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Biomedical subjects

R J Friedman

Publications and source records attributed to R J Friedman.

At least 19 recordsLinked to original sources
PubMed2001

Regaining chondrocyte phenotype in thermosensitive gel culture.

Chondrocyte tissue engineering continues to be a challenging problem. When chondrocytes are duplicated in vitro, it is imperative to obtain an adequate number of cells of optimal phenotype. A temperature-sensitive polymer gel, a copolymer of poly(N-isopropylacrylamide) and acrylic acid (PNiPAAm-co-Aac), has the ability of gelling at 37 degrees C (the lower critical solution temperature, LCST) or above and liquefying below that temperature (Vernon and Gutowska, Macromol. Symp. 1996;109:155-167). The hypothesis of this study was that chondrocytes could (1) duplicate in the copolymer gel; (2) regain their chondrocyte phenotype; and (3) be easily recovered from the gel by simply lowering the temperature below 37 degrees C. Chondrocytes from adult rabbit scapular cartilage were harvested and cultured in a monolayer culture until confluency (approximately 2 weeks). Next, the cells were harvested and seeded into the copolymer gel and cultured for 2-4 weeks. The phenotype of the cultured cells was then characterized. Two groups of control cultures, monolayer and agarose gel, were used to compare their ability to maintain chondrocyte phenotype. The results showed that chondrocytes isolated from rabbit scapula can re-express chondrocyte phenotype in agarose culture and polymer gel culture but not in monolayer culture. Also, cultured chondrocytes can be easily recovered from polymer gel culture by simply lowering the temperature. This new in vitro method of chondrocyte culture is recommended for chondrocyte propagation and regaining chondrocyte phenotype before cell seeding or transplantation.

Acrylamide↗
PubMed2001

Evaluation of scatter contribution from shielding materials used in scatter measurements for calibration range characterization.

The contribution of scatter from the shielding material used in scatter measurements at the Ohio Emergency Management Agency was evaluated. This was accomplished by comparing physical measurements with results generated by detectors modeled in the Monte Carlo shielding code, MCNP4B. The high purity germanium (HPGe) detector model was improved by using radiographs to more accurately represent the detector geometry, including a model of the lithium-contact transition region, and considering the effects of the non-uniform electric field in the germanium crystal. Photons scattered from the shielding material were found to contribute 4.25% of the total scatter recorded by the HPGe detector (thus contributing only 0.26% of the total dose) at a point 5 m from a 1.35 GBq (36.4 mCi) 137Cs source.

Calibration↗
PubMed2001

Prolonged enoxaparin therapy to prevent venous thromboembolism after primary hip or knee replacement. Enoxaparin Clinical Trial Group.

BACKGROUND: Patients undergoing hip or knee joint replacement are at risk for venous thromboembolic complications for up to twelve weeks postoperatively. We evaluated the efficacy and safety of a prolonged post-hospital regimen of enoxaparin, a low-molecular-weight heparin, in this patient population. METHODS: Following elective total hip or knee replacement, 968 patients received subcutaneous enoxaparin (30 mg twice daily) for seven to ten days, and 873 were then randomized to receive three weeks of double-blind outpatient treatment with either enoxaparin (40 mg once daily) or a placebo. The primary efficacy end point was the prevalence of objectively confirmed venous thromboembolism or symptomatic pulmonary embolism during the double-blind phase of treatment. RESULTS: Of the 873 randomized patients, 435 underwent elective total hip replacement and 438 underwent elective total knee replacement. Enoxaparin was superior to the placebo in reducing the prevalence of venous thromboembolism in patients treated with hip replacement: 8.0% (eighteen) of the 224 patients treated with enoxaparin had venous thromboembolism compared with 23.2% (forty-nine) of the 211 patients treated with the placebo (p < 0.001; odds ratio, 3.62; 95% confidence interval, 2.00 to 6.55; relative risk reduction, 65.5%). Enoxaparin had no significant benefit in the patients treated with knee replacement: thirty-eight (17.5%) of the 217 patients treated with enoxaparin had venous thromboembolism compared with forty-six (20.8%) of the 221 patients treated with the placebo (p = 0.380; odds ratio, 1.24; 95% confidence interval, 0.76 to 2.02; relative risk reduction, 15.9%). Symptomatic pulmonary embolism developed in three patients, one with a hip replacement and two with a knee replacement; all had received the placebo. There was no significant difference in the prevalence of hemorrhagic episodes or other types of toxicity between the enoxaparin and placebo-treated groups. CONCLUSIONS: Prolonging enoxaparin thromboprophylaxis following hip replacement for a total of four weeks provided therapeutic benefit, by reducing the prevalence of venous thromboembolism, without compromising safety. A similar benefit was not observed in patients treated with knee replacement.

