Limb immobilization alters functional electrophysiological parameters of sciatic nerve

Static Body Weight Distribution and Girth Measurements Over Time in Dogs After Acute Thoracolumbar Intervertebral Disc Extrusion

Dogs with thoracolumbar intervertebral disc extrusion (TL-IVDE) can exhibit variable neurologic deficits after decompressive surgery. The objectives of this study were to quantify changes in static weight distribution (SWD) and limb and body circumference over time in dogs recovering from surgery for TL-IVDE. Dogs with acute TL-IVDE were prospectively evaluated at baseline (48–72 h post-operatively), 2, 4, 8, and 12 weeks post-operatively. Commercially-available digital scales were used to measure weight distributed to the pelvic limbs (PL%) and asymmetry between left and right pelvic limbs (LRA), each expressed as a percentage of total body weight. Trunk and thigh circumference measurements were performed using a spring-loaded tape measurement device. Measurements were performed in triplicate, compared to neurologically normal small breed control dogs and analyzed for changes over time. P <0.05 was significant. Twenty-one dogs were enrolled; 18 regained ambulation and 3 did not by study completion. PL% increased from 27.6% at baseline to 30.7% at 12 weeks but remained lower than in control dogs (37%) at all time points (p < 0.0001), even excluding dogs still non-ambulatory at 12 weeks (p < 0.025). LRA was similar to the control dogs, and did not have an association with surgical side. Caudal trunk girth decreased over time to 95% of baseline (p = 0.0002), but this was no longer significant after accounting for reductions in body weight (p = 0.30). Forward shifting of body weight persisted in dogs with TL-IVDE 12 weeks after surgery even among ambulatory dogs. SWD and circumference measurements could provide additional objective measures to monitor recovery.

A rat model of hip joint contracture induced by mono-articular hip joint immobilization

BACKGROUND

To elucidate the formation process and therapeutic targets of hip flexion contracture, we developed a rat model of hip flexion contracture induced by hip mono-articular immobilization.

METHODS

Kirschner wires inserted into the femur and hip bone were anchored at the hip in a flexed position in the immobilization groups and unanchored in the sham groups for up to four weeks. Age-matched untreated rats were used as controls. Hip extension range of motion (RoM) was measured at three different extension moments (7.5, 15, and 22.5 N•mm) in each successive myotomy step as follows: before myotomy, after sequential myotomy of the tensor fascia lata, quadriceps muscle, iliopsoas muscle, and after myotomy of all residual muscles (the gluteus medius and adductor muscles). Histological analysis of the hip joint was also performed.

FINDINGS

After four weeks of immobilization, the RoM before myotomy at 22.5 N•mm was significantly decreased by 29° compared with controls, and this value was unaltered in the sham group. Analyses following serial myotomy suggested that the structures responsible for myogenic contracture were the tensor fascia lata, iliopsoas, gluteus medius, and adductor muscles because the RoMs were increased by these myotomies. Unexpectedly, arthrogenic contracture was not detected at moments other than at 7.5 N•mm, even after four weeks of immobilization. Histological analysis confirmed that pathological changes were not apparent in the anterior capsule of the hip joint.

INTERPRETATION

The present findings suggest that myogenic contracture may be an important therapeutic target for immobilization-induced hip flexion contracture.

Sauna use as a lifestyle practice to extend healthspan

Sauna use, sometimes referred to as "sauna bathing," is characterized by short-term passive exposure to high temperatures, typically ranging from 45 °C to 100 °C (113 °F to 212 °F), depending on modality. This exposure elicits mild hyperthermia, inducing a thermoregulatory response involving neuroendocrine, cardiovascular, and cytoprotective mechanisms that work in a synergistic fashion in an attempt to maintain homeostasis. Repeated sauna use acclimates the body to heat and optimizes the body's response to future exposures, likely due to the biological phenomenon known as hormesis. In recent decades, sauna bathing has emerged as a probable means to extend healthspan, based on compelling data from observational, interventional, and mechanistic studies. Of particular interest are the findings from large, prospective, population-based cohort studies of health outcomes among sauna users that identified strong dose-dependent links between sauna use and reduced morbidity and mortality. This review presents an overview of sauna practices; elucidates the body's physiological response to heat stress and the molecular mechanisms that drive the response; enumerates the myriad health benefits associated with sauna use; and describes sauna use concerns.

