Association between dyslipidemia and rotator cuff tear – A study

Introduction and Aim: Rotator cuff diseases are the most common soft tissue injuries in the upper extremity with incidence ranging from 5% to 39%. The causes of rotator cuff tendon ruptures are multifactorial. Both extrinsic and intrinsic factors affect the degeneration of rotator cuff muscles. Few animal studies have shown detrimental effects on tendons in the presence of high lipid levels. The goal of the current investigation was to determine whether abnormal blood lipid levels and rotator cuff tears are related. Materials and Methods: This cross-sectional study was carried out in a hospital setting at the AJ Institute of Medical Sciences and Research Centre in Mangalore over a 24-month period . The sample size obtained was 93 with the convenience sampling technique. The research involved clinical examination and routine blood investigations, fasting lipid profile and radiological examination. Following all the data collection, an association was assessed between fasting lipid values and rotator cuff tear using statistical analysis. Results: Sixty-eight patients had an increased serum cholesterol level, which was shown to have a significant association with rotator cuff tear (chi square = 12.102 and p = 0.007). 52 patients suffering from rotator cuff tear had a low level of HDL, which was shown to have a statistically significant association (chi square = 13.098 and p = 0.042). 55 patients with rotator cuff tears had high LDL levels, which were shown to have a statistically significant association, (chi square = 9.487 and p = 0.023). 75 patients with rotator cuff tears had high triglyceride levels, which were shown to have a statistically significant association chi square = 8.044 and p = 0.044. Conclusion: Our research revealed a statistically significant correlation between rotator cuff injuries and elevated serum cholesterol, triglycerides, LDL levels, and low HDL levels.


INTRODUCTION
he most frequent soft tissue injuries in the upper extremities are rotator cuff illnesses.Within the general population, the incidence varies from 5% to 39% (1).The prevalence of rotator cuff tears in those over 50 years is about 23 percent (2,3).The supraspinatus tendon is the most often injured of the rotator cuff tendons in the shoulder.Avulsion of the cuff tendon from its insertion is the most common cause of full-thickness tears, necessitating tendon-tobone repair (4).
Investigations were conducted to support the risk variables for cuff pathology; few of these investigations revealed elevated serum cholesterol in patients with tears in their tendon Achilles.According to a recent study, rotator cuff injuries may be linked to elevated levels of LDL cholesterol, triglycerides, total cholesterol, and low levels of HDL cholesterol (5).Subsequent animal studies indicated that a raised level of lipids would lead to detrimental biochemical properties of tendons and adversely affect rotator cuff tendon healing (6).However, the study conducted by Longo et al., found no association between elevated total cholesterol, triglycerides, and rotator cuff injury (7).The literature is inconclusive about the association between dyslipidemia and rotator cuff injury.Hence, this study sought to determine whether abnormal serum lipid levels and rotator cuff tears are related.

MATERIALS AND METHODS
This cross-sectional study was done in the Orthopedics Department at the A. J. Institute of Medical Sciences and Research Centre, Mangalore, for a period of 24 months.The study comprised ninety-three individuals older than twenty-one years who were diagnosed with rotator cuff injuries based on both clinical examination and shoulder ultrasonography.Individuals having a history of shoulder infections, smokers, frozen shoulder, calcific tendonitis, chronic steroid usage, and cardiovascular disease were not allowed to participate in the study.
The research involved clinical examination and routine blood investigations, fasting lipid profiles, radiological examination in the form of x-rays and USG.Following all the data collection, an association was assessed between fasting lipid values and rotator cuff tear using statistical analysis.Baseline data was represented by simple tables and diagrams.To investigate the potential correlation between dyslipidemia and rotator cuff tears, the chi-square test was used.

Statistical analysis
With SPSS 20.0, a statistical analysis of the data was carried out.Frequency and percentage were used to T represent the category variables.The mean ± SD was used to present the continuous variables.The chi square test was used to determine the relationship between radiological results and triglycerides, HDL, LDL, and cholesterol.P-values less than 0.05 were deemed statistically significant.

