Automated measurement of proprioception following stroke

Background.?Proprioception provides feedback which is essential for adequate motor control. Despite having detrimental functional implications, the assessment of proprioception deficits in current clinical practice is mostly qualitative and inadequate for diagnosis and longitudinal monitoring of subtle impairments and their effect on motor function.

Purpose.?To evaluate a novel quantitative approach to the assessment of proprioception deficits in stroke patients.

Method.?We designed and implemented an automated protocol where a magnetic motion tracking system and a sensor attached to each of the patient's hands, enables registration of trajectories in 3D coordinates. In this protocol the patient's affected and healthy hands are placed respectively below and above a square board. With vision blocked, the subject's affected hand is passively moved to one of four locations, and then the patient is instructed to actively position the healthy hand directly above his/her perceived location of the affected hand. The positional difference between the two hands is automatically recorded by the system. This procedure is repeated several times and the magnitude and direction of errors are used to quantify the proprioception deficit. The data for this pilot study was collected in a sample of 22 stroke patients and an age-matched group of neurologically intact subjects.

Results.?Stroke patients had significantly higher mean distance error compared with the control group (average values of 7.9 and 5.3 cm, respectively), and showed higher instability (variance) in repeated performance (average values of the standard deviation of errors 3.4 and 1.8 cm, respectively). Significant correlation was found between the mean distance error and the results of semi-quantitative clinical tests of proprioception.

Conclusion.?The system provides a reliable quantitative measure of upper limb proprioception, offering considerable advantage over the traditional means applied in the clinic.     

Kinesthetic perceptions of earth- and body- fixed axes

 The major purpose of this research was to determine whether kinesthetic/proprioceptive perceptions of the earth-fixed vertical axis are more accurate than perceptions of intrinsic axes. In one experiment, accuracy of alignment of the forearm to earth-fixed vertical and head- and trunk-longitudinal axes by seven blindfolded subjects was compared in four tasks: (1) Earth-Arm – arm (humerus) orientation was manipulated by the experimenter; subjects aligned the forearm parallel to the vertical axis, which was also aligned with the head and trunk longitudinal axis; (2) Head – head, trunk, and upper-limb orientations were manipulated by the experimenter, subjects aligned the forearm parallel to the longitudinal axis of the head using only elbow flexion/extension and shoulder internal/external rotation; (3) Trunk – same as (2), except that subjects aligned the forearm parallel to the trunk-longitudinal axis; (4) Earth – same as (2), except that subjects aligned the forearm parallel to the earth-fixed vertical. Head, trunk, and gravitational axes were never parallel in tasks 2, 3, and 4 so that subjects could not simultaneously match their forearm to all three axes. The results showed that the errors for alignment of the forearm with the earth-fixed vertical were lower than for the trunk- and head-longitudinal axes. Furthermore, errors in the Earth condition were less dependent on alterations of the head and trunk orientation than in the Head and Trunk conditions. These data strongly suggest that the earth-fixed vertical is used as one axis for the kinesthetic sensory coordinate system that specifies upper-limb orientation at the perceptual level. We also examined the effects of varying gravitational torques at the elbow and shoulder on the accuracy of forearm alignment to earth-fixed axes. Adding a 450 g load to the forearm to increase gravitational torques when the forearm is not vertical did not improve the accuracy of forearm alignment with the vertical. Furthermore, adding small, variably sized loads (between which the subjects could not distinguish at the perceptual level) to the forearm just proximal to the wrist produced similar errors in aligning the forearm with the vertical and horizontal. Forearm-positioning errors were not correlated with the size of the load, as would be expected if gravitational torques affected forearm-position sense. We conclude that gravitational torques exerted about the shoulder and elbow do not make significant contributions to sensing forearm-orientation relative to earth-fixed axes when the upper-limb segments are not constrained by external supports. Received: 26 March 1998 / Accepted: 21 December 1998     

Weight estimation in a "deafferented" man and in control subjects: are judgements influenced by peripheral or central signals?

