Validation of a measuring technique with computed tomography for cement penetration into trabecular bone underneath the tibial tray in total knee arthroplasty on a cadaver model.

BACKGROUND: In total knee arthroplasty (TKA), cement penetration between 3 and 5 mm beneath the tibial tray is required to prevent loosening of the tibia component. The objective of this study was to develop and validate a reliable in vivo measuring technique using CT imaging to assess cement distribution and penetration depth in the total area underneath a tibia prosthesis. METHODS: We defined the radiodensity ranges for trabecular tibia bone, polymethylmethacrylate (PMMA) cement and cement-penetrated trabecular bone and measured the percentages of cement penetration at various depths after cementing two tibia prostheses onto redundant femoral heads. One prosthesis was subsequently removed to examine the influence of the metal tibia prostheses on the quality of the CT images. The percentages of cement penetration in the CT slices were compared with percentages measured with photographs of the corresponding transversal slices. RESULTS: Trabecular bone and cement-penetrated trabecular bone had no overlap in quantitative scale of radio-density. There was no significant difference in mean HU values when measuring with or without the tibia prosthesis. The percentages of measured cement-penetrated trabecular bone in the CT slices of the specimen were within the range of percentages that could be expected based on the measurements with the photographs (p = 0.04). CONCLUSIONS: CT scan images provide valid results in measuring the penetration and distribution of cement into trabecular bone underneath the tibia component of a TKA. Since the proposed method does not turn metal elements into artefacts, it enables clinicians to assess the width and density of the cement mantle in vivo and to compare the results of different cementing methods in TKA.

Grasping Weber's illusion: The effect of receptor density differences on grasping and matching.

Weber found that distances between tactile stimuli on a high-receptor-density area are perceived as being larger than identical distances on a low-receptor-density area (Weber's illusion). Previous studies of visual illusions suggest that illusion effects vary with the type of response given. Here we tested a modified version of Weber's illusion in which a solid object was placed on the forearm or hand. Blindfolded participants were required either to give a size estimation or to grasp the object. The results showed that size estimation of solid objects was consistent with Weber's illusion, whereas grasping responses showed an opposite pattern (e.g., larger hand opening for objects on the forearm). A second experiment showed that this pattern is not due to biomechanical differences induced by the difference in spatial position of the target objects on the hand and arm. We suggest that the larger grip aperture when grasping objects on the arm were due to an increase in safety margin as a response to greater uncertainty about the object dimensions due to reduced receptor density.

Grasping Weber's illusion: the effect of receptor density differences on grasping and matching.

Weber found that distances between tactile stimuli on a high-receptor-density area are perceived as being larger than identical distances on a low-receptor-density area (Weber's illusion). Previous studies of visual illusions suggest that illusion effects vary with the type of response given. Here we tested a modified version of Weber's illusion in which a solid object was placed on the forearm or hand. Blindfolded participants were required either to give a size estimation or to grasp the object. The results showed that size estimation of solid objects was consistent with Weber's illusion, whereas grasping responses showed an opposite pattern (e.g., larger hand opening for objects on the forearm). A second experiment showed that this pattern is not due to biomechanical differences induced by the difference in spatial position of the target objects on the hand and arm. We suggest that the larger grip aperture when grasping objects on the arm were due to an increase in safety margin as a response to greater uncertainty about the object dimensions due to reduced receptor density.

The effects of a weight belt on trunk and leg muscle activity and joint kinematics during the squat exercise.

Fourteen healthy men participated in a study designed to examine the effects of weight-belt use on trunk- and leg-muscle myoelectric activity (EMG) and joint kinematics during the squat exercise. Each subject performed the parallel back squat exercise at a self-selected speed according to his own technique with 90% of his IRM both without a weight belt (NWB) and with a weight belt (WB). Myoelectric activity of the right vastus lateralis, biceps femoris, adductor magnus, gluteus maximus, and erector spinae was recorded using surface electrodes. Subjects were videotaped from a sagittal plane view while standing on a force plate. WB trials were completed significantly faster (p < 0.05) than NWB trials over the entire movement and in both the downward phase (DP) and upward phase (UP). No significant differences in EMG were detected between conditions for any of the muscle groups or for any joint angular kinematic variables during either phase of the lift. The total distance traveled by the barbell both anteriorly and vertically was significantly greater (p < 0.01) in the WB condition than the NWB condition. The velocity of the barbell was significantly greater (p < 0.01) both vertically and horizontally during both the DP and UP in the WB condition as compared with the NWB condition. These data suggest that the use of a weight belt during the squat exercise may affect the path of the barbell and speed of the lift without altering myoelectric activity. This suggests that the use of a weight belt may improve a lifter's explosive power by increasing the speed of the movement without compromising the joint range of motion or overall lifting technique.

