1. Manual Setup. The simple method for registering preset codes of Denon players, and the method for registering the preset numbers of other manufacturers’ devices. (5 digits) listed for the device in the Preset Code Table using the number buttons (0 – 9) on the remote control. Some manufacturers use more than one.
2. 130: Denon AVR not properly configured? (4.88) Posted by 4season on 2013-11-16, 20:57:26 (174.29.202.48) I'll bet your Denon is currently configured to direct most of the bass frequencies to a subwoofer which isn't there. Either add a sub else reconfigure your receiver so it treats your Tannoys as full-r.

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Background. Mirror therapy (MT) and mesh glove (MG) afferent stimulation may be effective in reducing motor impairment after stroke. A hybrid intervention of MT combined with MG (MT + MG) may broaden aspects of treatment benefits. Objective. To demonstrate the comparative effects of MG + MT, MT, and a control treatment (CT) on the outcomes of motor impairments, manual dexterity, ambulation function, motor control, and daily function. Methods. Forty-three chronic stroke patients with mild to moderate upper extremity impairment were randomly assigned to receive MT + MG, MT, or CT for 1.5 hours/day, 5 days/week for 4 weeks. Outcome measures were the Fugl-Meyer Assessment (FMA) and muscle tone measured by Myoton-3 for motor impairment and the Box and Block Test (BBT) and 10-Meter Walk Test (10 MWT) for motor function. Secondary outcomes included kinematic parameters for motor control and the Motor Activity Log and ABILHAND Questionnaire for daily function. Results. FMA total scores were significantly higher and synergistic shoulder abduction during reach was less in the MT + MG and MT groups compared with the CT group. Performance on the BBT and the 10 MWT (velocity and stride length in self-paced task and velocity in as-quickly-as-possible task) were improved after MT + MG compared with MT. Conclusions. MT + MG improved manual dexterity and ambulation. MT + MG and MT reduced motor impairment and synergistic shoulder abduction more than CT. Future studies may integrate functional task practice into treatments to enhance functional outcomes in patients with various levels of motor severity. The long-term effects of MG + MT remain to be evaluated.

Stroke has become the most frequent cause of adult-onset disability and costs a tremendous amount of related care expense.¹ About 65% of people after stroke experience difficulty in incorporating the affected hand into activities.¹ Several novel and theory-based rehabilitation interventions have been developed to improve motor recovery of the upper extremity (UE).² Among novel interventions, mirror therapy (MT) was beneficial and comparatively low cost.²

Substantial evidence showed that MT reduced UE motor impairment, as measured by the Fugl-Meyer Assessment (FMA). Reduced impairments might result from recruiting the premotor cortex or balancing neural activation within the primary motor cortex toward the affected hemisphere.^2-4 The benefits in certain aspects of outcomes are inconclusive, however; for instance, Cacchio et al⁵ found MT improved hand function, but others² reported no significant effect. Results of research on the effects of MT on spasticity, ambulation function, and daily function have been inconsistent.^5-10

Another compelling approach is afferent sensory stimulation applied to the UE, which was beneficial for motor recovery, as demonstrated by the FMA.¹¹ One type of afferent stimulation is provided by the mesh glove (MG; Prizm-Medical Inc, Oakwood, GA). The MG uses a 2-channel electrical stimulator to provide synchronous or reciprocal sensory stimulation with variant amplitudes and can provide stimulation of the entire hand. The MG can be used to reduce muscle hypertonia and facilitate residual movement, which may ameliorate motor impairment and increase volitional activity of the hand and arm in stroke patients.^12,13 A study by Zehr et al¹⁴ also suggests that stimulation of the superficial radial nerve at the wrist may increase dorsiflexion bilaterally in the stance-swing transition of ambulation. Providing MG stimulation might also result in plastic changes in the primary motor cortex¹⁵ and induce a long-lasting effect on motor cortical excitability.^16-18

Combining 2 treatment protocols has been advocated as a way to improve treatment efficacy.^19-21 MG stimulation could be used to supplement other treatment,²² such as MT, to normalize muscle tone and enhance hand or ambulation function. Besides, the possible mechanism of brain plasticity underlying MG is similar to the mechanism behind MT, in that the primary motor cortex might be activated. Adding MG to MT might further augment cortical reorganization.^19,20 MG stimulation added to MT improved manual dexterity and ability to transfer skill during daily activities.²³ However, this pilot study did not recruit a control group and therefore could not estimate a possible gained value, if any, in providing this new approach. The present study included a larger sample of stroke patients, a control group that received task-oriented therapy, and further explored the possible benefits of MT coupled with MG.

This study used the Myoton-3 myometer to objectively assess the treatment effects on muscle tone in the UE instead of a subjective measure such as the Modified Ashworth Scale (MAS).²⁴ This study also included kinematic analyses to obtain objective information on spatial and temporal characteristics (eg, movement time, displacement, and joint recruitment) of UE movements. Kinematic analysis helps us understand whether a true change in the end point control and joint motion/synergy patterns has occurred^21,25,26 and infer possible reorganization of the brain after treatment.^27,28 No previous research, to our knowledge, has addressed change in the motor control mechanism after MT.

The present study combined MG stimulation with MT (MT + MG) and compared the efficacy of MT + MG, MT, and a control therapy (CT) on motor impairment, as measured by the FMA and Myoton-3, and on motor function, as measured by the Box and Block Test (BBT) and 10-Meter Walk Test (10-MWT). Also investigated were strategies of motor control indicated by kinematic parameters and function in daily life situations measured by the Motor Activity Log (MAL) and ABILHAND questionnaire. Possible adverse effects, including pain and fatigue, were monitored.

The study recruited 43 patients (11 women) with stroke from 4 medical centers who had met the following criteria: (a) onset of an ischemic or hemorrhagic stroke of at least 6 months duration; (b) the ability to reach Brunnstrom stage III or above in the proximal and distal part of the arm; (c) no severe spasticity in any joints of the affected arm (Modified Ashworth Scale ≤ 2)²⁹; (d) no serious cognitive deficits (Mini-Mental State Examination score > 24)³⁰; (e) no serious vision or visual perception deficits (score of 0 on the best gaze and visual subtest of the National Institutes of Health Stroke Scale)³¹; (f) no history of other neurologic, neuromuscular, or orthopedic disease; and (g) no participation in other studies concurrent with this study. Participants signed informed consent forms approved by the institutional review boards of the participating facilities.

