Dunn View Alpha Angle More Useful Than Femoral Head-Neck Offset to Predict Acetabular Cartilage Damage in Patients With Femoroacetabular Impingement Syndrome Undergoing Hip Arthroscopy

Alpha Angle Values Predict the Severity of Hip Chondral Damage in Patients With Cam-Type Femoroacetabular Impingement Syndrome: A Systematic Review and Meta-analysis

PURPOSE

To assess the role of alpha angle (AA) in predicting the severity of hip chondral damage in patients with cam-type femoroacetabular impingement (FAI) syndrome.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols guidelines, a systematic review was performed to summarize and critically appraise studies analyzing the prognostic capability of AA values in predicting the severity of intraoperatively evaluated hip chondral damage in patients with cam-type FAI syndrome. The risk of bias was assessed through the Quality In Prognosis Studies tool. Meta-analyses based on groups and individual data from studies with a low risk of bias were conducted. We employed a cumulative link mixed model to analyze the relationship between AA and the ordinal outcome (chondral damage). The model was adjusted for sex, age, and the lateral center-edge angle (LCEA). Interactions between sex and AA were also investigated, and probabilities were calculated.

RESULTS

Twelve studies with 4,564 patients were included in a qualitative review (aged 30-39 years, 1,822 women [40%]). Studies with a low risk of bias (n = 4; 2,945 patients) indicated that AA values are significantly smaller (mean difference [95% confidence interval] of 10.5° [6.5°-15°]) in the low-grade chondral damage group (grades 0/I/II) compared with the high-grade chondral damage group (III/IV). The cumulative link mixed model with individual patient data from studies with low risk of bias (n = 3; 1,460 patients) indicated that for each 1° increase in AA, the odds of being in a greater category of chondral damage increased by a factor of 1.04 (odds ratio 1.04, P < .0001). Men were at significantly greater risk (odds ratio 2.11, P < .0001) than women, but no significant interaction between sex and AA was observed (P = .054). We estimate the average probability of having high-grade chondral damage to be greater than 33% when AA values surpass 71° for men and 90° for women, and greater than 50% when 89° for men and 108° for women. However, the heterogeneity observed across studies should be considered.

CONCLUSIONS

The AA is a significant predictor of hip chondral damage severity in patients with cam-type FAI syndrome, regardless of sex and independently of age and LCEA. In addition, men are at a greater risk of chondral damage than women, and this risk increases with aging but decreases with the magnitude of the LCEA.

LEVEL OF EVIDENCE

Level III, systematic review of Level II and III studies.

Editorial Commentary: Timely Treatment of Femoroacetabular Impingement Syndrome Both Treats Ongoing Hip Symptoms and Mitigates Future Cartilage Damage and Osteoarthritis

Patients with femoroacetabular impingement syndrome (FAIS) present with ongoing symptoms in a painful hip. Insightful patients or family members often express concern about similar pathology, and associated risk of arthritis, in their less or asymptomatic hip, and recent research shows that patients with increased alpha angles are associated with more advanced cartilage damage, particularly in males. The ultimate question, for surgeons and patients, is: Can we predict chondral pathology based on preoperative variables alone, and should we intervene prior to symptoms? Yet, FAIS is multifactorial, not simply anatomic, and cam-type FAI can have a high prevalence in asymptomatic hips in some populations. Thus, today, prophylactic hip preservation surgery cannot be generally recommended, but in the future, an individualized treatment algorithm may result in precise prediction of which patients might benefit from earliest intervention to help reduce the incidence of premature hip osteoarthritis. In the interim, when timely intervention is in the best interest of the patient, insurance denials that delay indicated surgery must not be tolerated. One of the most rewarding and unique aspects of managing FAIS is that we have the opportunity to both treat ongoing hip symptoms and mitigate future pathology, sometimes even in the contralateral hip.

Current understanding of articular cartilage lesions in femoroacetabular impingement syndrome

The concept of femoroacetabular impingement syndrome (FAIS) has received much attention over the past 20 years. Currently, it is believed that FAIS can lead to intra-articular pathologies such as labral tears and articular cartilage lesions, resulting in clinical symptoms and subsequent poor clinical outcomes. FAIS-related articular cartilage lesions are common but unique, and their natural course always leads to early osteoarthritis of the hip. However, despite these cartilage lesions having gradually gained considerable attention, limited consensus has been reached on key aspects, such as diagnosis, mechanisms, classification, and management strategies, which limits clinical and research advances. Hence, an intensive comprehensive overview based on the existing evidence is necessary. The purpose of this review was to introduce the general consensus, controversial issues, and recent advances in FAIS-related articular cartilage lesions.

Lateral center-edge angle in femoroacetabular impingement: from the sourcil or the rim of the acetabulum?

