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Preoperative Predictors of Achieving Clinically Significant Athletic Functional Status After Hip Arthroscopy for Femoroacetabular Impingement at Minimum 2-Year Follow-Up
Address correspondence to Shane J. Nho, M.D., M.S., Department of Orthopaedic Surgery, Rush University Medical Center, 1611 W. Harrison St., Suite 300, Chicago, IL 60612, U.S.A.
To identify predictors of achieving clinically significant sport function in athletic patients undergoing hip arthroscopy for femoroacetabular impingement syndrome (FAIS).
Methods
Data were analyzed for all patients who treated for FAIS between 2012 to 2016 and reported being athletes, including recreational and competitive athletes. All patients had a minimum of 2-year follow-up with patient-reported athletic function in the form of the Hip Outcome Score–Sport Specific (HOS-SS), visual analog score–pain, and patient satisfaction. Achieving clinically significant sports function was defined as either reaching the minimally clinical important difference (MCID) or the patient acceptable symptomatic state (PASS) for HOS-SS at 2-year follow-up. An exploratory factor analysis was used to determine specific domains for the predictor variables and to reduce the redundancy in these variables. A ogistic regression analysis was used to identify significant predictors of achieving clinically significant sports function.
Results
Of 780 qualifying patients, 626 completed the 2-year minimum follow-up (80%), with a mean age and body mass index of 31.6 ± 11.9 years and 24.6 ± 8.6, respectively. A total of 500 patients (86.5%) achieved high functional status, with 77.9% achieving MCID HOS-SS and 68.7% achieving PASS HOS-SS. Logistic regression analysis identified increased the α angle (odds ratio [OR] 0.976; P = .027), preoperative pain duration (OR 0.729; P = .011), and body mass index (BMI) (OR 0.919; P = .018), as well as the presence of femoral chondral defects (OR 0.769; P = .013), as negative predictors for achieving MCID. Negative predictors for achieving PASS HOS-SS included the presence of a preoperative limp (OR 0.384; P = .013), anxiety or depression (OR 0.561; P = .041), and increased BMI (OR 0.945; P = .018) and preoperative pain duration (OR 0.987; P < .001).
Conclusions
Several predictors of achieving clinically significant sport function performance exist, including a history of anxiety or depression, BMI, preoperative α angle, limp, femoral chondral damage, *and preoperative symptom duration. Our results suggest there are both modifiable and nonmodifiable preoperative factors that have the potential to predict achieving high athletic function after hip arthroscopy for FAIS.
Level of Evidence
IV, Case Series.
Introduction
Hip arthroscopy is widely used to treat femoroacetabular impingement syndrome (FAIS).
These studies evaluated a broad range of sporting activities for both professional and recreational athletes. Additional factors influencing return to sport include the sport type, level of competition, and severity of the intra-articular hip damage.
This information demonstrates that a multitude of factors contribute to patient outcomes and return to sport, which also highlights the complexity in predicting these outcomes. Therefore, a detailed understanding of the predictors of both superior and inferior outcomes of athletic function after arthroscopic surgery for FAIS is imperative for treating surgeons. This information will help guide surgeons and patients in choosing the optimal treatment algorithm.
identified that mental health, activity level, sex, and smoking predict greater baseline pain and decreased baseline function before hip arthroscopy; however, the authors did not evaluate the efficacy of the intervention or predictors of postoperative pain and function. Furthermore, as with other previous studies, the authors did not identify preoperative variables predictive of achieving high sports-specific functional status after undergoing hip arthroscopy for FAIS in athletic patients. As such, the purpose of this study was to identify predictors of achieving clinically significant sport function in athletic patients undergoing hip arthroscopy for FAIS. An advanced understanding of factors that may influence postoperative outcomes and functional status would provide vital information for clinical decision-making for the treatment of athletic patients with FAIS across a large spectrum of athletic involvement. We hypothesized that both modifiable (i.e., age, body mass index [BMI], mental status, etc.) and nonmodifiable (α angle, Tonnis grade, pain duration, chondral damage, etc.) preoperative factors will predict achieving high functioning status in patients who undergo hip arthroscopy at a minimum of 2-year follow-up regardless of their athletic level.
