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Biomedical subjects

F R Noyes

Publications and source records attributed to F R Noyes.

At least 91 records · Page 5Linked to original sources
PubMed1981

Effect of radiation sterilization and aging on ultrahigh molecular weight polyethylene.

The mechanical properties of polyethylene components used in prosthesis are altered after fabrication by the sterilization procedure and by the environmental and mechanical aging which occurs after implantation. To assess the importance and extent of these alterations, ultrahigh molecular weight polyethylenes from two sources, Hercules 1900 and RCH 1000C, were subjected to gamma-ray irradiation and aging in serum and argon environments. Changes induced by these treatments in the structural and mechanical parameters have been determined by a variety of experimental techniques. The effect of irradiation is to introduce crosslinks and to increase the degree of crystallinity resulting in changes in the tensile properties in the direction of higher stiffness and reduced ductility. Aging for six months produced similar changes with subtle differences. The results suggest that the initially low degree of crystallinity which results from the sluggish mobility of the very long chain molecules offers the opportunity for significant changes in the properties during use in the long run.

Crystallization↗
PubMed1980

Knee ligament tests: what do they really mean?

In summary, newer biomechanical concepts clarify human function, the clinical laxity tests, and functional stability of the joint. Biomechanical studies show that one or two ligaments provide the primary passive restraint for each plane of knee stability, with the remaining ligaments having a secondary, helping role. Correct interpretation of clinical laxity tests and surgical treatment of instability require understanding of this differentiation. Knowledge of the interaction between the primary and secondary restraints during the clinical laxity tests allows for more accurate interpretation of the extent of ligament injury. Weak secondary restraints may initially allow little laxity to be demonstrated in the clinical laxity tests. However, the secondary restraints will eventually stretch out and cause a greater laxity. In an acute knee injury, "a little laxity is a lot" and should be considered as serious. In knee injuries, an exact diagnosis of injury is required. This often requires examination under anesthesia and arthroscopy to define the extent of ligament damage. Functional stability of the knee is a primary treatment goal after ligament injury but the stability may be short term if it relies on muscle control alone without the finetuning action of the ligamentous system. Abnormal laxity on clinical examination means increased risk for joint wear, cartilage deterioration, and arthritis on a long-term basis. Close follow-up after ligament injuries, adequate rehabilitation, and correct advice on allowable activities are important treatment concepts after any serious ligament injury.

Biomechanical Phenomena↗
PubMed1980

Knee sprains and acute knee hemarthrosis: misdiagnosis of anterior cruciate ligament tears.

A retrospective study and a prospective study comprising 186 patients with "typical knee sprains" were conducted at the University of Cincinnati Sports Medicine Institute. We concluded that the commonly encountered mild knee sprain may actually be a serious knee injury whose severity is easy to underestimate. Traumatic hemarthrosis indicates a serious knee injury. Arthroscopy showed that a surprising 72 percent of the patients in the prospective study had disruption of the anterior cruciate ligament (partial tear in 28%, complete tear in 44%). In addition of the 72 percent of anterior cruciate ligament tears, associated injuries included meniscus tears (62%), osteochondral fractures or fissures to the joint surface (20%), and other significant ligament disruptions (20%). Any joint effusion within 24 hours of knee injury, no matter how trivial, suggests a need for further diagnostic tests beyond the initial examination. In our study, our clinical examination alone consistently underestimated the extent of injury, resulting in inadequate information for treatment descisions. Conversely, arthroscopy and examination under anesthesia provided information on the extent of injury, allowing an accurate diagnosis and formulation of a rational treatment program.

Adolescent↗
PubMed1980

Patellar malalignment: a treatment rationale.

A general review of present-day treatment for patellofermoral malalignment is presented. These regimens are viewed in light of known anatomical, biomechanical, and pathophysiological principles. We stress the need for a sound knowledge of biomechanical and pathophysiological principles prior to the initiation of surgical or rehabilitative techniques. Three major categories of surgery are discussed: 1) simple lateral release, 2) proximal "dynamic" realignment, and 3) distal patellar tendon realignment. A comprehensive rehabilitation program is presented based on sound biomechanical principles and known surgical techniques. We wish to stress the "non-surgical," conservative approach to patellofemoral malalignment through the use of a well-orgainzed and structured rehabilitation program.

Biomechanical Phenomena↗
PubMed1980

Arthroscopy in acute traumatic hemarthrosis of the knee. Incidence of anterior cruciate tears and other injuries.

