The Diagnostic Value of Ultrasound in Anterosuperior Acetabular Labral Tear Guanying Gao, M.D., Qiang Fu, M.D., Ligang Cui, M.D., and Yan Xu, M.D.
Purpose: To investigate diagnostic value of ultrasound in acetabular labral tears compared with magnetic resonance (MR) imaging, using arthroscopic surgery as the gold standard in a relatively large sample size. Methods: We retrospectively evaluated patients who attended the sports medicine clinic of our department and underwent arthroscopic surgery for the diagnosis of an anterosuperior acetabular labral tear between June 2014 and April 2018. All the patients received hip joint ultrasound examination and MR imaging evaluation before arthroscopic surgery. The sensitivity, speciﬁcity, and accuracy of ultrasound and MR imaging were calculated and compared. Results: A total of 195 patients were enrolled in this study. Of these, 184 had arthroscopically conﬁrmed anterosuperior acetabular labral tear. The sensitivity, speciﬁcity, positive predictive value (PPV), negative predictive value, and accuracy by ultrasound were, respectively, 68.5%, 81.8%, 98 4%, 13.4%, and 69.2%, retrospectively. For MR imaging, the sensitivity, speciﬁcity, PPV, negative predictive value, and accuracy were 84.8%, 63.6%, 97.5%, 20.0%, and 83.6%, respectively. Conclusions: Although ultrasound had a slightly lower sensitivity for detecting anterosuperior acetabular labral tear, it had a higher speciﬁcity and PPV than MR imaging. With the advantages of being inexpensive, relatively quick, noninvasive, and having dynamic evaluation, ultrasound could be used as a feasible method to evaluate anterosuperior acetabular labral tear. Level of Evidence: Level IV, case series.
cetabular labral tear is 1 of the most common causes of hip joint pain.1 About 22% to 55% of patients with hip and groin pain have acetabular labral tear, many of which are often secondary to acetabular dysplasia or femoroacetabular impingement (FAI) syndrome.2,3 Arthroscopic surgery is regarded as the gold standard for diagnosing acetabular labral tear and magnetic resonance (MR) imaging is a sensitive imaging technique to evaluate the acetabular labrum other than
From the Institute of Sports Medicine (G.G., Y.X.), Peking University Third Hospital, Beijing China; and Department of Ultrasound (Q.F., L.C.), Peking University Third Hospital, Beijing, China. Guanying Gao and Qiang Fu contributed equally to this work. The authors report the following potential conﬂicts of interest or sources of funding: The work was supported by grant from the National Natural Science Foundation of China (No. 81672182). Full ICMJE author disclosure forms are available for this article online, as supplementary material. Received October 30, 2018; accepted February 22, 2019. Address correspondence to Yan Xu, M.D., Institute of Sports Medicine, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, China. E-mail: [email protected]
; Ligang Cui, M.D., Department of Ultrasound, Peking University Third Hospital, 49 North Garden Road, Haidian District, Beijing 100191, China. E-mail: [email protected]
pku.edu.cn Ó 2019 by the Arthroscopy Association of North America 0749-8063/181293/$36.00 https://doi.org/10.1016/j.arthro.2019.02.052
bony abnormalities and cartilage changes.4 Most people, however, would use an MR arthrogram to diagnose acetabular labral tears. Chopra et al.5 evaluated 68 consecutive patients who had clinical FAI syndrome and underwent both 1.5T MR arthrogram and 3T MR imaging; 2 musculoskeletal radiologists reported higher sensitivities for detecting labral tears with the 3T MR imaging than the 1.5T MR arthrogram. They suggested that conventional 3T MR imaging may be at least equivalent to 1.5T MR arthrogram in detecting the acetabular labrum and possibly superior to 1.5T MR arthrogram in detecting cartilage defects in patients with suspected FAI syndrome. MR arthrogram also has the disadvantages of being invasive and expensive and carries the risk of allergy. In this study, we used MR imaging as the contrast of ultrasound; however, an MR imaging scan is expensive, time-consuming, and unsuited for claustrophobic patients; those ﬁtted with electronic equipment; or those with metallic foreign body implants. In contrast, ultrasound is inexpensive, relatively quick, and noninvasive; however, related research is quite scarce. Previous studies about the use of ultrasound to diagnose acetabular labral tears had insufﬁcient sample size and only some of them were performed with surgical conﬁrmation.4,6
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 35, No 9 (September), 2019: pp 2591-2597
