Shoulder arthroplasty (SA) is an accepted means of pain relief

Transcription

1 Jean-Sébastien Roy, PT, PhD1 Joy C. MacDermid, PT, PhD2 Kenneth J. Faber, MD3 Darren S. Drosdowech, MD3 George S. Athwal, MD3 The Simple Shoulder Test Is Responsive in Assessing Change Following Shoulder Arthroplasty Shoulder arthroplasty (SA) is an accepted means of pain relief and improving function in patients with advanced joint destruction. 35 Measures of physical impairment and selfreported function are commonly used to assess the outcomes of these procedures. Various self-reporting scales are available to measure the functional outcome of shoulder surgery, but only a few have both rigorous development and subsequent validation by authors not involved in the scales development. 20 t STUDY DESIGN: Prospective cohort study with repeated measures. t OBJECTIVE: To establish the responsiveness of the Simple Shoulder Test (SST) in comparison to other commonly used clinical outcomes in patients undergoing shoulder arthroplasty. t BACKGROUND: Responsiveness statistics are a useful means to compare different outcomes in terms of their ability to detect clinical change. While the responsiveness of the SST has been established for rotator cuff repair, it has not been determined for patients undergoing arthroplasty. t METHODS: Patients undergoing shoulder arthroplasty (n = 120) were evaluated prior to surgery and 6 months after. The evaluation included the SST, Disabilities of the Arm, Shoulder and Hand questionnaire, range of motion, and isometric strength. Responsiveness to change was assessed using standardized response mean (SRM), while longitudinal construct validity was evaluated using Pearson correlation. Receiver operating characteristics curves were plotted to determine clinically important difference of SST. t RESULTS: The SST and Disabilities of the Arm, Shoulder and Hand questionnaire were highly responsive (SRM, 1.70) for this population. For the assessment of impairment, range of motion (SRM, ) was moderately to highly responsive, while isometric strength was minimally to moderately responsive (SRM, ). The clinically important difference of the SST was established at 3.0 SST points. Pearson correlations indicated moderate associations between the change scores of the SST and the Disabilities of the Arm, Shoulder and Hand questionnaire (r = 0.49). t CONCLUSIONS: The SST has been previously shown to be valid and highly reliable. The present results show that the SST is also responsive following shoulder arthroplasty and that it has a clinically important difference of 3.0 SST points. This should provide confidence to clinicians who wish to use a brief shoulder-specific measure in their practice. J Orthop Sports Phys Ther 2010;40(7): doi: /jospt t KEY WORDS: psychometric properties, questionnaire, responsiveness, shoulder The Simple Shoulder Test (SST) is a shoulder-specific scale that has been used to characterize changes over time following SA. 5,6 Previous studies have shown that the SST is valid and reliable. 3,10,30 In fact, its reliability has been shown to be superior to other shoulder-specific scales. 3 Responsiveness of the SST for patient undergoing SA has only been evaluated by Beaton and Richards. 3 They found a standardized response mean (SRM) of 0.87 on a small cohort of improved patients (n = 33) following rotator cuff surgery and total shoulder arthroplasty (TSA). In their improved cohort, less than 14 patients had undergone TSA. Responsiveness of the SST has been more commonly evaluated in patients undergoing rotator cuff repair. 3,20,27 In contrast to sensitivity to change, which refers to the ability of an instrument to measure change in a condition regardless of whether it is relevant to the decision maker, responsiveness refers to the ability of an instrument to measure a meaningful or clinically important change in a clinical status. 16 This measurement property is conveyed using specific statistical indices. Among them, effect size (ES), calculated based on the mean change score divided by the standard deviation of the baseline values, and SRM, calculated based on the mean change score divided by the standard deviation of the change score, are often used. Based on subjective classification, these indices are considered large when they exceed 0.8, 1 Postdoctoral Fellow, School of Rehabilitation Science, McMaster University, Hamilton, Ontario, Canada. 2 Associate Professor, School of Rehabilitation Science, McMaster University, Hamilton, Ontario; Co-Director, Clinical Research Lab, Hand and Upper Limb Centre, St Joseph s Health Centre, London, Ontario, Canada. 3 Orthopaedic Surgeon, Hand and Upper Limb Centre, St Joseph s Health Centre, London, Ontario, Canada. Research protocol approved by the Institutional Review Board of the University of Western Ontario. Address correspondence to Dr Jean-Sébastien Roy, School of Rehabilitation Science, McMaster University, IAHS, 1400 Main Street West, Hamilton, Ontario, Canada, L8S 1C7. jean-sebastien.roy.1@ulaval.ca journal of orthopaedic & sports physical therapy volume 40 number 7 july

