Abstract
Background Biofeedback training is widely used for rehabilitative intervention in patients with central or peripheral nervous impairment to train correct movement patterns; however, no biofeedback apparatus is currently available to correct pinch force ratios for patients with sensory deficiencies.
Design A cross-sectional and longitudinal design was used in an observational measurement study for establishing a prototype and to determine the effects of biofeedback intervention, respectively.
Objective This study aimed to develop a computerized evaluation and re-education biofeedback (CERB) prototype for application in clinical settings.
Methods A CERB prototype was developed integrating pinch apparatus hardware, a biofeedback user-controlled interface, and a data processing/analysis interface to detect momentary pinch performances in 79 people with normal hand sensation. Nine patients with hand sensory impairments were recruited to investigate the effects of training hand function with the CERB prototype.
Results Hand dominance, pinch pattern, and age significantly affected the peak pinch force and force ratio for lifting a 480-g object with a steel surface. In the case of the 79 volunteers with normal hand sensation, hand dominance affected the time lag between peak pinch force and maximum load; however, it was unaffected by pinch pattern or age. Training with the CERB prototype produced significant improvements in force ratio and better performance in the pin insertion subtests, although the results for both 2-point discriminative and Semmes-Weinstein monofilament tests did not change significantly.
Limitations The intervention findings are preliminary.
Conclusions This study developed a conjunct system suited for evaluating and restoring sensorimotor function for patients with impaired hand sensibility. The results from the participants with normal hand sensation could serve as a reference database for comparison with patients with nerve injuries.
To produce coordinated movement depends heavily on a well-integrated mechanism of feedforward and feedback controls between motor and sensory components.1 A motor program does not only indicate movement kinematics and dynamics, but it also contains proper and immediate responses to changes in sensory information. Thus, sensory messages play a critical role in detecting real-time external conditions and can be used to adjust an output force to provide optimal feedforward and feedback control for various manipulation activities.2 For example, a complex integration of sensorimotor memory can develop a well-coordinated pinch pattern via repeated experience and learning procedures.1 Humans use such mechanisms to adapt to an object's physical properties, including weight, texture, and shape, during manipulation.1,3,4 More specifically, the hand's cutaneous sensory input provides information for object recognition and sensory feedback signals from its receptors through central pathways to target areas within the brain in order to modulate precise movement and appropriate force control.5 Thus, people with poor digital sensation frequently report problems in manipulative activities.6,7 Previous studies6,7 have shown that peripheral sensing by grasping digits provides an efficient instantaneous scaling of the magnitude of grip force in response to the actual loading requirements. However, the intention of sensory re-education previously has been focused on stressing the brain to have better interpretations of altered sensory messages but not on directly promoting better functional use in hands with impaired sensibility.
Common clinical methods used for assessing impaired sensations include the Semmes-Weinstein (SW) monofilament test and the static and dynamic 2-point discrimination (S2PD and M2PD) tests.8,9 These assessments are popularly used to test the innervation density of specific mechanoreceptors with quantitative descriptions; however, some previous literature has indicated that these classical tests of sensibility do not reflect the real functional sensations of the injured hand.10–13 Because the central processing of afferent signals increases excitability of primary sensory areas, which, in turn, are closely linked to motor areas in the brain, the capacity to perceive normal and tangential forces with self-initiated lifting of a handheld object can be used as a model for automated sensorimotor control14,15 with a combination of feedback and feedforward elements. Such control is indicated by grip efficiency,16 and the major role of cutaneous mechanoreceptors is in economical grip force scaling.16–21 Accordingly, in our previous article, we reported a detailed examination of pinch force regulation in response to changes in load force, which we considered to be a quantitative method to evaluate the functional sensation of an injured hand.11
Feedback is an important and necessary element for motor learning. A better or more efficient motor response is learned through a well-integrated neurophysiological feedback system. By receiving feedback sensory information from a feedback system, patients can learn to control the monitored function and acquire successive establishment of specific motor responses. The use of biofeedback training for a clinical treatment program is a natural extension of the use of feedback to motivate and inform patients of their success and progress. The most common biofeedback techniques, electromyographic and electrogoniometer biofeedback, are widely used in treatment for patients with central or peripheral nervous impairment to train correct movement patterns or to inhibit abnormal synergies. Currently, no biofeedback apparatus is available that is suitable for correcting the pinch force output of patients with sensory deficiencies. Notably, it has been found that changes in the inertial load induce a dynamic relationship of the pinch-and-load coupling occurring during object transport.22 However, patients without sufficient sensory afference will exert higher force for preventing an object from being slipped off the hand. Thus, a quantitative and precise system that provides real-time, interactive sensory re-education information for patients with impaired sensation intended to help them acquire the functional sensibility needed to carry out tasks would be of great clinical value.
