- Email: [email protected]
Unique Substantial Clinical Benefit Values for the 12-Item International Hip Outcome Tool (iHOT-12) Based on Preoperative Level of Function
Unique Substantial Clinical Benefit Values for the 12-Item International Hip Outcome Tool (iHOT-12) Based on Preoperative Level of Function RobRoy L. Martin, Ph.D., P.T., Benjamin R. Kivlan, Ph.D., P.T., John J. Christoforetti, M.D., Andrew B. Wolff, M.D., Shane J. Nho, M.D., M.S., John P. Salvo Jr., M.D., Thomas J. Ellis, M.D., Geoff Van Thiel, M.D., M.B.A., Dean Matsuda, M.D., and Dominic S. Carreira, M.D.
Purpose: To define unique substantial clinical benefit (SCB) values for improvement on the 12-item International Hip Outcome Tool (iHOT-12) based on a preoperative self-rating of function in patients undergoing hip arthroscopy for intraarticular pathology. Methods: This was a retrospective review of prospective collected data on patients having hip arthroscopy for labral and chondral pathology and femoroacetabular impingement. On preoperative assessment and 1-year (þ/e1 month) follow-up, subjects completed the iHOT-12 and a self-categorical rating of function (“severely abnormal,” “abnormal,” “nearly normal,” or “normal”). Separate receiver operator characteristic analyses were performed for each preoperative categorical self-rating of function to determine unique SCB values for improvement-based changes in self-rating of function. Results: Of 1034 eligible patients, 733 (71%) subjects met the inclusion criteria. Subjects consisted of 537 (73%) female and 196 (27%) male subjects with a mean age of 35.3 years (standard deviation 13). At a mean of 352 (standard deviation 21) days postsurgery, changes in iHOT-12 scores of 22, 28, and 27 points were associated with acceptable accuracy in identifying those who had an improved function rating when reporting a “severely abnormal,” abnormal,” and “nearly normal” rating on preoperative assessment, respectively. The accuracy of these SCB values in predicting improvement was different depending on the patient’s preoperative rating of function. The accuracy of the SCB values in predicting improvement in those who had a “nearly normal” rating of function was not as accurate (area under the curve ¼ 0.73) compared with those who had a “severely abnormal” or “abnormal” rating of function on preoperative assessment (area under the curve ¼ 0.89; 0.89). Conclusions: This study provides surgeons with unique SCB values for the iHOT-12 based on a preoperative rating function and may allow for a more
From Rangos School of Health Sciences, Department of Physical Therapy, Duquesne University (R.L.M., B.R.K.), UPMC Center for Sports Medicine (R.L.M.), Allegheny-Singer Research Institute (J.J.C.), Pittsburgh, Pennsylvania; Texas Health Sports Medicine (J.J.C.), Allen, Texas; Hip Preservation and Sports Medicine, Washington Orthopaedics and Sports Medicine, Washington, DC (A.B.W.); Department of Orthopedic Surgery, Division of Sports Medicine, Hip Preservation Center, Rush University Medical Center, Chicago, Illinois (S.J.N.); Orthopaedic Surgery, The Sydney Kimmel Medical College at Thomas Jefferson University Hospital (J.P.S.) and Hip Arthroscopy Program, Rothman Institute (J.P.S.), Philadelphia, Pennsylvania; Orthopedic One, Ohio Orthopedic Surgery Institute, Dublin Methodist Hospital, Columbus, Ohio (T.J.E.); OrthoIllinois (G.V.T.), Rush University Medical Center (G.V.T.), US National Soccer Teams (G.V.T.), and Chicago Blackhawks Medical Network (G.V.T.), Chicago, Illinois; DISC Sports and Spine Center, Marina del Rey, California (D.M.); and Peachtree Orthopedics, Atlanta, Georgia (D.S.C.), U.S.A. The authors report the following potential conflicts of interest or sources of funding: D.M. reports editorial board membership, Orthopedics Today; paid consultant for Zimmer Biomet; and royalties for intellectual property from Smith & Nephew and Zimmer Biomet. J.J.C. reports board membership, International Society for Hip Arthroscopy; paid consultant for Arthrex;
royalties for Arthrex and Breg; employed physician at Allegheny Health Network; General Grant Funding Allegheny Singer Research Institute. A.B.W. reports paid consultant for Stryker. S.J.N. reports board membership, American Journal of Orthopedics; paid consultant for Stryker; and royalties from Ossur. J.P.S. reports paid consultant for Stryker. T.J.E. reports paid consultant for Biomet Sports Medicine; payment for lectures including service on speakers’ bureaus from Biomet Sports Medicine. D.S.C. reports board membership, the American Orthopaedic Foot and Ankle Society. G.V.T. reports consultancy for Smith & Nephew, Trainer Rx, Vericel, Zimmer; payment for lectures including service on speakers’ bureaus for Smith & Nephew, Zimmer; royalties from Zimmer; and stock/stock options from Trainer Rx. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Received July 5, 2018; accepted September 25, 2019. Address correspondence to RobRoy L. Martin, Ph.D., P.T., Rangos School of Health Sciences, Department of Physical Therapy, Duquesne University, Pittsburgh, PA. E-mail: [email protected] Ó 2019 by the Arthroscopy Association of North America 0749-8063/18812/$36.00 https://doi.org/10.1016/j.arthro.2019.09.046
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precise interpretation of score changes. SCB values of 22, 28, and 27 points on the iHOT-12 at 1-year (þ/e1 month) follow-up identified those who had an improved function rating, when reporting a “severely abnormal,” abnormal,” and “nearly normal” rating on preoperative assessment, respectively. Level of Evidence: III, retrospective comparative study
P
atient-reported outcome measures (PROMs) commonly are used to assess the success of surgery for patients undergoing hip arthroscopy. The information obtained from a PROM requires psychometric evidence to support its use, including information to interpret a change in score over time.1 Although there is evidence to support the use of PROMs in hip arthroscopy, including the 12-item International Hip Outcome Tool (iHOT-12),2 there is little known about how changes in score over time on a PROM may be affected by an individual’s functional status at preoperative assessment. The term responsiveness describes the ability of a PROM to detect a change in the patient’s status when a change has truly occurred.1 Responsiveness can objectively be defined with change in score values for minimal clinically important difference (MCID), patient acceptable symptom state (PASS), and substantial clinical benefit (SCB).3-7 The smallest change in outcome that the patient is able to appreciate can be used to define MCID, whereas a satisfactory or desired outcome status can be used to define PASS.6 SCB is considered the improvement in outcome or absolute postoperative health state that the patient considers to be a substantial or considerable improvement.3,4 MCID, PASS, and SCB are considered the lower, intermediate, and upper threshold for clinically significant outcome improvement, respectively.5 The MCID, PASS, and SCB values to define meaningful changes in score have been universally applied to patients without consideration for their preoperative level of function. It could be possible that a meaningful change in score on a PROM for someone with a low level of function on preoperative assessment could be different then a meaningful change in score for someone who is closer to normal preoperatively. In addition, the accuracy of these changes in score values also may be different based on an individual’s preoperative functional status. Responsiveness has been defined for commonly PROMs used in hip arthroscopy. This includes the iHOT-12, which was developed as a PROM appropriate to measure the impact of hip disease and effect of treatment in young, active individuals.2,8,9 Evidence to help interpret iHOT-12 scores at a follow-up time period at 1 year (þ/e 1 month) for patients undergoing hip arthroscopy for intra-articular pathology is available.2 Martin et al.2 found MCID values based on one-half the standard deviation (SD) of the change
scores and SCB based on an improvement in self-rating of function rating to be 13 and 28 points, respectively. Nwachukwu et al.10 noted a limitation in this type of study design is that SCB change scores may vary depending on the baseline level of function of the subjects. Defining unique values to interpret a change in score based on the patient’s preoperative level of function could allow for more precise interpretation of change in scores on a PROM in patients undergoing hip arthroscopy for intra-articular pathology. The purpose of this study was to define unique SCB values for improvement on the iHOT-12 based on a preoperative self-rating of function in patients undergoing hip arthroscopy for intra-articular pathology. It was hypothesized that unique values for SCB on the iHOT-12 could be identified based on preoperative rating of function.