2 moderate when they are between 0.5 and 0.8, and small when they are between 0.2 and The clinically important difference (CID), also referred to as minimal clinically important difference (MCID), is another indicator of responsiveness that reflects the minimal change required to demonstrate clinically relevant improvement (expressed in the same units as the original measurement). Along with responsiveness, longitudinal construct validity can be evaluated as a means of validating the use of measures for longitudinal assessment. This requires determining whether the change over time observed on different scales correlates to the extent consistent with their conceptual relatedness. While less directly related to clinical practice than measures of responsiveness, this is a common component of validation. It is important that responsiveness is evaluated across populations and interventions because these factors may alter performance. While the responsiveness of the SST has been established for rotator cuff repair, it has only been evaluated on a small subset of patients undergoing SA. Furthermore, the CID has not been reported for the SST. 30 Measures of CID are essential for setting treatment goals and evaluating the clinical impact of a treatment. Therefore, the purpose of this study was to determine the responsiveness and longitudinal construct validity of the SST in comparison to other commonly used outcomes instruments in patients undergoing SA. METHODS Study Design This prospective cohort study evaluated patients preoperatively and 6 months postoperatively. At each occasion, outcome measures were obtained by evaluators not involved in the care of the patients. Psychometric analyses were conducted. Participants and Evaluations One-hundred forty-two patients who were scheduled to have a SA were enrolled (number of eligible patients, 246; 58% of eligible patients were recruited). Depending on the indications for surgery, 3 types of SA were performed: hemiarthroplasty, TSA, and reverse total shoulder arthroplasty (RSA). Inclusion criteria were (1) ability to complete self-reported questionnaires in English and (2) providing a written informed consent. This study was approved by the Institutional Review Board of the University of Western Ontario. Informed consent was obtained from all participating subjects, and their rights as human subjects were protected. Outcome measures assessed at each evaluation included (1) SST, (2) the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, (3) SF-12, (4) shoulder active range of motion (ROM), and (5) shoulder isometric strength. Some patients (33% of the sample) chose not to complete the ROM and strength testing procedures and only the selfreported questionnaires during some follow-up visits, either for lack of time, fatigue, or inconvenience. The patients were assessed by experienced research assistants following standardized testing protocols. Outcome Measures Simple Shoulder Test The SST is a selfreported shoulder-specific questionnaire that measures functional limitations of the affected shoulder in patients with shoulder dysfunction. 18 The SST consists of 12 questions with dichotomous (yes/ no) response options. For each question, the patients indicate that they are able or are not able to do the activity. The scores range from 0 (worst) to 12 (best). 18 Disabilities of the Arm, Shoulder, and Hand Questionnaire The DASH is a self-reported questionnaire that was developed to measure physical disability and symptoms of the upper limb in patients with upper extremity disorders. 12 It is a 30-item scale that addresses difficulty in performing various physical activities that require upper extremity function (21 items); symptoms of pain, activity-related pain, tingling, weakness, and stiffness (5 items); or impact of disability and symptoms on social activities, work, sleep, and psychological well-being (4 items). Response options are rated on a 5-item Likert scale. The final score range from 0 (no disability) to 100 (most severe disability). The DASH has been shown to be valid and reliable (ICC, approximately 0.90), 30 as well as responsive for patient undergoing SA (ES and SRM, 1.19). 