The study was a single-blind, randomized, pretest and posttest control group design (Figure 1). Participants were stratified into 4 strata according to the side of lesion and the level of motor impairment (the cutoff point was 40 in total scores of the FMA UE subtest³²). A set of numbered envelopes containing cards indicating the allocated group was prepared for each stratum. When a new eligible participant was registered, an envelope was randomly extracted, and the relevant therapist was informed of the group allocation.

Figure 1. Flow diagram shows enrollment of patients and completion of study according to the CONSORT statement.

Abbreviations: CT, control therapy; MG, mesh glove; MT, mirror therapy.

Four certified occupational therapists were trained in the administration of these 3 protocols by 2 primary investigators to conduct consistent intervention. Outcome measurements were administered at baseline and immediately after the intervention by 2 trained occupational therapists. The evaluators were unaware of group allocation, and the participants were blinded to the study hypotheses.

All participants received a 1.5-hour training session per day, 5 days/week for 4 weeks. The treatments were provided during the daily occupational therapy sessions. All other routine interdisciplinary stroke rehabilitation was continued as usual.

The MT protocol included 10 minutes of warm-up, 1 hour of mirror box training, and 20 minutes of functional task practice. The warm-up activities included stretching and passive range of motion exercises. During the mirror box training, a mirror box that reflected the image of the unaffected arm was placed in the participant’s midsagittal plane. Participants were required to symmetrically move both hands as simultaneously as possible while watching the reflection of the unaffected arm in the mirror as if it were the affected one. To ensure that the participants focused on the reflection, the unaffected arm was placed in the mirror box, and vision of the affected arm was occluded by a vertical board placed beside the mirror box. The activities consisted of transitive (eg, gross motor tasks, such as reaching out to put a cup on a shelf, or fine motor tasks, such as picking up marbles) and intransitive movements (eg, gross motor movements, such as pronation and supination, or fine motor movements, such as finger opposition). After the mirror box training, functional task practice was provided according to task-oriented treatment principles.

The protocols of the MT + MG group were similar to the MT group (ie, 10 minutes of warm-up, 1 hour of mirror box training, and 20 minutes of functional task practice). The MT + MG group also wore the MG during mirror box training (Figure 2). For safety reasons, the conscious sensory threshold, with a feeling of tingling on palmar and dorsal sides, was set on the unaffected hand. Then, the MG was applied on the affected hand.

Figure 2. The intervention setup of mesh-glove stimulation combined with mirror therapy.

The MG protocol depended on the muscle tone of the participants. Participants with a MAS score of 2 points in any joint of the affected hand received 2-step electrical stimulation. The first step was 80% of the conscious sensory threshold that was a subthreshold, and the second step was at the conscious sensory threshold. Each step lasted about 30 minutes. Participants with a MAS score lower than 2 points received 3-step electrical stimulation. The first 2 steps were the same as that mentioned above, and step 3 was stimulation above the threshold, defined by 120% of the conscious sensory threshold. Each step took 20 minutes.¹⁶ The subthreshold stimulation could decrease spasticity, and stimulation at the threshold or higher could improve awareness of the hand and enhance volitional activity.^16,18,33

The CT group received 1.5 hours of therapeutic activities equivalent in duration and intensity to the MT + MG and MT groups, based on task-oriented treatment principles. Tasks used for practice were selected in accord with the abilities of the participants. In addition to functional task practice, this group also received warm-up similar to the other 2 groups.

This study included clinical measures for motor impairment, motor function, daily function, and adverse effects, and kinematic data for motor control. All measures have been reported to be adequately reliable and valid.^24,34-38

The UE subscale of FMA total score was used to evaluate several dimensions of motor impairments. The FMA measures the movements and reflexes of the UEs and coordination/speed on a 3-point ordinal scale (0 = cannot perform; 1 = can perform partially; 2 = can perform fully).³⁴

We used myotonometric measurements obtained with the Myoton-3 device (Muomeetria AS, Tallinn, Estonia) to assess the tone of skeletal muscles. The Myotone-3, which is placed perpendicular to the skin surface above the muscle to be tested, produces a short impulse on the muscle. An acceleration transducer records the damped oscillations of the muscle response. The muscle tone values of the biceps, flexor carpi radialis, and flexor carpi ulnaris were recorded.²⁴

The BBT was used to assess manual dexterity. A box is separated into 2 equal sides. Subjects used the affected hand to move as many blocks as possible, one at a time, from one side to the other in 60 seconds. The number of blocks is calculated at the end of the test.³⁵

The 10-MWT was used to assess the mobility function, measuring the time and the numbers of strides required to walk 10 meters under 2 conditions: (a) each participant’s self-pace (self-pace) and (b) the quickest speed that each participant could walk (as quickly as possible [AQAP]).³⁶ The velocity and stride length of the participant were calculated.

The MAL is a semistructured interview that assesses subjective report of 30 common daily tasks evaluating the frequency of affected UE use. It consists of subscales assessing the amount of use (AOU) and quality of movement (QOM). The MAL uses a 6-point ordinal scale, with higher scores indicating better performance.³⁷

The ABILHAND questionnaire is a self-report assessment of UE function that consists of 23 bilateral activities in daily life. Patients were asked to estimate their difficulty in performing each activity using a 3-point ordinal scale. The higher the scores, the more difficulty the patients feel.³⁸ The Rasch model was used to estimate a linear ability for each patient and linear difficulty for each item.³⁸

The experimental task required participants to press a desk bell with their affected hand as quickly as possible. Participants sat on a height-adjustable, straight-backed chair with the seat height set to 100% of the lower leg length. The tested arm was pronated, and the hand rested on the edge of the table in a neutral position with 90° flexion at the elbow joint. The desk bell was placed in the midline of the table. The bell distance, measuring from the medial border of the axilla to the bell, was standardized to 125% of the participant’s functional arm length (defined as from the medial border of the axilla to the distal wrist crease³⁹). If the maximum distance the participant could reach was less than 125% of the functional arm length, the bell distance was adjusted to the maximum reachable distance. The instruction to the participants was, “When you hear the start signal ring, please use the index finger of the affected hand to reach and press the bell as fast as possible.” After a practice trial, 3 trials were performed.

