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PubMed1996

Comparison of results of nocturnal penile tumescence and rigidity in a sleep laboratory versus a portable home monitor.

OBJECTIVES: To validate the results of the home penile tumescence monitor versus the sleep laboratory studies of erectile function. METHODS: We used both methods to study 18 episodes of rigidity and 19 episodes of tumescence in 10 subjects with erectile dysfunction before and after the use of an experimental vasodilating medication. RESULTS: The tumescence measurement in the sleep laboratory compared favorably with the changes in tumescence with the RigiScan portable home monitor: at the base (r = 0.70; P < 0.001), and at the tip (r = 0.84; P < 0.001). In measuring rigidity, the buckling pressure in the sleep laboratory compared favorably with the RigiScan measurements of percent average rigidity at the base (r = 0.56; P = 0.017), at the tip (r = 0.62; P = 0.006), and mean rigidity of the base and tip (r = 0.64; P = 0.004). In a comparison of the buckling pressure with the new RigiScan Plus quantitative program, there was good correlation with the rigidity activity units at the base (r = 0.70; P = 0.001) and at the tip (r = 0.72; P < 0.001). A clinical estimate of penetrable rigidity correlates with the RigiScan base rigidity of 55% to 60% and tip rigidity of about 50%. CONCLUSIONS: The portable home monitor is a viable and cost-effective clinical tool to measure nocturnal penile activity.

Aged↗
PubMed2000

Bilateral sagittal split osteotomy and temporomandibular disorders: rigid fixation versus wire fixation.

OBJECTIVE: The effects of orthognathic surgery on temporomandibular disorders may be related to the surgical method that is used. Specifically, it has been suggested that the choice of stabilization technique may play a major role in the functional outcome of mandibular advancement surgery. The purpose of this study was to prospectively compare long-term (2 years) signs and symptoms of temporomandibular disorders after orthognathic surgery with bilateral sagittal split osteotomy in 127 patients randomized to receive rigid or wire fixation. STUDY DESIGN: Signs and symptoms of temporomandibular disorders were evaluated before and 2 years after surgery by means of the overall craniomandibular index (CMI), dysfunction index (DI), and muscle index (MI). Patients also reported subjective symptoms of temporomandibular disorders by marking areas of pain on a standard drawing of the head and rating the pain in each area on a scale ranging from 1 (very mild) to 7 (very extreme). Subjective pain was also assessed through use of the Oral Health Status Questionnaire and by a rating of the difficulty in opening the mouth because of pain. RESULTS: There were no statistically significant differences in the CMI, MI, or DI change scores between the wire and rigid fixation groups (mean CMI(wire) = 0.05, mean CMI(rigid) = 0.04; mean DI(wire) = 0.02, mean DI(rigid) = 0. 01; mean MI(wire) = 0.08, mean MI(rigid) = 0.08) 2 years after surgery. Temporomandibular joint sounds also demonstrated no significant differences between the two fixation methods. Subjective pain reports were consistent with the clinical examinations. On average, both wire and rigid scores decreased slightly, but the change scores were not significantly different between groups. CONCLUSIONS: These findings suggest that the long-term (2 years) effects of wire and rigid internal fixation methods on the signs and symptoms of temporomandibular disorders do not differ. Earlier concerns about increased risk for temporomandibular disorders with rigid fixation were not supported by these results.

Adult↗
PubMed2003

The effect of design modifications on the torsional and compressive rigidity of U-shaped palatal major connectors.

