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1.2 Proprioception [UPDATED]

Objective: To determine whether proprioceptive impairments exist in patients with low back pain (LBP). We hypothesized that patients with LBP would exhibit larger trunk proprioception errors than healthy controls.

1.2 Proprioception

Revising the author's 1996 argument in "Translation as Phantom Limb," the article argues that the proprioceptive system, a proprioception of the body politic, which controls the phantom limb phenomenon, has a collective extension that organizes group behavior--and that translation is in essence an extremely complex social activity involving the alignment of two collective proprioceptive systems (source-cultural and target-cultural) in order to produce a single text. Through close readings of Viktor Shklovsky's essays on estrangement, the author shows that postcolonial translation theories from the early nineties, like those offered by Venuti, Niranjana, and Cheyfitz, are essentially talking about the enlivening effect temporal and cultural estrangement can have on the readers of a translation. A version of this article was delivered at the 2006 ATA Conference in New Orleans as the Marilyn Gaddis Rose Lecture.

Purpose: Adolescent idiopathic scoliosis (AIS) is a three-dimensional deformity of the spine associated with disturbed postural control. Cervical proprioception participates in controlling orthostatic posture via its influence on head stabilization. We hypothesized that patients with AIS exhibit altered cervical proprioception.

Methods: We conducted a case-control study to evaluate cervical proprioception using the cervicocephalic relocation test (CRT) in 30 adolescents with AIS (15.5 1.5 years; Cobb 24.8 9.5) versus 14 non-scoliotic controls (14.6 2.0 years). CRT evaluates cervical proprioception by measuring the capacity to relocate the head on the trunk after active rotation of the head in the transversal plane without visual control. Each subject performed ten right and then ten left head rotations.

Conclusion: Cervical proprioception is impaired in certain AIS patients. This anomaly may worsen the prognosis of AIS (headache; balance disorders; worsened spinal deformity; complication after spinal fusion). We recommend systematic screening for altered cervical proprioception in AIS patients.

In non-human primates, the time needed for afferent signals from proprioception to reach brain areas has been estimated to be as little as about 30 ms (Fetz et al., 1980; Soso and Fetz, 1980; Evarts and Fromm, 1981). In a study comparing reaction times to a visual stimulus and to a kinaesthetic one in humans, Flanders and Cordo (1989) found that it took approximately 250 ms to react to a visual stimulus and only 150 ms to react to a kinaesthetic one. In that study subjects had to modulate the left elbow torque in response to a stimulus that could be presented either visually or kinaesthetically. For the visual task, subjects saw the stimulus moving for 70 ms and had to increase or decrease the left elbow torque in a determined direction depending on the final position of the stimulus. For the kinaesthetic task, subjects' right elbow was rotated and they had to increase or decrease the left elbow torque in response to how the right elbow was rotated. In another study with an easier task, Flanders et al. (1986) reported smaller values but in the same direction (110 ms for kinaesthetic information and 190 for visual information). Shorter latencies were reported in Johansson and Westling (1987) who found compensatory responses after 75 ms in response to feedback from the skin receptors in a grip task.

(A) Velocity profile of a hand movement in a pursuit task (adapted from Rodríguez-Herreros and López-Moliner, 2008). (B) The expected perceptual bias across time would be determined by the velocity profile and the differential delay (color coded) between vision and proprioception. Inset: The expected bias as a function of tangential velocity for the four possible differential delays used in the simulation. See text for more details.

In order to compute the bias one could, therefore, obtain the unisensory estimates for vision and proprioception by finding earlier positions within a movement, such that the proprioceptive estimate would correspond to the actual position some time steps prior to the current position, and the visual estimate would correspond to an even earlier position. However, because the bias only depends on the differential delay between vision and proprioception, for simplicity we assumed no delay for proprioception in our simulation. Accordingly, we included in Equation 1 delayed positions for vision and updated positions for proprioception. We used 30, 40, 50, and 60 ms of delay (proprioception leading vision), values that include lower and upper bounds for the differential delays reported in the literature (discussed above).