G. GAO ET AL.
Fig 1. A normal triangular-shaped hyperechoic acetabular labrum (left side; white arrows) between the femoral head and acetabulum in a transverse oblique plane parallel to the axis of the femoral neck.
Ultrasound Examination Ultrasound examinations were performed by a single radiologist, blinded to the results of MR imaging, who specializes in musculoskeletal disorders with more than 10 years of experience. The patient was in the supine neutral position with the hip in slight external rotation and abduction. The acetabular roof, articular capsule, acetabular labrum, and femoral head and neck were identiﬁed by the longitudinal images obtained in a transverse oblique plane parallel to the axis of the femoral neck (Fig 1). The transducer was then moved across the hip joint medially and laterally for evaluation of the acetabular labrum in the anterior quadrant of the hip. Dynamic examinations of the hip in passive ﬂexion (0 to 90 ), adduction (0 to 20 ), and internal rotation (0 to 30 ) were performed to evaluate acetabular labrum and mutual position relationship of the femoral head, femoral neck, and labrum (Fig 2).4,8 The total time taken for the ultrasound examination of 1 hip ranged from 5 to 10 minutes.
The purpose of this study was to investigate the diagnostic value of ultrasound in acetabular labral tears compared with MR imaging, using arthroscopic surgery as the gold standard in a relatively large sample size. We hypothesized that ultrasound has high sensitivity, speciﬁcity, accuracy, and positive predictive value (PPV) to diagnose anterosuperior acetabular labral tear.
Methods Patients We retrospectively evaluated patients who attended the sports medicine clinic of our department and underwent arthroscopic surgery for the diagnosis of anterosuperior acetabular labral tear between June 2014 and April 2018. The inclusion criteria were as follows: (1) patients who preoperatively underwent both ultrasound examination and MR imaging preoperatively and had conﬁrmed anterosuperior acetabular labral tear, for which they then underwent arthroscopic surgery; and (2) no ﬁndings of labral tears on ultrasound examination or MR imaging, but patients were recommended to undergo an arthroscopic examination as a deﬁnite diagnostic procedure for ﬁnding the cause of the persistent hip pain. Patients with previous hip surgery were excluded from this study. All patients underwent ultrasound examination and MR imaging before arthroscopic surgery. Twenty patients in this study were also included in our prior study.7 The ultrasound examination and MR imaging scans of these 20 patients were analyzed by the corresponding authors of this study. The ﬁrst author assessed all patients and their credentials. All participants signed informed consent forms. The Ethics Committee of the Third Hospital of Peking University approved this study.
Fig 2. Acetabular labral tear before and after dynamic examination (right side). (A) Ultrasound examination shows no acetabular labral tear before dynamic examination (white arrow). (B) Ultrasound examination shows the presence of acetabular labral tear with anechoic cleft (white arrow) after dynamic examination.
ULTRASOUND FOR ANTEROSUPERIOR ACETABULAR LABRAL TEAR
articular cartilage, and ligamentum teres. The presence or absence of anterosuperior labral tears at the 11- to 3-o’clock positions were recorded using a clock-face system. Labral repair or labral debridement was performed according to the nature of injury. Femoral osteoplasty and acetabuloplasty were performed to treat FAI syndrome.
Fig 3. Acetabular labral tear with the plump morphology and heterogeneous echogenicity (right side; white arrow).
