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Abstract

Purpose:

Rotator cuff tears (RCTs) occur commonly, especially among certain groups of individuals. In this meta-analysis, we aim to identify risk factors for RCTs.

Methods:

We searched MEDLINE for 210 articles. Seventeen articles were selected for systematic review, of which 10 were eligible for meta-analysis. Data was analysed with Review Manager 5.3, using Mantel–Haenszel statistics and random effect models.

Results:

A total of 6653 individuals were analysed. The odds of sustaining a RCT on the dominant hand was 2.30 times more than the non-dominant hand (95% confidence interval (CI): 1.01–5.25, Z = 1.99, p = 0.05; Heterogenity: τ ² = 0.38, χ ² = 8.84, df = 2 (p = 0.01), I ² = 77%). The odds of an individual aged 60 years and above sustaining a RCT was 5.07 times higher than an individual less than 60 years old (95% CI: 2.45–10.51, Z = 4.37, p < 0.001; Heterogenity: τ ² = 0.47, χ ² = 25.24, df = 3 (p < 0.001), I ² = 88%). Female gender was not a significant association, with an odds ratio of 0.98 when compared to the male gender (95% CI: 0.66–1.45, Z = 0.09, p = 0.93; Heterogenity: τ ² = 0.20, χ ² = 44.24, df = 5 (p < 0.001), I ² = 89%).

Conclusions:

Hand dominance and older age are associated with RCTs. More studies are required for further assessment of associations and risk factors of RCTs.

Keywords

age gender hand dominance risk factors rotator cuff tears rotator cuff tendinopathy shoulder injury

Introduction

Rotator cuff tears (RCTs) are one of the more frequent pathologies within the shoulder girdle.¹ A significant number of such tears are asymptomatic. At any given time, the prevalence of asymptomatic RCTs is greater than that of symptomatic RCTs.² Many RCTs also cause restriction of shoulder function.³ Epidemiologically, their prevalence increases with age, with 54% of asymptomatic patients aged 60 years and greater having sustained either a partial or complete RCT on magnetic resonance imaging.⁴ Ultrasound (US) studies by Tempelhof et al. reveal that 13% of individuals in their fifth decade, 20% in their sixth decade and 31% in their seventh decade of life have RCTs.⁵ From their study on 306 cadavers, Löhr and Uhthoff noted a 19% and 32% prevalence of full and partial thickness tears, respectively.⁶ As the prevalence of RCTs is high within the general population, it is imperative to define risks and associations related to RCTs in the general population.

There have been various factors described to be associated with RCTs. The objective of this study is to synthesize the published literature regarding associations with RCTs in the form of a systematic review and meta-analysis. Where possible, we aimed to identify quantified overall estimates for associations with RCTs. This would provide an evidence-based foundation from which healthcare professionals can assess an individual’s risk of having an RCT at the point of consultation.

Methods

We searched Pubmed/MEDLINE (1956 to 11 February 2015) for publications in any language that recorded associations between identifiable risk factors and RCTs. Our search term was as follows: ‘(rotator cuff tear OR rotator cuff tendinopathy OR rotator cuff tendinitis) AND (risk factor)’. We also extracted and included the relevant citations of systematic reviews within our list for our review.

Out of the 210 studies we obtained, we selected all studies related to RCTs, rotator cuff tendinitis and their risk factors. We assessed the quality of these studies with a scoring system, adapted from Duckitt et al.,⁷ paying attention to participant selection (assessing the way in which participants were selected, comparing the potential extent of representation of study population to general population), comparability of groups being studied, study population size, study design and how the diagnosis of RCTs were made (Table 1). The maximum score a paper could obtain was 11 points. We excluded any study that failed our scoring system (< 6 points).

Table 1.

Rubric of assessment system.

