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Triglycerides and total serum cholesterol in rotator cuff tears: do they matter?
  1. U G Longo1,
  2. F Franceschi1,
  3. F Spiezia1,
  4. F Forriol2,
  5. N Maffulli3,
  6. V Denaro1
  1. 1Department of Orthopaedic and Trauma Surgery, University Campus Bio-Medico of Rome, Rome, Italy
  2. 2Research Unit FREMAP Hospital, Madrid, Spain
  3. 3Centre for Sports and Exercise Medicine, Barts and The London School of Medicine and Dentistry, Mile End Hospital, London, UK
  1. Correspondence to Prof Nicola Maffulli, Centre Lead and Professor of Sports and Exercise Medicine, Consultant Trauma and Orthopaedic Surgeon, Centre for Sports and Exercise Medicine, Barts and The London School of Medicine and Dentistry, Mile End Hospital, 275 Bancroft Rd, London E1 4DG, UK; n.maffulli{at}qmul.ac.uk

Footnotes

  • Competing interests None.

  • Ethics approval All procedures described in this study were approved by the Ethics Committee of our institution.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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Rotator cuff pathology is a very common orthopaedic problem and is a cause of great healthcare costs in industrialised countries.1 2 Despite the relevance of the problem, the aetiology and pathogenesis of rotator cuff pathology remains unclear.3,,5 Several theories of tendon injury have been proposed, and the incidence of rotator cuff tears increases with advancing age.6,,10 Trauma to the shoulder is reported by up to 60% of patients, and the incidence is particularly high in overhead athletes (30%) and labourers (23%).11 Obesity12 and increased plasma glucose levels13 have been indicated as potential risk factors for rotator cuff tears. There are data on the possible relationship between high serum lipid concentration and complete rupture of the Achilles tendon.14 15 However, to our knowledge, no studies have focused on the correlation between serum lipid levels and rotator cuff tears.

We therefore undertook a cross-sectional study of the serum triglyceride concentration and total serum cholesterol concentration in patients undergoing arthroscopic rotator cuff repair and compared them with a control group of patients of a similar age undergoing arthroscopic meniscectomy.

Material and methods

All procedures described in this study were approved by the ethics committee of our institution. All patients provided written informed consent according to the Declaration of Helsinki.

The study included 240 individuals who were operated on at our institution. One hundred and forty participants (70 in the study group and 70 in the control group) from a previous investigation13 were included in this material, along with a further 100 participants.

Group 1 included 120 patients (45 men and 75 women; mean age 64.86 years, range 40 to 83 years) (table 1) who underwent arthroscopic repair of a rotator cuff tear. The dominant arm was affected in 83 patients. The rotator cuff tears were classified as small (<1 cm) in 15 patients, medium (1 to 3 cm) in 30 patients, large (3 to 5 cm) in 43 patients, and massive (more than 5 cm) in 32 patients. The tear involved the supraspinatus tendon in 44 patients and the supraspinatus and infraspinatus tendons in 76 patients.

Table 1

Anthropometric measures

Group 2 (control group) included 120 patients (45 men and 75 women; mean age 63.91 years, range 38 to 78 years) (table 1) who underwent arthroscopic meniscectomy for a meniscal tear with no history of rotator cuff symptoms.

These patients were frequency-matched by age (within 3 years) and sex with patients of group 1.

Patients in group 1 were included in the study if they had a rotator cuff tear diagnosed on clinical and imaging grounds and a rotator cuff tear found at the time of surgery. Conservative management, including non-steroidal anti-inflammatory drugs, physiotherapy and rest, failed in all patients, and they continued to experience unacceptable pain and weakness in the affected shoulder. None of the patients had undergone previous surgery on the affected shoulder. All patients fulfilled the following criteria: (1) positive rotator cuff lag signs on preoperative examination (at least one among Jobe, Napoleon, lift-off and Patte tests)16; (2) no episodes of shoulder instability; (3) no radiographic sign of fracture of the glenoid or the tuberosities; (4) MRI evidence of cuff tear; (5) rotator cuff tear of one or more tendons at arthroscopic examination; (6) no lesion of the glenoid labrum or of the capsule at arthroscopic examination.

Patients in group 2 were included in the study if they had a meniscal tear diagnosed on clinical and imaging grounds and a meniscal tear found at the time of surgery.

Exclusion criteria for all participants were: primary osteoarthritis of the operated or contralateral joint, previous operations on the shoulder or knee, inflammatory joint disease, hypertension, diabetes or hypercholesterolemia managed with statins. Patients in group 2 were also excluded from the study if they had history of shoulder pain, or rotator cuff pathology diagnosed by imaging or on clinical grounds.

