Diagnostic Utility of MRI and MR Arthrography for Detection of Ligamentum Teres Tears: A Retrospective Analysis of 187 Patients With Hip Pain

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1 Musculoskeletal Imaging Original Research Datir et al. MRI and MR for Ligamentum Teres Tears Musculoskeletal Imaging Original Research bhijit Datir 1 Minzhi Xing 1 Jian Kang 2 Paul Harkey 1 parna Kakarala 1 Walt. Carpenter 1 Michael R. Terk 1 Datir, Xing M, Kang J, et al. Keywords: ligamentum teres, MR arthrography, MRI, tear DOI: /JR Received November 12, 2013; accepted after revision January 2, Department of Radiology & Imaging Sciences, Musculoskeletal Division, Emory University Hospital, 59 Executive Park South, tlanta, G ddress correspondence to. Datir (adatir@emory.edu). 2 Department of iostatistics & ioinformatics, Emory University Hospital, tlanta, G. JR 2014; 203: X/14/ merican Roentgen Ray Society Diagnostic Utility of MRI and MR rthrography for Detection of Ligamentum Teres Tears: Retrospective nalysis of 187 Patients With Hip Pain OJECTIVE. The purpose of this study was to compare the diagnostic utility of MRI and MR arthrography for ligamentum teres tears in patients with hip pain. MTERILS ND METHODS. This is a retrospective study involving 187 patients who underwent MRI or MR arthrography for hip pain. This study included 103 male and 84 female patients with average age of 39 years. Three experienced musculoskeletal radiologists reviewed the MRI and MR arthrography studies to assess the ligamentum teres tears. The criteria for diagnosing normal or abnormal (i.e., ligament), partial or degenerative or complete tear of ligamentum teres were defined on the basis of several imaging characteristics. The MRI and MR arthrography results were correlated with arthroscopy, which served as the reference standard. Statistical analysis was performed to calculate the diagnostic yield, diagnostic accuracy, and diagnostic performance of MRI and MR arthrography in detecting partial or degenerative and complete ligamentum teres tears. Overall comparative performance of MRI and MR arthrography was assessed using Kruskal-Wallis test. RESULTS. For partial ligamentum teres tears, MRI showed lower sensitivity, specificity, and positive predictive value (0.41, 0.75, and 0.32, respectively) as compared to MR arthrography (0.83, 0.93, and 0.76, respectively), whereas the negative predictive value of MRI (0.82) was comparable to that of MR arthrography (0.95). No statistically significant difference (p < 0.05) could be identified between MRI and MR arthrography for diagnosing complete ligamentum teres tears. CONCLUSION. Hip MRI is equally suited for diagnosis of complete ligamentum teres tears when compared with MR arthrography. y contrast, for partial or degenerative ligamentum teres tears, MR arthrography offers the advantage of better arthroscopic correlation. T he ligamentum teres, also known as ligamentum capitis femoris, remains a matter of debate in the orthopedic literature, regarding its mechanical function and role in stabilization of the hip joint [1 3]. On the basis of biomechanical models and operative findings, it has been suggested that the ligamentum teres may contribute to hip joint stability. It has also been shown that the patients with complete ligamentum teres rupture may have hip joint laxity on dynamic arthroscopic assessment [4]. However, the precise role of the ligamentum teres during multiplanar positioning of the hip joint remains unknown. With advancements in hip arthroscopy over recent years, there has been increased interest in the assessment of functional status of the ligamentum teres in patients with hip pain. This has led to various classification systems for hip arthroscopy findings of ligamentum teres tears [5, 6]. During arthroscopy, patients with ligamentum teres injury may require débridement along with attention to associated findings such as labral tears and cartilage lesions [7, 8], but the need for arthroscopic débridement remains controversial in isolated ligamentum teres tears [5, 9, 10]. Recently, there has been emphasis on the imaging appearance of ligamentum teres on MR and CT arthrography [11]. MR arthrography is considered to be the reference standard for detection of ligamentum teres tears [1, 11]. Not only does MR arthrography detect complete ligamentum teres tears, but it also helps in identifying other, more common causes of hip pain. It has been suggested that the intact and partially torn ligamentum teres may have similar imaging findings on MR arthrography, making the diagnosis of partial ligamentum teres tears difficult [12]. 418 JR:203, ugust 2014

