Reliability of Phase-Velocity Measurements of Tibial Bone.Several noninvasive non·in·va·sive adj. 1. Not penetrating the body, as by incision. Used especially of a diagnostic procedure. 2. Not invading healthy tissue. methods are available for the in vivo in vivo /in vi·vo/ (ve´vo) [L.] within the living body. in vi·vo adj. Within a living organism. in vivo adv. assessment of bone properties. These methods include densitometric measures of bone mineral content and density[1,2] and biomechanical Biomechanical may refer to:
The mechanical properties of the tibia tibia: see leg. can be assessed by measuring the bending stiffness The bending stiffness  of a beam (or a plate) relates the applied bending moment to the resulting deflection of the beam. It is the product of the elastic modulus of the tibia using the phase velocity Phase velocityThe velocity of propagation of a pure sine wave of infinite extent. In one dimension, for example, the form of the disturbance for such a wave is given by y(x, t) = A sin [2π(x/λ - t/T of flexural flexural pertaining to the flexure of a joint. flexural deformity fixation of joints in flexion. In the newborn called contracted calves or foals. waves passing through it.[4] In accordance with the Bernoulli-Euler model, the bending stiffness of a rotationally symmetrical long beam is proportional to the phase velocity of fourth-order flexural waves.[4] The validity of measurements of this relationship for the tibia has been confirmed in vitro in vitro /in vi·tro/ (in ve´tro) [L.] within a glass; observable in a test tube; in an artificial environment. in vi·tro adj. In an artificial environment outside a living organism. . Bending stiffness for 21 tibias was measured using 3-point bending tests, and the measurements were compared with values for bending stiffness calculated from measurements of phase velocity and area moment of inertia inertia (ĭnûr`shə), in physics, the resistance of a body to any alteration in its state of motion, i.e., the resistance of a body at rest to being set in motion or of a body in motion to any change of speed or change in direction of of tibial tibial pertaining to the tibia. tibial crest a longitudinal prominence on the cranial border of the proximal tibia. Its proximal end (tibial tubercle) has a growth plate separate from the proximal tibia; hyperflexion injuries to bone. This comparison resulted in a very good correlation (r=.96). To define the relationship between bending stiffness and fracture resistance of tibial bone, all 21 tibias were loaded until fracture. This loading gave an impression of maximum bending moment A bending moment exists in a structural element when a moment or torque is applied to the element so that the element bends. Moments and torques are measured as a force multiplied by a distance so they have units such as newton.metres (N.m) and foot.pounds (ft.lb). of the tibial bone. The authors in that study concluded that measurements of bending stiffness are related to the risk of fracture.[4] The results of an in vivo assessment of the bending stiffness of human tibias with the new Bone Stiffness Measurement Devise--Swing(*) (BSMD--Swing) demonstrated that bone mineral measurements are not suitable predictors for evaluating changes in the mechanical properties of long bones.[5] For the purpose of monitoring the changes that occur in the bending stiffness of the shin bone under low gravity, thereby providing an indication of the strength changes that could occur during long-term exposure to low gravity, the BSMD--Swing was adapted under European Space Agency European Space Agency (ESA), multinational agency dedicated to the promotion, for exclusively peaceful purposes, of cooperation among European states in space research and technology. (ESA 1. (architecture) ESA - Enterprise Systems Architecture. 2. (body) ESA - European Space Agency. ) contract. After successful completion of its tasks on the EUROMIR 95 mission, it was concluded that the BSMD--Swing was an easy-to-operate, noninvasive device that might be used to determine changes in the bending stiffness of the bone, either on the ground as the effect of long-term immobilization Immobilization Definition Immobilization refers to the process of holding a joint or bone in place with a splint, cast, or brace. This is done to prevent an injured area from moving while it heals. or in orbit.[6,7] In vivo, the phase velocity is calculated from 8 accelerometers that have been pressed firmly against the tibia. The flexural wave is produced by a mechanical impact to the head of the tibia, with a force of the impact comparable to that of a patellar patellar of or pertaining to the patella. patellar cartilage a cartilaginous process borne on the medial side of the patella of horses and cattle. tendon reflex tendon reflex n. A myotatic or deep reflex in which the muscle stretch receptors are stimulated by percussing the tendon of a muscle. test. Figure 1 shows the configuration of the hardware and a schematic A graphical representation of a system. It often refers to electronic circuits on a printed circuit board or in an integrated circuit (chip). See logic gate and HDL. operational configuration for a BSMD--Swing measurement. [Figure 1 ILLUSTRATION OMITTED] A future application of the BSMD--Swing by clinicians could allow them to make decisions about the strength of bone of individual patients (eg, when a clinician clinician /cli·ni·cian/ (kli-nish´in) an expert clinical physician and teacher. cli·ni·cian n. needs to determine whether a patient has enough bone strength to safely start loading exercises, when a clinician needs to determine whether a patient's bone strength has decreased after immobilization). Monitoring change in bone strength could indicate whether undertaking a corrective measure or medical attention before exercise is needed to prevent bone damage, specifically brittle breakage.