Methods This was a retrospective review of prospectively collected data maintained in a secure electronic registry. The registry consisted of patients who consented to undergo hip arthroscopy at 1 of 7 centers within the United States. Inclusion criteria specific to this study included subjects who underwent primary surgery for labral and chondral pathology and femoroacetabular impingement between May 2014 and April 2017 with preoperative and follow-up iHOT-12 scores available. The follow-up data were collected 1-year (þ/e1 month) postsurgery. Patients were e-mailed and given a 2-month window around their 1-year surgery date (1 month before and 1 month after surgery) to complete PROMs. Exclusion criteria included those diagnosed with primary lumbopelvic pathology, advanced hip arthrosis (>Tönnis 2), primary slipped capital epiphysis or Perthes disease, or severe dysplasia (lateral center edge angle <16 ). Patients with relative contraindications to hip arthroscopy such as hip dysplasia (lateral center edge angle <25 ), acetabular index greater than 15 , high body mass index (>25), or age greater than 60 years were not excluded but handled on a case-by-case basis with the overseeing surgeon and the patient. An inability to read or understand English was also an exclusion criterion for the registry. The pre-hoc collection and storage of agreed-on clinical data points was granted according to individual institutional requirements and institutional
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SCB FOR IHOT-12 BASED ON LEVEL OF FUNCTION
review board approval granted to review the deidentified registry of patient data. Preoperatively, subjects were given the iHOT-12 and a categorical self-rating of function to complete. For follow-up data collection, subjects were emailed the iHOT-12 and self-rating of current function to complete between 335 and 395 days after surgery. Each item on the iHOT-12 was scored using a 100-mm horizontal line (visual analog scale) so that the mean of all questions amounts to the score result ranging from 0 to 100, with a greater score meaning better function, fewer symptoms, and greater quality of life.9 The self-rating of current level of function had categorical responses choices as follows: “severely abnormal,” “abnormal,” “nearly normal,” or “normal.” Demographic information was recorded from the electronic registry. Psychometric Analysis An anchor-based method was used to calculate SCB values. A SCB change score for improvement was calculated with receiver operator characteristic (ROC) analysis calculating the area under the curve (AUC) at a 95% confidence interval.11,12 A positive change in the categorical rating of function from preoperative assessment to 1-year (þ/e1 month) follow-up was used to identify patients for the “improved” group. Those who did not have a change or had a negative change in categorical rating of function were put in the “did not improve” group. These 2 groups were used to calculate SCB change score values for improvement based a “severely abnormal,” “abnormal,” “nearly normal” categorical ratings of function at preoperative assessment. The AUC for the ROC analysis is a combination of sensitivity and specificity and defines the accuracy of the iHOT-12 in distinguishing between groups.12,13 As noted in similar studies, an AUC >0.7 and a 95% confidence interval that does not contain 0.5 are considered properties of acceptable levels responsiveness while an AUC >0.8 is consider excellent.10,13,14 Youden’s Index was used to optimize sensitivity and specificity values and identify the best cutoff values for SCB that represent a score change most likely to be associated with being in the “improved” group at 1-year (þ/e1 month) follow-up for each categorical rating of function at preoperative assessment.15 Statistical analysis was performed using the SPSS software package (Version 24; SPSS Inc., Armonk, NY).
Results Participants Of 1034 eligible patients, 733 (71%) subjects met the inclusion criteria for this study and had 1-year (þ/e1 month) outcome data available for analysis. The reason for exclusion was not having 1-year follow-up data available. The average follow-up time was slightly less than 1 year, at 352 days (SD 21), as the
subjects had a 2-month window around their 1-year surgery date (1 month before and 1 month after surgery) to complete PROMs. At preoperative assessment, there were 123 (17%), 451 (62%), 133 (18%), and 26 (3%) subjects in the “severely abnormal,” “abnormal,” “nearly normal,” and “normal” groups, respectively, with 525 (72%) subjects improved and 208 (28%) not improved at follow-up. The average time between preoperative assessment and surgery was 58 days (SD 41). Preoperative characteristics of the subjects including age, sex, body mass index, hip joint morphology, and degenerative joint processes as determined by radiograph are presented in Table 1. A majority of subjects were female (73%) with morphological abnormalities to the femoral side of the hip joint without radiographic findings of significant degenerative joint disease (Tönnis grade 0 ¼ 88%). Table 2 describes the diagnoses and surgical procedures performed on the subjects. Labral pathology (97%) and femoroacetabular impingement (92%) were among the most common diagnoses arthroscopically treated. There were 577 (79%) subjects who had multiple procedures performed. The confounding diagnoses/procedures included ligamentum teres tear (10%), borderline hip dysplasia (9%), gluteus medius tear (2%), or a revision of a previous hip arthroscopy (7%). Labral repairs (64%) followed by femoroplasty (60%), synovectomy (56%), acetabuloplasty (40%), and acetabular chondroplasty (32%) were the among the most common arthroscopic procedures performed. The intraoperative arthroscopic examination demonstrated chondral damage to the hip joint in 236 (36%) subjects. The Beck Classification of Chondral damage for the cohort is reported in Table 3. Surgical treatment of the joint capsule is also reported in Table 3, which shows that a
Table 1. Preoperative Characteristics of the Subjects Who Underwent Hip Arthroscopy Age, y Body mass index LCEA Alpha angle Acetabular index
Mean 35 25.7 31 57 5
Sex Female Male Age <18 y Age >60 y Dysplasia LCEA <16 Tönnis grade 0 I LCEA, lateral center edge angle.