A 7-camera motion capture system (VICON MX, Oxford Metrics Inc, Oxford, UK) at a sampling frequency of 120 Hz was used with a personal computer to record kinematic data. Three channels of analog signals were collected simultaneously: one for instruction of movement start and the others for target bells. Markers were placed on the acromion, middle of humerus, lateral epicondyle, styloid process of ulna and radius, and index nail of the affected side. Movement onset was defined as a rise of tangential wrist velocity above 5% of its peak value. Movement offset was defined as a fall of tangential wrist velocity below 5% of its peak value. Movement was digitally low-pass filtered at 5 Hz using a second-order Butterworth filter with forward and backward pass.

Kinematic data were processed with an analysis program coded by LabVIEW language (National Instruments, Inc, Austin, TX). Kinematic variables included normalized movement time and normalized movement units to represent end point control, and joint recruitment, including normalized shoulder flexion, normalized elbow extension, and maximum shoulder abduction, to describe movement patterns. Movement time, which refers to the execution time of the reaching movement and is the interval between movement onset and offset, was a variable to represent temporal efficiency.^40,41 Movement unit was defined as 1 acceleration and 1 deceleration, which refers to motor smoothness.^40,41 Joint recruitment was defined as the difference of shoulder flexion or elbow extension from movement onset and movement offset, and maximum shoulder abduction during each reaching motion. Maximum shoulder abduction and elbow flexion are 2 critical components of the flexor synergy pattern often exhibited by patients with stroke.^42,43 Reduced maximum shoulder abduction with enhanced elbow extension indicates a diminished synergy pattern.⁴² Because bell distance varied, depending on the individual’s arm length, and therefore influenced reaching distance (defined as the distance between the initial index marker position at resting and the target desk bell), all variables, except for maximum shoulder abduction, were normalized to reaching distance.

Self-reported assessments on pain and fatigue severity were administered immediately after the first and last treatment sessions to evaluate adverse effects. The evaluator presented the question, “What did you feel in terms of pain/fatigue severity during the treatment today?” The participant responded on an 11-point ordinal scale (0 = no pain/fatigue; 10 = the most severe pain/fatigue).

Data were analyzed with SPSS 19.0 software (SPSS Inc, Chicago, IL). We calculated that a sample size of 42 was needed for an 80% likelihood in detecting a group difference with a type I error of .05, based on the previous pilot study showing that MT combined with afferent stimulation resulted in improvements with effect sizes of approximately .50.²³ Baseline differences among groups were analyzed by analysis of variance for continuous data and by χ² for categorical data. To control the variance among groups in the pretest scores, analysis of covariance was used to compare the treatment effects among groups on different end points at posttest. The pretest performance was the covariate, group was the independent variable, and posttest performance was the dependent variable. No multiple testing corrections were made to restrain the type II error considering the early stage of intervention development.

Post hoc analysis using highly significant differences was used to evaluate the difference of each group. The η² was calculated for each outcome variable to index the magnitude of group differences. The η² value represents the variability in the dependent variable (posttest performance) that can be explained by the independent variable (group). A large effect is represented by an η² of at least 0.14, a moderate effect by an η² of 0.06, and a small effect by an η² of 0.01. The level of statistical significance (α) was set at .05 for all comparisons.⁴⁴

The study recruited 43 participants (mean age = 55.0 years). The MT + MG and the MT group consisted of 14 participants each, and the CT group consisted of 15 participants. After the treatment programs, the Myoton and kinematic data were missing for 2 participants. There were no significant differences in demographic characteristics among groups (Table 1). Group differences were not significant for pain (F_2,39 = 1.65, P = .06) and fatigue (F_2,39 = 3.05, P = .21).

Table 1. Characteristics of Study Participants (N = 43).

Table 2 reports the descriptive and inferential results, except the kinematic performance. Total FMA scores were significantly different, with a large effect among the 3 groups (F_2,40 = 3.35, P = .045, η² = .147). Post hoc analyses revealed that the MT + MG and the MT groups were significantly higher than the CT group for the FMA total score (P = .0032 and .0031, respectively). Group differences in the muscle tone were not significant.

Table 2. Descriptive and Inferential Statistics for Clinical Outcome Measures.

Significant and large effects on motor function were measured by the BBT (F_2,40 = 4.39, P = .019, η² = .184) and the 10-MWT (velocity of self-pace: F_2,40 = 5.02, P = .011, η² = .205; stride of self-pace: F_2,40 = 7.13, P = .002, η² = .268; velocity of AQAP: F_2,40 = 4.06, P = .025, η² = .176). No significant difference was found in stride length of the AQAP subscores in the10-MWT. Post hoc analyses revealed that the MT + MG and the CT group improved more than the MT group in the BBT (P = .007 and P = .036, respectively). The MG + MT group showed larger improvements than the MT group on the velocity of self-paced ambulation (P = .004), the stride of self-paced ambulation (P = .016), and the velocity of AQAP (P = .014). The CT group showed larger improvements than the MT group on the velocity of self-paced ambulation (P = .031), the stride of self-paced ambulation (P = .016), and the velocity of AQAP (P = .023).

For daily function, no significant group effects were found on the ABILHAND or on the AOU and QOM of the MAL. Table 3 reports the descriptive and inferential results for the kinematic performance. The results revealed significant and large effects on normalized shoulder flexion (F_2,38 = 3.43, P = .043, η² = .157) and reduction of maximum shoulder abduction during reach (F_2,38 = 4.55, P = .017, η² = .198) among the 3 groups. Post hoc analyses revealed that the MG + MT (P = .008) and the MT groups (P = .023) showed significantly greater reduction of maximum shoulder abduction than the CT group. The CT group showed larger improvements than the MT group on normalized shoulder flexion (P = .0013). Small and nonsignificant effects were found on normalized movement time, normalized movement unit, and the normalized elbow extension.