Short-Term Immobilization Promotes a Rapid Loss of Motor Evoked Potentials and Strength That Is Not Rescued by rTMS Treatment

Short-term limb immobilization results in skeletal muscle decline, but the underlying mechanisms are incompletely understood. This study aimed to determine the neurophysiologic basis of immobilization-induced skeletal muscle decline, and whether repetitive Transcranial Magnetic Stimulation (rTMS) could prevent any decline. Twenty-four healthy young males (20 ± 0.5 years) underwent unilateral limb immobilization for 72 h. Subjects were randomized between daily rTMS (n = 12) using six 20 Hz pulse trains of 1.5 s duration with a 60 s inter-train-interval delivered at 90% resting Motor Threshold (rMT), or Sham rTMS (n = 12) throughout immobilization. Maximal grip strength, EMG activity, arm volume, and composition were determined at 0 and 72 h. Motor Evoked Potentials (MEPs) were determined daily throughout immobilization to index motor excitability. Immobilization induced a significant reduction in motor excitability across time (−30% at 72 h; p < 0.05). The rTMS intervention increased motor excitability at 0 h (+13%, p < 0.05). Despite daily rTMS treatment, there was still a significant reduction in motor excitability (−33% at 72 h, p < 0.05), loss in EMG activity (−23.5% at 72 h; p < 0.05), and a loss of maximal grip strength (−22%, p < 0.001) after immobilization. Interestingly, the increase in biceps (Sham vs. rTMS) (+0.8 vs. +0.1 mm, p < 0.01) and posterior forearm (+0.3 vs. +0.0 mm, p < 0.05) skinfold thickness with immobilization in Sham treatment was not observed following rTMS treatment. Reduced MEPs drive the loss of strength with immobilization. Repetitive Transcranial Magnetic Stimulation cannot prevent this loss of strength but further investigation and optimization of neuroplasticity protocols may have therapeutic benefit.

Development of a simple method to measure static body weight distribution in neurologically and orthopedically normal mature small breed dogs

Background

Objective outcome measures capable of tracking different aspects of functional recovery in dogs with acute intervertebral disc herniation are needed to optimize physical rehabilitation protocols. Normal, pre-injury distribution of body weight in this population is unknown. The aims of this study were to quantify static weight distribution (SWD) using digital scales and to establish the feasibility of different scale methods in neurologically normal, mature, chondrodystrophic small breed dogs predisposed to intervertebral disc herniation.

Results

Twenty-five healthy, mature dogs were enrolled with a mean age of 4.6 years (SD 2.7) and a mean total body weight of 11.5 kg (SD 3.6). SWD for the thoracic and pelvic limbs and between individual limbs was acquired in triplicate and expressed as a percentage of total body weight using commercially available digital scales in four combinations: two bathroom, two kitchen (with thoracic and pelvic limbs combined), four bathroom and four kitchen (with limbs measured individually). SWD was also obtained using a pressure sensing walkway for comparison to scale data. Feasibility for each method was determined and coefficients of variation were used to calculate inter-trial variability. Mean SWD values were compared between methods using an ANOVA. The two bathroom scales method had the highest feasibility and lowest inter-trial variability and resulted in mean thoracic and pelvic limb SWD of 63 % (SD 3 %) and 37 % (SD 3 %), respectively. Thoracic limb mean SWD was higher for the PSW compared to any of the scale methods (p < 0.0001).

Conclusions

SWD in a population of healthy chondrodystrophic dogs was simple to obtain using inexpensive and readily available digital scales. This study generated SWD data for subsequent comparison to dogs recovering from acute intervertebral disc herniation.