Bias as a function of angular velocity adapted from Gritsenko et al. (2007), (Figure 7A) for the different active movement conditions. Different colors code the angles at which the probe was shown while moving the arm (60, 75, 90, and 105 in blue, black, orange, and red respectively). The black line denotes the expected bias assuming a differential delay of 60 ms between vision and proprioception. The blue solid line denotes the best fit (slope 0.066 s and zero intercept) including the data points that fall within the gray rectangle. The dashed solid line (slope 0.133 s and zero intercept) denotes the fit to all data points.

We assumed that the initial position (before any movement) of the integrated hand estimate was aligned with the actual hand position (Smeets et al., 2006). In each trial of the simulation, the initial felt and seen positions of the hand were randomly drawn from a Gaussian distribution with a SD of 1 cm and 0.75 cm for proprioception and vision, respectively, centered around the actual position of the hand. These values correspond to the variances used before. Once we had the unisensory estimates of the initial positions we computed the delayed unisensory running estimates based on the previously obtained velocity profile of the actual movement. This produced two time series of changing position, one for vision and another for proprioception, with the only difference being the starting position, which was drawn at random.

It is possible, however, that sensory estimates are not integrated. Rather, it may be that when vision is available it dominates position sense, and when vision is absent proprioception dominates position sense. This would not affect the direction of the bias that we have modeled, but it would increase the size of the bias. The predicted bias would be equal to the difference between the proprioceptive estimate (reaching in the dark) and the delayed visual estimate (reaching in the light), rather than the difference between the proprioceptive estimate (reaching in the dark with infinite variance for the visual estimate) and the integrated estimate (reaching in the light with weighted estimates).

This prospective longitudinal trial enrolled all candidates for ACL reconstruction with isolated primary ACL ruptures confirmed by magnetic resonance imaging (MRI) and physical examinations, such as positive anterior drawer, Lachmann, and/or pivot shift tests (more than grade II). Patients with concomitant meniscus tear were excluded to eliminate bias resulting from meniscus tear. Also excluded were patients with bilateral ACL injuries or associated injuries to any other ligament (i.e., the medial or lateral collateral ligament or the posterior cruciate ligament), previous injury / surgery to either knee, or any associated extra-articular lesions. Patients were also excluded if they were unable to perform the isokinetic muscle strength, postural stability, or proprioception tests due to pain or limited motion of the knee joint due to effusion. Patients who underwent surgery less than 3 months after injury were categorized as having acute ACL tears, whereas those who underwent surgery after 3 months were categorized as having chronic ACL tears. Of the 82 patients (82 knees) approached, 80 agreed to take part in the study. After assessments for eligibility, 76 patients, 48 with acute and 28 with chronic ACL tears, were enrolled. The baseline demographic characteristics of the two groups were similar except for time interval from injury to surgery (Table 1).

A reproduction of passive positioning (RPP) using the Biodex multi-joint system 4 was used to measure the joint position sense of knee joint proprioception.The mean and standard deviation of the two trials was calculated by this system. This system could measure the RPP to two decimal places.

Of the parameters associated with proprioception and postural stability, only RPP on the involved side differed significantly between the acute and chronic ACL tear groups. Therefore, correlation analyses were performed between various parameters and RPP on the involved side. Univariate analysis showed that patient age, time from injury to surgery, peak torques of the hamstring muscles on the involved and uninvolved sides, and RPP on the uninvolved side were significantly correlated with RPP on the involved side (Table 4). Multiple linear regression analysis of these 5 parameters showed that duration from injury to operation (β = 0.202, P = 0.039) and RPP on the uninvolved side (β = 0.242, P = 0.026) were significant and independent predictors of RPP on the involved side (Table 5).

This study quantitatively compared proprioception and postural stability in patients with acute and chronic ACL tears using parameters such as RPP and stability indices. The main finding of this study was that RPP on the involved side was greater in patients with chronic than acute ACL tears. In addition, RPP and the OSI and APSI stability indices were greater on the involved than on the uninvolved side, but only in the chronic ACL tear group. 041b061a72

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