Anthropometric measurements

Height and weight measurements of every patient were taken by the same examiner before blood sampling was performed; the body mass index (BMI) was calculated on the day of sampling (table 1).

Measurement of total cholesterol and triglycerides

All blood samples were collected in an identical manner between 07:00 and 07:30 after an overnight fast that started at 12:00 midnight. Biochemical analyses of blood were performed on fresh samples. Blood samples (5 ml) were collected from each patient into tubes (Vacutainer System, Becton Dickinson, New Jersey, USA), and were centrifuged at the relative centrifugal force of 2750 for 10 min. Sera were extracted from the samples, and the concentrations of total cholesterol (TC) and triglycerides (TG) were measured by enzymatic methods with the CIBA Corning 550 Express Autoanalyzer (Boehringer Mannheim, Mannheim, Germany). Patients were considered to have established hypercholesterolaemia at levels >6.2 mmol/l, and light hypercholesterolaemia at levels between 5.2 and 6.2 mmol/l.17 Patients were considered to have established hypertriglyceridaemia at levels >4.5 mmol/l.17

Statistics

Data were entered in a commercially available database. Descriptive statistics were calculated, and analytical statistics were performed with non-paired sample t test using SPSS (version 4). Significance was set at p<0.05.

Results

The serum concentrations of triglyceride and total cholesterol were measurable in all patients. We were not able to determine any significant differences in serum concentrations of triglyceride and total cholesterol in patients with small, medium, large and massive tears. Equally, there were no significant differences in serum concentrations of triglyceride or total cholesterol in patients with a supraspinatus tendon tear or supraspinatus and infraspinatus tendon tears. Therefore, for the purposes of this study, all tears were grouped together.

When comparing the two groups, no statistically significant differences were present in neither triglyceride concentration (p = 0.6) nor total cholesterol concentration (p = 0.1) (tables 2 and 3).

Table 2

Levels of serum triglycerides

Table 3

Levels of total serum cholesterol

Group 1

In group 1 (rotator cuff tears), triglyceride concentration was >4.5 mmol/l in one patient. No patient underwent treatment for high serum triglyceride levels. In the same group, total cholesterol concentration was >6.2 mmol/l in 41 patients (34.1%). Light hypercholesterolaemia (5.2–6.2 mmol/l) was present in 42 patients (35%). No patient underwent treatment for high serum cholesterol levels.

Group 2

In group 2 (control group), triglyceride concentration was >4.5 mmol/l in one patient. No patient underwent treatment for high serum triglyceride levels. In the same group, total cholesterol concentration was >6.2 mmol/l in 33 patients (27.5%). Light hypercholesterolaemia (5.2–6.2 mmol/l) was present in 47 patients (39.2%). No patient underwent treatment for high serum cholesterol levels.

Discussion

Patients with a rotator cuff tear showed no statistically significant difference in serum triglyceride and total cholesterol concentrations when compared with individuals of the same age and sex undergoing arthroscopic meniscectomy and who had no history of rotator cuff injury. This is the first study, to our knowledge, to examine the serum triglyceride and total cholesterol concentrations in patients with rotator cuff tears. We have previously shown in a comparable population that increasing plasma glucose levels are associated with rotator cuff tears in patients in the higher range of “normal” group.13

Strengths of the present study include the systematic collection of blood samples, the use of preoperative imaging and of arthroscopy to diagnose rotator cuff and meniscal tears, and the relatively large sample size of our study group. Nevertheless, we acknowledge the cross-sectional nature of the present investigation, which cannot completely resolve issues concerning temporality or rule out other factors that may influence rotator cuff tendinopathy. Another limitation of our study was that we have no data about high-density lipoprotein (HDL), low-density lipoprotein (LDL), and very low density lipoprotein (VLDL) concentrations in our patients. More detailed analysis could reveal lipoprotein abnormalities. The association between LDL and HDL cholesterol and the development of coronary heart disease is well established,18 and the management of coronary heart disease has traditionally focused on reduction of LDL cholesterol or of the total lipid profile.19 We do not know whether such strategies might exert a beneficial effect on tendon problems as well. We are fully aware that more anthropometric measures could be performed (eg, waist and hip girth, and skin-fold measurements). Unfortunately, we did not collect these data in our patients: this could be the subject of future endeavours.