Therefore, the aim of this study was to develop a conjunct system that combines functional sensation evaluation with biofeedback sensory re-education software for clinical applications. Our first objective for the present study was to create a control interface and software system that could link up our previously designed pinch device to set up a computerized biofeedback system for functional sensibility intervention. After establishment of the hardware and software system, the second objective of this study was to build a normal database within the system and investigate the effects of age and sex on pinch force control for different pinch patterns (palmar pinch and 3-jaw chuck), as well as to determine the effects of hand dominance. The third objective was to investigate the effect of a computerized evaluation and re-education biofeedback (CERB) prototype on the fine motor coordination of patients with peripheral nerve injuries.
Method
Establishment of a CERB System
The CERB system integrated 3 components (Fig. 1): (1) custom-designed pinch apparatus hardware, (2) a graphical biofeedback user-control interface, and (3) a data processing and analysis interface. The pinch apparatus (6.0 × 4.5 × 9 cm, 480 g weight) consisted of a custom-made steel cuboid, two 6-axis load cells (Nano-25 force and torque transducers, ATI Industrial Automation, Apex, North Carolina), and a triaxial analog accelerometer (model 2412, Silicon Designs Inc, Issaquah, Washington). During the test, the 6-axis force-torque system and the accelerometer were used to measure the pinch force exerted by thumb and fingers of the participants and to detect the acceleration of the pinch apparatus in space, respectively. According to Newton's second law of motion, the measured load force equals the product of the mass and the vector summation of the gravity and the lifting acceleration. That is, the momentary load force of the pinch apparatus was calculated by combining the gravitational and inertial loads. The pinch force and the load force were recorded and computed during discrete vertical movements to understand the capacity of adjusting pinch force according to inertial load fluctuations, as noted in our previous work.11
Schematic representation of the computerized biofeedback system. T1=the maximum upward acceleration during the lifting task, T2=the peak pinch force onset during the lifting phase, FPpeak=peak pinch force, FLmax=maximum load force.
The CERB system was assembled using LabView programs (National Instruments Corp, Austin, Texas) and was connected to the pinch device hardware. Signals from the load cells and the accelerometer of the pinch apparatus were amplified and sampled at 100 Hz using a 12-bit-resolution, analog-to-digital converter via the InstruNet data acquisition box (model 230, National Instruments Corp), and the data were collected using a laptop computer. This system provided both visual and auditory feedback, depending on the threshold settings of various parameters, which are programmable by the operator according to the patient's needs. The visual feedback displayed the momentary force ratio with corresponding colors (from light-green to red) on the monitor in real time. As the force exertion increased, the color became closer to red. Auditory biofeedback consisting of a low- or high-pitched sound also provided proper cues to trigger the correct output of performance.
Participants
The study participants were 9 patients with peripheral nerve injury and 79 volunteers with no current or past history of neuromuscular or orthopedic problems with the upper extremities within 1 year prior to the study. All of the recruited participants were right handed.
We analyzed grip force control for the participants with normal hand sensation over 3 age groups: young (25–39 years), middle-aged (40–54 years), and older (55–76 years). The young group comprised 21 adults (12 female, 9 male) with a mean age of 30.4 years (SD=4.8), the middle-aged group comprised 29 adults (18 female, 11 male) with a mean age of 47.8 years (SD=4.3), and the older group comprised 29 adults (15 female, 14 male) with a mean age of 62.7 years (SD=7.2) (Tab. 1).
