Introduction

Rotator cuff tears (RCTs) are a common shoulder condition, particularly prevalent among older individuals1. Prior research has indicated that several factors may contribute to the development of RCTs, including age1,2, sex3, smoking4,5, and posture6. These factors interplay in complex ways, influencing the risk and severity of tears. RCTs are associated with significant pain and dysfunction in the shoulder, often leading to limitations in daily activities and quality of life for those affected.

Numerous studies have reported on the prevalence of rotator cuff tears identified through cadaver dissections, revealing a wide range of frequencies from 5 to 39% depending on the specific study7,8. This variability may stem from differences in the subject populations examined, including their age, level of physical activity, and underlying health conditions9,10. Moreover, the background of patients with rotator cuff tears, including the specific symptoms they experience and any history of trauma, often remains unclear due to the inherent limitations of cadaveric research. Recent findings have highlighted the existence of asymptomatic rotator cuff tears, suggesting that many individuals may have tears without any noticeable symptoms9,11,12,13.

Traditional studies have predominantly focused on symptomatic patients, which can lead to a skewed understanding of the overall clinical picture of rotator cuff tears9,13,14. This narrow focus may overlook the significant number of individuals who have tears but do not report any pain or functional impairment. Furthermore, the epidemiology of rotator cuff tears has not been thoroughly elucidated, leaving gaps in our understanding of how these injuries manifest across different demographics15,16.

To gain a more comprehensive understanding of the risk factors associated with rotator cuff tears and to explore the relationship between tears and various patient backgrounds, a survey was conducted involving a diverse range of subjects from the general population, irrespective of whether they reported shoulder symptoms. This approach aims to provide a more representative picture of rotator cuff tears in the community, helping to clarify risk factors and prevalence rates that may not be apparent when only considering symptomatic individuals. By including asymptomatic cases, this research could yield valuable insights into the true burden of rotator cuff tears and inform strategies for prevention and management.

Materials and methods

This cross-sectional investigation employed a self-administered questionnaire (in paper format) to gather detailed information about RCT and their individual and physical factors across eight orthopedic and rehabilitation centers located in four provinces of Syria: Damascus, Aleppo, Homs, and Latakia, with two centers chosen from each province.

The variables included in the questionnaire were selected based on findings from previous studies, and input from the clinician experts. Subsequently, a pilot study of the assessment form was conducted among 20 patients to analyze the inter-evaluator reliability. The assessment of interexaminer reliability was performed using the intraclass correlation coefficient (ICC), and variables were included in the assessment instrument when obtained ICC values were classified as having good or excellent reliability (ICC ≥ 0.83).

The study included patients who attended these centers between October 2021 and November 2022. All participants were informed about the publication of their data and provided their consent to take part in the research. Participants completed a questionnaire that included queries about their age, gender, dominant arm, the intensity of physical labor (subjectively categorized as light, moderate, or heavy), history of shoulder trauma, and any current shoulder symptoms. They then underwent physical assessments on both shoulders, which included testing for impingement signs, measuring active range of motion, and evaluating muscle strength loss. The impingement sign was assessed using Neer’s test17, while the active range of motion was measured in forward elevation at the scapular plane with the participant standing upright. Muscle strength loss was determined in the abduction and external rotation, defined as any score below 5 on a manual muscle testing scale from 0 to 5.

Ultrasonography was performed on both shoulders to diagnose RCT, following the methodology outlined by Middleton et al.18, utilizing a LOGIQ e device (GE Health Care, USA) with linear-array probes set at 12 MHz. To minimize interobserver variability, all ultrasonographic evaluations were conducted by a single experienced shoulder surgeon who was unaware of the other evaluation components. According to Takagishi et al.19, signs of discontinuity and thinning in the rotator cuff were interpreted as evidence of full-thickness rotator cuff tears. Participants were categorized into two groups based on the ultrasonographic findings: those with a rotator cuff tear (the “RCT group”) and those without (the "non-tear group").

Inclusion criteria required that participants complete all assessments within the study. Individuals with a prior history of shoulder dislocation or surgical interventions were excluded before or during the study period. This research was reviewed and approved by the Institutional Review Board of Neijiang Normal University (Consent Letter NUU – IRB 202,404,084). All procedures adhered to the ethical standards outlined in the 1964 Declaration of Helsinki and the STROBE guidelines for observational studies. Informed consent was obtained from all participants and their legal guardians.