Methods
Study Design
After approval from our institutional review board, patients who were scheduled to undergo hip arthroscopy were enrolled in a database repository. A retrospective analysis was performed on a single surgeon's database, which was collected from January 2012 through June 2016. Inclusion criteria were undergoing hip arthroscopy for FAIS, self-reporting as an athlete (recreational, high school, college, or professional), and a minimum of 2-year follow up. Exclusion criteria included not being an athlete, a medical history of ipsilateral or contralateral hip surgery, advanced osteoarthritis, reduced joint space (Tonnis grade >1), or evidence of congenital hip disorders [e.g., slipped capital femoral epiphysis, developmental dysplasia of the hip (lateral center-edge angle <20°),
and had failure of conservative, nonoperative treatment including the use of nonsteroid anti-inflammatory treatment, corticosteroid injections, and physical therapy.
Every surgical candidate who volunteered to be entered into the database received a preoperative clinical assessment that was made with the use of the Hip Outcome Score–Sport Specific (HOS-SS) and an assessment of preoperative pain by use of a visual analog scale (VAS-pain) via electronic tablet and was stored in an encrypted data collection system (Oberd, Columbia, MO). Patient demographics, including age, BMI, sex, and physical activity level, as well as pertinent medical history (e.g., pain duration, history of back pain, and history of mental disorders), were gathered electronically at the time of surgical clearance. Medical history was confirmed from the electronic medical record if the patient was seen previously at our institution. After the surgery, patient-reported outcomes (PROs) were evaluated by using the same surveys, in addition to satisfaction, which was assessed by using VAS-satisfaction, and were all administered electronically at a minimum of 24 months.
High Versus Low Function After Hip Arthroscopy
To assess the outcome of patients involved in sports, clinically significant sport function was determined by reaching the minimally clinical important difference (MCID), patient acceptable symptomatic state (PASS) for the Hip Outcome Score–Sports Subscale (HOS-SS) at 2-year follow-up. Although previous studies have described the MCID and PASS scores for patients undergoing hip arthroscopy for FAIS, every study population is unique and therefore both scores should be calculated to concisely represent the group being analyzed. In same manner as described previously in the literature, MCID for HOS-SS was determined by calculating the half–standard deviation (SD) of the HOS-SS average in the study patients.
Preoperative outcome scores are predictive of achieving the minimal clinically important difference after arthroscopic treatment of femoroacetabular impingement.
The MCID was calculated to be 14.1. Any patient with an average improvement in 2-year HOS-SS score from baseline of <14.1 was considered to not be achieving a minimal threshold of meaningful athletic functional status. However, patients with an average improvement of ≥14.1 were considered to be achieving a minimal threshold of achieving meaningful athletic functional status.
PASS was calculated by using an anchor-based method. At 2-year follow-up, patients were asked the following anchor question: “Taking into account all the activities you have during your daily life, your level of pain, and also your functional impairment, do you consider that your current state is satisfactory?” The 2-year PASS value was then identified by using an receiver operating characteristic (ROC) curve analysis as previously done in prior studies (analysis provided in Appendix 1).
Preoperative outcome scores are predictive of achieving the minimal clinically important difference after arthroscopic treatment of femoroacetabular impingement.
The patient acceptable symptomatic state for the Modified Harris Hip Score and Hip Outcome Score among patients undergoing surgical treatment for femoroacetabular impingement.
A sensitivity and specificity of 0.80 was used as the cut-off for determining an acceptable HOS-SS PASS score. Patients were classified as achieving PASS if PASS was achieved on any of the included outcome measures. The score necessary for achieving PASS HOS-SS was calculated to be 72.1. Any patient with a 2-year HOS-SS score of <72.1 was considered to not be achieving a high threshold of meaningful athletic functional status, whereas patients with a score of ≥72.1 were considered to be achieving a high threshold of meaningful athletic functional status.
Surgical Technique
Patients underwent hip arthroscopy for the treatment of FAIS in the supine position as previously described.