[6] A prerequisite for the use of a measuring device is that measurements obtained with it are reliable and valid. Reliability refers to the relative absence of measurement errors and was defined for the purpose of this study as consistency of measurement results. An important feature of most clinical measurements is that they are performed and interpreted on individual patients, not on groups. To determine the clinical usability of the BSMD--Swing, the type of reliability indexes used should be appropriate. Proportional coefficients of reliability such as the Pearson product-moment correlation coefficient Noun 1. Pearson product-moment correlation coefficient - the most commonly used method of computing a correlation coefficient between variables that are linearly related product-moment correlation coefficient (r) and the intraclass correlation In statistics, the intraclass correlation (or the intraclass correlation coefficient[1]) is a measure of correlation, consistency or conformity for a data set when it has multiple groups. coefficient (ICC ICC See: International Chamber of Commerce ) are frequently used. Correlation coefficients Correlation Coefficient A measure that determines the degree to which two variable's movements are associated. The correlation coefficient is calculated as: , however, are most appropriate for group studies, not for measurements on individual patients as in clinical practice.[8-10] Another requirement for a study in which the reliability of measurements obtained with a measuring device is to be investigated is that the study design should correspond with how the measure is used in practice.[10] In our study, the reliability of phase-velocity measurements obtained with the BSMD--Swing was studied by means of generalizability theory Generalizability theory (G Theory) is a statistical framework for conceptualizing, investigating, and designing reliable observations. It was originally introduced by Lee Cronbach and his colleagues. .[10] Multiple sources of measurement error, such as occasion (O), clinician (C), and repetition (R), were estimated. For that purpose, generalizability theory uses the factorial factorial For any whole number, the product of all the counting numbers up to and including itself. It is indicated with an exclamation point: 4! (read “four factorial”) is 1 × 2 × 3 × 4 = 24. analysis-of-variance (ANOVA anova see analysis of variance. ANOVA Analysis of variance, see there ) model. For each factor and interaction, associated variance components (denoted as [[Sigma].sup.2]) are estimated, using a random-effects ANOVA. The objectives of our study were (1) to examine, with the help of generalizability theory, the reliability of phase-velocity measurements of flexural waves propagating through human tibial bone and (2) to assess reliability indexes that allow direct clinical interpretation of measurements obtained for individual patients for intrarater applications. For corresponding statistical terms and formulas, the reader is referred to the literature.[11-14] Materials and Methods Designs Generalizability theory distinguishes between generalizability (G) and decision (D) studies. G study. Phase-velocity measurements in a sitting position were tested on a sample of men without known orthopedic or neurological neurological, neurologic pertaining to or emanating from the nervous system or from neurology. neurological assessment evaluation of the health status of a patient with a nervous system disorder or dysfunction. impairments using a BSMD--Swing.[4-7,15,16] During 2 separate testing sessions, 2 clinicians obtained the measurements. During each session, 2 measurements were obtained on the right tibia. Because of the requirement that no change in soft tissue tension must appear between sessions, the time interval between sessions was set at 1 hour. In an attempt to replicate clinical practice, in which patients change position between consecutive sessions, measuring devices This is an incomplete list of measuring devices. word Measures accelerometer acceleration actinometer heating power of sunlight alcoholometer alcoholic strength of liquids altimeter altitude ammeter electric current, amperage and marks were removed and the subjects left the testing position at the end of each session. On a second occasion 1 week later, a time period in which no change in bone consistency was expected, there were 2 more test sessions. On the second occasion, the order in which the clinicians tested a subject was reversed (Fig. 2). [Figure 2 ILLUSTRATION OMITTED] This part of the study was conducted as a G study, in which the measuring device was tested. In this part of the study, potential sources of measurement error and their interactions were identified as factors.[10] The design is a completely random-effects design, in which the object of measurement is the subject (P; [n.sub.p] = 10) and the measurement factors are occasion (O; [n.sub.o] = 2), clinician (C; [n.sub.c] = 2), and repetition (R; [n.sub.r] = 2). Each subject was measured under all measurement conditions, denoted as a crossed 4-way P X O x C X R design. D study. Within a generalizability framework, the magnitude of multiple sources of measurement error was assessed for each test. Analyses of intrarater and interrater reliability were conducted on 2 data sets. The first data set included 2 repetitions from 2 sessions for each subject. For each clinician, a crossed P x O x R design was used, with the sessions ordered to time. In this example, the clinician's measurements of a subject obtained on different occasions and repetitions will be compared. In this example, mixed designs are appropriate, with the factor of clinician fixed and the factors of occasion and repetition random. The second data set included 2 repetitions from 2 clinicians for each patient. For the pair of clinicians, a crossed P x C x R design was used in which sessions were ordered with respect to the clinician. In this example, the measurements obtained by different clinicians will be compared. Each clinician is seen as a random sample among all clinicians who could apply the BSMD--Swing measurements. The factor of clinician, therefore, is random. Combined with the random factors of occasion and repetition, this leads to random-effects designs, with 3 random measurement factors. For both