Developing and Establishing Biomechanical Variables as Risk Biomarkers for Preventable Gait-Related Falls and Assessment of Intervention Effectiveness.

The purpose of this review is to position the emerging clinical promise of validating and implementing biomechanical biomarkers of falls in fall prevention interventions. The review is framed in the desirability of blunting the effects of the rapidly growing population of older adults with regard to the number of falls, their related injuries, and health care costs. We propose that biomechanical risk biomarkers may be derived from systematic study of the responses to treadmill-delivered perturbations to both identify individuals with a risk of specific types of falls, such as trips and slips as well as quantifying the effectiveness of interventions designed to reduce that risk. The review follows the evidence derived using a specific public health approach and the published biomedical literature that supports trunk kinematics as a biomarker as having met many of the criteria for a biomarker for trip-specific falls. Whereas, the efficacy of perturbation training to reduce slip-related falls by older adults appears to have been confirmed, its effectiveness presently remains an open and important question. There is a dearth of data related to the efficacy and effectiveness of perturbation training to reduce falls to the side falls by older adults. At present, efforts to characterize the extent to which perturbation training can reduce falls and translate the approaches to the clinic represents an important research opportunity.

Evaluation of cephalexin failure rates in morbidly obese patients with cellulitis.

WHAT IS KNOWN AND OBJECTIVE: Identification of adequate antimicrobial dosing regimens for morbidly obese patients is essential given the simultaneous increase in morbid obesity and cellulitis prevalence in recent years. Insufficient data currently exist to describe the effectiveness of extrapolating traditional antibiotic dosing strategies to morbidly obese patients with cellulitis. The primary objective of this study was to compare therapeutic failure rates in non-obese and morbidly obese patients with cellulitis when treated with cephalexin at standard dosing. METHODS: This was a single-centre, retrospective cohort analysis. Adult patients hospitalized or under inpatient observation at a 1265-bed academic medical centre who received cephalexin monotherapy for non-purulent cellulitis from 2005 to 2015 were evaluated for inclusion. Patients were divided into two cohorts based on body mass index (BMI), where BMI <30 kg/m(2) was defined as non-obese and BMI ≥40 kg/m(2) as morbidly obese. Patients with critical risk factors for purulent or polymicrobial cellulitis were excluded. The primary outcome, therapeutic failure, was defined as a need for extended or additional antimicrobial therapy, surgical intervention, emergency department visit, or re-hospitalization within two to thirty days after cephalexin initiation. RESULTS AND DISCUSSION: A total of 94 patients (69 non-obese and 25 morbidly obese) met inclusion and exclusion criteria, which was below the estimated sample size needed to reach desired power. The rate of therapeutic failure in the morbidly obese group was similar to the non-obese group (20% vs. 14·5%, P = 0·53). Patients most commonly had extended or additional antibiotics prescribed in response to therapeutic failure with cephalexin. WHAT IS NEW AND CONCLUSION: Cephalexin failure rates for cellulitis did not differ statistically between morbidly obese and non-obese patients. The underpowered nature of this study is a limitation. Until further study with a larger sample size is completed, empiric adjustment of cephalexin dosing based solely on BMI may not be necessary.

Step detection using multi- versus single tri-axial accelerometer-based systems.

Multiple sensors are often considered necessary for increased step count accuracy. However, subject adherence to device-wear increases using a minimal number of activity monitors (AMs). The study aims were to determine and compare the validity of using multiple AMs versus a single AM to detect steps by comparison to video using a modification of an algorithm previously developed for a four-accelerometer AM system capable, unlike other algorithms, of accurate step detection for gait velocities as low as 0.1 m s(-1). Twelve healthy adults wore ankle, thigh and waist AMs while performing walking/jogging trials at gait velocities from 0.1-4.8 m s(-1) and a simulated free-living dynamic activities protocol. Nineteen older adults wore ankle and waist AMs while walking at velocities from 0.5-2.0 m s(-1). As little as one AM (thigh or waist) accurately detected steps for velocities >0.5 m s(-1). A single ankle AM accurately detected steps for velocities ⩾0.1 m s(-1). Only the thigh AM could not accurately detect steps during the dynamic activities. Only the thigh-ankle combination or single waist AM could accurately distinguish between walking and jogging steps. These laboratory-based results suggest that the presented algorithm can accurately detect steps in a free-living environment using only one ankle or waist AM.