Improved outcomes after hip arthroscopic surgery in patients undergoing T-capsulotomy with complete repair versus partial repair for femoroacetabular impingement: A comparative matched-pair analysis.
All operations were performed with the patient in the supine position on a standard traction table under general anesthesia. Anterolateral (AL), mid-anterior, and distal anterolateral accessory (DALA) portals were created to address the central compartment pathology, and a T-capsulotomy was performed for visualization of the peripheral compartment. Labral refixation was performed in all cases amenable to repair. Hip traction was released immediately after work was concluded in the central compartment, and the peripheral compartment was addressed after a dynamic examination to identify the zones of the impingement.
Once the arthroscopic procedure was complete, a complete capsular closure was performed to restore biomechanical properties of the IFL. The vertical limb of the T-capsulotomy was closed with 2 to 4 side-to-side sutures, and the interportal capsulotomy limb was closed with 2 or 3 sutures. Capsular closure began with the distal portion of the vertical limb at the base of the iliofemoral ligament (IFL). A crescent tissue penetrating device (Slingshot; Stryker Sports Medicine) was loaded with high-strength No. 2 suture (Zipline; Stryker Sports Medicine) and placed through the AL portal to sharply pierce the lateral leaflet of the IFL approximately 6 mm from the edge. The No. 2 suture was then shuttled into the intra-articular side of the capsule. Through the DALA portal, the penetrating device was then used to pierce the medial leaflet approximately 3 mm from the edge to retrieve the free suture. Next, the looped suture retriever was used to pull the suture from the AL portal to the DALA portal so the suture can be tied. The authors prefer to tie each suture individually after it is passed, but all of the sutures can be passed first and then tied. Because successive suture placement and knot tying inherently tighten the capsule, successive visualization requires more precision. Each subsequent suture is similarly passed, about 1 cm proximal to the previous stitch. Most patients were closed via plication, with the lateral leaflet bite titrated 0 to 3 mm depending on the capsular laxity.
After closure of the vertical limb of the T-capsulotomy, the authors prefer to close the interportal capsulotomy with the InJector II Capsule Restoration System (Stryker Sports Medicine), a device that allows for closure through a single cannula lateral to medial. This device was passed through the AL cannula to bring the suture end through the proximal IFL attached to the acetabulum. The device was removed from the cannula, and the other suture end is placed in the device and passed through the distal IFL. The stitch was then tensioned and tied. Likewise, closure of the medial IFL involved passing the InJector through the DALA cannula and bringing the first suture end through the proximal IFL attached to the acetabulum. The Injector was then removed from the cannula, and the other suture end was placed in the device and passed through the distal IFL. The stitch was then tensioned and tied with the hip in neutral extension. Depending on the length of the incision and integrity of the capsule, 2 or 3 stitches are used to close the interportal capsulotomy. Complete capsular closure was confirmed by the inability to visualize the underlying femoral head/neck and by probing the anterior capsule to ensure proper tension.
Postoperative Rehabilitation Process
All patients followed the standard rehabilitation protocol previously as described.
A four-phase physical therapy regimen for returning athletes to sport following hip arthroscopy for femoroacetabular impingement with routine capsular closure.
After surgery, all patients went through the same 4-phase rehabilitation protocol that lasted 24 to 32 weeks. Patients ambulated with the aid of bilateral crutches for a minimum of 3 weeks with a 20-lb, foot flat weightbearing restriction. Hip orthosis was used to prevent active abduction, hip flexion beyond 90°, extension beyond neutral, and external rotation. Daily passive motion and soft tissue mobilization with supervised physical therapy started on postoperative day 1. At 3 weeks, closed chain exercises were initiated, and patients progressed to weightbearing as tolerated without crutches or a brace. At 12 weeks, patients progressed to straight line rotational control, agility, and plyometric exercises.
Therapy specific to a return to sport protocol included certain precautions for the first 6 weeks, including avoidance of the extremes of range of motion in all planes to protect the capsular plication and repaired labrum, as well as to prevent secondary injury to tight or weak muscular tissue structures. Patients were subsequently introduced to cycling exercises progressed using an upright stationary elliptical machine. Patients progressed with single leg stance balance activities, eccentric and concentric core and lower extremity strength training, advanced core activation and proximal control, and femoroacetabular and acetabulofemoral rotational control and strength. The clinician assessed the patient's ability to progress with minimal pain, good proximal control with exercises and functional activities, and absent compensatory gait pattern, with a goal of clearing patients for return to sport by 24 weeks.
