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Biomedical subjects

W H Thomas

Publications and source records attributed to W H Thomas.

At least 19 recordsLinked to original sources
PubMed2001

Detection and quantification of snow algae with an airborne imaging spectrometer.

We describe spectral reflectance measurements of snow containing the snow alga Chlamydomonas nivalis and a model to retrieve snow algal concentrations from airborne imaging spectrometer data. Because cells of C. nivalis absorb at specific wavelengths in regions indicative of carotenoids (astaxanthin esters, lutein, beta-carotene) and chlorophylls a and b, the spectral signature of snow containing C. nivalis is distinct from that of snow without algae. The spectral reflectance of snow containing C. nivalis is separable from that of snow without algae due to carotenoid absorption in the wavelength range from 0.4 to 0.58 microm and chlorophyll a and b absorption in the wavelength range from 0.6 to 0.7 microm. The integral of the scaled chlorophyll a and b absorption feature (I(0.68)) varies with algal concentration (C(a)). Using the relationship C(a) = 81019.2 I(0.68) + 845.2, we inverted Airborne Visible Infrared Imaging Spectrometer reflectance data collected in the Tioga Pass region of the Sierra Nevada in California to determine algal concentration. For the 5.5-km(2) region imaged, the mean algal concentration was 1,306 cells ml(-1), the standard deviation was 1,740 cells ml(-1), and the coefficient of variation was 1.33. The retrieved spatial distribution was consistent with observations made in the field. From the spatial estimates of algal concentration, we calculated a total imaged algal biomass of 16.55 kg for the 0.495-km(2) snow-covered area, which gave an areal biomass concentration of 0.033 g/m(2).

Aircraft↗
PubMed1999

Kinematic total knee arthroplasty: a 10- to 14-year prospective follow-up review.

To understand better the type and incidence of long-term complications in total knee replacement, 306 primary Kinematic total knee arthroplasties performed between June 1978 and December 1982 were prospectively reviewed in detail. The Kinematic knee is a nonconstrained, posterior cruciate-retaining prosthesis that has right and left femoral components to afford anatomic tracking of the patella. The overall revision rate was 6.5%. The most common cause for revision surgery was patellar complications. Ten revisions (3.06%) were for patellar component loosening. Two knees were revised for patella subluxation (0.65%); 1 was in a resurfaced rheumatoid patella, and 1 in an unsurfaced osteoarthritic patella. Stair climbing was better with an unsurfaced patella. Anterior knee pain was 21.8% in the unsurfaced patella and 11.2% in the replaced patella. These data suggest patella replacement is not appropriate with this design.

Arthroplasty, Replacement, Knee↗
PubMed1997

Management of the rheumatoid hindfoot with special reference to talonavicular arthrodesis.

In the patient with rheumatoid arthritis, involvement of the hindfoot is common. If conservative management fails, surgical treatment should be considered before the development of a fixed deformity. In patients with isolated talonavicular disease, arthrodesis of this joint provides excellent pain relief and seems to prevent future deformity.

Arthritis, Rheumatoid↗
PubMed1997

Total hip arthroplasty with cement for juvenile rheumatoid arthritis. Results at a minimum of ten years in patients less than thirty years old.

We retrospectively reviewed the clinical and radiographic results of total hip arthroplasty with cement in patients with juvenile rheumatoid arthritis who were less than thirty years old at the time of the index procedure. Thirty-nine patients (sixty-six hips) were managed with this procedure at our institution between 1971 and 1983. Six patients (eleven hips) died before a minimum of ten years of follow-up; the remaining thirty-three patients (fifty-five hips) were followed for at least eleven years. Twenty-eight patients (forty-six hips) had at least one original component in situ after an average duration of clinical follow-up of 15.1 years, and twenty-three of these patients (thirty-eight hips) were followed radiographically for an average of 14.7 years. At the time of the latest follow-up examination, all twenty-eight patients were able to walk outside the home; twenty of these patients (thirty-five hips; 76 per cent) had no pain with activity, and eight patients (eleven hips; 24 per cent) had mild-to-moderate pain with activity. Over-all, twelve (18 per cent) of the sixty-six femoral components and twenty-three (35 per cent) of the sixty-six acetabular components were revised after an average of 12.8 and 11.8 years, respectively. The fifteen-year survival rate for the femoral components was 85 per cent with revision or radiographic loosening as the end point. The fifteen-year survival rate for the acetabular components was 70 per cent with revision as the end point and 61 per cent with revision or radiographic loosening as the end point. The benefits of total hip arthroplasty were maintained over the long term in most of our patients who had juvenile rheumatoid arthritis. However, the durability of the components in these young patients remains a concern.