2 MRI and MR for Ligamentum Teres Tears The purpose of our study is to compare the diagnostic utility of MRI and MR arthrography in the diagnosis of ligamentum teres tears in patients with hip pain. ecause of optimal joint distention with contrast material, it seems logical for MR arthrography to have better diagnostic performance for evaluation of intraarticular abnormalities such as ligamentum teres tears. However, to our knowledge, the ability of MRI, as compared with MR arthrography, to diagnose ligamentum teres tears has not previously been described in the literature. Materials and Methods The present study was approved by the institutional review board and performed in compliance with HIP regulations. Patient informed consent was waived because this was a retrospective study. We collected data on patients who underwent MRI or MR arthrography of the hip joint from January 2010 to June 2013 at our tertiary orthopedic referral center. Patient Demographics This study included 187 consecutive patients with traumatic or nontraumatic hip pain. Of these, Fig year-old man with hip pain of 3 weeks duration and partial or degenerative ligamentum teres tear on hip MR arthrography. and, Coronal proton density weighted imaging with fat saturation () and axial oblique T1-weighted MR arthrography with fat saturation () sequences show attenuated ligamentum teres with frayed margins (arrows, and ) with intact attachments (arrowheads, ). This was confirmed on hip arthroscopy, which showed thinning and scarring of intact ligamentum teres. 103 were male and 84 were female patients (average age, 39 years; range, years). Sixty-three patients had trauma as a cause of hip pain, and 124 patients presented with nontraumatic hip pain. None of these patients had radiographic evidence of acute fracture or dislocation. Patients with prior hip surgery were excluded from the study. MRI Technique ll patients were imaged with a 3-T MR scanner (Signa HDx, GE Healthcare) using an eightchannel, phased-array surface coil. The imaging protocol for hip MRI included axial T1-weighted imaging (TR/TE, /4 8), axial proton density weighted imaging with fat saturation (TR/TE, /40 50), coronal T1-weighted imaging (TR/TE, /4 8), coronal proton density weighted imaging with fat saturation (TR/TE, /40 50), and sagittal proton density weighted imaging with fat saturation (TR/TE, /35 50) with the following parameters: matrix, ; FOV, cm; flip angle, 90 ; slice thickness, 3 mm; and interslice gap, 0.3 mm. Hip MR arthrography was performed after intraarticular injection of ml of a mixture of 2 mmol/l dilute gadolinium-based contrast agent (Multihance Fig year-old woman with hip pain of 4 months duration and partial or degenerative ligamentum teres tear on hip MRI. and, Coronal proton density weighted imaging with fat saturation () and axial proton density weighted imaging with fat saturation () sequences show thickened, heterogeneously hyperintense ligamentum teres (arrows, and ) with intact attachments. This was confirmed on hip arthroscopy, which showed swollen and frayed, but otherwise intact, ligamentum teres. [gadobenate dimeglumine 529 mg/ml], racco Diagnostics), iodinated contrast material (Isovue- M-300 [iopamidol 61%], racco Diagnostics), and anesthetic 1% Xylocaine (lidocaine hydrochloride, PP Pharmaceuticals) into the hip joint using standard technique. The imaging protocol for hip MR arthrography consisted of coronal T1-weighted imaging (TR/TE, /6 8), coronal T1-weighted imaging with fat saturation (TR/TE, /6 8), coronal proton density weighted imaging with fat saturation (TR/TE, /35 50), axial oblique T1-weighted imaging with fat saturation (TR/TE, /8 10), and sagittal T1-weighted imaging with fat saturation (TR/TE, /8 10) with the following parameters: matrix, ; FOV, cm; flip angle, 90 ; slice thickness, 3 mm; and interslice gap, 0.3 mm. The imaging studies were reviewed by an independent observer to exclude studies with motion degradation and suboptimal contrast injection. Review of MRI and MR rthrography Findings Three fellowship-trained musculoskeletal radiologists with 4, 6, and 24 years experience reviewed all hip MRI and MR arthrography studies independently. The radiologists were blinded to JR:203, ugust

3 Datir et al. Fig year-old woman with hip pain of 2 months duration and complete ligamentum teres tear on hip MR arthrography. and, Coronal proton density weighted imaging with fat saturation () and axial oblique T1-weighted MR arthrography with fat saturation () sequences show completely torn ligamentum teres from transverse ligament attachment (arrow, ) with nonvisualization in its inferior course. Few residual, attenuated fibers of ligamentum teres are seen proximally (arrowhead, ). This was confirmed on hip arthroscopy, which showed completely torn ligamentum teres with frayed, residual fibers. the clinical history, physical examination findings, and arthroscopy outcomes. The ligamentum teres was assessed with respect to size (normal, atrophic, hypertrophic, or absent), contour (smooth or frayed), signal characteristics (homogeneous or heterogeneous), foveal attachment (intact or disrupted), and transverse ligament attachment (intact or disrupted). The final radiologic diagnosis with regard to the ligamentum teres was categorized as: normal, partial or degenerative tear, complete tear, or indeterminate. The ligamentum teres was considered normal when the fibers were intact with normal insertion at