STATEMENT OF PROBLEM: Rigidity is a requirement of removable partial denture frameworks. Although commonly used by dentists, the U-shaped (horseshoe) maxillary major connector lacks the rigidity of other maxillary major connector designs. PURPOSE: The purpose of this study was to determine the effects of changing width, thickness, and shape on the rigidity of U-shaped maxillary major connectors. MATERIAL AND METHODS: Five nickel-chrome alloy frameworks were fabricated from the same master cast for each of 4 different U-shape removable partial denture designs. The designs were an 8-mm wide U-shaped strap with a 6-mm posterior strap (A-P strap), a 13-mm-wide U-shape strap (Wide), an 8-mm-wide U-shape strap that widened to 13 mm at the midline (Notch), and an 8-mm-wide U-shaped strap that was twice the thickness of the other straps (Thick). A fifth group of 5 frameworks was made by removing the posterior strap from the A-P strap frameworks (A strap). Two testing points were marked on each framework corresponding to the first premolar and second molar positions. The frameworks were mounted in a universal testing machine, and vertical (torsional) and horizontal (compressive) loads were applied using a 10-kN load cell at a cross-head speed of 2 mm/min until a deflection of 1 mm occurred. A force-deflection curve was generated for each test, and slope of the curves (N/mm) was compared with analysis of variance and Scheffe's F test (alpha=0.05). RESULTS: The Thick group was found to be significantly more rigid (P<.05) than the other frameworks when torsional loads were applied to both the premolar (22.42 N/mm) and molar (10.88 N/mm) areas, and when a compressive load was applied to the premolar (232.85 N/mm) area. The A-P strap group was significantly more rigid (P< or =.05) than the other designs when a compressive load was applied to the molar (69.56 N/mm) area. Both the Thick and A-P strap groups were significantly more rigid (P<.05) than the Notch and A strap groups in all tests. CONCLUSION: Doubling the thickness of the anterior strap of a U-shaped maxillary major connector improved the rigidity of the framework to torsional loads. A posterior strap became more effective in maintaining framework rigidity to compressive forces as the length of the arch increased.

Analysis of Variance↗
PubMed2006

Fibronectin rigidity response through Fyn and p130Cas recruitment to the leading edge.

Cell motility on extracellular matrices critically depends on matrix rigidity, which affects cell adhesion and formation of focal contacts. Receptor-like protein tyrosine phosphatase alpha (RPTPalpha) and the alphavbeta3 integrin form a rigidity-responsive complex at the leading edge. Here we show that the rigidity response through increased spreading and growth correlates with leading edge recruitment of Fyn, but not endogenous c-Src. Recruitment of Fyn requires the palmitoylation site near the N-terminus and addition of that site to c-Src enables it to support a rigidity response. In all cases, the rigidity response correlates with the recruitment of the Src family kinase to early adhesions. The stretch-activated substrate of Fyn and c-Src, p130Cas, is also required for a rigidity response and it is phosphorylated at the leading edge in a Fyn-dependent process. A possible mechanism for the fibronectin rigidity response involves force-dependent Fyn phosphorylation of p130Cas with rigidity-dependent displacement. With the greater displacement of Fyn from p130Cas on softer surfaces, there will be less phosphorylation. These studies emphasize the importance of force and nanometer-level movements in cell growth and function.

Cell Division↗
PubMed2000

Polymorphonuclear leukocyte rigidity is defective in patients with chronic renal failure.

BACKGROUND: The purpose of the study was to investigate the rigidity of polymorphonuclear leukocytes (PMNs) in non-dialysed chronic renal failure (CRF) and haemodialysis (HD) patients. METHODS: PMN rigidity as well as tumour necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) plasma levels were assessed in 10 early-stage CRF, 10 late-stage non-HD, and 10 HD patients, before and during dialysis. In HD patients both cellulose acetate and polysulphone membranes were used. Ten healthy subjects served as controls. Rigidity was tested by counting the deformability in morphologically passive PMNs by the micropipette method. Cytokine levels were measured by enzyme-linked immunosorbent assay. RESULTS: PMN rigidity was significantly increased in end-stage CRF patients regardless of HD but not in early-stage CRF. In HD patients PMN rigidity increased significantly 60 min after initiation of HD. There was an increase of TNF-alpha and IL-1beta levels in end-stage non-HD and HD patients and a further increase at 60 min after initiation of HD. The percentage of morphologically activated PMNs was increased only during dialysis. The nature of the HD membrane had no influence on rigidity, PMN activation, or cytokine production. CONCLUSIONS: The results indicate that PMN rigidity is defective in end-stage chronic CRF patients and is further increased 60 min after initiation of HD, regardless of the nature of the HD membrane used. PMN activation, increased TNF-alpha and IL-1beta levels, or a direct PMN impairment may cause the observed cell rigidity.