Table 3. Descriptive and Inferential Statistics for Analysis of Kinematics Performance.

The present study demonstrated that patients in the MT + MG and MT groups performed better compared with those in the CT group in the reduction of motor impairment. Combining MT with MG stimulation showed additional effects on manual dexterity of the affected hand, self-paced ambulation, and velocity of quickly paced ambulation compared with MT alone. Relative to CT, MT + MG and MT reduced maximum shoulder abduction during forward reach, which is regarded as reducing a critical component of the flexor synergy pattern. However, CT increased shoulder flexion more than the other groups. For daily function, we found no group differences immediately after the 4-week interventions. There was no adverse effect as measured by self-reported pain and fatigue.

Compared with the CT group, the MT + MG and MT groups showed improved motor impairment as indicated by the FMA total scores, in line with previous research on MT.^2,6,10 As an explanation for the treatment effects, the visual input during MT could substitute for absent or reduced proprioceptive input from the affected body side⁴⁵ and, consequently, helped recruit the premotor cortex or balance the neural activation within the primary motor cortex toward the affected hemisphere to facilitate motor improvements.^3,4,46

We found MT combined with MG stimulation provided additional benefits on manual dexterity compared with MT alone, consistent with the findings of a pilot study on MT combined with somatosensory stimulation²³ and studies related to electrical stimulation.^47,48 The extra benefit on manual dexterity is very encouraging, considering its importance for activities of daily living⁴⁹ and that previous studies of MT showed unclear results on manual dexterity.^2,6 MG stimulation might induce rapid plastic change in sensorimotor regions of the cortex^16,17,50 related to the hand to which the stimulation was applied and modulate the intracortical γ-aminobutyric acid pathways that reduce intracortical inhibition in the motor cortex of the ipsilesional hemisphere.⁴⁸ Combining MT with MG could provide cross-modal inputs (ie, sensation from electric stimulation and visual image input from the mirror) during training that may modulate activation of the somatosensory cortex and facilitate dexterity recovery.^21,51

Another important finding is that combining MT with MG demonstrated significant improvements on ambulation function measured by the 10-MWT compared with MT alone. This finding is consistent with a pilot study²³ and some studies of electrical stimulation on the UE.^12,52 Stimulation of cutaneous nerves of the hand could elicit an interlimb reflex response in muscles across the body that is believed to be related to motor coordination between arms and legs during walking.^14,53 In addition, arm integration during reciprocal activities, which were part of the training, could alter leg movement via propriospinal neural pathways.⁵⁴ Improvement in UE motor control may contribute to arm swing and help generate forward propulsion at the foot.⁵⁵

Our kinematic results revealed that MT + MG or MT might reduce shoulder synergy movements, as indicated by less maximum shoulder abduction⁴² during elbow extension, compared with the CT group. According to the assumption of motor learning, the neural structures controlling movement are required to adapt to constraints imposed by, at least, physical demands.⁵⁶ MT restrained arm movement in a size-limited box, which might not allow for a great range of shoulder abduction during task performance. Consequently, the synergy pattern of shoulder abduction might be inhibited. This result can also be cross-validated by our findings of improved total FMA scores, because the FMA involves the ability to perform out-of-synergy movements,³⁴ the scores of the FMA indicated a reduction in shoulder synergy movement.⁵⁷ In contrast, the CT patients gained a greater amount of shoulder flexion than the MT + MG and MT patients. The CT involved a variety of therapeutic activities requiring shoulder forward flexion and elevation. Accordingly, the CT patients exhibited better improvement in shoulder flexion than patients receiving the other 2 treatments. Task-specific training has been shown to be effective in recovery of movement poststroke.⁵⁸

No group differences were noted in the muscle tone of the biceps, flexor carpi radialis, and flexor carpi ulnaris. One possibility is that our participants had mild to moderate spasticity (MAS ≤ 2) at pretest. Most participants in the MT + MG group received the 3-step MG stimulation protocol to increase awareness of the affected hand and enhance volitional activity rather than the protocol to reduce spasticity,^15,17,32 resulting in nonsignificant effects on spasticity.

We found no group differences in daily function, which is in accord with previous research.²³ However, a scrutiny of the descriptive data showed all groups improved in some activities of daily living outcomes, and additional statistical analysis showed significant differences between pre- and posttreatment for each group (P = .014-.047), indicating that all treatments were beneficial to daily function. Future research might include follow-up assessments to study possible changes in activities of daily living or incorporate more functional task practice into MT + MG or MT to improve function in daily-life situations.

As a limitation, our study included only people with mild to moderate motor impairments. Some studies have reported that patients with severe motor deficits achieved more improvements after interventions.⁵⁹ The evidence for optimal intensity of afferent stimulation (eg, electric current intensity) for stroke rehabilitation is limited.⁵⁹ Because we found no adverse effects using stimulation at the threshold level, it might be possible to increase the intensity of the electrical stimulation.⁵⁹

This study is unique in demonstrating the comparative effects of MT + MG, MT alone, and task-oriented therapy on a variety of motor and functional outcomes. MT + MG and MT alone improved motor impairment and reduced the critical component of synergy patterns (ie, shoulder abduction) more than CT. MT + MG yields broader aspects of motor recovery. Our study showed the benefits of combining MT and MG stimulation for improving manual dexterity and ambulation function. In addition, all treatments here showed benefits in daily function. Future research may address the dosing issue by studying the effects of stimulation intensity and integrating functional task practice in the MT + MG protocol in an attempt to optimize the effects on daily function.

Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This project was supported in part by the National Health Research Institutes (NHRI-EX101-9920PI and NHRI-EX101-10010PI), the National Science Council (NSC-100-2314-B-002-008-MY3 and NSC99-2314-B-182-014-MY3), and the Healthy Ageing Research Center at Chang Gung University (EMRPD1B0371) in Taiwan.