Statistical analysis

Numerical variables have been summarized by calculating the standard deviation and mean. A preliminary descriptive analysis was performed, followed by comparisons between groups of respondents using the Student’s t-test for numerical variables and the chi-square test or simple logistic regression for categorical variables. Factors that demonstrated a significant association (P < 0.05) with RCT in the bivariate analysis were further examined using multiple logistic regression analysis. Odds ratios were computed to assess the relative likelihood of experiencing RCT about the presence of specific factors. All statistical analyses were conducted using SPSS software, with a significance threshold of P < 0.05.

Results

Participant demographics

The RCT group represented 31.3% (148 out of 472 shoulders) of the participants, while the non-tear group made up 68.7% (324 out of 472 shoulders). The proportion of individuals in the RCT group across different age brackets was 0% for those in their 20s (0 out of 4 shoulders), 14.2% for those in their 30s (4 out of 28 shoulders), 21.7% for individuals in their 40s (10 out of 46 shoulders), 26.2% in their 50s (42 out of 160 shoulders), 23.6% in their 60s (34 out of 144 shoulders), 26.8% in their 70s (22 out of 82 shoulders), and 25% in their 80s (2 out of 8 shoulders), indicating a rise in prevalence with advancing age (Fig. 1).

Fig. 1
figure 1

The percentage of the ‘‘RCT group’’ and ‘‘Non-tear group’’ in each generation, the RCT group included of 20.7% of all subjects and the prevalence increased with age.

Full size image

Symptomatology and tear prevalence

The survey results indicated that 41.25% (66 out of 160 shoulders) of subjects experiencing current symptoms had rotator cuff tears, whereas 26.29% (82 out of 312 shoulders) of asymptomatic subjects also had tears (Table 1). Significant differences were noted between the two groups in all evaluated parameters: age (average 64.6 years in the RCT group vs. 57.9 years in the non-tear group, P = 0.005), gender distribution (males: 31.1% in the RCT group and 43.8% in the non-tear group, P = 0.04), dominant arm usage (dominant arm: 77.1% in the RCT group vs. 54.9% in the non-tear group, P = 0.037), labor intensity (light/intermediate/heavy: 14.9%/55.4%/29.7% in the RCT group vs. 14.8%/51.8%/33.4% in the non-tear group, P = 0.005 ), history of trauma (present: 9.4% in the RCT group and 7.4% in the non-tear group, P = 0.026), impingement sign (positive: 17.6% in the RCT group vs. 17.9% in the non-tear group, P = 0.004), active forward elevation (148.6 degrees in the RCT group and 154.1 degrees in the non-tear group, P = 0.029), weakness in abduction (present: 25.1% in the RCT group and 10.6% in the non-tear group, P = 0.017), and weakness in external rotation (present: 21.6% in the RCT group and 17.3% in the non-tear group, P < 0.020) (Table 2).

Table 1 Relationship between rotator cuff tear and symptom.
Full size table
Table 2 Relationship between rotator cuff tear and evaluation items.
Full size table

Logistic regression analysis

Logistic regression analysis indicated that a history of trauma, dominant arm, and age were significantly linked to the risk of rotator cuff tear. The odds ratios for a history of trauma were 2.74 (95% CI 2.36–2.92); for the dominant arm, it was 2.25 (95% CI 2.10–2.68), and for age, it was 1.76 (95% CI 1.82–2.04) (Table 3). Based on these findings, we explored the connections among age, dominant arm, and history of trauma within the RCT group. For participants under 49 years, rotator cuff tears were more closely associated with dominant arm usage (85.7% in those under 49 years vs. 69.7% in those over 50, P = 0.021) and a history of trauma (16.4% in those under 49 vs. 22.3% in those over 50, P = 0.042) (Table 4).

Table 3 Risk factors for rotator cuff tear.
Full size table
Table 4 Relationship among age, dominant arm, and history of trauma in RCT group.
Full size table

Discussion

Prevalence of rotator cuff tears

Few studies have examined the prevalence and risk factors linked to rotator cuff tears (RCT). Minagawa et al. reported that an ultrasound screening conducted during community health check-ups revealed that 21.7% of 1,328 shoulders had full-thickness rotator cuff tears. Furthermore, the prevalence of tears among different age groups was 0% for those under 50, 10.7% for those in their 50s, 15.2% for those in their 60s, 26.5% for those in their 70s, and 36.6% for individuals over 8020.The present study found that 31.6% of participants had full-thickness rotator cuff tears, with the incidence also rising with age, showing only slight variation from earlier cadaveric studies. The prevalence of rotator cuff tears may vary based on the age distribution of the community or the predominant industries in an area; thus, further research in different settings, such as urban areas, is warranted.

