Search PubMed⌕ Search

Biomedical subjects

R D Scott

Publications and source records attributed to R D Scott.

At least 91 records · Page 5Linked to original sources
PubMed1989

Unicompartmental knee arthroplasty. A 4.5-6-year follow-up study with a metal-backed tibial component.

The results in the first 50 patients to receive an improved-design unicompartmental knee prosthesis were reviewed after an average follow-up period of 5.5 years. The prosthesis is composed of a metal-backed polyethylene tibial component and a wide femoral surface replacement that are fixed to bone with acrylic cement. Forty-five patients with 55 unicompartmental knee arthroplasties were available for clinical study. Ninety-two percent of the knees were rated as having a good or excellent result, and 94% had lasting relief of pain. There have been no failures requiring revision. A radiographic review demonstrated that no tibial component was bordered by a complete radiolucent line. There was no subsidence or loosening of either the tibial or femoral components, and there was no instance of local osteolysis. These results, coupled with a 14-year follow-up experience with the original-design unicondylar prosthesis, encourages the authors to remain advocates of this procedure in selected patients with unicompartmental osteoarthritis.

Aged↗
PubMed1989

Blood supply to the patella. Significance in total knee arthroplasty.

Patellofemoral problems occur in approximately 5% of total knee arthroplasties and account for 50% of complications of total knee arthroplasty. Surgical disruption of the blood supply to the patella may cause an increase in the incidence of osteonecrosis, stress fracture, and loosening. The authors discuss patellar blood supply and surgical considerations in total knee arthroplasty and review the clinical experience with avascular patellae.

Adolescent↗
PubMed1989

Unicompartmental total knee arthroplasty.

This article traces the evolution of unicondylar design and examines its indications, common aspects of surgical technique independent of design, results, and complications. The dichotomy of opinion concerning unicompartmental knee arthroplasty may reflect differences in patient selection, prosthesis selection, and surgical technique.

Arthritis↗
PubMed1989

Rationale of the Knee Society clinical rating system.

A new total knee rating system has been developed by The Knee Society to provide an up-to-date more stringent evaluation form. The system is subdivided into a knee score that rates only the knee joint itself and a functional score that rates the patient's ability to walk and climb stairs. The dual rating system eliminates the problem of declining knee scores associated with patient infirmity.

Disability Evaluation↗
PubMed1989

Tibial tray augmentation with modular metal wedges for tibial bone stock deficiency.

Peripheral defects in the proximal tibia can be difficult to treat during total knee arthroplasty. Attempts can be made to solve the problem with cement, cement with screws, bone grafts, metal wedges, and custom components. In vitro testing has shown that a custom-augmented prosthesis with a built-up metal wedge is mechanically superior in resisting deflections when loaded. Using modular metal wedges, the tibial tray can be customized at the time of surgery. In vitro testing has also shown the wedge to be superior to the use of cement alone or cement reinforced by screws. The authors report on modular metal wedges to augment tibial bone stock deficiency. Twenty-two knees (20 patients) were followed for a minimum of two years with an average follow-up time of 37 months. The average age of the patients at the time of surgery was 70 years. There have been no failures of this technique and no loosening of tibial components. The incidence of nonprogressive radiolucent lines was 27%. All but one patient was pain-free, and this patient's discomfort was not related to the tibial component fixation. No patient has had subsequent revision surgery. This technique should be considered in the treatment of severe peripheral tibial deficiencies in the elderly, low-demand patient.

Aged↗
PubMed1989

Press-fit condylar total knee replacement.

In 1984 the press-fit condylar knee was first introduced and was intended to provide a condylar knee system primarily for posterior cruciate retention that addressed refinements in metallurgy, prosthetic geometry and sizing, cementless fixation, inventory management, and instrumentation. This article addresses the results observed in the use of this prosthesis.

Humans↗
PubMed1988

Surgical treatment of unicompartmental degenerative arthritis of the knee.

The number of patients with unicompartmental osteoarthritis is increasing with the average age of our population. Good surgical techniques are available to improve pain and increase motion in the knee with degenerative disease. It is important to make early accurate diagnoses in arthritic patients so that the least surgically ablative procedure can be performed that will maximally benefit each patient. Total knee replacement is an extremely effective operation for relieving pain, but its major drawback is the large amount of bone stock that must be sacrificed during the procedure. Unicondylar knee replacement has proven itself to be an excellent alternative to total knee replacement in more limited arthritic disease. High tibial osteotomy still plays a major role as treatment for unicompartmental arthritis in younger and more active patients. McKeever interpositional hemiarthroplasty is an alternative in young patients when osteotomy is contraindicated. Arthroscopy is playing an increasing role in both diagnosis and treatment of unicompartmental osteoarthritis. The decision to perform unicompartmental arthroplasty, osteotomy, or total knee replacement is made on an individual basis. The extent of cartilage degeneration in the knee as well as the age, weight, and activity demands of the patient help to guide that decision.