Abstract

Purpose

Carpal tunnel syndrome (CTS) can adversely affect fine motor control of the hand. Precision pinch between the thumb and index finger requires coordinated movements of these digits for reliable task performance. This study examined the impairment upon precision pinch function affected by CTS during digit movement and digit contact.

Methods

Eleven CTS subjects and 11 able-bodied (ABL) controls donned markers for motion capture of the thumb and index finger during precision pinch movement (PPM). Subjects were instructed to repetitively execute the PPM task, and performance was assessed by range of movement, variability of the movement trajectory, and precision of digit contact.

Results

The CTS group demonstrated shorter path-length of digit endpoints and greater variability in inter-pad distance and most joint angles across the PPM movement. Subjects with CTS also showed lack of precision in contact points on the digit-pads and relative orientation of the digits at contact.

Conclusions

Carpal tunnel syndrome impairs the ability to perform precision pinch across the movement and at digit-contact. The findings may serve to identify deficits in manual dexterity for functional evaluation of CTS.

1 Introduction

Individuals with carpal tunnel syndrome (CTS) often suffer from numbness, tingling, pain, and clumsiness of the hand . These symptoms lead to notable impairments in the ability to perform fine motor tasks involving the thumb and index finger, thereby reducing quality of life by compromising the ability to execute activities of daily living such as manipulating buttons, writing, and using utensils . CTS is caused by compression of the median nerve in the carpal tunnel, but its etiology is not always readily evident and may develop from various precipitating factors including repetitive manual work, genetics, pregnancy, and injury . Treatment of CTS is often predicated on clinicians’ clinical assessment and patients’ performance at examination, and current diagnosis methods such as nerve conduction, imaging, sensation tests, and clinical maneuvers can produce inconclusive results ^; . Further reducing the reliance upon either subjective or qualitative measures for clinical assessment of CTS pathology upon hand function may improve diagnosis, which can also serve as a long-term objective of functional motion analysis of the hand.

Median nerve compression incites sensorimotor dysfunction of the digits of the hand, most notably the thumb and index finger . Since clinical tests for CTS typically evaluate symptoms and physiological consequences rather than function, examining the ramifications of median nerve impairment on coordinated force generation and movement of the hand is in need and has been attempted. Although diminished thumb abduction strength has been considered to be associated with CTS ^; , it was also shown that multi-directional force production at the thumb is largely preserved with CTS .When median a nerve block was administered to produce acute median neuropathy, several studies have reported decreases in grip strength and force production of the thumb ^-. The ability to adjust submaximal force during precision grip also appears to be notably afflicted by median neuropathy ^; . While CTS may diminish force-coordination of grip, neuropathic effects on the ability to skillfully move the digits also can limit dexterous manipulation of objects.

The precision pinch movement (PPM) task signifies a functional daily task that focally involves the thumb and index finger to prepare for grasp and manipulation of small objects . Since the median nerve has notable motor (first and second lumbricals) and sensory (palmar-side sensation) innervation to the thumb and index finger, the PPM is well-posed for studying median nerve dysfunction. Previous studies have demonstrated deficiencies in PPM execution in the presence of median nerve dysfunction. Similar to behavior following anesthesia-block of the median nerve , it was observed that CTS individuals performing PPM exhibited increased variability of the tip positions and joint angles of the thumb and index finger at contact. However, the inability to precisely locate the digits would be preceded by deficit in dynamic control of the digits during the movement. Therefore, assessing the performance of the movement function of the thumb and index finger may better illuminate the sensorimotor deficit induced during functional tasks in response to median nerve dysfunction.

The purpose of this study was to investigate the trajectory kinematics of the thumb and index finger during PPM for individuals with CTS in addition to contact. Specifically, PPM is defined by the consistent and coordinated bringing together of the thumb and index finger pads into contact from an initially, open-hand configuration. While free of force constraints, this task specifically pertains to the basic movement capabilities of the digits affected by CTS. Characterizing differences in movement features during PPM for individuals with CTS versus healthy, able-bodied (ABL) controls demonstrates the functional consequences of CTS and provides insight into the related patho-mechanism.

We hypothesized that the sensorimotor deficit associated with CTS would produce pathokinematics of the thumb and index finger which reflect degraded movement performance. The variables characterized in this study indicate the capacity and consistency to perform the PPM movements from which to assess the dysfunction associated with CTS. Specifically, CTS would lead to impairment of precision pinch function with the following characteristics: (1) general movement restriction quantified by inter-pad distance, (2) relative increase in index finger path-length as compared to thumb path-length, (3) increased variability in pinch trajectory, (4) increased variability of the orientation angle between the distal segments of the thumb and index finger, and (5) decreased precision of digit-pad contact. For parameter (2), we initially expected that while path-length for both digits may decrease with CTS, the index-finger may act to compensate for the pronounced loss in thumb function following median nerve impairment . Confirmation of these hypotheses could serve as kinematic hallmarks of the impact of CTS on hand function.

2 Methods

Human Subjects

Subjects were age- and gender-matched between the two population groups of ABL (able-bodied) and CTS (carpal tunnel syndrome). Twenty-two subjects (11 ABL, 11 CTS) between the ages of 35-64 years participated in this study. Subjects volunteered after initially being informed of the study by their consulting physicians and then contacting our study coordinator for further details. Each group consisted of 9 females and 2 males with mean age of 49.5 ± 9.6 years for CTS and 48.6 ± 7.6 years for ABL. The subject distribution across gender and age in this study is consistent with notably higher incidence of confirmed CTS among women with mean age near 50 years . All participants were right-hand dominant, verified by the Edinburgh Handedness Inventory . The CTS subjects were diagnosed upon positive confirmation of the following criteria: 1) history of parathesias, pain, and/or numbness in the median innervated hand territory persisting for at least 3 months; 2) positive provocative maneuvers including Tinel’s sign, Phalen’s test, and/or median nerve compression test; 3) abnormal electrodiagnostic testing consistent with median nerve neuropathy at/or distal to the wrist ; 4) an overall CTS Severity Questionnaire score greater than 1.5; (5) positive diagnosis according to clinical discretion . The ABL subjects did not previously report or demonstrate a history of disease, injury, or previous complications involving the hand and upper extremity. CTS and control subjects exclusion criteria included: 1) electrodiagnostic tests, which indicate ulnar, radial, or proximal median neuropathy; 2) existence of a central nervous system disease (e.g., multiple sclerosis, myasthenia gravis, Parkinson’s disease); 3) pregnancy; 4) history of trauma or surgical intervention to the hand/wrist; 5) rheumatoid arthritis or osteoarthritis of the hand/wrist; 6) diabetes; 7) recent steroid injection to the hand. The mean pinch strength values across the ABL and CTS subjects were 57.2±18N and 53.1±18N, respectively. All participants signed an informed consent approved by the local Institutional Review Board.

