Predictors of clinical outcomes after non-operative management of symptomatic full-thickness rotator cuff tears

BACKGROUND Previous studies have shown that non-surgical management can be an effective treatment strategy for many patients with rotator cuff tears.Despite the prevalence of rotator cuff disease,few studies have examined the patient and tear related factors that predict outcomes of nonsurgical management in this cohort of patients.AIM To identify factors that are associated with changes in patient reported outcomes over time in individuals with full-thickness rotator cuff tears treated without surgery.METHODS A cohort of 59 patients who underwent non-surgical management of full thickness rotator cuff tears with a minimum of 1-year follow-up were identified from our institutional registry.Patient demographics,comorbidities and tear characteristics were collected at initial presentation.Outcome measures were collected at baseline and at each clinical follow-up,which included Western Ontario Rotator Cuff(WORC)index,American Shoulder and Elbow Surgeons score,Visual Analog Scale for pain and Single Assessment Numerical Evaluation.Multi-and univariate regression analyses were used to determine the impact of each patient and tear related variable on final WORC scores and change in WORC scores throughout the study.RESULTS In this non-surgical cohort,all patient-reported outcome measures significantly improved compared to baseline at 1 and 2-year follow-up.There was no significant difference in outcomes between 1 and 2 years.The average improvement surpassed the published minimal clinically important differences values for WORC,American Shoulder and Elbow Surgeons,Visual Analog Scale pain and Single Assessment Numerical Evaluation scores.Regression analysis identified female gender(β=-19.88,P=0.003),smoking(β=-29.98,P=0.014)and significant subscapularis fatty infiltration(β=-15.35,P=0.024)as predictors of less favorable WORC scores at 1 year,and female gender(β=-19.09,P=0.015)alone as a predictor of lower WORC scores at 2 years.Patients with symptom duration greater than 1 year at presentation reported less improvement in WORC scores at 1-year follow-up(β=-14.63,P=0.052)and patients with traumatic tears reported greater improvements in WORC scores at 2-year follow-up(β=17.37,P=0.031).CONCLUSION Patients with full thickness rotator cuff tears can achieve and maintain clinically meaningful benefit from non-surgical management through 2-year follow-up.Female patients,smokers,and those with significant subscapularis fatty infiltration tend to have lower overall WORC scores at 1-year follow-up,and females also have lower WORC scores at 2-year follow-up.Patients presenting with symptoms greater than 1 year had less clinical improvement at 1-year follow-up,and those with traumatic tears had greater clinical improvement at 2-year follow-up.

An uneasy alliance:a nesting association between aggressive ants and equally fierce social wasps

Although the Neotropical territorially dominant arboreal ant Azteca chartifex Forel is very aggressive towards any intruder,its populous colonies tolerate the close presence of the fierce polistine wasp Polybia rejecta(F.).In French Guiana,83.33%of the 48 P.rejecta nests recorded were found side by side with those of A.chartifex.This nesting association results in mutual protection from predators(i.e.,the wasps protected from army ants;the ants protected from birds).We conducted field studies,laboratorybased behavioral experiments and chemical analyses to elucidate the mechanisms allowing the persistence of this association.Due to differences in the cuticular profiles of the two species,we eliminated the possibility of chemical mimicry.Also,analyses of the carton nests did not reveal traces of marking on the envelopes.Because ant forager flows were not perturbed by extracts from the wasps’Dufour’s and venom glands,we rejected any hypothetical action of repulsive chemicals.Nevertheless,we noted that the wasps"scraped"the surface of the upper part of their nest envelope using their mandibles,likely removing the ants'scent trails,and an experiment showed that ant foragers were perturbed by the removal of their scent trails.This leads us to use the term"erasure hypothesis."Thus,this nesting association persists thanks to a relative tolerance by the ants towards wasp presence and the behavior of the wasps that allows them to"contain"their associated ants through the elimination of their scent trails,direct attacks,"wing-buzzing"behavior and ejecting the ants.