ends, normal thickness, homogeneously hypointense signal intensity, and smooth margins. The diagnosis of partial or degenerative tear was made if the ligamentum teres was heterogeneous or hyperintense in signal intensity (or both), with or without frayed margins (Figs. 1 and 2). complete tear of the ligamentum teres was diagnosed if it was not seen in its normal expected location or was detached along its course or at the attachments from the fovea or transverse ligament (Figs. 3 and 4). The data were collected and reviewed with regards to the final imaging-based diagnoses for both modalities (hip MRI and MR arthrography). Studies with discrepancy in final diagnosis between three observers were rereviewed, and a consensus diagnosis was reached. rthroscopic Confirmation ll patients underwent hip arthroscopy after MRI or MR arthrography of the hip joint. The time interval between the hip MRI and arthroscopy ranged from 6 to 45 days. Hip arthroscopy was performed by two fellowship-trained orthopedic surgeons with a minimum of 5 years of experience each. The arthroscopy results for patients after MRI and MR arthrography were collected, and these were searched for assessment of ligamentum teres and compared with the final imaging diagnosis. rthroscopy reports without specific mention of the ligamentum teres were considered inconclusive for confirmatory diagnosis and were excluded from the study. Statistical nalysis ll statistical calculations were performed using SPSS (version 21.0, SPSS). The arthroscopic assessment was considered as the reference standard for diagnosing normal versus abnormal (partial or degenerative tear, or complete tear) ligamentum teres. Interobserver agreement for final diagnosis Fig year-old man with hip pain of 6 weeks duration and complete ligamentum teres tear on hip MRI. and, Coronal T1-weighted imaging () and coronal proton density weighted imaging with fat saturation () sequences show fat occupying acetabular fossa (arrows, and ) with complete absence of ligamentum teres in expected location. This was confirmed on hip arthroscopy with absent ligamentum teres. No residual ligamentum teres fragments were identified. by three reviewers on MRI and MR arthrography was calculated using Cohen s kappa coefficient. Diagnostic yield for MRI and MR arthrography was calculated as the number of imaging studies in which a definitive diagnosis with regard to the ligamentum teres was possible, divided by the total number that included studies with both indeterminate and definitive diagnoses. Diagnostic accuracy for MRI and MR arthrography was defined as the number of cases for which the imaging diagnosis matched that based on the arthroscopy results, divided by the total number of cases. Diagnostic performance of MRI and MR arthrography for partial or degenerative tear and complete tear was analyzed by calculating sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The comparative performance of MRI and MR arthrography for diagnosing partial or degenerative tear and complete tear was assessed using Kruskal-Wallis test. The criterion for statistical significance was p < 0.05, and the p value was not adjusted for multiple tests. Results total of 187 hip MRI and MR arthrography studies were reviewed. This included JR:203, ugust 2014

4 MRI and MR for Ligamentum Teres Tears patients (47 male and 35 female patients; average age, 43 years; age range, years) in the hip MRI category (Table 1), and the hip MR arthrography category (Table 2) included 105 patients (56 male and 49 female patients; average age, 28 years; age range, years). In the hip MRI category, a total of 22 partial and three complete ligamentum teres tears were diagnosed, and in the hip MR arthrography category, 25 partial and four complete ligamentum teres tears were diagnosed. In the hip MRI category (Table 1), we diagnosed 22 partial and 3 complete tears. Five cases of 82 were deemed to be indeterminate for ligamentum teres assessment by all three reviewers, and were excluded from the results. Fifty-two of the remaining 77 patients (82 minus 5) were diagnosed with normal ligamentum teres on MRI. Of these, 43 were confirmed to be normal on arthroscopy. The remaining nine patients had a partial or degenerative ligamentum teres tear on arthroscopy, which was not diagnosed on hip MRI. Twenty-two patients received a diagnosis of partial or degenerative tear on MRI; however, only 7 were confirmed on arthroscopy. Of the remaining 15 patients with partial or degenerative tear on MRI, 14 were found to have a normal ligamentum teres and one patient had a complete tear on arthroscopy. Three patients received a diagnosis of complete tear on MRI; of these, two were confirmed and one received a diagnosis of partial or degenerative tear on arthroscopy. In the hip MR arthrography category (Table 2), 72 patients had an arthroscopically confirmed normal ligamentum teres. Four partial or degenerative ligamentum teres tears seen on arthroscopy were not detected and diagnosed as normal on hip MR arthrography. Of 25 partial/degenerative