Association Between Preoperative Patient Factors and Clinically Meaningful Outcomes After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Machine Learning Analysis

Background: The International Hip Outcome Tool 12-Item Questionnaire (IHOT-12) has been proposed as a more appropriate outcome assessment for hip arthroscopy populations. The extent to which preoperative patient factors predict achieving clinically meaningful outcomes among patients undergoing hip arthroscopy for femoroacetabular impingement syndrome (FAIS) remains poorly understood. Purpose: To determine the predictive relationship of preoperative imaging, patient-reported outcome measures, and patient demographics with achievement of the minimal clinically important difference (MCID), Patient Acceptable Symptom State (PASS), and substantial clinical benefit (SCB) for the IHOT-12 at a minimum of 2 years postoperatively. Study Design: Case-control study; Level of evidence, 3. Methods: Data were analyzed for consecutive patients who underwent hip arthroscopy for FAIS between 2012 and 2018 and completed the IHOT-12 preoperatively and at a minimum of 2 years postoperatively. Fifteen novel machine learning algorithms were developed using 47 potential demographic, clinical, and radiographic predictors. Model performance was evaluated with discrimination, calibration, decision-curve analysis and the brier score. Results: A total of 859 patients were identified, with 685 (79.7%) achieving the MCID, 535 (62.3%) achieving the PASS, and 498 (58.0%) achieving the SCB. For predicting the MCID, discrimination for the best-performing models ranged from fair to excellent (area under the curve [AUC], 0.69-0.89), although calibration was excellent (calibration intercept and slopes: –0.06 to 0.02 and 0.24 to 0.85, respectively). For predicting the PASS, discrimination for the best-performing models ranged from fair to excellent (AUC, 0.63-0.81), with excellent calibration (calibration intercept and slopes: 0.03-0.18 and 0.52-0.90, respectively). For predicting the SCB, discrimination for the best-performing models ranged from fair to good (AUC, 0.61-0.77), with excellent calibration (calibration intercept and slopes: –0.08 to 0.00 and 0.56 to 1.02, respectively). Thematic predictors for failing to achieve the MCID, PASS, and SCB were presence of back pain, anxiety/depression, chronic symptom duration, preoperative hip injections, and increasing body mass index (BMI). Specifically, thresholds associated with lower likelihood to achieve a clinically meaningful outcome were preoperative Hip Outcome Score–Activities of Daily Living <55, preoperative Hip Outcome Score–Sports Subscale >55.6, preoperative IHOT-12 score ≥48.5, preoperative modified Harris Hip Score ≤51.7, age >41 years, BMI ≥27, and preoperative α angle >76.6°. Conclusion: We developed novel machine learning algorithms that leveraged preoperative demographic, clinical, and imaging-based features to reliably predict clinically meaningful improvement after hip arthroscopy for FAIS. Despite consistent improvements after hip arthroscopy, meaningful improvements are negatively influenced by greater BMI, back pain, chronic symptom duration, preoperative mental health, and use of hip corticosteroid injections.

INSTRUMENTAL DIAGNOSIS AND PREOPERATIVE PLANNING OF HIP ARTHROSCOPY IN FEMOROACETABULAR IMPINGEMENT SYNDROME

Femoroacetabular impingement syndrome (FAI) is essentially a mechanical conflict that occurs when the acetabulum edge of the pelvic bone interacts with femur head and neck with clinical symptoms. In a basis of this conflict, as a rule, is a single or bilateral anatomical bone defect that causes an irregular shape of the hip joint with congenital or acquired etiology. Radiography, performed in a direct projection and in 45 Dunn position with external rotation of 40, is traditionally considered as basic tool for the radiological diagnosis of hip joint pathology. It allows to assess the anatomical and morphological structure of joint surfaces and their relationship. Detection of severe hip deformations may require computed tomography (CT). Magnetic resonance imaging (MRI) or magnetic resonance arthrography (MRA) is used to assess the condition of soft tissue structures of hip joint, its damage is often found in patients with FAI. The modern method of treating patients with FAI is hip arthroscopy, the undeniable advantage of which is low traumatic nature of the operation, low level of intraoperative complications and short postoperative rehabilitation period. For its successful implementation, it is necessary to take into account the complexity of performing hip arthroscopy, its duration, the necessity for good technical equipment and a high skill level of the operating surgeon. However, this operation has a number of limitations, which must be taken into account when selecting patients.

