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Biomedical subjects

S A Lietman

Publications and source records attributed to S A Lietman.

10 recordsLinked to original sources
PubMed2005

The effect of recombinant human osteogenic protein-1 on allograft incorporation.

We used a canine intercalary bone defect model to determine the effects of recombinant human osteogenic protein 1 (rhOP-1) on allograft incorporation. The allograft was treated with an implant made up of rhOP-1 and type I collagen or with type I collagen alone. Radiographic analysis showed an increased volume of periosteal callus in both test groups compared with the control group at weeks 4, 6, 8 and 10. Mechanical testing after 12 weeks revealed increased maximal torque and stiffness in the rhOP-1 treated groups compared with the control group. These results indicate a benefit from the use of an rhOP-1 implant in the healing of bone allografts. The effect was independent of the position of the implant. There may be a beneficial clinical application for this treatment.

Animals↗
PubMed2002

The temporal sequence of spontaneous repair of osteochondral defects in the knees of rabbits is dependent on the geometry of the defect.

Damage to articular cartilage is a common injury, for which there is no effective treatment. Our aims were to investigate the temporal sequence of the repair of articular cartilage and to define a critical-size defect. Full-thickness defects were made in adult male New Zealand white rabbits. The diameter (1 to 4 mm) of the defects was varied in order to determine the effect that the size and depth of the defect had on its healing. The defects were made in the femoral groove of the knee with one defect per knee and eight knees per group. The tissues were fixed in formalin at days 3, 7, 14, 21, 28, 42, 84 and 126 after operation and the sections stained with Toluidine Blue. These were then examined and evaluated for several parameters including the degree of metachromasia and the amount of subchondral bone which had reformed in the defect. The defects had a characteristic pattern of healing which differed at different days and for different sizes of defect. Specifically, the defects of 1 mm first peaked in terms of metachromasia at day 21, those of 2 mm at day 28, followed by defects of 3 mm and 4 mm. The healing of the subchondral bone was slowest in defects of 1 mm.

Animals↗
PubMed2001

The partial pelvic replacement cup in severe acetabular defects.

Severe bone loss resulting in pelvic discontinuity may result in <50% coverage of the socket by native bone. The goal in these cases is to bridge the gap by using bone grafts, methylmethacrylate, or both. The partial pelvis cup helps protect bone grafts during their incorporation and also provides a stable construct to the acetabulum for weight bearing.

Acetabulum↗
PubMed2000

Complications of irradiated allografts in orthopaedic tumor surgery.

Massive structural allografts used for replacement of bone defects after removal of bone tumors have several complications, including fracture, infection, and nonunion. To decrease the rate of infection, irradiation of selected allografts before their implantation was performed. This study evaluated the complications in patients with these irradiated grafts. Twenty-four patients were identified who had received allografts from 1987 through 1991 that were irradiated before implantation. The dosage of radiation was between 10 kGy and 30 kGy. The mean length of followup of the patients was 5 years (range, 2-9 years). These grafts were compared with a control group of grafts that were not irradiated but were implanted during the same time and used for similar diagnostic problems with defects of similar size. The outcomes of the groups differed significantly only in the incidence of allograft fracture. These findings indicate that high-dose irradiation to bone allografts is associated with a higher rate of fracture than are similar reconstructions using nonirradiated allografts.

Adolescent↗
PubMed1999

Size and position of a single condyle allograft influence knee kinematics.

An optimal match for size and shape between the donor femur and the host knee is considered a critical factor influencing the outcome of a knee allograft implantation. An in vitro allograft model was developed to determine the influence of the size and position of a lateral distal femoral condylar allograft on knee kinematics. Functional knee motion was simulated in a cadaver host knee in the intact state after removing and reimplanting the native lateral condyle of the distal femur and after serially replacing the native condyle with eight donor allografts. Each allograft was first tested in an optimal position and subsequently shifted 3 mm proximal and 3 mm distal to the joint line to quantify changes in joint kinematics due to the position of the allograft. The intact knee and the knee with the ideally implanted native allograft followed similar kinematic trends. Decreasing the width of the allograft increased the valgus knee orientation at full flexion, translated the tibia posteriorly at full extension, and externally rotated the tibia throughout knee flexion. The proximal shift in allograft position increased the valgus orientation at full extension, translated the tibia posteriorly at mid-flexion, and externally rotated the tibia throughout flexion. The distal shift in position had the opposite effect on the kinematics of the proximal shift. These results indicate that improving techniques for preoperative size-matching and intraoperative allograft placement may help to reduce biomechanical complications following implantation of the allograft.

Biomechanical Phenomena↗
PubMed1997

Stimulation of proteoglycan synthesis in explants of porcine articular cartilage by recombinant osteogenic protein-1 (bone morphogenetic protein-7).

UNLABELLED: Osteogenic protein-1 (also known as bone morphogenetic protein-7) is a member of the bone morphogenetic protein family. Bone morphogenetic proteins and related members of the TGF-beta (transforming growth factor-beta) superfamily are involved in the development and repair of bone. Recombinant bone morphogenetic proteins induce the formation of new cartilage and bone at heterotopic sites. We investigated the influence of recombinant osteogenic protein-1 (at doses of three, ten, thirty, or 100 nanograms per milliliter) on the synthesis and release of proteoglycans and the maintenance of a steady-state concentration of proteoglycans in explants of porcine articular cartilage that were maintained in chemically defined serum-free medium. We found a dose-dependent stimulation of proteoglycan synthesis and a concurrent decrease in the rate of release of proteoglycans from the explants. The size of the proteoglycan monomers and the composition of the glycosaminoglycan chains in the untreated articular cartilage were similar to those in the articular cartilage treated with osteogenic protein-1. The capacity of the newly synthesized proteoglycan monomers to form aggregates with exogenous hyaluronic acid was found to be similar to that of proteoglycans in bovine nasal cartilage. Our results demonstrated that osteogenic protein-1 stimulated the synthesis of proteoglycans and diminished the release of proteoglycans from explants of porcine articular cartilage. CLINICAL RELEVANCE: The maintenance and repair of articular cartilage is a formidable challenge in clinical orthopaedics. The stimulation of proteoglycan synthesis by osteogenic protein-1 (bone morphogenetic protein-7) in explants of cartilage maintained in chemically defined serum-free medium implies that recombinant osteogenic protein-1 may play a role in the maintenance of a steady-state concentration of proteoglycans in articular cartilage, a desirable prerequisite for optimum repair of cartilage. Osteogenic protein-1 can initiate the formation of cartilage from mesenchymal cells. Once new cartilage has formed at the site of repair, osteogenic protein-1 also may maintain the synthesis of proteoglycans.

Animals↗
PubMed1987

Use of CT scans in selection of patients for pectus excavatum surgery: a preliminary report.

A pectus index can be derived from dividing the transverse diameter of the chest by the anterior-posterior diameter on a simple CT scan. In a preliminary report, all patients who required operative correction for pectus excavatum had a pectus index greater than 3.25 while matched normal controls were all less than 3.25. A simple CT scan may be a useful adjunct in objective evaluation of children and teenagers for surgery of pectus excavatum.

Adolescent↗