LATERAL EPICONDYLITIS AND TOBACCO USE: A CASE-CONTROL STUDY Avery E. Michienzi, BS1,2, Christopher P. Anderson, MPH3, Sandy Vang, BA1,2, Christina M. Ward, MD1,2
ABSTRACT Background: Although lateral epicondylitis (LE) is a ver y common tendinopathy, we understand little about the etiology of the disease. Tobacco use has been associated with other tendinopathies, and the purpose of this study is to determine if there is an association between the incidence of lateral epicondylitis and tobacco use. Methods: We performed a retrospective cohort study of adult patients diagnosed with lateral epicondylitis. Patients from a single orthopaedic surgeon’s practice with LE were matched to control patients with other common upper extremity conditions based on age, gender, and occupation. A total of 65 case patients and 217 control patients were included in the study. The incidence of smoking in patients with lateral epicondylitis was compared to the incidence of smoking in the control group. Results: Of the LE patients, 30/65 (46.2%) were non-smokers, 23/65 (35.4%) were former smokers, and 12/65 (18.5%) were current smokers. Of the control patients, 121/217 (55.8%) were nonsmokers, 45/217 (20.7%) were former smokers, and 51/217 (23.5%) were current smokers. The odds of LE patients being former or current smokers compared to control patients were 1.45 times higher, but this was not statistically significant. Among people who did not smoke at the time of presentation, the odds of being a former smoker were 2.28 times higher in LE patients than in controls, which was statistically significant. Conclusions: The odds of being a former smoker were significantly higher in patients with lateral epicondylitis compared to patients with other upDepartment of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN 2 Department of Orthopaedics, Regions Hospital, St. Paul, MN 3 HealthPartners Institute for Research and Education, Bloomington, MN Corresponding Author: Christina M. Ward, MD Regions Hospital 640 Jackson St Mail Stop 11503L St. Paul, MN 55101 Phone: (651) 254-1513 [email protected] 1
114 The Iowa Orthopaedic Journal
per extremity conditions. Although it did not reach statistical significance, the odds of being former or current smokers were also higher in the LE group. These results suggest a relationship between smoking histor y and incidence of lateral epicondylitis, though more research is needed to determine the exact nature of the relationship. Level of Evidence: Prognostic, Level III INTRODUCTION Lateral epicondylitis (LE), or “tennis elbow,” is a common cause of elbow pain, effecting nearly 1% of working-age adults1,2. Despite the prevalence of lateral epicondylitis, the etiology of the disease is not well understood. Several studies have evaluated the relationship between LE and patient factors such as occupational activities, sex, and age1,2,3. These studies have shown a link between manual labor and LE as well as a higher incidence of LE in patients ages 45-541,2,4,5. Biopsies of tendon tissue in patients undergoing surgery for lateral epicondylitis reveal a pattern of poorly organized collagen and invasion with abnormal vascular structures known as tendinosis6. These changes are similar in appearance to tendon changes in other tendinopathies such as rotator cuff tears7,8. Though there is not a wealth of data on the relationship between smoking status and LE, a link between tobacco use and rotator cuff tears has been shown in several recent studies. Kane et al. found an increased incidence and increased severity of rotator cuff tears in cadavers with a history of smoking9. Likewise, Baumgarten et al. found an increased incidence of rotator cuff tears was associated with any history of smoking, a history of smoking within 10 years of onset of shoulder pain, and increased packyears of tobacco use10. Because of the similarity in microscopic pathology between rotator cuff tears and LE, we questioned whether tobacco use was related to LE. We identified two published studies addressing this question. The first study, a cross-sectional study from Finland, found that patients with LE were more likely to be regular tobacco users (odds ratio [OR] 3.4)1. The second study, a casecontrol study from England that utilized diagnostic and demographic information from a database, found that previous smoking history was a risk factor for lateral
Lateral Epicondylitis and Tobacco Use: A Case-Control Study Table 2: Classification of Occupations
Table 1: ICD9 Diagnosis Codes ICD9 Code
Description
Cohort
726.32
Lateral epicondylitis