Exposure-response of asphalt fumes with changes in pulmonary function and symptoms.

OBJECTIVES: This study examines possible associations between asphalt fumes and workshift changes in lung function and symptoms among 170 workers exposed to asphalt fumes. METHODS: The workers were from 5 segments of the asphalt industry, and most of them participated for 2 consecutive workdays. The primary response variables were changes in lung function (measured at the beginning and end of the shift) and incidence of symptoms (measured before, 3 times during, and at the end of the shift). Exposure was estimated from breathing-zone samples of total particulate (TP), respirable particulate (RP), the benzene-soluble fraction of the TP (BSF), volatile hydrocarbons collected on a charcoal tube (VHC), nitrogen dioxide, sulfur dioxide, formaldehyde, carbon monoxide, and hydrogen sulfide. Ozone and wet bulb/dry bulb temperature, as a measure of heat stress, were measured as area samples. In addition, daily cigarette smoking was determined by questionnaire. The exposure-response associations were assessed by both parametric and nonparametric statistical techniques. RESULTS: Overall, no consistent association was observed between an acute reduction in lung function or the incidence of symptoms and exposure to asphalt fumes. Concentrations in the neighborhood of the maximum levels constitute no-observed adverse effect levels: TP (<1.5 mg/m3 to maximum 6.2 mg/m3), RP (<0.6 mg/m3 to maximum 1.4 mg/m3), BSF (<0.6 mg/m3 to maximum 1.3 mg/m3), VHC (<8 mg/m3 to maximum 19.8 mg/m3). There were no exposure-response trends with ozone, heat stress, cigarettes smoked, or length of workday.

Creatine supplementation differentially affects maximal isometric strength and time to fatigue in large and small muscle groups.

Ten physically active, untrained, college-aged males (26.4 +/- 5. 8 years old) received creatine (CR, 5 g creatine monohydrate + 3 g dextrose) and placebo (PLA, 7 g dextrose) supplementation four times per day for 5 days in a double-blind, randomized, balanced, crossover design. Performance was assessed during maximal and three repeated submaximal bouts of isometric knee extension and handgrip exercise. CR supplementation significantly increased (p <.05) maximal isometric strength during knee extension but not during handgrip exercise. CR supplementation increased time to fatigue during each of the three bouts of submaximal knee extension and handgrip exercise when compared to the PLA trials. These findings suggest that CR supplementation can increase maximal strength and time to fatigue during isometric exercise. However, the improvements in maximal isometric strength following CR supplementation appear to be restricted to movements performed with a large muscle mass.

Effects of stairclimbing on VO2max and quadriceps strength in middle-aged females.

The purpose of this study was to determine the effect of 12 wk of stairclimbing with and without an external load on aerobic capacity and quadriceps strength of sedentary (initial VO2max 25.3 +/- 0.73 ml.kg-1.min-1) (mean +/- SEM) middle aged females (50-65 yr). Three groups, LOAD (stairclimbing with external load, N = 8), STAIR (no load, N = 9), and CONTROL (N = 7) were tested. By week 4, subjects warmed up 5 min on a cycle ergometer followed by 35 min on the stairclimber at 80-85% maximum heart rate (MHR) 4 d.wk-1. In week 6, the LOAD group carried an external load of 4% of body weight increasing to 8% for weeks 7-12. STAIR and LOAD group significantly increased (P < 0.01) VO2max by 11.1% and 9.6%, respectively. Isokinetic strength tests showed increased (P < 0.05) peak torque and total work for STAIR and LOAD at 120 and 180 degrees.s-1. For total work, a significant increase (P < 0.05) of 10.5% was observed at 60 degrees.s-1 for the LOAD group. The results indicate stairclimbing is an appropriate exercise for middle-aged females improving both aerobic capacity and strength following 12 wk of training.

Effect of run vs combined cycle/run training on VO2max and running performance.