Assessment system
Participant selection
	Cohort studies Selected cohort was representative of general population (1) Cohort was a selected group or the selection of the group was not described (0) Case-control studies Cases and controls drawn from the same population (1) Cases and controls drawn from different sources or the selection of groups was not described (0)
Comparability of groups
	No differences between groups explicitly reported (especially in terms of age, gender, BMI, comorbidities) unless it was one of the variables that was under investigation, or such differences were adjusted for (2) Differences between groups were not recorded (1) Groups differed (0)
Size
	>100 participants in each group (2) <100 participants in each group (1)
Cohort design
	Prospective cohort design (2) Retrospective design (1)
Outcomes section 1
	Definition and classification of rotator cuff tear References definition (2) Explicit definition that included complete and partial rotator cuff tears (1) Rotator cuff tears not defined and/or classified (0)
Outcomes section 2
	How the diagnosis of rotator cuff tear was made Arthroscopy (2) MRI or ultrasound (1) Clinical examination/process was not described (0)

Data analysis was carried out using Review Manager 5.3.⁸ Where papers contained raw data, we calculated the unadjusted odds ratios (ORs) with 95% confidence intervals via Mantel–Haenszel statistics. We took into account random effects within our analysis model. For combined studies, we calculated the I², statistic for combined studies,⁹ which takes into account the proportion of total variation in study estimates as a result of heterogeneity of the studies included. For certain studies, we were unable to combine data. For such studies, we described the results from the studies along with their published ORs or relative risks (adjusted or crude). For factors in which data was combined from studies, Forrest Plots are displayed.

Results

We identified 230 studies. After screening titles, we read 92 abstracts. We subsequently excluded 48 further studies as they were cadaveric studies, had no data analyses regarding rotator cuff tendinopathies, had poor or no data analysis techniques or were not written in English. We read 44 full-text articles, of which 5 were removed as they were either systematic reviews or meta-analyses.

We scored the remaining 39 articles based on our adapted assessment system. Details of our scoring system can be found in Table 1. The maximum number of points a paper could score was 11 points. Sixteen articles were removed as they failed our scoring system (<6 points). Details regarding the individual scores of the 39 papers can be found in Table 2.

Table 2.

Score breakdown for selected studies based on selection criteria.

Authors	Selection	Comparability	Size	Outcome 1 (definition and classification)	Outcome 2 (mode of diagnosis)	Cohort design	Overall score
Abate et al.¹⁰	1	0	2	2	1	1	(7/11)
Akbar et al.¹¹	1	0	2	0	1	1	(5/11)
Andersen and Gaardboe, 1993¹²	0	1	1	0	0	1	(3/11)
Bahrs et al.¹³	0	0	2	1	1	1	(5/11)
Banas et al.¹⁴	1	1	1	2	1	1	(7/11)
Baumgarten et al.¹⁵	1	0	2	2	1	1	(7/11)
Berbig et al.¹⁶	1	0	2	2	1	2	(8/11)
Bodin et al.¹⁷	1	0	2	2	1	2	(8/11)
Bodin et al.¹⁸	1	0	2	2	1	1	(7/11)
Carbone et al.¹⁹	1	0	2	2	2	1	(8/11)
Gumina et al.²⁰	1	1	2	2	2	1	(9/11)
Gumina et al.²¹	1	1	2	2	2	1	(9/11)
Gumina et al.²²	1	2	2	2	2	1	(10/11)
Gwilym et al.²³	1	1	1	2	1	1	(7/11)
Harvie et al.²⁴	1	1	2	2	1	1	(8/11)
Kaergaard et al.²⁵	0	2	2	0	0	2	(6/11)
Kaerlev et al.²⁶	0	0	2	0	1	1	(4/11)
Kang et al.²⁷	1	2	1	2	1	1	(8/11)
Milgrom et al.²⁸	1	0	1	1	1	1	(5/11)
Miranda et al.²⁹	1	0	2	2	0	1	(6/11)
Motta et al.³⁰	1	0	2	0	1	1	(5/11)
Oliva et al.³¹	1	0	2	0	2	1	(6/11)
Park et al.³²	1	1	2	0	0	1	(5/11)
Porcellini et al.³³	1	1	1	1	2	1	(7/11)
Rechardt et al.³⁴	1	0	2	1	0	1	(5/11)
Robinson et al.³⁵	1	1	2	2	0	1	(7/11)
Rocquelaure et al.³⁶	1	0	2	2	1	1	(7/11)
Sorensen et al.³⁷	1	0	1	1	1	1	(5/11)
Seidler et al.³⁸	0	0	2	1	1	1	(5/11)
Stenlund et al.³⁹	1	1	1	1	0	1	(5/11)
Teerlink et al.⁴⁰	0	1	2	1	1	1	(6/11)
Tempelhof et al.⁵	1	0	2	2	1	1	(7/11)
Tetreault et al.⁴¹	0	1	1	0	1	1	(4/11)
Titchener et al.⁴²	0	1	2	0	0	1	(4/11)
Wendelboe et al.⁴³	0	2	2	0	1	1	(6/11)
Worland et al.⁴⁴	1	0	1	1	1	1	(5/11)
Yamamoto et al.⁴⁵	1	0	2	2	1	1	(7/11)
Yi et al.⁴⁶	0	2	1	0	1	1	(5/11)