MR Imaging Unlike our prior study in which MR imaging scans were evaluated by different authors,7 only one radiologist specializing in musculoskeletal disorders and with 10 years of experience in musculoskeletal radiology analyzed all MR imaging scans and was blinded to the results of the ultrasound exam. The hip MR examinations were performed with a 3.0 T MR scanner (Magnetom Trio with TIM system, Siemens Healthcare) and a dedicated ﬂexible surface coil around the affected hip joint. Patients were in the supine position. Conventional MR imaging of the affected hip joint was then obtained. Fat-suppressed turbo spin-echo intermediateand T2-weighted sequences were performed separately in the axial, oblique transverse, and oblique coronal planes using following parameters: repetition time, 3000 ms; echo time, 32 ms and 76 ms; ﬁeld of view, 180 mm 180 mm; slice thickness, 3.0 mm; slice gap, 0.3 mm; and a 256 230 matrix. Imaging in the oblique transverse plane was performed parallel to the axis of the femoral neck, whereas that in the oblique coronal plane was performed perpendicular to the line through the anterior and posterior acetabulum edge on the axial images. Turbo spin-echo T1-weighted sequence was also obtained routinely in the oblique coronal plane with the following parameters: repetition time, 820 ms; echo time, 10 ms; ﬁeld of view, 180 mm 180 mm; slice thickness, 3.0 mm; slice gap, 0.3 mm; and a 256 230 matrix. The total time taken for MR imaging of 1 hip ranged from 30 to 35 minutes. Arthroscopic Surgery Hip joint arthroscopy was performed by 1 surgeon with more than 10 years of experience. All patients underwent standard hip joint arthroscopy. A detailed inspection of the central compartment was performed to assess the acetabular rim, acetabular labrum,
Criteria for Acetabular Labral Tear Criteria for acetabular labral tear in ultrasound examination were as follows: (1) plump morphology with heterogeneous echogenicity (Fig 3); (2) absence of labrum with focal patchy hyperecho; (3) deﬁnite hypoechoic cleft or anechoic cleft through the base of the labrum or extending to the articular surface of the labrum (Fig 4); and (4) acetabular paralabral cyst (Fig 5).8 The criteria for acetabular labral tear in MR imaging were as follows: (1) abnormal high signal at the basal or internal labrum reaching the articular surface; (2) a clear separation of the labrum from the acetabular edge; or (3) an irregular shape of the acetabular labrum.9 Statistics Sensitivity, speciﬁcity, accuracy, PPV, negative predictive value (NPV), and accuracy of ultrasound and MR imaging were calculated. Independent sample t and c-square tests were used to compare mean body mass index (BMI) and gender between patients who were misdiagnosed and correctly diagnosed by ultrasound. P values <.05 were considered statistically signiﬁcant. All statistical analyses were performed with SPSS Statistics, version 22 (IBM).
Results Patient Demographics In this retrospective study, we initially analyzed 227 patients, of whom 32 were excluded. As shown in
Fig 4. An acetabular labral tear with anechoic cleft throughout the base of the labrum (left side; white arrow).
G. GAO ET AL. Table 2. Comparison Between Ultrasound and Arthroscopy Ultrasoundþ Ultrasounde Total
Fig 5. Acetabular labral tear with irregular anechoic acetabular paralabral cyst (right side; white arrows).
Table 1, a total of 195 patients (mean age, 36.2 9.6 years; age range, 13-60 years; 87 male and 108 female) were included for the ﬁnal analysis. There were 89 left hips and 106 right hips. The BMI was 23.7 (range, 18.5-27.2). Diagnosis before surgery was shown in Table 1. Eighteen patients with negative results on both ultrasound and MR imaging were recommended to have an arthroscopic examination as a deﬁnite diagnostic procedure to ﬁnd the cause of persistent hip pain. We compared BMI and gender between patients who were misdiagnosed and correctly diagnosed by ultrasound and found no signiﬁcant difference (P > .05). Comparison Between Ultrasound and Arthroscopy As shown in Table 2, arthroscopy conﬁrmed the presence of anterosuperior acetabular labral tear in 184 (94.4%) patients and the absence of 1 in 11 (5.6%) Table 1. Patients’ Demographic Data (n ¼ 195) Parameter Age, y, mean (SD) Sex Male Female Side Left Right BMI, mean (SD) Diagnosis before surgery Acetabular labral tear Cam deformity Pincer deformity Hip dysplasia Osteoid osteoma Synovitis
Data 36.2 9.6 (13-60) 87 (44.6) 108 (55.4) 89 (45.6) 106 (54.4) 23.7 (18.5-27.2) 177 132 112 8 2 2
(90.8) (67.7) (57.4) (4.1) (1.0) (1.0)
NOTE. Unless otherwise speciﬁed, data are numbers of patients, with percentages in parentheses.