ligamentum teres tears on MR arthrography, nineteen were confirmed on arthroscopy. There were 2 arthroscopically confirmed complete ligamentum teres tears, which were diagnosed as partial/degenerative tear on hip MR arthrography. Four patients with complete ligamentum teres tear on MR arthrography were confirmed on arthroscopy. The interobserver agreement was calculated for final diagnoses using Cohen s kappa coefficient. This showed fair agreement for diagnoses made on MRI for ligamentum teres (κ = 0.344). However, there was substantial agreement for the diagnoses made on MR arthrography (κ = 0.728). The reviewers were able to make an imaging diagnosis for ligamentum teres in all TLE 1: MRI ssessment of Ligamentum Teres With rthroscopic Confirmation rthroscopic Diagnosis Normal Ligament MR arthrography studies (i.e., no indeterminate outcome), thereby leading to a diagnostic yield of 100%. In the MRI category, five studies were deemed to be indeterminate for ligamentum teres assessment. This led to the diagnostic yield of 93.9% (77/82). Similarly, the diagnostic accuracy for hip MRI was 67.5% (52/77), and for hip MR arthrography was 90.5% (95/105). s shown in Table 3, the sensitivity and specificity of hip MRI for diagnosing partial/degenerative ligamentum teres tears was 0.41 and 0.75, respectively. This was in contrast with the ability of hip MR arthrography MRI Diagnosis Partial or Degenerative Tear Complete Tear Normal ligament Partial or degenerative tear Complete tear Note Data are number of ligaments. TLE 2: MR rthrographic ssessment of Ligamentum Teres With rthroscopic Confirmation rthroscopic Diagnosis Normal Ligament MR rthrographic Diagnosis Partial or Degenerative Tear Complete Tear Normal ligament Partial or degenerative tear Complete tear Note Data are number of ligaments. TLE 3: Diagnostic Performance of MRI and MR rthrography for Partial or Degenerative and Complete Ligamentum Teres Tears Parameter Partial or Degenerative Tear Complete Tear MRI MR rthrography MRI MR rthrography Sensitivity 0.41 (7/17) 0.83 (19/23) 0.67 (2/3) 0.67 (4/6) Specificity 0.75 (45/60) 0.93 (76/82) 0.99 (73/74) 1.00 (99/99) Positive predictive value 0.32 (7/22) 0.76 (19/25) 0.67 (2/3) 1.00 (4/4) Negative predictive value 0.82 (45/55) 0.95 (76/80) 0.99 (73/74) 0.98 (99/101) TLE 4: Comparative nalysis of Diagnostic Performance for MRI Versus MR rthrography in Detecting Partial or Degenerative and Complete Ligamentum Teres Tears Using Kruskal-Wallis Test (p < 0.05) Type of Tear Sensitivity Specificity Positive Predictive Value Negative Predictive Value Partial or degenerative Complete to diagnose partial/degenerative ligamentum teres tear with higher sensitivity (0.83) and specificity (0.93). MR arthrography was able to diagnose complete ligamentum teres tear in all cases (PPV = 1, NPV = 0.98), whereas MRI showed lower sensitivity (0.67) but higher specificity (0.98) for the same (PPV = 0.67, NPV = 0.99) (Table 3). The comparative performance of MRI versus MR arthrography was assessed with Kruskal-Wallis test for diagnosing partial or degenerative tear and complete tear. This showed a significant difference (p < 0.05) in sensitivity (0.007), specificity (0.003), JR:203, ugust

5 Datir et al. PPV (0.003), and NPV (0.014) between MRI and MR arthrography for diagnosis of partial or degenerative ligamentum teres tears. However, for diagnosis of complete ligamentum teres tears, there was no significant difference between the abilities of MRI and MR arthrography (Table 4). Discussion The arthroscopy and surgery literature on ligamentum teres continues to grow [1, 3 5]. However, there is little agreement on the function and role of the ligamentum teres. It has been suggested that the ligamentum teres is a strong stabilizing structure that plays an important role during hip adduction, flexion, and external rotation [13]. With regards to ligamentum teres morphology, variation in the number of ligamentum teres bundles has been described (two vs three) [14]. The length of the ligamentum teres has also been shown to be variable, ranging from 30 to 35 mm [15]. ased on experience with open surgical dislocations that require transection of ligamentum teres, some surgeons believe that the ligamentum teres has a negligible role. y contrast, others emphasize the role of the ligamentum teres in normal hip biomechanics and stability, thereby warranting its reconstruction [16]. clinical diagnosis of ligamentum teres tear remains challenging, because there are no specific signs for this entity on physical examination [3, 4, 13, 17]. lthough patients usually describe hip and groin pain, locking, and catching, these symptoms are nonspecific and may be seen in other intraarticular conditions. lso, there remains controversy on the treatment of ligamentum teres tears, with options ranging from débridement to reconstruction [16]. Recent radiology literature has described the imaging appearance of ligamentum teres on MR and CT arthrography [11, 12]. s described by lankenbaker et al. [12], the diagnosis of partially torn ligamentum