Asymptomatic rotator cuff tears

Several studies have reported the presence of asymptomatic rotator cuff tears21,22,23. For instance, Sher et al. found that 15% of 96 asymptomatic volunteers had full-thickness rotator cuff tears detected via Magnetic Resonance Imaging (MRI)21. Additionally, Tempelhof et al.22 and Schibany et al.23 reported that 23% of 411 subjects and 6% of 212 subjects, respectively, had full-thickness tears identified through ultrasound. However, these studies focused exclusively on asymptomatic individuals, leaving the true prevalence of asymptomatic tears in the general population unclear. In the current study, 41.2% of symptomatic patients had rotator cuff tears, while the overall prevalence of asymptomatic rotator cuff tears was found to be 26.3% (41 out of 236 shoulders). This distinction emphasizes the need to separately evaluate symptomatic and asymptomatic rotator cuff tears to understand their respective impacts on shoulder health.

Risk factors for rotator cuff tears

Rotator cuff tears can result from acute injuries but are primarily attributed to age-related degenerative changes17. Various factors contribute to the pathogenesis of rotator cuff tears, including external factors such as subacromial and internal impingement, tensile overload, and repetitive stress17,24,25, as well as internal factors like poor vascularity, changes in material properties, matrix composition, and aging26,27,28

The current study statistically identified significant risk factors for rotator cuff tears in the general population, including a history of trauma, dominant arm use, and age. Notably, in individuals under 49, rotator cuff tears were more strongly linked to dominant arm use and a history of trauma. This highlights the relevance of dominant arm as a critical factor influencing the risk of rotator cuff injuries.

Dominant arm use can significantly increase the risk of RCT through several biomechanical and occupational mechanisms. Biomechanically, the dominant arm often experiences greater mechanical loads during activities, leading to asymmetrical load distribution that can result in microtrauma over time29. Altered kinematics associated with dominant arm use may also contribute to this risk, as repetitive overhead motions can lead to increased impingement and injury30. Furthermore, muscle imbalances from frequent use of the dominant arm can compromise shoulder stability, heightening the risk of rotator cuff injuries31. From an occupational perspective, tasks that require extensive use of the dominant arm, particularly in physically demanding roles such as construction or sports, can lead to cumulative trauma. These occupations often expose individuals to additional risk factors, such as awkward postures and repetitive strain, which can exacerbate tendon degeneration32. Additionally, fatigue from prolonged use of the dominant arm can impair muscle function and coordination, further increasing the likelihood of injury33.The findings of the current study suggest that both internal and external factors contribute to the occurrence of rotator cuff tears. However, it is important to differentiate between the factors influencing symptomatic and asymptomatic tears. External factors being more relevant in younger patients these findings consistent with previous studies, where Petersson et al. demonstrated that external factors contribute to the occurrence of rotator cuff tear8. while Schibany et al. presented that internal factor contribute to the occurrence of rotator cuff tears23. Furthermore Fehringer et al. assessed a simple shoulder test, Constant score, and ultrasound in 200 patients aged 65 and older, regardless of shoulder symptoms, and found that those with rotator cuff tears had lower scores than those without34. The current results indicated that subjects with rotator cuff tears tested positive for impingement signs and exhibited reduced active forward elevation, along with decreased muscle strength in abduction and external rotation. While these simple tests proved useful for detecting rotator cuff tears in the general population, they do not encompass the entire range of shoulder function. This study highlighted the risk factors associated with rotator cuff tears and the prevalence of asymptomatic tears among Syrian patients. However, the distinctions between asymptomatic and symptomatic tears remain crucial for understanding their implications on treatment and recovery. Further investigation is ongoing into the mechanisms that lead to symptoms in these patients.

Limitations

This study has several limitations. First, the sample size, while adequate, may not fully represent the broader population, affecting the generalizability of the findings. Second, the cross-sectional design restricts the ability to establish causality between identified risk factors and the occurrence of rotator cuff tears, highlighting the need for longitudinal studies to better understand these relationships. Additionally, potential recall bias may have influenced the self-reported history of trauma among participants. Individuals may not accurately remember past injuries or may underreport them, which could skew the data on trauma history. Moreover, recruiting participants from conflict-affected regions presents its own set of challenges. Issues related to accessibility, safety, and willingness to participate may limit the diversity and representativeness of the sample. Finally, variability in imaging techniques among participants may lead to discrepancies in the detection of tears, further complicating the interpretation of results.

Conclusion

This study addresses the risk factors of RCT in Syrian patients, regardless of symptoms. Our results revealed that history of trauma, the dominance of the affected arm, and age were identified as significant contributors to RCT. The study’s findings shed light on both symptomatic and asymptomatic tears, emphasizing the complex interplay of internal and external factors in their development. Diagnostic indicators like impingement sign positivity and muscle weakness provide valuable insights for the early detection and management of RCT patients.