Dynamic balance assessment during gait in spinal pathologies - a literature review.

UNLABELLED: The role of the spine as a gait stabilizer is essential. Dynamic assessment, while walking, might provide complementary data to improve spinal deformity management. The aim of this paper was to review spine dynamic behavior and the various methods that have been used to assess gait dynamic balance in order to explore the consequences of spinal deformities while walking. A review was performed by obtaining publications from five electronic databases. All papers reporting pathological or non-pathological spine dynamic behavior during gait and dynamic balance assessment methods were included. Sixty articles were selected. Results varied widely according to pathologies, study conditions, and balance assessment techniques. Three methods assessing dynamic stability during gait were identified: local-orbital dynamic stability, tri-axial accelerometry, and dynamic stability margin. Data from conventional gait analysis techniques were established essentially for scoliosis and low back pain, but they do not assess specific consequences on gait dynamic balance. Three techniques investigate gait dynamic balance and have been validated in normal subjects. Further investigations need to be performed for validation in spinal pathologies as well as the value for clinical practice. LEVEL OF EVIDENCE: Level IV.

Use of a Poroelastic Model to Predict Intramuscular Pressure.

Measurement of individual muscle tension in a clinical setting has yet to be achieved. Previous investigators have suggested that the tension in skeletal muscle, comprised of approximately 70% fluid, could be determined using interstitial muscle fluid pressure (IMP). A computational model is needed to aid in understanding IMP distribution in muscles of varying geometry and contractile states without exhaustive testing. The first aim of this study was to determine a set of transversely isotropic material properties (i.e., permeability, relaxed modulus, and drained Poisson's ratio) for excised skeletal muscle using inverse finite element analysis with a poroelastic constitutive formulation on tension data from either longitudinal or transverse uniaxial load-relaxation tests of skeletal muscle tissue. The second aim was to compare pore pressure estimated from a model to experimental pressure measurements to assess its ability to accurately predict IMP. Results of this study indicated that skeletal muscle was transversely isotropic under load-relaxation as demonstrated by significant differences in the drained Poisson's ratio. It was also noted that the drained Poisson's ratios under both longitudinal and transverse loading were negative in these tests of excised muscle tissue. Pore pressure calculated with this model provided a good prediction of the development of IMP. These results point to the benefit of using a poroelastic model of skeletal muscle to predict IMP.

Loads on the uprights of a knee-ankle-foot orthosis.

BACKGROUND: Objective design criteria for orthotic components is lacking. This paucity of data results in prescription guidelines based on assumptions or practitioners' past experience, and the potential for incorrectly designed components. The purpose of this study was to directly measure loads on the knee joint of a knee-ankle-foot orthosis. STUDY DESIGN: Case series. CASE DESCRIPTION AND METHODS: Three subjects who had been prescribed a knee-ankle-foot orthosis for quadriceps weakness underwent gait analysis and orthotic upright load data collection. A load sensor to measure the three force and three moment components was used in place of the lateral knee joint while the subjects walked in three knee flexion positions. FINDINGS AND OUTCOMES: Forces were highest in compression and moments were greatest in the sagittal plane. The kinetics did not increase solely with patient weight. There was substantial variability between subjects. CONCLUSIONS: This data will help guide orthotic component design and prescription guidelines. Knowledge of loading conditions will lead to more optimal orthotic intervention for patients and increased patient satisfaction. CLINICAL RELEVANCE: This study is one of the first to directly measure loads on the upright of a KAFO. These data provide objective targets for engineering design. The data from this small case series can also be used to establish guidelines for patient device selection.

Gait patterns of patients with inclusion body myositis.

Inclusion body myositis (IBM) is a progressive, inflammatory muscle disease that is known to cause quadriceps weakness and knee buckling during gait. This is the first known report of gait characteristics in patients with IBM. Nine subjects with IBM and quadriceps weakness underwent gait analysis and quantitative strength testing. A wide range of strength and gait abilities were present in the subject group. Subjects with stronger knee extensors exhibited nearly normal sagittal knee kinematics and kinetics. As quadriceps strength decreased, kinematic and kinetic patterns were increasingly abnormal. Exceptions to this pattern could be explained by examining strength at adjacent joints. Gait analysis and strength testing is a helpful tool in evaluating the functional status of this population and aiding in determination of the needs for interventions such as assistive devices.