Six other articles were removed as there was no analysis regarding RCTs (i.e. only other forms of rotator cuff tendinopathies, such as rotator cuff tendinitis, were discussed). A total of 17 articles were available for our qualitative synthesis, of which, 10 articles were used for the meta-analysis. Details regarding the included studies can be found in Table 3. A list of excluded studies is available upon request. The Prisma diagram in Figure 1 summarizes the article selection process for the systematic review and meta-analysis.

Table 3.

Characteristics of included studies.

Characteristics of included studies
Authors, year of study	Methods and study design	Participants	Outcome assessment	Diagnosis method
Abate et al., 2010⁴⁷	Case-control retrospective study	48 cases and 32 controls	Asymptomatic RCTs in elderly individuals with diabetes	Ultrasound imaging
Abate et al., 2014¹⁰	Case-control retrospective study	110 cases and 122 controls	Asymptomatic RCTs in postmenopausal women	Ultrasound imaging
Baumgarten et al., 2010¹⁵	Case-control retrospective study	375 cases and 211 controls	RCTs in smokers	Ultrasound imaging
Berbig et al., 1999¹⁶	Case-control prospective study	167 cases and 93 controls	RCTs in individuals with primary anterior shoulder dislocations	Ultrasound imaging
Carbone et al., 2012¹⁹	Case-control retrospective study	131 cases and 277 controls	RCTs in smokers	Arthroscopic evaluation
Gumina et al., 2013²¹	Case-control retrospective study	408 cases and 201 controls	RCTs in individuals with arterial hypertension	Arthroscopic evaluation
Gumina et al., 2013²⁰	Case-control retrospective study	586 patients studied No data on number of cases and controls	RCTs in the elderly	Arthroscopic evaluation
Gumina et al., 2014²²	Case-control retrospective study	381 cases and 220 controls	Associations of body fat with RCTs	Arthroscopic evaluation
Gwilym et al., 2009²³	Case-control prospective study	62 cases and 68 controls	Genetic influences on RCTs	Ultrasound imaging
Harvie et al., 2004²⁴	Case-control retrospective study	205 probands, 129 siblings and 150 spouses	Genetic influences on RCTs	Ultrasound imaging
Kang et al., 2010²⁷	Case-control retrospective study	80 cases and 339 controls	RCTs in diabetic patients	Ultrasound imaging
Porcellini et al., 2006³³	Cohort retrospective study	50 patients with shoulder instability, 50 patients with complete cuff tear and 50 patients with both shoulder instability and complete cuff tear	RCTs in patients aged 40–60 years old	Arthroscopic evaluation
Robinson et al., 2012³⁵	Cohort retrospective study	3633 patients	RCTs in individuals with traumatic anterior glenohumeral dislocations	Ultrasound imaging and MR imaging
Schibany et al., 2003⁴⁸	Cohort retrospective study	212 individuals	RCTs in asymptomatic individuals	Ultrasound and MR imaging
Teerlink et al., 2015⁴⁰	Case-control retrospective study	175 cases and 2595 controls	Association of RCTs and estrogen-related receptor-beta	MRI imaging
Tempelhof et al., 1999⁵	Cohort retrospective study	411 individuals	Age-related prevalence of RCTs in asymptomatic individuals	Ultrasound imaging
Yamamoto et al., 2010⁴⁵	Cohort retrospective study	683 individuals	RCTs in general population	Ultrasound imaging

RCTs: rotator cuff tears; MR: magnetic resonance.