1,30 SF-12 The SF-12 was developed as a shorter alternative to the SF-36. The 12 questions on the SF-12 allow calculation of a mental component summary score, which addresses limitations from emotional problems, and a physical component summary score, which addresses physical health and possible limitations from physical health problems. Response options are rated on a 5-item Likert scale. The final score ranges from 0 to 100, and higher scores indicate a better self-reported health-related status. Validity testing of the SF-12 showed high correlations with the physical and mental component summary scores of the SF-36 (ICC 0.92). 14,33 Furthermore, it has been shown to have good to excellent reliability (ICC 0.75) 32,34 and to be moderately responsive (SRM, ) in populations with musculoskeletal disorders. 33 Range of Motion Active shoulder flexion, abduction, internal rotation, and external rotation ROM were measured in degrees using a goniometer. Flexion and abduction were measured seated with the elbow in extension and shoulder in neutral rotation, while internal rotation was measured supine with the shoulder abducted in the frontal plane to 90 and the elbow flexed to 90. External rotation was measured in both the sitting (at 0 of abduction) and supine (at 90 of abduction) positions with the elbow flexed to 90. The scapula was stabilized during internal rotation by the research assistant to avoid protraction of the shoulder girdle. The scapula was not stabilized for external rotation measurements. The 414 july 2010 volume 40 number 7 journal of orthopaedic & sports physical therapy

3 olecranon process was used as the axis of rotation for the rotations. Intratester reliability of shoulder goniometry using this approach has been shown to be excellent for passive movement. 19 However, it has not been established for active movement as used in the present study. Strength Shoulder flexion, internal rotation, and external rotation isometric strength were measured in Newton meters using the LIDO computerized dynamometer (Loredan Biomedical, Sacramento, CA). Testing was performed with patients seated with both feet flat on the floor. The arm to be tested was positioned in the plane of the scapula (30 of forward flexion and 45 of abduction). 15 The subject grasped a handgrip, using a neutral forearm pronation/supination position. During internal and external rotations, the resistance arm was applied through the handgrip. For flexion, instead of the application of force through the handgrip, as recommended in the LIDO manual, a customized padded upper-arm contact attachment was used. 29 This customized attachment allowed measurement of shoulder flexion strength directly. Three measurements were averaged for each muscle group. The LIDO WorkSET (Loredan Biomedical) has been shown to have excellent reliability in the measurement of isometric shoulder strength in individuals with rotator cuff pathology (ICC 0.88). 21 Analyses Because the statistical methods underlying SRM assume that all patients change in the same direction, 16 patients were subdivided into 3 subgroups according to their changes in the DASH and SST at 6 months: (1) those who had positive changes in their total score on both scales were labeled as improved, (2) those who had negative changes on both scales were labeled as worse, and (3) the remaining patients were labeled as having equivocal responses. 20 A mixed-model analysis of variance (ANOVA) was calculated to compare the baseline and 6-months scores of the TABLE 1 response subgroups and types of arthroplasty. The factors in the model were evaluation time (2 levels: baseline versus 6 months), response subgroups (2 levels: improved versus equivocal-worse responses), and types of surgery (3 levels: hemiarthroplasty, TSA, and RSA). According to the results of the mixedmodel ANOVA, the following multiple pairwise comparisons were performed: 1-way ANOVA with Bonferroni post hoc test for the types of surgery, independent t tests for response subgroups, and paired t test for evaluation time. A Bonferroni adjustment was performed for multiple t tests. Independent t tests (age, and baseline SST, DASH, and SF-12 scores) and chi-square tests (sex and types of surgery) were also used to compare the baseline characteristics of the subjects who chose or declined to complete the ROM and strength testing procedure. SPSS, Version 17.0 (SPSS Inc, Chicago, IL) was