Case
726.32A
Lateral epicondylitis
Case
354.2
Ulnar nerve lesion
Control
816.01
Fx middle/proximal phalanx- hand-CL
Control
727.05
Tenosynovitis hand/wrist NEC
Control
815.00
Fx metacarpal NOS-CLOSED
Control
727.43
Ganglion NOS
Control
727.04
Radial styloid tenosynovitis
Control
715.34
LOC osteoarthritis NOS-HAND
Control
727.03
Trigger finger
Control
813.42
Fx distal radius NEC-CL
Control
354.0
Carpal tunnel syndrome
Control
epicondylitis (OR 1.20) but that current smoking status was not11. However, this study was limited in that there were no specific diagnostic criteria for LE. Understanding the relationship between tobacco use and LE could have an important impact on treatment. Mallon et al. found that smokers had worse outcomes than nonsmokers following open rotator cuff repairs12. If tobacco use is related to tendinosis, evaluating the efficacy of various treatments in smokers vs. non-smokers could yield important direction for treatment of patients with LE. The goal of this study was to evaluate the relationship between tobacco use and incidence of lateral epicondylitis. We hypothesized that patients with lateral epicondylitis are more likely to regularly use tobacco than the general population. In this study, we compared the smoking rates in a group of LE patients to the smoking rates in a control group of patients with other upper extremity conditions. We also compared the smoking rates of the LE patients and control patients to the state average of the study population. PATIENTS AND METHODS Subject Selection: This was a retrospective case control study approved by the site’s institutional review board. We reviewed patients who presented to a single orthopaedic surgeon specializing in upper extremity conditions between 2009 and 2012. Patients were identified by query of billing codes (ICD9 codes) through hospital databases. Data was collected from the electronic medical record. Eligible subjects for study were 18 years or older at the time of presentation, and had either a diagnosis of LE by ICD-9 code (case patients), or one of the ten common upper extremity injuries listed in Table 1 (con-
Occupation Class
Type of work
Light
Health care worker, lab worker, office worker, stay at home mom, teacher, student, retired*, unemployed*
Medium
Law enforcement, food service, army, truck driver, mail handler, physical/message therapy
Heavy
Construction, labor, maintenance, mechanic, factory/assembly line worker
*Due to variability in the documentation of jobs in the electronic medical records, past work history was not factored into the classification of retired or unemployed patients.
trol patients). Patients were excluded if their records contained incomplete smoking status or occupation information, or if the cause of LE was determined by the principal investigator to be due to high energy trauma. All patients were examined by a single orthopaedic surgeon. The diagnosis of LE was made based on the presence of tenderness over the lateral epicondyle and pain with resisted wrist extension with the elbow in extension. Because the pool of potential controls was large, a subset was selected using the random number generator (RAND) function in Excel (Microsoft Corporation, Redmond, WA, USA). Case-control match: Occupations were organized into three classes (light, moderate, and heavy) based on the perceived frequency that workers would engage in high risk activities identified by Van Rijn et al., Walker-Bone et al., and Haahr and Anderson2,5,13. The high risk factors for lateral epicondylitis identified in the literature included forceful work, repetitive movements, working with hands or arms in a non-neutral position, working with the neck twisted, working with neck bent forwards >2h/day, handling tools > 1 kg, handling loads > 20 kg at least 10/day, use of hand/arm vibrating tools >1h/day, carrying weights on one shoulder, and lifting weights >5kg in one hand. Table 2 shows the classification of specific occupations and occupation fields according to the above criteria. A separate investigator independently assessed occupation class in a subset of 20 LE patients and 20 control patients for purposes of demonstrating inter-rater agreement. Each LE patient in the case cohort was matched with up to four controls using a greedy matching algorithm according to age, gender, and occupation class14. In order to be considered a match, a control had to be within 5 years of age from a case, and have the same occupation class and gender. Any cases or controls that remained unmatched were not included in the analysis.