Figure 1.

PRISMA diagram outlying flow of article selection.

A summary of our systematic review findings can be found in Table 4. From our systematic review, we noted that there were only five factors, which had a statistically significant calculated ORs, namely age above 60 years (OR = 5.07, 95% CI: 2.45–10.51), dominant hand (OR = 2.30, 95% CI: 1.01–5.25), overweight body mass index (BMI) (OR = 2.35, 95% CI: 1.65–3.40), tobacco smoking (OR = 1.74, 95% CI: 1.25–2.43) and hypertension (OR = 1.93, 95% CI: 1.36–2.74). However, for most of the parameters, there are insufficient populations being studied to make a synthesized conclusion of their extent of effect towards contribution to RCTs.

Table 4.

Summary of results from systematic review.^a

Outcome a Assessed	No. of studies	No. of participants with assessed outcome/ total no. of participants (%)	Unadjusted odds ratio (95% CI)	I2 (%) (overall effect p value)	Individual study risk (odds ratio or relative risk or mean difference), 95% CI
Female gender^{5,20,24,33,35,45}	6	3098/6653 (46.6)	0.98 (0.66–1.45)	89 (0.93)	1.03 (0.65–1.64),⁵ 1.02 (0.73–1.43),²⁰ 0.73 (0.50–1.06),²⁴ 0.95 (0.45–2.03),³³ 1.68 (1.45–1.96),³⁵ 0.68 (0.52–0.90)⁴⁵
Age 60 years and above^5,16,24,45	4	1139/2316 (49.2)	5.07 (2.45–10.51)	88 (<0.001)	2.87 (1.70–4.85),⁵ 23.39 (10.03–54.56),¹⁶ 2.35 (1.41–3.92),²⁴ 5.46 (4.04–7.38)⁴⁵
Dominant hand^10,16,45	3	1006/1997 (50.4)	2.30 (1.01–5.25)	77 (0.05)	13.89 (3.25–59.36),¹⁰ 1.42 (0.73–2.75),¹⁶ 1.58 (1.21–2.06)⁴⁵
Overweight bmi²²	1	440/601 (73.2)	2.35 (1.63–3.40)	Na (<0.001)	2.35 (1.63–3.40)²²
Tobacco smoking¹⁵	1	333/584 (57.0)	1.74 (1.25–2.43)	Na (0.001)	1.74 (1.25–2.43)¹⁵
Hypertension²¹	1	294/609 (48.3)	1.93 (1.36–2.74)	Na (<0.001)	1.93 (1.36–2.74)²¹
Diabetes mellitus²⁷	1	91/453 (20.1)	0.96 (0.41–2.26)	Na (0.92)	0.96 (0.41–2.26)²⁷

BMI: body mass index; CI: confidence interval.

^a I ² for overweight BMI, tobacco smoking, hypertension and diabetes mellitus were not applicable as there was only one study within our included studies that analysed each factor. Hence, there was no heterogeneity of studies to be assessed.

From the systematic review, we further analysed the age of patients (Table 5), hand dominance (Table 6) and gender of patients (Table 7) in relation to their influence on RCTs. In all, taking into consideration random effects, females had an OR of 0.98 (95% CI: 0.66–1.45, Z = 0.09, p = 0.93) revealing that gender may not be a significant parameter for RCTs based on the current data. However, hand dominance and the age of patient were revealed to be significant factors with respect to sustaining RCTs. Total OR for dominant hand was 2.30 (95% CI: 1.01–5.25, Z = 1.99, p = 0.05). A significant level of inter-study heterogeneity was noted (τ ² = 0.20, χ ² = 44.24, df = 5 (p < 0.00001), I ² = 89%). A more substantial relationship was noted between a greater age of patient and RCTs. The total OR for individuals aged 60 years and above sustaining an RCT was 5.03 (95% CI: 2.45–10.51, Z = 4.37, p < 0.0001). A significant level of inter-study heterogeneity was also noted (τ ² = 0.47, χ ² = 25.24, df = 3 (p < 0.0001), I ² = 88%).