Arthroscopyþ 126 58 184
Arthroscopye 2 9 11
Total 128 67 195
patients. Among the 11 patients without acetabular labral tear, 5 had osteoarthritis, 4 had synovitis, 1 had synovial chondromatosis, and 1 had gluteus contracture. Three posterior labral tears were identiﬁed on arthroscopy. In all, 135 (69.2%) of the 195 patients were correctly diagnosed by ultrasound, including 126 with anterosuperior acetabular labral tears and 9 without tears using ultrasound. Forty (29.6%) of those 135 patients were diagnosed by dynamic examinations. Of the remaining patients, 2 had false-positive tears and 58 had false-negative tears. The sensitivity, speciﬁcity, PPV, NPV, and accuracy by ultrasound were respectively 68.5%, 81.8%, 98.4%, 13.4%, and 69.2%, retrospectively. Comparison Between MR Imaging and Arthroscopy Of the 195 patients, 163 (83.6%) were diagnosed correctly by MR imaging, including 156 with anterosuperior acetabular labral tears and 7 without. Of those, 4 were false-positive and 28 were false-negative tears. The results are presented in Table 3. For MR imaging, the sensitivity, speciﬁcity, PPV, NPV, and accuracy were, respectively, 84.8%, 63.6%, 97.5%, 20.0%, and 83.6%, retrospectively. Comparison Between Ultrasound and MR Imaging The results of comparison between ultrasound and MR imaging are presented in Table 4. The results of ultrasound and MR imaging were identical in 129 of the 195 patients. A total of 111 of the 129 patients were diagnosed by both ultrasound and MR imaging, and 11 of the 129 patients had no tears on either ultrasound or MR imaging. The results of ultrasound and MR imaging were inconsistent in 66 of the 195 patients. Twentynine of the 66 patients were diagnosed as having anterosuperior acetabular labral tear by ultrasound, but MR imaging found no evidence of tear (Fig 6), and 37 of the 66 patients were diagnosed as having anterosuperior acetabular labral tear by MR imaging, but not ultrasound. Table 3. Comparison Between MR Imaging and Arthroscopy MR imagingþ MR imaginge Total
Arthroscopyþ 156 28 184
MR, magnetic resonance.
Arthroscopye 4 7 11
Total 160 35 195
ULTRASOUND FOR ANTEROSUPERIOR ACETABULAR LABRAL TEAR Table 4. Comparison Between Ultrasound and MR Imaging MR imagingþ MR imaginge Total
Ultrasoundþ 111 29 140
Ultrasounde 37 18 55
Total 148 47 195
MR, magnetic resonance.