Standard Deviation 13 5.1 7 16 5
Range 11-73 17-51 16-60 38-120 e20-26
n
Percent (%)
537 196 60 23 14
73% 27% 8% 3% 2%
649 84
88% 12%
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Table 2. Arthroscopic Procedures and Diagnoses Labral treatment Debridement Repair Reconstruction Arthroscopic procedures Femoroplasty Synovectomy Acetabuloplasty Acetabular chondroplasty Femoral chondroplasty Acetabular microfracture Femoral microfracture Primary diagnoses Labral pathology Femoroacetabular impingement Concurrent diagnoses/procedures Ligamentum teres tear debridement Revision hip arthroscopy Gluteus medius repair Loose body removal Avascular necrosis Proximal hamstring repair Synovial chondromatosis Septic arthritis Pigmented villonodular synovitis
N
Percent (%)
182 471 62
25% 64% 8%
437 393 295 232 115 22 4
60% 56% 40% 32% 16% 3% 0.5%
715 677
97% 92%
70 54 18 5 3 2 1 1 0
10% 7% 2% 0.7% 0.4% 0.3% 0.1% 0.1% 0%
majority of patients received an interportal capsulotomy 251 (34%) with capsular closure 326 (44%). Psychometric Results The mean preoperative iHOT-12 and 1-year postoperative scores for each level of function are presented in Table 4. The results of the ROC analyses for SCB change score for improvement also are presented in Table 4 and Figure 1. Change scores of 22, 28, and 27 points on the iHOT-12 from preoperative assessment to 1-year (þ/e1 month) follow-up were associated with acceptable accuracy in identifying those who had an “improved” function rating from those that “did not improve” when reporting a “severely abnormal,” abnormal,” and “nearly normal” response at preoperative assessment, respectively. Depending on the patient’s preoperative level of function, the accuracy of these values in predicting whether a patient had reached the criteria for SCB was different. The accuracy of the SCB values in predicting improvement in those who had a “nearly normal” rating of function was not as accurate (AUC ¼ 0.73) compared with those who had a “severely abnormal” or “abnormal” rating of function at preoperative assessment (AUC ¼ 0.89, 0.89).
Discussion
The most important finding from this study was that iHOT-12 SCB values, which define whether a patient has improved their self-reported level of function at 1-year (þ/e1 month) follow-up, were relative and dependent on the patient’s preoperative self-rating of
function. The results of this study support the hypothesis as change score values of 22, 28, and 27 points on the iHOT-12 at 1-year (þ/e1 month) follow-up were associated with acceptable accuracy in identifying those who had an improved functional rating when preoperatively reporting a “severely abnormal,” abnormal,” and “nearly normal,” rating, respectively. These findings indicate that interpreting changes in score on the iHOT-12 from preoperatively to 1-year (þ/e1 month) follow-up is based not only on the magnitude of the change but also the patient’s preoperative self-rating function. Specifically, patients who consider their function more severely impaired required the least amount of change on the iHOT-12 to feel “improved,” Therefore, clinically meaningful changes specific to the patient’s baseline self-reported functional level before surgery may allow for more precise interpretation of score changes on the iHOT-12 after hip arthroscopy. The current study also provides information to help interpret the accuracy of the established SCB values based on the preoperative functional level. AUC defines the accuracy of the change in score on the iHOT-12 in identifying those who reached the criteria for SCB. A value of 1 for AUC would be associated with a cut-off score that is perfectly accurate, whereas 0.5 would be a cut-off of score that is no better than chance.13 The accuracy of the SCB values in predicting whether a patient has rated their function as improved were different depending on their preoperative self-rating of function. The SCB value of a change in score predicting improvement in those who had an initial “nearly normal” rating of function was not as accurate (AUC ¼ 0.73) compared with those who had a “severely abnormal” or “abnormal” rating of function preoperatively (AUC ¼ 0.89, 0.89). Therefore, surgeons may need to use additional indicators to confirm a patient’s status and complement the change in iHOT-12 scores to Table 3. Intraoperative Characteristics of Patients Undergoing Hip Arthroscopy Capsule treatment Release Closure Plication Not reported Capsulotomy type Interportal Extended interportal T-type Not reported Cartilage damage (Beck classification) Grade 1 Grade 2 Grade 3 Grade 4
N
Percent (%)
43 326 170 194
6% 44% 24% 26%
251 51 201 230
34% 7% 27% 32%
71 68 88 40
10% 9% 12% 5%
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SCB FOR IHOT-12 BASED ON LEVEL OF FUNCTION Table 4. Mean Preoperative iHOT-12 and 1-Year Postoperative Scores for Each Initial Rating of Function Initial Rating of Function Severely abnormal (N ¼ 123) Abnormal (N ¼ 451) Nearly normal (N ¼ 133)
Initial iHOT-12 20 (SD 12) 32 (SD 15) 49 (SD 16)
1-Year iHOT-12 64 (SD 29) 70 (SD 24) 76 (SD 21)
SCB Change Score for Improvement 22 28 27
SN/SP 0.79:1.0 0.82: 0.82 0.72: 0.63
AUC 0.89 (0.83-0.95) 0.89 (0.85-0.92) 0.73 (0.64-0.81)
AUC, area under the curve; iHOT-12, 12-item International Hip Outcome Tool; SCB, substantial clinical benefit; SD, standard deviation; SN, sensitivity; SP, specificity.
