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Biomedical subjects

C B Sledge

Publications and source records attributed to C B Sledge.

At least 73 records · Page 4Linked to original sources
PubMed1988

Use of liposomes as carriers for radiation synovectomy.

Using [99mTc]pertechnetate as an aqueous space marker, the permeability of liposomes composed of seven different mixtures of distearoylphosphatidylcholine (DSPC) and sphingomyelin (SM) was determined. Liposomes containing 20-33% SM were the least permeable in the presence of rheumatoid synovial fluid. Following injection of 99mTc-containing liposomes into the knee joints of rabbits, retention of 99mTc in the knee was more than 200 times greater than following injection of nonencapsulated [99mTc]pertechnetate. The knee clearance biologic half time of 99mTc with DSPC/SM (4:1) liposomes was 64 h. Most of the activity that had leaked from the knee was not found in extra-articular tissues, suggesting rapid excretion. When DSPC/SM (4:1) liposomes were labeled with 111In(oxine), a knee clearance biologic half time of greater than 1200 h was observed.

Animals↗
PubMed1988

The effects of modern cementing techniques on the longevity of total hip arthroplasty.

Modern prosthetic design and cementing techniques have dramatically improved femoral component fixation. Compared to studies reported in the 1970s, the incidence of radiographic loosening for periods up to 5 years postoperatively has been reduced by at least a factor of 10. These results are the benchmark by which alternative forms of femoral component fixation must be measured. With the likelihood of increased longevity of total hip arthroplasty resulting from improved fixation, the problems of wear debris from the bearing surfaces and loss of bone stock with time will become preeminent.

Bone Cements↗
PubMed1988

Strategies for improving fixation of femoral components in total hip arthroplasty.

As strategies are considered for improving fixation of femoral components in total hip arthroplasty (THA), one is challenged to exceed the standard set by contemporary cement procedures. However, despite the improved ten- to 15-year clinical results anticipated with current cementing techniques, the limited fatigue strength of polymethylmethacrylate warrants continued investigation of alternative systems, particularly for younger patients and in revision arthroplasty. Design considerations for femoral stems for cementless THA include (1) initial mechanical stability afforded by the stem shape, (2) strength and stiffness of the stem, and (3) surface features relating to biocompatibility and attachment to bone. In one approach a fit-and-fill algorithm has been implemented to design stems that maximize contact between prosthesis and cortex in priority areas to achieve stability. Titanium is recommended for the fabrication of such stems because of its corrosion resistance, its biocompatibility, and its modulus, which is lower than that of cobalt-chromium alloy. Long-term fixation of these implants will be dependent upon the maintenance of normal strain patterns in the host bone. Achievement of this goal will require additional strategies that combine optimal fit and optimal material properties of the prosthesis.

Biocompatible Materials↗
PubMed1987

Cyclic AMP-regulating agents inhibit endotoxin-mediated cartilage degradation.

The influence of cyclic AMP on cartilage degradation was investigated by using phosphodiesterase inhibitors [theophylline and 3-isobutyl-1-methylxanthine (IBMX)], forskolin (which activates the catalytic subunit of adenylate cyclase) and cyclic AMP analogues (dibutyryl and 8-bromo). Breakdown was assessed by quantification of proteoglycans released into the media of 8-day bovine nasal-septum cartilage cultures. Theophylline (1-20 mM), IBMX (0.01-2 mM) and dibutyryl cyclic AMP (0.1-2 mM) had little or no influence on the rate of proteoglycan release from unstimulated (no-endotoxin) cartilages. A small but detectable increase in breakdown was observed with 8-bromo cyclic AMP (0.5-2 mM) and forskolin (50-75 micrograms/ml). To examine potential inhibitory influences of these agents, the cyclic AMP modulators were added to cultures simultaneously treated with Salmonella typhosa endotoxin (12-25 micrograms/ml), a potent stimulator of cartilage degradation. The 3-4-fold stimulation of breakdown by endotoxin was strikingly inhibited by all three classes of cyclic AMP regulators. Optimal inhibition was found at 10-20 mM-theophylline, 1-2 mM-IBMX, 50-75 micrograms of forskolin/ml, 2 mM-dibutyryl cyclic AMP and 2 mM-8-bromo cyclic AMP. Inhibition was shown to be reversible, indicating that cartilages were viable after treatment. Sepharose CL-2B chromatography of proteoglycan products released from treated cartilages showed that the endotoxin-stimulated shift to lower average Mr was significantly prevented by cyclic AMP analogues and phosphodiesterase inhibitors. Together, these results show that agents which increase cyclic AMP inhibit both quantitative and qualitative aspects of endotoxin-mediated cartilage degradation.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Experimental arthritis induced by polysaccharide macromolecules.