Mean (SD) Values for Peak Pinch Force (FPpeak), Peak Force Ratio (FRpeak), and Time Lag for Hand Used, Pinch Pattern, and Age
Inclusion criteria for the patients with peripheral nerve injury were: (1) having digital nerve injuries of the thumb and index finger, (2) having median nerve injury distal to wrist level, or (3) having digital replantation. The initial evaluation of the participants was performed at least 1 month after the operation for those who had type 1 and 2 injuries. For those with type 3 injuries, the initial evaluation was performed at least 3 months after the operation, at which time sufficient tensile strength had returned to the injured tendon. Nine patients (4 female, 5 male) with a mean age of 30.7 years (SD=12.1) and sensory disturbance in 11 hands who had undergone digital or median nerve repair were recruited for the study. Three individuals exhibited dominant hand injuries, 4 had nondominant hand injuries, and 2 had bilateral hand injuries. The mean duration from injury onset to the first evaluation was 9.7 months (SD=6.5). Prior to the study, each participant was informed of the experimental aims and procedures and signed a consent form approved by the Institutional Review Board of National Cheng Kung University Hospital.
Traditional Sensory Tests
Hand sensibility was evaluated using S2PD and M2PD tests and the SW monofilament test. The 2PD test is a widely used method of assessing tactile gnosis clinically. The SW monofilament test was used to measure the cutaneous pressure threshold.
Hand Function Test
The Purdue Pegboard Test was used to test the skillful controlled movement of small objects where the hand is primarily involved. Participants were asked to pick up pins, collars, and washers and put them correctly on a pegboard as quickly as they could. The test consisted of both unimanual and bimanual tasks. The scores were recorded 3 times for each group of tests.23
Experimental Procedure
Participants were requested to wash their hands with soap and water to remove any greasy substances on their thumb and fingertips before the measurements were taken. They then were asked to sit upright with their unsupported forearm extending forward. The pinch device was placed on a stable desk in front of each participant. They were instructed to pinch and lift the device using the pulps of the thumb and index finger (and the long finger for the 3-jaw chuck pinch pattern) to roughly 5 cm above the desktop and asked to hold the device in that position for about 5 seconds. Afterward, they were asked to lift the pinch device to a height of 30 cm above the desktop and to hold the device in that position. This cycle consisted of 2 parts: the stationary period and the moving period. The stationary period was defined as the static holding phase for a duration of 5 seconds. The moving period was defined as the lifting phase, lasting for 10 seconds. The duration of data collection of the entire cycle of movement was 15 seconds. Each participant was required to perform the task using both the palmar pinch and the 3-jaw chuck pinch pattern with both the dominant and nondominant hands in a random order. Three trials were repeated for each pinch pattern, with a 1-minute rest interval between trials. To reduce the variability in force production among the trials, the average of the 3 trials was used for analysis. The exerted force was recorded, and the force ratio between pinch force and load force was computed. The force parameters in the pinch-up-holding (PUH) test and the results of the Purdue Pegboard Test and traditional sensory tests were recorded before and after the sensory re-education program.
Data Processing and Analysis
Two time points were recorded during each required PUH test: (1) the maximum upward acceleration during a lifting task and (2) the peak pinch force (FPpeak) onset during the lifting phase. At these points, the pinch force and load of the interactive object were recorded and computed (Fig. 1). The FPpeak and the maximum load force (FLmax) that occurred during the PUH test were used to compute the peak force ratio (FRpeak) (ie, FPpeak:FLmax). This ratio revealed the ability of pinch force adjustment responsible for the inertial loads of the apparatus among the different phases of the pinch-up-holding activity. We analyzed the temporal factor to understand the precision in regard to time control. The time lag is defined here as the latency period between time 1 and time 2. It indicates the temporal coupling between the FPpeak and the FLmax during the lifting performance test. A custom-written Matlab program (MathWorks Inc, Natick, Massachusetts) was developed to determine the FPpeak and the FRpeak in the PUH test.
