Predictive Value of 3-T Magnetic Resonance Imaging in Diagnosing Grade 3 and 4 Chondral Lesions in the Hip

The Relationship Between the Joint Space and Outcomes After Hip Arthroscopic Surgery for Femoroacetabular Impingement: Reevaluating the 2-mm Rule

BACKGROUND

A limited joint space (<2 mm) is associated with poorer outcomes and conversion to total hip arthroplasty (THA) after hip arthroscopic surgery. As indications for hip arthroscopic surgery expand, it is important to reevaluate established risk factors among large patient populations.

PURPOSE

To reevaluate the relationship between the radiographic joint space and outcomes after hip arthroscopic surgery and to assess the validity of a joint space of 2 mm as the accepted cutoff for successful hip arthroscopic surgery.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients aged 18 to 50 years who underwent hip arthroscopic surgery for femoroacetabular impingement between January 2008 and December 2016 and had a minimum 2-year follow-up were included. Patients with previous ipsilateral hip surgery, a history of hip fractures, dysplasia (lateral center-edge angle <20°), or osteoarthritis (Tonnis grade >2) were excluded. The joint space was categorized as diminished (≤2 mm), borderline (>2 to ≤3 mm), or preserved (>3 mm). Minimum 2-year patient-reported outcomes (modified Harris Hip Score [mHHS], Hip Outcome Score-Activities of Daily Living [HOS-ADL], Hip Outcome Score-Sports-Specific Subscale [HOS-SSS]), revision rates, and rates of conversion to THA were compared between groups.

RESULTS

A total of 699 patients (782 hips) with a mean age of 33.8 ± 10.1 years met 2-year inclusion criteria. The mean follow-up time was 4.2 ± 2.1 years. Overall, 51 hips (6.5%) had a diminished joint space, 297 (38.0%) had a borderline joint space, and 434 (55.5%) had a preserved joint space. Patients with a diminished joint space had larger femoral and acetabular defects compared with those with larger joint spaces. All groups had improved patient-reported outcome scores compared with baseline (P < .001 for all), and there were no differences between the groups in the percentage of patients who reached the minimal clinically important difference or patient acceptable symptom state. There were also no differences between the groups in revision rates (P = .95). A greater number of hips with a diminished joint space converted to THA (n = 8 [15.7%]) compared with those with a borderline (n = 9 [3.0%]) or preserved (n = 9 [2.1%]) joint space (P < .001). Considering joint space as a continuous variable, adjusted logistic regression showed that for every millimeter decrease in the joint space, the odds of conversion to THA increased by a factor of 2.5 (odds ratio, 2.5 [95% CI, 1.6-3.8]).

CONCLUSION

This study demonstrated that patients with a diminished joint space were at a higher risk of conversion to THA. Although 2 mm should not serve as a strict cutoff, patients should be counseled based on their preoperative radiographic findings accordingly.

Patients Undergoing Primary Hip Arthroscopy Report Favorable Outcomes at Minimum 10 Year Follow-Up: A Systematic Review

PURPOSE

(1) To evaluate minimum 10-year PROs (patient-reported outcomes) and survivorship after primary hip arthroscopy and (2) to identify predictors of failure for secondary arthroscopy and conversion to total hip arthroplasty (THA).

METHODS

A systematic review of the literature was conducted with the following key words: "hip arthroscopy," "long-term," "outcomes," "ten-year," "survivorship," "10-year," "15-year," "fifteen-year," 20-year," "twenty-year," and "femoroacetabular impingement" in PubMed and Embase in March 2022 using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Level I to Level IV evidence was included and reported on minimum 10-year outcomes or greater after primary hip arthroscopy. Long-term studies were defined as minimum 10-year follow-up in accordance with established standards in the literature. Case reports, review articles, technique articles, and opinion articles were excluded. Articles not in English were excluded. Title, author, publication date, study design, demographic, number of hips, follow-up time, study period, indications for hip arthroscopy, PROs, predictors of failure for THA, and rates of secondary surgeries were recorded. Survivorship was defined as a nonconversion to THA. P < .05 was defined as statistical significance.