The effects of 5 wk of equivalent intensity, 85-90% maximum heart rate (MHR), run-only (N = 6) vs cycle/run (N = 5) training were evaluated in moderately fit runners, mean VO2max of 55.2 ml.kg-1.min-1, 19-35 yr old, on maximal treadmill (TM) and cycle ergometer (CE) testing, 5000-m and 1609-m run performances, and submaximal measures while treadmill running. Subjects participated in either 4 d.wk-1 of run-only or alternating run and cycle training. Both groups significantly improved TM VO2max (P < 0.05), CE VO2peak (P < 0.01), and 5000-m (P < 0.01) and 1609-m (P < 0.05) run times with no significant differences between the groups. The TM VO2max pre/post values were 55.3 +/- 3.0 to 58.2 +/- 3.0 and 55.6 +/- 3.8 to 58.9 +/- 2.4 ml.kg-1.min-1 for the run group and cross-trained group, respectively. Posttraining submaximal treadmill running showed statistically significant pace increases of 18.7 (run) and 16.1 (cycle/run) m.min-1 with similar heart rate, blood lactate, and RQ values as pretraining. Results indicate that 5 wk of either mode of training can significantly improve aerobic capacity and run performance.

A physiological comparison of forward vs reverse wheelchair ergometry.

The purpose of this study was to compare metabolic and cardiopulmonary responses for forward wheelchair ergometry (FOR) and reverse wheelchair ergometry (REV) at equal power outputs (PO) levels. Moderately active able-bodies (N = 21) subjects exercised at 3-min stages at PO levels of 15, 20, 25, and 30 W for each mode of ergometry. Oxygen uptake (VO2), pulmonary ventilation (VE), respiratory exchange ratio (RER), heart rate (HR), percent net mechanical efficiency (ME), revolutions per minute (RPM) and strikes per minute (SPM) were determined at each PO level. With the exception of RER, all the physiological responses (VO2, VE, and HR) were higher for FOR exercise (P < 0.05) than REV exercise. ME increased with PO and was higher (P < 0.05) for REV than FOR at each PO level. SPM values for the REV were lower (P < 0.01) by almost half of that for the FOR exercise, although RPM remained constant between modes during all four stages. In general, these data suggest that reverse wheelchair ergometry is physiologically more efficient than conventional wheelchair ergometry and should be studied further as an alternative method for wheelchair ambulation.

Effects of stair-climbing vs run training on treadmill and track running performance.

Physically active college age women were evaluated to determine the effects of 9 wk of stair-climbing (Stairmaster Gauntlet) vs run training on 2414-m run time and treadmill measured aerobic capacity (VO2max) and submaximal physiological parameters. Subjects were randomly assigned to a stair-climbing (STAIR N = 11) (43.8 +/- 1.5 ml.kg-1.min-1) (mean +/- SEM) or run training (RUN N = 12) (44.2 +/- 1.8) group, training 4 d.wk-1 at 70-80% of maximum heart rate (MHR) for 30 min progressing to 85-90% MHR for 45 min. The STAIR group significantly increased (P < 0.01) their VO2max by 12% and decreased (P < 0.01) their 2414-m run time of 12.8 min by 8%. The RUN group increased (P < 0.01) their VO2max 16% and decreased run time (P < 0.01) 11% from 13.1 min. Submaximal treadmill runs at the same speed and grade demonstrated significant decreases in %VO2max and % MHR (P < 0.01) for both groups. The data support the use of stair-climbing exercise as an alternative mode to running with similar treadmill and running performance results subsequent to 9 wk of training.

Specificity effects of run versus cycle training on ventilatory threshold.

This study compared the effects of 9 weeks of run (RT) versus cycle (CT) training on ventilatory threshold (Thv) determined during treadmill (TM) and cycle ergometer (CE) graded exercise testing. Sixteen college age men were assigned to a RT or CT group and performed a TM and a CE test before and after training. Both training groups performed similar training protocols which initially consisted of continuous exercise 4 days.week-1 at 75-80% maximum heart rate (fc, max) for 45 min. Training intensity was later increased to 80-85% fc, max and interval training (90-95% fc, max) was incorporated 2 days.week-1 into the continuous training. Both groups showed significantly improved maximal oxygen consumption (VO2 max) on both TM and CE tests (P < 0.01) with no significant differences between the groups. Significant Thv increases (P < 0.05) were found on TM tests for RT (n = 8) and CT (n = 8) groups [mean (SD); 443 (438) and 373 (568) ml O2 x min-1, respectively] with no difference between the groups. Results from the CE tests revealed a significant Thv increase (P < 0.01) for the CT group [566 (663) ml O2 x min-1] with no change for the RT group. The Thv improvement noted for the RT group was significantly different (P < 0.05) comparing CE with TM tests but not for the CT group. The results indicate that CT and RT improvement in Thv for runners is dependent upon mode of training and testing, and there is an apparent dissociation of VO2 max and Thv specific to training.