Sensory Re-education Protocol
Participants received the CERB program with the palmar pinch pattern for 10 to 15 minutes per session, 3 times per week, for 4 consecutive weeks. Before the execution of the biofeedback intervention, the therapist set up the target force range using the manual setting interface. The upper limit of the range of the target force ratio was determined and set at 94% of the FRpeak obtained from the affected hand at the initial evaluation. The lower boundary of the force ratio was set at 94% of the mean FRpeak from a normal database based on different age levels. The 94% FPpeak value was determined according to the results for the average nondominant hand producing 6% more excessive force compared with the dominant hand in order to complete the pinch lifting task obtained in our previous studies.11,24 Based on the motor relearning theory, the affected hand could be more accurately programmed to optimize force through repeated practice. Thus, we decided that this 6% difference in capability could be improved using the CERB prototype. The detected force in the requested PUH training task was compared with the target force level during the lifting phase (from a 5-cm height to a 30-cm height above desktop level) by a feedback loop. That is, the participants had a period of 10 seconds to correct the force ratio on the cues. Both visual and auditory feedback were assigned to warn the participants, and the scores for the hitting rates in the target range were shown to motivate the them.
Data Analysis
Statistical analyses were carried out using SPSS 17.0 software (SPSS Inc, Chicago, Illinois). As described in our hypothesis, we assumed that several parameters might influence the FRpeak and time lag while performing the pinch-up-holding task. In order to investigate these influences, we used standard descriptive statistical methods, including analysis of variance for repeated measures. Factors included age group (young, middle age, and older), pinch pattern (palmar pinch and 3-jaw chuck), and hand used (dominant or nondominant). The relative significance of the factors was determined based on comparisons made among them. In addition, the Wilcoxon signed rank test was used to analyze the difference in pinch force adjustment parameters and manual skills before and after the CERB training.
Role of the Funding Source
This work was supported by National Science Council grant NSC 97-2314-B-006-047-MY2, Taiwan.
Results
Computerized Evaluation and Biofeedback System Setup
The pinch apparatus hardware, together with a custom-made LabView interface, provided the computerized biofeedback system used in sensory evaluation and re-education. The computerized interface consisted of 2 parts: a manual settings panel and a real-time feedback display panel (Fig. 1). A manual settings panel allows clinicians to set the target force latitude, based on results from the participant's initial assessment. Participants were monitored while performing the PUH test during the training session, and each participant's force signal was instantly compared with the target force latitude via a feedback loop. Once the force output exceeded the target latitude, visual and auditory cues were displayed to trigger optimal motor strategy during training tasks.
Normal Database Comparison and Installation
The group means and standard deviations for FRpeak, FPpeak, and time lag, which were the averages of the multiple trials acquired from the apparatus indication for the influence of hand dominance, pinch pattern, and age, are listed in Table 1. The force parameters (ie, FPpeak and FRpeak) were significantly affected by hand dominance factors (FPpeak, P=.001; FRpeak, P=.001), pinch pattern (FPpeak, P=.000; FRpeak, P=.000), and age (FPpeak, P=.007; FRpeak, P=.005). No statistical significance was observed for either the effect of sex (FPpeak, P=.070; FRpeak, P=.069) or the interaction effect (P values ranged from .052 to .900). The force ratio is a sensitive parameter that determines the pinch efficiency during task execution. Figure 2 shows that there were significant differences in the force ratio among the 3 age groups under different conditions (P values ranged from .014 to .004 for different pinch patterns or using a different hand), except for when participants used the palmar pinch pattern with their nondominant hand (P=.066).
Effects of age on peak pinch force (FPpeak) for pinch task and hand dominance. FLmax=maximum load force. Asterisk indicates statistical significance.
The time lags obtained from the 79 volunteers were affected by hand dominance (P=.010) but were unaffected by pinch pattern (P=.781) and age (P=.826). When carrying out the palmar pinch pattern (Fig. 3), the dominant hand had greater timing control precision in pinch force adjustment than was the case for the nondominant hand (P=.005).