Table 5.

Forest plot synthesizing overall odds ratio for RCT in individuals aged 60 years and above.

	Experimental		Control			Odds ratio	Odds ratio
Study or subgroup	Events	Total	Events	Total	Weight (%)	M–H, random, 95% CI	M–H, random, 95% CI
Berbig et al.¹⁶	58	109	7	151	21.0	23.39 [10.03, 54.56]
Harvie et al.²⁴	82	168	32	111	25.6	2.35 [1.41, 3.92]
Tempelhof et al.⁵	74	244	22	167	25.4	2.87 [1.70, 4.85]
Yamamoto et al.⁴⁵	216	618	67	748	27.9	5.46 [4.04, 7.38]
Total (95% CI)		1139		1177	100	5.07 [2.45, 10.51]
Total events	430		128

CI: confidence interval; M–H: Mantel–Haenszel. Heterogeneity: τ² = 0.47; χ² = 25.24, df = 3 (p < 0.0001); I ² = 88%. Test for overall effect: Z = 4.37 (P < 0.0001).

Table 6.

Forest plot synthesizing overall OR for RCT in dominant hand.

	Dominant hand		Non-dominant hand			Odds ratio	Odds ratio
Study or subgroup	Events	Total	Events	Total	Weight (%)	M–H, random, 95% CI	M–H, random, 95% CI
Abate et al.⁴⁷	25	232	2	232	19.1	13.89 [3.25, 59.36]
Berbig et al.¹⁶	32	91	21	76	36.1	1.42 [0.73, 2.75]
Yamamoto et al.⁴⁵	167	683	116	683	44.8	1.58 [1.21, 2.06]
Total (95% CI)		1006		991	100	2.30 [1.01, 5.25]
Total events	224		139

OR: odds ratio; RCT: rotator cuff tear; CI: confidence interval; M–H: Mantel–Haenszel. Heterogeneity: τ² = 0.38; χ² = 8.84, df = 2 (P = 0.01); I ²=77%. Test for overall effect: Z = 1.99 (P = 0.05).

Table 7.

Forest plot synthesizing overall OR for RCT in Female Gender.

	Experimental		Control			Odds ratio	Odds ratio
Study or subgroup	Events	Total	Events	Total	Weight (%)	M-H, random, 95% CI	M-H, random, 95% CI
Gumina et al.^20,21	209	311	199	298	17.6	1.02 [0.73, 1.43]
Harvie et al.²⁴	145	233	174	251	17.0	0.73 [0.50, 1.06]
Porcellini et al.³³	27	41	73	109	11.5	0.95 [0.45, 2.03]
Robinson et al.³⁵	442	1383	491	2250	19.6	1.68 [1.45, 1.96]
Tempelhof et al.⁵	52	220	44	191	15.8	1.03 [0.65, 1.64]
Yamamoto et al.⁴⁵	169	910	114	456	18.4	0.68 [0.52, 0.90]
Total (95% CI)		3098		3555	100	0.98 [0.66, 0.45]
Total events	1044		1095

OR: odds ratio; RCT: rotator cuff tear; CI: confidence interval; M–H: Mantel–Haenszel.

Heterogeneity: τ ² = 0.20; χ ² = 44.24, df = 5 (p = 0.00001); I ² = 89%. Test for overall effect: Z = 0.09 (P = 0.93).

Discussion

The results in our study conclude that both the dominant hand and older age are associated with higher odds of sustaining an RCT. Within our study, factors such as a high BMI, hypertension and smoking were not considered to be associations with RCTs as they were only reported in one article each and hence could not be generalized sufficiently to the rest of the international population.