used for all analyses. The SRM, calculated as the mean change score divided by the standard deviation of the change score, 17 were determined for the whole arthroplasty group, for the 2 response subgroups (improved, worse-equivocal) and for each type of arthroplasty. SRM were considered large if greater than or equal to 0.8, moderate if between 0.5 and 0.8, and small if between 0.2 and 0.5. Confidence intervals (95% CI) were calculated around the SRM. 36 Baseline Patients' Characteristics Characteristics overall (n = 120) improved (n = 94) equivocal and Worse (n = 26) Age (mean SD y) Sex (male/female) 54/66 47/47 7/19 Handedness (right/left) 110/10 87/7 23/3 Treated side (right/left) 74/46 56/38 18/8 Type of arthroplasty Sample Description Hemiarthroplasty Total arthroplasty Reverse arthroplasty Previous shoulder surgery (yes/no) 46/74 32/62 14/12 Traumatic injury (yes/no) 58/62 45/49 13/13 The ESs, calculated as the mean change score divided by the standard deviation of baseline values, 13 were also calculated but are only presented in the TABLES. Spearman (for the SST) and Pearson correlations (for the DASH, SF-12, ROM, and strength measures) between the change scores were calculated to determine the longitudinal construct validity. Finally, receiver operating characteristics (ROC) curves were plotted to determine the amount of change on the SST that best differentiates those patients who have improved from those who have remained stable or deteriorated. 8 There are a variety of methods to provide an external criterion to establish the patients that have clinically changed, including global rating of change by clinicians or patients. Because global ratings of change can be affected by recall bias, and because the DASH has had numerous investigations to determine its CID, the DASH CID was used as an external criterion of change. The ROC curve was constructed by plotting sensitivity versus 1-specificity of the SST classification. Because previous studies have shown that the CID for the DASH is 10.2 points, 32 this criterion was used as a cut-off for establishing clinically important change. That is, patients who improved more than 10.2 points on their DASH score at 6 months were categorized as having achieved a clinical important change compared to those journal of orthopaedic & sports physical therapy volume 40 number 7 july

4 TABLE 2 Self-Reported Scales, Range of Motion, and Strength Scores at Baseline and 6-Month Follow-up* Abbreviations: DASH, Disabilities of the Arm, Shoulder and Hand questionnaire; ER, external rotation; IR, internal rotation; ROM, range of motion; SST, Simple Shoulder Test. * Values are mean SD. Significant differences at 6 months between improved patients and patients with equivocal-worse responses. baseline 6 Months baseline 6 Months SST (0-12) DASH (0-100) SF-12 mental (0-100) SF-12 physical (0-100) ROM ( ) Flexion Abduction ER sitting ER supine IR supine Strength (Nm) Flexion ER IR TABLE 3 Hemiarthroplasty (n = 27) Improved Equivocal and Worse Self-Reported Scales Scores at Baseline and 6-Month Follow-up According to the Type of Surgery* Abbreviations: DASH, Disabilities of the Arm, Shoulder and Hand questionnaire; SST, Simple Shoulder Test. * Values are mean SD. Significant differences at 6 mo between patients undergoing total shoulder arthroplasty and patients undergoing hemiarthroplasty or reverse shoulder arthroplasty. Significant differences at baseline between patients undergoing total shoulder arthroplasty and patients undergoing reverse shoulder arthroplasty. baseline 6 mo SST (0-12) DASH (0-100) SF-12 mental (0-100) SF-12 physical (0-100) Total shoulder arthroplasty (n = 62) SST (0-12) DASH (0-100) SF-12 mental (0-100) SF-12 physical (0-100) Reverse shoulder arthroplasty (n = 31) SST (0-12) DASH (0-100) SF-12 mental (0-100) SF-12 physical (0-100) who had 0- to 10.1-point change score. A threshold for clinically substantial change was also defined to reflect larger treatment effects. Therefore, patients who had an improvement of more than 20.4 DASH points were compared to those who had an improvement of 10.2 to 20.3 DASH points. The area under the curve was evaluated for significance, with α =.05. By examination of the intersections of the sensitivity and 1-specificity plots nearest to the upper left hand corner of the graph, the optimal cut-off value for maximal average sensitivity and specificity for detecting change could be identified. 