J Shoulder Elbow Surg (2014) 23, e300-e307
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Association between kyphosis and subacromial impingement syndrome: LOHAS study Kenichi Otoshi, MD, PhDa,*, Misa Takegami, RN, PhDb, Miho Sekiguchi, MD, PhDa, Yoshihiro Onishi, MPH, PhDc, Shin Yamazaki, PhDd, Koji Otani, MD, PhDa, Hiroaki Shishido, MD, PhDa, Shinichi Kikuchi, MD, PhDa, Shinichi Konno, MD, PhDa a
Department of Orthopaedic Surgery, Fukushima Medical University School of Medicine, Fukushima, Japan Department of Preventive Medicine and Epidemiologic Informatics, National Cerebral and Cardiovascular Center, Osaka, Japan c Institute for Health Outcomes and Process Evaluation Research (iHope International), Kyoto, Japan d Department of Healthcare Epidemiology, Graduate School of Medicine and Public Health, Kyoto University, Kyoto, Japan b
Background: Kyphosis is a cause of scapular dyskinesis, which can induce various shoulder disorders, including subacromial impingement syndrome (SIS). This study aimed to clarify the impact of kyphosis on SIS with use of cross-sectional data from the Locomotive Syndrome and Health Outcome in Aizu Cohort Study (LOHAS). Methods: The study enrolled 2144 participants who were older than 40 years and participated in health checkups in 2010. Kyphosis was assessed by the wall-occiput test (WOT) for thoracic kyphosis and the rib-pelvic distance test (RPDT) for lumbar kyphosis. The associations between kyphosis, SIS, and reduction in shoulder elevation (RSE) were investigated. Results: Age- and gender-adjusted logistic regression analysis demonstrated significant association between SIS and WOT (odds ratio, 1.65; 95% confidence interval, 1.02, 2.64; P < .05), whereas there was no significant association between SIS and RPDT. Multivariable logistic regression analysis demonstrated no significant association between SIS and both WOT and RPDT, whereas there was significant association between SIS and RSE. Conclusion: RSE plays a key role in the development of SIS, and thoracic kyphosis might influence the development of SIS indirectly by reducing shoulder elevation induced by the restriction of the thoracic spine extension and scapular dyskinesis. Level of evidence: Level III, Cross-Sectional Design, Epidemiology Study. Ó 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: Epidemiologic study; kyphosis; wall-occiput test; rib-pelvic distance test; subacromial impingement syndrome; scapular dyskinesis; LOHAS
IRB: This work was approved by the ethical committee of Fukushima Medical University School of Medicine (N0.673). *Reprint requests: Kenichi Otoshi, MD, PhD, Department of Orthopaedic Surgery, Fukushima Medical University School of Medicine, 1 Hikarigaoka, Fukushima City, Fukushima 960-1295, Japan. E-mail address:
[email protected] (K. Otoshi).
Subacromial impingement syndrome (SIS) is typically caused by compression of the rotator cuff and subacromial bursa against the anterolateral aspect of the acromion.37 Several structural and contributing factors might be associated with SIS, including the acromial shape,3 os acromiale,36
1058-2746/$ - see front matter Ó 2014 Journal of Shoulder and Elbow Surgery Board of Trustees. http://dx.doi.org/10.1016/j.jse.2014.04.010
Kyphosis and subacromial impingement syndrome
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coracoacromial ligament,45 superior aspect of the glenoid fossa,11,22 hypermobility and instability of the glenohumeral joint,31,51 glenohumeral capsular contraction,30 rotator cuff tendinitis,37 and intrinsic rotator cuff tendinosis.6,39,49 In addition, scapular dyskinesis is frequently associated with SIS.18,28,29 Scapular dyskinesis is defined as an alteration in the normal resting position of the scapula or an alteration in normal dynamic scapular motion.26 Biomechanical studies have demonstrated that scapular dyskinesis results from a combination of decreases in posterior tilt, external rotation, and upward rotation, and these alterations prevent elevation of the acromion, which places increased pressure on the rotator cuff and subacromial space when the arm is elevated.28,29 Alterations in the muscle properties around the scapula resulting from inflexibility, weakness, fatigue, or nerve injury are considered to be the most common factors for scapular dyskinesis.40 Alterations in spinal alignment, such as thoracic kyphosis and spinal scoliosis, have also been suggested as causes of scapular dyskinesis. Increased thoracic kyphosis would induce the scapula to become more protracted and downwardly rotated. Excessive scapular protraction alters the role of the scapula in shoulder function,25 and it leads to a potential compression under the acromion and subacromial tissues including the subacromial bursa and rotator cuff.14,16,42 Whereas several reports have described an association between thoracic kyphosis and shoulder disorders,17,24,27,48 no large population-based epidemiologic studies have investigated this association. The purpose of this study was to clarify the impact of kyphosis on SIS with use of cross-sectional data from our Locomotive Syndrome and Health Outcome in Aizu Cohort Study (LOHAS).