Arthroscopy↗
PubMed1988

Further observations on metal-backed patellar component failure.

The clinical data, failure pattern, symptoms, roentgenographic findings, and failure mechanism of a series of 25 metal-backed patellar component failures are summarized. Diagnosis of implant failure was unknown prior to arthrotomy in seven of 25 cases (28%). Clinical findings and history were not helpful in making the diagnosis. Roentgenographic findings led to the diagnosis in 17 of 18 and were by far the most useful data. Metal-backed patellar component failure is a new complication of total knee arthroplasty and will be seen in increasing numbers. Caution is urged in implanting metal-backed designs until further design research is done.

Aged↗
PubMed1988

Revision total knee arthroplasty.

Revision total knee arthroplasty can be very successful if careful preoperative planning has been carried out and the surgeon is equipped to handle potential problems encountered with restoration of static alignment, stability, and deficient bone stock. Special femoral and tibial component extractors are indispensable tools. A high-speed burr is helpful. Posterior cruciate ligament-preserving prostheses often can be used, but prostheses with extra degrees of constraint must be available. Long-stemmed components for both the femoral and tibial sides should be available. Access to a bone bank to obtain allogeneic bone for grafting is essential. The surgeon must be familiar with techniques other than bone grafting for restoration of deficient stock, such as the use of bone screws and cement, custom-augmented components, and metal wedge spacers.

Arthroplasty↗
PubMed1988

The patellofemoral component of total knee arthroplasty.

Patellofemoral complications continue to form a large proportion (up to 50%) of total knee arthroplasty (TKA) complications. If adequate attention is paid intraoperatively to patellar tracking and component position, the incidence of subluxation, component loosening, and fracture should decrease. When treating patellar subluxation and dislocation, tibial tubercle transfer should be avoided because there is an unacceptably high incidence of complications. Care should be taken to treat the underlying cause of dislocation with either a soft tissue procedure or component revision. Fracture of the patella may be treated nonoperatively in 50% and 80% of patients. Cysts, if large, may be bone-grafted to avoid the potential complications of stress fracture and component loosening. Loosening of the patellar component is likely to be symptomatic and to require surgery in up to 75% of cases. A displaced patellar component may cause attritional wear of the quadriceps tendon or patellar ligament. All rheumatoid patellae should be resurfaced. The present trend in the osteoarthritic patella is toward resurfacing more often. With improved implant design and a predicted decrease in complications, resurfacing in the osteoarthritic patella may become routine. Osteoarthritic patellae that maintain good cartilage, normal anatomic shape, and congruent tracking need not be resurfaced.

Adult↗
PubMed1988

Failure of the metal-backed patellar component after total knee replacement.

Twenty-five patients had failure of a metal-backed patellar component after total knee replacement. Five manufacturers and seven designs were involved. There was no apparent correlation between failure of the component and the age or sex of the patient, the diagnosis, the use of cement, the femorotibial alignment, or the use of lateral release. The patients in whom the patellar implant failed were relatively heavy, and the diagnosis in most of them was osteoarthritis. The failure was due to one of two mechanisms: wear or fracture, or both, of the polyethylene over the edge of the metal backing (eighteen components), or dissociation of the polyethylene or the base-plate, or both, from the anchoring pegs (seven components). In many of the patients, failure of the component was not suspected before arthrotomy. The failure led to considerable wear of the femoral component in eleven patients and to metal-induced synovitis in twenty-three. We concluded that metal backing may predispose the patellar component to a small but important likelihood of failure, and we urge caution in choosing a metal-backed patellar implant. Additional research is necessary to improve designs for the patellar component, especially if metal backing is to be used.

Aged↗
PubMed1987

Function of pyridoxal 5'-phosphate in glycogen phosphorylase: a model study using 6-fluoro-5'-deoxypyridoxal- and 5'-deoxypyridoxal-reconstituted enzymes.