Volume 35 115
A. E. Michienzi, C. P. Anderson, S. Vang, C. M. Ward Figure 1: Breakdown of total study population
Table 3: Smoking Rates in Lateral Epicondylitis Cases and Controls Smoking Status
Control Rate (%)
LE Case Rate (%)
Never
55.8 (48.9 – 62.5)
46.2 (33.7 – 59.0)
Former
20.7 (15.5 – 26.7)*
35.4 (23.9 – 48.2)
Current
23.5 (18.0 – 29.7)*
18.5 (9.9 – 30.0)
Ever Smoking
44.2 (37.5 – 51.1)
53.8 (41.0 -66.3)
*Indicates a p
ABSTRACT Background: Although lateral epicondylitis (LE) is a ver y common tendinopathy, we understand little about the etiology of the disease. Tobacco use has been associated with other tendinopathies, and the purpose of this study is to determine if there is an association between the incidence of lateral epicondylitis and tobacco use. Methods: We performed a retrospective cohort study of adult patients diagnosed with lateral epicondylitis. Patients from a single orthopaedic surgeon’s practice with LE were matched to control patients with other common upper extremity conditions based on age, gender, and occupation. A total of 65 case patients and 217 control patients were included in the study. The incidence of smoking in patients with lateral epicondylitis was compared to the incidence of smoking in the control group. Results: Of the LE patients, 30/65 (46.2%) were non-smokers, 23/65 (35.4%) were former smokers, and 12/65 (18.5%) were current smokers. Of the control patients, 121/217 (55.8%) were nonsmokers, 45/217 (20.7%) were former smokers, and 51/217 (23.5%) were current smokers. The odds of LE patients being former or current smokers compared to control patients were 1.45 times higher, but this was not statistically significant. Among people who did not smoke at the time of presentation, the odds of being a former smoker were 2.28 times higher in LE patients than in controls, which was statistically significant. Conclusions: The odds of being a former smoker were significantly higher in patients with lateral epicondylitis compared to patients with other upDepartment of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN 2 Department of Orthopaedics, Regions Hospital, St. Paul, MN 3 HealthPartners Institute for Research and Education, Bloomington, MN Corresponding Author: Christina M. Ward, MD Regions Hospital 640 Jackson St Mail Stop 11503L St. Paul, MN 55101 Phone: (651) 254-1513 [email protected] 1
114 The Iowa Orthopaedic Journal
per extremity conditions. Although it did not reach statistical significance, the odds of being former or current smokers were also higher in the LE group. These results suggest a relationship between smoking histor y and incidence of lateral epicondylitis, though more research is needed to determine the exact nature of the relationship. Level of Evidence: Prognostic, Level III INTRODUCTION Lateral epicondylitis (LE), or “tennis elbow,” is a common cause of elbow pain, effecting nearly 1% of working-age adults1,2. Despite the prevalence of lateral epicondylitis, the etiology of the disease is not well understood. Several studies have evaluated the relationship between LE and patient factors such as occupational activities, sex, and age1,2,3. These studies have shown a link between manual labor and LE as well as a higher incidence of LE in patients ages 45-541,2,4,5. Biopsies of tendon tissue in patients undergoing surgery for lateral epicondylitis reveal a pattern of poorly organized collagen and invasion with abnormal vascular structures known as tendinosis6. These changes are similar in appearance to tendon changes in other tendinopathies such as rotator cuff tears7,8. Though there is not a wealth of data on the relationship between smoking status and LE, a link between tobacco use and rotator cuff tears has been shown in several recent studies. Kane et al. found an increased incidence and increased severity of rotator cuff tears in cadavers with a history of smoking9. Likewise, Baumgarten et al. found an increased incidence of rotator cuff tears was associated with any history of smoking, a history of smoking within 10 years of onset of shoulder pain, and increased packyears of tobacco use10. Because of the similarity in microscopic pathology between rotator cuff tears and LE, we questioned whether tobacco use was related to LE. We identified two published studies addressing this question. The first study, a cross-sectional study from Finland, found that patients with LE were more likely to be regular tobacco users (odds ratio [OR] 3.4)1. The second study, a casecontrol study from England that utilized diagnostic and demographic information from a database, found that previous smoking history was a risk factor for lateral
Lateral Epicondylitis and Tobacco Use: A Case-Control Study Table 2: Classification of Occupations
Table 1: ICD9 Diagnosis Codes ICD9 Code
Description
Cohort
726.32
Lateral epicondylitis
Case
726.32A
Lateral epicondylitis
Case
354.2
Ulnar nerve lesion
Control
816.01