Benson et al.⁴⁹ discuss that the aetiologies of RCTs are multifactorial. The aetiologies for RCTs revolve around both homeostasis of normal tissue and elimination pathways for damaged and superfluous cells. Any disruption in such homeostasis and elimination pathways can result in rotator cuff tendon degeneration. It extreme cases, this tendon degeneration can present as RCTs. Disruptions in homeostasis, from the pathophysiological perspective, result in excessive apoptosis within the tendon itself. Case in point, the number of apoptotic cells in the torn aspects of the rotator cuff tendons has been shown to be double that of normal tendons.⁵⁰ The role of apoptosis has also been proven by animal studies revealing apoptotic gene upregulation and eventual increased apoptosis upon high strain and overuse.^51,52 Apoptosis in itself is a process of programmed cell death.^53,54 It is prompted by a variety of chemical signals, such as glucocorticoids, growth factor withdrawal, reactive oxygen species and cytokines.⁵⁵

Hand dominance and older age were both noted to be significantly associated with RCTs. The dominant hand had more than double the odds of sustaining an RCT as compared to the non-dominant hand, while an individual aged 60 years or above was approximately at a five-time higher odds of sustaining an RCT as compared to an individual less than 60 years old. Both these observations can be explained by the increased apoptotic activities observed under such circumstances. The dominant hand tends to be utilized more than the non-dominant hand and hence tends to be placed under higher stress. This increases apoptosis at the sites of increased stress. RCTs predictably will occur at the site of highest stress.

Tendons in the elderly have a significantly compromised microvascular system making the patient more prone to degeneration, microtears, calcification, fibrovascular proliferation and general insult. All these pathways place the elderly at higher risk of sustaining RCTs.^56,57 A study performed by Milgrom et al. revealed that the prevalence of both partial- and full-thickness RCTs increased markedly after 50 years of age and that these findings were present in more than 50% of dominant shoulders in the seventh decade of life and in 80% of participants over 80 years of age.²⁸ Yamaguchi et al.⁵⁸ noted that the average age for an individual without an RCT was 48.7 years, 58.7 years for those with a unilateral tear and 67.8 years for those with a bilateral tear. Moreover, further logistic regression analysis revealed a 50% likelihood of a bilateral RCT at 66.0 years of age (p < 0.01).

Factors such as diabetes mellitus, hypertension, smoking and older age prompt such chemical signals, induce excessive apoptosis and consequently impede current elimination pathways via poor vascularity, alterations in material properties as well as matrix composition changes and consequently. Although we did not consider a high BMI, hypertension, diabetes mellitus and smoking as associations with RCTs within our analysis due to insufficient reporting of these factors within the current literature, patients with such factors potentially are at a higher risk of RCTs.^59

–61 Furthermore, such interference with elimination pathways can potentially prolong the healing process of these patients.

The data for gender association with RCTs was equivocal as well, with a total OR of 0.98 (CI: 0.66–1.45). This may indicate that the homeostasis of natural tissue and elimination pathways as well as the extent of apoptosis is similar in both the male and female genders.

Conclusion

In conclusion, our meta-analysis revealed that both hand dominance and older age are associated with RCTs. Although we revealed that a higher BMI, a history of hypertension and history of smoking are associated with RCTs within our systematic review, these associations cannot be generalized to the entire international population as it strong data was only presented in one study. Future studies should focus more on strengthening the literature for the association between RCTs and factors such as diabetes mellitus, hypertension, smoking and BMI. Studies should also explore other novel risk factors as well as basic sciences explaining the underlying basis for the association between each factor and RCTs. It is hoped that with such information, treatment options can be improved, thus influencing management protocols and patient outcomes.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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Systematic review on risk factors of rotator cuff tears

Abstract

Purpose:

Methods:

Results:

Conclusions:

Keywords

Introduction

Methods

Results

Discussion

Conclusion

Footnotes

Declaration of conflicting interests

Funding

References