Glenohumeral and scapulothoracic strength impairments exists in patients with subacromial impingement, but these are not reflected in the shoulder pain and disability index

Abstract

BackgroundPain and loss of function are cardinal symptoms associated with Subacromial impingement syndrome (SIS), while the presence and magnitude of deficits in strength and range of motion (ROM) are largely undescribed in non-athletic patients with SIS. Moreover, the relevance of impairments in strength and ROM to patient-reported shoulder function is not well described, even though testing of strength is recommended in clinical guidelines.The purpose of this study was, first, to investigate impairments in glenohumeral and scapulothoracic strength and in abduction and internal rotation ROM in patients with SIS. Secondly, to investigate the influence of these impairments on patient-reported shoulder function.MethodsCross-sectional study based on a consecutive cohort of 157 patients referred to specialist examination and diagnosed with shoulder impingement (SIS) using predefined validated diagnostic criteria. Prior to specialist examination, questionnaires regarding shoulder function (Shoulder Pain And Disability Index, SPADI) demographics and kinesiophobia (TSK-11) were collected, and shoulder strength and ROM was measured by trained testers, with the patient reporting pain levels during testing and for the last week. Impairments in strength (abduction, external-rotation, (protraction and horizontal-extension) and ROM (abduction and internal rotation) were investigated in patients with unilateral shoulder pain, using one-sample t-tests. SPADI total score (SPADI) and SPADI function score (SPADI-F), were chosen as dependent variables in multiple regressions to investigate the influence of impairments on patient-reported shoulder function. Independent variables of interest were; strength in abduction and external rotation, abduction ROM, pain-during-tests, pain-last-week and kinesiophobia.ResultsSignificant impairments were found for all impairment tests, but most pronounced for glenohumeral strength and abduction ROM (29–33% deficits), and less for scapulothoracic strength and internal rotation ROM (8–18% deficits). Pain variables influenced SPADI and SPADI-F score to a high degree (R2 = 23.4–31.6%, p < 0.001), while strength and ROM did not.ConclusionSubstantial strength and ROM impairments were found in patients with SIS. Only pain significantly influenced patient-reported function, while impairments did not. As SPADI score does not reflect the substantial strength and ROM impairments in external rotation and abduction observed in patients with SIS, supplemental assessment of these impairments seems important.Electronic supplementary materialThe online version of this article (doi:10.1186/s12891-017-1667-1) contains supplementary material, which is available to authorized users.

The Strengthening Exercises in Shoulder Impingement trial (The SExSI-trial) investigating the effectiveness of a simple add-on shoulder strengthening exercise programme in patients with long-lasting subacromial impingement syndrome: Study protocol for a pragmatic, assessor blinded, parallel-group, randomised, controlled trial

“…Resistance training, aimed at strengthening the rotator cuff muscles and scapula stabilising muscles, is an important component of most novel exercise interventions for long-lasting SIS [ 9 , 12 , 13 ]. This seems relevant as patients with SIS have significant force impairments in both the glenohumeral and the scapulothoracic joint [ 4 , 14 , 15 ]. However, these force impairments are most pronounced in the glenohumeral joint, with a 33% deficit in external rotation force and a 29% deficit in abduction force compared to only 8% and 18% force deficit in protraction and retraction of the scapula, respectively [ 15 ].…”

“…This seems relevant as patients with SIS have significant force impairments in both the glenohumeral and the scapulothoracic joint [ 4 , 14 , 15 ]. However, these force impairments are most pronounced in the glenohumeral joint, with a 33% deficit in external rotation force and a 29% deficit in abduction force compared to only 8% and 18% force deficit in protraction and retraction of the scapula, respectively [ 15 ]. This suggests that specific training of the glenohumeral muscles is especially relevant.…”

“…Accordingly, changes in muscle force are only tested in a few randomised controlled trials (RCTs), including resistance training in the rehabilitation of patients with SIS [ 12 , 13 , 18 , 19 ]. In these studies, maximum force in external rotation increased by only 4–15% in average from baseline to follow-up in patients doing strengthening exercises [ 12 , 13 , 18 , 19 ], which is far from restoring the 33% impairment in external rotation force previously reported [ 15 ]. Though strength gain may not be the primary aim of the intervention, the sparse effect on this objective outcome points towards a possible gap in the rehabilitation of patients with long-lasting SIS.…”

Conservative treatment for patients with subacromial impingement: Changes in clinical core outcomes and their relation to specific rehabilitation parameters

“…The condition is characterized by shoulder pain and impaired patient-reported function ( Roach et al, 1991 ), but reduced strength and range of motion (ROM) has also been reported in patients with SIS ( Clausen et al, 2017 ; MacDermid et al, 2004 ). More specifically, abduction and external rotation strength, as well as abduction ROM, is only two-thirds of that in the unaffected shoulder ( Clausen et al, 2017 ) or healthy controls ( MacDermid et al, 2004 ), which is why a ∼50% increase is needed to reach normal strength and ROM levels. Based on this, it is suggested that patient-reported function, pain, strength and ROM should be considered core outcomes related to SIS ( Clausen et al, 2017 ).…”

“…More specifically, abduction and external rotation strength, as well as abduction ROM, is only two-thirds of that in the unaffected shoulder ( Clausen et al, 2017 ) or healthy controls ( MacDermid et al, 2004 ), which is why a ∼50% increase is needed to reach normal strength and ROM levels. Based on this, it is suggested that patient-reported function, pain, strength and ROM should be considered core outcomes related to SIS ( Clausen et al, 2017 ).…”