Adolescent↗
PubMed1996

Early failure of Hylamer acetabular inserts due to eccentric wear.

The authors performed a retrospective review of the survivorship of Hylamer (DePuy Dupont Orthopaedics, Warsaw, IN) acetabular liners following primary arthroplasty of the acetabulum. Between 1990 and 1992, 193 total hip arthroplasties were performed in which Hylamer acetabular liners were implanted. One hundred forty-three of these hips (74%) were available for clinical and radio-graphic follow-up evaluation after a minimum of 2 years. The mean follow-up period was 2.5 years. Five Hylamer liners have been revised for eccentric wear at a mean of 37 months postimplantation and one additional liner is scheduled to be revised at the 34-month follow-up evaluation (total, 4.2% failure rate due to wear). Survivorship of the Hylamer liner, with failure defined as revision due to eccentric wear, was calculated to be 86% (SE, 5.5%) at 4 years. The authors have discontinued the use of Hylamer acetabular liners because of this high early failure rate.

Acetabulum↗
PubMed1995

Replacement of "other" joints.

Replacement of larger joints other than the hip and knee has been relatively disappointing and remains in a developmental stage. In the small joints, initial enthusiasm for silicone rubber arthroplasty has diminished in all sites except the MCPs because of the recognition of the high frequency of silicone synovitis. Further research and development is ongoing. This article was intended to facilitate understanding of the choices of operative procedures, the types of available components, and particularly, the specifics of radiographic assessment of the success or failure of these "other" prostheses. We hope this information will be helpful in assessing postoperative radiographs, as "We only see what we look for and we only look for what we know."

Ankle Joint↗
PubMed1994

Failure of ritanserin to block the discriminative or reinforcing stimulus effects of cocaine.

Ritanserin, a 5-HT2/1C antagonist, has been suggested to reduce the preference for cocaine in rats. In the present experiment, the action of ritanserin was investigated in locomotor activity, cocaine drug discrimination, and cocaine self-administration paradigms in rats. A low dose of ritanserin (1.0 mg/kg) was without effect on locomotor activity, while a higher dose (10.0 mg/kg) reduced both horizontal and vertical locomotor activity counts during the first 30 min of the test session. Ritanserin (0.32-32 mg/kg) did not significantly affect the discrimination of 10 mg/kg of cocaine, nor did a dose of 10.0 mg/kg significantly modify the dose-effect curve for cocaine discrimination. Ritanserin (1.0 and 10.0 mg/kg) had no significant effect on the dose-response curve for cocaine self-administration. Thus, ritanserin was without effect against either the discriminative or reinforcing stimulus effects of cocaine, suggesting that ritanserin has limited efficacy as a potential treatment for cocaine abuse.

Animals↗
PubMed1993

Capitellocondylar total elbow replacement in rheumatoid arthritis. Long-term results.

We evaluated the long-term results of 202 capitellocondylar total elbow replacements that had been performed, from July 1974 through June 1987, in 172 patients. The duration of follow-up averaged sixty-nine months (range, twenty-four to 178 months). At the most recent follow-up examination, use of a 100-point rating score demonstrated an improvement from an average preoperative score of 26 points (range, 2 to 50 points) to an average postoperative score of 91 points (range, 45 to 100 points). The most improvement occurred in the categories of relief of pain, functional status, and range of motion in all planes except extension. The improvements in these categories and in the roentgenographic appearance that were seen in the early postoperative period did not deteriorate with time. The average preoperative arc of motion at the elbow ranged from -37 degrees of extension to 118 degrees of flexion. The average postoperative arc of motion at the elbow ranged from -30 degrees of extension to 135 degrees of flexion. Supination improved from 45 degrees preoperatively to 64 degrees postoperatively; pronation improved from 56 degrees preoperatively to 72 degrees postoperatively. The roentgenograms showed a radiolucent line adjacent to eight humeral and nineteen ulnar components; most of the lines were incomplete and one millimeter wide or less. Revision of the prosthesis was necessary in three elbows (1.5 per cent) because of loosening without infection, and in three additional elbows because of dislocation of the prosthesis. Complications included deep infection in three elbows (1.5 per cent); problems related to the wound in fifteen (7 per cent); permanent, partial sensory ulnar-nerve palsy in five (2.5 per cent); permanent, partial motor ulnar-nerve palsy in one (0.5 per cent); and dislocation in seven (3.5 per cent).