Short-term repeatability of joint space width measurements using a magnetic resonance imaging compatible knee positioning device.

The purpose of this study was to evaluate a magnetic resonance imaging (MRI) compatible knee positioning device to aid in minimizing intratechnologist and intertechnologist differences of minimum joint space width (JSW) measurements. Five subjects were scanned by two separate technologists, with and without an MRI-compatible positioning device. A semi-automated program calculated the minimum JSW of the tibiofemoral and patellofemoral joints. The scan-to-scan repeatability was evaluated from measurements between serial scans without subject repositioning, and the intratechnologist and intertechnologist repeatabilities were evaluated when the subject was removed from the magnet and repositioned by an individual technologist. The root mean square (RMS) error of the JSW measurements was also calculated. All measures of scan-to-scan repeatability and intratechnologist repeatability were unchanged with the MRI-compatible positioning device. The intertechnologist repeatability decreased from 0.70 to 0.42 mm, and the RMS error was significantly reduced (P = 0.0006) from 0.26 to 0.15 mm for the tibiofemoral joint. The variability of patellofemoral JSW measurements increased when using the positioning device; however, the increases were not statistically significant. The intertechnologist repeatability increased from 1.55 to 1.79 mm, and the RMS error increased from 0.58 to 0.73 mm. The MRI-compatible positioning device was successful at reducing JSW measurement variability at the tibiofemoral joint. The increase in measurement variability at the patellofemoral joint may be due to local incongruities of the articular surfaces. An MRI-compatible positioning device may be beneficial for quantitative longitudinal studies evaluating knee joint health.

Replacement with GABAergic steroid precursors restores the acute ethanol withdrawal profile in adrenalectomy/gonadectomy mice.

The neurosteroid allopregnanolone (ALLO) is a progesterone metabolite that is one of a family of neuroactive steroids (NAS) that are potent positive allosteric modulators of gamma-aminobutyric acid(A) (GABA(A)) receptors. These GABAergic NAS are produced peripherally (in the adrenals and gonads) and centrally in the brain. Peripherally produced NAS modulate some effects of ethanol intoxication (e.g., anxiolytic, antidepressant, and anticonvulsant effects) in rodents. We have found that NAS also may be involved in the rebound neural hyperexcitability following a high ethanol dose. Removal of the adrenals and gonads (ADX/GDX) increased withdrawal severity following 4 g/kg ethanol, as measured by handling-induced convulsions (HICs) in male and female DBA/2J mice. NAS are produced through the metabolism of progesterone (PROG), deoxycorticosterone (DOC), or testosterone, which can be blocked with the administration of finasteride (FIN), a 5alpha-reductase enzyme inhibitor. The current investigation was undertaken to clarify the step(s) in the biosynthetic NAS pathway that were sufficient to restore the acute ethanol withdrawal profile in ADX/GDX mice to that seen in intact animals. Male and female DBA/2J mice underwent ADX/GDX or SHAM surgery. After recovery, separate groups of animals were administered PROG, DOC, PROG+FIN, DOC+FIN, FIN, ALLO, ganaxalone (a synthetic ALLO derivative), corticosterone, or vehicle. Animals were then administered a 4 g/kg ethanol dose and allowed to undergo withdrawal. HICs were measured for 12 h and again at 24 h. The results indicate that replacement with PROG and DOC restored the withdrawal profile in ADX/GDX animals to SHAM levels, and that this effect was blocked with co-administration of FIN. Administration of FIN alone increased the withdrawal profile in both SHAM and ADX/GDX males. These findings indicate that the increase in acute withdrawal severity after ADX/GDX may be due to the loss of GABAergic NAS, providing insight into the contribution of endogenous GABAergic NAS to ethanol withdrawal severity.

Psychogenic non-epileptic seizures, anticipatory grief and limited access to medical care.

Psychogenic non-epileptic seizures (PNES) in the context of meningoencephalitis can occur with sufficient stressors. Video-EEG is a critical diagnostic tool in such complex cases. Once the diagnosis of PNES is confirmed by video-EEG, psychiatric consultation with psychotherapeutic intervention to address underlying psychopathology and specific stressors that led to these conversion symptoms is required. Clinicians need to understand the importance of cultural themes, including the economics of healthcare, and anticipatory grief as causative stressors in pseudoseizures.