Statistical Analysis
All data were screened to determine if they met all parametric statistical assumptions before analysis. Two binary logistic regression models were created: one for achieving MCID and another for achieving PASS. The process of creating the models is summarized in Figure 1. Pearson and Spearman covariate analyses were carried out to identify correlations between MCID and PASS HOS-SS, versus preoperative, intraoperative, and postoperative variables, to identify variables to fit in the exploratory analysis for the final logistic models. An exploratory factor analysis was performed on the variables with statistically significant correlations to the primary outcomes (achieving MCID or PASS HOS-SS) by using a principal component (PC) extraction with a varimax rotation to reduce the redundancy in the predictor variables. A Kaiser-Meyer-Olkin test value of 0.7 was found, which demonstrates the data were appropriate for factor analysis as this value exceeded a recommended value of 0.6 for exploratory factor analysis.
A scree plot was examined to determine the number of PCs to retain for analysis. Each extracted PC was used to calculate the percent variance explained (%VAF) by dividing the eigenvalue of each PC by the sum of all eigenvalues. The contribution of each variable to the PC was determined by using the factor loadings of each variable. Variables that demonstrated a factor loading of >±0.25 for a PC was retained as a predictor variable for the follow-up binary logistic regression analysis used to predict a high-versus low-functioning 2-year postoperative PRO outcome scores. An ROC curve analysis was then used to identify the model with the best fit and, therefore, the variables with the best fit for the model. The final regression models for MCID and PASS were chosen based on the highest area under the curve (AUC) in the ROC curve analysis.
Fig 1Binary logistic regression models for achieving minimally clinical important difference (MCID) or the patient acceptable symptomatic state (PASS).
Descriptive statistics for all continuous variables are reported as mean and SD values, and frequency statistics were reported for all noncontinuous variables. Paired-sample t tests were used to compare preoperative and 2-year postoperative PROs in patients with FAIS. One-way analysis of variance was used to compare 2-year postoperative PROs stratified by athlete type (recreational, high school, college, professional). Statistical significance for all analysis was set at an á ≤ .05.
Results
Patient Demographics
Of the 780 qualifying patients, 626 completed the 2-year minimum follow-up (80%); mean (±SD) age and body mass index (BMI) were 31.5 (11.9) years and 24.6 (8.6), respectively (Table 1). The majority of patients were female (n = 437, 69.8%) and nonsmokers (n = 570, 91.1%), and 187 patients (29.9%) experienced preoperative symptoms for longer than 2 years. The majority of patients in the study group were recreational athletes (74.1%), followed by high school (9.6%), college (7.5%), and professional (1.6%) athletes.
Table 1Patient Demographics
Total/Mean
Female, n
437 (69.8%)
Age, yr
31.6 ± 11.9
Body mass index
24.6 ± 8.6
History of back pain, n
74 (11.8%)
History of anxiety or depression, n
79 (12.6%)
Psychiatric history
80 (12.8%)
Chronic pain preoperatively (>2 yr)
187 (29.9%)
Average length of preoperative pain, mo
23.2 ± 33.1
Running for regular exercise (yes)
481 (76.8%)
Limp when walking
37 (5.9%)
History of hip injections
363 (57.9%)
Level of athletic performance
Recreational
464 (74.1%)
High school
60 (9.6%)
College
47 (7.5%)
Professional
10 (1.6%)
NOTE. Values given as n (%) except where otherwise indicated.