RESULTS
The study consisted of 93 patients with an average age of 50.02 ± 10.50 years, including people from thirty to eighty years old.A high concentration of 54 (58.1%) of the patients were in the age group of 45 to 59 years, followed by 23 (24.7%) from 30 to 44 years and 16 (17.2%)were 60 years and older.The study consisted of 93 patients, among them the majority of whom the majority 55 (59.1%) were male and 38 (40.9%) were female.Among 38 female patients, a majority of 50% was in the age range of 45 to 59 years and among 55 male patients, a majority of 63.6% was in the age range of 45 to 59 years.1).
The analysis shows a significant association between radiological findings and low HDL levels, with chi square = 13.098 and p = 0.042 (p<0.05).The table depicts 52 patients with HDL levels below the normal level.Among them, 44.2% had supraspinatus muscle tears, 30.8% had supraspinatus and infraspinatus muscle tears, 17.3% had supraspinatus and subscapularis muscle tears and 7.7% had supraspinatus, infraspinatus, and subscapularis muscle tears (Table 6).The analysis shows a significant association between radiological findings and high triglyceride levels, with chi square = 8.044 and p = 0.044 (p<0.05).The table depicts 75 patients with triglycerides >=150 mg/dl.Among them, 38.7% had supraspinatus muscle tears, 32% had supraspinatus and infraspinatus muscle tears, 17.3% had supraspinatus and subscapularis muscle tears and 12% had supraspinatus, infraspinatus, and subscapularis muscle tears (Table 8).

DISCUSSION
Although the exact causes of rotator cuff injuries are unknown, there are several.Few studies have been done in regard to rotator cuff tears, but many have been done to determine the association between high serum lipid levels and tendon ruptures (5).Many studies have been conducted to establish the relationship between rotator cuff tendon pathology and hyperlipidemia, of which few studies have shown hyperlipidemic conditions that lead to degenerative changes, causing the rotator cuff tear.Contrarily, few other studies have shown no statistical significance between hyperlipidemic and rotator cuff to tear.Many research articles have mentioned the manifestations of systemic hyperlipidemia effects on other major tendons like tendon Achilles.A few animal model studies were also conducted to establish the relationship.Another study conducted by Beason et al., on rats suggested, higher cholesterol levels in rats showed detrimental effects on healing properties of tendon (6).
A few other studies have suggested there is no positive association between rotator cuff tear and hyperlipidemia status, which leads to conflicts.In a study conducted by Longo et al., (7) he noted that, comparing patients with rotator cuff tears to those receiving arthroscopic meniscectomy and without a history of rotator cuff injury, there was no statistically significant change in the blood triglyceride and total cholesterol values.
One of the studies, by Klemp et al., (8) suggested an association between hyperlipidemia and tendon xanthomas, tendo Achilles tendinitis, and oligoarthritis.It also demonstrated that in 62% of patients, musculoskeletal system symptoms preceded the diagnosis of hyperlipidemia, and that in 63% of patients, symptoms got better after starting treatment for hyperlipidemia.He also stated that there is some evidence, though it is not conclusive, that elevated triglyceride levels may also raise the risk of musculoskeletal system symptoms.
In a study conducted by Mathiak et al., (9) it was mentioned that high lipid levels may predispose individuals to Achilles tendon ruptures.He also compared his study to other studies done by Murano et al., (10) and Zehntner et al., (11)  correlations between the thickness of the Achilles tendon, ruptures, and total cholesterol levels in patients with familial hypercholesterolemia.He found that in his patients 83% of them had high cholesterol levels, only 19% of them were aware of high cholesterol levels.In his study, even though he did not notice partial ruptures or xanthomas, he noted degenerative changes.He also mentioned that ultrasound may be helpful in investigations but is not suitable for screening for the risk of Achilles tendon ruptures.
Hypercholesterolemia is thought to enhance the risk of tendon injury through a variety of mechanisms.
Previous investigations have demonstrated site-to-site differences in the age-related accumulation of cholesterol in tissue.Age-related changes in muscle cholesterol deposition are minor, but they are greater in adipose tissue, skin, and the dense connective tissues of the elderly.(i.e., tendons like the biceps and psoas tendon).As a result, normal connective tissue is especially vulnerable to localized cholesterol deposition in the elderly.This strengthens the previously mentioned intrinsic mechanism of tendon failure.The production of tendon xanthoma, which may alter mechanical properties and obviously raise Achilles tendon rupture rates, has been linked to the deposition of cholesterol byproducts (12,13).
In other study of 74 people, in contrast to patients with normal rotator cuff tendons, who had a total cholesterol level of 194 mg/dl, 47 patients with rotator cuff tears had a higher serum cholesterol level of more than 240 mg/dl, according to a study by Abboud and Kim (5).Triglyceride and LDL-C concentrations were higher in the individuals with rotator cuff tendon injuries (p=0.02 and p=0.03, respectively), although HDL-C levels were declining (p=0.1).Patients with two rotator cuff tendon injuries also had higher cholesterol levels, according to their findings.
In another study done by Kim et al.,(14) 37 of the 49 (75.5%)patients with hyperlipidemia and 29 (58%) individuals with non-hyperlipidemia both exhibited supraspinatus tears on ultrasonography.Although statistical analysis did not reveal a difference that was statistically significant (p = 0.06), we discovered that rotator cuff tears were more common in the hyperlipidemia group.They also found improvement in pain from supraspinatus tendinopathy in the hyperlipidemia group was less when compared to patients without hyperlipidemia.
In another study by Sunil et al., out of 50 patients, 21 had high cholesterol compared to 18 out of 50 people in the control group with no rotator cuff tear (15).High cholesterol levels in rotator cuff tears were not statistically significant (p = 0.539).Triglycerides were high in 26% of people who showed rotator cuff tears and in 24% of the control group, which showed no statistically significant association between rotator cuff and high triglycerides.In the same study, 36% of people had low HDL compared to 32% in the control group, which showed no statistical significance (p = 0.663).When comparing the LDL levels, 32% of people in the tear group had high LDL levels when compared to 28% in the control group, which showed no statistical significance.Even though high cholesterol levels were statistically significant in rotator cuff tear patients, total cholesterol, triglycerides, and LDL were high.
In the current study, out of 93 patients, the mean age was 50.02 ± 10.50 years.Most of the patients were concentrated in the age group of 45 to 59 years.Most of the patients were male (59.1%).The majority were right hand dominant patients.64.5% of the people were not known to have a history about the origin of the symptoms, whereas 20.4% gave a history of trauma, and 15.1% of them gave a history of injury during sports.Most of the patients aged 30-44 years and 45-60 years had supraspinatus and infraspinatus muscle tears.
Out of 93 patients, 68 had higher total cholesterol levels, which were above 200 mg/dl.Of those, 26 patients had supraspinatus tears.Out of 13 people who had both supraspinatus, infraspinatus, and subscapularis tears, 12 had higher serum cholesterol levels.There was a significant association between raised serum cholesterol levels and rotator cuff tears (P<0.007).In relation to HDL, 52 out of 93 patients had below normal levels, and the majority had supraspinatus tears.Low HDL levels were shown to have a statistically significant association with rotator cuff tear with chi square = 13.098 and p = 0.042 (p < 0.05).A total of 55 out of 93 patients had higher LDL levels, of which there was a significant association between radiological findings and higher LDL levels with chi square = 9.487 and p = 0.023 (p < 0.05).
Also in this study, we found a significant association between radiological findings and triglyceride level with chi square = 8.044 and p = 0.044 (p < 0.05), 75 patients had a higher triglyceride level out of 93 people.