designs, variance components were averaged over clinicians. In this part of the study, we investigated the possible application of the BSMD--Swing in a clinical setting. The absolute error variance was calculated for a D study,[10] based on the estimated variance components from the G study. In this presented case, the D study refers to applications in which a subject will be measured by one clinician only (intrarater reliability). In this type of study, a clinician's measurements of a subject are compared over occasions and repetitions. The clinician's measurements will not be compared with those of any other clinician. In this example, mixed designs are appropriate, with the factor of clinician fixed and the factors of occasion and repetition random. The measurement error was assessed for a random D study design (P x O x R) in which a single score is used as a measurement result and the factor of occasion varied. Calculation of Reliability Indexes Before conducting a D study, the magnitude of measurement error that a decision-maker (eg, a physical therapist) must take into account can be assessed from the variance components estimated in the G study.[4] Measurement error was assessed from the mean variance components estimated in the G study. For the D study design, all variance components, excluding the estimated variance between subjects, contributed to the absolute error variance. The estimate of standard error of measurement (SEM) was determined by calculating the square root of the absolute error variance. For the interpretation of a single measurement, the 95% confidence interval confidence interval, n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. was calculated as [+ or -] 1.96 x SEM. For the comparison of 2 consecutive measurements in one person, the smallest detectable difference (SDD (Software Design Description) The architecture of an information system. See IDD. ) at the .05 level was calculated as 1.96 x [square root of 2] x SEM.[10,17] Only differences greater than the SDD represent a real (non-error) change in propagation The transmission (spreading) of signals from one place to another. of phase velocity in bone.[18] Clinicians The clinicians who performed the measurements, one physician and one research assistant who were responsible for monitoring cosmonauts, were both experienced in applying the BSMD--Swing. Both clinicians attended 2 training sessions in which they learned the test protocols and practiced their performance according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. the standard. Both testers applied the BSMD--Swing at different locations. To ensure that they would apply the BSMD--Swing in the same way in this study, they coordinated their experiences and learned (or relearned) the test protocols. All tests on cosmonauts administered by the clinicians took place on earth as preflight-postflight measurements. These measurements, therefore, corresponded to real-world circumstances. After the training sessions, the clinicians received a manual for the BSMD--Swing test protocol with detailed instructions for taking the measurements. Subjects Ten male subjects with no history of tibial bone fractures and without known orthopedic or neurological impairments participated in the first part of the study. All subjects received written and oral information on the research and gave written informed consent before participating in the study. The mean age of the subjects was 33.3 years (SD=7.7, range=24-47). Their mean body weight was 71.2 kg (SD=5.2, range=64-80), and their mean height was 176.6 cm (SD=5.7, range = 170-189). For the clinical trial, 17 persons (16 male, 1 female) with recent spinal cord injuries Spinal Cord Injury Definition Spinal cord injury is damage to the spinal cord that causes loss of sensation and motor control. Description Approximately 10,000 new spinal cord injuries (SCIs) occur each year in the United States. (SCIs) gave their informed consent to participate in the study. None of these subjects had a history of tibial bone fracture, nor had they experienced fractures of the leg(s) in concurrence CONCURRENCE, French law. The equality of rights, or privilege which several persons-have over the same thing; as, for example, the right which two judgment creditors, Whose judgments were rendered at the same time, have to be paid out of the proceeds of real estate bound by them. Dict. de Jur. h.t. with their spinal injury. The mean age of the subjects was 33.7 years (SD=12.6, range=16-57). Their mean body weight was 70.9 kg (SD=9.7, range=63-94), and their mean height was 176.6 cm (SD=6.2, range=167-188). Measuring Device The BSMD--Swing is a measuring device comprising a hand-held electromechanical The use of electricity to run moving parts. Disk drives, printers and motors are examples. Electromechanical systems must be designed for the eventual deterioration of moving components that wear over time. The first TVs were electromechanical systems (see video/TV history). hammer, a shin-mounted receiver assembly containing 8 piezo "Piezo", derived from the Greek piezein, which means to squeeze or press, is a prefix used in:
n. A reference mark (  ) used in printing and writing. Also called diesis.Noun 1. ]) presented test protocols to the clinician and provided feedback about measurement conditions and measurement results on the computer screen. A prototype of the BSMD--Swing was used in this study. The BSMD--Swing measures the phase velocity of flexural waves passing through the tibia. A more detailed description of the device can be found elsewhere.[4-6,15,16] Standard Test Protocols Body weight and height were measured for each subject. Length of the tibia was measured as the distance between the medial medial /me·di·al/ (me´de-il) 1. situated toward the median plane or midline of the body or a structure. 2. pertaining to the middle layer of structures. me·di·al adj. knee joint cleft and the lower border of the medial malleolus The medial surface of the lower extremity of tibia is prolonged downward to form a strong pyramidal process, flattened from without inward - the medial malleolus.