There was a statistically significant improvement in the HOS-SS score average after surgery (43.9 ± 22.0 to 77.9 ± 23.5; P < .001). In addition, VAS-pain was significantly decreased from 66.1 ± 20.29 to 4.5 ± 9.1 (P < .001) with a high satisfaction score average of 84.4 ± 20.5 at 2-year minimum follow-up (Table 2). Subanalysis by athletic type (recreational, high school, college, professional) demonstrated a statistically significant difference when comparing 2-year HOS-SS score average values (Table 3). However, there was no difference in overall change (Δ) in HOS-SS and VAS-pain between athletic performance. A total of 500 patients (86.9%) achieved high functional status (achieved either PASS, MCID, or both), with 77.9% achieving MCID HOS-SS and 68.7% achieving PASS HOS-SS (Table 4).
Δ, Change in reported outcomes over average 2-year time period; HOS-SS, Hip Outcome Score–Sport Subscale; SD, standard deviation; VAS, visual analog scale.
NOTE. Values given as n (%) except where otherwise indicated.
High functional status, achieved either PASS, MCID, or both; HOS-SS, Hip Outcome Score–Sport Subscale; MCID, minimal clinically important difference; PASS, patient acceptable symptomatic state.
The factor analysis for achieving high functional status consisted of 9 PCs that explained 62.3% of the variance of the predictor variables. The variables retained for analysis were based on the PC loadings, and those that were statistically significant in the MCID and PASS regression models are reported in Tables 5 and 6, respectively. Preoperative predictors of achieving a minimal threshold of meaningful clinical outcome based on MCID include smaller α angle (odds ratio [OR] 0.976, 95% confidence interval [CI] 0.956-0.997; P = .027), absence of femoral chondral defects (OR 0.769, CI 0.625-0.946; P = .013), shorter preoperative pain duration (OR 0.729, CI 0.571-0.931; P = .011), and lower BMI (OR 0.919, CI 0.865-0.977; P = .018). The regression model had an appropriate fit based on the ROC curve analysis (AUC 0.691) (Appendix 2). Preoperative predictors of achieving a higher threshold of meaningful clinical outcome based on PASS include absence of limp (OR 0.384, CI 0.18-0.818; P = .013), absence of anxiety or depression (OR 0.561, CI 0.322-0.975; P = .041), lower BMI (OR 0.945, CI 0.903-0.99; P = .018), and shorter preoperative pain duration (OR 0.987, CI 0.981-0.994; P < .001). The regression model had an appropriate fit based on the ROC curve analysis (AUC 0.700) (Appendix 3).
Table 5Binary Logistic Regression Model for MCID HOS-SS
Odds Ratio
95% CI
P
Lower Bound
Upper Bound
Preoperative α angle (AP)
0.976
0.956
0.997
.027
Femoral chondral defects
0.769
0.625
0.946
.013
Preoperative pain duration (in months)
0.729
0.571
0.931
.011
BMI
0.919
0.865
0.977
.007
AP, anteroposterior; BMI, body mass index; CI, confidence interval; MCID, minimal clinically important difference; PASS, patient acceptable symptomatic state.
The primary finding in this study was that the absence of mental health disease, lower BMI, and shorter preoperative pain duration were positive predictors of achieving MCID after hip arthroscopy for FAIS in patients who participate in sports. Furthermore, physical findings such as limp while ambulating and intraoperative findings including femoral chondral defects were negative predictors of achieving PASS in the same study population. Last, there was a statistically significant improvement in sports function score averages, regardless of sports performance level. The current study adds to the literature in that it derived MCID and PASS for the patient study population as opposed to what has been previously published; it has twice the study population as current 2-year outcome studies; it defines clinical high functional status; and it provides ROC curve and factor analysis for creating predictor models.
Psychological distress and mental health disease are increasingly recognized as significant influences on pain and function associated with orthopedic conditions.
Mental health has a stronger association with patient-reported shoulder pain and function than tear size in patients with full-thickness rotator cuff tears.
Preoperative Short Form Health Survey Score is predictive of return to play and minimal clinically important difference at a minimum 2-year follow-up after anterior cruciate ligament reconstruction.
In a previous study, preoperative predictors of increased baseline (preoperative) pain and decreased baseline function included mental health, activity level, sex, and smoking.
Therefore, when the current findings are considered in the context of these previous studies, it is not surprising that the absence of mental health disease, shorter durations of preoperative symptoms, and no preoperative narcotic use all predicted patients who were high functioning after surgery. Each of these predictors likely evaluates factors associated with a patient's pain behavior before surgery; therefore, it is also not surprising that these factors all seem to represent this domain.