FUNCTIONAL ANALYSIS OF GAIT WITH INSOLE USE IN DIABETIC FEMALE RATS: A CROSS-SECTIONAL STUDY

ABSTRACT Introduction: Diabetes mellitus is a chronic disease that is characterized by causing damage to the peripheral nervous system, generating sensory and motor changes. Objective: This study aims at analyzing the impact of the use of different orthotic insoles on the gait of diabetic female rats. Methods: Twenty-six female Wistar rats were randomly divided into the Control and Diabetic groups. The mechanical sensitivity test was performed manually on the surface of the animals' hind paws using the von Frey test. The functional evaluation was carried out on an adapted platform where the animals were stimulated to walk in order to capture images of the ventral region for measurements of the right and left hind paws. After the images were collected they were processed using Kinovea software version 0.8.27 to assess: stride distance, time, speed and acceleration. Results: There was a reduction in the weight of the animals in the Diabetic Group (p = 0.0018), associated with hyperglycemia (p = <0.0001), and a decrease in mechanical sensitivity as compared to the Control Group (p = 0.0372). Gait analysis showed a reduction in stride speed (p = 0.0482) and acceleration (p = 0.0149), with the silicone orthosis in the Diabetic Group. Conclusions: The silicone orthosis demonstrated a reduction in stride speed and acceleration, without compromising the other variables in the diabetic rats. The other insoles showed no functional difference between groups. Even though the animals showed a change in sensitivity at the end of 28 days of DM induction, this time does not appear to have been able to develop extensive changes in the rats' gait function. Level of evidence II; Therapeutic studies - Investigating the Results of Treatment.

Spinal Manipulation Therapy Improves Tactile Allodynia and Peripheral Nerve Functionality and Modulates Blood Oxidative Stress Markers in Rats Exposed to Knee-Joint Immobilization

OBJECTIVE

The purpose of our study was to evaluate the effect of manually assisted lumbar spinal manipulation therapy on tactile allodynia, peripheral nerve functional recovery, and oxidative markers in rats exposed to knee immobilization-inducing hypersensitivity.

METHODS

Tactile allodynia and sciatic, tibial, and peroneal functional indices were assessed before the knee joint immobilization, 24 hours after the knee cast removal, and 24 hours after 3 weeks of lumbar therapy with the Activator Adjusting Instrument, model 4 (AAI 4). Subsequently, the blood was collected from each rat, and oxidative markers such as lipid hydroperoxide levels; nitric oxide metabolites; and superoxide dismutase, catalase, and glutathione peroxidase activities were assessed.

RESULTS

The AAI 4 improved the immobilization-induced allodynia and recovered the peripheral nerve functional indices impaired after knee immobilization. Immobilized rats treated with AAI 4 therapy presented a lack of significant changes in lipid hydroperoxides and nitric oxide metabolites in the plasma contrasting with rats that were kept freely in their cages, with no therapy applied, which presented elevated lipid hydroperoxides levels. Also, the antioxidant catalase enzymatic activity decreased in the blood of rats immobilized and treated with AAI 4.

CONCLUSION

These results suggest that manually assisted lumbar spinal manipulation therapy modulates systemic oxidative stress, which possibly contributes to the analgesia and recovery of peripheral nerve functionality.

Case Report: Canine Strain– and Study Condition–Dependent Formation of Renaut Bodies in Sciatic Nerves of Beagle Dogs

Two beagle dog strains were used in a 14-day intrathecal infusion study for a small molecule test article. A moderate number of Renaut bodies (RBs) were observed in the sciatic nerves of control and test article–treated adult animals as early as 1 day after test article infusion (ie, 5 days after catheter implantation in the lumbar cistern). In most cases, the sciatic nerve was affected unilaterally, apparently in association with extended lateral recumbency on one side. The lighter beagle strain (Marshall), and especially the females (which weighed less than age-matched Marshall males), developed more RBs. In contrast, neither females nor males of the larger strain (Harlan) developed any nerve lesions. These data support the hypothesis that RBs develop following mechanical stress to sciatic nerves, suggest that this change may develop fairly quickly following an insult, and demonstrate that different dog strains exhibit strain-specific nerve changes.

Stimulus electrodiagnosis and motor and functional evaluations during ulnar nerve recovery

BACKGROUND:

Distal ulnar nerve injury leads to impairment of hand function due to motor and sensorial changes. Stimulus electrodiagnosis (SE) is a method of assessing and monitoring the development of this type of injury.

OBJECTIVE:

To identify the most sensitive electrodiagnostic parameters to evaluate ulnar nerve recovery and to correlate these parameters (Rheobase, Chronaxie, and Accommodation) with motor function evaluations.