28 RESULTS Of the 142 patients enrolled in the study, 22 patients (TSA, 14 patients; RSA, 7 patients; and hemiarthroplasty, 1 patient) either did not complete both SST and DASH or did not properly complete 1 of them, leaving 120 patients for data analyses (84% of the original sample) (TABLE 1). Twenty-seven patients (22%) had a hemiarthroplasty, 62 (52%) had a TSA, and 31 (26%) had a RSA. At follow-up, 94 patients (78.3%) had improved scores on both SST and DASH, 4 (3.3%) had worse scores on both questionnaires, and 22 (18.3%) had equivocal scores. Because only 4 patients were worse after the surgery, patients having equivocal and worse responses were combined in 1 subgroup. There were no significant differences for age, sex, type of surgery, and baseline scores on SST, DASH, and SF-12 between the subjects who chose or declined to complete the ROM and strength testing procedures. Evaluation time by response subgroups interaction effects were observed for the SST (F = , P.001), DASH (F = , P.001), and for the mental (F = , P =.001) and physical (F = , P =.001) components of the SF- 12. In addition, an interaction effect for evaluation time by types of arthroplasty was observed for the SST (F = 4.437, P =.014). Therefore, for these outcomes, the 416 july 2010 volume 40 number 7 journal of orthopaedic & sports physical therapy

5 TABLE 4 effects of response subgroups and types of surgery were analyzed independently at each evaluation time (baseline and 6-months). At baseline, there were no significant differences for SST, DASH, and SF-12 scores between the 2 responses subgroups. As expected, at 6 months, patients classified as improved had better SST (t = 5.237, P.001), DASH (t = 5.800, P.001), and SF-12 mental (t = 2.361, P =.020) and physical (t = 2.560, P =.012) components scores compared to those classified as equivocal-worse (TABLE 2). At baseline, there were no significant differences for the SST scores between Responsiveness of Self-Report Measures in Each Response Subgroup es SRM (95% CI) es SRM (95% CI) SST (1.41, 2.05) (0.09, 0.91) DASH (1.44, 2.09) ( 0.75, 0.04) SF-12 mental (0.13, 0.56) ( 1.08, 0.17) SF-12 physical (0.51, 0.94) ( 0.27, 0.50) Abbreviations: CI, confidence interval; DASH, Disabilities of the Arm, Shoulder and Hand questionnaire; ES, effect size; SRM, standardized response means; SST, simple shoulder test. TABLE 5 Hemiarthroplasty (n = 17) Improved (n = 94) Equivocal and Worse (n = 26) Responsiveness of Self-Report Measures in Patients Improved Following Shoulder Arthroplasty es SRM (95% CI) SST (0.95, 2.48) DASH (0.71, 2.07) SF-12 mental ( 0.25, 0.74) SF-12 physical (0.19, 1.26) Total shoulder arthroplasty (n = 54) SST (1.48, 2.39) DASH (1.40, 2.29) SF-12 mental (0.07, 0.62) SF-12 physical (0.56, 1.19) Reverse shoulder arthroplasty (n = 23) SST (1.02, 1.83) DASH (1.33, 2.50) SF-12 mental ( 0.05, 0.85) SF-12 physical ( 0.08, 1.33) Abbreviations: CI, confidence interval; DASH, Disabilities of the Arm, Shoulder and Hand questionnaire; ES, effect size; SRM, standardized response means; SST, simple shoulder test. the 3 types of arthroplasty; whereas, at 6 months (F = , P.001), patients with a TSA had better SST scores compared to patients with a RSA (P =.001) and hemiarthroplasty (P.001) (TABLE 3). Finally, a type of surgery effect was observed for the DASH (F = 5.139, P =.007), showing that patients undergoing a TSA have better DASH scores compared to patients undergoing RSA and hemiarthroplasty (P.001) (TABLE 3). Responsiveness Overall, large responsiveness was observed for both the SST (SRM, 1.73) and the DASH (SRM, 1.76) in improved patients, with 95% CI above 0.80 for both scales (TABLE 4). The physical (SRM, 0.74) and mental (SRM, 0.34) components of the SF-12 demonstrated small to moderate responsiveness. Moderate to large positive treatment effects were observed using the SST (SRM, 0.50) on patients who had equivocal-worse responses (TABLE 4). In contrast, the DASH scores of patients classified as equivocal or worse demonstrated small negative effects (SRM, 0.36). This can be explained by the fact that, as observed in TABLE 2, patients with equivocal-worse responses had an improvement on the SST but deterioration on the DASH (TABLE 2). Moderate negative effects were also observed for the mental component of the SF-12. For the 3 types of arthroplasty, comparable levels of responsiveness were observed for the improved patients (TABLE 5). They were characterized by large effects for the SST (SRM, 1.43 to 1.94) and DASH (SRM, 1.39 to 1.91), moderate to large effects for the physical component of the SF-12 (SRM, 0.63 to 0.88), and small effects for the mental component of the SF-12 (SRM, 0.24 to 0.40). The