with the anchor-based question “How would you rate your overall physical ability?” and the response choices as follows: “no change,” “slightly worse,” “worse,” “slightly improved,” and “much improved.”5,16 These studies have found a change in iHOT-33 score in identifying those that were “unchanged” from “much improved” to be 24.5 points in patients who underwent hip arthroscopic surgery for femoroacetabular impingement16 and 25.2 points after revision hip arthroscopy.5 The SCB vales obtained in these studies are comparable with the change scores of 22, 28, 27 points on the iHOT-12 at 1 year (þ/e 1 month) that this current study found for those with “severely abnormal,” abnormal,” and “nearly normal” preoperative function, respectively. The potential benefit of this current study is that it establishes values to interpret changes in score of the iHOT-12 based preoperative level of function. Limitations There are a number of limitations that need to be acknowledged. First, one must consider that the follow-up
Sensivity
identify improvement in those with “nearly normal function” preoperatively. On the contrary, a surgeon can be more confident that the patient has an improved functional rating when preoperatively they note being “severely abnormal” or “abnormal” and have iHOT-12 change scores of 22 and 28 points, respectively. The relationship between functional status and responsiveness is an area of interest. Pre-operative Hip Outcome Score (HOS) scores have been found to be able to predict achieving MCID values at 1-year followup.10 Nwachukwu et al.10 found if subjects scored high on the HOS, >83.3 on the activities of daily living and >58.3 on sports subscales, they were less likely to achieve the HOS MCID with surgical treatment. Nwachukwu et al.10 findings would be consistent with this current study, as the accuracy of the change in iHOT-12 scores in predicting the achievement of the SCB criteria was lowest in subjects who reported being “nearly normal” on preoperative assessment. Therefore, a greater level of patient function preoperatively may reduce the ability of a change score to predict whether a patient has achieved a meaningful improvement or desired status with surgical intervention. Nwachukwu et al.10 also found that diagnosis influenced the likelihood of achieving MCID. Specifically, anterior acetabular under coverage, acetabular chondral defects, and relative femoral retroversion appear to be important factors in determining likelihood for achieving MCID values on PROMs. Therefore, an area of further study may be to see how responsiveness of PROM are influenced by both diagnosis and preoperative level of function. The smallest change in outcome that the patient is able to appreciate can be used to define MCID, whereas a change SCB score is a substantial or considerable improvement.3,4 These change scores differ from an absolute standalone score associated with PASS. Both versions of the iHOT, the shorter clinical iHOT-12 version and the parent iHOT-33, have been previously described related to their construction and psychometric properties8,9 and have established SBC values.5,16 At a mean of follow-up period of 352 (SD 21) days postsurgery in patients undergoing hip arthroscopy for intra-articular pathology, a change SCB score of 28 points on the iHOT-12 was able to identify those who improved their self-rating of function. At 1-year followup, the SCB values for the iHOT-33 were established
1-Specificity Improvement for Severly Abnormal at IE Improvement for Abnormal at IE Improvement for Nearly Normal at IE
Fig 1. Receiver operating characteristic curves for the iHOT-12 defining the accuracy in identifying a change score for improvement. (IE, initial evaluation; iHOT-12, 12-item International Hip Outcome Tool.)
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period was only 1 year. This limits the generalizability of the findings for patients with regards to their long-term functional outcome. Second, the postoperative rehabilitation following surgery was not identical for each surgeon or monitored for compliance. The quality of physical therapy after surgery can be an important factor in patient outcomes. Although all subjects were prescribed physical therapy with a relatively standard postoperative protocol after hip arthroscopy, the present study did not mandate adherence to a specific protocol, nor did it measure compliance of patients to postoperative rehabilitation. Thus, the results may be influenced by the quality of physical therapy received by the subject. This study is also limited to the anchor-based question and response for selfreported level of function used in this study. Other methods to determine SCB values may provide slightly different results. It may be of interest to determine a set cut-off score, or PASS score, that reflects the patient’s satisfaction of their level of function based on their preoperative status.6 A patient may have different tolerance for what is “acceptable” or “satisfactory” function compared with what is “normal” function. The purpose of this study was to establish an amount of change in the iHOT-12 in which the subject would consider their function to be “normal,” not just a “satisfactory,” and would represent the ultimate goal from which to judge a truly successful outcome.3,4 Future studies may look at absolute PASS score that would represent an “acceptable” outcome based on their preoperative status. Finally, only subjects with complete data sets were included, which could introduce bias and affect the results. There was less than 80% follow-up and a majority of subjects were female, which could possible introduce a bias. Related to sex bias, Nwachukwu et al.16 did not demonstrate that sex influences outcome.
Conclusions This study provides surgeons with unique SCB values for the iHOT-12 based on a preoperative rating function and may allow for a more precise interpretation of score changes. SCB values of 22, 28, and 27 points on the iHOT-12 at 1-year (þ/e1 month) follow-up identified those who had an improved function rating, when reporting a “severely abnormal,” abnormal,” and “nearly normal” on preoperative assessment, respectively.
References 1. Beaton DE, Bombardier C, Katz JN, Wright JG. A taxonomy for responsiveness. J Clin Epidemiol 2001;54: 1204-1217. 2. Martin RL, Kivlan BR, Christoforetti JJ, et al. Minimal clinically important difference and substantial clinical benefit values for the 12-Item International Hip Outcome Tool. Arthroscopy 2019;35:411-416.
3. Glassman SD, Copay AG, Berven SH, Polly DW, Subach BR, Carreon LY. Defining substantial clinical benefit following lumbar spine arthrodesis. J Bone Joint Surg Am 2008;90:1839-1847. 4. Katz NP, Paillard FC, Ekman E. Determining the clinical importance of treatment benefits for interventions for painful orthopedic conditions. J Orthop Surg Res 2015;10:24. 5. Nwachukwu BU, Chang B, Rotter BZ, Kelly BT, Ranawat AS, Nawabi DH. Minimal clinically important difference and substantial clinical benefit after revision hip arthroscopy. Arthroscopy 2018;34:1862-1868. 6. Kvien TK, Heiberg T, Hagen KB. Minimal clinically important improvement/difference (MCII/MCID) and patient acceptable symptom state (PASS): What do these concepts mean? Ann Rheum Dis 2007;66(suppl 3): iii40-41. 7. Harris JD, Brand JC, Cote MP, Faucett SC, Dhawan A. Research pearls: The significance of statistics and perils of pooling. part 1: clinical versus statistical significance. Arthroscopy 2017;33:1102-1112. 8. Mohtadi NG, Griffin DR, Pedersen ME, et al. The development and validation of a self-administered quality-oflife outcome measure for young, active patients with symptomatic hip disease: The International Hip Outcome Tool (iHOT-33). Arthroscopy 2012;28:595-610 e591. 9. Griffin DR, Parsons N, Mohtadi NG, Safran MR, Multicenter Arthroscopy of the Hip Outcomes Research Network. A short version of the International Hip Outcome Tool (iHOT-12) for use in routine clinical practice. Arthroscopy 2012;28:611-616. quiz 616-618. 10. Nwachukwu BU, Fields K, Chang B, Nawabi DH, Kelly BT, Ranawat AS. Preoperative outcome scores are predictive of achieving the minimal clinically important difference after arthroscopic treatment of femoroacetabular impingement. Am J Sports Med 2017;45: 612-619. 11. Beaton DE. Understanding the relevance of measured change through studies of responsiveness. Spine (Phila Pa 1976) 2000;25:3192-3199. 12. Lasko TA, Bhagwat JG, Zou KH, Ohno-Machado L. The use of receiver operating characteristic curves in biomedical informatics. J Biomed Inform 2005;38:404-415. 13. Park SH, Goo JM, Jo CH. Receiver operating characteristic (ROC) curve: Practical review for radiologists. Korean J Radiol 2004;5:11-18. 14. Berliner JL, Brodke DJ, Chan V, SooHoo NF, Bozic KJ. John Charnley Award: Preoperative patient-reported outcome measures predict clinically meaningful improvement in function after THA. Clin Orthop Relat Res 2016;474:321-329. 15. Schisterman EF, Perkins NJ, Liu A, Bondell H. Optimal cut-point and its corresponding Youden Index to discriminate individuals using pooled blood samples. Epidemiology 2005;16:73-81. 16. Nwachukwu BU, Chang B, Fields K, et al. Defining the "substantial clinical benefit" after arthroscopic treatment of femoroacetabular impingement. Am J Sports Med 2017;45:1297-1303.
