Diagnosis of emphysema.

Thirty-seven patients with chronic obstructive lung disease (COLD) were divided into three groups on the basis of radiologic evidence of emphysema. The category of radiologic emphysema correlated with severity of abnormality of routine lung function, gas exchange and lung mechanics. Within the group of patients with no radiologic abnormally, a subgroup with severe functional abnormalities, quite similar to those found in patients with widespread radiologic emphysema, could be selected on the basis of maximum elastic recoil less than 10 cm H2O.

Chronic obstructive pulmonary disease following idiopathic pulmonary fibrosis.

The rapid development of irreversible airflow obstruction in two nonsmoking women who recovered from acute idiopathic pulmonary fibrosis is discussed. Pulmonary fibrosis was diagnosed clinically and by lung biopsy. Recovery both clinically and radiologically was complete. Several pulmonary function studies in both patients showed a typical restrictive pattern (reduced lung volumes and carbon dioxide diffusing capacity, normal FEV1/FVC ratio). Within one year both patients exhibited an obstructive pattern of dysfunction (hyperinflation, gas trapping, reduced airflow measurements). These patients illustrated irreversible airway obstruction following recovery from the restrictive stage of pulmonary fibrosis.

Patellar tracking measurement in the normal knee.

Eleven fresh frozen cadaveric knee specimens were mounted in a knee kinematics test device, and normal patellar movements were evaluated with use of an external device for direct measurement of patellar movements. The effects of four different measurement conditions were assessed through alteration of one condition and determination of its effect on patellar kinematics with the use of six specimens. The four conditions included (a) change of the measuring axis from an axis parallel to the central axis of the femur (femoral axis) to one parallel to the central axis of the tibia (tibial axis), (b) rotation of the femoral axis internally 6 degrees, (c) change of the direction of the quadriceps force from parallel to the mechanical line of the lower extremity to a direction parallel to the femoral shaft, and (d) increase of the magnitude of the quadriceps force from 111 to 500 N. During knee flexion, the patella shifted laterally after a slight initial medial shift, tilted laterally from midflexion to 90 degrees, and gradually rotated medially. The patellar shift relative to the tibial axis appeared to be more medial than the shift measured relative to the femoral axis; the discrepancy was caused by the valgus position of the tibia relative to the femur. Changing the rotational angle of the femoral axis artificially changed the patellar position. Varying the direction of the quadriceps within the narrow range and increasing the quadriceps force did not affect patellar movements.(ABSTRACT TRUNCATED AT 250 WORDS)

Femoral rotational alignment, based on the anteroposterior axis, in total knee arthroplasty in a valgus knee. A technical note.

The landmarks used to achieve correct rotational alignment of the femoral component in total knee arthroplasty may be indistinguishable or unreliable in the distal architecture of a valgus knee. Five observers identified the anteroposterior axis, the posterior condylar axis, and the transepicondylar axis in thirty cadaveric femora to determine the reliability of the use of each axis in the operative setting. In addition, radiographs were made of the distal aspect of each femur, the axes were constructed, and the angles were measured and compared with the visual measurements made by the observers. A line drawn perpendicular to the anteroposterior axis consistently approximated 4 degrees of external rotation relative to the posterior condylar surfaces. The transepicondylar axis was more difficult to define and was not as accurate. The radiographic results were similar to the visual results, but the standard deviations for the former were less than those for the latter. The anteroposterior axis appears to be a reliable landmark for rotational alignment of the femoral component in a valgus knee.

Effect of neck resection on torsional stability of cementless total hip replacement.

Loosening of the femoral component in total hip arthroplasty commonly results from inadequate resistance to torsional loads. We evaluated 20 adult human cadaver femora to determine the effect of different neck-resection levels on torsional resistance of the femoral component. All specimens were prepared for fixation with the Impact modular total hip replacement. Each femoral diaphysis was overreamed 2 mm to achieve only proximal fixation. The specimens were then divided into groups of five and implants were inserted with the precision press-fit technique. Each specimen was loaded in an Instron stress-testing device. A linearly variable differential transducer was then attached to the specimen to measure micromotion at the medial interface between the implant and bone. Each specimen was loaded until failure occurred. When all of the neck was preserved, torsional load to failure was significantly better than in the 50%, 15%, and 0% neck-preservation specimens. At a 20 N-m torsional load, the 100% and 50% neck preservation specimens had similar micromotion, but the 15% and 0% specimens had gross motion and a large standard deviation at this load level. Without distal fixation, the femoral component is highly dependent on proximal geometry for resistance to torsional loading. Preserving the femoral neck provides an effective means of resistance. Maintaining the entire femoral neck most effectively reduces miromotion at low loads, but maintaining the midshaft area of the femoral neck appears to most effectively control micromotion at higher torsional loads. Resection below the midshaft of the neck markedly decreases the torsional load-bearing capacity of the proximal femur.