responsiveness for shoulder ROM was large for flexion, abduction, and supine external rotation (SRM, 0.89 to 1.03), whereas it was moderate to large for sitting external rotation and supine internal rotation (SRM, 0.64 to 0.80) (TABLE 6). As for shoulder isometric strength, moderate responsiveness indices were observed for flexion and external rotation (SRM, 0.69 and 0.62), and small responsiveness indices for internal rotation (SRM, 0.32). Minimal Clinically Important Difference Using ROC curves (FIGURE), the highest area under the curve (AUC) was recorded for the substantial clinical change curve (n = 87; AUC, 0.745, fair discriminative abilities) compared to the important clinical change curve (n = 101; AUC, 0.661, poor discriminative abilities). 24 The 2 curves showed discriminative abilities (P.001) journal of orthopaedic & sports physical therapy volume 40 number 7 july

6 TABLE 6 Range of motion Responsiveness of Impairment Measures in Patients Improved Following Shoulder Arthroplasty Abbreviations: CI, confidence interval; ES, effect size; SRM, standardized response means. es SRM (95% CI) Flexion (0.48, 1.48) Abduction (0.46, 1.33) External rotation sitting (0.35, 0.93) External rotation supine (0.47, 1.60) Internal rotation supine (0.28, 1.32) Strength Improved patients Flexion (0.31, 1.06) External rotation (0.28, 0.96) Internal rotation (0.00, 0.64) Sensitivity Specificity Important clinical change (AUC, 0.661) Substantial clinical change (AUC, 0.745) FIGURE. Receiver operating characteristics (ROC) curves for the Simple Shoulder Test (SST) cut points for differentiating clinically important difference. The ROC curve was constructed by plotting sensitivity versus 1 specificity for all possible cut-off values of the SST. The cut-off point varied for differentiation between those patients who were improved by more than 10.2 Disabilities of the Arm, Shoulder and Hand (DASH) points (important clinical change curve) or 20.4 DASH points (substantial clinical change curve) and those who did not. The point closest to the far left corner is the clinically important difference, which was 3.0 SST points for each curve. A higher area under the curve (AUC) represents a higher ability to distinguish between patients who had a meaningful change and those who did not. that were statistically better than chance (AUC, 0.50). The optimal cut-off point (point nearest the upper left-hand corner of the graph), which defined the CID, was 3.0 SST points for both curves. For the substantial clinical change curve, the sensitivity of the cut-off point was 65% and specificity 74%; whereas, for the important clinical change curve, the sensitivity was 62% and specificity 59%. Longitudinal-Construct Validity There were significant correlations between change score on the SST and change score on (1) the DASH, (2) the physical component of the SF-12, (3) abduction and sitting external rotation ROM, and (4) flexion and external rotation isometric strength (TABLE 7). Significant correlations were also observed between change score on the DASH and change score on the physical and mental components of the SF-12 (TABLE 7). The DASH was not correlated with ROM and strength. Discussion Our study suggests that both the SST and DASH have the ability to detect clinical improvement and to discriminate between different responses following SA. With results showing similar level of responsiveness, the main advantage of the SST over the DASH is that it has been shown to be quicker to complete, 30 which makes it easier to use in clinical settings. Correlations between change score on the SST and on the DASH were significant but of a lower magnitude than expected. Change score on the SST was also correlated with change score on abduction and external rotation ROM and on flexion and external rotation isometric strength. Other researchers have evaluated the responsiveness of shoulder-specific scales in patient undergoing SA. Angst et al 1 compared the responsiveness of 3 self-reported shoulder questionnaires (DASH, Shoulder Pain and Disability Index [SPA- 418 july 2010 volume 40 number 7 journal of orthopaedic & sports physical therapy

