A comparison of the Oxford shoulder score and shoulder pain and disability index: factor structure in the context of a large randomized controlled trial

Factor structure of the Oxford Shoulder Score: secondary analyses of the UK FROST and PROFHER trial populations

AIMS

Frozen shoulder and proximal humeral fracture can cause pain, stiffness and loss of function. The impact of these symptoms on patients can be measured using the comprehensively validated, 12-item Oxford Shoulder Score (OSS). Evidence suggests that pain and function may have a differential impact on patients' experience of shoulder conditions, and this may be important for clinical management. We therefore explored the factor structure of the OSS within the UK FROST and PROFHER trial populations.

METHODS

We performed exploratory factor analysis (EFA), followed by confirmatory factor analysis (CFA), on baseline UK FROST data from 490 of the 503 trial participants. Data at 6 months post-randomisation were used for 228 of the 250 participants for the PROFHER trial.

RESULTS

UK FROST factor extraction results, using Velicer's Minimum Average Partial and Horn's Parallel Analysis tests, suggested a unifactorial solution, but two factors were weakly indicated by the less reliable 'Kaiser's eigenvalue > 1' and scree tests. We explored this further using EFA. Eight items (2 to 7, 9 and 10) loaded onto a 'Function' factor, three on a 'Pain' factor (1, 8 and 12) and item 11 cross-loaded. However, one- and two-factor models were rejected in CFA. Factor extraction of PROFHER data at 6 months demonstrated a single first-order factor solution, which was also subsequently rejected in CFA.

CONCLUSION

Insufficient evidence was found, within the constraints of the data available, to support the use of 'Pain' and 'Function' sub-scales of the OSS in either patient population.

The Greek version of shoulder rating questionnaire (SRQ): Translation, cultural adaptation, a reliability and validity study in patients with rotator cuff related shoulder pain

BACKGROUND

The Shoulder Rating Questionnaire (SRQ) was created in the English language to assess shoulder disorders in six areas: global function, pain, daily activities, recreational and athletic activities, and work.

PURPOSE

The study aimed to translate and culturally adapt Shoulder Rating Questionnaire (SRQ) into Greek.

METHODS

The SRQ English version was translated and adapted into the Greek language using forward translation, expert panel synthesis, and backward translation procedures. A pilot testing has been made in the target population, and the final version was created. A cross-sectional study was conducted in clinical settings with the SRQ and the Shoulder Pain and Disability Index. A total of 168 Greek adult patients with rotator cuff-related shoulder pain were recruited from physical therapy clinics. Τhe reliability of the SRQ Greek version was assessed using intraclass correlation coefficients. Internal consistency was assessed using the Cronbach alpha coefficient. Concurrent validity was measured by correlating the Shoulder Rating Questionnaire with the Shoulder Pain and Disability Index using Pearson's correlation coefficient.

RESULTS

The results showed that the SRQ Greek version has excellent internal consistency (Cronbach's α = 0.99), test-retest reliability (ICC = 0.976), and concurrent validity (r > 0.9). No ground or ceiling effects were found. The standard error of measurement and the minimum detectable change of the total score were 5.55 and 15.38.

CONCLUSIONS

The Greek Language Version of the SRQ is a reliable and valid instrument that can be used to evaluate adult patients with shoulder rotator cuff-related disorders in the acute or chronic phases and in clinical trials.

Mid-term results of Eclipse total shoulder arthroplasty

AIMS

The use and variety of stemless humeral components in anatomical total shoulder arthroplasty (TSA) have proliferated since their advent in 2004. Early outcomes are reassuring but independent mid-term results are scarce. This independent study reports a consecutive series of 143 Eclipse stemless shoulder prostheses with a minimum five-year (5 to 10) follow-up.

METHODS

Outcomes of 143 procedures undertaken for all indications in 131 patients were reviewed, with subset analysis of those for osteoarthritis (OA) (n = 99). The primary outcome was the Oxford Shoulder Score (OSS) at a minimum of five years. Secondary outcomes were ranges of motion and radiological analysis of humeral radiolucency, rotator cuff failure, and glenoid loosening.