Adult↗
PubMed1993

Long-term complications after total knee arthroplasty with or without resurfacing of the patella.

The long-term complications related to the patella were retrospectively evaluated for 891 knees (684 patients) that had had a total arthroplasty, with or without resurfacing of the patella, with use of an unconstrained, condylar, posterior-cruciate-preserving prosthesis. The study population comprised two groups of patients who were similar in size, age, sex distribution, and diagnosis. One group (396 knees [303 patients]) had had a total knee arthroplasty with patellar resurfacing and the other group (495 knees [381 patients]) had had the same procedure without resurfacing. The average duration of follow-up was six and one-half years (range, two to fifteen years). The decision to resurface the patella was based on subjective inspection of the articular surface and on assessment of patellar tracking at the time of the operation. Resurfacing was performed if there was loss of cartilage, exposed bone, gross surface irregularities, or tracking abnormalities. Complications occurred an average of three years (range, immediately postoperatively to nine years) after the operation in the group that had had resurfacing and an average of four years (range, immediately post-operatively to ten years) postoperatively in the group that had not had resurfacing. In the group that had had resurfacing, there was loosening of the patellar component in five knees, patellar subluxation in four knees, fracture of the patella in three knees, rupture of the patellar tendon in three knees, and chronic peripatellar pain in one knee. In the group that had not had resurfacing, the complications included patellar subluxation in five knees, rupture of the patellar tendon in two knees, and chronic peripatellar pain in fifty-one knees.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Total shoulder arthroplasty versus hemiarthroplasty. Indications for glenoid resurfacing.

The results of total shoulder arthroplasty and hemiarthroplasty in a similar patient population were compared in an effort to define more clearly the indications for resurfacing the glenoid. The results of 64 Neer hemiarthroplasties in 59 patients were compared with 146 Neer total shoulder arthroplasties in 134 patients in a retrospective review of the period between 1974 and 1986. The average follow-up period was 44 months (range, 24-124 months). Hemiarthroplasty and total shoulder arthroplasty produced similar results in terms of functional improvement. Pain relief, range of motion, and patient satisfaction were better with total shoulder arthroplasty than hemiarthroplasty in the rheumatoid population. Progressive glenoid loosening was found in 12% of total should arthroplasties but no correlation with pain relief or range of motion was noted. Total shoulder arthroplasty is recommended for patients with inflammatory arthropathies, and hemiarthroplasty is recommended for patients with osteoarthritis, avascular necrosis, and four-part fractures with preservation of glenoid congruity and absent synovitis.

Adult↗
PubMed1990

Total knee arthroplasty with the kinematic prosthesis. Results after five to nine years: a follow-up note.

A review of the results of 192 kinematic total knee replacements five to nine years after the operation showed that the results were still satisfactory. At the time of the review, the ages of the patients ranged from twenty-two to eighty-seven years. About half of the patients had rheumatoid arthritis and the other half, osteoarthrosis. About 90 per cent of the results were rated good or excellent, and the average range of flexion was 109 degrees. Radiolucency was present around 40 per cent of the tibial components, 30 per cent of the femoral components, and 60 per cent of the patellar components, but the lines were thin and not progressive. The complications included loosening of the patellar components in five knees, one fracture of the tibial tray with loosening of the patellar component, one fracture of the patellar component, and one dislocation of the patellar component.

Adult↗
PubMed1989

Nonconstrained total shoulder arthroplasty in patients with polyarticular rheumatoid arthritis.