Cytokines↗
PubMed2003

Cantilever bending technique for treatment of large and rigid scoliosis.

STUDY DESIGN: Retrospective review of a consecutive clinical series. OBJECTIVES: To assess the efficacy and clinical value of cantilever bending technique as a technique for correcting large (> or =70 degrees ) and rigid (flexibility < or =30%) scoliosis. SUMMARY OF BACKGROUND DATA: Scoliosis correction by current methods is a compromise between the rigidity of the deformity and corrective forces provided by these methods. For large and rigid scoliosis, the rigidity of the deformity cannot be overcome enough to achieve satisfactory correction. Thus, anterior release procedures are usually necessary to make the curves more flexible and thus improve correction. The cantilever bending technique provides powerful corrective forces for overcoming the rigidity of the deformity and obviates the need for anterior release procedures. The utility and efficacy of the method alone without anterior release for treating large and rigid deformity has not been demonstrated. METHODS: A total of 41 consecutive patients undergoing cantilever bending technique for the management of large and rigid scoliosis of any etiology (congenital, idiopathic, or neuromuscular) were included. Radiographic studies, complications, and satisfaction assessment using the modified Scoliosis Research Society Instrument were used to assess outcomes. RESULTS: The mean Cobb angle of the major curves was 98 degrees (range 75-133 degrees ). The deformity correction was 67.1% (range 51-74%). Coronal imbalance was 2.5 cm before and 0.8 cm after surgery. No major complication occurred. Satisfactory correction was achieved in all patients and without anterior release in all but one patient. Regardless of the etiology of their deformities, all patients were very satisfied with their outcomes. CONCLUSIONS: The cantilever bending technique is an effective procedure for the management of large and rigid scoliosis regardless of etiology. The clinical value of the procedure was demonstrated by reduced need for anterior release, fewer complications, and high rates of patient satisfaction.

Adolescent↗
PubMed1996

Clinical applicability of a new tactile sensor for evaluating rigidity of the penis: a comparative study with Rigiscan.

BACKGROUND: A new tactile sensor was developed for detecting hardness of living tissue by Omata et al. in 1992. This paper reports applicability of the sensor for evaluation of penile rigidity. METHODS: Nine patients from a group of 12 patients with penile erectile dysfunction were selected as subjects of this study. All patients agreed to artificial erection and monitoring of penile rigidity by a new tactile sensor and the Rigiscan system. The 9 patients selected all developed more than 1 cm circumferential expansion of the penis after an injection of smooth muscle relaxant into the corpus cavernosum. The sensor equipment consisted of a piezoelectric element that vibrated, and a pickup that detected vibration frequency. When the end of the sensor was pressed against a surface of the penis, the resonance frequency of the sensor changed and indicated rigidity of the organ. Rigidity of the penile shaft was simultaneously monitored with the sensor and the Rigiscan system before and after an injection of 40 mg papaverine or 20 micrograms prostaglandin E1. The sensor's measurements of rigidity were compared with those of Rigiscan. RESULTS: Reproducibility of rigidity measured with the tactile sensor was satisfactory. Statistical analysis was made on 85 simultaneous pairs of rigidity values from the tactile sensor and Rigiscan. The analysis indicated significant correlation between the values. CONCLUSION: The tactile sensor as well as Rigiscan will be of use for evaluating rigidity of the penis.

Adult↗
PubMed2000

Pediatric occipitocervical arthrodesis. A review of current options and early evaluation of rigid internal fixation techniques.