The correlation between clinical outcomes and preoperative/postoperative measures of the lateral center-edge angle (LCEA) will help establish the cutoff values for this measurement and determine whether to obtain it from the lateral acetabular rim (LCEAR) or the lateral end of the sourcil (LCEAS). The hypothesis was that the LCEAS would be more sensitive than the LCEAR. An upper cutoff value of LCEA could predict better functional outcomes in FAI patients. 106 patients (103 unilateral, 3 bilateral) who underwent hip arthroscopy surgery due to FAI and had a minimum 2-year follow-up were included. Patient-reported outcomes included the mHHS and visual analogue scale for pain (Pain VAS). Radiological parameters (alpha angle, LCEAS, LCEAR) were evaluated at the pelvis, 45° Dunn X-rays. A receiver operating characteristic analysis was used to evaluate the correlation between significant variables and achievement of patient-acceptable symptomatic state (PASS) and calculate area under the curve (AUC) and critical values for LCEA. The mean age of the patients was 34 ±10 years with a mean follow-up of 5 years. There were 75 male and 31 female patients. The mHHS improved from 57 ± 11 before surgery to 93 ± 8 after surgery (P < .001). The Pain VAS decreased from 6 before surgery to 1 after surgery (P < .001). A higher frequency of reaching the PASS threshold for mHHS was associated with lower preoperative and postoperative dunn LCEAS and postoperative dunn LCEAR. Preoperative dunn LCEAS ≤ 24.8° had an AUC of 0.67, predicting PASS (+) with 0.38 sensitivity and 0.93 specificity. Combining LCEAS with other parameters further improved predictability. LCEAS seems more predictive of clinical significance than LCEAR. However, predictivity exceeds the acceptable limit when they are measured together. The upper values for LCEAS and LCEAR seem to be 24° and 35°, respectively.

Eighty-One Percent of Unrepaired Interportal Capsulotomies Showed Healed Capsules on Magnetic Resonance Imaging 5 Years After Primary Hip Arthroscopy

Purpose

To evaluate whether unrepaired interportal capsulotomy presents with capsular defect on magnetic resonance imaging (MRI) 5 years after primary hip arthroscopy and to determine its effect on functional results and findings of osteoarthritis on radiographs or MRI scans.

Methods

Patients with femoroacetabular impingement (without arthritis or dysplasia) were retrospectively reviewed after arthroscopic labral repair or debridement and femoroplasty through interportal capsulotomy without closure. Patients were assessed preoperatively and at a minimum of 5 years postoperatively using patient-reported outcomes (Hip Outcome Score-Activities of Daily Living scale, modified Harris Hip Score, and visual analog scale pain score), radiographic measures, and MRI scans.

Results

Forty patients (42 hips) were deemed eligible for the study and were evaluated. Of the hips, 81% had healed capsules, whereas 8 (19%) had capsular defects on the latest MRI scan. There were 3 hips with subchondral edema in the defect group compared with 1 in the healed-capsule group (P = .01) on the latest MRI scan, which was not present on preoperative MRI (still positive on multivariate analysis when the preoperative alpha angle was also taken into consideration). Functional results did not differ between the groups (P > .05).

Conclusions

In this study, 81% of interportal capsulotomies healed without repair at 5 years after primary hip arthroscopy.

Clinical Relevance

Understanding the prevalence and implications of unhealed capsulotomies could encourage surgeons to be meticulous in capsular closure.

Effect of cam resection depth on clinical outcomes after primary hip arthroscopy

BACKGROUND

The amount of resection or the starting point of the resection on the femoral head for cam lesions in femoroacetabular impingement (FAI) is controversial.

AIM

The purpose of this study was to study the effect of postoperative resection depth, and resection arc ratio of cam lesion on the frequency of achieving substantial clinical benefit (SCB), patient acceptable state (PASS) in modified Harris Hip Score (mHHS) and Hip Outcome Score Activity of Daily Living (HOSADL), 2 years postoperatively.

PATIENTS AND METHODS

All patients who underwent first-time hip arthroscopy for FAI with a 2-year follow-up were included in this study. Patient-reported outcomes included the mHHS, HOSADL, and visual analogue scale for pain (Pain VAS). Radiological parameters such as alpha angletraditional (αT), alpha anglecartilage (αC), resection arc ratio (% alpha anglecartilage-alpha angletraditional/360°), resection depth (''D''mm) and resection depth ratio 'D%' (D/femoral head diameter %) were measured using the 45° Dunn view.