Rotational stability of noncemented total hip femoral components.

Achieving torsional fixation of the femoral component in total hip arthroplasty is an important factor in success of the implant, so design features that improve fixation are likely to improve clinical results. Four femoral stem designs that allow different levels of femoral neck resection and use different distal fixation techniques were mechanically tested in cadaveric femurs to determine resistance to torsional loads. Five specimens for each stem design were implanted according to the standard procedure, and each was axially and torsionally loaded in a servohydraulic testing machine. Rotational interface micromotion and interface slippage were measured at the bone-implant interface. Decreased micromotion and interface slippage were associated with a distal scratch fit and neck retaining design, and the combination of distal scratch fit and neck retention had the least micromotion and smallest standard deviation of the four designs.

Postural relief of dyspnoea in severe chronic airflow limitation: relationship to respiratory muscle strength.

Maximal static inspiratory and expiratory pressures (Pimax and Pemax) were measured in six different positions in 40 patients with advanced chronic airflow limitation and in 140 normal subjects to determine whether posture influences respiratory muscle strength. Patients with chronic airflow limitation were studied on days 1 and 5 of an acute exacerbation. There was no postural effect on maximal static pressures in the normal subjects. We divided our patients with chronic airflow limitation into "moderate" and "severe" groups on the basis of a Pimax in the standing position greater or less than 35 cm H2O. The seated leaning-forward position was the preferred posture in 22 of the 23 "severe" patients and 13 of the 17 "moderate" patients. Pimax was greater in the seated leaning-forward position than in the other positions studied (p less than 0.001) on days 1 and 5 in the "severe" patients and (p less than 0.05) on day 5 in the "moderate" patients. Posture had no influence on Pemax in patients with chronic airflow limitation. There was a significant improvement in both Pimax (p less than 0.01 for the "severe" group and p less than 0.05 for the "moderate" group) and Pemax (p less than 0.01 for both groups) between days 1 and 5. The seated leaning-forward position was the optimum posture for the patients to generate maximum inspiratory pressures and to obtain greatest subjective relief of dyspnoea.

Fixation of the Quatroloc femoral component: a biomechanical and clinical study.

The current study was designed to test the hypothesis that press-fit femoral components with proximal press-fit and distal mechanical interlock can achieve fixation sufficient to allow bone ingrowth in osteoporotic and in normal bone. The addition of steps along the tapered distal stem improved fixation in osteoporotic bone enough to reduce micromotion to less than 20 microm in response to physiologic axial and torsional load. The clinical portion of the study included 226 consecutive hips (223 patients) with 2- to 4-year clinical results after total hip arthroplasty with a rectangular femoral component using proximal porous coating and distal mechanical interlock. Patient age ranged from 36 to 92 years. At 2 years postoperative, 4% of the patients with Type A (normal) femoral bone, 3% with Type B (intermediate) bone, and no patients with Type C (osteoporotic) bone had thigh pain. No clinical cases of loosening have occurred in normal or osteoporotic femurs.

Laboratory evaluation of alignment and kinematics in a unicompartmental knee arthroplasty inserted with intramedullary instrumentation.

The purposes of this study were to evaluate the reliability of intramedullary (IM) instrumentation for unicompartmental total knee replacement and to assess the stability characteristics of the knee after implantation of a relatively unconstrained articular surface. Five adult, human cadaver lower extremities including hip, knee, and ankle were used to evaluate IM alignment. Five adult, fresh-frozen knee specimens were used to evaluate knee kinematics. Long anterioposterior roentgenograms were used to evaluate valgus angle and position of the center of the knee relative to the mechanical axis of the lower extremity. IM instrumentation returned the knee to normal alignment in all cases. The greatest valgus angle change was 3 degrees, and the position of the center of the knee relative to the mechanical axis was not significantly altered. Knee kinematics after unicompartmental knee replacement followed the predicted pattern of normal stability in extension and had slightly less varus-valgus laxity at 30 degrees (p less than 0.01), 45 degrees (p less than 0.01), and 60 degrees (p less than 0.05), and less anteroposterior displacement at 45 degrees (p less than 0.01) and 60 degrees (p less than 0.05). This study offers encouraging evidence that unicompartmental knee replacement with unconstrained components can restore normal knee kinematics, and that alignment can be restored with a high degree of accuracy with an intramedullary alignment system.

Lung elastic recoil and reduced airflow in clinically stable asthma.

Lung volumes, maximum expiratory flow rates, and static volume-ressure curves were measured in 16 patients with clinically stable asthma. It was found that flow rates were reduced in such patients because of the combined effects of reduced elastic recoil (transpulmonary pressure) and intrinsic diseases of the airways. In nine patients treated with an aerosol of isoprenaline, flow rates improved as a result of reduction in airways resistance as the static recoil pressure of the lungs fell further in those patients. The possibility is suggested that muscle tone in peripheral airways or alveolar ducts contributed to the elastic recoil measurements.