The effect of hand dominance on temporal control for different pinch tasks. FPpeak=peak pinch force, FLmax=maximum load force. Asterisk indicates statistical significance.
Effects of the CERB Prototype on Participants With Peripheral Nerve Injury
Compared with the force ratio of the palmar pinch pattern in the participants with normal hand sensation, the patient values (X̅=2.76, SD=0.66) were statistically higher than the control data (2.34–2.57). In addition, the FPpeak was higher in the participants with peripheral nerve injuries (Tabs. 1 and 2). Therefore, the re-education program was implemented for the participants with peripheral nerve injuries. Both discriminative and threshold measurements did not change significantly after the CERB training (Tab. 2). However, the participants with peripheral nerve injuries presented higher efficiency in adjusting pinch force (P=.004) during the PUH test and had better results on the Purdue Pegboard Test following the CERB training (P=.003). Nevertheless, the values for the time lag did not improve significantly (Tab. 2).
Sensory Status, Efficiency of Pinch Force Responding to Load Change With Palmar Pinch Pattern, and Manual Skills Before and After Computerized Evaluation and Re-education Biofeedback Training in the Patients With Peripheral Nerve Injuriesa
Discussion
Current clinical practices do not commonly utilize tools appropriate to functional sensibility assessment and related re-education intervention. Therefore, there is a troublesome gap between an understanding of sensibility impairment and the selection of remedial strategies to improve functional performance, which is a concern for clinicians and patients with functional sensibility deficiencies alike. Conventional sensory re-education programs are time- and manpower-consuming processes, and the lack of any quantitative index to evaluate the effects of intervention might be the most frustrating aspect of any treatment progression. To create a measurement and training system with an appropriate control interface and computational functions for sensorimotor assessment and intervention, we assembled an integrated computerized biofeedback and assessment system in the established pinch hardware and then incorporated the normal force ratio database into the system to provide additional reference values for clinical applications. The system provides functions to record and feed back information about the pinch force exerted by an individual, either with or without sensibility disturbance in the pinch-up-holding activity. This approach represents a more functional perspective than an examination conducted using conventional threshold and discriminative tests. In addition to benefiting from quantitative measurements, users can learn to monitor inappropriate force output and can further modify their pinch strategies using the visual or auditory feedbacks displayed by the system.
The establishment of a normal database is a prerequisite for the setup of clinical assessment and therapeutic tools. The collected normal range of force and temporal parameters installed in the system could be regarded as the reference values in a lifting task. With the use of the reference data, we can compare typical values corresponding with varying degrees of sensory impairment.
However, some studies have demonstrated that accurate functional sensory input is essential for precise pinch motion, which is needed for the many varied activities of daily living.25,26 Cole et al27 reported that one of the mechanisms of age-related changes in fingertip force modulation in a lifting task was the impaired cutaneous afferent encoding of skin-object frictional properties. In the current study, the average FRpeak obtained for the 3 age groups was greater than 2, which was larger than the values (1.77–1.98) for young adults obtained in our previous work.11 The reason for this difference might be that the mean age of the recruited participants in the previous work was 21.3 years, which was much younger than the young adult group (mean age=30.4 years) in this study. Increased pinch force also was observed in the middle-age and older age groups during the required performance. Similarly, older adults exhibited significantly higher force ratios with a slippery grip surface in previous studies.28,29 However, in these studies, the effect of pinch force modulation with different pinch patterns for different age groups was not investigated. The ratio between peak grip force output and the peak load force input is a very sensitive parameter; it was used to measure the efficiency of adjusting pinch force in executing functional tasks in a previous study, and was a key parameter in the present study.30
In this study, we found the FRpeak to be significantly affected by the age factor in both the 3-jaw chuck and palmar pinch patterns when the participants used their dominant hand (palmar pinch, P=.011; 3-jaw chuck, P=.014). However, statistically significant differences among the age groups were found only for the 3-jaw chuck pinch pattern when the participants used their nondominant hand (P=.004). The dominant hand is the primary manipulative extremity for performing activities of daily living; the results revealed that younger adults produced an efficient force scaling in performing a functional activity with either of the 2 pinch patterns.