OBJECT: Few reports exist on the options and effectiveness of craniocervical stabilization in the pediatric population compared with the adult literature. Traditional options in children include onlay grafting and semi-rigid occipitocervical wiring. Recently, reports on the use of rigid internal fixation devices such as occipitocervical plates and contoured loops have provided excellent results in adults, and their use has often obviated the need for external orthosis. The purpose of this article is to report our experience with both traditional and newer rigid internal fixation methods for occipitocervical fusion in children. METHODS: During the past 4.5 years, 14 children (ages 4 months to 16 years) have undergone occipitocervical fusion. Indications for fusion included trauma (n = 4), congenital instability/stenosis (n = 6), postinfectious instability (n = 1) and basilar invagination (n = 3). Techniques using onlay grafting (n = 3) as well as rigid internal fixation using plates (n = 1) and contoured craniocervical titanium loops (n = 10) were used. Postoperative orthosis included halo vests (n = 7), minerva jackets (n = 3), sterno-occipital mandibular immobilizer (n = 1), and a cervical collar (n = 3). Long-term follow-up (range 13-58 months) was available for 13 of the 14 children. CONCLUSIONS: While each occipitocervical fusion in pediatric patients requires a customized treatment plan, we believe children older than 12 months of age should be considered candidates for rigid internal fixation methods. The rigidity afforded by this method may eliminate the need for rigid external orthotic support in selected individuals. In our experience, anatomic constraints in children less than 1 year old usually require fusion with more traditional onlay techniques. Long-term follow-up studies are still required to assess the effects of rigid internal fixation in the skeletally immature spine.

Adolescent↗
PubMed1999

Increased rigidity and priming of polymorphonuclear leukocytes in sepsis.

It has been proposed that abnormal mechanical properties may contribute to capillary retention of polymorphonuclear leukocytes (PMN) in sepsis, leading to the development of organ dysfunction. The present study was designed to determine whether PMN rigidity is increased in severe sepsis, and whether changes in the rheologic behavior of PMN correlate with the clinical course in sepsis. Eighteen adults with severe sepsis were studied over a period of 14 d; 11 survived and seven died. PMN deformation behavior was investigated via micropore filtration, using the cell transit analyzer. On Day 0, PMN rigidity was 2.5-fold greater for sepsis patients than for five normal controls (p < 0.001). PMN rigidity progressively improved over the 14 d study period for patients who recovered, but not for those who died; clinical indicators correlated with PMN rigidity. Patient PMN also exhibited a 5-fold greater increase in rigidity in response to formyl-methionylleucylphenylalanine (fMLP) than did control PMN. Both the increased rigidity and enhanced response to fMLP could be simulated in vitro by incubation of normal PMN with tumor necrosis factor-alpha (TNF-alpha). We conclude that circulating PMN are more rigid in severe sepsis, and are "primed" for an augmented response to chemotactic stimuli. These findings support the hypothesis that cytokine-mediated increases of PMN rigidity may lead to sequestration of these cells in capillaries and to the consequent impairment of microvascular perfusion in sepsis.

Adult↗
PubMed2005

Ocular rigidity in living human eyes.

PURPOSE: To measure the rigidity coefficient of a large number of subjects at clinically encountered intraocular pressures (IOPs) and to examine the possible correlation of ocular rigidity with other factors, such as the age of the patients, ocular parameters (axial length and corneal thickness), and pathologic conditions affecting the eye. METHODS: The pressure-volume relationship and the ocular rigidity coefficient (K) were determined in 79 eyes undergoing cataract surgery, by injecting 200 microL of saline solution (in steps of 4.5 microL) through the limbus into the anterior chamber, while continually monitoring the IOP with a transducer, up to the limit of 60 mm Hg. Data within an IOP range of 10 to 35 mm Hg were used to calculate the scleral rigidity coefficient. All measurements were taken at the same time of day, to eliminate any possible diurnal variation. RESULTS: The mean ocular rigidity coefficient was 0.0126 mm Hg/microL (95% confidence interval [CI], 0.0112-0.0149). A statistically significant positive correlation between the rigidity coefficient and age of the patient was found (P = 0.02), whereas similar findings were not observed for the examined ocular parameters (axial length, P = 0.09; and corneal thickness, P = 0.12). No correlation was found for patients with diabetes mellitus (P = 0.39), age-related macular degeneration (P = 0.55), and hypertension (P = 0.45). CONCLUSIONS: The present study provides quantitative data on the ocular rigidity coefficient based on measurements in a large series of living human eyes. A positive correlation between the ocular rigidity coefficient and the patient's age was documented.