Collection of Marker Position Data

Retro-reflective markers were affixed to the dorsal surface of the right hand of each subject to derive thumb and index finger kinematics. The 3-D position of each marker was tracked at 100Hz using a motion capture system (Model 460, Vicon Motion Systems and Peak Performance, Inc., Oxford, UK). A marker set established in our laboratory was employed to compute joint kinematics with considerations of anatomical alignment (Figure 1A) . To explicitly define the position and orientation of the distal digit segment of the thumb and index finger, the marker set included a nail marker-cluster employed with a digit alignment device (DAD, Figure 1B) . The long-axis of the nail-cluster stem was approximately in-line with the central prominence of the finger-pad. The DAD block accommodates most hand sizes such that subjects typically are able to position the index finger and thumb along the long-axis of the block and palmar-side of the digits flush on the respective block planes. The marker-cluster on the back of the hand placed along the second metacarpal served as the local reference frame for the hand. It was assumed that the second metacarpal would serve as a stable proximal reference for both the index finger and thumb in order to utilize a minimal set of markers in computing angular kinematics .

Experimental set-up A) Markers utilized for motion tracking and computing digit kinematics B) Calibration using a digit alignment device C) Subject with arm-support cyclically performing 2-sec cycle of precision pinch movement (markers not shown) D) Aligned axes about which relative rotation of distal thumb with respect to distal index finger defines distal orientation coordination angle (DOCA).

Note: Origin of axes located at respective “nail-point” estimated from the respective nail marker-cluster, which subsequently serves as center for digit-pad sphere model.

Experimental Protocol

After subjects donned the marker set and underwent the calibration procedure described in ^; , each subject performed trials involving consecutive cycles of PPM at a metronome pace to allow for performing a PPM cycle in 2 sec. For a cycle of PPM, a subject placed their arm in a splint (Figure 1C), while transitioning their hand from the open (all digits comfortably extended to maximally separate thumb and index finger-pads) to closed (thumb and index finger pads contacting in tip-pinch) back to open configuration. The subject initially was in the open position. After the “go” command, the subject would smoothly transition to the closed position following a metronome beep so as to reach the closed position on the following beep then smoothly return to open on the third beep to complete the cycle. The subject continued to perform a total of 10 consecutive PPM cycles to mark the end of the trial. The subject first underwent 5 practice trials with eyes open to accommodate to the protocol. The subject subsequently performed 5 test trials (10 cycles per trial) while visual feedback was blocked with an opaque sleeping mask to prevent visual compensation of proprioceptive deficit . Each subject was instructed to perform each cycle of PPM as naturally, but as consistently similar, as possible. A one-minute rest was provided between consecutive trials. All subjects reported not having notably worsened pain while performing the experiment compared to any pain or discomfort they felt prior to the session commencing.

Computation of Digit Kinematics

The protocol for computing joint angles from this marker set followed that described in . For adjacent segments of the same digit, aligned axes of rotations about the X, Y, and Z-axes were assumed to correspond to anatomical extension(+)/flexion(-), abduction(+)/adduction (-), and internal(+)/external(-) rotation, respectively, following the ISB (International Society of Biomechanics) convention . The joint angle degrees of freedom (DOFs) being characterized were the metacarpophalangeal (MCP) extension/flexion and abduction/adduction, proximal interphalangeal (PIP) extension/flexion, and distal interphalangeal (DIP) extension/flexion joints of the index finger. For the thumb, the DOFs included the interphalangeal (IP) extension/flexion, MCP extension/flexion abduction/adduction, and carpometacarpal (CMC) extension/flexion, abduction/adduction, and internal/external rotation. To assess relative orientation of the distal segments, the distal orientation coordination angle (DOCA) was defined as the Euler angles of the distal thumb segment relative to the distal index segment (Figure 1D). Rotations with respect to the distal index segment coordinate system about the X, Y, and Z-axes were denoted as Pitch, Yaw, and Roll, respectively . Ultimately, the three DOCA rotations comprehensively describe how the thumb is oriented relative to the index finger during the PPM. It should be noted that for the CMC joint, which connects the first metacarpal to the trapezium, the second metacarpal was used as a reference surrogate for the trapezium. This was done with the assumption that relative changes in orientation between the trapezium and second metacarpal would be minimal to obtain sufficiently accurate estimations of presumed pure rotations about orthogonal axes of rotation at the CMC joint according to convention specified in . The presumed axes of CMC rotation are orthogonal to those defined by the block coordinate system seen in (Figure 1B). Specifically, CMC extension/flexion, abduction/adduction, and internal/external rotation occur about axes pointing medially, dorsally, and proximally to the long-axis of the first metacarpal.

Computation of the Precision of Digit-Pad Contact

Using each nail marker-cluster (Figure 1A) as a reference for an aligned 3-D coordinate system (Figure 1B), a spherical model of the respective digit-pad was represented. A virtual “nail-point” is computed as a projection along the marker-cluster stem to the dorsal surface of the nail and served as the respective sphere “center”. Using digital calipers, the digit thickness was measured as the transverse distance from dorsal surface to digit-pad prominence of the distal segment for both the thumb and index finger and served as the sphere “radius”. The shortest distance between the digit-pad surfaces was subsequently denoted as “inter-pad” distance. The contact between the thumb and index finger was estimated to occur at initial intersection between the virtual spheres. A circular area of contact points (from multiple trials) projected upon each subject’s digit-pad model surface was also computed. The center of this contact area was the mean point of contact location, and the radius was the mean distance away from this location across all trials.