Purpose: To define unique substantial clinical benefit (SCB) values for improvement on the 12-item International Hip Outcome Tool (iHOT-12) based on a preoperative self-rating of function in patients undergoing hip arthroscopy for intraarticular pathology. Methods: This was a retrospective review of prospective collected data on patients having hip arthroscopy for labral and chondral pathology and femoroacetabular impingement. On preoperative assessment and 1-year (þ/e1 month) follow-up, subjects completed the iHOT-12 and a self-categorical rating of function (“severely abnormal,” “abnormal,” “nearly normal,” or “normal”). Separate receiver operator characteristic analyses were performed for each preoperative categorical self-rating of function to determine unique SCB values for improvement-based changes in self-rating of function. Results: Of 1034 eligible patients, 733 (71%) subjects met the inclusion criteria. Subjects consisted of 537 (73%) female and 196 (27%) male subjects with a mean age of 35.3 years (standard deviation 13). At a mean of 352 (standard deviation 21) days postsurgery, changes in iHOT-12 scores of 22, 28, and 27 points were associated with acceptable accuracy in identifying those who had an improved function rating when reporting a “severely abnormal,” abnormal,” and “nearly normal” rating on preoperative assessment, respectively. The accuracy of these SCB values in predicting improvement was different depending on the patient’s preoperative rating of function. The accuracy of the SCB values in predicting improvement in those who had a “nearly normal” rating of function was not as accurate (area under the curve ¼ 0.73) compared with those who had a “severely abnormal” or “abnormal” rating of function on preoperative assessment (area under the curve ¼ 0.89; 0.89). Conclusions: This study provides surgeons with unique SCB values for the iHOT-12 based on a preoperative rating function and may allow for a more
From Rangos School of Health Sciences, Department of Physical Therapy, Duquesne University (R.L.M., B.R.K.), UPMC Center for Sports Medicine (R.L.M.), Allegheny-Singer Research Institute (J.J.C.), Pittsburgh, Pennsylvania; Texas Health Sports Medicine (J.J.C.), Allen, Texas; Hip Preservation and Sports Medicine, Washington Orthopaedics and Sports Medicine, Washington, DC (A.B.W.); Department of Orthopedic Surgery, Division of Sports Medicine, Hip Preservation Center, Rush University Medical Center, Chicago, Illinois (S.J.N.); Orthopaedic Surgery, The Sydney Kimmel Medical College at Thomas Jefferson University Hospital (J.P.S.) and Hip Arthroscopy Program, Rothman Institute (J.P.S.), Philadelphia, Pennsylvania; Orthopedic One, Ohio Orthopedic Surgery Institute, Dublin Methodist Hospital, Columbus, Ohio (T.J.E.); OrthoIllinois (G.V.T.), Rush University Medical Center (G.V.T.), US National Soccer Teams (G.V.T.), and Chicago Blackhawks Medical Network (G.V.T.), Chicago, Illinois; DISC Sports and Spine Center, Marina del Rey, California (D.M.); and Peachtree Orthopedics, Atlanta, Georgia (D.S.C.), U.S.A. The authors report the following potential conflicts of interest or sources of funding: D.M. reports editorial board membership, Orthopedics Today; paid consultant for Zimmer Biomet; and royalties for intellectual property from Smith & Nephew and Zimmer Biomet. J.J.C. reports board membership, International Society for Hip Arthroscopy; paid consultant for Arthrex;
royalties for Arthrex and Breg; employed physician at Allegheny Health Network; General Grant Funding Allegheny Singer Research Institute. A.B.W. reports paid consultant for Stryker. S.J.N. reports board membership, American Journal of Orthopedics; paid consultant for Stryker; and royalties from Ossur. J.P.S. reports paid consultant for Stryker. T.J.E. reports paid consultant for Biomet Sports Medicine; payment for lectures including service on speakers’ bureaus from Biomet Sports Medicine. D.S.C. reports board membership, the American Orthopaedic Foot and Ankle Society. G.V.T. reports consultancy for Smith & Nephew, Trainer Rx, Vericel, Zimmer; payment for lectures including service on speakers’ bureaus for Smith & Nephew, Zimmer; royalties from Zimmer; and stock/stock options from Trainer Rx. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Received July 5, 2018; accepted September 25, 2019. Address correspondence to RobRoy L. Martin, Ph.D., P.T., Rangos School of Health Sciences, Department of Physical Therapy, Duquesne University, Pittsburgh, PA. E-mail: [email protected] Ó 2019 by the Arthroscopy Association of North America 0749-8063/18812/$36.00 https://doi.org/10.1016/j.arthro.2019.09.046
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precise interpretation of score changes. SCB values of 22, 28, and 27 points on the iHOT-12 at 1-year (þ/e1 month) follow-up identified those who had an improved function rating, when reporting a “severely abnormal,” abnormal,” and “nearly normal” rating on preoperative assessment, respectively. Level of Evidence: III, retrospective comparative study
P
atient-reported outcome measures (PROMs) commonly are used to assess the success of surgery for patients undergoing hip arthroscopy. The information obtained from a PROM requires psychometric evidence to support its use, including information to interpret a change in score over time.1 Although there is evidence to support the use of PROMs in hip arthroscopy, including the 12-item International Hip Outcome Tool (iHOT-12),2 there is little known about how changes in score over time on a PROM may be affected by an individual’s functional status at preoperative assessment. The term responsiveness describes the ability of a PROM to detect a change in the patient’s status when a change has truly occurred.1 Responsiveness can objectively be defined with change in score values for minimal clinically important difference (MCID), patient acceptable symptom state (PASS), and substantial clinical benefit (SCB).3-7 The smallest change in outcome that the patient is able to appreciate can be used to define MCID, whereas a satisfactory or desired outcome status can be used to define PASS.6 SCB is considered the improvement in outcome or absolute postoperative health state that the patient considers to be a substantial or considerable improvement.3,4 MCID, PASS, and SCB are considered the lower, intermediate, and upper threshold for clinically significant outcome improvement, respectively.5 The MCID, PASS, and SCB values to define meaningful changes in score have been universally applied to patients without consideration for their preoperative level of function. It could be possible that a meaningful change in score on a PROM for someone with a low level of function on preoperative assessment could be different then a meaningful change in score for someone who is closer to normal preoperatively. In addition, the accuracy of these changes in score values also may be different based on an individual’s preoperative functional status. Responsiveness has been defined for commonly PROMs used in hip arthroscopy. This includes the iHOT-12, which was developed as a PROM appropriate to measure the impact of hip disease and effect of treatment in young, active individuals.2,8,9 Evidence to help interpret iHOT-12 scores at a follow-up time period at 1 year (þ/e 1 month) for patients undergoing hip arthroscopy for intra-articular pathology is available.2 Martin et al.2 found MCID values based on one-half the standard deviation (SD) of the change
scores and SCB based on an improvement in self-rating of function rating to be 13 and 28 points, respectively. Nwachukwu et al.10 noted a limitation in this type of study design is that SCB change scores may vary depending on the baseline level of function of the subjects. Defining unique values to interpret a change in score based on the patient’s preoperative level of function could allow for more precise interpretation of change in scores on a PROM in patients undergoing hip arthroscopy for intra-articular pathology. The purpose of this study was to define unique SCB values for improvement on the iHOT-12 based on a preoperative self-rating of function in patients undergoing hip arthroscopy for intra-articular pathology. It was hypothesized that unique values for SCB on the iHOT-12 could be identified based on preoperative rating of function.