Adult↗
PubMed1994

Correlation between self-reported rigidity and rule-governed insensitivity to operant contingencies.

Adults were selected on the basis of their scores on the Scale for Personality Rigidity (Rehfisch, 1958a). Their scores served as a measure of hypothesized rule governance in the natural environment. Experiment 1 studied the effects of accurate versus minimal instructions and high versus low rigidity on performance on a multiple differential-reinforcement-of-low-rate (DRL) 4-s fixed-ratio (FR) 18 schedule. When the schedule was switched to extinction, accurate instructions and high rigidity were associated with greater perseveration in the response pattern subjects developed during the reinforcement phase. In Experiment 2, the effects of rigidity and of accurate versus inaccurate instructions were studied. Initially, all subjects received accurate instructions about an FR schedule. The schedule was then switched to DRL, but only half of the subjects received instructions about the DRL contingency, and the other half received FR instructions as before. Accurate instructions minimized individual differences because both high and low scorers on the rigidity scale earned points in DRL. However, when inaccurate instructions were provided, all high-rigidity subjects followed them although they did not earn points on the schedule, whereas most low-rigidity subjects abandoned them and responded appropriately to DRL. The experiments demonstrate a correlation between performances observed in the human operant laboratory and a paper-and-pencil test of rigidity that purportedly reflects important response styles that differentiate individuals in the natural environment. Implications for applied research and intervention are discussed.

Journal Article↗
PubMed1987

Inducing flexibility in cognitive rigidity.

This study examined the extent to which normal learners identified as cognitively rigid could use alternate strategies when instructed to do so. The total number of rigid solutions on the standard portion of the "Three Jar Test" was used to divide eighty normal adults into high and low rigid groups. The second portion of the TJT instructed subjects to use a less rigid strategy. The two groups were compared for the total number correct and the number of rigid solutions. Analysis of these data showed that groups were not significantly different in either the extent to which the rigid solution (B-A-2C) was used nor in total number of corrects. The results were interpreted as lending support to the theoretical notion that two forms of rigidity may exist. Implications of the study seem to interest in understanding the otherwise normal rigid learner.

Adult↗
PubMed1982

Aortic rigidity and plasma catecholamines in essential hypertensive patients.

Aortic rigidity, plasma noradrenaline and adrenaline, and hemodynamic parameters were measured in 48 essential hypertensive patients, 25 younger than 45 (Group I) and 23 of 45 years and over (Group II). Aortic rigidity was determined by the ratio of pulse pressure over stroke volume. Aortic rigidity and hemodynamic parameters were also determined after combined alpha-beta receptor blockade induced by Labetalol (mg 100 IV) or by Propranolol (mg 10 IV) plus Phentolamine (mg 10 IV). The aortic rigidity index was significantly higher in Group II, systolic arterial pressure being significantly higher. All other data, including plasma noradrenaline and adrenaline, were not significantly different in the two groups. In Group II a significant correlation (r = 0.62) was noted between aortic rigidity indexes and plasma noradrenaline values. The alpha-beta receptor blockade induced a decrease of aortic rigidity particularly in Group II, owing to a more marked decrease of systolic arterial pressure. A highly significant correlation was noted in Group II between the changes in aortic rigidity index and the basal plasma noradrenaline levels (r = 0.81). Therefore, the aortic rigidity in essential hypertensive patients older than 45 is influenced by the sympathetic nervous system activity, as judged by plasma noradrenaline levels. This influence seems related to an increase with age of aortic responsiveness to sympathetic stimulation.