Adult↗
PubMed2000

Intersubjectivity and interaction in the analytic relationship: a mainstream view.

The authors conceptualize intersubjectivity as a meta-theory that reflects the inherent nature of human relatedness and is conceptually independent of any particular theory of mind or school of psychoanalysis. Their view of intersubjectivity joins the emotional life of the analyst to that of the patient and places the analytic relationship at the center of the analytic process. They contrast intersubjectivity with traditional classical conflict theory so as to clarify the relevance of intersubjectivity for psychoanalytic clinical theory and therapeutic practice. In so doing, they hope to direct analysts more firmly toward the study of the unconscious dyadic contributions to the affective, inactive, and interactive dimensions of the analytic situation and their impact upon the patient's actions within and experience of the analytic relationship. To illustrate their thesis, two hours from an analysis are presented in detail.

Adult↗
PubMed2000

Multidirectional instability of the glenohumeral joint.

The concept of multidirectional instability (MDI) was introduced as an important clinical entity in 1980. Previously, it had received little mention in the literature and was not considered to be clinically relevant. MDI is a symptomatic glenohumeral subluxation or dislocation occurring in more than one direction. The basic pathology of this condition is a loose and redundant joint capsule. Most patients with MDI can be treated successfully by conservative methods, such as patient education, a shoulder girdle strengthening program, or modification of the patient's routine activity.

Arthroscopy↗
PubMed2000

Pre-clinical in vivo evaluation of orthopaedic bioabsorbable devices.

The presence of bioabsorbable materials in orthopaedics has grown significantly over the past two decades with applications in fracture fixation, bone replacement, cartilage repair, meniscal repair, fixation of ligaments, and drug delivery. Numerous biocompatible, biodegradable polymers are now available for both experimental and clinical use. Not surprisingly, there have been a wealth of studies investigating the biomechanical properties, biocompatibility, degradation characteristics, osteoconductivity, potential toxicity, and histologic effects of various materials. Promising results have been reported in the areas of fracture fixation, ligament repair, and drug delivery. In this article we review the pre-clinical in vivo testing of bioabsorbable devices with particular emphasis on implants used for these applications.

Absorbable Implants↗
PubMed2000

Cost analyses of extended prophylaxis with enoxaparin after hip arthroplasty.

Venous thromboembolic complications occur in 50% to 70% of patients undergoing total hip arthroplasty if no prophylactic regimen is used. Because enoxaparin and warfarin are useful for extended outpatient prophylaxis, the objective of this study was to determine which of these agents is most cost effective in preventing venous thromboembolic complications. A decision tree analysis was developed to simulate a hypothetical cohort of patients with total hip arthroplasty. The analysis considered home health care services to perform monitoring and compliance verification. Accounting for prophylactic failures and treatment complications, results showed that enoxaparin maintained a cost effective advantage over warfarin for extended prophylaxis in the time after discharge and total hip arthroplasty ranging from 19 to 31 days after the patient was discharged from the hospital. The duration of cost effectiveness of enoxaparin was reduced to 14 to 17 days when home care services were excluded. These results indicated that approximately 3 weeks of outpatient therapy with enoxaparin is cost effective. With the cornerstone of managed care being cost efficiency in the provision of quality care, this conclusion warrants the development of integrated care strategies for the patient having orthopaedic surgery to achieve cost effective patient management.

Anticoagulants↗
PubMed1999

Enactments: an intersubjective perspective.

We offer a critique and synthesis of classical and interpersonal views of enactment. From an intersubjective standpoint, the study of enactment leads to a reconsideration of the nature of the psychoanalytic process. And enactment becomes virtually synonymous with the psychoanalytic process. Enactments are interactions of analysand and analyst with communicative and resistive meanings that lead to valuable insight and can constitute corrective emotional experiences. Enactments that are recognized and defined become valuable dramatizing moments that have condensing, clarifying, and intensifying effects upon consciousness. The inevitable participation by the analyst in enactment is compatible with appropriate analytic discipline. A case will demonstrate these points.