7 TABLE 7 DASH 0.50* (n = 120) Correlation Between Change Scores on Different Outcome Measures SST DASH SF-12 Physical SF-12 Mental SF-12 physical 0.32* (n = 120) 0.48* (n = 120) SF-12 mental 0.11 (n = 120) 0.25* (n = 120) 0.12 (n = 120) Strength Flex 0.45* (n = 50) 0.27 (n = 50) 0.33 (n = 50) 0.03 (n = 50) ER 0.35 (n = 50) 0.13 (n = 50) 0.19 (n = 50) 0.03 (n = 50) IR 0.05 (n = 50) 0.16 (n = 50) 0.25 (n = 50) 0.01 (n = 50) Range of motion Flex 0.33 (n = 30) 0.23 (n = 30) 0.10 (n = 30) 0.18 (n = 30) Abd 0.46* (n = 37) 0.21 (n = 37) 0.21 (n = 37) 0.20 (n = 37) ER sitting 0.30 (n = 83) 0.03 (n = 69) 0.07 (n = 69) 0.08 (n = 69) ER supine 0.00 (n = 28) 0.05 (n = 28) 0.32 (n = 28) 0.27 (n = 28) IR 0.30 (n = 28) 0.08 (n = 28) 0.37 (n = 28) 0.01 (n = 28) Abbreviations: Abd, abduction; DASH, Disabilities of the Arm, Shoulder and Hand questionnaire; ER, external rotation; Flex, flexion; IR, internal rotation; SST, simple shoulder test. * Significant at P.01. Significant at P.05. DI], and American Shoulder and Elbow Surgeons [ASES]) and the Constant- Murley score in patients (n = 150) undergoing primary TSA. They found that the 3 scales and the Constant-Murley score were highly responsive (Constant- Murley score: ES, 2.23; ASES: ES, 2.13; SPADI: ES, 2.10; DASH: ES, 1.19). The responsiveness indices observed in the present study for the SST in patients who underwent TSA (ES, 2.22) were similar to the indices observed by Angst et al. 1 Beaton and Richards 3 also compared the responsiveness of 5 self-reported shoulder questionnaires, including the SST, on patients who believed that they had improved following rotator cuff surgery and TSA. They found that the SRM of the SST was The differences in the compositions of the cohort could explain the differences observed between their responsiveness indices and ours (SRM, 1.73 versus 0.87, respectively). Beaton and Richards 3 included patients (n = 33) undergoing either a TSA or rotator cuff surgery, while patients undergoing TSA, RSA, and hemiarthroplasty were included in the present study. Because responsiveness is related to the potential for clinical improvement, scores can only be compared across similar clinical populations. 30 A limitation on the clinical application of the SST has been the lack of an established CID. 30 The CID is important to consider when evaluating change in a patient s status because it is the value that is associated with the patient s perception of meaningful change. 25 We found that 3.0 SST points (25% of the total score) was the amount of change to have a clinically relevant improvement. It means that if a patient is able to perform 3 additional activities listed on the SST, the patient has a clinically relevant improvement. For example, if a patient who scored 5.0 SST points preoperatively scores 9.0 SST points 6 months following SA, the clinician will be able to state that an improvement meaningful to the patient has been obtained because the 4.0 SST points change is greater than the CID. The CID can also be used by the clinicians to set measurable treatment goals that are meaningful to the patient. The CID of other shoulder- or upper limb-specific scales has been established. The CID of the ASES score has been established at 6.4 points (6.4% of the total score), 25 the CID of the DASH at 10.2 points (10.2% of the total score), and the CID of the SPADI at 13.1 points or 8 points (13.1% or 8% of the total score), 32 depending on the external criteria. 28 The CID of the SST represents a much larger proportion of the total score than for these other scales. The scales response options could explain these differences. Because the SST is the only shoulder disability score based on yes/no answers, the potential for detecting changes in capability along a continuum for each activity may be less than for other shoulder questionnaires. This may explain why, on average, the patients who underwent hemiarthroplasty did not demonstrate a clinically important improvement on the SST, but did on the DASH. Measures of impairment, such as ROM and strength, are often used to evaluate the effects of interventions. 2,9,15,21-23,31 Thus, it is important to understand their responsiveness. The present results suggest that 6 months after SA most measurements of shoulder ROM are moderately to highly responsive, while measurements of isometric strength are minimally to moderately responsive. However, only a limited number of subjects were evaluated for the impairment measures leading to less stable estimates of responsiveness and large 95% CIs for both ROM and isometric strength. In addition, all of the 95% CIs of the ROM and strength measurements were overlapping, which highly suggests that there was no significant difference between the responsiveness of ROM and strength measurements. However, there seems to be a trend toward better responsiveness indices for ROM measurements for this population at 6 months. Following SA, strengthening exercises are usually started 6 to 12 weeks postoperatively with gentle isometric strengthening. 4,35 Thereafter, 12 weeks postoperatively, they are progressed gradually to isotonic strengthening. 4,35 Therefore, at 6 months, journal of orthopaedic & sports physical therapy volume 40 number 7 july