Adult↗
PubMed2002

An assessment of polymorphonuclear leukocyte rigidity in HIV-infected individuals after immune recovery.

PURPOSE: To determine whether polymorphonuclear leukocytes (PMNs) remain rigid after immune reconstitution in human immunodeficiency virus (HIV)-infected individuals with a history of severe immunosuppression. METHODS: PMN rigidity was measured in vitro in three groups: (1) HIV-infected individuals with a history of CD4+ T-lymphocyte counts of less than 50/microL, but with current counts of more than 200/microL attributable to potent antiretroviral therapy (group 1); (2) HIV-infected individuals whose CD4+ T-lymphocyte counts had always been more than 200/microL (group 2); and (3) HIV-negative control subjects. Rigidity was determined with a cell transit analyzer (containing a micropore filter with 30 identical, 8-microm diameter pores), representing a simple in vitro model of a capillary bed. A longer PMN pore transit time reflects increased PMN rigidity. RESULTS: PMN transit time (median) in group 1 (n = 11) was 3.34 ms, in group 2 (n = 9) was 3.19 ms, and in control subjects (n = 15) was 2.66 ms. PMN rigidity was significantly greater in groups 1 (P = 0.014) and 2 (P = 0.046) than in control subjects (Wilcoxon rank-sum test). A significant difference was not identified between groups 1 and 2 (P = 0.518). CONCLUSIONS: The increased PMN rigidity known to occur in severely immunosuppressed HIV-infected individuals persists after immune reconstitution. Furthermore, PMN rigidity is increased in those HIV-infected individuals who do not have a history of severe immunosuppression. Because PMN rigidity can alter microvascular blood flow, HIV-infected individuals may remain at risk for retinal vascular damage in the era of potent antiretroviral therapy.

Adult↗
PubMed1998

Axial penile rigidity: determinants and relation to hemodynamic parameters.

Erectile dysfunction may be defined in terms of axial penile rigidity, the physical property that enables the erection to be utilized as a penetration tool during sexual activity. Erectile dysfunction occurs when inadequate axial penile rigidity results in buckling of the penile column when subjected to axial compressive loading situations during vaginal intromission. New multi-disciplinary engineering studies of penile hemodynamic and structural dynamic relationships are reviewed concerning the determinants of axial penile rigidity. Axial penile rigidity develops as a continuum during the increases in intracavernosal pressure and volume changes from the flaccid state and is influenced by intracavernosal pressure, penile tissue mechanical properties and penile geometry. Two penile tissue mechanical properties are especially relevant; cavernosal maximum volume at relatively low intracavernosal pressure, and tunical distensibility, the relative volume of the fully erect to completely flaccid pendulous penis. Two penile geometric properties are critical; the penile aspect ratio, defined as the diameter to length ratio of the pendulous penis, and the magnitude of the flaccid penile diameter. Clinically measured values of axial buckling forces in patients undergoing dynamic pharmacocavernosometry strongly correlated to theoretic-based analytic derived magnitudes of axial penile rigidity based on these above pressure, tissue and geometric determinants. Since axial penile rigidity is not exclusively dependent upon intracavernosal pressure, patients with normal erectile hemodynamics may be erroneously labelled as having psychogenic dysfunction where their true pathophysiology may be related to abnormal penile tissue properties and/or penile geometric factors. Similarly, some patients may claim sufficient rigidity for penetration, but have abnormal hemodynamic erectile function studies. They may have uniquely advantageous tissue mechanical and/or geometric properties. More research is needed concerning axial penile rigidity, a most influential factor determining functional erectile quality, erectile potency and successful coitus.