Several polysaccharide macromolecules are capable of inducing synovial inflammation. Characteristics of polysaccharides that have this capacity were studied in an in vivo rabbit model. The ability to induce synovial inflammation was positively correlated with the presence of sulfate and with high molecular weight. Understanding the characteristics of molecules that produce inflammation may help in the investigation to determine what mechanisms initiate the inflammatory response.

Animals↗
PubMed1987

Treatment of rheumatoid arthritis using radiopharmaceuticals.

One hundred and twenty one knees in 97 patients with seropositive rheumatoid arthritis and persistent knee synovitis were treated with the intra-articular injection of 270 mCi (30 GBq) of dysprosium-165 (165Dy) bound to ferric hydroxide macroaggregates. Of 81 knees evaluated at one year, 61% had good results, 23% had fair results and 16% had poor results. Of 44 knees evaluated at two years, 64% had good results, 16% had fair results and 20% had poor results. Knees with Stage I radiographic changes showed 72 and 81% good results at one and two years, respectively. Knees and Stage II radiographic changes showed 53 and 48% good results at one and two years, respectively. Leakage of radioactivity from the injected joint was minimal. Mean leakage to the venous blood was 0.15% of the injected dose. Mean leakage to the liver 24 h after injection was 0.64% of the injected dose. Mean leakage to the draining inguinal lymph nodes was 0.17% of the injected dose. These results indicate that 165Dy-ferric hydroxide macroaggregate is an effective agent for radiation synovectomy, particularly in knees with Stage I radiographic changes. The minimal leakage rates observed offer a definite advantage over previously used agents.

Adult↗
PubMed1987

Chondrocyte-mediated breakdown of cartilage.

Chondrocyte-mediated degradation of cartilage was studied using bovine nasal cartilage discs cultured for up to 8 days in the presence or absence of chemically defined agents. Breakdown, assessed quantitatively as proteoglycan released into culture medium and qualitatively by gel filtration of (medium and cartilage) products, was potently stimulated by highly purified interleukin-1 (IL-1), bacterial lipopolysaccharides, and prostaglandin F2 alpha. IL-1 action was abolished by anti-IL-1 antibodies but unaffected by hydrocortisone. LPS-stimulated breakdown was reversibly inhibited by glucocorticoid hormones, indomethacin, and cAMP. In addition to their usefulness in probing chondrocyte degradative pathways, several of these agents may be of pathogenetic and clinical significance.

Animals↗
PubMed1987

The weight-bearing shoulder. The impingement syndrome in paraplegics.

The cases of ninety-four patients who had complete paraplegia were studied to determine whether they had complaints about the shoulder during transfer activities. Thirty-one patients reported pain on transferring, and twenty-three of these patients were found to have a chronic impingement syndrome with subacromial bursitis. Arthrography of the shoulder was done for each of these twenty-three patients, and fifteen were found to have a tear of the rotator cuff. Five of the thirty-one patients were found to have aseptic necrosis of the head of the humerus. We also measured the intra-articular pressure in the shoulder in five patients during different activities, including transfer from wheelchair to bed, and found that this pressure exceeded the arterial pressure by two and one-half times. We believe that this high pressure, in conjunction with abnormal distribution of stress transmitted across the subacromial area during transfer or propulsion of a wheelchair, contributes to the high rate of problems about the shoulder in paraplegics.

Arthrography↗
PubMed1987

Synovectomy of the rheumatoid knee using intra-articular injection of dysprosium-165-ferric hydroxide macroaggregates.