It is not yet certain which sources of information are most important in judging the weight of a held object. In order to study this question further, a "deafferented" man and five controls flexed their wrist to lift a container weighing 1,000 g. Direct vision of the arm and weight was denied; the container's vertical position was displayed to the subjects on an oscilloscope at the start of each trial and, then, in most experimental conditions, this display was removed. The weight was then either gradually increased or decreased over 20 s or left unchanged, on a pseudorandom basis. A verbal judgement of its change was required at the end of each trial, lasting 20 or 40 s. Under these conditions, the "deafferented" subject was unable to correctly judge the weight changes (38% accuracy, n.s. chi2, compared with 77% in control subjects), and even the control subjects, when exposed to muscle vibration, made many errors (54% accuracy). However, in many trials, including those in which the weight was unchanged, the vertical height of the container was not held constant by the subjects, but drifted up or down (mean absolute drift: approximately 2 cm). Hence, the change in muscular activation or stiffness could be estimated by the observers in the majority of trials. This allowed the verbal judgements of both the "deafferented" man and of control subjects undergoing muscle vibration to be correlated with the muscle activation produced, independent of the actual weight being tested. Post-hoc predictions of controls' responses during vibration, based on the direction of the change in muscle activity which these drifts in position implied, were 77% and 66% accurate for +/-750 g and +/-375 g tasks and 73% accurate for forearm-vibration trials (P<0.0001, chi2). Predictions of the "deafferented" subject's responses were 64% accurate (P=0.0002, chi2), even though his own responses were at a chance level with respect to the actual weight change. The judgements made by these subjects might have been based upon a peripheral sensory input, as small afferent fibres are still present in the "deafferented" man and vibration only partly blocked sensory function in the control subjects. Care was taken to minimise all other possible cues to the weight changes, e.g. vestibular, thermal, pressure or pain cues. However, peripheral inputs may not be the only signals used in the subjects' perceptual judgements. They might, instead, be based upon a centrally originating, but illusory changing sense of body position or, possibly, a changing sense of effort. In both cases, a perceived discordance between voluntary muscle activation and body image could underlie the subjects' responses. Our data do not yet allow us to distinguish between these alternative peripheral and central hypotheses, but do highlight the need to include perceptions of body position and motion into judgements of force control.     

Nonspecific velocity and amplitude hunting reveals different specific detection performance of flexion and extension movements in the human knee joint

A debate exists in the literature as to what extent perception is conscious. In some publications regarding proprioception, the term proprioception has explicitly only been seen as properly used when subjects were able to report the imposed movement's direction. Detections of movements without movement-direction perception, have been seen as nonspecific. Since a lot of studies discussed this point but never tested it explicitly, we tested it by using nonspecific hunting paradigms (only the occurrence of a movement has to be detected, not its direction) with the following rationale. If the perception performance is really nonspecific, no difference regarding the movement's direction should be found. Thus, if we found a different detection performance regarding flexion and extension by means of a nonspecific paradigm, it would demonstrate that this "nonspecific" perception is already specific. Therefore, we measured the perception characteristics separately for flexion and extension. The perception characteristics have been determined from the amplitude-velocity-relation curve. Two different, nonspecific hunting paradigms, modifications of our previously published specific hunting paradigm, have been used. Thus, we determined pairs of threshold values, regarding amplitude hunting using three different angular velocities (0.1 degrees s(-1), 0.25 degrees s(-1), and 0.5 degrees s(-1)) and regarding velocity hunting using three different angular displacements (0.25 degrees, 0.5 degrees, and 1 degrees) as well, for flexion and extension, respectively. We found that both threshold paradigms (velocity hunting and amplitude hunting) revealed the same perception characteristics for a given movement direction. With an increasing angular velocity, angular displacement threshold values converged toward a common value for flexion and extension (about 0.2 degrees); with an increasing angular displacement, angular velocity threshold values converged toward separate values for flexion (about 0.06 degrees s(-1)) and extension (about 0.1 degrees s(-1)). Thus, our findings demonstrate that detection performance is specific and not bound to conscious perception, since specific thresholds for flexion and extension were revealed with nonspecific hunting paradigms.     

Proprioceptive abilities in patients with conservative and surgical treatment of ACL tears

Summary In the present study we evaluated proprioceptive capabilities of the knee joint with a balance test and correlated these findings to parameters which document mechanical stability. We compared 8 conservatively treated and 12 surgically treated patients with ACL-deficient knee joints with a control group of 12 subjects. The balance test was performed with a Kistler force plate. Both the conservatively treated and the surgically treated patients showed significantly higher deviations of their centre of gravity than the control group. This was true not only for the injured leg but also for the noninjured contralateral leg. The differences were most remarkable when comparing the entire distance of centre of gravity deviations during 10 s. Additionally, the conservatively treated patients interrupted the test procedure significantly more frequently than the other two groups. We were not able to document any correlation between proprioceptive function and parameters for joint stability such as anterior drawer, Lachman, pivot shift and KT-1000 measurements. Clinical significance: In patients with conservatively or surgically treated ACL tears the rehabilitation of proprioceptive capabilities is mandatory both for the injured leg and for the noninjured contralateral leg in order to restore the function of the lower extremities. Reconstruction of passive stability alone is not sufficient.      

Effects of short-term cycling on knee joint proprioception in ACL-deficient patients

It has previously been shown that knee injuries with ACL ruptures may lead to decreased proprioception and that exercise in a normal population, uninjured individuals, may reduce the proprioceptive ability. How proprioception is affected by exercise in patients with ACL deficiency has, to our knowledge, not been studied before. Knee joint proprioception was estimated in 36 patients, 18 males and 18 females, with ACL deficiency by measuring thresholds for detection of slow passive motion before and after a short period of exercise on an ergometer bicycle. In addition, the results were compared with a control group of 24 individuals of the same age. We found trends of enhanced proprioception towards extension in the patient group after cycling, but not in the control group. Towards flexion, both groups showed poorer proprioception after cycling. When difference scores of proprioceptive change in each group were compared, a trend towards different reaction upon cycling between the groups was seen in measurement towards extension from 20° where the patients seemed to improve proprioception, which the controls did not. The results are not conclusive in this pilot study, but the possibility that ACL-deficient patients and controls may not react likewise to cycling, as regards their proprioceptive ability, is discussed.     