Ideally, the control group should have been constituted by healthy people. However, as this was a frequency-matched casecontrol study, if, on the one hand, it could have been relatively simple to find a healthy young person, the same would have not applied for an elderly person, especially given the stringent exclusion criteria in our study. Among the various diseases of the lower limb, we choose to enrol in the control group patients with pathology of the lower limb with a likely mechanic, not metabolic cause, different from tendon pathology. Classically, the causative mechanisms of rotator cuff pathology have been subdivided into extrinsic and intrinsic factors.20 Intrinsic factors focus on the pathologic changes lying predominantly within the tendon itself.21,,23 Extrinsic factors are variables that interact to contribute to rotator cuff damage. They can be broadly grouped into anatomical (acromial morphologic characteristics, os acromiale and acromial spurs) and environmental factors (shoulder overuse, smoking, and any medical condition that impairs the inflammatory and healing response such as diabetes mellitus).20

In a retrospective cohort study of 205 patients, Harvie et al24 showed a higher risk of symptomatic full-thickness rotator cuff tears in siblings of patients with rotator cuff tears versus controls, implying a role for genetic factors.25 There is an association between obesity and shoulder repair surgery in men and women aged 53 to 70 years, suggesting that increasing BMI is a risk factor for rotator cuff pathologies.12 Obesity could contribute to decreased vascularity through its associations with risk factors for vascular disease, such as elevated cholesterol,26 atherosclerosis,27 diabetes, hypertension, metabolic syndrome and decreased physical activity.28 A correlation between adiposity and rotator cuff tendinopathy has been proposed, but while the association with BMI and tendinopathy has been reported,12 there are no studies focused on serum levels of lipids and rotator cuff tendinopathy.

What is already known on this topic

  • ▶. Tears of the rotator cuff cause high healthcare costs in industrialised countries.

  • ▶. The mechanisms underlying the aetiopathogenesis of rotator cuff disease remains poorly understood.

  • ▶. No studies have focused on the correlation between plasma serum total cholesterol and triglyceride concentrations and rotator cuff tears.

What this study adds

  • ▶. There appears to be no association between serum triglycerides and total serum cholesterol levels and rotator cuff tears.

  • ▶. Additional research is required to improve our understanding of aetiopathogenesis of rotator cuff tears.

A major histopathological feature of tendinopathy is a failed healing response.29 Accumulation of lipids and ground substance (glycosaminoglycans) and calcium deposits represent age-related changes of the tendon.30 During ageing, lipid accumulation is extracellular: lipids with a high content of esterified cholesterol spread along the longitudinal axis of collagen fibres. Lipid deposition disrupts the fibre bundles and may, through this mechanism, decrease tendon strength.30

The association between tendon injury and adiposity has been examined.31 Elevated adiposity can be frequently associated with tendon injury,31 and it seems that elevated adiposity develops before tendon pathology, even though any definitive conclusion should be reached with caution.32 Although some evidences suggest that there is a possible association between tendinopathy of the lower limb and high cholesterol levels,14 15 we could not find similar results in our population of patients with rotator cuff tears. Moreover, while histopathological examination of specimens harvested during surgery for tendinopathy in the lower limb showed fatty degeneration or tendolipomatosis,33 we failed to show evidence of fatty degeneration in tendon samples from the rotator cuff3 and the long head of the biceps tendon.34 In addition, while there seems to be evidence of a possible role of high serum lipid concentration and complete rupture of the Achilles tendon,14 15 our data suggest no role of the serum cholesterol and triglyceride concentration in rotator cuff tears. We can speculate that, probably, the mechanisms underlying tendinopathy may be different in the lower or upper limbs, even though more studies are needed to confirm this preliminary statement.

Some authors35 proposed the use of dietary supplements, including omega 3 fatty acids and antioxidants, in the management of tendinopathies, on the basis that high levels of cytokines, (ie, pro-inflammatory interleukin 1b and vascular endothelial growth factor) have been reported in the bursa of patients with rotator cuff pathology. The potential benefits of dietary supplementation in the management of tendinopathy35 36 need further research using appropriately designed, adequately powered, randomised controlled trial studies, with both objective and patient-centred outcome measures.

On the basis of our study, we doubt that triglyceride serum levels and total serum cholesterol have a causative role in the pathogenesis of rotator cuff tears, even though we advocate more research to reach definitive conclusion. The study of the different fractions of serum cholesterol may shed further light, and is the subject of future research.

In conclusion, there appears to be no association between serum lipid level and rotator cuff tears. Additional research is required to understand the causative role, if any, of serum triglyceride and total cholesterol concentrations in rotator cuff pathology.

References

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Footnotes

  • Competing interests None.

  • Ethics approval All procedures described in this study were approved by the Ethics Committee of our institution.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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