Methodological aspects
The results in this study were collected from routine diagnostic practice in an outpatient clinic. The practice was based on a literature-based written diagnostic consensus reinforced by regular supervision, meetings on a regular basis and discussions regarding difficult cases. The diagnostic criteria listed in Table
1 are mainly based on symptoms and clinical investigations and only supported by imaging in three of our nine diagnostic categories. However, most of the patients either brought (471 (61%)) or had imaging, mostly with MRI, but also with X-rays and diagnostic ultrasound. This supplementary use of imaging might be a problem in this study, as imaging give many incidental findings not necessarily contributing to the symptoms. However, this study lacked the rigid framework of a scientific study with a systematic pre-approved registration. There was no quality assessment of potential differences between the involved consultants. Intra- and inter rater reliability measures on the performance of the clinical tests were not obtained, although training before the registration period was done. The lack of inter rater reliability testing is an important limitation of this study and might lead to variability in prevalences of the selected diagnoses.
For 17 patients, the pre-set diagnosis was not changed to a more specific diagnosis after the consultation due to lacking registration from the consultants. To include these patients the senior consultant (NGJ) corrected these diagnoses by going through these medical records after the registration period, and retrospectively set a diagnosis according to the methods used in this study.
The most common diagnoses of shoulder ailments are based on sets of criteria in the absence of tissue specific characteristics. There is no conclusive gold standard and the pain generator is not known for conditions such as subacromial pain syndrome and myalgia. This is even true in the degenerative diseases where studies have shown both full thickness rotator cuff tears[
8] and osteoarthritis[
9] in non-painful shoulders. Therefore, the diagnostic criteria sets used in the literature might differ and cause frequency differences across studies. Our choice of criteria sets was mostly based on the Southampton examination schedule[
11,
25], and additional research-based criteria were added when considered adequate (Table
1). The myalgia diagnosis is disputed and argued to be a symptom and not a specific diagnosis. In this study myalgia is a symptom diagnosis supplemented with positive findings by muscle palpation.
We report only one main diagnosis per person although some patients had more than one diagnosis. This have probably affected the results, particularly in the myalgia and AC joint osteoarthritis groups. AC joint osteoarthritis is reported as increasingly present with age in persons without shoulder pain[
9] and was most likely underestimated in older age groups in our study. Myalgia is almost always present in joint diseases as an additional extra-articular source of pain but was only accounted for when present as the main diagnosis in our cohort. Probably myalgia and AC joint osteoarthritis would have been among the most prevalent secondary and tertiary diagnoses, but due to the lack of registration of more than one main diagnosis this study can not present results on the distribution of secondary and tertiary diagnosis.
Discussion of our results compared with other reports
A search of the literature did not reveal any studies reporting the prevalence of shoulder diagnoses in secondary care. Three studies reporting shoulder diagnoses from population studies or primary care were identified. Walker-Bone
et al.[
4] (447 shoulders) recruited patients from a questionnaire study of 9696 persons in the general population and 365 shoulder diagnoses were made. Östör
et al.[
5] investigated a 1-year cohort from two general practices (131 shoulders). These two studies were from England, whereas van der Windt
et al.[
6] described a Dutch 1-year cohort (392 shoulders) recruited from 11 general practitioners.
The percentages of the six most common diagnoses in these three population studies are shown in Table
3 together with percentages from our study.
Table 3
Percentages of the most common diagnoses in four studies
Subacromial pain syndrome | 36 | 30a
| 86b
| 44c
|
Adhesive capsulitis | 11 | 55 | 15 | 21 |
Myalgia | 17 | – | 6 | – |
Full thickness rotator cuff tear | 8 | – | – | – |
Acromioclavicular osteoarthritis | 4 | 6 | 31 | 5 |
Glenohumeral osteoarthritis | 4 | – | – | – |
Walker-Bone et al. reported from a population-based study in which the participants complained of shoulder pain in the previous week when asked, but did not seek help themselves. This population probably had fewer complaints regarding both duration and pain intensity compared to the other two studies that are based on patients seeking help for their shoulder symptoms. It is surprising that Walker-Bone et al. found adhesive capsulitis in 55% of the cases because this is a disease regarded to cause a lot of pain and restriction in function. In contrast the other two studies found 15% and 21% of this diagnosis.
