Observations on the measurement of joint stiffness

What is the minimum torque required to obtain passive elbow end range of motion?

BACKGROUND

Passive range of motion is a common clinical assessment. The point at which passive end range of motion is measured is typically described by the 'end-feel'of the joint.

RESEARCH QUESTION

What is the minimum amount of torque required to obtain passive elbow flexion and extension in children?

METHODS

Twenty-five children (age, 7.5 ± 1.6 years-old), who had previously sustained unilateral distal humeral fractures, participated in this prospective study.Passive elbow flexion and extension was measured at least 8 weeks and up to one year out of cast. Motion capture cameras were used to track twenty-one reflective markers placed on subjects and two markers attached to the pad of a force transducer.Five trials of passive range of motion (flexion and extension) were performed on both arms. Elbow joint moments were calculated as products of the forces applied and lengths to the elbow centers. A one way ANOVA was used to determine differences in moments for flexion and extension for both involved and uninvolved limbs. Pairedsamples t-tests were used to determine differences between the involved and the uninvolved limbs for both maximum flexion and extension.

RESULTS

There was no difference in the minimum mean joint moment (2.7 ± 1.1 Nm) at end range of motion. However, differences in passive range of motion was found between involved and uninvolved elbows (flexion p < .001; extension p = .001).

SIGNIFICANCE

The results demonstrate therapists obtained end range of passive elbow flexion and extension applying the same amount of minimum torque. A small torque is sufficient to achieve end range of elbow motion for children. This torque can be used in guiding clinical practice for assessing passive range of elbow motion in pediatric population. Because of a paucity of data for any joint, future research developing force data for other joints should be conducted.

Investigating Dimensions of Stiffness in Rheumatoid and Psoriatic Arthritis: The Australian Rheumatology Association Database Registry and OMERACT Collaboration

OBJECTIVE

It is not known how the experience of stiffness varies between diagnoses or how best to measure stiffness. The aims of our study were to (1) compare stiffness in psoriatic arthritis (PsA) and rheumatoid arthritis (RA) using patient-reported outcomes, (2) investigate how dimensions of stiffness are associated with each other and reflect the patient experience, and (3) analyze how different dimensions of stiffness are associated with physical function.

METHODS

An online survey was sent to Australian Rheumatology Association Database participants (158 PsA, and 158 age- and sex-matched RA), assessing stiffness severity, duration, impact, importance, coping, and physical function [modified Health Assessment Questionnaire (mHAQ)]. Scores were compared between diagnoses and correlations among stiffness dimensions calculated. Multivariate regression was performed for stiffness severity, impact, and duration on mHAQ, adjusting for age, sex, disease duration, obesity, and pain. Cognitive debriefing was conducted through semistructured telephone interviews.

RESULTS

Overall, 240/316 (75.9%) responded [124/158 RA (78.5%) and 116/158 PsA (73.4%)], with no significant difference in stiffness ratings between diagnoses. Scores for all stiffness dimensions were strongly correlated (r = 0.52-0.89), and severity and impact were associated with mHAQ in both diagnoses. Stiffness duration was not associated with mHAQ in RA. In cognitive debriefing, participants described stiffness severity and impact by their effect on daily activities (10/16 and 14/16 participants, respectively).

CONCLUSION

Stiffness ratings were similar between PsA and RA. Different dimensions of stiffness were strongly correlated. Stiffness severity and impact both independently predicted mHAQ. Stiffness was important to participants; however, measuring multiple dimensions of stiffness may have minimal additive value.

Changes in contractile and elastic properties of the triceps surae muscle induced by neuromuscular electrical stimulation training

PURPOSE

Neuromuscular electrical stimulation (NMES) training is known to induce improvement in force production capacities and fibre-type transition. The aim of this study was to determine whether NMES training also leads to changes in the mechanical properties of the human triceps surae (TS) muscle.

METHODS

Fifteen young male subjects performed a training protocol (4 weeks, 18 sessions, 4-5 sessions per week) based on a high-frequency isometric NMES programme of TS muscle. Quick-release test was used to evaluate Musculo-Tendinous (MT) stiffness index (SIMT) as the slope of the linear MT stiffness-torque relationships under submaximal contraction. Sinusoidal perturbations allowed the assessment of musculo-articular stiffness index (SIMA) as well as the calculation of the maximal angular velocity ([Formula: see text]) of TS muscle using an adaptation of Hill's equation.

RESULTS

After NMES training, Maximal Voluntary Contraction under isometric conditions and [Formula: see text] increased significantly by 17.5 and 20.6 %, respectively, while SIMT and SIMA decreased significantly (-12.7 and -9.3 %, respectively).

CONCLUSIONS

These changes in contractile and elastic properties may lead to functional changes of particular interest in sport-related activities as well as in the elderly.