RESULTS

Twelve studies met the inclusion criteria. In total, 4 studies were Level III, and 8 studies were Level IV. A total of 1,344 hips were included, and follow-up ranged from 10 to 20 years. Femoroacetabular impingement syndrome was the most common indication for hip arthroscopy. Ten of the 12 studies reported on PROs, and 8 studies reported significant improvement after hip arthroscopy at long-term follow-up. The remaining 2 studies reported favorable outcomes that satisfied clinical benefit thresholds at minimum 10-year follow-up. Five studies reported clinical benefit where each patient cohort achieved 80% minimal clinically important difference and 75% patient acceptable symptomatic state for at least one PRO. Rates of secondary arthroscopy ranged from 4.5% to 24%, and rates of conversion to THA varied from 0% to 44.1%. Older age and chondral damage were the most commonly cited predictors for conversion to THA.

CONCLUSIONS

At long-term follow-up, patients who underwent primary hip arthroscopy demonstrated favorable outcomes and variable rates of secondary surgeries. Patients undergoing hip arthroscopy within the last 20 years with Tönnis grade <1 and labral repair experienced greater than 90% survivorship. Chondral damage and older age were the most cited predictors for conversion to THA.

LEVEL OF EVIDENCE

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

Evolutionary course of the femoral head osteonecrosis: Histopathological - radiologic characteristics and clinical staging systems

Osteonecrosis of the femoral head (ONFH) is a recalcitrant ischemic disorder, which could be classified into two major categories: traumatic and nontraumatic. Regardless of different risk factors, it has been testified that ONFH results from primitive vascular problems, leading to temporary or permanent loss of blood supply to bone tissue. Histopathological and microarchitectural alterations ensues, which is a gradual evolutionary process involving bone marrow and osteocyte necrosis, progressive destruction of subchondral bone, unsuccessful reparative process, and eventual articular collapse and degenerative arthritis. Based on the imaging features of ONFH, different classification systems have been developed to evaluate the severity and prognosis of the disease, which is pivotal for implementation of treatment strategy, especially the joint-preserving surgery. However, patients classified with the same severity stage, especially in the peri-collapse stage, sometimes responded differently after similar joint-preserving surgery. The unusual phenomenon may be attributed to the limitation of the current imaging classification systems, which might underestimate the disease severity, especially when referring to the early stages. In this review, we briefly summarize the etiology and pathogenesis of ONFH. The imaging features and staging classification systems of ONFH are also described. More importantly, we focus on histopathological and microstructural alterations of the femoral head, and provide an overview of their essential contribution to ONFH progression. Given the observation of discordance between imaging characteristics and histopathological alterations, a substantial amount of research on the relationship between imaging and histopathological features is required to further modify and revise the current wide-accepted classification systems.

Magnetic Resonance Imaging Predictors of Chondral Lesions in Patients With Femoroacetabular Impingement: An Analysis of 545 Cases

PURPOSE

A large prospective cohort was used (1) to evaluate the overall ability of magnetic resonance imaging (MRI) to detect Outerbridge grade III and IV cartilage defects found during surgery and (2) to identify the specific MRI findings most associated with these cartilage defects so that the practicing hip arthroscopist can better predict cartilage injury before surgery.

METHODS

All patients undergoing hip arthroscopy between February 2015 and May 2017 at 1 institution were enrolled in a prospective cohort. Intra-articular findings were documented at the time of surgery. MRI reports were retrospectively reviewed for radiologist-reported articular cartilage, osseous, or synovial abnormalities. Sensitivity and specificity of MRI findings were calculated; multivariate logistic regression analysis determined which findings were associated with high-grade chondral damage at the time of arthroscopy and used to create an online risk calculator, https://orthop.washington.edu/hiprisk/.

RESULTS

Of 598 patients who underwent hip arthroscopy, 550 had MRI reports available for review (92%). Grade III and IV cartilage injuries were reported on arthroscopy in 70 patients (13%) of average age 33 ± 13 years. On univariate analyses, individual MRI findings were not sensitive in detection of articular cartilage injury (mean 22%; range, 1.4%-46%), but positive findings were highly specific (mean 90%,; range, 76%-99%). Multivariate analysis revealed that older age (odds ratio [OR] 1.09 [1.06-1.11], P < .001) and osseous findings such as subchondral cyst or edema (OR 4.77 [2.51-9.05], P < .001) were most predictive of grade III and IV defects (P < .001).

CONCLUSION

MRI was a specific but not sensitive tool in diagnosing articular cartilage injury. Surgeons should be aware that osseous findings such as cysts or edema are highly predictive of full-thickness cartilage loss in FAI.