Nonarthritic Hip Pathology Patterns According to Sex, Femoroacetabular Impingement Morphology, and Generalized Ligamentous Laxity

Background: Sex differences are frequently encountered when diagnosing orthopaedic problems. Current literature suggests specific sex differences, such as a higher prevalence of cam-type femoroacetabular impingement syndrome in male patients and features of hip instability in female patients. Purpose: To identify hip pathology patterns according to sex, alpha angle deformity, and generalized ligamentous laxity (GLL) in a nonarthritic patient population that underwent primary hip arthroscopy in the setting of femoroacetabular impingement syndrome and labral tears. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Patients who underwent primary hip arthroscopy between February 2008 and February 2017 were included and separated into male and female groups for initial analysis. Patients were excluded if they had Tönnis osteoarthritis grade >1, previous ipsilateral hip surgery, or previous hip conditions. The demographics, radiographic findings, intraoperative findings, and surgical procedures were then analyzed and compared. Subanalyses were performed for both groups. A threshold of 1 SD above the mean alpha angle in the male group was used to create 2 subgroups. For female patients, GLL based on a Beighton score ≥4 was used to divide the group. Intraoperative findings were compared for both subanalyses. Results: A total of 2701 hips met all inclusion and exclusion criteria. Of those, 994 hips were in the male group and 1707 in the female group. The mean ± SD age was 36.6 ± 13.8 and 37.1 ± 15.0 years for the male and female groups, respectively( P = .6288). The average body mass index was significantly higher in the male group ( P < .0001). GLL was more common in women (38.6%) than men (13.6%) ( P < .001). The male group had a higher proportion of acetabular Outerbridge grade 3 (21.8%) and 4 (19.2%) lesions when compared with the female group (9.3% and 6.3%, respectively) ( P < .0001). Men in the subgroup with an alpha angle ≥78° reported higher rates of acetabular Outerbridge grade 4 damage than men with an alpha angle <78° ( P < .001). Mean lateral center-edge angle was lower in the female subgroup with Beighton score ≥4 vs <4 (23.7°± 4.2° vs 31.3°± 5.8°; P < .0001). Conclusion: In this analysis of a large cohort of patients who underwent hip arthroscopy, 2 patterns of hip pathologies were related to sex. On average, male patients had larger alpha angles and increased acetabular chondral damage when compared with their female counterparts. Furthermore, a larger cam-type anatomy was associated with more severe acetabular chondral damage in men. In the female group, the incidence of features of hip instability such as GLL were significantly higher than in the male group.

Return to Sport in Athletes With Borderline Hip Dysplasia After Hip Arthroscopy for Femoroacetabular Impingement Syndrome