Stretch reflexes and joint dynamics in rheumatoid arthritis

In clinically diagnosed rheumatoid arthritis (RA), studies were conducted to investigate the reflex and passive tissue contribution to measured increases in joint stiffness in the resting upper limb and during constant contractions of an attached muscle. The tonic stretch reflex was induced by a servo-controlled sinusoidal stretch perturbation of the metacarpophalangeal joint of RA patients, and age- and sex-matched controls. The resulting reflexes and mechanical changes in the RA affected joint were explored. Surface electromyographic (EMG) measurements were obtained from first dorsal interosseus muscle. Reflex gain (EMG/joint angle amplitude ratio), phase difference (reflex delay after stretch), coherence square (proportion of EMG variance accounted for by joint angle changes), joint mechanical gain (torque-joint angle amplitude ratio) and mechanical phase difference (torque response delay after stretch) were determined. RA patients showed decreased reflex gain that was partly due to coexistent severe muscle weakness, as determined from maximum voluntary contraction and grip pressure estimates. The decreased reflex gain was most evident at high stretch frequency suggesting a disproportionate loss of the large diameter afferent response and also increased reflex delay in the patients. These changes ensemble suggest significant loss of neural drive to the motor unit population. Patients also showed increased joint stiffness (measured as torque gain) in the contracting muscle, but there was no evidence of reflex activity or increased stiffness at rest. This suggests that the increased joint stiffness in RA was due to changes in the mechanical properties of the active muscle-joint system rather than changes in reflex properties.

A robot-assisted study of intrinsic muscle regulation on proximal interphalangeal joint stiffness by varying metacarpophalangeal joint position

The tightness of intrinsic hand muscles is a common cause of finger joint stiffness. The purposes of this study were to develop a robot-assisted methodology to obtain torque-angle data of a finger joint, and to investigate the regulation of the intrinsic muscles on finger joint stiffness. Our robot system features the integration of a low payload robot arm, a controller, and a force/torque transducer. The system provided highly reproducible torque-angle curves. Torque-angle data of the proximal interphalangeal joint with the metacarpophalangeal joint at 0 and 60 degrees were obtained from eight asymptomatic hands. The torque-angle curve shifted with the position of the metacarpophalangeal joint. As the metacarpophalangeal joint flexion angle changed from 60 to 0 degrees, the equilibrium of the proximal interphalangeal joint increased more than 20 degrees, and joint stiffness increased more than 50%. The dependence of the stiffness of the proximal interphalangeal joint on metacarpophalangeal joint position supports the regulatory role of the intrinsic muscles on finger joint mechanics. This regulatory mechanics is likely amplified in hands with intrinsic muscle tightness, justifying the commonly used Bunnell Intrinsic Tightness Test.

Proximal interphalangeal joint stiffness: measurement and analysis

PURPOSE

The purpose of this study was to quantify the stiffness of the human finger proximal interphalangeal (PIP) joint and to study its relationship to different common clinical parameters.

METHODS

Eighty-nine normal adult subjects had their PIP joints of the index, middle, and ring fingers evaluated using a computer-controlled moment-angle plotter. This device was used to measure stiffness and energy absorbed at the PIP joint during passive flexion and extension.

RESULTS

The average overall stiffness was 0.05 N-cm/degree. There was a weak correlation between stiffness and energy absorbed and the size of the finger: they both increased with the size of the finger. The men's fingers were stiffer and absorbed more energy than the corresponding women's fingers. No significant associations were found between the time of day when the test took place, occupation, hobbies, or age with stiffness or absorbed energy. No significant differences were associated with hand dominance. The finger on the dominant hand had a larger circumference for both genders. Heavier individuals had more stiffness and absorbed more energy than lighter individuals.

CONCLUSIONS

The PIP joint stiffness was defined quantitatively and measured over a wide cross-section of a normal population. This may allow future studies to record the outcome of different treatments for finger joint stiffness objectively. The stiffness was greater in men and in larger fingers.

Manual discrimination capability when only viscosity is varied in viscoelastic stiffness stimuli

BACKGROUND

Training manual therapists in the judgment of spinal stiffness traditionally requires the spines of human volunteers. Presenting the range of stiffness values representative of spines requires both time and resources. When investigating the ability of therapists to judge spinal stiffness, several studies have therefore utilized spine analogues, nonbiological devices designed to present either purely elastic stimuli or viscoelastic stimuli with unknown relative contributions of elastic and viscous components. Previous research has suggested that the viscous component of stiffness is more difficult to judge.

OBJECTIVE

This study determined for each subject the just-noticeable difference, or discrimination threshold, for manual judgment of viscous stiffness against a constant elastic and friction background.

DESIGN

This psychophysical study utilized the Weber fraction as a measure of the ability of subjects to discriminate between viscoelastic stiffness stimuli.