Constitutive modeling of skeletal muscle tissue with an explicit strain-energy function.

While much work has previously been done in the modeling of skeletal muscle, no model has, to date, been developed that describes the mechanical behavior with an explicit strain-energy function associated with the active response of skeletal muscle tissue. A model is presented herein that has been developed to accommodate this design consideration using a robust dynamical approach. The model shows excellent agreement with a previously published model of both the active and passive length-tension properties of skeletal muscle.

Misdirection of regenerating motor axons after nerve injury and repair in the rat sciatic nerve model.

Misdirection of regenerating axons is one of the factors that can explain the poor results often found after nerve injury and repair. In this study, we quantified the degree of misdirection and the effect on recovery of function after different types of nerve injury and repair in the rat sciatic nerve model; crush injury, direct coaptation, and autograft repair. Sequential tracing with retrograde labeling of the peroneal nerve before and 8 weeks after nerve injury and repair was performed to quantify the accuracy of motor axon regeneration. Digital video analysis of ankle motion was used to investigate the recovery of function. In addition, serial compound action potential recordings and nerve and muscle morphometry were performed. In our study, accuracy of motor axon regeneration was found to be limited; only 71% (+/-4.9%) of the peroneal motoneurons were correctly directed 2 months after sciatic crush injury, 42% (+/-4.2%) after direct coaptation, and 25% (+/-6.6%) after autograft repair. Recovery of ankle motion was incomplete after all types of nerve injury and repair and demonstrated a disturbed balance of ankle plantar and dorsiflexion. The number of motoneurons from which axons had regenerated was not significantly different from normal. The number of myelinated axons was significantly increased distal to the site of injury. Misdirection of regenerating motor axons is a major factor in the poor recovery of nerves that innervate different muscles. The results of this study can be used as basis for developing new nerve repair techniques that may improve the accuracy of regeneration.

Gait and balance of transfemoral amputees using passive mechanical and microprocessor-controlled prosthetic knees.

BACKGROUND: Microprocessor-controlled knee joints appeared on the market a decade ago. These joints are more sophisticated and more expensive than mechanical ones. The literature is contradictory regarding changes in gait and balance when using these sophisticated devices. METHODS: This study employed a crossover design to assess the comparative performance of a passive mechanical knee prosthesis compared to a microprocessor-controlled knee joint in 15 subjects with an above-knee amputation. Objective measurements of gait and balance were obtained. RESULTS: Subjects demonstrated significantly improved gait characteristics after receiving the microprocessor-controlled prosthetic knee joint (p<0.01). Improvements in gait were a transition from a hyperextended knee to a flexed knee during loading response which resulted in a change from an internal knee flexor moment to a knee extensor moment. The participants' balance also improved (p<0.01). All conditions of the Sensory Organization Test (SOT) demonstrated improvements in equilibrium score. The composite score also increased. CONCLUSIONS: Transfemoral amputees using a microprocessor-controlled knee have significant improvements in gait and balance.

Clinical evaluation of T2 values of patellar cartilage in patients with osteoarthritis.

OBJECTIVE: The transverse relaxation time constant, T2, of articular cartilage has been proposed as a biomarker for osteoarthritis (OA). Previous studies have not clearly defined the relationship between cartilage T2 values and clinical methods of grading OA or known factors associated with OA. This study compared T2 values of patellar cartilage grouped by radiographic stage of patello-femoral OA and by body mass index (BMI). METHODS: T2 values of patellar cartilage were calculated for 113 subjects using images acquired on a 1.5 T clinical scanner. Radiographs of the patello-femoral joint were graded for OA grading using the Kellgren-Lawrence scale. RESULTS: No differences of T2 values were found across the stages of OA (P = 0.25), but the factor of BMI did have a significant effect (P < 0.0001) on T2 value. CONCLUSIONS: The results indicate the T2 values are not sensitive to changes in radiographic stages of OA. In addition, differences of T2 values with BMI signify structural changes occurring within the patello-femoral joint and that BMI may be considered a factor for a potential increase of T2 values. Future studies comparing different OA grading methods with T2 mapping may highlight the sensitivity of T2 mapping in a clinical setting.

Changes in gait associated with acute stage II posterior tibial tendon dysfunction.