Hemodynamics↗
PubMed1994

Portable device for quantifying parkinsonian wrist rigidity.

The need for objectivity in the assessment of parkinsonism prompted the development of a portable transducer capable of quantifying muscular rigidity. This paper describes the development and use of a device for measuring wrist rigidity and reports the preliminary findings from 25 normal healthy controls and 29 patients, many of whom were undergoing antiparkinsonian treatment to alleviate rigidity or antipsychotic treatment, which produced parkinsonian rigidity. An objective rigidity score, representing the degree to which motor activity increases muscular stiffness in the wrist, correlates highly with clinical ratings of parkinsonian rigidity and demonstrates 89% specificity and 82% sensitivity. Unlike previous techniques for quantifying rigidity, this transducer offers greater portability and apparent face validity.

Adult↗
PubMed1994

Antiparkinsonian action of MK-801 on the reserpine-induced rigidity: a mechanomyographic analysis.

MK-801, a non-competitive antagonist of NMDA receptors, is known to exhibit a beneficial action in many animal models of Parkinson's disease. The aim of this study was to examine the influence of MK-801 on the reserpine-induced muscle rigidity. The rigidity was estimated by a direct mechanomyographic method. This method consists in successive bending and straightening of a rat's hind foot in the ankle joint and measuring the resistance of the foot to passive movements. Reserpine in doses of 5-10 mg/kg ip, given alone or in combination with alpha-methyl-p-tyrosine (alpha MT, 250 mg/kg ip), induced rigidity. The strongest muscle rigidity was induced by 10 mg/kg of reserpine 1 hour after administration. MK-801 (0.32-1.28 mg/kg sc) injected 70 min after reserpine (10 mg/kg ip) decreased the rigidity induced by the latter compound. Similarly, MK-801 (1.28 mg/kg sc), administered 27 h 40' after joint treatment with reserpine (10 mg/kg ip) and alpha MT (250 mg/kg ip), strongly inhibited the reserpine-induced muscle rigidity. The obtained results show that the glutamatergic hyperactivity plays a significant role in the reserpine-induced rigidity. As the reserpine-induced motor disturbances are commonly accepted to be an animal model of parkinsonian symptoms, it may be assumed that the NMDA receptor blocking component may contribute substantially to the therapeutic action of antiparkinsonian drugs.

Animals↗
PubMed2004

The role of shortening reaction in mediating rigidity in Parkinson's disease.

Rigidity in Parkinson's disease (PD) is defined as an increased resistance to passive movement of a joint. The plastic-type rigidity is uniform and constant throughout the entire range of motion, whereas the cogwheel-type rigidity is accompanied by tremor. Rigidity in PD has been understudied. Thus, its pathophysiological basis remains unclear. The purpose of the study is to examine neuromuscular/biomechanical properties of PD rigidity and to provide its physiological characteristics. We hypothesize that PD rigidity presents as a flattened trace of joint torque vs. angular position (torque-angle relation) of the wrist, because the forces generated by lengthening muscles are offset by activation of the antagonist, i.e. show "shortening reaction" (SR). Experiments were conducted on six PD subjects medication OFF and ON. PD severity was assessed based on the unified Parkinson's disease rating scale. Each subject sat on a chair and was instructed to relax, with the wrist coupled to the device. The servomotor applied constant velocity displacement to create wrist flexion/extension. Electromyographic (EMG) responses were monitored from wrist muscles, along with position, velocity and torque. EMG magnitudes were computed over the movement period. Slopes were derived from the torque-angle trace. Results showed that SRs were routinely recorded OFF medication, but substantially reduced ON medication. Due to the interaction of SR, torque-angle relation was flatter OFF medication and became steeper ON medication. Correlation analyses showed that a strong correlation (R=0.65) existed between SR and torque-angle slope OFF medication, exclusively. We suggest that SR may play an important role in mediating the mechanical features of PD rigidity.

Adult↗