One hundred and eleven patients who had seropositive rheumatoid arthritis and persistent synovitis of the knee were treated with intra-articular injection of 270 millicuries of dysprosium-165 bound to ferric hydroxide macroaggregates. A two-year follow-up was available for fifty-nine of the treated knees. Thirty-nine had a good result; nine, a fair result; and eleven, a poor result. Of the twenty-five knees that had Stage-I radiographic changes, nineteen had a good result. Of the thirty-four knees that had Stage-II radiographic changes, twenty showed a good result. Systemic spread of the radioactivity from the injected joint was minimum. The mean whole-body dose was calculated to be 0.3 rad and that to the liver twenty-four hours after injection, 3.2 rads. The results indicated that dysprosium-165-ferric hydroxide macroaggregate is an effective agent for performing radiation synovectomy, particularly in knees that have Stage-I radiographic changes. Because of the minimum rate of systemic spread of the dysprosium-165, it offers a definite advantage over agents that previously have been used.

Adult↗
PubMed1986

Treatment of rheumatoid synovitis of the knee with intraarticular injection of dysprosium 165-ferric hydroxide macroaggregates.

One hundred eight knees of 93 patients with seropositive rheumatoid arthritis and persistent synovitis of the knee were treated with an intraarticular injection of 270 mCi of dysprosium 165 bound to ferric hydroxide macroaggregate. Leakage of radioactivity from the injected joint was minimal. Mean leakage to the venous blood 3 hours after injection was 0.11% of the injected dose; this corresponds to a mean whole body dose of 0.2 rads. Mean leakage to the liver 24 hours after injection was 0.64% of the injected dose; this corresponds to a mean liver dose of 3.2 rads. In 7 additional patients examined, there was negligible or near negligible activity found in the draining inguinal lymph nodes. One-year followup was possible for 74 knees (63 patients). Sixty-one percent of the knees had good results, 23% had fair results, and 16% had poor results. There was a direct correlation between the radiographic stage and response to treatment. In knees with stage I radiographic changes, 72% showed good results; 93% showed improvement. In knees with stage II changes, 59% showed good results; 81% showed improvement. These preliminary results indicate that dysprosium 165-ferric hydroxide macroaggregate is an effective agent for radiation synovectomy. The low leakage rates observed offer a definite advantage over agents previously used.

Adult↗
PubMed1986

Cost-effectiveness of total joint arthroplasty in osteoarthritis.

Although total joint replacement (TJR) is a major advance in the treatment of patients with osteoarthritis, its cost-effectiveness has been questioned. We report the results of a study of the costs and benefits of TJR in consecutive osteoarthritis patients, 6 months after the surgery. Health status was measured by the Index of Well-Being. Costs of services for arthritis were determined by interview and billing records. Six months after TJR, significant improvements were seen in global health and in functional status. The average cost of care for the 6 months prior to TJR was $933. The average cost during the 6 months beginning with the TJR was $22,730 per patient--due almost entirely to costs of surgery. In general, the surgery did not change work status, probably because the mean age of the patients was 66.4 years. There were large effectiveness/cost differentials (the larger the effectiveness/cost differential, the higher the degree of cost-effectiveness [CE]). At 6 months, for all patients, the CE was associated with initial health status. The highest CE was observed in 10 patients who initially had the poorest health. TJR is more cost-effective for patients with the most to gain and less effective for those with better preoperative health status.

Aged↗
PubMed1986

Radiation synovectomy with 165Dy-FHMA: lymph node uptake and radiation dosimetry calculations.

The lymph node uptake of 165Dy was measured in 25 patients treated by radiation synovectomy via intra-articular injection of 165Dy-ferric hydroxide macroaggregates (FHMA). An average of 0.12% of the injected dose was found in the inguinal lymph nodes 19h post injection. This results in a lymph node of 16.6 rad (166 mGy), a dose significantly less than that reported following radiation synovectomy with other radiocolloids. Dosimetry calculations for the intra-articular injection of 165Dy-FHMA are provided in the appendix.

Arthritis, Rheumatoid↗
PubMed1986

Effects of total knee replacement design on femoral-tibial contact conditions.