LEVEL OF EVIDENCE

Level III, development of diagnostic criteria (consecutive patients with consistently applied reference standard, no blinding).

Intra-articular pathology affects outcomes after joint preserving surgery for osteonecrosis of the femoral head

PURPOSE

Currently, knowledge regarding the intra-articular pathology and its relationship to outcomes after joint-preserving surgery in patients with osteonecrosis of the femoral head (ONFH) is lacking. The purposes were to evaluate the intra-articular pathology and its relationship with outcomes of joint-preserving surgery in ONFH.

METHODS

We reviewed 41 hips with ONFH in 41 patients (27 women; mean age, 34.9 years old) who underwent intertrochanteric curved varus osteotomy. Radiographic evaluations were based on pre-operative imaging studies, including radiographs, computed tomography (CT), and magnetic resonance imaging (MRI). Intra-articular pathology was evaluated by arthroscopic inspection of the femoral head, labrum, and acetabular cartilage during surgery. In addition, we performed radiographic measurements of the hip, including the collapse of the femoral head and minimal joint space width at three  years post-operatively and at final follow-up.

RESULTS

Arthroscopy revealed damage to the acetabular cartilage and labrum in 22 (54%) and 13 patients (32%), respectively. However, these lesions could be detected on imaging in only 13 (32%) and ten patients (24%), respectively. The change in joint space width after surgery was significantly higher in patients with cartilage degeneration and labral injury (P = 0.02, P = 0.02). Logistic regression analysis for subsequent progression of osteoarthritis showed an association with degenerative changes of articular cartilage and the labral tear as independent predictors (P = 0.001, P = 0.03).

CONCLUSIONS

Our data demonstrate the presence of labral and acetabular cartilage lesions in ONFH patients, while images do not reveal the full extent of the tissue damage. These intra-articular pathologies can be associated with the outcomes after joint-preserving surgery.

The Evolution of Hip Arthroscopy: What Has Changed Since 2008-A Single Surgeon's Experience

PURPOSE

To compare a single surgeon's first 200 cases of hip arthroscopy with the last 200 cases regarding patient demographic characteristics, indications for surgery, intraoperative findings, procedures performed, and patient-reported outcomes.

METHODS

Data were reviewed for all patients undergoing primary hip arthroscopy between February 2008 and August 2016 performed by a single surgeon. Of the 3,319 patients who underwent hip-preservation surgery during the study period, the first 200 (group A) and last 200 (group B) eligible for minimum 2-year follow-up were included in our analysis.

RESULTS

Follow-up was available for 187 of 200 patients (93.5%) and 189 of 200 patients (94.5%) in groups A and B, respectively. The groups were similar in age, sex, and body mass index (P > .05). Group A included significantly more patients with Tönnis grade 1 (37% vs 21%, P < .001). Group B consisted of significantly more (P < .001) labral reconstructions (10.2% vs 0%), capsular closures (72.7% vs 26.2%), and gluteus medius repairs (18.2% vs 3.2%). Femoroplasty was performed for smaller cam lesions in group B, resulting in smaller postoperative alpha angles (45.7° ± 7.9° vs 42.4° ± 6.3°, P < .001). Group B exhibited significantly higher patient-reported outcomes at minimum 2-year follow-up (P < .05). In addition, in group B, greater proportions of patients achieved the minimal clinically important difference and patient acceptable symptomatic state (P < .05).

CONCLUSIONS

This study shows the noteworthy evolution in the management of the prearthritic adult hip occurring between 2008 and 2016. This includes improvements in preoperative patient evaluation and patient selection. In addition, the proportion of patients undergoing labral reconstruction, capsular plication, and femoroplasty has increased significantly. These developments, as well as increased surgical experience, may have contributed to improved surgical outcomes.

LEVEL OF EVIDENCE

Level III, retrospective comparative trial.

Impacto femoroacetabular – Fatores associados à presença de lesões profundas da junção condrolabral

Objective  The purpose of the present study was to evaluate factors associated with the presence of deep chondral lesions (Konan/Haddad grades III and IV) in patients submitted to hip arthroscopy to treat femoroacetabular impingement (FAI).

Method  This was a prospective, cross-sectional study of a series of 125 consecutive hip arthroscopies performed between May 2016 and May 2017. After applying the exclusion criteria, 107 hips of 92 patients submitted to surgical treatment for mixed and CAM FAI were analyzed. For purposes of analysis, the present study considered groups with lesions considered mild and deep, which were associated with symptom score, lateral coverage angle, α angle, age, gender, and radiological classification of arthrosis. Results with a p -value < 0.05 were considered statistically significant.