METHOD:

A prospective cohort study of ten patients submitted to ulnar neurorrhaphy and evaluated using electrodiagnosis and motor assessment at two moments of neural recovery. A functional evaluation using the DASH questionnaire (Disability of the Arm, Shoulder, and Hand) was conducted at the end to establish the functional status of the upper limb.

RESULTS:

There was significant reduction only in the Chronaxie values in relation to time of injury and side (with and without lesion), as well as significant correlation of Chronaxie with the motor domain score.

CONCLUSION:

Chronaxie was the most sensitive SE parameter for detecting differences in neuromuscular responses during the ulnar nerve recovery process and it was the only parameter correlated with the motor assessment.

Análise da função pulmonar e estrutura micromecânica após 14 dias de restrição de movimento em ratas

RESUMO A imobilização é uma condição que compromete diversos segmentos e sistemas orgânicos, inclusive o sistema respiratório, levando a alterações estruturais e funcionais. O objetivo deste estudo foi analisar a função pulmonar e estrutura micromecânica após 14 dias de restrição de movimento de ratas. Foram utilizados catorze ratas Wistar com massa corporal entre 210 g±50 g, distribuídas em dois grupos, compostos por (n=7) cada grupo: Controle (C) e Imobilizado (I). O procedimento de imobilização envolveu abdômen (e últimas costelas), pelve, quadril e joelho em extensão, além de tornozelo em flexão plantar, por duas semanas. Após esse período de imobilização, foi realizada a análise da função pulmonar por ventilador mecânico para pequenos animais (flexiVent) e manobras de recrutamento alveolar (MR). E, posteriormente, foram retiradas tiras do pulmão de cada animal para analisar a micromecânica pulmonar. Para a análise estatística, utilizou-se o teste t não pareado com significância estatística (p<0,05), expresso como média±erro padrão da média. O grupo I apresentou mudanças significantes nos parâmetros da resistência das vias aéreas (RN) pré-MR(C=0,067±0,003 cmH2O.s/mL, I=0,095±0,004 cmH2O.s/mL, p<0,05) e histerisividade (η) pré-MR(C=0,203±0,004 cmH2O.s/mL, I=0,248±0,013 cmH2O.s/mL, p<0,05), que retornaram a seus valores de normalidade pós-MR, considerando-se RN pós-MR (C=0,064±0,003 cmH2O.s/mL, I=0,065±0,004 cmH2O.s/mL, p<0,05) e η (C=0,209±0,005 cmH2O.s/mL, I=0,214±0,007 cmH2O.s/mL, p<0,05). Conclui-se que a imobilização acarreta alterações funcionais reversíveis no sistema respiratório após 14 dias de restrição de movimento, o que é evidenciado pela redução de RN e η pós-MR.

Sensorial, structural and functional response of rats subjected to hind limb immobilization

AIMS

This study analyzed the sensorial, structural and functional response of rats subjected to paw immobilization.

MAIN METHODS

Animal pelvis, hip, knee and ankle were immobilized using waterproof tape during two weeks for assessment of sensorial response to thermal (hot plate test) and mechanical stimuli (Von Frey test), motor system structure (histology and radiography) and muscle function (soleus contractility).

KEY FINDINGS

Disuse animals became more responsive to thermal stimuli (49%), although less responsive to mechanical challenge (58%). Disuse animals showed local injuries such as reduction in muscle fiber diameter (16.7% in gastrocnemius, 5.7% in soleus), contractile activity (55% of the control maximal tonic contraction) and tibia cortical thickness (9.3%), besides increased nitrite:protein ratio, suggestive of protein degradation. Disuse also evoked systemic adaptations that include increase in serum lactate dehydrogenase (36.1%) and alkaline phosphatase (400%), but reduction in calcium (8.4%) and total serum protein (5.5%), especially albumin (34.2%).

SIGNIFICANCE

Two weeks of functional paw disuse leads to local and systemic harmful adaptive changes in sensorial and structural systems. This study brings new insights into nervous and motor system mechanism associated with therapeutic limb immobilization in muscle and skeletal pathological conditions.