Discussion Our results showed that ultrasound had a higher speciﬁcity and PPV than MR imaging and slightly lower sensitivity for detecting anterosuperior acetabular labral tears. Acetabular labral tears have been reported as an important cause of hip pain in many patients and are frequently found in patients with FAI syndrome.10,11 MR imaging is now routinely used to assess both bone and soft-tissue structures in patients with hip pain or dysfunction and is considered an important evaluation tool for acetabular tear.9,12 MR arthrogram is another option for diagnosing acetabular labral tears owing to its high accuracy13; however, we do not use MR arthrogram regularly because of its invasive nature, high cost, and risk of allergies. In addition, outpatients are always hesitant to undergo invasive examinations. Furthermore, we found that the effect of tissue edema and soft tissue observed by MR arthrogram is inferior to that observed by MR imaging. Chopra et al.5 evaluated 68 consecutive patients with clinical FAI syndrome and concluded that conventional 3T MR imaging may be at least equivalent to 1.5T MR arthrogram in detecting acetabular labrum and likely superior to 1.5T MR arthrogram in detecting cartilage defects in patients with suspected FAI syndrome. Magee14 evaluated 43 conventional MR imaging scans and MR arthrograms on patients with hip pain who underwent subsequent arthroscopy and concluded that 3.0T MR imaging demonstrated sensitivity for detection of acetabular labral tears that was comparable to the sensitivity of 3.0T MR arthrogram of the hip. We therefore use MR imaging instead of MR arthrogram in our practice. An MRI scan, however, is expensive, timeconsuming, and unsuited for claustrophobic patients, those ﬁtted with electronic equipment, or those with metallic foreign body implants.15 In contrast, ultrasound is inexpensive, relatively quick to perform, noninvasive, and has hence attracted increasing attention in recent time. Dynamic examination by ultrasound is another advantage that can improve diagnostic value. Ultrasound can also be used in patients with symptomatic hip dysplasia or FAI syndrome.16-18 This retrospective study focused on the diagnostic value of ultrasound in acetabular labral tears with arthroscopic ﬁndings. Only a few studies have assessed the efﬁcacy of ultrasound in diagnosing acetabular labral tears. In a study by Mitchell et al.,6 a labral tear was found in the 8
included patients by use of ultrasound, with a reported sensitivity and speciﬁcity of 13% and 100%, respectively. In another study by Sofka et al.,19 21 patients underwent ultrasound examination and showed evidence of labral tears were found in 13 (61.9%) patients. They also reported improvement in visualization of labral injuries following intra-articular injections. Troelsen et al.15 assessed the ability of ultrasound examination to diagnose acetabular labral tears in 20 hip joints by using MR imaging as a diagnostic gold standard and reported a sensitivity, speciﬁcity, PPV, and NPV of 44%, 75%, 88%, and 25%, respectively, for the ability of ultrasound in diagnosis of labral tears. After 2 years, in a similar study, Troelsen et al.8 reported both sensitivity and PPV of 94% for ultrasound in diagnosing labral tears using MR arthrography as a diagnostic gold standard in 18 patients. No true negatives, deﬁned as the absence of a labral tear in both ultrasound and MR arthrography, were found; thus, the speciﬁcity and NPV were not assessed. Improvements in diagnostic ability show that the experience of the sonographer and a learning curve are both important for accurate diagnosis of the acetabular labral tear; however, arthroscopic
Fig 6. (A) Acetabular labral tear with heterogeneous echogenicity (left side; white arrow). (B) Magnetic resonance imaging shows no obvious acetabular labral tear in the same patient (left side; white arrow).