Methods This was a retrospective review of prospectively collected data maintained in a secure electronic registry. The registry consisted of patients who consented to undergo hip arthroscopy at 1 of 7 centers within the United States. Inclusion criteria specific to this study included subjects who underwent primary surgery for labral and chondral pathology and femoroacetabular impingement between May 2014 and April 2017 with preoperative and follow-up iHOT-12 scores available. The follow-up data were collected 1-year (þ/e1 month) postsurgery. Patients were e-mailed and given a 2-month window around their 1-year surgery date (1 month before and 1 month after surgery) to complete PROMs. Exclusion criteria included those diagnosed with primary lumbopelvic pathology, advanced hip arthrosis (>Tönnis 2), primary slipped capital epiphysis or Perthes disease, or severe dysplasia (lateral center edge angle <16 ). Patients with relative contraindications to hip arthroscopy such as hip dysplasia (lateral center edge angle <25 ), acetabular index greater than 15 , high body mass index (>25), or age greater than 60 years were not excluded but handled on a case-by-case basis with the overseeing surgeon and the patient. An inability to read or understand English was also an exclusion criterion for the registry. The pre-hoc collection and storage of agreed-on clinical data points was granted according to individual institutional requirements and institutional
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SCB FOR IHOT-12 BASED ON LEVEL OF FUNCTION
review board approval granted to review the deidentified registry of patient data. Preoperatively, subjects were given the iHOT-12 and a categorical self-rating of function to complete. For follow-up data collection, subjects were emailed the iHOT-12 and self-rating of current function to complete between 335 and 395 days after surgery. Each item on the iHOT-12 was scored using a 100-mm horizontal line (visual analog scale) so that the mean of all questions amounts to the score result ranging from 0 to 100, with a greater score meaning better function, fewer symptoms, and greater quality of life.9 The self-rating of current level of function had categorical responses choices as follows: “severely abnormal,” “abnormal,” “nearly normal,” or “normal.” Demographic information was recorded from the electronic registry. Psychometric Analysis An anchor-based method was used to calculate SCB values. A SCB change score for improvement was calculated with receiver operator characteristic (ROC) analysis calculating the area under the curve (AUC) at a 95% confidence interval.11,12 A positive change in the categorical rating of function from preoperative assessment to 1-year (þ/e1 month) follow-up was used to identify patients for the “improved” group. Those who did not have a change or had a negative change in categorical rating of function were put in the “did not improve” group. These 2 groups were used to calculate SCB change score values for improvement based a “severely abnormal,” “abnormal,” “nearly normal” categorical ratings of function at preoperative assessment. The AUC for the ROC analysis is a combination of sensitivity and specificity and defines the accuracy of the iHOT-12 in distinguishing between groups.12,13 As noted in similar studies, an AUC >0.7 and a 95% confidence interval that does not contain 0.5 are considered properties of acceptable levels responsiveness while an AUC >0.8 is consider excellent.10,13,14 Youden’s Index was used to optimize sensitivity and specificity values and identify the best cutoff values for SCB that represent a score change most likely to be associated with being in the “improved” group at 1-year (þ/e1 month) follow-up for each categorical rating of function at preoperative assessment.15 Statistical analysis was performed using the SPSS software package (Version 24; SPSS Inc., Armonk, NY).
Results Participants Of 1034 eligible patients, 733 (71%) subjects met the inclusion criteria for this study and had 1-year (þ/e1 month) outcome data available for analysis. The reason for exclusion was not having 1-year follow-up data available. The average follow-up time was slightly less than 1 year, at 352 days (SD 21), as the
subjects had a 2-month window around their 1-year surgery date (1 month before and 1 month after surgery) to complete PROMs. At preoperative assessment, there were 123 (17%), 451 (62%), 133 (18%), and 26 (3%) subjects in the “severely abnormal,” “abnormal,” “nearly normal,” and “normal” groups, respectively, with 525 (72%) subjects improved and 208 (28%) not improved at follow-up. The average time between preoperative assessment and surgery was 58 days (SD 41). Preoperative characteristics of the subjects including age, sex, body mass index, hip joint morphology, and degenerative joint processes as determined by radiograph are presented in Table 1. A majority of subjects were female (73%) with morphological abnormalities to the femoral side of the hip joint without radiographic findings of significant degenerative joint disease (Tönnis grade 0 ¼ 88%). Table 2 describes the diagnoses and surgical procedures performed on the subjects. Labral pathology (97%) and femoroacetabular impingement (92%) were among the most common diagnoses arthroscopically treated. There were 577 (79%) subjects who had multiple procedures performed. The confounding diagnoses/procedures included ligamentum teres tear (10%), borderline hip dysplasia (9%), gluteus medius tear (2%), or a revision of a previous hip arthroscopy (7%). Labral repairs (64%) followed by femoroplasty (60%), synovectomy (56%), acetabuloplasty (40%), and acetabular chondroplasty (32%) were the among the most common arthroscopic procedures performed. The intraoperative arthroscopic examination demonstrated chondral damage to the hip joint in 236 (36%) subjects. The Beck Classification of Chondral damage for the cohort is reported in Table 3. Surgical treatment of the joint capsule is also reported in Table 3, which shows that a
Table 1. Preoperative Characteristics of the Subjects Who Underwent Hip Arthroscopy Age, y Body mass index LCEA Alpha angle Acetabular index
Mean 35 25.7 31 57 5
Sex Female Male Age <18 y Age >60 y Dysplasia LCEA <16 Tönnis grade 0 I LCEA, lateral center edge angle.