These findings, however, show a trend toward decreasing adjusting ability in pinch force with increasing age for individuals applying the palmar pinch pattern (P=.066). We attributed the observed results for the nondominant hand to the palmar pinch pattern's relative instability and inefficiency for object handling resulting in participants in all 3 age groups paying greater attention and exerting a greater pinch force to prevent objects slipping from the digit pads during the lifting task.
The term “precision” often is restricted to grips in which a small object is held between the thumb's distal phalanx and the terminal volar pads of one or more fingers.31 Participants used the palmar pinch and 3-jaw chuck grip with each hand during the pinch-up-holding tasks in our study. Pinch pattern had a significant effect on force exertion for dynamic lifting tasks (P<.000). The 3-jaw chuck pattern involves the thumb being opposed to the fingers, thus enhancing the security of the grip. The orientation of third metacarpal head brings the palmar surface of the third proximal phalanx into opposition to the thumb, with flexion maximizing the potential contact area between the volar skin of the fingers and thumb. This orientation provides the advantage of efficient tool handling for the 3-jaw chuck grip.32 Prehensile pinch capability typically is quantified by force control. The results of our study suggest that the 3-jaw chuck grip allows an effective precision manipulation by the thumb and radial finger pads.
Additionally, our results showed FPpeak, FRpeak, and time lag to be significantly affected by hand dominance. The 79 participants with normal hand sensation were all right-hand dominant and were accustomed to performing precision tasks with the right hand. Therefore, they were unaccustomed to executing delicate activities with their nondominant hand. During the lifting phase, the nature of the lifting task is more dynamic and unpredictable. Through memory of previous manipulations, the dominant hand's motor planning is accurately programmed and significantly optimizes the force during lifting actions.33 A healthy pinch performance not only should include efficient force scaling, but also should provide precisely timed coupling between grip and load force profiles. The time lags between FPpeak and FLmax for the dominant and nondominant hands were 8.40 and 14.73 milliseconds, respectively, in this study.
These results are similar to those of the 2 previous works on this topic.34,35 Jin et al34 analyzed the effects of hand dominance on precision pinch performance in 16 individuals who were healthy and found that the time lags between the onset of grip and load forces were significantly higher in the dominant hand than in the nondominant hand. In addition, the time lags were 8.74 and 30.61 milliseconds for the dominant and nondominant hands, respectively, in the study by Iyengar et al.35 However, the time lag in adjusting the pinch force according to the actual load of the lifted object was unaffected by the factors of age and pinch pattern, and these results are similar to the findings of Cole et al.27 Westling and Johansson36 found that the time taken to adjust grip force, which is an event encoded by fast-adapting type II (FA-II) afferents throughout the hand and wrist, does not increase with age. Cole et al27 also were unable to demonstrate an age-related sensory decline that might affect precision in timing adjustment in a “nonvisual” situation.
The adjustment of pinch force with actual load has been demonstrated using an experimental forward internal model,37,38 and the cerebellum has been shown by functional magnetic resonance imaging to be the most likely location for forward models to be stored.39 Generally, the cerebellum plays an important role in temporal coupling of motor control38,40; therefore, using an efference copy of previous actions, participants in this study were able to supply timely adjustment to pinch force output, with no apparent difference among age groups.
The participants with impaired sensation of the hand in this study exhibited a noticeable training effect, not only on the pinch force modulation but also in unimanual and bimanual skill on the Purdue Pegboard Test, although there was no significant improvement in the results of the traditional sensibility examinations made during the intervention phase. In view of these results, this novel CERB prototype could monitor the pinch force adjustment to present the index of functional sensibility and could be used as an intervention strategy to facilitate selective movement control that would enhance the function of an affected hand. The results supported the hypothesis that clinical application of the CERB prototype for patients with sensory deficiency could promote the functional performance of the hand. The participants were able to transfer the newly learned strategy to manual hand activities. They did not show improvement in the assembly task subtest, which might have been due to the imperfections in the movement ability of the distal interphalangeal joint, limiting the performance for picking up the thin, tiny washers used in this study. Hence, the purpose of sensory reeducation is not only to educate the patient to interpret sensory information correctly, but also to promote the sensorimotor control of the hand. Although the numbers of recruited participants in the preliminary application were relatively few, we did demonstrate that the CERB prototype represents a significant effect on actual hand capability for patients with impaired sensibility.