Adult↗
PubMed1999

The role of low molecular weight heparin in total knee arthroplasty.

Low-molecular-weight heparin prophylaxis is an acceptable, if not superior, alternative to heparin and warfarin prophylaxis in TKA. Considering the current popularity of pharmacologic prophylaxis after total hip and total knee arthroplasty and the advantages of low-molecular-weight heparins over traditional pharmacologic agents, these agents have the potential to become the prophylactic agent of choice against DVT in TKA. There are several practical differences between low molecular weight heparins and warfarin. Low molecular weight heparins are administered by subcutaneous injection and do not require drug-level or blood monitoring. Warfarin, although administered orally, must be maintained within an appropriate international normalized ratio (INR=2-3) with daily dose adjustments and takes 36 hours to produce a measurable effect, which may leave patients relatively unprotected during the early postoperative period. Comparative trials have demonstrated that low molecular weight heparins are more efficacious than warfarin in producing a greater overall reduction in the incidence and risk of DVT, but show similar rates of PE. Some studies suggest that bleeding may be a greater problem with low molecular weight heparin. Despite the superior efficacy of low molecular weight heparin, the prevalence of venous thromboembolism after TKA continues to be substantial compared with total hip arthroplasty, with at least a quarter of patients still affected. Additional prophylaxis strategies for this indication are needed and could include combining mechanical prophylaxis (eg, external pneumatic compression) with low molecular weight heparin. An appropriate management strategy should be established for all patients undergoing TKA. This should include identification of high-risk patients, cautious transfusion of blood products, pharmacologic prophylaxis with an acceptable agent for TKA, early mobilization, postoperative screening in high-risk patients, and continuing pharmacologic prophylaxis for an appropriate period postoperatively.

Anticoagulants↗
PubMed1998

Concise review of mechanisms of bacterial adhesion to biomaterial surfaces.

This article reviews the mechanisms of bacterial adhesion to biomaterial surfaces and the factors affecting the adhesion. The process of bacterial adhesion includes an initial physicochemical interaction phase (phase one) and a late molecular and cellular interaction phase (phase two), which is a complicated process affected by many factors, including the characteristics of the bacteria themselves, the target material surface, and the environmental factors, such as the presence of serum proteins or bactericidal substances.

Bacterial Adhesion↗
PubMed1998

Bone ingrowth to implant surfaces in an inflammatory arthritis model.

Many studies have shown enhanced bone apposition to implants coated with hydroxyapatite, but the optimum implant texture, especially in abnormal trabecular bone, is unclear. The purpose of this project was to evaluate the histological and mechanical properties of cylindrical implants with three different surface textures that were placed in the cancellous bone of the distal femur of the rabbit after the production of an inflammatory knee arthritis. The three implant surfaces included a beaded surface (Group A), a beaded surface coated with hydroxyapatite (Group B), and a smooth surface coated with hydroxyapatite (Group C). The right knees of 36 rabbits were injected with carrageenan twice a week for 2 weeks. Then bilateral implantations were performed, with 12 rabbits in each group receiving identical implants in the right and left knees. The rabbits were killed 6 weeks after surgery. Mechanical (push-out test) and histomorphometric analyses were performed to determine the quality and quantity of bone ingrowth. In Group A, there was virtually no direct contact (a 20-60-microm clearance) between the bone and the beaded surfaces. Direct contact between the bone and the implant surfaces was seen in Groups B and C. The thickness and number of trabeculae were smaller on the arthritic side than on the control side for all groups but were not different between groups for either the control or the arthritic side. Mechanical testing showed that the shear strength of the interface was weaker on the arthritic side in all groups. The results suggest that inflammatory arthritis induced by carrageenan may influence the quality of local bone (osteopenic changes) and hence compromise the bone apposition and mechanical stability of the interface between the implant and bone.

Animals↗
PubMed1998

[Instability of the sternoclavicular joint].

Instability of the sternoclavicular joint is a rare diagnosis and will mostly be found after motor vehicle accidents or sports injuries. Depending on the severity of the trauma open reduction is rarely required, and most cases will be treated successfully with conservative management. Associated injuries to the surrounding anatomic structures are not rare, and can be found in posteriorly directed injuries.

Accidents, Traffic↗
PubMed1998

Humeral technique in total shoulder arthroplasty.