The purpose of this study was to examine differences in gait mechanics between patients with acute stage II PTTD and healthy volunteers. Hindfoot and midfoot kinematics, plantar foot pressures and electromyographic (EMG) activity of the posterior tibialis, gastrocnemius, anterior tibialis and the peroneals were measured in five patients with acute stage II PTTD. Kinematics and kinetics were compared to a database of 20 healthy volunteers. EMG and plantar pressure data were obtained from five healthy volunteers. Hindfoot moments and powers were also calculated. The center of pressure excursion index (CPEI) was calculated from the plantar pressures. Significant differences were observed between the two groups, which confirmed clinical observations. Limited hindfoot eversion and increased midfoot external rotation occurred during the first and third rockers. The EMG data suggested that tendon dysfunction in the posterior tibialis is associated with compensatory activity, not only in its antagonists (the peroneals), but also in the anterior tibialis and the gastrocnemius. These data suggest that non-operative treatment of patients with PTTD should consider minimizing the activity of the posterior tibialis as well as the peroneals, the anterior tibialis and the gastrocnemius.

Semi-automated digital image analysis of joint space width in knee radiographs.

OBJECTIVE: To design a semi-automated program to measure the minimum tibiofemoral joint space width (JSW) of knee radiographs. DESIGN: Bilateral knee radiographs were obtained twice within a 2 week period from 34 asymptomatic research participants. Radiographic images were analyzed to report both the variability of the image analysis program and the reproducibility of JSW measurements within a 2 week period. In addition, the results were compared with minimum JSW measurements read manually by an experienced musculoskeletal radiologist. RESULTS: The variability of the image analysis program was shown to be within one pixel. The results showed that reproducibility was better with the automated method. In addition, the manual method measured a greater minimum JSW than the automated method. There was no significant difference in between-day measurements. There was a significant difference reported between the automated and manual minimum JSW measurements. CONCLUSION: A novel semi-automated method for measurement of JSW has been developed.

Modafinil in sports: ethical considerations.

Performance enhancing agents are prohibited in athletic competition so that only athletic skills can determine outcomes. Modafinil is a novel non-addicting psychostimulant approved for treatment of narcolepsy. Does its use, especially for medical indications, violate the Olympic Movement Anti-Doping Code? This is discussed with reference to a current high profile case.

A kinematic method to calculate the workspace of the trapeziometacarpal joint.

The specific aim of this study was to develop a quantitative method and a kinematic method to evaluate the maximal workspace of the trapeziometacarpal (TM) joint. Six fresh-frozen human cadaver hands were disarticulated 4 cm proximal to the wrist joint and used in this experiment. The three-dimensional motion data of the TM joint was collected by an electromagnetic tracking device at 30 Hz. The workspace was reconstructed according to a complete set of motion data included circumduction, flexion-extension and abduction-adduction. A spherical fitting technique was used to obtain a sphere encompassing all the motion trajectories and estimating the centre of the sphere. The surface area of the maximal TM workspace, located on the one part of the sphere surface, was calculated by surface integration. The interclass correlation coefficient values for the reliability estimation of the repeated measurements of the radius and surface area of all specimens were 0.91 and 0.98 respectively. The mean coefficients of variance of the measured radius and the surface area were 2.04 per cent and 3.65 per cent respectively. The results also showed that using a spherical model to calculate the maximal workspace as an index for assessing TM joint impairment is practical.

Visual fields and tiagabine: a quandary.

This case report describes the development of asymptomatic visual field defects (VFDs) in a psychiatric patient with bipolar disorder receiving adjunctive tiagabine treatment. These defects were apparently reversible upon the discontinuation of tiagabine. Controlled clinical trials are indicated to determine if this finding is indicative of a class effect for all GABAergic antiepileptic drugs (AEDs), as already noted with vigabatrin, or if this case represents an incidental finding with tiagabine (41 references).

Patellar tracking in total knee arthroplasty: inset versus onset design.

Patellar components come in onset and inset designs. Kinematic differences between these designs were studied in a cadaver model of closed kinetic chain knee extension. Seven frozen knees were implanted with a standard posterior cruciate-retaining design. Each knee first was tested with the inset design, followed by the onset design in the Oxford Knee Rig. Three-dimensional tracking of the femur, tibia, and patella was performed using an electromagnetic system during active knee extension under load. No statistically significant differences were seen in knee kinematics between the 2 designs. The inset patella tended to shift laterally and tilt laterally more than the onset patella. This difference may be clinically significant.