Quantitative assessment of simultaneous capacitive and resistive plantar pressure measurements during walking.

Plantar pressure data were collected simultaneously, during walking, from capacitive and resistive in-shoe pressure measurement systems. Overall mean peak pressure recordings from the resistive system were 32%, 20% and 14% greater than recordings from the capacitive system, at the heel, central metatarsal heads, and great toe, respectively. Placement of one system's insoles above or below the other's somewhat affected peak pressure measurements from both systems, while calibration via air bladder or single limb standing techniques somewhat affected resistive measurements as well. Capacitive measurement variability was 60%, 20% and 22% lower than resistive measurement variability, at the heel, central metatarsal heads, and great toe, respectively. Both systems tended to exhibit greater variability when capacitive insoles were placed above resistive insoles; however, the effects on variability of the experimental insole arrangements were well overshadowed by the overall variability differences between systems.

A computer analysis of reflex eyelid motion in normal subjects and in facial neuropathy.

OBJECTIVE: To demonstrate how computerized eyelid motion analysis can quantify the human reflex blink. DESIGN: Seventeen normal subjects and 10 patients with unilateral facial nerve paralysis were analyzed. BACKGROUND: Eyelid closure is currently evaluated by systems primarily designed to assess lower/midfacial movements. The methods are subjective, difficult to reproduce, and measure only volitional closure. Reflex closure is responsible for eye hydration, and its evaluation demands dynamic analysis. METHODS: A 60Hz video camera incorporated into a helmet was used to analyze blinking. Reflective markers on the forehead and eyelids allowed for the dynamic measurement of the reflex blink. Eyelid displacement, velocity and acceleration were calculated. The degree of synchrony between bilateral blinks was also determined. RESULTS: This study demonstrates that video motion analysis can describe normal and altered eyelid motions in a quantifiable manner. CONCLUSIONS: To our knowledge, this is the first study to measure dynamic reflex blinks. Eyelid closure may now be evaluated in kinematic terms. This technique could increase understanding of eyelid motion and permit more accurate evaluation of eyelid function. Dynamic eyelid evaluation has immediate applications in the treatment of facial palsy affecting the reflex blink. Relevance No method has been developed that objectively quantifies dynamic eyelid closure. Methods currently in use evaluate only volitional eyelid closure, and are based on direct and indirect observer assessments. These methods are subjective and are incapable of analyzing dynamic eyelid movements, which are critical to maintenance of corneal hydration and comfort. A system that quantifies eyelid kinematics can provide a functional analysis of blink disorders and an objective evaluation of their treatment(s).

Wavelet-based noise removal for biomechanical signals: a comparative study.

The purpose of this paper is to present wavelet-based noise removal (WBNR) techniques to remove noise from biomechanical acceleration signals obtained from numerical differentiation of displacement data. Manual and semiautomatic methods were used to determine thresholds for both orthogonal and biorthogonal filters. This study also compares the performance of WBNR approaches with four automatic conventional noise removal techniques used in biomechanics. The conclusion of this work is that WBNR techniques are very effective in removing noise from differentiated signals with sharp transients while leaving these transients intact. For biomechanical signals with certain characteristics, WBNR techniques perform better than conventional methods, as indicated by quantitative merit measures.

A deficient anterior cruciate ligament does not lead to quadriceps avoidance gait.

Without an intact anterior cruciate ligament (ACL) to resist anterior tibial translation, it is commonly believed that ACL-deficient patients employ alterations in walking. Although there is no consensus in the literature about the specific kinematic and kinetic adaptations in these patients with ACL tears, the gait adaptation of quadriceps avoidance is perhaps the one most popularized. The purpose of our study was to determine whether quadriceps avoidance is common in patients with ACL-deficiency. We used a video-based motion analysis system and surface electromyography (EMG) to study 18 patients with ACL-deficiency. All patients demonstrated an internal knee extension moment during early mid-stance (similar to normal subjects). Quadriceps EMG activity was noted throughout most of stance. No patients demonstrated an internal knee flexion moment, a decreased internal knee extension moment or a decreased duration of quadriceps EMG activity during stance. The findings of this study would suggest that quadriceps avoidance as a gait adaptation in ACL-deficient patients may be less common than previously reported.

A demonstration of validity of 3-D video motion analysis method for measuring finger flexion and extension.

This study demonstrates the validity of using 3-D video motion analysis to measure hand motion. Several researchers have devised ingenious methods to study normal and abnormal hand movements. Although very helpful, these earlier studies are static representations of a dynamic phenomenon. Despite the many studies of hand motion using scientifically impeccable techniques, little is known about digital motion, and there are still few researchers investigating dynamic three-dimensional motion of the hand. Results from a three-camera video motion analysis system were compared to those from the "gold standard", 2-D lateral view fluoroscopy. We used these two methods to record hand motion simultaneously during unrestricted flexion and extension of the index finger of the dominant hand in 6 neurologically normal, healthy volunteers. After collection and post-processing, the waveforms of the PIP, DIP and MCP joint angles were compared using the adjusted coefficient of multiple determination (R2(a), or CMD). The mean CMD values for the MCP, PIP and DIP joint angle waveforms were 0.96, 0.98 and 0.94, respectively, suggesting a close similarity between motion of comparable joints analyzed by the 2-D and 3-D methods. This shows that the method of 3-D motion analysis is capable of accurately quantifying digital joint motion. It is anticipated that 3-D motion analysis, in addition to being used as a research tool, will also have clinical applications such as surgical planning in neuromuscular disorders and the documentation of abnormal motion in many other pathological hand conditions.

The motion path of the digits.

This study investigates whether the path taken by the fingertips of the human hand during unrestricted flexion and extension follows a precise mathematical pattern: an equiangular spiral. Eight normal subjects participated in the study. Subjects performed numerous flexion and extension trials at a random speed. Motion was recorded by a 6-camera, 3-dimensional motion analysis system with 24 retroreflective markers affixed to the dominant hand at predetermined locations. Four hundred eighty flexion-extension arcs were analyzed. We used the coefficient of multiple determination to compare the flexion and extension motion arc of each finger to an equiangular spiral curve derived mathematically. Our results indicate that the path of the hand during flexion and extension closely follows the path of an equiangular spiral with the coefficient of multiple determination values consistently above 0.95.

The initiation and sequence of digital joint motion. A three-dimensional motion analysis.

We studied the initiation and sequence of digital joint motion during unrestricted flexion and extension using a 3-D motion analysis of all fingers moving simultaneously. Our results showed that motion started in a single joint in 83%, of flexion and 80%, of extension cycles. The DIP joint initiated flexion and extension in the index, middle, and ring fingers, but in the little finger, flexion started in the PIP joint, and extension in the MP joint. The two most frequent sequences of joint movement during flexion of the three radial fingers were DIP-PIP-MP and PIP-DIP-MP. The two most frequent sequences during extension of the three radial fingers were DIP-MP-PIP followed by DIP-MP/PIP. In the little finger, however, the most frequent sequences during flexion were PIP-DIP-MP followed by DIP-PIP-MP and during extension, DIP-MP/PIP followed by PIP/DIP-MP.