test (WOT) is a semiquantitative technique used to assess thoracic kyphosis and has also been used to detect occult thoracic vertebral fractures.15 Because the most common vertebral fracture morphology is an anterior wedge compression deformity,21 and this wedging leads to increased hyperkyphosis within the thoracic region,12,23 the WOT is a quick and easily administered method to assess structural thoracic kyphosis. A positive test result is defined as being unable to touch the wall with the occiput when standing with the back and heels against the wall and the head positioned such that an imaginary line from the lateral corner of the eye to the superior junction of the auricle is parallel to the floor.15 The ribpelvic distance test (RPDT) was used to assess lumbar kyphosis. The RPDT is used to detect occult lumbar vertebral fractures.1,15,43 For the same reason as for the thoracic spine, the RPDT is thought to be an indicator of lumbar kyphosis. A positive test result is defined as a distance 2 fingerbreadths between the inferior margin of the ribs and the superior surface of the pelvis in the midaxillary line.15
Materials and methods
Self-completed questionnaire survey
Study population
Questionnaire forms were distributed to the subjects before an annual health checkup and collected on the day of the checkup. The questionnaire items included the subject’s sex, age, occupation, shoulder disabilities, and general health-related quality of life. The current or most long-lasting former occupations were investigated and classified into the following 4 categories: manual, nonmanual, service, and others. Manual work included agriculture, transportation, and manufacturing work. Nonmanual work included office work, administration, and professional. Service work included sales and the service industry, and the population of unemployed subjects was defined as no-occupation.38 Upper extremity disabilities were assessed with the Japanese version of the shortened Disability of the Arm, Shoulder and Hand (QuickDASH) questionnaire.20 Health-related quality of life was assessed with the Medical Outcomes Study 12-Item Short Form Health Survey (SF-12).13 The subjects’ responses to the SF-12 questions were used to determine scores for the mental component summary (MCS) and the physical component summary (PCS). The scales for MCS and PCS are derived from 8 different subscales: physical functioning role (physical, bodily pain, general health, and vitality) and social functioning role (emotional and mental health).
The LOHAS study aims to evaluate the risk of cardiovascular disease, quality of life, medical costs, and mortality attributable to locomotive dysfunction. LOHAS is a cohort study whose subjects are residents in the towns of Tadami and Minamiaizu in Fukushima Prefecture, Japan.38 Locomotive syndrome is a condition characterized by a set of associated symptoms due to problems of the locomotive systems.35 Both towns involved in this study are located in valleys surrounded by mountains, and the main industry in the region is agriculture. In 2005, the population of Tadami was 5284, of which 40% were 65 years or older (elderly population), and the population of Minamiaizu was 19,870, of which 33% were 65 years or older.38 Eligibility criteria included persons older than 40 years who had participated in annual health checkups conducted in 2010. The Research Ethics Committee of our institute approved the study protocol, and written informed consent was obtained from all subjects.
Definition of spinal kyphosis Kyphosis was assessed by a clinical examination. Both thoracic kyphosis and lumbar kyphosis were evaluated. The wall-occiput
Definition of SIS and RSE The primary outcome measure was SIS, and a diagnosis was made on the basis of symptoms and clinical signs in a standardized health examination. The diagnostic criteria for SIS were shoulder pain during shoulder elevation and a positive Neer or Hawkins impingement test result. The shoulder elevation angle was also assessed. The angle was measured by a goniometer and divided into two categories, below or above 150 . Reduction in shoulder elevation (RSE) was defined as a shoulder elevation angle that was less than 150 . Experienced orthopedic surgeons assessed the kyphosis and performed the shoulder physical examinations. In addition, to achieve better accuracy, the orthopedic surgeons performed the physical examination after being trained by an orthopedic specialist.38
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Statistical analysis Participants with complete data were entered into the primary analysis. All analyses were conducted by JMP 10 (SAS Institute, Cary, NC, USA). Kyphosis was taken as the main exposure variable and SIS as the main outcome variable. The main survey items were described and compared in subjects with and without SIS. Statistical significance (2-tailed P < .05) was assessed by a c2 test for categorical variables and by a 2-sample t test for continuous variables. The relationships between kyphosis and SIS and between kyphosis and RSE were examined by age- and gender-adjusted logistic regression analysis. Multivariable logistic regression analysis for SIS, after control for other covariates, was also performed. The odds ratio (OR) and 95% confidence intervals (CI) were calculated for each outcome variable.