G. GAO ET AL.
conﬁrmation for the presence of tears was not performed in conjunction with ultrasound examination. Jin et al.4 performed a comparison study between ultrasound and arthroscopic correlation in 16 symptomatic patients and reported a sensitivity, speciﬁcity, PPV, and NPV of 82%, 60%, 82%, and 60%, respectively, in the diagnosis of anterosuperior labral tears by ultrasound using arthroscopic results as the gold standard. Jung et al.20 reported that the sensitivity, speciﬁcity, and accuracy of ultrasound examination of labral tears, using arthroscopic surgery as gold standard, before and after injection were 58% versus 79%, 67% versus 58%, and 61% versus 72%, respectively, for observer 1 and 75% versus 92%, 25% versus 42%, and 58% versus 75%, respectively, for observer 2. Reiman et al.21 conducted a systematic review and found that the speciﬁcity and diagnostic odds ratio of ultrasound examination were higher than MR imaging (1.5T). In our prior study,7 we compared the ability of ultrasound and MR imaging to diagnose anterosuperior acetabular labral tears in 102 patients by using arthroscopic surgery as the gold standard and reported a sensitivity, speciﬁcity, PPV, and NPV of 65.93%, 81.82%, 96.77%, and 22.50%, respectively, for the ability of ultrasound in diagnosis of labral tears. However, the MR imaging scans in our prior study were not analyzed by only one author, which we thought was a big limitation and would result in bias. Twenty patients in this study were also included in our prior study.7 We did not include the data analyzed by other authors in the prior study and only included data analyzed by the corresponding authors of this study in our new study. Ultrasound examinations were performed by one of the corresponding authors of this study, blinded to the results of MR imaging, and MR imaging scans were analyzed by the other corresponding author, blinded to the results of ultrasound. In the past two years, we have accumulated more experience and improved the technology of ultrasound in diagnosing acetabular labral tears. In this study, we focused on ultrasound examination to diagnose anterosuperior labral tears with arthroscopic surgical conﬁrmation. The sensitivity, speciﬁcity, PPV, NPV, and accuracy of ultrasound in this study were respectively 68.5%, 81.8%, 98.4%, 13.4%, and 69.2%, retrospectively. The sensitivity in this study was higher than that reported by Troelsen et al.,15 but lower than that reported by Jin et al.4 and the later study by Troelsen et al.8 The speciﬁcity and PPV were higher than those reported by Jin et al.4 and Troelsen et al.,8,15 however. Troelsen et al.8 reported the sensitivity of ultrasound to be 94% in diagnosing labral tears; however, their study included 18 patients that underwent previous periacetabular osteotomies and used MR arthogram as the gold standard as against our study, which included 195 patients with no previous hip surgery and used
arthroscopy as the gold standard. The lower sensitivity in this study could be attributed to differences in sample size and diagnostic gold standards and the experience of the sonographer. The number of patients involved in previous studies ranged from 8 to 21. In contrast, our study included a considerably large sample size (n ¼ 195), and every patient underwent arthroscopy as a gold standard. Nonetheless, a larger sample size and surgical conﬁrmation may better demonstrate the diagnostic value of ultrasound for acetabular labral tears. The very high PPV in this study indicates a high likelihood that an acetabular labral tear is present if diagnosed by sonography. Ultrasound for diagnosing anterosuperior labral tears is still to be developed and further studies should be conducted to prove the diagnostic value of ultrasound. Limitations Our study has some limitations. First, complete evaluation of around-the-clock positions in the acetabular labrum was not performed, and only anterosuperior (from 11- to 3-o’clock) labral tears were evaluated. Compared with MR imaging, ultrasound does not provide the same complete visualization of the acetabular labrum. Only the part of the labrum corresponding to approximately 10- to 3-o’clock can be sufﬁciently visualized; however, almost all labral tears associated with hip dysplasia or FAI syndrome are found in this area.10,15,22 In our study, most labral tears (98.4%) were located in the anterosuperior portion of the hip. Only 3 posterior labral tears were seen in the hips on arthroscopy. Second, the number of patients without tears is relatively low in this study, which may have inﬂuenced the results of high PPV and speciﬁcity. This is a limitation that can hardly be performed with gold standard arthroscopy in patients without tear in imaging tests, however. Third, nonarthrogram MR used in this study is a potential limitation because MR imaging may not be as accurate as MR arthrogram in the diagnosis of labral tear. As explained earlier, we avoid regular use of MR arthrogram because of its invasive nature, high cost, and risk of allergies. We believe that MR imaging can also provide a sufﬁciently accurate diagnosis. Last, we did not calculate the inter- and intra-observer error, because the ultrasound examination and MR imaging were evaluated by a single experienced radiologist.
Conclusion Although ultrasound had a slightly lower sensitivity for detecting anterosuperior acetabular labral tear, it had a higher speciﬁcity and PPV than MR imaging. With the advantages of being inexpensive, relatively quick, noninvasive, and providing dynamic evaluation, ultrasound could be used as a feasible method to evaluate anterosuperior acetabular labral tear.
ULTRASOUND FOR ANTEROSUPERIOR ACETABULAR LABRAL TEAR
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