Measurements of the phase velocity of flexural waves propagating through the tibia of the subjects without known orthopedic or neurological impairments were obtained while the subjects assumed a sitting position with the back and thigh supported and the lower extremity lower extremity n. The hip, thigh, leg, ankle, or foot. Also called inferior limb, pelvic limb. in a horizontal position horizontal position, n a posture in which the body lies flat and the feet and head remain on the same level. Also called supine. . For the subjects with SCI (Scalable Coherent Interface) An IEEE standard for a high-speed bus that uses wire or fiber-optic cable. It can transfer data up to 1GBytes/sec. (hardware) SCI - 1. Scalable Coherent Interface. 2. UART. , these measurements were obtained with the subjects in a lying position with the thigh supported. The right leg of the subjects without known orthopedic or neurological impairments was measured twice (G study), and the right and left legs of the subjects with SCI were measured once each (D study). The receiver unit of the BSMD--Swing was positioned perpendicular to the tibia on the medial surface, at 50% of the tibia length distally from the knee joint cleft. When the receiver was firmly fixed on the medial surface of the tibia and the hammer was positioned, the test clinician started the measurements by pressing the start key on the computer. The computer sent a specific pulse waveform The shape of a signal. See wavelength, sine wave and square wave. via the analog output board to the hammer, which then delivered a small blow on the tibia. The resulting shock waves in the tibia were detected by the receiver, digitized, and stored in the control unit. The computer gathered these data, checked them on their frequency spectrum, and compared the amplitudes of the 8 different channels. These data were simultaneously displayed on the screen and stored on the hard disk. Detailed data analysis was performed on an alpha station. The hammer and receiver were repositioned 3 times, with 5 pulses being measured each time. For each hammer pulse, the BSMD--Swing produced a set of 8 signal curves. One measurement contained 15 pulses. Data Analysis Data analysis was conducted on the phase velocities of 10 subjects who had 2 measurements on the right leg (G study) and on the phase velocities of 17 subjects with one measurement on the right leg and one measurement on the left leg (D study). After checking for ANOVA assumptions,[13] an ANOVA for a random-effects design was carried out. Unbiased estimates of the variance components were obtained from the mean squares.[11] Analysis was performed using a personal computer version of the GENOVA program.[19] Variance components were calculated for: * patient (P), * occasion (O), * clinician (C), and * repetition (R); for the 2-way interaction for: * patient and occasion (PO), * patient and clinician (PC), * patient and repetition (PR), * occasion and clinician (OC), * occasion and repetition (OR), and * clinician and repetition (CR); for the 3-way interaction for: * patient, occasion, and clinician (POC (Proof Of Concept) See PoC exploit. POC - Point Of Contact ), * patient, clinician, and repetition (PCR PCR polymerase chain reaction. PCR abbr. polymerase chain reaction Polymerase chain reaction (PCR) ), and * occasion, clinician, and repetition (OCR OCR in full optical character recognition Scanning and comparison technique intended to identify printed text or numerical data. It avoids the need to retype already printed material for data entry. ); and for the 4-way interaction for: * patient, occasion, clinician, and repetition, confounded with the residual random error (e) (POCR POCR Proof of Compliance Report , e). According to the approach of Cronbach et al,[11] relatively small negative estimates of variance components were set to zero. For each estimate of a variance component, the standard error was calculated using the number of measurement conditions in this G study ([n.sup.o], [n.sup.c], [n.sup.r]).[11] The factor of patient (P) is not a measurement condition; therefore, this factor is not a source of measurement error. Results G Study In Table 1, mean values and standard deviations In statistics, the average amount a number varies from the average number in a series of numbers. (statistics) standard deviation - (SD) A measure of the range of values in a set of numbers. of the measured phase velocities of the tibia over 2 repetitions are listed for each subject and occasion-clinician combination. The magnitude of the phase velocities measured in this G study varied from 400.1 to 507.7 m [multiplied by] [s.sup.-1]. In Table 2, the results of the ANOVA are given, as well as the estimates of variance components for all factors and interactions. Table 2 indicates that the variance components for occasion and repetition were negligible, and the main effect for clinician was very small compared with the magnitude of the phase velocities measured. These findings imply that the mean phase velocity was not different from one occasion to another or from one repetition to another. Table 1. Tibial Phase Velocities (in Meters per Second) Over 2 Repetitions for Each Subject
Occasion 1
Subject Clinician 1 Clinician 2
No. [bar]X SD [bar]X SD
1 443.0 15.4 466.9 36.0
2 425.7 24.6 426.5 35.7
3 482.7 24.4 467.6 26.7
4 400.1 21.4 402.0 19.3
5 456.3 27.0 441.1 26.0
6 477.4 25.4 468.4 47.6
7 425.1 22.4 434.2 30.8
8 454.3 19.1 474.6 24.6
9 479.1 30.6 507.7 37.6
10 433.6 27.7 407.6 26.2
Occasion 2
Subject Clinician 1 Clinician 2
No. [bar]X SD [bar]X SD
1 446.7 26.6 441.0 30.3
2 431.4 25.9 476.2 38.4
3 459.1 16.7 496.4 26.0
4 415.9 23.4 403.5 17.7
5 435.3 16.3 442.3 25.0
6 455.5 26.9 484.5 43.3
7 411.5 15.9 429.6 21.7
8 451.0 19.5 486.7 28.4
