Subacromial Anesthetics Increase Proprioceptive Deficit in the Shoulder and Elbow in Patients With Subacromial Impingement Syndrome

Abstract

Shoulder proprioception gives information regarding arm joint position and movement direction. Several studies have investigated shoulder proprioceptive acuity in patients with subacromial impingement syndrome (SIS); however, differences in protocols and between-subjects designs have limited scientific inferences regarding proprioception and SIS. We aimed to determine within-subject differences in shoulder and elbow proprioceptive acuity in 17 patients with stage 2 SIS following treatment of a local anesthetic injection. In addition, we used 17 healthy, age-, sex-, and arm dominance–matched controls to determine the magnitude of differences after treatment. Joint position sense (JPS) was measured before and after treatment in both groups in the sagittal plane for the shoulder and elbow. Our results indicate that patients with SIS have less sensitivity to angular position and tended to overshoot their targets with greater variability during angle-matching tasks for the shoulder (1.8° difference, P = .042) and elbow (5.6° difference, P = .001) than controls. The disparities in JPS found in patients with SIS were not resolved following subacromial injection; in fact, the magnitude of the errors increased after treatment where postinjection errors were significantly greater (P = .046) than controls, with an average difference of 2.4°. These findings suggest that patients with SIS have decrements in either the signaling or processing of proprioceptive information and may use pain to reduce these inequalities.

Wrist joint proprioceptive acuity assessment using inertial and magnetic measurement systems

“…There were three dependent variables for JPS errors: absolute error (AE), [40][41][42][43][44] constant error (CE), 4,[45][46][47][48] and variable error (VE). [49][50][51] While AE is an assessment of overall error, CE reflects the directionality of errors and VE is the variability of the error over a series of trials and represents the accuracy of the performance. AE m was calculated to obtain the AE between the target position and reproduced position of the m-position for all the data together.…”

Patients with Subacromial Pain Syndrome Present no Reduction of Shoulder Proprioception: A Matched Case‐Control Study

“…The absence of the impairment of the proprioception of the shoulder in a pain‐free movement in patients with SAPS is a novelty of our study that extends and complements previous work. We have chosen the shoulder rotation movement with intermediate angles to avoid causing pain in the patients, since it is already known that pain influences proprioceptive acuity in shoulder injuries . Thus, we focused the assessment on the proprioceptive information from the mechanoreceptors of the shoulder of patients with SAPS rather than the influence of the pain symptom.…”

“…We have chosen the shoulder rotation movement with intermediate angles to avoid causing pain in the patients, since it is already known that pain influences proprioceptive acuity in shoulder injuries. 8,19,25 Thus, we focused the assessment on the proprioceptive information from the mechanoreceptors of the shoulder of patients with SAPS rather than the influence of the pain symptom. Therefore, our findings suggest that the SAPS do not appear to involve damage in the mechanoreceptors or changes in the neural pathway due to the normal response of proprioception in pain-free movement.…”

“…For passive and active evaluation of medial rotation, the starting position was 50° of lateral rotation and the target position was 0°. These positions were chosen because it is considered that the intensity of pain in a greater range of motion could not be tolerated for the SAPS group and could interfere with the evaluation of proprioception . Three trials were performed for each target angle, for each type of repositioning, with a 1‐minute interval.…”

“…These positions were chosen because it is considered that the intensity of pain in a greater range of motion could not be tolerated for the SAPS group and could interfere with the evaluation of proprioception. 19 Three trials were performed for each target angle, for each type of repositioning, with a 1-minute interval. The absolute error was calculated for each repetition indicating the absolute difference in degrees between the target position and the corresponding position.…”