METHODS

Twenty-five subjects with both physiotherapy and lay backgrounds volunteered to participate in the study. Stiffness stimuli were generated by a device incorporating a fluid-filled plunger and a spring, with only the amount of viscous stiffness being manipulated by the experimenter. The method of constant stimuli was used to estimate the just-discriminable change in viscous stiffness, and results were expressed as a percentage of the base stiffness or Weber fraction.

RESULTS

The mean Weber fraction for manual judgments of viscous stiffness was 14.7%. For 13 of the subjects who had previously participated in elastic stiffness discrimination studies, the Weber fraction for viscous stimuli was significantly greater than that for elastic stimuli.

CONCLUSION

The significantly higher Weber fraction for viscous stiffness perception compared with that for pure elastic stiffness suggests that the poor reliability of manual judgments of spinal stiffness may be due to the difficulty in judging the viscous stiffness component.

Influence of leg stiffness and its effect on myodynamic jumping performance

The purposes of this study are: a) to examine the possibility of influencing the leg stiffness through instructions given to the subjects and b) to determine the effect of the leg stiffness on the mechanical power and take-off velocity during the drop jumps. A total of 15 athletes performed a series of drop jumps from heights of 20, 40 and 60 cm. The instructions given to the subjects were a) "jump as high as you can" and b) "jump high a little faster than your previous jump". The jumps were performed at each height until the athlete could not achieve a shorter ground contact time. The ground reaction forces were measured using a "Kistler" force plate (1000 Hz). The athletes body positions were recorded using a high speed (250 Hz) video camera. EMG was used to measure muscle activity in five leg muscles. The data was divided into 5 groups where group 1 was made up of the longest ground contact times of each athlete and group 5 the shortest. The leg and ankle stiffness values were higher when the contact times were shorter. This means that by influencing contact time through verbal instructions it is possible to control leg stiffness. Maximum center of mass take-off velocity the can be achieved with different levels of leg stiffness. The mechanical power acting on the human body during the positive phase of the drop jumps had the highest values in group 3. This means that there is an optimum stiffness value for the lower extremities to maximize mechanical power.

Reliability of torque range of motion: a preliminary study

The clinical reliability of torque range of motion (TROM) has not been tested. This preliminary review was performed to determine the intra- and interrater reliability of TROM. The proximal interphalangeal joints of the index and middle fingers of 14 normal subjects, 56 digits, were tested by applying extension forces of 200 g, 400 g, 600 g, and 800 g. Data were collected using both the hand-held Haldex orthotic gauge with the dial goniometer (manual) and the cantilever-beam force transducer and electrogoniometer (digital) as testing instruments. The testing order of digits, sides, and devices was randomized and tested separately by three different test teams. Results of the analysis of variance showed a significant difference of the means between raters at all force levels (p < 0.0001) and between instruments at 600-g and 800-g forces (p < 0.01). The Pearson product-moment correlation coefficient test, used to test the consistency, resulted in moderate consistency of measures of intrarater reliability between trials, and between instruments used (digital and manual). Intraclass correlation coefficients (ICCs) were calculated with results that were nearly identical to those of the Pearson. Intrarater reliability was in more consistent agreement at the 600-g and 800-g levels. There was significantly high agreement between the tests of tester B, compared with moderate correlations of the tests of testers A and C.

Flexibility of the shoulder joint measured as range of abduction in a large representative sample of men and women over 65 years of age

In a representative survey of 1000 elderly men and women aged over 65 years living in their own homes, assessments have been made of flexibility measured as range of shoulder abduction in addition to health status, psychological well-being and reported customary activity. The results for shoulder abduction were approximately normally distributed and the mean values (+/- 1 standard deviation) were as follows: - in men aged 65-74 years, 129 (+/- 14) degrees and aged over 74 years, 121 (+/- 19) degrees; in women aged 65-74 years, 124 (+/- 19) degrees and aged over 74 years, 114 (+/- 22) degrees. These mean values are about 30 degrees less than those accepted for younger subjects. Nearly half the distribution falls below the accepted threshold level of 120 degrees for adequate function. There were significant effects of sex and age (P less than 0.001); women had poorer flexibility and the reduction with age amounted to 10 degrees per decade. Multiple regression analysis showed that the effect of age was accounted for in part by health, strength and customary use. The effects of use were most marked in those with some disability. This suggests that maintained or increased use could offset some of the age-related loss of the range of shoulder movement.

