Clinical Tests for Predicting Fallers Among Ambulatory Patients with Amyotrophic Lateral Sclerosis: A Preliminary Cohort Study

Background: Few studies have examined falls and their predictors in patients with amyotrophic lateral sclerosis (ALS). Objective: The aim of this study was to survey fall incidence and to identify variables predicting the presence or absence of falls occurring within 3 months after discharge of patients with ALS from hospital. Methods: The following variables were evaluated in 14 patients with ALS: timed up and go test (TUG), functional reach test, 10-m comfortable gait speed, single-leg stance time, manual muscle test (MMT) scores for the lower limb, total modified Ashworth scale score for the lower limbs, fear of falling, and pull test score. The primary outcome variable was the occurrence of a fall within 3 months after discharge. The fall rate was calculated based on fall record forms. The specific circumstances of each fall were also recorded. Univariate and multiple regression analyses were used to identify fall predictors. Results: Seven of the 14 ALS patients (50%) experienced a fall within 3 months. Five fallers reported experiencing a fall that had caused injury, and three reported experiencing a fall that had required a hospital visit. Univariate logistic regression analysis identified TUG time, gait speed and MMT of the ankle dorsiflexors as factors associated with falls (p = 0.02–0.04). Multiple linear regression analysis of fall numbers identified age and TUG time as predictor models (p = 0.03). Conclusion: TUG time and MMT of ankle dorsiflexors may help predict falls in ALS patients. Validation studies in larger cohorts are needed.

Effects of tonic muscle pain on fusimotor control of human muscle spindles during isometric ankle dorsiflexion

Studies on anesthetized animals have revealed that nociceptors can excite fusimotor neurons and thereby change the sensitivity of muscle spindles to stretch; such nociceptive reflexes have been suggested to underlie the mechanisms that lead to chronic musculoskeletal pain syndromes. However, the validity of the “vicious cycle” hypothesis in humans has yielded results contrasting with those found in animals. Given that spindle firing rates are much lower in humans than in animals, it is possible that some of the discrepancies between human experimental data and those obtained in animals could be explained by differences in background fusimotor drive when the leg muscles are relaxed. We examined the effects of tonic muscle pain during voluntary contractions of the ankle dorsiflexors. Unitary recordings were obtained from 10 fusimotor-driven muscle spindle afferents (6 primary, 4 secondary) supplying the ankle dorsiflexors via a microelectrode inserted percutaneously into the common peroneal nerve. A series of 1-min weak contractions was performed at rest and during 1 h of muscle pain induced by intramuscular infusion of 5% hypertonic saline into the tibialis anterior muscle. We did not observe any statistically significant increases in muscle spindle firing rates of six afferents followed during tonic muscle pain, although discharge variability increased slightly. Furthermore, a participant’s capacity to maintain a constant level of force, while relying on proprioceptive feedback in the absence of visual feedback, was not compromised during pain. We conclude that nociceptive inputs from contracting muscle do not excite fusimotor neurons during voluntary isometric contractions in humans. NEW & NOTEWORTHY Data obtained in the cat have shown that muscle pain causes a marked increase in the firing of muscle spindles, attributed to a nociceptor-driven fusimotor reflex. However, our studies of muscle spindles in relaxed leg muscles failed to find any effect on spindle discharge. Here we showed that experimental muscle pain failed to increase the firing of muscle spindle afferents during weak voluntary contractions, when fusimotor drive sufficient to increase their firing is present.

Design of Semirigid Wearable Devices Based on Skin Strain Analysis

Nowadays, both usability and comfort play a key role in the development of medical and wearable products. When designing any device that is in contact with the human body, the mechanical behavior of the embraced soft tissue must be known. The unavoidable displacement of the soft tissue during motion may lead to discomfort and, thus, the removal of the wearable product. This paper presents a new methodology to design and test a wearable device based on the measurement of the dynamic skin strain field. Furthermore, from this field, the anatomical lines with minimum strain (lines of nonextension (LoNEs)) are calculated to design the structural parts of the wearable device. With this new criterion, the resulting product is not only optimized to reduce the friction in skin-device interface, but fully personalized to the patient's morphology and motion. The methodology is applied to the design of an ankle-foot wearable orthosis for subjects with ankle dorsiflexors muscles weakness due to nervous system disorders. The results confirm that the use of LoNEs may benefit the design of products with a high interaction with the skin.

CLINICAL MUSCULAR EVALUATION IN PATELLOFEMORAL PAIN SYNDROME

ABSTRACT Objective: To define a profile of the muscle groups affected by patellofemoral pain syndrome (PFPS) to determine a pattern of functional weaknesses around the knee. Methods: Sixty-three female patients were randomly selected, and 17 included in this study, receiving a clinical evaluation with pre-established protocol which evaluated the quadriceps, abductors, range of motion in the internal rotators and ankle dorsiflexors, pelvic tilt, and dynamic valgus. Results: Losses were seen in abductor strength and ankle dorsiflexor range of motion in comparison with the contralateral limb (0.031 and 0.040, respectively). There was a loss of quadriceps strength and decreased amplitude of internal hip rotation when compared to the Kujala score (0.032 and 0.002, respectively). Dynamic valgus and pelvic fall were greater in comparison with the Kujala score (0.668 and 0.567, respectively). Conclusion: Clinical evaluation showed deficits in the quadriceps and abductor muscle groups, as well as decreased range of motion in the internal hip rotators and ankle dorsiflexors and increased dynamic valgus and pelvic drop. Level of Evidence IV; Case series.