The subacromial pain syndrome diagnosis was separated into subdiagnoses in the other studies as impingement and rotator cuff tendinopathy[
5], rotator cuff tendinitis and subacromial bursitis[
4] or as tendonitis and chronic bursitis[
6], giving the opportunity of multiple diagnoses in the same person. This might have affected the reported numbers of patients with subacromial pain syndrome. Separation of specific diagnoses in the subacromial area is disputed, both on the grounds of clinical tests and of radiological investigations[
26,
27]. Therefore, in our study, we chose to collect all patients with subacromial pain and no other specific tissue diagnosis as listed above into one group called subacromial pain syndrome. Östör
et al. reported subacromial pain in 86% of their subjects, double the rate of the other studies. Their criteria included discomfort with isometric testing of any of the rotator cuff muscles. Isometric testing gives a co contraction of all cuff muscles and this will increase the compressive forces in the GH joint, engage the trapezius and scapular muscles and may trigger pain from capsulitis in the GH joint or from painful muscles[
14]. Isometric tests with the arm elevated produce shear forces in the AC joint[
28]. Pain during isometric testing might have led to overdiagnosing subacromial pain.
Surprisingly, none of the other studies reported full thickness rotator cuff tears or glenohumeral osteoarthritis. In our study, 14% of all diagnoses in the 60–69 age group were tears, rising to 30% in persons over 70 years of age. Glenohumeral osteoarthritis was the most frequent diagnosis in women aged over 70 years (41%) and accounted for 17% of the diagnoses in men of this age group. This large difference in results between the four studies might occur because these degenerative diagnoses are rare in primary care. On the other hand, one would expect scattered cases in a 1-year cohort with ages up to 87 years. In our cohort, all diagnoses of glenohumeral osteoarthritis and full thickness rotator cuff tears were supported by MRI scans, which have very high sensitivity for these diagnoses[
29]. This might account for a higher proportion of these diagnoses in our group. On the other hand full thickness cuff tears is frequently found also in non-painful shoulders in the elderly[
30] and may have led to overdiagnosing these conditions in our population. However, there were only 28 patients with osteoarthritis and full thickness tears in our cohort of 766. The other cohorts in the literature were smaller than ours and a random distribution of diagnoses may also explain some of the variation in the results.
In the present study, AC joint osteoarthritis had to fulfil the clinical criteria in Table
1 and to be the main diagnosis to be registered. In clinical practice, symptomatic AC-joint osteoarthritis often coexists with, or is a part of, a subacromial pain syndrome. Therefore, the number of AC-joint osteoarthritis diagnoses in our study might have been underestimated because subacromial pain was chosen most often as the main diagnosis. Östör
et al. found a high percentage of AC joint osteoarthritis compared with the other studies. This might be because their diagnostic criteria included either tenderness in the AC joint region or pain on adduction of the arm only. Adduction is often painful in patients with subacromial pain syndrome and always in cases of adhesive capsulitis and this may have led to an overestimation of AC joint osteoarthritis in their study.
Walker-Bone et al. did not find any age or gender-related difference in diagnoses, and the other reports did not detail such differences. In our study, the most striking difference was the approximately 10% higher proportion of myalgia in women aged up to 60 years, a higher proportion of subacromial pain syndrome in women under 50 years of age and a higher proportion of full thickness tears after the age of 60 for both sexes.
In terms of the duration of pain, there were only one comparable study from primary care[
6]. Östör
et al. reported the median duration of pain to be 10 weeks. The participants in our cohort had suffered from shoulder pain for 26 weeks on average at the consultation. This might imply a more chronic group in secondary care, which is also to be expected. The rather large difference in the frequencies of the diagnose myalgia might be explained by the different diagnostic criteria used in the studies but it could also partly reflect the longer duration of pain in secondary care.
The generalisability of this study is limited because of differences in the spectre of diagnoses used compared to other studies, and also the methodological limitations with the lack of inter rater reliability testing, the missing secondary and tertiary diagnoses and the pragmatic use of clinical tests and imaging as diagnostic tools.
However, our data is the first description of the shoulder diagnoses in a secondary care setting, and we found that the most frequent diagnoses were subacromial pain, myalgia and adhesive capsulitis. Our results from secondary care are partly in line with studies from primary care settings. In all these studies subacromial pain and adhesive capsulitis represented 50% or more of the cases for both men and women. Consequently, these two diagnoses should always be considered in patients presenting with shoulder pain in all levels of health care.