In this study, the design for 2 lifting heights (5 cm and 30 cm above desk top level) in the testing procedure was different from that of other experiments that have analyzed pinch force control in the hands. The contribution of 2 lifting heights is to evaluate the FPpeak, FRpeak, and time lag parameters accurately according to the inertial loads of the pinch apparatus. Because there was a wide range of capabilities in the recruited participants, including memory from previous manipulative experience and muscle strength and cognition,41 there were large variations in force production among them when they lacked understanding of the mechanical properties of the object. When holding the apparatus at the height of 5 cm above the desk, the participants were able to become familiar with the characteristics of the apparatus, including the weight, texture, and shape. After that, they had the ability to produce forces with small errors.
However, this study still has limitations with regard to additional research. A limitation of our study is its lack of measurement and representation of changes in the frictional properties of the skin of patients. The purpose of this study was to educate patients through the CERB prototype to have better attendance to sensory cues so that the brain could generate more appropriate motor commands. However, the friction between the skin and the objects used varied widely according to personal and environmental factors. That is, training to lower the patient's pinch force might lead to a risk of object slippage due to changes in skin friction following nerve injuries. Therefore, the setting of the lower boundary of the force ratio for the training course of CERB preferably should be based directly on the individual's slip force (the minimum pinch force to avoid slip) in the future. In addition, quantitative sensory testing for patients with nerve injuries should be conducted using validated instruments; however, the 2PD test has been reported not to be sufficiently responsive with regard to detection of tactile spatial discrimination.42
In future research, gap detection and grating resolution of psychophysical measurements could be used to understand the actual perception regarding patient tactile spatial acuity. In this experiment, the training results for patients with peripheral nerve damage indicate that the FPpeak and FRpeak improve toward normal with the CERB system, but the temporal lag does not significantly change. The possible reason is that the training improves the feedforward control but not feedback control for the short-duration cohort study. Future research conducted with a long-term follow-up will help us to comprehend the training mechanism of the CERB on the precision pinch performance. Moreover, training effects of using a feedback system to practice with bilateral hands was not investigated in this study. In future research, authors could investigate the effects of both bilateral and unilateral training.
Conclusions
Using our experimental results, we developed a conjunct system suited to both evaluating and restoring sensorimotor function in patients with impaired sensibility of the hands. The force and temporal parameters obtained in the pinch-up-holding task for different age groups and hands (dominant and nondominant) could be used as reference data for comparison with patients with central or peripheral nerve injuries. We found that pinch pattern significantly affected efficiency in dynamic hand manipulations; this finding suggests that using an alternate pinch pattern results in suboptimal force control during tool handling. In addition, by providing auditory and visual feedback cues, the CERB system can be used as an alternative treatment for the enhancement of hand function of patients with impaired hand sensibility.
Footnotes
Professor Chiu, Professor Su, and Professor Kuo carried out the establishment of the evaluation and biofeedback system. Ms Hsu and Professor Kuo were the main contributors of the study design, data collection, and clinical assessments. Ms Hsu, Professor Jou, and Professor Kuo participated in the data analysis and interpretation. Ms Hsu, Professor Lin, and Professor Kuo helped to draft the manuscript. All authors read and approved the contents and format of the final manuscript.
The study was approved by the Institutional Review Board of National Cheng Kung University Hospital.
This work was supported by National Science Council grant NSC 97-2314-B-006-047-MY2, Taiwan.
- Received February 5, 2012.
- Accepted September 17, 2012.
- © 2013 American Physical Therapy Association
References
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