RESULTS

Mean OSS at mean follow-up of 6.67 years (5.0 to 10.74) was 40.12 (9 to 48), with no statistically significant difference between those implanted for a non-OA indication and those for OA (p = 0.056) or time-dependent deterioration between two years and five years (p = 0.206). Ranges of motion significantly improved compared with preoperative findings and were maintained between two and five years with a mean external rotation of 38° (SD 18.1, 0 to 100) and forward elevation of 152° (SD 29.9, 90 to 180). Of those components with radiographs suitable for analysis (n = 83), 23 (28%) were found to have a least one humeral radiolucent line, which were predominantly incomplete, less than 2 mm, and in a single anatomical zone. No humeral components were loose. A radiolucent line was present around 22 (15%) of glenoid components, and 15 (10%) of components had failed. Rotator cuff failure was found in 21 (15%) components. The mean time to either glenoid or rotator cuff failure was greater than three years following implantation. Survivorship was 96.4% (95% CI 91.6 to 98.5, number at risk 128) at five years, and 94.3% (95% CI 88.2 to 97.3, number at risk 76) at seven years, both of which compare favourably with best results taken from available registries.

CONCLUSION

Functional and radiological outcomes of the Eclipse stemless TSA are excellent, with no loose humeral components at minimum five-year follow-up. The presence of radiolucent lines is of interest and requires long-term observation but does not impact on the clinical results. Of the eight revisions required, this was predominantly for glenoid and rotator cuff failure. Cite this article: Bone Joint J 2022;104-B(1):83-90.

Floor and ceiling effects in the Oxford Shoulder Score : an analysis from the National Joint Registry

AIMS

The main objective of this study was to examine whether the Oxford Shoulder Score (OSS) demonstrated floor or ceiling effects when used to measure outcomes following shoulder arthroplasty in a large national cohort. Secondary objectives were to assess its pain and function subscales, and to identify independent predictors for patients achieving a postoperative ceiling score following shoulder arthroplasty.

METHODS

Secondary database analysis of the National Joint Registry (NJR), which included 48,270 patients undergoing shoulder arthroplasty, was conducted. The primary outcome measure was the OSS. Secondary outcome measures were the OSS-Function Component Subscale and OSS-Pain Component Subscale. Floor and ceiling effects were considered to be present if > 15% of patients scored either the lowest or highest possible score. Logistic regression analysis was used to identify independent predictors for scoring the highest possible OSS score postoperatively.

RESULTS

Preoperatively, 1% of patients achieved the lowest possible OSS score (0) and 0.4% of patients achieved the highest possible score (48). Postoperatively, < 1% of patients achieved the lowest score at all timepoints, but the percentage achieving the highest score at six months was 8.3%, at three years 16.9%, and at five years 17%. Male patients, those aged between 60 and 89 years, and those undergoing an anatomical total shoulder arthroplasty (ATSA) were more likely to contribute to the ceiling effect seen in the OSS questionnaire. Pain and function subscales exhibited greater ceiling effects at three years and five years when compared with the overall OSS questionnaire. Logistic regression analysis showed that sex, procedure type, and preoperative OSS score were independent predictors for scoring the highest possible OSS at years.

CONCLUSION

Based on NJR patient-reported outcome measures data, the OSS does not exhibit a ceiling effect at six months, but does at three years and five years, in part due to outcome scores of ATSA. Preoperative OSS, age, male sex, and ATSA are independent predictors of achieving a ceiling score. Cite this article: Bone Joint J 2021;103-B(11):1717-1724.

Unexpected positive cultures after revision shoulder arthroplasty: does it affect outcome?

BACKGROUND

Several studies have confirmed a high rate of unexpected positive cultures (UPCs) after presumably aseptic revisions of shoulder arthroplasties; however, the impact on the outcome is still unclear. The purpose of this prospective study is to compare the patient-reported outcomes of standard revisions with and without the emergence of UPCs.

METHODS

During a 3-year period, we included all patients who were revised for reasons other than suspicion of infection from 2 orthopedic centers. Five biopsies were obtained from every revision, and only cultures with the same bacteria in at least 3 biopsy specimens were classified as UPCs. All patients were assessed using the Oxford Shoulder Score (OSS) and range of motion preoperatively and after at least a 2-year follow-up.