Figure 1
Study flow chart.
Results
The prevalence of SIS, RSE, and kyphosis
Of the 2505 participants who received the health check examination and agreed to fill out the questionnaire, 2481 received a physical examination. After exclusion of 337 participants with at least one missing exposure, outcome, and confounding variable, the remaining 2144 participants were entered into the primary analysis (Fig. 1).
The prevalence of SIS, RSE, and kyphosis is described in Table II. The overall prevalence of SIS was 4.4%, and there were no significant differences in the age and gender of subjects with or without SIS. The overall prevalence of RSE was 8.9%. The prevalence of RSE was significantly increased with age (P < .001) and higher in men than in women (10.6% vs 7.7%; P ¼ .021). The overall prevalence of a positive WOT result was 20.5%. The prevalence of a positive WOT result was significantly increased with age (P < .001) and higher in men than in women (22.8% vs 19%; P ¼ .032). The overall prevalence of a positive RPDT result was 43.4%. The prevalence of a positive RPDT result also significantly increased with age (P < .001) and was higher in women than in men (46.9% vs 38.1%; P < .001).
Characteristics of the study population according to the presence of SIS The baseline characteristics of the analysis population according to the presence or absence of SIS are described in Table I. The participants tended to be older, with 83.4% older than 60 years. There was no significant difference in the age or gender of subjects with or without SIS. However, a positive WOT result was significantly higher in subjects with SIS compared with those without (31.6% vs 20%; P ¼ .006), whereas a positive RPDT result was similar between the groups (49.5% vs 43.1%). RSE was more prevalent in subjects with SIS than in those without (34.3% vs 7.7%; P < .001). Approximately 40% of the subjects were employed, with 17.2%, 10.2%, 5.8%, and 7.1% categorized as manual workers, service workers, nonmanual workers, and noncategorized workers, respectively. There was no significant difference between subjects with or without SIS among each occupational category. The QuickDASH score in the overall subjects was 8.7 11.2. It was significantly higher in the subjects with SIS than in those without (20.2 17.1 vs 8.2 10.5; P < .001). The PCS and MCS scores of the SF-12 in the overall subjects were 45.8 11.3 and 50.7 9.0, respectively. Both scores were significantly lower in the subjects with SIS compared with the subjects without SIS (PCS: 40.1 13.1 vs 46.1 11.1, P < .001; MCS: 48.4 9.2 vs 50.8 9.0, P < .013).
Association of kyphosis with SIS and RSE Age- and gender-adjusted logistic regression analysis demonstrated that there was significant association between the WOT and SIS (OR, 1.65; 95% CI, 1.02, 2.64; P ¼ .039), whereas there was no significant association between the RPDT and SIS. There was significant association between the WOT and RSE (OR, 2.50; 95% CI, 1.80, 3.46; P < .001), and there was also significant association between the RPDT and RSE (OR, 1.63; 95% CI, 1.16, 2.27; P ¼ .004) (Table III). Multivariable logistic regression analysis, after control for other covariates including RSE, demonstrated that only RSE was significantly associated with SIS (OR, 6.31; 95% CI, 3.83, 10.30; P < .01). There was no significant association between SIS and kyphosis (Table IV).
Discussion Spinal kyphosis with osteoporotic vertebral fractures may worsen over time.32 The progression of thoracic kyphosis significantly related to spinal load and accelerated
Kyphosis and subacromial impingement syndrome Table I
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Baseline characteristics of the analysis population according to presence of SIS Total (n ¼ 2144) n
Age (years) Age group (years) 40-49 50-59 60-69 70-79 80 Gender Male Female Kyphosis WOT result Negative Positive RPDT result Negative Positive RSE result Negative Positive Occupation No occupation Nonmanual Service Manual Others Clinical score QuickDASH SF-12 PCS MCS
%
Mean (SD)
Subjects without SIS (n ¼ 2049)
Subjects with SIS (n ¼ 95)
n
n
%
Mean (SD)
67.9 (9.0)
%
67.9 (9.0)
P value
Mean (SD) 69.6 (8.6)
.073
102 244 760 909 129
4.8 11.4 35.4 42.4 6.0
99 234 735 860 121
4.8 11.4 35.9 42.0 5.9
3 10 25 49 8
3.2 10.5 26.3 51.6 8.4
.052
859 1285
40.0 60.0
828 1221
40.4 59.6
31 64
32.6 67.4
.13
1704 440
79.5 20.5
1639 410
80.0 20.0
65 30
68.4 31.6
.006
1214 930
56.6 43.4
1166 883
56.9 43.1
48 47
50.5 49.5
.22
1954 190
91.1 8.9
1892 157
92.3 7.7
62 33
65.7 34.3