In a prospective study, all injured knees that had traumatic hemarthrosis and absent or negligible instability on clinical examination underwent arthroscopy and examination under anesthesia. Eighty-five knees (eighty-three patients) were examined over a 125-week period. Some degree of disruption of the anterior cruciate ligament was found in sixty-one (72 per cent) of the knees (a partial tear in 28 per cent and a complete tear in 44 per cent), frequently associated with an injury of varying severity to other joint structures. These included minor ligament sprains without laxity in 41 per cent, a major associated ligament injury in 21 per cent, meniscal tears in 62 per cent (partial in 30 per cent and complete in 70 per cent), and a femoral chondral fracture or surface defect in 20 per cent. A popping sensation at injury occurred in 33 per cent of knees with a normal anterior cruciate ligament and in 36 per cent of those with a disruption. One-third of the knees had no to slight pain at the time of injury. The anterior drawer test without anesthesia was positive in only 24 per cent of the knees with a torn anterior cruciate ligament. We concluded that: (1) a traumatic hemarthrosis indicates a significant knee injury; (2) examination under anesthesia plus arthroscopy allows a more accurate diagnosis of injury to joint structures; and (3) such data are required for a rational treatment program to be outlined.

Adolescent↗
PubMed1979

Osseous deformity from osteomyelitis variolosa. A case report.

Smallpox osteomyelitis (osteomyelitis variolosa) with gross clinical and radiologic deformities of the elbows, hands and feet occurred in a 53-year-old Vietnamese refugee. This disease, once common in Asia and Africa, may cause permanent damage to joints and growth centers in the course of the acute infection in childhood. The roentgenographic features are sufficiently diagnostic to exclude congenital dysplasia of the skeletal system, leprosy, or sequelae of thermal injury, and other joint disorders.

Elbow Joint↗
PubMed1976

The strength of the anterior cruciate ligament in humans and Rhesus monkeys.

The mechanical properties of anterior cruciate bone-ligament-bone specimens from humans and rhesus monkeys were determined in tension to failure under high strain-rate conditions. The age range of the human specimens was from sixteen to eighty-six years. The values fro human specimens obtained from young adults with regard to elastic modulus, ultimate tensile stress, and strain energy to failure were approximately two to three times those for specimens from humans in the sixth decade and older. The major mode of failure was ligament disruption in the specimens from young adult humans and avulsion of bone beneath the ligament insertion site in the specimens from older humans. The difference in mode of failure correlated with histological observations of decreased bone mass at the site of ligament attachment in the specimens from older humans. Rhesus monkey specimens had higher values for elastic modulus, failure stress, and strain energy. Significant reductions in strength and stiffness properties of ligament units were shown to occur with advancing age to a greater degree than expected. All experiments in which specimens from older human cadavera are used should be interpreted with caution when the results are applied to mechanisms of ligament failure for younger or athletic individuals.

Adolescent↗
PubMed1976

Cruciate ligament prosthesis: strength, creep, and fatigue properties.

The mechanical properties of the Richards polyethylene ligament implant were studied and compared with the strength of human cruciate ligament preparations. The implant yields and plastically deforms at a force of 420 newtons (ninety-four pounds) and approximately 10 per cent elongation when tested at a strain rate of 100 per second. This is one-fourth the average tensile strength of the human anterior curciate ligament preparations. When tested at a strain rate of 1 per cent per second the implant's yield-point force was lowered by 15 per cent. The implant exhibits considerable viscoelastic behavior and will progressively elongate under repetitive loads when insufficient time is allowed for it to return to its original length. In bending, the implant did not fail after eighty million stress reversals (forty million revolutions) when tested while immersed in saline solution at body temperature. The tests indicate that the tensile strength of the implant is low in comparison with both the strength of human preparations and estimates of actual in vivo functional loads. We conclude that caution is required in the use of this implant.

Age Factors↗
PubMed1975

The influence of compositional variations on bone ingrowth of implanted porous calcium aluminate ceramics.

Sixteen ceramic specimens were implanted in the femur of mature rhesus monkeys. The specimens consisted of four groups of a basic calcium aluminate composition with additions of 5, 10, 15 and 20 wt% phosphorous pentoxide (P2O5). The increasing amounts of P2O5 caused variations in the resorption rate, microstructure and surface characteristics of the implant. The influence of these variables on bone and tissue growth within and about the implant was investigated. After sacrifice the ceramic-bone specimens were studied by a tetracycline-based histological analysis, scanning electron microscopy and energy dispersive analysis. The results indicate an increase in mesenchymal cell proliferation, fibrous and bone tissue formation at the ceramic tissue interface and within the implant with increasing concentrations of P2O5. The results obtained from the study did not furnish sufficient evidence to differentiate between the direct chemical influence the increasing P2O5 had on osseous tissue formation or the indirect influence that may have resulted from its effect on the ceramic microstructure and morphology.

Aluminum↗