Evaluation of professional preparation in athletic training by employed, entry-level athletic trainers.

The purpose of this study was to determine the perceived adequacy of professional preparation in athletic training among employed, entry-level certified athletic trainers. Data were gathered by means of a self-reporting questionnaire designed specifically for the study. There were 277 questionnaires mailed, and 183 entry-level certified athletic trainers (66%) responded to the survey. Demographic and employment characteristics of the respondents were examined. Respondents rated their perceptions of adequacy of professional preparation and growth in several academic and clinical task areas. Entry-level athletic trainers felt more prepared in the areas of prevention of athletic injuries/illnesses, evaluation and recognition of athletic injuries/illnesses, and first aid/emergency care. They felt less prepared in the areas of rehabilitation and reconditioning, organization and administration of athletic training programs, counseling and guidance of athletes, and education of athletes. Many entry-level certified athletic trainers were not strongly impressed with the adequacy of the number of clinical hours required or the areas of clinical experiences encountered during their professional preparation programs. Respondents felt that their mentors/certified athletic trainers could have provided more leadership, guidance, and evaluation. According to this study, professional preparation programs in athletic training are adequately preparing entry-level professionals, but certain task areas need increased emphasis.

Changes in cardiovascular function during inversion.

Although inversion therapy is used increasingly as a therapy for musculoskeletal back disorders, its effects on cardiovascular function have not been systematically determined. Heart rate, blood pressure and echocardiographic measurements were performed in 20 normal male volunteers before, during and after bent-knee inversion. Compared to control measurements in the supine position, inversion significantly increased heart rate, systolic and diastolic blood pressure, rate-pressure product, systemic vascular resistance and left ventricular (LV) wall stress. Inversion also resulted in a significant decrease in LV diastolic volume, cardiac output and ejection fraction. Thus inversion produces an increase in LV afterload and myocardial oxygen demand concomitantly with a decrease in LV preload and global systolic function, and may be contraindicated in patients with cardiovascular disease.

Relationship of Body Core Temperature and Warm-up to Knee Range of Motion.

This study examined the effects of submaximal, treadmill exercise-induced body core temperature (BCT) increase on selected knee range of motion (ROM). Twenty males, 18-35 years old, were tested (randomized crossover) for ROM, BCT, and heart rate (HR), followed by either Treatment I (20 minutes of rest) or Treatment II (20 minutes of submaximal running). The two treatments were subsequently followed by a two-minute passive stretch. Range of motion was assessed before and after passive stretch treatment intervention. Treatment means differed for BCT and HR (p < 0.001) but not for ROM after exercise intervention. It was concluded that 20 minutes of exercise increased BCT (>1 degrees C) but had no effect on knee ROM. J Orthop Sports Phys Ther 1991;13(3):126-131.

Sampling and analysis of acetic anhydride in air.

This paper describes the development of a new method for monitoring acetic anhydride in the presence of acetic acid in the occupational environment. The method consisted of collecting airborne acetic anhydride on a solid sorbent, desorbing it with acetone and analyzing it by gas chromatography. During the development of this method various parameters such as selection of column, selection of solid sorbent, selection of desorber solvent, effects of humidity, flow rate, total sample volume, desorption efficiency, and shelf-life of samples were studied. Interference from methyl acetate, water, formic acid, and acetic acid was also tested with the determination of acetic anhydride.

Monitoring personal exposure to ethylenediamine in the occupational environment.

A method for monitoring exposure to ethylenediamine (EDA) in the occupational environment is described. The EDA is adsorbed on activated silica gel, desorbed with 0.5 percent aqueous cupric chloride, and analyzed by gas chromatography using a 2 percent KOH on a Chromosorb 103 column. The method is sensitive to 200 micrograms/mL EDA and can detect 1.0 ppmv EDA in samples collected for 4.5 hours at a 300 cc per minute flow. The method has been evaluated in the laboratory and under plant conditions. Other amines do not interfere with the determination of EDA.

Relationships among selected tests of spatial orientation ability.

The purpose of this study was to investigate the relationships between selected tests of spatial orientation ability. 2 tests which have been used as predictors of spatial ability (Guilford-Zimmerman Aptitude Survey, Parts V and VI) plus 2 newly developed tests designed to measure that ability were given to 202 Junior high school boys aged 11-15 yr. 3 of these tests were of the paper and pencil type while one was a physical performance (tumbling) test. The paper-and-pencil tests correlated significantly with each other (.62, .61, .44) but the physical performance test did not correlate significantly with any of the other tests.