Fx middle/proximal phalanx- hand-CL
Control
727.05
Tenosynovitis hand/wrist NEC
Control
815.00
Fx metacarpal NOS-CLOSED
Control
727.43
Ganglion NOS
Control
727.04
Radial styloid tenosynovitis
Control
715.34
LOC osteoarthritis NOS-HAND
Control
727.03
Trigger finger
Control
813.42
Fx distal radius NEC-CL
Control
354.0
Carpal tunnel syndrome
Control
epicondylitis (OR 1.20) but that current smoking status was not11. However, this study was limited in that there were no specific diagnostic criteria for LE. Understanding the relationship between tobacco use and LE could have an important impact on treatment. Mallon et al. found that smokers had worse outcomes than nonsmokers following open rotator cuff repairs12. If tobacco use is related to tendinosis, evaluating the efficacy of various treatments in smokers vs. non-smokers could yield important direction for treatment of patients with LE. The goal of this study was to evaluate the relationship between tobacco use and incidence of lateral epicondylitis. We hypothesized that patients with lateral epicondylitis are more likely to regularly use tobacco than the general population. In this study, we compared the smoking rates in a group of LE patients to the smoking rates in a control group of patients with other upper extremity conditions. We also compared the smoking rates of the LE patients and control patients to the state average of the study population. PATIENTS AND METHODS Subject Selection: This was a retrospective case control study approved by the site’s institutional review board. We reviewed patients who presented to a single orthopaedic surgeon specializing in upper extremity conditions between 2009 and 2012. Patients were identified by query of billing codes (ICD9 codes) through hospital databases. Data was collected from the electronic medical record. Eligible subjects for study were 18 years or older at the time of presentation, and had either a diagnosis of LE by ICD-9 code (case patients), or one of the ten common upper extremity injuries listed in Table 1 (con-
Occupation Class
Type of work
Light
Health care worker, lab worker, office worker, stay at home mom, teacher, student, retired*, unemployed*
Medium
Law enforcement, food service, army, truck driver, mail handler, physical/message therapy
Heavy
Construction, labor, maintenance, mechanic, factory/assembly line worker
*Due to variability in the documentation of jobs in the electronic medical records, past work history was not factored into the classification of retired or unemployed patients.
trol patients). Patients were excluded if their records contained incomplete smoking status or occupation information, or if the cause of LE was determined by the principal investigator to be due to high energy trauma. All patients were examined by a single orthopaedic surgeon. The diagnosis of LE was made based on the presence of tenderness over the lateral epicondyle and pain with resisted wrist extension with the elbow in extension. Because the pool of potential controls was large, a subset was selected using the random number generator (RAND) function in Excel (Microsoft Corporation, Redmond, WA, USA). Case-control match: Occupations were organized into three classes (light, moderate, and heavy) based on the perceived frequency that workers would engage in high risk activities identified by Van Rijn et al., Walker-Bone et al., and Haahr and Anderson2,5,13. The high risk factors for lateral epicondylitis identified in the literature included forceful work, repetitive movements, working with hands or arms in a non-neutral position, working with the neck twisted, working with neck bent forwards >2h/day, handling tools > 1 kg, handling loads > 20 kg at least 10/day, use of hand/arm vibrating tools >1h/day, carrying weights on one shoulder, and lifting weights >5kg in one hand. Table 2 shows the classification of specific occupations and occupation fields according to the above criteria. A separate investigator independently assessed occupation class in a subset of 20 LE patients and 20 control patients for purposes of demonstrating inter-rater agreement. Each LE patient in the case cohort was matched with up to four controls using a greedy matching algorithm according to age, gender, and occupation class14. In order to be considered a match, a control had to be within 5 years of age from a case, and have the same occupation class and gender. Any cases or controls that remained unmatched were not included in the analysis.
Volume 35 115
A. E. Michienzi, C. P. Anderson, S. Vang, C. M. Ward Figure 1: Breakdown of total study population
Table 3: Smoking Rates in Lateral Epicondylitis Cases and Controls Smoking Status
Control Rate (%)
LE Case Rate (%)
Never
55.8 (48.9 – 62.5)
46.2 (33.7 – 59.0)
Former
20.7 (15.5 – 26.7)*
35.4 (23.9 – 48.2)
Current
23.5 (18.0 – 29.7)*
18.5 (9.9 – 30.0)
Ever Smoking
44.2 (37.5 – 51.1)
53.8 (41.0 -66.3)
*Indicates a p