Circulating hyaluronic acid levels vary with physical activity in healthy subjects and in rheumatoid arthritis patients. Relationship to synovitis mass and morning stiffness

We evaluated the possible influence of physical activity on serum levels of hyaluronic acid (HA), plasma levels of elastase, and serum levels of procollagen III peptide. In 15 healthy individuals, HA increased from 26 +/- 9 micrograms/liter (mean +/- SD) before arising from a night's sleep to 54 +/- 24 micrograms/liter 1 hour after arising and performance of normal morning activities (P less than 0.001). HA in 14 patients who had inflammatory arthritis increased from 124 +/- 104 micrograms/liter to 402 +/- 232 micrograms/liter under the same conditions (P less than 0.001). The elevation due to physical activity was significantly (P less than 0.001) higher in patients with rheumatoid arthritis (RA) than that found in controls. A slight increase of HA in the afternoon was also observed in healthy subjects who performed heavy exercise, but a marked increase was seen in RA patients who performed moderate exercise. In another group of 24 RA patients, a more standardized blood sampling was performed before arising and during normal morning activities. An increase in HA was significantly (P less than 0.001) correlated to the synovitis mass, estimated by the Ritchie articular index. Maximum increases of HA were seen 30 and 60 minutes after arising; thereafter, levels decreased to those measured at rest. During the morning activities, procollagen III peptide remained stable, while plasma elastase tended to increase. It is proposed that HA, produced in the joint tissue structures and accumulated at rest, is carried by the lymph vessels to the general circulation during physical activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of outcome in rheumatic diseases

In the assessment of outcome in rheumatic diseases a number of factors must be taken into account. It is important to make an accurate diagnosis, so that the response to treatment is not confused by heterogeneity of the population. The meaning of outcome needs to be defined. The quality of life over a prolonged period is just as important as the ultimate outcome. Subjective symptoms are important to the patient. Pain is the most important, followed by disability and then stiffness. Despite attempts to produce numerical values for pain, particularly visual analogue scales, patients' accuracy in recalling pain experienced more than an hour previously is dubious. In an attempt to quantify this aspect we have measured disturbance of sleep by changes in the EEG and in the motility of the patient. Objective clinical measures are desirable for accuracy. Arthrographs of the knees and metacarpophalangeal joints have produced useful data for physical stiffness. It is doubtful, however, whether they truly reflect the subjective stiffness of which the patient complains. That is more likely to be due to limitation of motion. Grip strength is commonly measured by a pneumatic dynomometer, but a pinch/hand grip analyser promises to give more extensive information. Active movement has been measured goniometrically. The value of electrogoniometers should be enhanced by telemeterization of the apparatus. Passive movement has been measured with a hyperextensometer in patients with hypermobility. Ligamentous laxity of the knee can be measured on the Leeds Knee Analyser and differentiates collateral ligament damage and anterior cruciate ligament damage. Laboratory variables are important in a patient model system in which potential antirheumatoid drugs can be screened and their mechanism of action investigated. Correlation matrices separate second-line agents from NSAIDs. Although mini-matrices have been produced, it would not appear that any single biochemical test will suffice to differentiate these two classes of drugs. A therapeutic index, in which the efficacy is expressed as a ratio of the toxicity of the drug, is important in determining its value. The nearest we can get to serial assessment of the pathological changes in the joint is by X-ray assessment. Changes radiologically correlate to some extent with the height of the ESR, and their progress with changes in the ESR. Functional impairment is important to the patient in the long term, and the Disability Index devised by the Stanford group commends itself for extensive long-term studies.

Microprocessor controlled arthrograph

This new arthrograph, based on a microcomputer, provides displacements of variable amplitude, frequency and waveform. It is sufficiently small for use on a ward or in a clinic, is simple to use and is readily accepted by patients. One test and its associated analysis, together with printed and plotted results, occupies little more than two minutes.

The passive elastic moment at the hip

The passive elastic moment at the hip was measured in normal male subjects in situ. The influence of two joint muscles crossing the hip was evaluated by performing hip moment measurements over a continuous range of hip angles and at prescribed knee angles. The experimentally acquired data was fitted by exponential functions which separately modeled the moment contribution of tissues deformed by hip flexion and extension. The results of the investigation are discussed with regard to the possible role of the passive joint moments as an energy storage and release mechanism during human walking.

An apparatus and a method for measuring the relationship of triceps surae torques to tibio-tarsal angles in man

1. The apparatus and method described give the relationship of triceps surae torque to the absolute tibio-tarsal angle. Data of the anatomy of the foot and the axis of the ankle are taken into consideration. They make complementary measurements necessary, which in certain cases enable the angle recorded by the apparatus to be corrected so as to obtain the true angle. 2. The reliability of the apparatus and the technique of linkage of subject to apparatus are judged by examination of the torque-angle plots obtained by passive stretching of the triceps in 7 subjects for whom correction is monor. Good reliability was observed during the session and from one session to another. The plot is exponential. The merits of the method of correcting angles are illustrated in three subjects with the same protocol: when plots are not corrected, they are more dispersed during the session and no longer exponential. These results justify the considerable correction of the angle that we propose in the study of isometric contractions.