RESULTS

We identified 26 patients (27 hips) with 2-year follow-up. There were 10 female and 16 male patients. The mean age of the patients was 33 ± 12 years.Higher frequency of achieving SCB threshold for mHHS was related to labrum repair (73% vs. debridement '27%' p = 0.03), lower preoperative αT (64° vs. 76°, p = 0.04), lower preoperative mHHS (54 vs. 81, p < 0.001) and higher preoperative VAS scores (8 vs. 7, p = 0.02). Higher frequency of reaching PASS threshold for mHHS was associated with lower αC (82°vs. 92° p:0.02), lower RA (8% vs. 11%, p = 0.03), lower D (2.8 mm vs. 4.5 mm p:0.03), lower D% (4.7% vs. 8.4% p = 0.04) and higher postoperative mHHS (97 vs. 82 p < 0.001).

CONCLUSIONS

A higher frequency of achieving SCB for HOSADL was related to lower D% (5% vs. 10.5%, p = 0.04).Cam resection depth affects the frequency of achieving clinically meaningful scores and resection depth less than 6% of the femoral head diameter seems to be appropriate for optimal results. The starting point of resection on head cartilage needs to be <90° when alpha angle is used for reference.

Young Bovine Hip Model for Hip Arthroscopy Training

Hip arthroscopy is associated with risks for complications, especially for novice surgeons. The present article reports use of a young bovine hip as a valid educational tool for key components of arthroscopic treatment of femoroacetabular impingement syndrome, ie, labrum repair and cam excision. The purpose of this Technical Note is to describe the steps of arthroscopic femoroacetabular impingement treatment in the bovine hip.

Anterior and Lateral Femoroacetabular Excursion Angles Are Helpful for Assessing Femoroacetabular Impingement Syndrome: A Cross-Sectional Cohort Study

PURPOSE

To develop a radiographic measurement to evaluate the femoroacetabular space using 3-dimensional (3D) hip models in asymptomatic hips, and to evaluate the reliability and validity of the femoroacetabular excursion angle (FAEA) in symptomatic patients.

METHODS

From January 2020 to December 2020, we recruited patients with healthy hips to establish 3D models. Through the simulation of 14 activities of daily living (ADLs), anterior and lateral impingement-free FAEAs were measured. Another cross-sectional cohort was formed from consecutive symptomatic subjects with impingement signs during the same period. In the validation cohort, anterior and lateral FAEAs were assessed on modified Dunn's and anteroposterior views of the hip, respectively. We evaluated the reliability and clinical implications of the FAEAs.

RESULTS

In the discovery cohort (n = 33), hips with collisions tended to have smaller computed tomography-based FAEAs than collision-free hips, although alpha and lateral center-edge (CE) angles were comparable. Additionally, hips with a lower quartile of FAEAs had a significantly higher number of ADLs with collisions. In the validation cohort (n = 411), the FAEA measurement was highly reliable (kappa statistics >0.95 for both interobserver and intraobserver reliabilities). The femoroacetabular impingement syndrome (FAIS) group (n = 165) showed significantly smaller anterior and lateral FAEAs than the non-FAIS group (all P < .001, Cramer V = .420). The optimal cut-off values for anterior and lateral FAEAs were 32.6° and 48.9°, respectively. In univariate regression, anterior (odds ratio [OR] = 0.91; 95% confidence interval [CI] = 0.89-0.94) and lateral (OR = 0.91; 95% CI = 0.89-0.93) FAEAs were significantly associated with FAIS. Moreover, in multivariate regression adjusted for alpha and lateral CE angles, anterior FAEA remained a significant predictor (OR = 0.96; 95% CI = 0.93-0.99), and small FAEA was an independent risk factor for FAIS (OR = 1.99; 95% CI = 1.06-3.71) for any small FAEA (OR = 2.88; 95% CI = 1.32-6.31) for both small FAEAs.

CONCLUSION

The FAEA is a valid measurement for FAIS with high reliability. Small FAEA was an independent risk factor for FAIS in the multivariate regression model, even after adjusting for alpha and lateral CE angles.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Postoperative alpha angle seems to be important for the achievement of clinical significance at a minimum 5-year follow-up after primary hip arthroscopy

The purpose of the present study was to clarify whether there is an association of postoperative alpha value with functional scores or progression of osteoarthritis at X-rays at the midterm after arthroscopic treatment of femoroacetabular impingement (FAI) syndrome with femoral osteoplasty, labral repair or debridement and rim trimming. A retrospective review of prospectively gathered data from 2013 to 2017 was performed. All patients who underwent first-time unilateral hip arthroscopy for FAI resection with 5-year follow-up were included. Patient-reported outcomes included the modified Harris Hip Score (mHHS) and Visual Analog Scale for Pain (Pain VAS). The progression of osteoarthritis (Tönnis grade) and radiological parameters (alpha angle, lateral center-edge angle [LCEA] and head-neck offset) were evaluated. A receiver operating characteristic (ROC) analysis was used to evaluate the correlation between significant variables and achievement of patient-acceptable symptomatic state (PASS) and degree of osteoarthritis. We identified 52 patients with a minimum 5-year follow-up (average, 6.7 years). The average patient age was 33.9 ± 11.5 years. There were 19 (36.5%) female patients. The mHHS improved from 60.1 ± 13.4 before surgery to 86.8 ± 14 after surgery (P < 0.001). The Pain VAS decreased from 6.21 before surgery to 2 after surgery (P < 0.001). Overall, 69% achieved the PASS for mHHS. The ROC curve for postoperative alpha angle demonstrated acceptable discrimination between patients achieving a fifth-year PASS value and those who did not have an area under the curve of 0.72. Patients having a postoperative alpha angle of ≤48.3° achieved the fifth-year PASS value at a significantly higher rate than patients having a postoperative alpha angle of >48.3° (P = 0.002). The postoperative alpha angle is a predictor of the achievement of the fifth-year PASS value for the mHHS. A threshold of ≤48.3° had a sensitivity of 0.75 and a specificity of 0.69 to predict positivity. Level of evidence IV.