Statistical Analysis

Comparisons between the ABL and CTS groups were made using the Mann-Whitney-Wilcoxon non-parametric test for variables. These variables include movement range, pinch contact location, and pinch contact DOCA. For comparing trial-to-trial trajectory variability, a paired t-test was used for mean trial-to-trial variability. Trajectory variability was defined as the 1 standard deviation (s.d.) band about the mean trajectory for each subject across equally-spaced points defined for each pinch cycle (i.e., open → closed → open). The initial open-portion of each pinch cycle was defined to begin at a local maximum observed in inter-pad distance for the corresponding PPM cycle that is one standard deviation greater than the mean inter-pad distance across all cycles for a given subject. When comparing between groups, the variability for one group should be “normalized” to be on the same scale of the other group since absolute variability generally increases proportionally with range of movement. Thus, the normalization factor multiplying the variability of group B to scale to group A is range(A)/range(B). To consider differences in hand sizes, variables of inter-pad distance and digit path-lengths were normalized by respective subject palm width.

In summary, the movement parameters being calculated include mean trajectory range (R), mean trial-to-trial trajectory variability (V), mean-value at contact (MC), and variability at contact (VC). The kinematic variables being observed with corresponding parameter calculations are as follows: inter-pad distance (R, V), joint angles (R, V), pinch contact location (MC, VC), and distal orientation coordination angle (R, V, MC, VC).

3 Results

The range for inter-pad distance across the PPM cycle was larger for ABL than CTS (Figure 2). On average, the peak inter-pad distance for CTS subjects was 26% lower than that for ABL subjects (p<0.01). In comparison to the ABL subjects, the CTS subjects had 16% greater cycle-to-cycle variability across the pinch trajectories (p<0.01). The three-dimensional (3-D) path-length values of the thumb and index finger nail-points across the PPM cycle for the ABL and CTS groups are shown in Figure 3. The path-length was significantly greater for the ABL than CTS groups for both the thumb (p<0.05) and index finger (p<0.001). On average, the ratio of index-to-thumb path-length for the CTS subjects (2.87±1.7) was greater than the ABL subjects (2.09±0.8), but the difference was not significant according to a two-sample t-test (p=0.17).

LEFT: Mean trajectory (solid lines) and cycle variability (dashed lines) across condition types: ABL = able-bodied subject, CTS = carpal tunnel syndrome subject. RIGHT: Bar plots comparing range and range-normalized trajectory variability for ABL versus CTS.

Note: **p<0.01, distance normalized by “palm width”

Bar plots comparing index and thumb path-lengths (left, middle) and ratio of index to thumb path-length (right) for ABL versus CTS.

Note: *p<0.05, ***p<0.001, distance normalized by “palm width”

The mean range and variability (based on the +/- 1 s.d. about the mean trajectory) values for the joint-DOF angles observed over the pinch cycle, and denoting of significant differences between ABL and CTS, are shown in the bar graphs of Figure 4. Overall, the angular ranges were greater for ABL than CTS, and significant differences (p<0.05) were found for Thumb-MCP extension/flexion (Δ = 17.0°), Index-MCP extension/flexion (Δ = 18.6°), and DOCA-Roll (Δ = 45.2°). For variability, significant increases were observed for CTS among the thirteen angular trajectories (p<0.001) reported except Thumb-CMC extension/flexion (no significant difference, p=0.10), Thumb-CMC abduction/adduction (decrease, p<0.01), and DOCA-Pitch (decrease, p<0.01).

The range (R) and variability (V) between ABL and CTS for angular excursions at corresponding degrees-of-freedom (DOFs) are shown for comparison. Across all 13 DOF trajectories being observed, the CTS group demonstrated reduced range and greater variability at 12 and 10 DOFs, respectively.

The precision of pinch contact over all repetitive trials is described by the contact areas depicted in Figure 5 for both the ABL and CTS groups. The contact area on both digits was greater for the CTS group, and the area for the index finger was found to be significant (p<0.05) (Table 1). In comparing differences in mean contact location between ABL and CTS groups, the absolute difference in each X-Y-Z location dimension for each digit was not significantly different (p>0.05). For relative digit orientation at contact, only the DOCA-Roll component demonstrated a significant difference (p<0.05).

Mean contact location and area on spherical models for thumb and index finger shown for ABL (blue) and CTS (red) groups relative to respective nail XYZ coordinate systems.

Note: contact area circle radius equals mean distance of contact points across all trials about mean contact point location (circle center).

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Table 1

Relative position and orientation of distal segments of digits at contact (mean across all subjects)

4 Discussion

In this study, the effects of CTS on the ability to perform precision pinch movement were investigated and compared to the ABL group by observing differences in (1) movement range, (2) variability of the dynamic movement, and (3) digit configuration at digit contact. The CTS group generally demonstrated reduced performance across these measures compared to the ABL controls. These quantitative observations support the central notion that CTS focally compromises movement dexterity during precision pinch function.

The physiological effects of CTS on functional precision pinch movements can be profound. Chronic symptoms of pain and tingling can produce motor behavior that promotes passive tissue rigidity and a functional disincentive to actively challenge the extremes of the ranges of movement . This phenomenon is supported by our finding that individuals with CTS demonstrated reduced range of inter-pad distance despite having similar pinch strength of the ABL group. Decreased inter-pad distance is a hallmark of the dynamic portion of the pinch task as it describes the overall effects of CTS on the functional ability to separate and bring the digits together in a coordinated manner. The reduction in inter-pad distance range can be attributed to a movement deficit at each individual digit as the path-lengths of the digit nail-points for both the thumb and index finger were reduced for the CTS group.