Standard Deviation 13 5.1 7 16 5
Range 11-73 17-51 16-60 38-120 e20-26
n
Percent (%)
537 196 60 23 14
73% 27% 8% 3% 2%
649 84
88% 12%
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Table 2. Arthroscopic Procedures and Diagnoses Labral treatment Debridement Repair Reconstruction Arthroscopic procedures Femoroplasty Synovectomy Acetabuloplasty Acetabular chondroplasty Femoral chondroplasty Acetabular microfracture Femoral microfracture Primary diagnoses Labral pathology Femoroacetabular impingement Concurrent diagnoses/procedures Ligamentum teres tear debridement Revision hip arthroscopy Gluteus medius repair Loose body removal Avascular necrosis Proximal hamstring repair Synovial chondromatosis Septic arthritis Pigmented villonodular synovitis
N
Percent (%)
182 471 62
25% 64% 8%
437 393 295 232 115 22 4
60% 56% 40% 32% 16% 3% 0.5%
715 677
97% 92%
70 54 18 5 3 2 1 1 0
10% 7% 2% 0.7% 0.4% 0.3% 0.1% 0.1% 0%
majority of patients received an interportal capsulotomy 251 (34%) with capsular closure 326 (44%). Psychometric Results The mean preoperative iHOT-12 and 1-year postoperative scores for each level of function are presented in Table 4. The results of the ROC analyses for SCB change score for improvement also are presented in Table 4 and Figure 1. Change scores of 22, 28, and 27 points on the iHOT-12 from preoperative assessment to 1-year (þ/e1 month) follow-up were associated with acceptable accuracy in identifying those who had an “improved” function rating from those that “did not improve” when reporting a “severely abnormal,” abnormal,” and “nearly normal” response at preoperative assessment, respectively. Depending on the patient’s preoperative level of function, the accuracy of these values in predicting whether a patient had reached the criteria for SCB was different. The accuracy of the SCB values in predicting improvement in those who had a “nearly normal” rating of function was not as accurate (AUC ¼ 0.73) compared with those who had a “severely abnormal” or “abnormal” rating of function at preoperative assessment (AUC ¼ 0.89, 0.89).
Discussion
The most important finding from this study was that iHOT-12 SCB values, which define whether a patient has improved their self-reported level of function at 1-year (þ/e1 month) follow-up, were relative and dependent on the patient’s preoperative self-rating of
function. The results of this study support the hypothesis as change score values of 22, 28, and 27 points on the iHOT-12 at 1-year (þ/e1 month) follow-up were associated with acceptable accuracy in identifying those who had an improved functional rating when preoperatively reporting a “severely abnormal,” abnormal,” and “nearly normal,” rating, respectively. These findings indicate that interpreting changes in score on the iHOT-12 from preoperatively to 1-year (þ/e1 month) follow-up is based not only on the magnitude of the change but also the patient’s preoperative self-rating function. Specifically, patients who consider their function more severely impaired required the least amount of change on the iHOT-12 to feel “improved,” Therefore, clinically meaningful changes specific to the patient’s baseline self-reported functional level before surgery may allow for more precise interpretation of score changes on the iHOT-12 after hip arthroscopy. The current study also provides information to help interpret the accuracy of the established SCB values based on the preoperative functional level. AUC defines the accuracy of the change in score on the iHOT-12 in identifying those who reached the criteria for SCB. A value of 1 for AUC would be associated with a cut-off score that is perfectly accurate, whereas 0.5 would be a cut-off of score that is no better than chance.13 The accuracy of the SCB values in predicting whether a patient has rated their function as improved were different depending on their preoperative self-rating of function. The SCB value of a change in score predicting improvement in those who had an initial “nearly normal” rating of function was not as accurate (AUC ¼ 0.73) compared with those who had a “severely abnormal” or “abnormal” rating of function preoperatively (AUC ¼ 0.89, 0.89). Therefore, surgeons may need to use additional indicators to confirm a patient’s status and complement the change in iHOT-12 scores to Table 3. Intraoperative Characteristics of Patients Undergoing Hip Arthroscopy Capsule treatment Release Closure Plication Not reported Capsulotomy type Interportal Extended interportal T-type Not reported Cartilage damage (Beck classification) Grade 1 Grade 2 Grade 3 Grade 4
N
Percent (%)
43 326 170 194
6% 44% 24% 26%
251 51 201 230
34% 7% 27% 32%
71 68 88 40
10% 9% 12% 5%
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SCB FOR IHOT-12 BASED ON LEVEL OF FUNCTION Table 4. Mean Preoperative iHOT-12 and 1-Year Postoperative Scores for Each Initial Rating of Function Initial Rating of Function Severely abnormal (N ¼ 123) Abnormal (N ¼ 451) Nearly normal (N ¼ 133)
Initial iHOT-12 20 (SD 12) 32 (SD 15) 49 (SD 16)
1-Year iHOT-12 64 (SD 29) 70 (SD 24) 76 (SD 21)
SCB Change Score for Improvement 22 28 27
SN/SP 0.79:1.0 0.82: 0.82 0.72: 0.63
AUC 0.89 (0.83-0.95) 0.89 (0.85-0.92) 0.73 (0.64-0.81)
AUC, area under the curve; iHOT-12, 12-item International Hip Outcome Tool; SCB, substantial clinical benefit; SD, standard deviation; SN, sensitivity; SP, specificity.