9 499.6 22.4 505.7 32.8
10 418.3 28.1 419.2 24.6
Table 2. G Study Analysis-of-Variance Results and Estimates of Variance Components(a) Source df SS MS Patient (P) 9 58990.38 6554.49 Occasion (O) 1 11.02 11.02 Clinician (C) 1 1596.05 1596.05 Repetition (R) 1 7.39 7.39 PO 9 3014.4 334.93 PC 9 3000.75 333.42 PR 9 774.88 86.10 OC 1 728.08 728.08 OR 1 0.05 0.05 CR 1 87.01 87.01 POC 9 3559.57 395.51 POR 9 1536.21 170.69 PCR 9 1598.48 177.61 OCR 1 117.71 117.71 POCR,e 9 686.91 76.32 Total 79 75708.89 Source [[Sigma].sup.2] SEE Patient (P) 808.44 351.20 Occasion (0) 0 16.16 Clinician (C) 26.55 36.41 Repetition (R) 5.6 4.17 PO 0 58.73 PC 0 58.87 PR 0 28.98 OC 14.56 31.31 OR 0 6.24 CR 0 7.26 POC 159.59 85.88 POR 47.18 39.86 PCR 50.64 41.21 OCR 4.14 10.15 POCR,e 76.32 32.54 Total (a) Negative estimates are replaced by zero. [[Sigma].sup.2] = estimate of variance component, SEE = standard error of estimate, e = residual error (Mensuration) See Error, 6 See also: Residual . The 2-way occasion-clinician interaction (OC) showed that one clinician achieved higher scores on the first occasion, whereas the other clinician achieved higher scores on the second occasion. Compared with the magnitude of the phase velocities measured, this factor is small. The negligible patient-clinician and patient-occasion variance components show that the same subjects produced the same phase velocities when measured by clinician 1 and clinician 2, and on occasion 1 and occasion 2. A summation summation n. the final argument of an attorney at the close of a trial in which he/she attempts to convince the judge and/or jury of the virtues of the client's case. (See: closing argument) of the 3-way interaction effects including the factor of occasion (POC, POR POR problem-oriented record. POR abbr. problem-oriented record POR Problem-Oriented Record. , OCR) yielded a variance of 210.9. This summated variance implies that some subjects achieved larger phase velocities during the first occasion, whereas other subjects achieved larger phase velocities during the second occasion. A summation of the 3-way interaction effects including the factor of repetition yielded a variance of 101.9. A summation of the 2-way interaction effect (OC) and the 3-way interaction effects including the factor of clinician yielded a variance of 228.9. An interpretation of these third-order factors is difficult. The 4-way interaction term was confounded with residual error and, therefore, is not interpretable. This component, however, is not extremely large. This finding means that a large portion of the error variance can be explained by the factors chosen in the design of the study and their interactions. D study The SEMs that were obtained in the D study are given in Table 3. Values are given for measurements by one fixed clinician and one repetition of measurement. For measurement results based on single scores by one clinician at one occasion and one repetition (design 1), the SEMs for mixed designs were 39.7 m [multiplied by] [s.sup.-1] for the right leg and 34.6 m [multiplied by] [s.sup.-1] for the left leg. For those clinical settings in which only one clinician is available but a patient can be measured on 2 occasions, between which no treatment effect is expected, the SEMs for a single score (one measurement; design 2) were 14.4 m [multiplied by] [s.sup.-1] for the right leg and 14.9 m [multiplied by] [s.sup.-1] for the left leg. If the clinician is able to perform a measurement on a third occasion, the SEMs for a single score (design 3) were 11.9 m [multiplied by] [s.sup.-1] for the right leg and 12.8 m [multiplied by] [s.sup.-1] for the left leg. Table 3. Summary of Measurements for a Single Therapist (Mixed Designs)(a)
No. of Measurement Conditions
Design Measurement Result O C R
1 Single score right leg 1 1 1
Single score left leg 1 1 1
2 Single score right leg 2 1 1
Single score left leg 2 1 1
3 Single score right leg 3 1 1
Single score left leg 3 1 1
95%
Confidence
SEM Interval
(m [multiplied by] (m [multiplied by]
Design [s.sup.-1]) [s.sup.-1])
1 39.7 [+ or -] 77.8
34.6 [+ or -] 67.9
2 14.4 [+ or -] 28.2
14.9 [+ or -] 29.2
3 11.9 [+ or -] 23.3
12.8 [+ or -] 25.1
Smallest
Detectable
Difference
(m [multiplied by]
Design [s.sup.-1])
1 110.0
96.0
2 39.4
41.2
3 33.0
35.5
(a) Measurement conditions: O = occasion (random factor), C = clinician (fixed factor), R = repetition (fixed factor). Reliability indexes: SEM = estimate of standard error of measurement, 95% confidence interval = [+ or -] 1.96 X SEM, smallest detectable difference 1.96 x [square root of 2] X SEM ([Alpha]=.05). To facilitate the interpretation of measurement results in clinical practice, the 95% confidence interval of a measurement and the SDD for each design are also given in Table 3. The SDDs in the studied applications show that for measurements obtained for persons with SCI, only changes larger than 96.0 to 110.0 m [multiplied by] [s.sup.-1] (1 measurement occasion), 39.4 to 41.2 m [multiplied by] [s.sup.-1] (2 measurement occasions), or 33 to 35.5 m [multiplied by] [s.sup.-1] (3 measurement occasions) can be interpreted as real changes in phase-velocity propagation through tibial bone. Discussion Neither a general effect over clinicians nor a marked effect over occasion or repetition was found. In this study, therefore, the main effects of occasion, repetition, and clinician were unimportant un·im·por·tant adj. Not important; petty. un  im·por tance n. sources