Results  Patients whose hips had lesions considered deep had significantly higher nonarthritic hip scores (NAHSs) than those whose hips presented lesions considered mild or who did not present chondral lesions (67.9 ± 19.4 versus 57.0 ± 21.9, p  = 0.027). The prevalence of deep lesions was higher in hips with Tonnis 1 compared with hips with Tonnis 0: 15 (55.6%) versus 10 (12.7%), respectively, p  < 0.001. Men presented a higher prevalence of grades III and IV lesions than women, 23 (34.3%) versus 2 (5.0%), p  = 0.001, and had significantly higher functional scores (65.6 ± 19.6 versus 49.3 ± 21.6, p  < 0.001).

Conclusion  Men presented a higher prevalence of deep lesions. Hips classified as Tonnis 1 presented a 4.4-fold higher probability of presenting these lesions. Patients with deep chondrolabral lesions had a better preoperative functional score.

Editorial Commentary: Predictive Nomograms for Hip Chondral Lesions: A Poor Man's Magnetic Resonance Imaging?

As the use of hip arthroscopy continues to increase, there is a greater need to identify prognostic factors to aid in patient selection, presurgical planning, and the management of postoperative patient expectations. These prognostic factors may then be used to aid in the development of predictive clinical tools that could help identify the presence of chondral pathology. These tools may provide an advantage over magnetic resonance imaging, which has previously been shown to have limited sensitivity in the detection of chondral injuries in the hip. If proven accurate, these nomogram tools may limit the future role of magnetic resonance imaging in the evaluation of hip pain. Future efforts should focus on validating these tools and on evaluating whether they are capable of changing clinical treatment algorithms.

Predicting Severe Cartilage Damage in the Hip: A Model Using Patient-Specific Data From 2,396 Hip Arthroscopies

PURPOSE

To determine patient-specific factors that can be used to predict the presence of severe articular cartilage damage in the hip in patients without osteoarthritis.

METHODS

The prevalence of severe (Outerbridge grade III or IV) cartilage damage to the acetabulum and femoral head was prospectively recorded at hip arthroscopy. Patients who underwent primary hip arthroscopic surgery between 2006 and 2016 performed by a single surgeon were included. Patients were excluded if they underwent previous hip surgery, had poor-quality radiographs, were younger than 16 years at the time of surgery, or had a minimal joint space of 2 mm or less. The relation between severe cartilage damage and preoperative patient characteristics was examined using multivariable logistic regression analysis with restricted cubic splines.

RESULTS

Of the 2,396 hips presenting for hip arthroscopy, 995 (41%) had severe cartilage damage to the acetabulum and 257 (11%) had severe cartilage damage to the femoral head. Older age was a significant risk factor for severe cartilage damage both to the acetabulum (χ² = 69.5, P < .001) and to the femoral head (χ² = 53.9, P < .001). An age of 45 years was associated with a 1.96 (95% confidence interval, 1.54-2.49) increase in the odds of severe acetabular cartilage damage and a 3.94 (95% confidence interval, 2.61-5.94) increase in the odds of severe femoral head cartilage damage relative to an age of 20 years. Male sex was associated with severe cartilage damage to the acetabulum (χ² = 66.7, P < .001), and a lower center-edge angle was a significant risk factor for severe cartilage damage to the femoral head (χ² = 78.5, P < .001). Predictive nomograms were established for severe cartilage lesions.

CONCLUSIONS

The primary risk factors for severe hip cartilage damage were older age for both the femoral head and acetabulum; a lower center-edge angle and larger Tönnis angle for the femoral head; and male sex, body mass index, alpha angle, and joint space for the acetabulum. The likelihood of cartilage damage to the hip can be estimated clinically using a prediction nomogram.

LEVEL OF EVIDENCE

Level III, cross-sectional study.

Do Femoral Head Osteochondral Lesions Predict a Poor Outcome in Hip Arthroscopy Patients? A Matched Control Study With Minimum 5-Year Follow-Up

PURPOSE

To determine whether the presence of femoral head (FH) lesions affects patient-reported outcomes (PROs) of patients undergoing hip arthroscopy for labral tears.