RESULTS

In this study, 124 patients were included, with a median follow-up of 29 months (range 29-32), and UPCs emerged after 27 revisions (22%), with Cutibacterium acnes accounting for 67% (18/27). At baseline, the OSS was 22 in both the culture-negative and UPC groups (P = .46). Then, at follow-up, the OSS was 37 in the culture-negative group and 35 in the UPC group (P = .91). The forward elevation increased significantly by 44° and 41°, respectively, in the 2 groups, but no statistically significant difference between the culture-negative group and the UPC group was found (P = .66). In contrast, the external rotation was unchanged after the revision, and again, no difference in the change between the culture-negative and UPC groups (P = .54) was observed. Subgroup analyses stratified by different implant designs revealed equal patterns with no statistical differences in outcome.

CONCLUSION

We did not find a difference in outcome after a presumed aseptic revision regardless of the emergence of UPCs. Similarly, we could not demonstrate that patients with UPCs presented with poorer function at baseline compared with culture-negative patients. The clinical relevance of UPCs thus requires further evaluation, especially in the case of C acnes as a potential pathogenic versus a merely colonizing microbe.

Structural validity of the Brazilian version of the Shoulder Pain and Disability Index in patients with chronic shoulder pain

BACKGROUND

The Shoulder Pain and Disability Index (SPADI) is a measuring instrument for pain and disability in patients with shoulder dysfunction. However, its structure is controversial (ie, 1 or 2 domains).

PURPOSE

To investigate the structural validity of the Brazilian version of the SPADI in patients with chronic shoulder pain.

STUDY DESIGN

Cross-sectional study.

METHODS

Brazilian Portuguese speakers of both genders aged 18 years or older with shoulder pain for at least 90 days (chronic) were included in this study. The structure of the SPADI was assessed by means of exploratory factor analysis with the implementation of parallel analysis and by confirmatory factor analysis. For the latter, the following goodness-of-fit indices were considered: root mean square error of approximation with 90% confidence interval, comparative fit index, Tucker-Lewis index, standardized root mean square residual, and chi-square/degrees of freedom.

RESULTS

A total of 103 participants were included in the study. The original version of the SPADI with 2 domains and 13 items showed high covariance between domains (0.98), suggesting one-dimensionality. After exploratory factor analysis with the implementation of parallel analysis, one-dimensionality was found in the SPADI. Comparing models with 1 and 2 domains by means of confirmatory factor analysis, both presented adequate values (chi-square/degrees of freedom < 3; comparative fit index and Tucker-Lewis index > 0.90; root mean square error of approximation and standardized root mean square residual < 0.08). However, the model with one domain is more suitable for presenting lower values of Akaike information criterion (3308.713) and Bayesian information criterion (3377.216).

CONCLUSION

The Brazilian version of the SPADI has a one-dimensional structure with 13 items ("shoulder impairment" construct), in contrast to the version with 2 domains.

Surgical treatments compared with early structured physiotherapy in secondary care for adults with primary frozen shoulder: the UK FROST three-arm RCT

BACKGROUND

Frozen shoulder causes pain and stiffness. It affects around 10% of people in their fifties and is slightly more common in women. Costly and invasive surgical interventions are used, without high-quality evidence that these are effective.

OBJECTIVES

To compare the clinical effectiveness and cost-effectiveness of three treatments in secondary care for adults with frozen shoulder; to qualitatively explore the acceptability of these treatments to patients and health-care professionals; and to update a systematic review to explore the trial findings in the context of existing evidence for the three treatments.

DESIGN

This was a pragmatic, parallel-group, multicentre, open-label, three-arm, randomised superiority trial with unequal allocation (2 : 2 : 1). An economic evaluation and a nested qualitative study were also carried out.

SETTING

The orthopaedic departments of 35 hospitals across the UK were recruited from April 2015, with final follow-up in December 2018.

PARTICIPANTS

Participants were adults (aged ≥ 18 years) with unilateral frozen shoulder, characterised by restriction of passive external rotation in the affected shoulder to < 50% of the opposite shoulder, and with plain radiographs excluding other pathology.

INTERVENTIONS

The inventions were early structured physiotherapy with a steroid injection, manipulation under anaesthesia with a steroid injection and arthroscopic capsular release followed by manipulation. Both of the surgical interventions were followed with post-procedural physiotherapy.