of measurement error. The measurement variability was scattered ScatteredUsed for listed equity securities. Unconcentrated buy or sell interest. mainly over some 3-way interaction components and the residual component, indicating that these interaction effects were important sources of measurement error. Standard errors associated with the larger variance components were relatively small, indicating that the estimates of these components were rather stable. The SEMs that must be considered in some possible clinical studies are given in Tables 4 and 5. For measurement results based on single scores by one clinician at one occasion and one repetition (design 1; Tabs. 4 and 5), the SEMs were 8.4 and 8.9, respectively. For those clinical settings in which only one clinician is available but a patient can be measured during 2 occasions, between which no treatment effect is expected, the SEM for the mean score over 2 repetitions (design 4; Tab. 4) was 8.1. To facilitate the interpretation of measurement results in clinical practice, the 95% confidence interval of a measurement and the SDD for each design are also given in Tables 4 and 5. Table 4. Intrarater Reliability of Phase-Velocity Measurements With the Bone Stiffness Measurement Devise--Swing: G Study Summary of Tests, Using a P X O X R Design(a)
No. of
Measurement
Measurement Conditions
Design Result O R
1 Single score 1 1
2 Mean score 1 2
3 Mean score 2 1
4 Mean score 2 2
95%
Confidence
SEM Interval
Design (m [multiplied by] (m [multiplied by]
[s.sup.-1]) [s.sup.-1])
1 8.4 [+ or -] 16.5
2 7.3 [+ or -] 14.4
3 9.8 [+ or -] 19.1
4 8.1 [+ or -] 15.9
Smallest
Detectable
Difference
(m [multiplied by]
Design [s.sup.-1])
1 23.3
2 20.3
3 27.0
4 22.5
(a) Measurement conditions: 0 = occasion (random factor), R = repetition (random factor). Reliability indexes: SEM = standard error of measurement, 95% confidence interval = [+ or -] 1.96 x SEM, smallest detectable difference = 1.96 x [square root of 2] x SEM ([Alpha] =.05). Table 5. Intrarater Reliability of Phase-Velocity Measurements With the Bone Stiffness Measurement Devise--Swing: G Study Summary of Tests, Using a P x C x R Design(a)
No. of
Measurement
Measurement Conditions
Design Result C R
1 Single score 1 1
2 Mean score 1 2
3 Mean score 2 1
4 Mean score 2 2
95%
SEM Confidence
(m [multiplied by] Interval
Design [s.sup.-1]) (m [multiplied by]
[s.sup.-1])
1 8.9 [+ or -] 17.4
2 9.5 [+ or -] 18.6
3 5.7 [+ or -] 11.1
4 8.2 [+ or -] 16.0
Smallest
Detectable
Difference
(m [multiplied by]
Design [s.sup.-1])
1 24.7
2 26.3
3 15.8
4 22.6
(a) Measurement conditions: C = clinical (random factor), R = repetition (random factor). Reliability indexes: SEM = standard error of measurement, 95% confidence interval = [+ or -] 1.96 x SEM, smallest detectable difference 1.96 x [square root of 2] x SEM ([Alpha] = .05). For a researcher, the approach of generalizability theory for assessing reliability provides a practical tool. Important sources of measurement error can be determined and accounted for. For example, from the first part of the study, it can be concluded that some 3-way interaction combinations that include the factor of clinician are sources of measurement error. This error can possibly be reduced by better standardization standardization In industry, the development and application of standards that make it possible to manufacture a large volume of interchangeable parts. Standardization may focus on engineering standards, such as properties of materials, fits and tolerances, and drafting of the measurement protocol with respect to how the test is conducted by the clinicians. A possible approach for diminishing the various occasion interaction effects is to introduce an extra test session. Further reduction can be realized by adjusting the measurement design. In this way, the residual measurement error can also be reduced. In clinical practice, however, it is time consuming to add an extra test session or to increase the number of measurement conditions. The small differences between intrarater and interrater reliability (Tabs. 4 and 5) indicate that application of the BSMD--Swing is relatively independent of the clinician. For clinicians who want to evaluate a patient's changes in bone stiffness, the indexes of reliability used in this study could be informative, especially the SDD. From the SDD, a clinician knows what differences need to be measured in order to conclude that a measurement reflects a real change rather than measurement error. For clinical application of measurements, the SDD must be small enough to detect clinically important changes during the course of illness or during interventions aimed at influencing the bone. In future studies, other researchers will need to determine whether the values found for the SDD (Tab. 3) meet these requirements satisfactorily. Future studies are planned to answer this question. Problems in estimating the variance components are the "Achilles heel Achilles heel Noun a small but fatal weakness [Achilles in Greek mythology was killed by an arrow in his unprotected heel] Achilles heel n → talón m de Aquiles " of generalizability theory.[10,12] Estimates of variance components are unstable and may even be negative, especially with small sample sizes.[12] With respect to the last point, the calculation procedure used in this study gives unbiased estimates, whereas negative estimates are set to zero.[12] To attain stable estimates of variance components, larger samples are needed in a reliability study.