Ten fresh knee specimens with prosthetic components inserted were tested in a loading rig. Compressive and shear force were applied to the femur with the tibia held fixed. The location of the femoral-tibial contact points was measured. The contact reaction forces, the shear forces, and the rocking moments transmitted to the tibial component were calculated. The variations in the test conditions were: high and low compressive force, flexion angles of 0 degree, 45 degrees, and 90 degrees, three curvatures of tibial plastic inserts, and the posterior cruciate retained or resected. When the posterior cruciate was retained, the contact points were close to the center of the component; for cruciate resection, the contacts were close to the anterior of the component. The shear forces and rocking moments were higher for cruciate resection, but the contact reaction forces were lower. There is a wide variety of knee prosthesis designs, but the amount of inherent stability between the femoral and tibial surfaces, and whether the posterior cruciate ligament is retained or sacrificed, are two of the most important design variables. This study shows that cruciate resection increases the shear forces and the rocking moments to the tibial components and that additional fixation means may be necessary to compensate. On the other hand, cruciate retention with low conformity gives higher contact forces, which may lead to more wear in the long term. Cruciate sacrificing designs with intercondylar guiding surfaces are a separate category of design and were not considered in this study.

Biomechanical Phenomena↗
PubMed1985

Total knee arthroplasty in rheumatoid arthritis.

Total knee replacement in rheumatoid arthritis has evolved into a very reliable procedure for the relief of pain and restoration of function. Minimum of two year follow-ups using the most recent components and surgical techniques show that pain relief is good in 97 per cent of patients and range of motion averages 111 degrees. Although the rheumatoid patient presents many potential hazards and problems because of systemic disease most of these can be minimized or overcome by meticulous attention to pre-operative evaluation, planning, and operative technique.

Arthritis, Rheumatoid↗
PubMed1985

Total joint replacement: latest developments for the geriatric patient.

Total joint replacement has significantly improved the treatment of patients with severe, disabling arthritis. Following replacement of the hip, knee, shoulder, or elbow, the vast majority of patients can expect excellent pain relief and functional improvement. The components of a successful total joint replacement include proper patient selection, optimal preoperative and postoperative management of associated medical problems, meticulous surgical technique, a comprehensive rehabilitation program, and proper prophylaxis against infection.

Adrenal Cortex Hormones↗
PubMed1985

Long-term results of revision total hip replacement. A follow-up report.

The results of 110 revision total hip replacements performed for aseptic failure, with an average follow-up of 3.4 years, were reported in 1982. We were able to continue to follow ninety-nine of these patients for an average of 8.1 years (range, five to 12.5 years). With this longer follow-up, we found that twenty-nine (29 per cent) of these revised arthroplasties have since failed. Most of the failures after 1982 occurred in the hips that were known to have a progressive radiolucency at the time of the first evaluation. We concluded that there is an increased failure rate with longer follow-up of revision total hip replacement, and that progressive radiolucency at an interface indicates a poor prognosis for the arthroplasty.

Activities of Daily Living↗
PubMed1984

Kinematic total knee replacement.

We reviewed 124 consecutive kinematic condylar total knee replacements (in ninety-one patients) at two to four years postoperatively. One hundred and eleven (90 per cent) were rated as good or excellent. The average active postoperative flexion was 106 degrees (range, 94 to 120 degrees). Twenty-two knees (18 per cent) had incomplete, non-progressive radiolucent lines, less than one millimeter in width, at the tibial bone-cement interface; these were considered insignificant. Restriction of stair-climbing ability in this series appeared to be a function of involvement of multiple joints rather than of patellar replacement, as the rheumatoid patients with resurfaced patellae performed the worst. The osteoarthritic patients with involvement of a single joint performed the best, regardless of whether the patella was resurfaced or not. When compared with a similar series of total knee replacements in which the tibial component was made entirely of plastic, less reaction at the bone-cement interface was found with the metal-backed kinematic tibial component. We suggest that this finding is clinical confirmation of in vitro studies that demonstrated the advantage of metal-backed tibial components. We concluded that this procedure, if meticulously performed, will give predictably good to excellent results with a low complication rate, a good postoperative range of motion, and a favorable-appearing bone-cement interface at two to four years.

Adult↗