8 the number of weeks during which strengthening exercises were performed was probably not large enough to bring about large changes in shoulder isometric strength. Because recovery following joint arthroplasty may take up to 1 to 2 years, 4,11 examining responsiveness in the early phase may underestimate the full impact of the arthroplasty on strength. This study has limitations. First, in contrast to other responsiveness studies, 1,25 the patients in the present study did not complete a global rating of change question at the 6-month evaluation to differentiate patients that were improved and worse, and to establish the CID of the SST. We chose not to use a global rating of change question because of concerns about recall bias and because a 1-item scale is being used to validate a multiitem scale. However, we recognize that our method is dependent on the validity of the established CID for the DASH and its transferability across samples. Nevertheless, an advantage of using the SST and DASH to subdivide the group, and of using the DASH to establish the CID of the SST was that independent ratings were completed at baseline and 6 months, thereby preventing a recall bias. None of the methods for establishing external criteria are without limitations, and, while we cannot confirm whether our approach provides an estimate of CID that is comparable to other methods, we believe it is a rational approach. The sensitivity and specificity of the CID of the SST were lower than expected, with respectively 65% and 74% for a substantial clinical change, and 62% and 59% for an important clinical change. Therefore, only 65% of the patients that had been identified by the DASH as having a substantial clinical change were correctly identified by the SST, whereas 74% of the patients who did not present a substantial clinical change on the DASH were correctly identified by the SST. This may reflect differences in the focus of each scale or the measurement performance of yes/no items for the SST. An additional limitation of this study is the limited number of subjects evaluated for their ROM and isometric strength. The 2 primary reasons why these measures were not obtained on all patients were that (1) patients were unable or had too much pain to complete strength and ROM testing prior to surgery and (2) a minority of patients became fatigued during hospital visits and chose to only complete the self-report questionnaires. Finally, the reliability of active ROM, as used in the present study, has not been established, although active goniometry of the shoulder has been shown reliable in other circumstances in healthy individuals. 26 Conclusion In previous studies, the SST has been shown to be quick to complete, 3 valid compared to other shoulder specific scale, 3,10,30 highly reliable, 3,10 and responsive following rotator cuff repair. 20 In this study we have established that it is also highly responsive following different types of shoulder arthroplasty and that it has a CID of 3.0 SST points. This should provide confidence in the SST to clinicians who wish to use a brief shoulderspecific measure in their practice. t Key Points FINDINGS: This study indicates that the SST and the DASH are highly responsive for patients undergoing shoulder arthroplasty. The CID for the SST is 3 on the 12-point SST scale. For the assessment of impairment, only shoulder ROM in abduction, flexion, and external rotation were highly responsive at 6 months. IMPLICATION: The SST or the DASH should be used to monitor progress at 6 months for patients undergoing shoulder arthroplasty. CAUTION: Only a limited number of subjects were evaluated for their shoulder ROM and isometric strength. Therefore, these responsiveness indices must be considered as less stable estimates because they were based on a smaller cohort. references 1. Angst F, Goldhahn J, Drerup S, Aeschlimann A, Schwyzer HK, Simmen BR. Responsiveness of six outcome assessment instruments in total shoulder arthroplasty. Arthritis Rheum. 2008;59: art Bandholm T, Rasmussen L, Aagaard P, Jensen BR, Diederichsen L. Force steadiness, muscle activity, and maximal muscle strength in subjects with subacromial impingement syndrome. Muscle Nerve. 2006;34: org/ /mus Beaton D, Richards RR. 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