METHODS

Data were prospectively collected and retrospectively reviewed for all patients who underwent hip arthroscopy for labral tears at our institution from April 2008 to March 2011. Patients with FH lesions were matched to those without (control) for age, body mass index, sex, and lateral center-edge angle. The inclusion criteria were FH lesions, labral tears, and minimum 5-year follow-up. The exclusion criteria were previous hip surgery, prior hip conditions, inflammatory arthritis, Workers' Compensation claims, and Tönnis grade greater than 1. PRO scores, including the modified Harris Hip Score, Non-Arthritic Hip Score, and Hip Outcome Score-Sports Specific Subscale, were collected preoperatively and postoperatively. Visual analog scale (VAS) scores for pain and patient satisfaction were recorded.

RESULTS

We matched 96 hips with FH lesions to 96 control hips. The FH group had slightly longer follow-up (71.4 months vs 67 months, P = .004). Patients with FH lesions tended to have higher-grade acetabular lesions (grade 4 acetabular labrum articular disruption and Outerbridge grade 4 acetabular lesions). All PRO scores, VAS scores, and patient satisfaction ratings were statistically improved at latest follow-up in both groups. No statistical difference in improvement (ΔPRO and ΔVAS scores) was noted between groups. However, patients with FH lesions had a higher rate of conversion to arthroplasty (32% vs 16%, P = .0027). Patients in the control group underwent more secondary arthroscopies (14% vs 5%, P = .05).

CONCLUSIONS

Finding an FH chondral lesion at arthroscopy does not necessarily portend a worse clinical outcome or conversion to total hip arthroplasty, when controlling for other variables. Patients with FH lesions were, however, found to have worse intra-articular hip pathology. When combined with these factors, patients with FH lesions had lower outcome scores and double the rate of conversion to arthroplasty than patients without them.

LEVEL OF EVIDENCE

Level III, case-control study.

Diagnostic Accuracy of Magnetic Resonance Arthrography in Detecting Intra-articular Pathology Associated with Femoroacetabular Impingement

Purpose  The aim of this study was to assess the diagnostic accuracy of magnetic resonance arthrography (MRA) in the detection of intra-articular lesions of the hip in patients affected by femoroacetabular impingement (FAI) by using arthroscopy as reference standard.

Methods  Twenty-nine consecutive hip arthroscopies performed in 24 patients were considered for the study. Patients had a mean age of 38.3 years. Ultrasound-guided 1.5-T MRA was performed with precontrast short tau inversion recovery, T1-weighted and PD coronal, T1-weighted, and T2-weighted axial with 3-mm-thick slice sequences, and postcontrast T1-weighted fat saturation MRA (Fat-SAT) axial, coronal and oblique sagittal, and T1-weighted Vibe 3D coronal sequences with MPR sagittal, axial, and radial reconstructions with 2-mm-thick slice and coronal density protonil (DP) Fat-SAT. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MRA were evaluated by comparison arthroscopy for the following intra-articular findings: acetabular and femoral chondral lesions, labral degeneration, labral tears, synovitis, ligamentum teres (LT) tears, CAM lesions, pincer lesions, loose bodies, and osteophytes.

Results  An absolute per cent agreement (100%) was observed for all the variables in the assessment of CAM lesions. Sensitivity, specificity, PPV, and NPV of MRA were 100, 68.4, 72.7, and 100%, respectively, for acetabular chondral lesions; 100, 50, 47.3, and 100%, respectively, for femoral chondral lesions; 33, 85, 20, and 91.6%, respectively, for labral tears; 95, 71, 91.3, and 83.3%, respectively, for labral degeneration; 100, 88, 57.1, and 100%, respectively, for LT tears; 33.3, 85, 50, and 73.9%, respectively, for pincer lesions; 50, 96, 66.6, and 92.3%, respectively, for intra-articular loose bodies; and 100, 73.9, 50, and 100%, respectively, for osteophytes.

Conclusion  MRA may play an important role in detecting intra-articular lesions associated with FAI. This might be helpful for the preoperative planning before hip arthroscopy.

Level of Evidence  This is a Level 2, diagnostic accuracy study compared with gold standard.