Hypomagnesemia and respiratory muscle power.

Although hypomagnesemia is common and causes weakness in humans, it is not known what effect its correction has on respiratory muscle power. We designed an experiment to test the hypothesis that correction of hypomagnesemia will improve respiratory muscle power. We measured muscle power and lung volumes in 16 control subjects and 17 patients (11 alcoholics, 6 nonalcoholics) on 3 consecutive days. After baseline measurements on Day 1, patients were randomized and the study was double blinded. Patients were given magnesium intravenously or dextrose as placebo. Measurements were repeated on Day 2, and the patients were then given magnesium if they had previously been given placebo, and vice versa. Measurements were done again on Day 3. There was no significant difference in lung volumes in patients or control subjects over the 3 days. There were no changes in respiratory muscle power in control subjects, but there was an improvement in all parameters of muscle power measured after magnesium therapy in patients. Hypomagnesemia should be excluded as a cause of muscle weakness because its replacement may improve muscle power.

Effect of modification of the smoking habit on lung function.

The effect of smoking cessation or modification on lung function was determined during a 48-week period. In a large number of the cigarette smokers, a disturbance of lung function was not revealed by conventional tests, such as the 1-sec forced expiratory volume; however, an abnormality was often demonstrable in tests that may reflect alterations in small airways, such as closing volume and Phase III of the single-breath expired N2 curve. There was no relation between the degree of abnormality of lung function and the presence of respiratory symptoms, but there appeared to be a relationship to lifetime smoking history, the heaviest smokers having the poorest function. Cessation, or more than 25 per cent decrease in the number of cigarettes smoked, was attened by improvement in the slope of Phase III of the N2 washout curve, closing volume, and closing capacity, as well as forced vital capacity, 1-sec forced expiratory volume, and peak flow. Resumption of smoking after cessation was attended by a deterioration in the slope of Phase III and closing capacity. The data suggest that the functional abnormalities in smokers are related to smoking and are at least partially reversible by cessation or significant modification of the smoking habit.

Intraindividual variability in maximal expiratory flow-volume and closing volume in asymptomatic subjects.

The variability of the parameters derived from analysis of the forced vital capacity and the expired nitrogen trace after a vital capacity inhalation of oxygen (closing volume) within a day, from day to day, and from week to week, has been determined. Effort-dependent tests as vital capacity and peak expiratory flow showed the least variability. The greatest variability was seen in effort-independent tests of function such as the maximal expiratory flow rate at 25 per cent (75 per cent of expired vital capacity) and 50 per cent of vital capacity, as well as closing volume. The degree of variability in the tests used was uninfluenced by the periodicity of the tests or the age or smoking habits of the subjects tested. It is suggested that variability of tests of respiratory function should be taken into account in their interpretation.

The effect of acute, intensive cigarette smoking on maximal expiratory flows and the single-breath nitrogen washout trace.

The effect of acute, intensive cigarette smoking on forced vital capacity and the single-breath expired N2 trace was studied in 82 smokers. There were significant decreases in the "effort-dependent" tests, such as peak flow and 1-sec forced expiratory volume, but no change in the more "effort-independent" tests, such as maximal mid-expiratory flow and maximal expiratory flow at 25 per cent of the vital capacity. Closing volume was unchanged in absolute terms and as a percentage of vital capacity. Closing capacity was unchanged in absolute terms and as a percentage of total lung capacity, but there was a significant increase in the slope of Phase III of the N2 washout curve after the acute smoking session. The tests of function that changed significantly after acute, intensive smoking were the ones that improved in 52 subjects who modified their smoking habits. The data suggest that acute, intensive cigarette smoking may be associated with an increase in resistance to air flow in the larger airways or a reduction in effort, and with increased nonuniformity of intraregional distribution of ventilation.

Computer analysis of the single-breath nitrogen washout curve.

A computerized system has been developed to analyze the parameters that can be derived from the nitrogen washout curve. Analog signals for air flow, volume, and nitrogen concentration are entered either on-line or off-line into a 24,000 mini-computer. The program calculates vital capacity, total lung capacity, and residual volume, as well as the slope of phase III, closing volume in liters, total lung capacity, residual volume, closing capacity, closing volume/vital capacity ratio, and closing capacity/total lung capacity ratio. Validation tests showed excellent correlation between hand- and computer-calculated values of closing volume(r=0.864), vital capacity (r=0.997), total lung capacity (r=0.991), and slope of phase III (R=0.926). We concluded that the computerized system for analysis of the expired nitrogen washout curve is as reliable as hand calculations and is immeasurably faster.