosteroid therapy

Posttraumatic avascular necrosis of the femoral head typically occurs immediately or within a few years after a femoral neck injury, and non-traumatic avascular necrosis is often related to systemic glucocorticoid therapy. We report an unusual case in which avascular necrosis of the femoral head occurred 15 years after a transcervical femoral fracture in a woman with a 20-year history of daily inhaled glucocorticoid therapy for chronic bronchitis. She had not taken glucocorticoids by any other route and had no other risk factors for osteonecrosis. To our knowledge, this is the first report of osteonecrosis associated with inhaled glucocorticoid therapy in a patient with a local cause of diminished vascular reserve. Inhaled glucocorticoid therapy should be added to the list of risk factors for osteonecrosis.

In vitro elution characteristics of gentamicin and vancomycin from synthetic bone graft substitutes.

Objects: Beta tricalciumphosphate pellets loaded with individualized antibiotics may represent novel options in the treatment of osteomyelitis and infectious bone disease. Here, the in vitro antibiotic elution of vancomycin and gentamicin from the synthetic bone graft substitutes Cerasorb® and Cerasorb M® was tested. Methods: Antibiotic elution and concentration of gentamcin and vancomycin were measured using photometrically-based measurement and homogeneous particle-enhanced turbidimetric inhibition immunoassays (PETINIA). Results: Initially both materials showed a high release of the loaded antibiotics, with Cerasorb M® showing lower release levels for gentamicin and vancomycin than Cerasorb®. Gentamicin concentrations of Cerasorb M granules and Cerasorb were below the minimum detectiontreshold until day four and six of the experiment respectively. The vancomycin release-level followed a similar pattern, although the vancomycin concentration eluted by Cerasorb M® granules stayed above the detection threshold during the experimental time. Conclusions: Cerasorb® and Cersorb M® may represent a new treatment option in osteomyelitis and infectious bone disease.

Efficacy and safety of a novel moldable, resorbable, and degradable sealant of bone surfaces for hemostasis after bone graft harvesting from the iliac crest

Study Design. A prospective, controlled, open, randomized multicenter study. Objective. The studys objective was to demonstrate equivalence of a novel, moldable, resorbable, and degradable synthetic polymer (Bone Seal) compared with a collagen fleece (Lyostypt) in efficacy and safety for topical hemostasis after iliac crest bone graft harvesting. Summary of Background Data. Harvesting cortico-cancellous bone from the iliac crest is a well established procedure in orthopedic and particularly in spine surgery. It is associated with significant morbidity at the donor site where hematoma formation may cause impaired wound healing and infections in up to 10% of cases. Methods. A total of 112 patients were included in the safety analysis. Safety was determined by a compound wound healing score and the incidence of adverse clinical effects. One hundred and eight patients were studied for equivalence in efficacy using a compound bleeding score. The handling properties and the application to the bone surface of either device were measured with two additional compound scores. Results. The mean bleeding scores in the final analysis was 4.5 ± 1.3 for the Bone Seal group and 4.2 ± 1.3 for the collagen fleece group. Bone Seal was better applicable to the bleeding bone surfaces than the collagen fleece, even though its handling was more complicated. Wound healing and the incidences of adverse clinical events were comparable in either study group. Conclusions. Bone Seal is an effective and safe hemostatic material for sealing bleeding bone surfaces after iliac crest bone graft harvesting. By virtue of its hemostatic efficacy, Bone Seal is preventive for wound healing disorders.

Sekundäre juvenile Osteoporose

Die juvenile Osteoporose tritt im Verhaltnis zur Osteoporose des alteren Menschen erheblich seltener auf. Eine Erkrankung stellt aber fur das betroffene Kind und dessen Familie eine erhebliche Belastung dar. Die meisten juvenilen Osteoporosen sind sekundarer Form, ausgenommen die idiopathische juvenile Osteoporose, bei der es sich um eine nichthereditare Form der erhohten Knochenbruchigkeit im Kindesalter handelt, fur die keine auslosende Ursache verantwortlich gemacht werden kann. Die haufigsten Ursachen sind entweder durch eine entsprechende Grunderkrankung, z. B. rheumatoide Arthritis oder iatrogen durch osteokatabole Medikamente bedingt, an erster Stelle Kortison.