[10] The SEMs presented in Table 3 appear to be large; however, they can be reduced by adjusting the test design. The results of the clinical part of our study provide clinicians with information as to whether a single occasion or more occasions are needed to reach the desired level of reliability in the assessment of a patient's phase-velocity propagation. This possibility to adjust the test design offers the opportunity to differentiate between situations. When important decisions are to be made (eg, to stop or change therapies), it can be worthwhile to test a patient during 2 or 3 occasions and to conduct several repetitions of the measurement. Most noninvasive measures of mineral content (eg, photon absorptiometry ab·sorp·ti·om·e·try n. A diagnostic technique for measuring bone mineral density in which an image of bone is produced from computerized analysis of absorption rates of photons directed in a focused beam at a body part. , computed tomography Computed tomography (CT scan) X rays are aimed at slices of the body (by rotating equipment) and results are assembled with a computer to give a three-dimensional picture of a structure. ) have an accuracy of a few percentage points. Because they measure volumetric volumetric /vol·u·met·ric/ (vol?u-met´rik) pertaining to or accompanied by measurement in volumes. vol·u·met·ric adj. Of or relating to measurement by volume. mineralization Mineralization The process by which the body uses minerals to build bone structure. Mentioned in: Rickets mineralization, n the bioprecipitation of an inorganic substance. in some fashion, these procedures are generally incapable of separating diseases with reduced volumetric mineralization (eg, osteoporosis osteoporosis (ŏs'tēō'pərō`sĭs), disorder in which the normal replenishment of old bone tissue is severely disrupted, resulting in weakened bones and increased risk of fracture; osteopenia ) from those that involve reduced specific mineralization (eg, osteomalacia osteomalacia /os·teo·ma·la·cia/ (os?te-o-mah-la´shah) inadequate or delayed mineralization of osteoid in mature cortical and spongy bone; it is the adult equivalent of rickets and accompanies that disorder in children. ).[20] Progress in clinical characterization of bone relies on developing means to clinically assess all of the important determinants of bone quality, specifically, the intrinsic material properties of a bone (stiffness and brittleness) versus the macroscopic macroscopic /mac·ro·scop·ic/ (mak?ro-skop´ik) gross (2). mac·ro·scop·ic or mac·ro·scop·i·cal adj. 1. Large enough to be perceived or examined by the unaided eye. 2. structural properties (eg, apparent mass density, structural shape and distribution of cortical cor·ti·cal adj. 1. Of, relating to, derived from, or consisting of cortex. 2. Of, relating to, associated with, or depending on the cerebral cortex. mass).[21] Conclusions The SEM and indexes derived from the SEM appear to be practical clinical measures for expressing the reliability of measurements of phase velocity of flexural waves. Sources of measurement error should be included as factors in the measurement design when studying the reliability of measurements obtained with the BSMD--Swing. Furthermore, the number of conditions for each factor should be large enough to attain stable estimates of variance components. To improve the SDDs, it is feasible to adapt the measurement design. For one operator to perform measurements, design 3 in Table 3 is the best approach because it results in a small SDD. The BSMD--Swing appears to be a promising device from clinical and research perspectives, although the reliability of its measurements has yet to be fully determined on subjects with osteoporosis after SCI. The device is noninvasive, nonradiological, and dependable in handling. It might present a means for the early diagnosis of osteoporosis in persons with SCI and for monitoring bone response to therapy on an individual basis. The device may also provide the means of detecting persons with SCI who are at risk for brittle bone breakage in time, so that preventive therapy can be started. Further research in clinical populations with the BSMD--Swing seem to be indicated. Acknowledgments We thank Josef Ehwald and Roland Herzog for carrying out the measurements and all of the subjects for participating in this study. We also thank Thomas Erni for his contribution to the data analysis. (*) Biomechanics The study of the anatomical principles of movement. Biomechanical applications on the computer employ stick modeling to analyze the movement of athletes as well as racing horses. Biomechanics Laboratory, Swiss Federal Institute of Technology The Swiss Federal Institute of Technology may refer to one of two institutes of higher education in Switzerland:
pl.n. 1. Geology Irregular dark or light streaks in plutonic igneous rock that differ in composition from the principal mass. 2. , Switzerland. ([dagger]) Kistler, PO Box 304, CH-8408 Winterthur, Switzerland. ([double dagger]) Inprise Corp, 100 Enterprise Way, Scotts Valley, CA 95066. References [1] Kanis JA, Devogelaer JP, Gennari C. Practical guide for the use of bone mineral measurements in the assessment of treatment of osteoporosis: a position paper of the European Foundation
[2] Consensus Development Conference report: diagnosis, prophylaxis prophylaxis (prō'fĭlăk`sĭs), measures designed to prevent the occurrence of disease or its dissemination. Some examples of prophylaxis are immunization against serious diseases such as smallpox or diphtheria; quarantine to confine , and treatment of osteoporosis. Am J Med. 1993;94:646-650. [3] Cheng S. Bone Mineral Density bone mineral density n. See bone density. bone mineral density A measurement of bone mass, expressed as the amount of mineral–in grams divided by the area scanned in cm2. See Bone densitometry. and Quality in Older People. Jyvaskyla, Finland: University of Jyvaskyla; 1994. PhD thesis. [4] Bischof H. Schallwellen in Langen Rohrenknochen: Eine Methode zur Bestimmung von Biegesteifigkeit und Maximaler Bruchkraft. Zurich, Switzerland: University of Zurich History The University of Zurich was founded in 1833 with existing colleges of theology (founded by Huldrych Zwingli in 1525), law and medicine merged together with a new faculty of Philosophy. ; 1993. PhD thesis. [5] Stussi E, Bischof HJ, Lucchinetti E, et al. Entwicklung und anpassung der biegesteifigkeit des extremitatenskelettes durch training am beispiel der tibia. Sportverletz Sportschaden. 