Acetabular Cartilage Lesions Predict Inferior Mid-Term Outcomes for Arthroscopic Labral Repair and Treatment of Femoroacetabular Impingement Syndrome

PURPOSE

To analyze the effect of acetabular chondrosis at a minimum of 2 years following hip arthroscopy in patients undergoing labral repair and treatment of femoroacetabular impingement.

METHODS

From 2014 to 2017, patients undergoing arthroscopic labral repair were prospectively enrolled in a multicenter hip arthroscopy registry. The registry was retrospectively queried for primary labral repair patients with complete 2-year outcomes and a Tonnis grade of less than 2. Patients were grouped according to severity of articular cartilage damage noted intraoperatively using the Beck classification system: none, low-grade (Grade 1 or 2), or high-grade (Grade 3 or 4) damage. A Kruskal-Wallis test and post hoc Dunn's test with Holm correction compared 2-year postoperative outcome scores of the iHOT-12 scale between groups. The proportion of patients in each cohort who achieved the clinically significant thresholds of the minimum clinically important difference (MCID), patient-acceptable symptom scale, and substantial clinical benefit (SCB) were analyzed. Multivariate logistic regression models identified predictors of achieving clinical thresholds while controlling for demographic variation.

RESULTS

422 patients met inclusion criteria, from which 347 completed 2-year outcomes. All groups experienced improvement in iHOT-12 scores from baseline to follow-up (P < .001). iHOT-12 scores at follow-up were inferior for Low-Grade Damage and High-Grade Damage Groups relative to the No Damage Group (P = .04; P = .03). When accounting for age, body mass index, gender, and preoperative iHOT-12 scores in logistic regression models, the presence of high-grade lesions was a negative predictor for achieving SCB (OR [95% CI], 0.54 [0.29-0.96]) and low-grade lesions a negative predictor for achieving MCID (0.50 [0.27-0.92]. Among patients with high-grade lesions, there was no significant difference in 2-year iHOT-12 scores between those undergoing chondroplasty (n = 50) and those undergoing microfracture (n = 14) (P = .14).

CONCLUSIONS

Acetabular cartilage damage portends inferior patient-reported outcomes 2 years after primary labral repair and treatment of femoroacetabular impingement. The presence of cartilage lesions was a negative predictor of individual achievement of several clinical thresholds.

LEVEL OF EVIDENCE

III, Retrospective comparative cohort.

Editorial Commentary: The Measurement of the Alpha Angle in Femoroacetabular Impingement Syndrome With a 45° Dunn-View Radiograph Predicts the Cartilage Damage on the Acetabular Side of the Hip Joint-Is It as Simple as That?

In recent years, femoroacetabular impingement syndrome (FAIS) has developed itself into a well-known pathology throughout the orthopaedic community worldwide. The more we learned, the more sophisticated it became: In the beginning, we measured the femoral head-neck offset; then, the alpha angle was found to be a useful measurement in detecting FAIS. We learned to perform these measurements with, for example, the 45° Dunn view. The alpha angle, but not the femoral head-neck offset, measured as described, predicts not only the acetabular cartilage damage resulting from FAIS but also the correlation between the degree of the alpha angle and the severity of the cartilage damage within the acetabular labrum articular disruption and Outerbridge classifications. The femoral head-neck offset cannot provide us with this information, but it is the first sign we all look at before taking any measurements on radiographs or magnetic resonance imaging scans if a cam morphology could be present. It is paramount to understand the underlying problems of the individual hip and distinguish instability (dysplasia) from FAIS and also to evaluate femoral torsional abnormalities to perform the appropriate treatment using magnetic resonance imaging and computed tomography scans if necessary. The alpha angle quantifies the severity of the pathology and predicts the possible cartilage damage in FAIS patients, but in our opinion, we cannot neglect the femoral head-neck offset, because it is often the first radiologic sign of FAIS that most of us realize on a radiograph. Therefore, both signs have their place in detecting and treating FAIS.