MAIN OUTCOME MEASURES

The primary outcome and end point was the Oxford Shoulder Score at 12 months post randomisation. A difference of 5 points between early structured physiotherapy and manipulation under anaesthesia or arthroscopic capsular release or of 4 points between manipulation under anaesthesia and arthroscopic capsular release was judged clinically important.

RESULTS

The mean age of the 503 participants was 54 years; 319 were female (63%) and 150 had diabetes (30%). The primary analyses comprised 473 participants (94%). At the primary end point of 12 months, participants randomised to arthroscopic capsular release had, on average, a statistically significantly higher (better) Oxford Shoulder Score than those randomised to manipulation under anaesthesia (2.01 points, 95% confidence interval 0.10 to 3.91 points; p = 0.04) or early structured physiotherapy (3.06 points, 95% confidence interval 0.71 to 5.41 points; p = 0.01). Manipulation under anaesthesia did not result in statistically significantly better Oxford Shoulder Score than early structured physiotherapy (1.05 points, 95% confidence interval -1.28 to 3.39 points; p = 0.38). No differences were deemed of clinical importance. Serious adverse events were rare but occurred in participants randomised to surgery (arthroscopic capsular release,n = 8; manipulation under anaesthesia,n = 2). There was, however, one serious adverse event in a participant who received non-trial physiotherapy. The base-case economic analysis showed that manipulation under anaesthesia was more expensive than early structured physiotherapy, with slightly better utilities. The incremental cost-effectiveness ratio for manipulation under anaesthesia was £6984 per additional quality-adjusted life-year, and this intervention was probably 86% cost-effective at the threshold of £20,000 per quality-adjusted life-year. Arthroscopic capsular release was more costly than early structured physiotherapy and manipulation under anaesthesia, with no statistically significant benefit in utilities. Participants in the qualitative study wanted early medical help and a quicker pathway to resolve their shoulder problem. Nine studies were identified from the updated systematic review, including UK FROST, of which only two could be pooled, and found that arthroscopic capsular release was more effective than physiotherapy in the long-term shoulder functioning of patients, but not to the clinically important magnitude used in UK FROST.

LIMITATIONS

Implementing physiotherapy to the trial standard in clinical practice might prove challenging but could avoid theatre use and post-procedural physiotherapy. There are potential confounding effects of waiting times in the trial.

CONCLUSIONS

None of the three interventions was clearly superior. Early structured physiotherapy with a steroid injection is an accessible and low-cost option. Manipulation under anaesthesia is the most cost-effective option. Arthroscopic capsular release carries higher risks and higher costs.

FUTURE WORK

Evaluation in a randomised controlled trial is recommended to address the increasing popularity of hydrodilatation despite the paucity of high-quality evidence.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN48804508.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 71. See the NIHR Journals Library website for further project information.

Measurement properties of translated versions of the Shoulder Pain and Disability Index: A systematic review

PURPOSE

To summarise measurement properties of translated versions of the Shoulder Pain and Disability Index (SPADI) and to assess their methodological quality.

METHODS

Relevant studies testing measurement properties of translated versions of the SPADI in non-specific shoulder pain participants were included from 11 databases (August 2020). Two reviewers independently screened articles and assessed individual measurement property risk of bias using the COSMIN checklist as very good, adequate, doubtful or inadequate. For each measurement property results were pooled and rated sufficient, insufficient, or inconsistent. Synthesised evidence was graded as high, moderate, low or very low (GRADE approach).

RESULTS

Thirty-four studies (21 languages and 26 different versions) were included from 4402 articles. A total of 141 measurement properties were reported with 60 rated as very good or adequate. These included; internal consistency (19), test-retest reliability (4), construct validity (6), structural validity (10), measurement error (5), responsiveness (9), and cross-cultural validity (2). Comprehensibility was adequate in the Chinese, German, Nepali, Spanish and Urdu versions. Only the Danish, Dutch and Nepali versions confirmed all, or all but one, of their measurement properties with sound methodology. Pooled results of all measurement properties except structural validity were rated as sufficient. Quality of evidence was graded moderate to high with downgrading due to inconsistent results.

CONCLUSION

Overall evidence suggests the SPADI is valid, reliable and responsive in translated form but less than half the measurement properties tested were of adequate quality. Further testing is required in many languages particularly in; test-retest reliability, measurement error and construct validity.