Limitations
Our study has various limitations, including the following: 1.We lacked histology correlation for diagnosis confirmation; histology investigations could have prevented this. 2. We examined patients who visited our hospital; most of them were residents of our neighborhood.This selection bias can be reduced by conducting extensive multicentric trials across India.3. The patients that visited us might not be an accurate representation of the entire population (habits, gender).4. Other factors that might have caused the tear, such as the involvement of exercise, dietary habits, and concomitant sickness, were not examined.However, these factors can be ruled out by correlating associations and having many variables.

CONCLUSION
In the present study, a significant association was observed between dyslipidemia and rotator cuff tear.Increased levels of serum total cholesterol, triglycerides and LDL were observed to have a statistically significant association with patients having rotator cuff tears.Also, patients with low HDL levels were shown to have increased chances of having a rotator cuff tear.

Table 2 :
Cross tabulation of age and muscles involved in rotator cuff tear

Table 3 :
Cross tabulation of age and cholesterol level

Table 3
In the 40 to 59 years old age group, 43 (79.6%) had a cholesterol level >=200 mg/dl and in the 60 years and above age group, 10 (62.5%) had a cholesterol level >=200 mg/dl.Most of the patients in both sexes had a cholesterol level >= 200 mg/dl (female: 65.8%, male: 78.2%).In all the age categories, the majority had HDL below the normal level.In the 30 to 44, 45 to 59 and 60 years and depicts that in the present study, 15 (65.2%) had a cholesterol level >=200 mg/dl in the age group of 30 to 44 years.

Table 4 :
Cross tabulation of triglycerides with age

Table 5 :
Association between radiological findings and cholesterol level

Table 6 :
Association between radiological findings and HDL

Table 7 :
Association between radiological findings and LDL

Table 8 :
Association between radiological findings and triglycerides who found