In vivo 3-dimensional analysis of scapular and glenohumeral kinematics: comparison of symptomatic or asymptomatic shoulders with rotator cuff tears and healthy shoulders.

BACKGROUND: Alteration in shoulder kinematics has been suggested as one cause of symptoms in shoulders with rotator cuff tears (RCTs). However, only a few studies comparing symptomatic and asymptomatic RCTs using kinematic analysis have been performed. The purpose of this study was to compare 3-dimensional (3D) scapular and glenohumeral kinematics during scapular-plane abduction among symptomatic RCTs, asymptomatic RCTs, and healthy shoulders. METHODS: This study included 7 healthy shoulders in subjects with a mean age of 62 years, 5 symptomatic RCTs in subjects with a mean age of 70 years, and 7 asymptomatic RCTs in subjects with a mean age of 67 years. All shoulders with RCTs had medium-sized tears (1-3 cm in the coronal plane) that were confirmed with magnetic resonance imaging. Biplane fluoroscopic images during scapular-plane abduction were recorded, and computed tomography-derived 3D bone models were matched with the silhouettes of the bones on the fluoroscopic images using 3D/2-dimensional model-image registration techniques. Angular values of the scapula and glenohumeral kinematics were compared among the 3 groups. RESULTS: Posterior tilt of the scapula was significantly smaller in the symptomatic RCTs (3.1° ± 1.8°) than in healthy shoulders (10.4° ± 0.8°) (P = .049). The humerus of the symptomatic shoulders was less externally rotated relative to the scapula throughout the activity than the healthy shoulders and asymptomatic RCTs (P = .006 and P = .028 respectively). However, there were no kinematic differences between the asymptomatic RCTs and healthy shoulders. CONCLUSION: Kinematic changes in symptomatic RCTs might be associated with development of symptoms. Improvement of these kinematic changes may be a key to successful conservative treatment for symptomatic RCTs.

Sensory innervation of rat contracture shoulder model.

BACKGROUND: To date, few studies have investigated the cause of pain experienced by patients with frozen shoulder. The purposes of this study were to establish a rat contracture model and clarify the innervation pattern of the glenohumeral (GH) joint and subacromial bursa (SAB) using immunohistochemistry in the dorsal root ganglion (DRG) neurons. MATERIALS AND METHODS: The rat contracture models were made by tying the animal's humerus and scapula with No. 2-0 FiberWire (Arthrex, Naples, FL, USA). Contracture was confirmed on x-ray images taken 8 weeks after the operation. Subsequently, two kinds of neurotracers, Fluoro-Gold (FG) (Fluorochrome, Denver, CO, USA) and 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI) (Molecular Probes, Eugene, OR, USA), were used to detect the GH joints and SAB separately. FG tracers were injected into GH joints, and DiI tracers were injected into the SAB. At 7 days after injection, DRGs were harvested between C1 and T1. Immunohistochemistry by use of calcitonin gene-related peptide (CGRP) was performed. CGRP is thought to be one of the causes of pain sensation in joint disease. We evaluated the percentages of FG-labeled CGRP-immunoreactive (CGRP-ir) neurons in the total number of FG-labeled neurons and of DiI-labeled CGRP-ir neurons in the total number of DiI-labeled neurons. RESULTS: Abduction and total arc of the rotation were statistically significantly decreased in the contracture group. Furthermore, the percentage of CGRP-ir DRG neurons was significantly higher in the contracture group in both the GH joint and SAB. CONCLUSION: These results show that pain sensation in rat shoulder contracture may be induced by the up-regulation of CGRP expression in DRG neurons.

Efficacy of hyaluronic acid or steroid injections for the treatment of a rat model of rotator cuff injury.

This study evaluated dorsal root ganglia from C3-C7, analyzed gait, and compared the expression of calcitonin gene-related peptide (CGRP) which was a marker of inflammatory pain in a rat rotator cuff tear model in which the supraspinatus and infraspinatus tendons were detached; comparisons were made to a sham group in which only the tendons were exposed. Fluorogold was injected into the glenohumeral joint 21 days after surgery in both groups, and saline, steroids, or hyaluronic acid was injected into the glenohumeral joint in the rotator cuff tear group 26 days after surgery. The proportions of CGRP-immunoreactive neurons were higher and the gait parameters were impaired in the rotator cuff tear group compared to in the sham group. However, the CGRP expression was reduced and the gait was improved with steroid or hyaluronic acid injection compared to saline, suggesting that both hyaluronic acid and steroid injections suppressed of inflammation which thought to be provided pain relief. While there were no significant differences, the suppression of CGRP expression and the improved gait after hyaluronic acid and steroid injections suggested that both methods were effective for rat rotator cuff tear model.

Assessment of pain-related behavior and pro-inflammatory cytokine levels in the rat rotator cuff tear model.

The cause of pain following rotator cuff tear has not been fully elucidated. The purpose of this study was to evaluate behavior and inflammatory cytokines in a rat unstabilized rotator cuff defect (UCD) model. Forty-five Sprague-Dawley rats were divided into three groups: sham; UCD; and stabilized rotator cuff defect (SCD). Gait analysis was examined using CatWalk. Tumor necrosis factor (TNF)-α, interleukin(IL)-1ß, and IL-6 were measured within the subacromial bursa and the glenohumeral joint synovium at 21 and 56 days after surgery using an enzyme-linked immunosorbent assay (ELISA). Stride length, print area and contact intensity in the UCD group was significantly lower than in the sham group after surgery. Stride length, print area and contact intensity in the SCD group was significantly higher than in the UCD group. In contrast, TNF-α, IL-1ß, and IL-6 in the UCD group was significantly higher than in the sham group at days 21 and 56. However, TNF-α, IL-1ß, and IL-6 in the SCD group was significantly lower than in the UCD group at days 21 and 56. The present results suggest that SCD is effective not only in improving shoulder function but also in reducing inflammatory cytokines, which may serve as one source of pain due to rotator cuff tear.