Reducing shoulder complaints in employees with high occupational shoulder exposures: study protocol for a cluster-randomised controlled study (The Shoulder-Café Study)

Background

In Denmark, exercise therapy in combination with work modification is the first-choice treatment for persons with shoulder complaints and high occupational shoulder exposures. To obtain this treatment they must visit several healthcare providers, which makes usual care fragmented and uncoordinated. Therefore, we developed a new intervention which unifies the expertise that is needed. The main hypotheses are that a group-based Shoulder-Café intervention will more effectively reduce (1) shoulder complaints and (2) occupational shoulder exposures than an individual-based Shoulder-Guidance intervention (active control – enhanced usual care).

Methods

A cluster-randomised trial is conducted including 120 employees with high occupational shoulder exposures. Companies (clusters) are randomised to either Shoulder-Café or Shoulder-Guidance with a 1:1 allocation ratio. Participants are 18–65 years old and have an Oxford Shoulder Score (OSS) ≤ 40. Both interventions include a home-based shoulder-exercise programme, assessment of shoulder exposures by technical measurements and self-report, and general information on how to reduce shoulder exposures. The Shoulder-Café course also includes three café meetings with physiotherapist-supervised exercises, clinical shoulder evaluation, education on shoulder anatomy, workplace-orientated counselling, and an opportunity for a workplace visit by a health and safety consultant. The primary outcomes are the OSS at 6-month follow-up (hypothesis I), and the mean number of min/day with the arm elevated > 60° shortly after the end of the intervention (hypothesis II). We will use a mixed-model analysis that allows for company clustering, and data will be analysed according to the intention-to-treat principle.

Discussion

Persons with shoulder complaints and high occupational shoulder exposures are an obvious target group for secondary prevention efforts. We developed the Shoulder-Café to reduce shoulder complaints and shoulder exposures while unifying the expertise that is needed to evaluate and treat shoulder complaints. If the intervention is effective, it would warrant widespread implementation.

Trial registration

Clinicaltrials.gov, ID: NCT03159910. Registered on 18 May 2017

Which patients are less likely to improve after arthroscopic rotator cuff repair?

OBJECTIVE

The aim of this study was to evaluate which specific factors influence the improvement in function and to estimate the time to obtain pain relief following arthroscopic rotator cuff repair.

METHODS

A total of 97 patients (57 men and 40 women; mean age: 55.5 ± 9.3 years) who had arthroscopic rotator cuff repair between 2013 and 2016 were included into the study. Multivariable stepwise analysis included preoperative variables (age, gender, body mass index, comorbidities, occupation and participation in sports, Oxford shoulder score at baseline, preceding injury and duration of preoperative symptoms) and arthroscopic findings (size of rotator cuff tear, pathology of the long head of the biceps and cartilage lesions). The change in the Oxford shoulder score at the last follow-up was modeled as a function of the above predictor variables. The time to regain a visual analogue scale (VAS) under two points following surgery was considered the time to regain substantial pain relief.

RESULTS

The mean follow-up time was 33.2 ± 14.4 months. Twenty three patients had partial thickness and seventy four had full thickness supraspinatus tears. In third of the patients the tears were defined as large full thickness. At the last follow-up the mean Oxford shoulder score improved from 13.8 ± 4.8 to 42.1 ± 7.2 points (P < 0.001). The mean VAS improved from a preoperative score of 6.7 ± 1.3 points to 1.5 ± 0.6 points postoperatively (P < 0.001) and 80 (83%) patients declared they were satisfied to have had the operation. The mean time interval for substantial pain relief was 4.9 ± 3.6 months. Patients with higher preoperative Oxford shoulder score and larger tear size were correlated with lesser improvement in Oxford shoulder score (R = 0.5, P = 0.001).

CONCLUSION

Arthroscopic rotator cuff repair improved pain and function at an average follow-up of three years. A substantial pain relief was regained within five months from surgery. Larger rotator cuff tear size and more favorable preoperative function were predictors of worse postoperative function.

LEVEL OF EVIDENCE

Level IV, Therapeutic study.