The significant deficit in range of inter-pad and path-length distances would also indicate a general reduction in range of the angle excursions at the contributing digit joints. Significant reductions in range due to CTS were indeed observed for extension/flexion of the MCP joint for both digits. Deficit at the MCP joint of the index finger may be explained by compromised median nerve innervation to the first lumbrical muscle, which inserts on the radial extensor mechanism near the MCP joint. Compromised motor output of this muscle may explain limited movement at the MCP joint, which as the most proximal joint in the kinematic chain of the index finger consequently reduced path-length of the index nail-point. However, CTS subjects did exhibit similar pinch strength as the ABL subject group. Therefore, if muscle-based contributions to ROM deficit exist, it may be more attributable to issues with sensory feedback such that muscles are being sub-maximally activated. Reduced range of movement at the thumb may be due to CTS effects on the thenar muscles (opponens pollicis, abductor pollicis brevis, flexor pollicis brevis) which produces flexion at the MCP and basal joint of the thumb. The range for DOCA-Roll was also significantly lower with CTS, and this observation is likely due to impaired median nerve innervation of the same thenar muscles which inadequately pronate the thumb into opposition with the index finger. The diminished movement range observed in this CTS study was prevalent across joints than observed by following acute median nerve block. We observed reductions in movement range for all joint DOFs with CTS, while reported notable compensatory increases in thumb-MCP, index-PIP, and index-DIP joint motions. This suggests that the restricted movement with CTS is not only due to sensorimotor dysfunction of the median nerve but may also entail chronic structural changes in conjunction with pain effects. With CTS, stiffening of soft tissue structures of the hand, such as myofascia, may lead to undesirable passive joint rigidity stemming from less daily movement due to persistent sensorimotor dysfunction.

Because the median nerve facilitates function of the muscles of the thenar eminence , we hypothesized that the effects on thumb path-length would be relatively greater to those of the index finger. For each group, path-length was expectedly greater for the index finger than the thumb since the index finger is capable of more versatile changes in posture that demonstrates its relatively greater role in thumb-index co-manipulation . The index-to-thumb path-length ratio was, on average, 32% greater for the CTS group, however, this difference was not observed to be significant, possibly due to the relatively small sample size and unequal variance. A statistical power analysis indicated that 41 subjects are needed to detect the difference.

While reduction in the range of movement is a clear and evident functional outcome of CTS, the effects of CTS on movement precision and coordination require examination of more kinematic details. In this study, the functional deficit from CTS was characterized by assessing the trajectory variability of the dynamic portions of the pinch movement in addition to pinch contact. Measurements at contact indicate an end result of the movement, but the functional impairment from CTS can manifest during the movement as well. While suggested CTS increased the digit position variability at contact, the current study examined the cyclic variability of the index finger and thumb across the entire pinch movement trajectory. The CTS group exhibited increased dyscoordination in terms of significantly higher dynamic (or trajectory) variability for joint angles (7 out of 10), inter-pad distance, and DOCA (Yaw, Roll). This inability to consistently coordinate during the pinching motion prior to or following contact may result from sensorimotor dysfunction yielding both reduced motor output and compromised sensory feedback in dynamically regulating motor function .

At pinch contact, anecdotal increases in variability of the distal segments of the grasping digits with median nerve dysfunction were observed as similarly reported in ^; . Since differences were more notably observed in movement trajectories rather than in contact location, it may signify a compensatory adaptation by individuals with CTS to better locate their digits at pinch termination despite sensorimotor deficit throughout the movement. However, a significant decrease in the contact precision on the index finger with CTS was still demonstrated. A decreasing trend in thumb contact precision was also shown, although it was statistically insignificant. The decreased contact precision on the index finger could be related to impaired coordination between both the thumb and index finger. However, it may be focally attributable to dysfunction of the first lumbrical because its musculo-tendon unit has focal contribution to dynamic index finger action . The lumbricals act via the dorsal aponeurosis to control and enhance the stability of finger motion . Furthermore, the onus of the index finger to undergo larger excursions and changes in posture than the thumb make it more susceptible to undergoing variable contact. Since greater kinematic variability may accrue across the longer trajectories of the index finger, there is likely more inconsistency in converging upon the same contact location. Given the change in contact area, as expected, differences in the relative orientation of the distal digit segments (i.e., DOCA) were also observed. The DOCA-roll component was significantly lower for CTS, which may again indicate a compromised motor ability to reliably rotate the thumb in opposition to the index finger .

Compared to the previous studies investigating precision pinch contact, our study utilized a more stable reference for the digit end-points fixed to the nail , rather than the hand. This consideration in conjunction with a presumed spherical model for the digit-pad serves as a more rigorous measurement tool than direct placement of a marker on the digit. However, this methodology is still a limited approximation of the finger-pad. The true finger-pad is not perfectly spherical and has mechanical compression characteristics that also contribute to cutaneous sensation and regulation of motor performance . However, the geometrical model and parameters utilized in this study allows effective quantification and visualization to distinguish ABL and CTS groups on a functional level.

While CTS has notable effects at the MCP and CMC-basilar joint of the thumb and the MCP joint of the index finger, the relative functional effects of CTS upon the respective digits can be assessed from movement characteristics of the distal segments of the digits. In this study, we observed that ranges of movement and the path-lengths of the nail-points for both digits diminished with CTS. Furthermore, CTS led to increased variability in the movement of these digits in addition to subsequent variation of contact between the finger-pads. These results outline functional consequences of CTS upon movement of the digits in subsequent manipulation of objects. Limited ranges of movement suggest a reduced functional workspace while increased variability during the movement and contact indicate inability to efficiently operate within that workspace. As such, this provides a kinematic basis for manual clumsiness that extends beyond deficits in grip and pinch forces commonly used for functional evaluation for CTS.

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Acknowledgements

The project described was supported by Grant Number R01AR056964 from NIAMS/NIH. The authors would also like to thank Tamara Marquardt for coordinating recruitment of human subjects.

6 References

Denon Rc 1075 Manual Dexterity Test

Denon Rc 1075 Manual Dexterity System