Experimental muscle pain produces central modulation of proprioceptive signals arising from jaw muscle spindles.
ABSTRACT The aim of the present study was to investigate the effects of intramuscular injection with hypertonic saline, a well-established experimental model for muscle pain, on central processing of proprioceptive input from jaw muscle spindle afferents. Fifty-seven cells were recorded from the medial edge of the subnucleus interpolaris (Vi) and the adjacent parvicellular reticular formation from 11 adult cats. These cells were characterized as central units receiving jaw muscle spindle input based on their responses to electrical stimulation of the masseter nerve, muscle palpation and jaw stretch. Forty-five cells, which were successfully tested with 5% hypertonic saline, were categorized as either dynamic-static (DS) (n=25) or static (S) (n=20) neurons based on their responses to different speeds and amplitudes of jaw movement. Seventy-six percent of the cells tested with an ipsilateral injection of hypertonic saline showed a significant modulation of mean firing rates (MFRs) during opening and/or holding phases. The most remarkable saline-induced change was a significant reduction of MFR during the hold phase in S units (100%, 18/18 modulated). Sixty-nine percent of the DS units (11/16 modulated) also showed significant changes in MFRs limited to the hold phase. However, in the DS neurons, the MFRs increased in seven units and decreased in four units. Finally, five DS neurons showed significant changes of MFRs during both opening and holding phases. Injections of isotonic saline into the ipsilateral masseter muscle had little effect, but hypertonic saline injections made into the contralateral masseter muscle produced similar results to ipsilateral injections with hypertonic saline. These results unequivocally demonstrate that intramuscular injection with an algesic substance, sufficient to produce muscle pain, produces significant changes in the proprioceptive properties of the jaw movement-related neurons. Potential mechanisms involved in saline-induced changes in the proprioceptive signals and functional implications of the changes are discussed.
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ABSTRACT: BACKGROUND: This study firstly aimed to determine whether proprioception deficits, as measured by joint position sense (JPS), occur in people following recurrent patellar dislocations. Secondly, to determine whether JPS changes following medial patellofemoral ligament reconstruction (MPFL) reconstruction for patellar instability. METHODS: Thirty people following recurrent patellar dislocation were recruited. Pre-operative JPS was assessed using the passive angle reproduction test. Through this, an assessor moved a participant's limb to a target position. This was returned to neutral, before finally moving the limb again, whilst requiring the participant to indicate when they thought the target angle was reached. The actual angular error (AAE) was calculated as the difference between the perceived angle and target angle. Clinical outcomes included the Kujala Patellofemoral Disorder Score, the International Knee Documentation Committee (IKDC) form, pain, knee motion, extensor muscle strength and frequency of patellar dislocation. Outcomes were assessed pre-operative, 6weeks, 3 and 12months. RESULTS: Mean AAE was 2.2° (inner range) to 3.9° (mid-range); this was not clinically significant. There was no statistically significant difference between the baseline-and-6week, 6week-and-3month or baseline-and-12month AAE measures (p=0.38 to 1.00). There was a statistically significant improvement in functional outcomes as measured by the Kujala score, IKDC form, reduced pain and increased extension strength from baseline to 12months (p<0.01). CONCLUSIONS: Following recurrent patellar dislocation, patients exhibit minimal deficits in JPS. Whilst MPFL reconstruction significantly improved clinical and functional outcomes for this population, this operation did not significantly alter JPS during the first post-operative year.The Knee 10/2012; · 2.01 Impact Factor
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ABSTRACT: Jerk-cost is an inverse measure of movement smoothness and can be calculated from the first-time derivative of acceleration obtained from a tri-axial piezoelectric accelerometer (TPA), or from the third-time derivative of position obtained from a jaw-tracking device. The aims of this study were to determine, in 10 asymptomatic subjects who are chewing gum, (i) jerk-cost measures derived from displacement/time data obtained from the JAWS3D jaw-tracking device and from acceleration data obtained from a TPA used in the same jaw movement recordings, (ii) whether there was a significant relationship between jerk-cost measures derived from both devices and (iii) the degree of agreement between the two measures. Jerk-cost data were calculated in the opening phase, the closing phase, and over the full chewing cycle as the first-time derivative from acceleration obtained from the TPA, and the third-time derivative from JAWS3D for each of the X-, Y- and Z-direction series. There was a significant correlation between both measures of jerk-cost over the full chewing cycle and during jaw-opening (r = 0·65, 0·75, respectively; P < 0·001). There was no significant correlation in the closing phase (r = -0·02, P = 0·99). The Bland-Altman test showed that jerk-cost derived from the JAWS3D can differ by up to 78% below and 21% above that derived from the TPA. These results suggest that jerk-cost measures derived from a jaw-tracking system cannot substitute for jerk-cost measures derived from an accelerometer.Journal of Oral Rehabilitation 02/2011; 38(9):661-7. · 2.34 Impact Factor
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ABSTRACT: O objetivo foi verificar a influência da dor no controle postural de mulheres com dor cervical e a relação com as possíveis alterações nos sistemas sensoriais e postura corporal. O grupo dor cervical foi composto por mulheres, entre 20 e 50 anos, com dor cervical por mais de três meses e o grupo controle por 20 mulheres sem dor cervical. Para caracterização, utilizaram-se anamnese, índice de incapacidade cervical e Escala Visual Analógica. O equilíbrio postural foi avaliado por uma plataforma de força. O equilíbrio com manipulação dos sistemas sensoriais foi avaliado pela posturografia dinâmica Foam-laser, expondo o indivíduo a seis testes de organização sensorial. A postura foi avaliada pelo Software de Avaliação Postural. Normalidade das variáveis verificada pelo teste de Shapiro Wilk e testes t de student e Mann Whitney para comparação entre grupos, nível de significância de 5%. Os grupos apresentaram homogeneidade nas variáveis demográficas. No equilíbrio postural, observou-se maior amplitude e velocidade de deslocamento do centro de pressão no grupo dor cervical, demonstrando maior oscilação postural. Houve diferença significativa no ângulo crâniovertebral, mostrando anteriorização da cabeça nas mulheres sintomáticas. Na posturografia dinâmica, observou-se diferença entre os grupos sendo que o escore obtido nas seis condições sensoriais demonstrou que o grupo dor cervical apresentou maior comprometimento do equilíbrio. Dor cervical e postura anteriorizada da cabeça têm efeito deletério no controle postural de mulheres sintomáticas, tanto na postura estática quanto na postura dinâmica.Revista Brasileira de Cineantropometria & Desempenho Humano. 06/2013; 15(3):371-381.