with the anchor-based question “How would you rate your overall physical ability?” and the response choices as follows: “no change,” “slightly worse,” “worse,” “slightly improved,” and “much improved.”5,16 These studies have found a change in iHOT-33 score in identifying those that were “unchanged” from “much improved” to be 24.5 points in patients who underwent hip arthroscopic surgery for femoroacetabular impingement16 and 25.2 points after revision hip arthroscopy.5 The SCB vales obtained in these studies are comparable with the change scores of 22, 28, 27 points on the iHOT-12 at 1 year (þ/e 1 month) that this current study found for those with “severely abnormal,” abnormal,” and “nearly normal” preoperative function, respectively. The potential benefit of this current study is that it establishes values to interpret changes in score of the iHOT-12 based preoperative level of function. Limitations There are a number of limitations that need to be acknowledged. First, one must consider that the follow-up
Sensivity
identify improvement in those with “nearly normal function” preoperatively. On the contrary, a surgeon can be more confident that the patient has an improved functional rating when preoperatively they note being “severely abnormal” or “abnormal” and have iHOT-12 change scores of 22 and 28 points, respectively. The relationship between functional status and responsiveness is an area of interest. Pre-operative Hip Outcome Score (HOS) scores have been found to be able to predict achieving MCID values at 1-year followup.10 Nwachukwu et al.10 found if subjects scored high on the HOS, >83.3 on the activities of daily living and >58.3 on sports subscales, they were less likely to achieve the HOS MCID with surgical treatment. Nwachukwu et al.10 findings would be consistent with this current study, as the accuracy of the change in iHOT-12 scores in predicting the achievement of the SCB criteria was lowest in subjects who reported being “nearly normal” on preoperative assessment. Therefore, a greater level of patient function preoperatively may reduce the ability of a change score to predict whether a patient has achieved a meaningful improvement or desired status with surgical intervention. Nwachukwu et al.10 also found that diagnosis influenced the likelihood of achieving MCID. Specifically, anterior acetabular under coverage, acetabular chondral defects, and relative femoral retroversion appear to be important factors in determining likelihood for achieving MCID values on PROMs. Therefore, an area of further study may be to see how responsiveness of PROM are influenced by both diagnosis and preoperative level of function. The smallest change in outcome that the patient is able to appreciate can be used to define MCID, whereas a change SCB score is a substantial or considerable improvement.3,4 These change scores differ from an absolute standalone score associated with PASS. Both versions of the iHOT, the shorter clinical iHOT-12 version and the parent iHOT-33, have been previously described related to their construction and psychometric properties8,9 and have established SBC values.5,16 At a mean of follow-up period of 352 (SD 21) days postsurgery in patients undergoing hip arthroscopy for intra-articular pathology, a change SCB score of 28 points on the iHOT-12 was able to identify those who improved their self-rating of function. At 1-year followup, the SCB values for the iHOT-33 were established
1-Specificity Improvement for Severly Abnormal at IE Improvement for Abnormal at IE Improvement for Nearly Normal at IE
Fig 1. Receiver operating characteristic curves for the iHOT-12 defining the accuracy in identifying a change score for improvement. (IE, initial evaluation; iHOT-12, 12-item International Hip Outcome Tool.)
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period was only 1 year. This limits the generalizability of the findings for patients with regards to their long-term functional outcome. Second, the postoperative rehabilitation following surgery was not identical for each surgeon or monitored for compliance. The quality of physical therapy after surgery can be an important factor in patient outcomes. Although all subjects were prescribed physical therapy with a relatively standard postoperative protocol after hip arthroscopy, the present study did not mandate adherence to a specific protocol, nor did it measure compliance of patients to postoperative rehabilitation. Thus, the results may be influenced by the quality of physical therapy received by the subject. This study is also limited to the anchor-based question and response for selfreported level of function used in this study. Other methods to determine SCB values may provide slightly different results. It may be of interest to determine a set cut-off score, or PASS score, that reflects the patient’s satisfaction of their level of function based on their preoperative status.6 A patient may have different tolerance for what is “acceptable” or “satisfactory” function compared with what is “normal” function. The purpose of this study was to establish an amount of change in the iHOT-12 in which the subject would consider their function to be “normal,” not just a “satisfactory,” and would represent the ultimate goal from which to judge a truly successful outcome.3,4 Future studies may look at absolute PASS score that would represent an “acceptable” outcome based on their preoperative status. Finally, only subjects with complete data sets were included, which could introduce bias and affect the results. There was less than 80% follow-up and a majority of subjects were female, which could possible introduce a bias. Related to sex bias, Nwachukwu et al.16 did not demonstrate that sex influences outcome.
Conclusions This study provides surgeons with unique SCB values for the iHOT-12 based on a preoperative rating function and may allow for a more precise interpretation of score changes. SCB values of 22, 28, and 27 points on the iHOT-12 at 1-year (þ/e1 month) follow-up identified those who had an improved function rating, when reporting a “severely abnormal,” abnormal,” and “nearly normal” on preoperative assessment, respectively.
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3. Glassman SD, Copay AG, Berven SH, Polly DW, Subach BR, Carreon LY. Defining substantial clinical benefit following lumbar spine arthrodesis. J Bone Joint Surg Am 2008;90:1839-1847. 4. Katz NP, Paillard FC, Ekman E. Determining the clinical importance of treatment benefits for interventions for painful orthopedic conditions. J Orthop Surg Res 2015;10:24. 5. Nwachukwu BU, Chang B, Rotter BZ, Kelly BT, Ranawat AS, Nawabi DH. Minimal clinically important difference and substantial clinical benefit after revision hip arthroscopy. Arthroscopy 2018;34:1862-1868. 6. Kvien TK, Heiberg T, Hagen KB. Minimal clinically important improvement/difference (MCII/MCID) and patient acceptable symptom state (PASS): What do these concepts mean? Ann Rheum Dis 2007;66(suppl 3): iii40-41. 7. Harris JD, Brand JC, Cote MP, Faucett SC, Dhawan A. Research pearls: The significance of statistics and perils of pooling. part 1: clinical versus statistical significance. Arthroscopy 2017;33:1102-1112. 8. Mohtadi NG, Griffin DR, Pedersen ME, et al. The development and validation of a self-administered quality-oflife outcome measure for young, active patients with symptomatic hip disease: The International Hip Outcome Tool (iHOT-33). Arthroscopy 2012;28:595-610 e591. 9. Griffin DR, Parsons N, Mohtadi NG, Safran MR, Multicenter Arthroscopy of the Hip Outcomes Research Network. A short version of the International Hip Outcome Tool (iHOT-12) for use in routine clinical practice. Arthroscopy 2012;28:611-616. quiz 616-618. 10. Nwachukwu BU, Fields K, Chang B, Nawabi DH, Kelly BT, Ranawat AS. Preoperative outcome scores are predictive of achieving the minimal clinically important difference after arthroscopic treatment of femoroacetabular impingement. Am J Sports Med 2017;45: 612-619. 11. Beaton DE. Understanding the relevance of measured change through studies of responsiveness. Spine (Phila Pa 1976) 2000;25:3192-3199. 12. Lasko TA, Bhagwat JG, Zou KH, Ohno-Machado L. The use of receiver operating characteristic curves in biomedical informatics. J Biomed Inform 2005;38:404-415. 13. Park SH, Goo JM, Jo CH. Receiver operating characteristic (ROC) curve: Practical review for radiologists. Korean J Radiol 2004;5:11-18. 14. Berliner JL, Brodke DJ, Chan V, SooHoo NF, Bozic KJ. John Charnley Award: Preoperative patient-reported outcome measures predict clinically meaningful improvement in function after THA. Clin Orthop Relat Res 2016;474:321-329. 15. Schisterman EF, Perkins NJ, Liu A, Bondell H. Optimal cut-point and its corresponding Youden Index to discriminate individuals using pooled blood samples. Epidemiology 2005;16:73-81. 16. Nwachukwu BU, Chang B, Fields K, et al. Defining the "substantial clinical benefit" after arthroscopic treatment of femoroacetabular impingement. Am J Sports Med 2017;45:1297-1303.