A retrospective review of 114 patients with polyarticular rheumatoid arthritis who had 140 total shoulder arthroplasties revealed that 93% of the patients had excellent pain relief; however, improvement in active forward elevation averaged 34 degrees. Nearly one-half of the patients had significant rotator cuff pathology. Three-fourths of the patients had a press-fit type of humeral component, and 5% of these have had variable amounts of subsidence. None have been sufficiently painful to require a revision. Eighty-two percent of the glenoid components developed radiolucent lines during the follow-up period. One percent of these were definitely loose and 9% were probably loose. To date, none have been revised. Complications occurred in 7% of the shoulders, but no deep or superficial wound infections were noted.

Adult↗
PubMed1989

Non-constrained total shoulder replacement in patients who have rheumatoid arthritis and class-IV function.

The results of twenty-four non-constrained total shoulder replacements that were done in twenty patients who had treatment of rheumatoid arthritis were retrospectively reviewed to determine how those results were affected by the severity of the disease. All of the patients had Class-IV functional capacity, and 92 per cent had Stage-III or IV rheumatoid progression. Nine (38 per cent) of the shoulders had a tear of the rotator cuff. The mean length of clinical follow-up was 4.5 years (range, two to ten years). Preoperatively, all of the patients had disabling pain and limited function. Postoperatively, twenty-two (92 per cent) of the patients had no appreciable pain, and eighteen (75 per cent) had no significant functional limitation (p less than 0.001). Active elevation improved by 88 per cent, and external and internal rotation also improved significantly. Motion, relief of pain, and functional improvement were not significantly greater in the patients who had an intact rotator cuff. Radiolucent lines developed around ten (42 per cent) of the glenoid prostheses, but only two of the prostheses were surrounded by a complete line and were thought to be loose. No revisions were done. We believe that a non-constrained total shoulder replacement affords excellent relief of pain, satisfactorily improves range of motion, and improves function in patients who have severe rheumatoid involvement of the shoulder. However, because motion and function are severely restricted preoperatively, the end-results are not comparable with those that have been reported for patients who have less severe rheumatoid disease.

Adult↗
PubMed1988

His+ reversions caused in Salmonella typhimurium by different types of ionizing radiation.

The yield of his+ reversions in the Ames Salmonella tester strain TA2638 has been determined for 60Co gamma rays, 140 kV X rays, 5.4 keV characteristic X rays, 2.2 MeV protons, 3.1 MeV alpha particles, and 18 MeV/U Fe ions. Inactivation studies were performed with the same radiations. For both mutation and inactivation, the maximum effectiveness per unit absorbed dose was obtained for the characteristic X rays, which have a dose averaged linear energy transfer (LET) of roughly 10 keV/micron. The ratio of the effectiveness of this radiation to gamma rays was 2 for inactivation and about 1.4 for the his+ reversion. For both end points the effectiveness decreases substantially at high LET, i.e., for the alpha particles and the Fe ions. The composition of the bottom and the top agar was the one recommended by Maron and Ames [Mutat. Res. 113, 173-215 (1983)] for application in chemical mutagenicity tests. The experiments with the less penetrating radiations differed from the usual protocol by utilization of a technique of plating the bacteria on the surface of the top agar. As in an earlier study [Roos et al., Radiat. Res. 104, 102-108 (1985)] greatly enhanced yields of mutations, relative to the spontaneous reversion rate, were obtained in these experiments by performing the irradiations 6 h after plating, which differs from the conventional procedure to irradiate the bacteria shortly after plating.

Alpha Particles↗
PubMed1987

Trochanteric advancement for recurrent dislocation after total hip arthroplasty.

Twenty-one patients had trochanteric advancement after experiencing an average of 3.9 dislocations in a mean period of 46 weeks following total hip arthroplasty. Before trochanteric advancement was performed, component malposition and mechanical impingement were excluded as causes of dislocation. Radiographic measurements revealed that the trochanter was advanced an average of 16 +/- 7.7 mm (1 SD). Four patients, all with rheumatoid arthritis, had trochanteric migration greater than 1 cm. Seventeen of the 21 hips had no further dislocations following trochanteric advancement, with mean follow-up period of 2.7 years. Two patients dislocated because of extremes in hip position and had no further dislocations. Two patients dislocated who had trochanteric migration greater than 1 cm. Only one patients with a technically satisfactory trochanteric advancement continued to dislocate repeatedly. In patients without component malposition or obvious sources of impingement, trochanteric advancement is an effective and safe procedure for prevention of recurrent dislocations after total hip arthroplasty.

Adult↗