Background: Data on outcomes in patients with borderline hip dysplasia (BHD) who undergo hip arthroscopy remain limited, particularly in regard to return to sport (RTS). Purpose: To evaluate outcomes in patients with BHD and their ability to RTS after hip arthroscopy for treatment of femoroacetabular impingement syndrome (FAIS). Study Design: Case series; Level of evidence, 4. Methods: Consecutive patients with self-reported athletic activity and radiographic evidence of BHD, characterized by a lateral femoral center-edge angle (LCEA) between 18° and 25° and a Tönnis angle >10°, who underwent hip arthroscopy for FAIS between November 2014 and March 2017 were identified. Patient characteristics and clinical outcomes including the Hip Outcome Score–Activities of Daily Living (HOS-ADL), Hip Outcome Score–Sports Subscale (HOS-SS), modified Harris Hip Score (mHHS), international Hip Outcome Tool (iHOT-12), and visual analog scale (VAS) for pain and satisfaction were analyzed at minimum 2-year follow-up. In addition, all patients completed an RTS survey. Results: A total of 41 patients with a mean age and body mass index (BMI) of 29.6 ± 13.4 years and 25.3 ± 5.6, respectively, were included. Mean LCEA and Tönnis angle for the study population were 22.7°± 1.8° and 13.3°± 2.9°, respectively. A total of 31 (75.6%) patients were able to RTS after hip arthroscopy at a mean of 8.3 ± 3.2 months. A total of 14 patients (45.2%) were able to RTS at the same level of activity, 16 patients (51.6%) returned to a lower level of activity, and only 1 (3.2%) patient returned to a higher level of activity. Of the 11 high school and collegiate athletes, 10 (90.9%) were able to RTS. All patients demonstrated significant improvements in all patient-reported outcome measures (PROMs) as well as in pain scores at a mean of 26.1 ± 5.4 months after surgery. Patients who were able to RTS had a lower preoperative BMI than patients who did not RTS. Analysis of minimum 2-year PROMs demonstrated better HOS-ADL, HOS-SS, mHHS, iHOT-12, and VAS outcomes for pain in patients able to RTS versus those who did not RTS ( P < .05). Conclusion: Of the patients with BHD studied here, 75.6% of patients successfully returned to sport at a mean of 8.3 ± 3.2 months after hip arthroscopy for FAIS. Of the patients who successfully returned to sport, 45.2% returned at the same level, and 3.2% returned at a higher activity level.

Clinical Outcomes and Reoperation Rates After Hip Arthroscopy in Female Athletes With Low Versus Normal Body Mass Index: A Propensity-Matched Comparison With Minimum 2-Year Follow-up

Background: The effect of low body mass index (BMI) on outcomes in female athletes is unknown. Purpose: (1) To report minimum 2-year patient-reported outcomes and return to sports for high-level female athletes with low BMI undergoing hip arthroscopy for femoroacetabular impingement syndrome and (2) to compare results with those of a propensity-matched control group of high-level female athletes with a normal BMI. Study Design: Cohort study; Level of evidence, 3. Methods: Data were collected on all professional, collegiate, and high school female athletes who had a low BMI and underwent primary hip arthroscopy between September 2009 and March 2017 at our institute. Return-to-sports status and minimum 2-year patient-reported outcomes were collected for the modified Harris Hip Score (mHHS), Nonarthritic Hip Score, Hip Outcome Score–Sport Specific Subscale, and visual analog scale (VAS) for pain. The percentage of patients achieving the minimal clinically important difference (MCID), Patient Acceptable Symptom State (PASS), and maximum outcome improvement satisfaction threshold (MOIST) was also recorded. These patients were propensity matched to high-level female athletes with a normal BMI for comparison. Results: A total of 21 high-level female athletes (25 hips) with a mean ± SD follow-up of 58.9 ± 31.5 months were included. They demonstrated significant improvement from preoperatively to latest follow-up for the mHHS, Nonarthritic Hip Score, Hip Outcome Score–Sport Specific Subscale, and VAS ( P < .001). When outcomes were compared with those of the control group, female athletes with low BMI demonstrated lower rates of achieving the MCID for the mHHS (54.5% vs 77.4%; P = .041), PASS for the International Hip Outcome Tool–12 (45.5% vs 72.6%; P = .022), and MOIST for the VAS (31.8% vs 56.5%; P = .047). There were no other significant differences in the rate of achieving the MCID, PASS, or MOIST between the groups ( P > .05). Female athletes with low BMI also had higher rates of revision when compared with the control group (27.2% vs 10.6%; P = .049), but there were comparable return-to-sports rates (75.0% vs 74.5%; P > .05). Conclusion: High-level female athletes with low BMI undergoing primary hip arthroscopy for femoroacetabular impingement syndrome demonstrated significant improvement in patient-reported outcomes and acceptable rates of return to play. When compared with a control group with normal BMI, they exhibited higher rates of revision and lower rates of achieving the MCID for the mHHS, PASS for the International Hip Outcome Tool–12, and MOIST for the VAS.