Cryotherapy does not impair shoulder joint position sense

OBJECTIVE: To determine the effects of a cryotherapy treatment on shoulder proprioception. DESIGN: Crossover design with repeated measures. SETTING: University athletic training and sports medicine research laboratory. PARTICIPANTS: Thirty healthy subjects (15 women, 15 men). INTERVENTION: A 30-minute cryotherapy treatment. MAIN OUTCOME MEASURES: Joint position sense was measured in the dominant shoulder by using an inclinometer before and after receiving 30 minutes of either no ice or a 1-kg ice bag application. Skin temperature was measured below the tip of the acromion process and recorded every 5 minutes for the entire 30 minutes and immediately after testing. Three different types of error scores were calculated for data analyses and used to determine proprioception. RESULTS: Separate analyses of absolute, constant, and variable error failed to identify changes in shoulder joint proprioception as a function of the cryotherapy application. CONCLUSIONS: Application of an ice bag to the shoulder does not impair joint position sense. The control of proprioception at the shoulder may be more complex than at other joints in the body. Clinical implications may involve modifying rehabilitation considerations when managing shoulder injuries.     

Obstacle avoidance during human walking: effects of biomechanical constraints on performance

OBJECTIVE: To determine whether fixation of the ankle joint, the knee joint, or both increasingly affects the performance of a newly learned task, that is, stepping over an obstacle. DESIGN: Randomized trial. SETTING: Research laboratory of a university hospital in Switzerland. PARTICIPANTS: Eighteen healthy, young volunteers. INTERVENTION: Subjects walked on a treadmill and, with reduced vision, stepped with the right leg over a randomly approaching obstacle. They adapted to the task during the 2 runs. In the third run, fixating orthoses of the ankle-foot (AFO), knee (KO), or both (KAFO) were attached to the left leg. MAIN OUTCOME MEASURE: The "performance" consisted of leg muscle activity, joint movements, swing phase duration, and the clearance between the foot and the obstacle. The changes within runs (adaptation) and between runs (eg, transfer) were evaluated. RESULTS: The attached orthoses caused a reduced transfer of performance in the KAFO and KO between runs 2 and 3. No differences in the rate of adaptation were observed among the 3 groups during the third run. CONCLUSIONS: A movement restriction of the supporting leg worsened the performance of the contralateral leg in a locomotor task. Performance was more affected by knee-joint fixation than by ankle-joint fixation alone and, consequently, the need for relearning is greater.     

A long-lasting improvement of somatosensory function after prism adaptation, a case study

Previous studies have observed a reduction of visual and representational neglect symptoms after visuo-manual adaptation to rightward displacing prisms. Recently, improvements have also been observed on somatosensory tasks, such as locating the centre of a haptically explored circle and tactile double simultaneous stimulation. In the current single case study we assessed whether prism adaptation with the ipsilesional hand improved two aspects of contralesional somatosensory function, pressure sensitivity and proprioception. After the first application of prism adaptation improvements in pressure sensitivity and proprioception were observed. A second prism adaptation confirmed the improvements in contralesional somatosensory function. The effects of prism adaptation on position sense were longer lasting than have been reported previously, but consistent with reductions of visual neglect symptoms after prism adaptation. The current findings suggest that prism adaptation can have a non-spatial effect on neglect-related supra-modal deficits.     

The effect of a simulated knee joint effusion on postural control in healthy subjects

OBJECTIVE: To determine the effects of a simulated knee joint effusion on center of pressure (COP) path and mean power frequency (MPF) during standing. DESIGN: Quasi-experimental design. SETTING: Sports injury research laboratory in a university setting. PARTICIPANTS: Twenty healthy volunteers, 10 of whom (age, 20.1+/-2.4y; height, 168.0+/-8.1cm; weight, 70.4+/-13.3kg) were assigned to an effusion group and 10 of whom (age, 25+/-3.8y; height, 169.4+/-8.9cm; weight, 74.7+/-7.7kg) were assigned to a control group. INTERVENTIONS: COP data were collected before and after a 60-mL injection of sterile saline into the knee joint space.Main Outcome Measures: COP path and mediolateral and anteroposterior MPF. RESULTS: COP path decreased after the effusion (pre-effusion mean, 92.2+/-21.9cm; posteffusion mean, 77.27+/-23.0cm). No change was found within the control group for COP path (P>.05). No differences were detected before or after joint effusion when the MPF was examined (P>.05). CONCLUSIONS: Possible explanations for the improved postural control after the effusion include additional somatosensory feedback, an augmented neural drive to the soleus, and/or increased capsular tension.