Nepali translation, cross-cultural adaptation and measurement properties of the Shoulder Pain and Disability Index (SPADI)

Background

The Shoulder Pain and Disability Index (SPADI) is a 13-item shoulder-specific patient-reported outcome measure (PROM). The English version is easy to use and has demonstrated excellent measurement properties for both clinical and research settings. The availability of the SPADI in Nepali would facilitate shoulder research and enhance management of patients with shoulder pain in Nepal. Therefore, the purpose of this study was to translate and cross-culturally adapt the SPADI into Nepali (SPADI-NP) and evaluate its measurement properties.

Methods

The translation and adaptation process followed international guidelines. Participants completed SPADI-NP on two assessments (N = 150 at initial and 119 at follow-up assessment). A Nepali version of the Global Rating of Change score was completed at follow-up. Assessment of measurement properties included analysis of internal consistency (Cronbach’s α), minimal detectable change (MDC) with standard error of measurement (SEM), test-retest reliability (intraclass correlation coefficient; ICC), validity (factor structure, construct using Pearson’s correlation with the Disability of Arm and Hand [DASH]) and responsiveness (area under the curve; AUC) with minimal important change (MIC).

Results

Minor changes were integrated in the adaptation process to improve cultural relevance such as dress items. Items were largely loaded under two factors (pain and disability), internal consistencies were good for the pain construct (α = 0.82) and disability (α = 0.88) and test-retest reliability was excellent (pain = 0.89, disability = 0.96). MDC was 5.7 (out of 100) with SEM = 2.1. Strong associations with the DASH (r = 0.63 pain, r = 0.81 disability) demonstrated its construct validity. The AUC was 0.68 and MIC was 12.3 (out of 100).

Conclusion

The Nepali version of the SPADI demonstrated excellent reliability and validity. It can be used for the assessment of shoulder pain and disability in patients with shoulder pain in Nepal in both clinical practice and research.

The operative treatment of shoulder pain in patients with a concurrent diagnosis of cervical spondylosis and shoulder dysfunction

Background

Etiology of neck and shoulder pain may be multifactorial. When surgical intervention is indicated, the choice of whether to start with spine or shoulder surgery is an important clinical decision to make based on severity of pathologies, comorbidities, and patient preference. The literature includes with very few studies exploring the incidence or results of the surgical treatment paths followed in this clinical situation. This study compares patient-reported outcomes of patients with both cervical spine and shoulder pathology who underwent intervention for cervical, shoulder, or both pathologies.

Methods

The authors retrospectively reviewed 154 charts at a single institution between 2009-2017 who had both cervical spine and shoulder pathology while undergoing operative intervention of one or both pathologies. For each patient, demographics, patient-perceived success, NRS pain scores, functional outcomes (Focus on Therapeutic Outcome scores and neck disability index scores), and post-operative opioid use were reported.

Results

Patient-reported success (P=0.85), NRS pain score decreases (P=0.45), all functional outcomes except for final external rotation range of motion (P=0.02), and post-operative opioid use (P=0.30) were similar when comparing only cervical spine to shoulder intervention. Success (P=1.00), NRS pain score decreases (P=0.37), both functional outcomes, and post-operative opioid use (P=0.08) were all similar when comparing patients who underwent cervical then shoulder intervention to shoulder then cervical intervention. Finally, statistical significance was found when comparing reported success (P=0.0004) but not NRS decreases (P=0.18), functional outcomes, or post-operative opioid use (P=0.43) in patients who underwent both operation types versus only one.

Conclusions

Similar outcomes are seen when comparing isolated surgical intervention types and order of surgeries when undergoing both interventions. Multiple surgical intervention types, regardless of order, tends to result in higher rates of patient-reported success but similar post-operative outcomes compared to one.

Arthroscopic rotator cuff surgery following shoulder trauma improves outcome despite additional pathologies and slow recovery

PURPOSE

To compare the outcome, recovery and surgical findings after shoulder arthroscopy of clinically defined traumatic and non-traumatic rotator cuff pathology in middle-aged patients.

METHODS

Of the patients who underwent rotator cuff surgery, 37 patients who reported a preceding shoulder injury related to their shoulder symptoms (traumatic group) were compared to a control group of 58 patients without a preceding injury (non-traumatic group), matched by age, body mass index and comorbidities. Data included demographic details, patient history, surgical findings, the Oxford Shoulder Score questionnaires and overall satisfaction from surgery.