T2*-Mapping of Acetabular Cartilage in Patients With Femoroacetabular Impingement at 3 Tesla: Comparative Analysis with Arthroscopic Findings

Objective To evaluate the diagnostic accuracy of T2*-mapping for detecting acetabular cartilage damage in patients with symptomatic femoroacetabular impingement (FAI). Design A total of 29 patients (17 females, 12 males, mean age 35.6 ± 12.8 years, mean body mass index 25.1 ± 4.1 kg/m², 16 right hips) with symptomatic FAI underwent T2* MRI and subsequent hip arthroscopy. T2* values were obtained by region of interest analysis in seven radially reformatted planes around the femoral neck (anterior, anterior-superior, superior-anterior, superior, superior-posterior, posterior-superior, posterior). Intraoperatively, a modified Outerbridge classification was used for assessment of the cartilage status in each region. T2* values and intraoperative data were compared, and sensitivity, specificity, negative predictive values (NPV) and positive predictive values (PPV) as well as the correlation between T2*-mapping and intraoperative findings, were determined. The mean time interval between MRI and arthroscopy was 65.7 ± 48.0 days. Results Significantly higher T2* values were noted in arthroscopically normal evaluated cartilage than in regions with cartilage degeneration (mean T2* 25.6 ± 4.7 ms vs. 19.9 ± 4.5 ms; P < 0.001). With the intraoperative findings as a reference, sensitivity, specificity, NPV and PPV were 83.5%, 67.7%, 78.4% and 74.4%, respectively. The correlation between T2*-mapping and intraoperative cartilage status was moderate (ρ = -0.557; P < 0.001). Conclusions T2*-mapping enabled analysis of acetabular cartilage with appropriate correlation with intraoperative findings and promising results for sensitivity, specificity, PPV, and NPV in this cohort. Our results emphasize the value of T2*-mapping for the diagnosis of hip joint cartilage pathologies in symptomatic FAI.

The Correlation Between Arthroscopically Defined Acetabular Cartilage Defects and a Proposed Preoperative Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage Index in Hips of Patients With Femoroacetabular Impingement Syndrome

PURPOSE

To evaluate a delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) index designed to predict focal acetabular articular cartilage damage in patients with femoroacetabular impingement (FAI).

METHODS

The inclusion criteria were patients who underwent dGEMRIC and hip arthroscopy between April 2010 and August 2015 for FAI syndrome. The exclusion criteria were previous hip conditions, a Tönnis grade greater than 1, and a delay between magnetic resonance imaging and surgery greater than 180 days. The cutoff value for full-thickness chondral damage was set to 350 milliseconds. The coronal anterolateral (CAL) index was designed to evaluate focal articular anterolateral chondral defects. We calculated the binary classification test of the CAL index for full-thickness chondral damage, with arthroscopy as the gold standard. We calculated the correlation between the CAL index and the arthroscopically defined acetabular labrum articular disruption (ALAD) and Outerbridge grades and tested for differences between no or mild focal chondral damage and moderate or severe focal chondral damage. We repeated this analysis on the sagittal superior index, a combination of the sagittal anterior and posterior indices.

RESULTS

A total of 195 hips (183 patients) were reviewed. The CAL index showed a sensitivity of 55% (95% confidence interval [CI], 32%-76%), specificity of 81% (95% CI, 74%-86%), positive predictive value of 27% (95% CI, 18%-37%), and negative predictive value of 93% (95% CI, 90%-96%). The CAL index showed a significant difference between no or mild focal chondral damage and moderate or severe focal chondral damage per both ALAD and Outerbridge groups (P < .0001). The CAL index was moderately inversely correlated with ALAD and Outerbridge grades (ρ = -0.403, P < .0001). The sagittal superior index was not significantly different between the groups and showed a weak correlation with focal defects.

CONCLUSIONS

The CAL index may play a role in ruling out full-thickness articular cartilage defects in patients with FAI syndrome. In addition, it may help in differentiating between no or mild focal chondral damage and moderate or severe focal chondral damage.

LEVEL OF EVIDENCE

Level III, case-control study.

Comprehensive Clinical Evaluation of Femoroacetabular Impingement: Part 3, Magnetic Resonance Imaging

Radiologic imaging is an essential supplement to the physical examination in the evaluation of a patient with femoroacetabular impingement. Plain radiographs are the initial modality of choice for the evaluation of bony anatomy and pathology. Magnetic resonance imaging supplements the physical examination and standard radiographs by enabling qualitative and quantitative evaluation of both articular cartilage and soft tissues about the hip. Magnetic resonance imaging also provides improved 3-dimensional characterization of the bony anatomy owing to the multiplanar nature of this technique. This article describes a comprehensive approach to interpretation of magnetic resonance examination of the hip.