The multifactorial nature of clinically significant sport function outcomes can be further emphasized by looking at return to sport after hip arthroscopy. Athletes are generally highly motivated and demonstrate a high rate of return to sport after hip arthroscopy sport (reported to be 88% to 96%).
However, in a cohort of recreational and competitive runners, BMI was associated with the rate of return to running and postoperative HOS-SS scores, which is consistent with the observations of the current study that BMI is predictive of achieving MCID and PASS in patients who participate in all sports.
Limitations
Our study carries common limitations associated with retrospective cohort analysis. First, we analyzed all consecutive patients treated by the senior author during a defined period, which may not be generalizable to a wider patient cohort. Second, the predictive models for inferior clinical outcomes and clinical failures demonstrated an appropriate fit based on the ROC curve analysis; however, it is possible that better models exist. A number of different models were analyzed by using the variables in the factor analysis, but it is possible that confounders and other nonlinear associations exist between the primary outcomes and other variables not tested. Third, we did not stratify the MCID/PASS analysis by sports performance type, because the number of professional athletes was low and likely would have been underpowered. Additionally, return to sports information was not specifically recorded, so it is possible that patients reported a high athletic functional score regardless of return to competition. Finally, all patients in the current study were operated on by a single, fellowship-trained surgeon at a single institution, which limits the external validity of the study.
Conclusions
Several predictors of achieving clinically significant sport function performance exist, including a history of anxiety or depression, BMI, preoperative α angle, limp, femoral chondral damage, and preoperative symptom duration. Our results suggest that there are both modifiable and nonmodifiable preoperative factors that have the potential to predict achievement of high athletic function after hip arthroscopy for FAIS.
Appendix 1. ROC Curve Analysis for Determining HOS-SS Score for PASS
Appendix 2. ROC Curve Analysis for MCID HOS-SS Logistic Regression Model
Appendix 3. ROC Curve Analysis for PASS HOS-SS Logistic Regression Model
Preoperative outcome scores are predictive of achieving the minimal clinically important difference after arthroscopic treatment of femoroacetabular impingement.
The patient acceptable symptomatic state for the Modified Harris Hip Score and Hip Outcome Score among patients undergoing surgical treatment for femoroacetabular impingement.
Improved outcomes after hip arthroscopic surgery in patients undergoing T-capsulotomy with complete repair versus partial repair for femoroacetabular impingement: A comparative matched-pair analysis.
A four-phase physical therapy regimen for returning athletes to sport following hip arthroscopy for femoroacetabular impingement with routine capsular closure.
Mental health has a stronger association with patient-reported shoulder pain and function than tear size in patients with full-thickness rotator cuff tears.
Preoperative Short Form Health Survey Score is predictive of return to play and minimal clinically important difference at a minimum 2-year follow-up after anterior cruciate ligament reconstruction.
The authors report that they have no conflicts of interest in the authorship and publication of this article and that no funding or financial remuneration was received. Full ICMJE author disclosure forms are available for this article online, as supplementary material.
In the article titled “Preoperative Predictors of Achieving Clinically Significant Athletic Functional Status After Hip Arthroscopy for Femoroacetabular Impingement at Minimum 2-Year Follow-Up,” published in the November 2019 issue (Arthroscopy 2019;35:3049-3056), there was a typographical error displayed in the Abstract Methods, due to publisher error. In the following sentence, the letter “l” was omitted from the word “logistic”: “A logistic regression analysis was used to identify significant predictors of achieving clinically significant sports function.” The publisher apologizes for any inconvenience caused.
Hip pain in the young athletic population is often caused by femoroacetabular impingement morphology. If a patient fails conservative management, hip arthroscopy becomes a potential treatment option. Our ability to maximize patient outcomes after hip arthroscopy is directly related to preoperative patient selection, intraoperative technical ability, and attention to detail in the postoperative period. When considering surgery as a therapeutic option, we want to first identify that the pain is truly stemming from the hip.
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