1994;8:103-110. [6] Stussi E, Lawson R. The flight of a bone stiffness measurement device on EUROMIR 95 and future applications. Microgravity mi·cro·grav·i·ty n. 1. An environment in which there is very little net gravitational force, as of a free-falling object, an orbit, or interstellar space. 2. News. 1996;9(1);1-4. [7] Stussi E, Herzog R, Lawson R. Adaptation of tibia stiffness to low-gravity conditions (preliminary EUROMIR 95 report). Presented as an abstract at: Sixth European Symposium on Life Sciences Research in Space; June 16-20, 1996; Trondheim, Norway. [8] Rothstein JM. Measurement and clinical practice. In: Rothstein JM, ed. Measurement in Physical Therapy. New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of , NY: Churchill Livingstone Imprint of a medical publishing company owned by Elsevier Ltd, but previously owned by Harcourt and Pearsons. Originally formed from Livingstone, Edinburgh, Scotland, and J & A Churchill, London, UK, and subsequently with an office in New York, but now integrated with the rest of Inc; 1985:1-46. [9] Stratford PW. Reliability: consistency or differentiating among subjects? Phys Ther. 1989;69:299-300. Letter to the editor. [10] Roebroeck ME, Harlaar J, Lankhorst GJ. The application of generalizability theory to reliability assessment: an illustration using isometric isometric /iso·met·ric/ (-met´rik) maintaining, or pertaining to, the same measure of length; of equal dimensions. i·so·met·ric adj. 1. force measurements. Phys Ther. 1993;73:386-395. [11] Cronbach LJ, Gleser GC, Nanda H, Rajaratnam N. The Dependability of Behavioral Measurements: Theory of Generalizability for Scores and Profiles. New York, NY: John Wiley John Wiley may refer to:
[12] Shavelson RJ, Webb NM. Generalizability Theory: A Primer. Newbury Park, Calif: Sage Publications This article or section needs sources or references that appear in reliable, third-party publications. Alone, primary sources and sources affiliated with the subject of this article are not sufficient for an accurate encyclopedia article. Inc; 1991. [13] Anderson VL, McLean RA. Design of Experiments: A Realistic Approach. New York, NY: Marcel Dekker Marcel Dekker is a well-known encyclopedia publishing company with editorial boards found in New York, New York. They are part of the Taylor and Francis publishing group. Initially a textbook publisher, they went to encyclopedia publishing in the late 1990's. Inc; 1974. [14] Neter J, Wasserman W, Kutner MH. Applied Linear Statistical Models: Regression, Analysis of Variance, and Experimental Designs. 3rd ed. Boston, Mass: Irwin Inc; 1990. [15] Stussi E, Fah D. Assessment of bone mineral content by in vivo measurement of flexural wave velocities The speed at which a wave form advances across the sea, usually expressed in knots. See also wave. . Med Biol Eng Comput. 1988; 26:349-354. [16] Fah D, Stussi E. Phase velocity measurement of flexural waves in human tibia. J Biomech. 1988;21:975-983. [17] McNemar Q. Psychological Statistics. 3rd ed. New York, NY: John Wiley & Sons Inc; 1962:145-158. [18] Hartmann DP. Considerations in the choice of interobserver reliability estimates. J Appl Behav Anal. 1977;10:103-116. [19] Crick Crick , Francis Henry Compton 1916-2004. British biologist who with James D. Watson proposed a spiral model, the double helix, for the molecular structure of DNA. He shared a 1962 Nobel Prize for advances in the study of genetics. JE, Brennan RL. Manual for GENOVA: A General Purpose Analysis of Variance System. Iowa City, Iowa Iowa City is a city in Johnson County, Iowa, United States. It is the principal city of the Iowa City, Iowa Metropolitan Statistical Area which encompasses Johnson and Washington counties. : American College American College is the name of:
[20] Martin RB, Burr burr (bur) bur. burr n. Variant of bur. burr 1. a plant seed capsule carrying many hooked structures which catch in animal coats thus promoting dissemination of the plant. DB. Structure, Function, and Adaptation of Compact Bone. New York, NY: Raven raven, common name for the largest member of the family Corvidae (crow family), ranging throughout the arctic and temperate regions of the Northern Hemisphere. The raven, Corvus corax, is a glossy black scavenging bird about 26 in. Press; 1989. [21] Brandenburger GH. Clinical determination of bone quality: Is ultrasound an answer? Calcif Tissue Int. 1993;53 (suppl 1) :S151-S156. ED de Bruin, PT, is Research Scientist, Biomechanics Laboratory Swiss Federal Institute of Technology Zurich, Wagistrasse 4, CH-8952 Schlieren, Switzerland (debruin@biomech.mat.ethz.ch), and Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam (education, body) Vrije Universiteit, Amsterdam - The "Free University of Amsterdam", founded in 1880 by Abraham Kuyper (who later became Prime Minister of The Netherlands). Originally only open to Reformed Christians, it is now open to all. , the Netherlands. Address all correspondence to Mr de Bruin at the first address. RH Rozendal, MD, PhD, Professor, Faculty of Human Movement Sciences, Vrije Universiteit The language of instruction for the bachelors courses is Dutch. However, many of the masters programmes are given entirely in English in order to attract students from outside The Netherlands. . E Stussi, PhD, is Professor, Biomechanics Laboratory, Swiss Federal Institute of Technology Zurich. This study was approved by the Review Committee of Swiss Federal Institute of Technology Zurich and Balgrist University Hospital, Zurich, Switzerland. This article was submitted July 28, 1997, and was accepted May 19, 1998. |
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