A new vitamin B6 analogue, 6-fluoro-5'-deoxypyridoxal (6-FDPL), was synthesized and characterized. This analogue, as well as 6-fluoropyridoxal (6-FPAL), 6-fluoropyridoxal phosphate (6-FPLP), and 6-fluoropyridoxine, showed positive heteronuclear 1H-19F nuclear Overhauser effects between the 5'-protons and the 6-fluorine. Apophosphorylase reconstituted with 6-FDPL showed 1% of the activity of the native enzyme in the presence of phosphite. The kinetic pattern, apparent pH optimum of activity, and the activity-temperature dependency of the 6-FDPL-enzyme were virtually identical with those of phosphorylase reconstituted with the parent compound, 6-FPAL [Chang, Y. C., & Graves, D. J. (1985) J. Biol. Chem. 260, 2709-2714], except the Km of phosphite toward the 6-FDPL-enzyme was 9 times higher than that with the 6-FPAL-enzyme and the 6-FDPL-enzyme showed a lower Vmax value. Phosphorylase reconstituted with 5'-deoxypyridoxal (DPL) also showed activity in the presence of phosphite. The kinetics and the temperature-activity dependency of this reconstituted enzyme were investigated. 19F nuclear magnetic resonance studies showed that the binding of glucose 1-phosphate to a 6-FDPL-enzyme-adenosine 5'-phosphate (AMP) complex shifted the 19F signal 0.6 ppm upfield, whereas a 2.1 ppm change was observed when the 6-FPAL-enzyme-AMP formed a complex with glucose 1-phosphate [Chang, Y. C., Scott, R. D., & Graves, D. J. (1986) Biochemistry 25, 1932-1939].(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Use of TARA hemiarthroplasty in advanced osteonecrosis.

The results of 25 TARA hemiarthroplasty procedures performed on 21 patients with radiographically documented Ficat stages III and IV osteonecrosis are reported. The average patient age at the time of surgery was 37.6 years (range, 22-55 years). The average length of follow-up study was 37 months (range, 25-60 months). Preoperative Harris hip scores averaged 51 points (range, 22-69 points). Postoperative scores averaged 90 points (range, 66-100 points). Good or excellent results were obtained in 22 of 25 hips. There were no cases of infection or component dislocation. Three component revisions were performed in two patients. Four patients required removal of trochanteric wires and one patient had excision of heterotopic ossification. This procedure appears to offer selected young patients with advanced femoral head osteonecrosis a very satisfactory initial result, while preserving many options for subsequent revision procedures.

Adult↗
PubMed1987

Long-term results of total joint arthroplasty in nonambulatory patients.

The authors conducted a long-term follow-up study of 27 patients, all confined to a bed or wheelchair for at least 6 months, who had total joint arthroplasty to relieve rest pain, correct deformity, and enable independent ambulation. The average duration of nonambulatory status before operation was 3 years (mean, 1 1/2 years), with the longest being 15 years. The patients required an average 3-month hospital stay and an average of three major total joint arthroplasties in the lower extremities. All of the patients were ambulatory at the time of discharge but required some sort of aid. After 1 year, 20 patients (74%) were able to launch independently; 9 (33%) could ambulate without aids; and 14 (52%) could ambulate with aids. At follow-up evaluation 3-12.8 years (average, 6.5 years) after operation, nine patients (33%) ambulated without aids, five (19%) required a single crutch or cane, and nine (33%) required bilateral crutches or a walker, for a total success rate of 85%, which did not deteriorate with time.

Adolescent↗
PubMed1987

Renal clearance of glutathione measured in rats pretreated with inhibitors of glutathione metabolism.

Renal clearance measurements were performed in rats pretreated with various inhibitors of glutathione metabolism. Approximately 97% of the renal gamma-glutamyltranspeptidase was inactivated by infusion of AT-125. Within 4.5 h arterial plasma concentration and urinary excretion of glutathione increased from 4 microM and 1.2 nmol/h to 27 microM and 3,900 nmol/h, respectively. The ratio of excreted to filtered glutathione increased from less than 0.01 to 1. When renal glutathione was decreased to 35% of normal by pretreating rats with D,L-buthionine-S,R-sulfoximine, the subsequent inactivation of the transpeptidase caused only a two-fold increase in arterial plasma glutathione, and urinary excretion increased to only 70% of the filtered load. The filtered load of glutathione was reduced by intravenous infusion of purified gamma-glutamyltranspeptidase. At 1 to 3 h after infusion, arterial glutathione decreased to 0.3 microM. Under these conditions, the amount of glutathione excreted by an AT-125-treated rat was 40-fold greater than the filtered load. When similar experiments were carried out in rats that were pretreated with D,L-buthionine-S,R-sulfoximine and AT-125, urinary excretion of glutathione was decreased 10-fold, but it still exceeded the amount filtered. These results firmly establish that apical secretion contributes to the glutathione catabolized in the tubular lumen.

Animals↗