Humeral head replacement arthroplasty has been performed for more than 40 years. As the technique has been refined and advances have been made in joint arthroplasty of the lower extremity, the indications and success of shoulder arthroplasty have greatly improved. The humeral component in a shoulder arthroplasty can be implanted with either cement or press fit fixation. Both techniques are precise and demand meticulous attention to detail to achieve optimum results for the patient. Press fit fixation, with or without porous coating for biologic ingrowth, can be considered for a patient with good bone stock, if it is felt that a stable interface can be obtained. In patients with abnormal bone, such as those with rheumatoid arthritis who are on corticosteroids and those with osteoporosis, the use of cement can provide stable long-term fixation.

Adrenal Cortex Hormones↗
PubMed1998

Shoulder hemiarthroplasty for proximal humeral fractures.

Shoulder hemiarthroplasty is a well-accepted surgical procedure for the treatment of specific subtypes of proximal humeral fractures, including four-part fractures, three-part fractures associated with severe osteopenia, head-splitting and severe articular impression fractures. Careful patient assessment and meticulous surgical technique are essential to prevent complications. The results are satisfactory in approximately 80% of cases. The results are better in younger patients and in acute versus chronic fractures. There are a significant number of complications that are related to technical details of the procedure. Careful placement of the prosthesis and secure reattachment of the tuberosities to the shaft reduce the chance of complication following surgery. Good to excellent results in terms of range of motion and pain relief can be expected in most patients.

Acute Disease↗
PubMed1998

Postoperative rehabilitation following total shoulder arthroplasty.

It is essential that patients receive proper rehabilitation following a total shoulder arthroplasty. This should ideally include a preoperative visit that includes the specified therapist, patient, and primary caregiver. The rehabilitative process is an individual program, and the protocol described is suggested as a guide for the therapist. The order of the exercises listed is more important than the time at which they are started, with an emphasis on maximizing motion prior to aggressive strengthening.

Arthroplasty, Replacement↗
PubMed1998

Morphological and mechanical study on the effects of experimentally induced inflammatory knee arthritis in rabbit long bones.

Inflammatory knee arthritis was induced by intraarticular injection of carrageenan twice a week for a total of 6 weeks in New Zealand White rabbits and the effects of the arthritis on the morphological and mechanical properties of the adjacent femur and tibia were evaluated 8 weeks after the first injection. Carrageenan-induced knee arthritis resulted in severe osteopenic changes and a dramatic decrease in bone strength of the entire ipsilateral femur and tibia, including the femoral head and distal tibia, but not the contralateral femur and tibia and the remote humerus. The osteoporotic changes of the adjacent bones of the inflammatory arthritic knee are the basis for the reduced mechanical strength of these bones. These findings may have clinical significance with regard to the mechanisms and consequences of osteoporotic changes in patients with rheumatoid arthritis.

Journal Article↗
PubMed1998

Fixation of osteotomies using bioabsorbable screws in the canine femur.

The purpose of this study was to compare the healing properties of femoral osteotomies fixed by bioabsorbable screws (20:80 polyglycolic copolylactic acid copolymer) to standard stainless steel screws of a similar design in a dog femoral model. Two osteotomies were used, the trephine osteotomy (10 mm diameter) in the metaphyseal lateral femoral condyle and in the femoral diaphysis, and a unilateral osteotomy in the lateral femoral condyle. Two months after the trephine osteotomies, the femurs that contained the polymer screws were not significantly different in mechanical strength from the femurs treated with the stainless steel screws, either in the diaphyseal or metaphyseal model. There was no histological difference in bone healing between the metallic and polymer screws for all periods (2, 9, and 17 months). There was no adverse inflammatory response to the polymeric or metallic screws. By month 17, the polymer screws were resorbed completely. All the diaphyseal screw tracks had healed with bone and areas of remodeling were evident in two specimens. For the femoral condyle osteotomy model at 2 months, the polymer screws were present and intact, and all osteotomies healed with no evidence of inflammation. By 9 months, only one specimen had polymeric material left in the screw track. At 15 months, the screw tracks still were present but no evidence of any polymer remained. The tracks were filled with fibrous and adipose connective tissue. All osteotomies stabilized with either bioabsorbable polymer screws or stainless steel screws did heal satisfactorily without any complications, inflammation, or osteolysis. The polyglycolic polylactic acid copolymer may have a clinical role as a bioabsorbable material without the concerns for the osteolysis, foreign body reaction, and sterile abscess formation that have occurred with bioabsorbable fixation methods in the past.

Absorbable Implants↗