RESULTS

The mean follow-up time was 33.2 ± 14.4 months. More concomitant pathologies were found in the study group. The proportion of large and massive supraspinatus tears was double in the study group (43%) compared to the control group (22%). The Oxford Shoulder Score (OSS) improved significantly after surgery in both groups (p < 0.001) with no differences between groups in OSS and overall satisfaction from surgery. Patients in the study group felt recovered at an average time of 6.1 ± 4.6 months from surgery, while patients in the control group felt recovered at 4.2 ± 2.6 months (p = 0.02). Patients who were operated at the first 6 months after the injury had better improvement in OSS than patients who were operated later.

CONCLUSION

Surgical arthroscopy for rotator pathology of the shoulder in middle-aged patients improved pain and function regardless of a traumatic onset; however, earlier repair after trauma resulted in better outcome scores. Larger full-thickness tears and concomitant pathologies were more common after injury.

STUDY DESIGN

Level III.

Rasch validation of the Danish version of the shoulder pain and disability index (SPADI) in patients with rotator cuff-related disorders

PURPOSE

The psychometric properties of the shoulder pain and disability index (SPADI) have been extensively evaluated using classical test theory, but very few studies have applied Rasch analysis. The purpose of this study was to validate the Danish version using Rasch analysis.

METHODS

Responses to the SPADI from 229 patients (48% female, mean age 54.5) were included in the Rasch analysis. Overall fit, individual item fit, local response dependence, dimensionality, targeting, reliability, and differential item functioning (DIF) were examined.

RESULTS

After iterative analyses, good fit to the Rasch model was observed, with acceptable targeting and uni-dimensionality. SPADI should be reported as two separate subscales: Pain and Functional Disability. The pain subscale initially demonstrated misfit due to local dependence and DIF, but a log linear Rasch model showed good fit to the Rasch model with acceptable targeting and uni-dimensionality. A six-item version of the disability subscale exhibited adequate fit in the Danish version. The same items were also found to fit the Rasch model in the English version.

CONCLUSIONS

The measurement properties of the Danish SPADI are similar to those of the English version. SPADI should be reported as two separate subscales. For the pain subscale, DIF with respect to age was disclosed, but the impact was small. The eight-item disability subscale did not fit the Rasch model. A six-item version of the disability subscale exhibited adequate fit in the Danish version. The same items were also found to fit the Rasch model in the English version.

An evaluation of the structural validity of the shoulder pain and disability index (SPADI) using the Rasch model

PURPOSE

The shoulder pain and disability index (SPADI) has been extensively evaluated for its psychometric properties using classical test theory (CTT). The purpose of this study was to evaluate its structural validity using Rasch model analysis.

METHODS

Responses to the SPADI from 1030 patients referred for physiotherapy with shoulder pain and enrolled in a prospective cohort study were available for Rasch model analysis. Overall fit, individual person and item fit, response format, dependence, unidimensionality, targeting, reliability and differential item functioning (DIF) were examined.

RESULTS

The SPADI pain subscale initially demonstrated a misfit due to DIF by age and gender. After iterative analysis it showed good fit to the Rasch model with acceptable targeting and unidimensionality (overall fit Chi-square statistic 57.2, p = 0.1; mean item fit residual 0.19 (1.5) and mean person fit residual 0.44 (1.1); person separation index (PSI) of 0.83. The disability subscale however shows significant misfit due to uniform DIF even after iterative analyses were used to explore different solutions to the sources of misfit (overall fit (Chi-square statistic 57.2, p = 0.1); mean item fit residual 0.54 (1.26) and mean person fit residual 0.38 (1.0); PSI 0.84).

CONCLUSIONS

Rasch Model analysis of the SPADI has identified some strengths and limitations not previously observed using CTT methods. The SPADI should be treated as two separate subscales. The SPADI is a widely used outcome measure in clinical practice and research; however, the scores derived from it must be interpreted with caution. The pain subscale fits the Rasch model expectations well. The disability subscale does not fit the Rasch model and its current format does not meet the criteria for true interval-level measurement required for use as a primary endpoint in clinical trials. Clinicians should therefore exercise caution when interpreting score changes on the disability subscale and attempt to compare their scores to age- and sex-stratified data.