Background: The muscle quality of the rotator cuff (RC), measured by atrophy and fatty infiltration (FI), is a key determinant of outcomes in RC injury and repair. The ability to regenerate muscle after repair has been shown to be limited. Purpose: To determine if there is a source of resident endogenous stem cells, fibroadipogenic progenitor cells (FAPs), within RC injury patients, and if these cells are capable of adipogenic, fibrogenic, and pro-myogenic differentiation. Study Design: Controlled laboratory study. Methods: A total of 20 patients between the ages of 40 and 75 years with partial- or full-thickness RC tears of the supraspinatus and evidence of atrophy and FI Goutallier grade 1, 2, or 3 were selected from 2 surgeons at an orthopaedic center. During the surgical repair procedure, supraspinatus muscle biopsy specimens were obtained for analysis as were deltoid muscle biopsy specimens to serve as the control. FAPs and satellite cells were quantified using fluorescence-activated cell sorting. Muscle FI and fibrosis was quantified using Oil Red O and Masson trichrome staining. FAP differentiation and gene expression profiles were compared across tear sizes after culture in adipogenic, fibrogenic, and beta-3 agonist (amibegron) conditions. Analysis of variance was used for statistical comparisons between groups, with P < .05 as statistically significant. Results: Histologic analysis confirmed the presence of fat in biopsy specimens from patients with full-thickness tears. There were more FAPs in the full-thickness tear group compared with the partial-thickness tear group (9.43% ± 4.25% vs 3.84% ± 2.54%; P < .01). Full-thickness tears were divided by tear size, with patients with larger tears having significantly more FAPs than those with smaller tears. FAPs from muscles with full-thickness tendon tears had more adipogenic and fibrogenic potential than those with partial tears. Induction of a beige adipose tissue (BAT) phenotype in FAPs was possible, as demonstrated by increased expression of BAT markers and pro-myogenic genes including insulin-like growth factor 1 and follistatin. Conclusion: Endogenous FAPs are present within the RC and likely are the source of FI. These FAPs were increased in muscles with in larger tears but are capable of adopting a pro-myogenic BAT phenotype that could be utilized to improve muscle quality and patient function after RC repair.
Reported pain intensity depends not only on stimulus intensity but also on previously experienced pain. A painfully hot temperature applied to the skin evokes a lower subjective pain intensity if immediately preceded by a higher temperature, a phenomenon called offset analgesia. Previous work indicated that prior pain experience can also increase subsequent perceived pain intensity. Therefore, we examined whether a given noxious stimulus is experienced as more intense when it is preceded by an increase from a lower temperature. Using healthy volunteer subjects, we observed a disproportionate increase in pain intensity at a given stimulus intensity when this intensity is preceded by a rise from a lower intensity. This disproportionate increase is similar in magnitude to that of offset analgesia. We call this effect onset hyperalgesia. Control stimuli, in which a noxious temperature is held constant, demonstrate that onset hyperalgesia is distinct from receptor or central sensitization. The absolute magnitudes of offset analgesia and onset hyperalgesia correlate with each other but not with the noxious stimulus temperature. Finally, the magnitude of both offset analgesia and onset hyperalgesia depends on preceding temperature changes. Overall, this study demonstrates that the perceptual effect of a noxious thermal stimulus is influenced in a bidirectional manner depending upon both the intensity and direction of change of the immediately preceding thermal stimulus.
Background: Disparities associated with socioeconomic status (SES) and insurance coverage have been shown to affect outcomes in different medical conditions and surgical procedures. We hypothesized that patients insured by Medicaid will be associated with lower follow-up rates and inferior outcomes relative to those with Medicare or private insurance. Methods: Patients undergoing shoulder arthroplasty, including anatomic total shoulder arthroplasty, reverse arthroplasty, and hemiarthroplasty, were enrolled preoperatively in an institutional database. Preoperative demographics, payor (Medicaid, Medicare, or private insurance), and baseline American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) scores were recorded. Postoperatively, patients completed ASES scores at multiple time points. Follow-up completion rate was calculated as the number of follow-up visits completed relative to possible visits. Continuous variables were compared between groups with 1-way analyses of variance, and chi-squared tests were used for categorical variables. Significance was defined as P < .05. Results: There were 491 shoulder replacements performed for 438 patients from 2012-2017. The mean follow-up completed percentage was significantly lower (P < .001) for Medicaid patients (62.6% AE 33.7%) relative to Medicare patients (80.2% AE 26.7%; P < .001) and private insurance patients (77.8% AE 22.1%; P ¼ .001). The ASES Composite score increased significantly for all patients from baseline to final follow-up. At each time point, including before surgery and each postoperative time point, patients with Medicaid insurance had significantly lower ASES Composite scores. The final ASES Composite score was significantly lower in the Medicaid patients (66.1 AE 28.7) relative to private insurance patients (78.3 AE 20.8; P ¼ .023). Medicaid patients had significantly lower preoperative (P < .001) and postoperative (P ¼ .018) ASES Pain subscores. In multivariate regression analysis, Medicaid insurance was associated with both inferior preoperative and postoperative ASES scores relative to patients with Medicare or private insurance. Conclusions: We observed that all patients, regardless of insurance payor, improved by similar magnitudes after shoulder arthroplasty, though patients with Medicaid insurance had significantly lower preoperative and postoperative ASES scores, primarily because of the ASES Pain subscore. Patients with Medicaid insurance also have lower follow-up rates than other payors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.