teres remains challenging on MR arthrography. Several features on MR arthrography have been described to diagnose partial ligamentum teres tears that may help in establishing a diagnosis. MR arthrography has the advantage of joint distention with contrast material, which may help in diagnosing ligamentum teres tears. In routine practice, most ligamentum teres pathologies are seen as incidental and unexpected findings on MRI studies. Very often we have encountered situations in which ligamentum teres pathologies are seen in nonarthrographic MRI studies. We believe that it is important to know the diagnostic utility of MRI versus MR arthrography in diagnosing ligamentum teres tears. Not only will this help in avoiding unnecessary intervention and imaging, but it will also guide the referring physician in dealing with such pathologies. In our study, MRI was able to correctly diagnose normal ligamentum teres in 43 of 52, compared to 72 of 76 on MR arthrography. Nine partial tears were underdiagnosed on MRI, compared with four on MR arthrography. For partial tears confirmed on arthroscopy in the hip MRI category, only seven of 22 were correctly diagnosed on MRI. In contrast, MR arthrography diagnosed 19 of 25 partial tears that were later confirmed arthroscopically. This shows that MR arthrography has a higher diagnostic performance for identifying partial or degenerative ligamentum teres tears when compared with MRI. The PPV of 0.32 and NPV of 0.82 for MRI to diagnose partial or degenerative ligamentum teres tear (compared with 0.76 and 0.95, respectively, for MR arthrography) shows that MRI is better suited to rule out a partial or degenerative tear rather than confirming one. Our results are comparable to those of lankenbaker et al. [12], who showed that MR arthrography was able to diagnose five to eight of 12 partial ligamentum teres tears. We believe that the underdiagnosis of partial ligamentum teres tears on MRI could be due to a combination of several factors including (but not limited to) the following: poor visualization in a nondistended joint; variation in the ligamentum teres bundle anatomy; overlap in the imaging appearance of the intact and partially torn ligamentum teres; and very small tears. With regards to complete ligamentum teres tears, MRI correctly diagnosed two of three cases with arthroscopic confirmation. lso, four of four arthroscopically proven complete ligamentum teres tears were correctly diagnosed by MR arthrography. This yields a strong PPV and NPV for both MRI and MR arthrography in diagnosing complete ligamentum teres tears. In MR arthrography, this can be explained on the basis that it is easier to identify nonvisualization of ligamentum teres in an optimally distended and contrastopacified hip joint. However, having similar strong correlation between MRI and arthroscopy in diagnosis of complete ligamentum teres tears suggests that MR arthrography is not necessarily needed to make this diagnosis. lthough the ligamentum teres is better visualized in a contrast-distended joint, the other factors mentioned earlier in this article could still play a role in underdiagnosis of partial ligamentum teres tears. Our study is different than previous studies in the radiology literature on ligamentum teres in several respects. We compared MRI versus MR arthrography in their diagnostic utility for ligamentum teres tears. To our knowledge, such comparative analysis has not been performed in the radiology literature. We did not attempt to measure the size of the ligamentum teres in our study for several reasons. First, there is no consensus for the normal size range of the ligamentum teres in the arthroscopy or radiology literature. Second, the ligamentum teres follows a complex course during flexion and abduction of the lower limb [18]. ecause the ligamentum teres forms a slinglike structure to support the femoral head inferiorly during hip motion, accurate measurements of the ligamentum teres not only are difficult to obtain and reproduce but also possess very little diagnostic value in our opinion. Last, because of its oblique orientation and pyramidal shape [1], it is difficult to form a stable, reproducible anatomic landmark for measurement. ecause of this complex 3D orientation and its multiple fiber bundles, we agree with other authors [11, 12] that coronal, axial, and axial oblique planes are helpful for precise assessment of the ligamentum teres. However, we did not separate partial ligamentum teres tears from degenerative ones and have grouped them as one category in this study. This is because there are no reliable imaging features to separate these entities. lso, in the arthroscopy literature, the most agreed treatment of these diagnoses, if any, seems to be the surgical débridement alone. t our institution, both partial and degenerative ligamentum teres tears are managed with arthroscopic débridement, and no additional benefit could be gained in separating these diagnoses. The limitations of our study include a small patient population and retrospective evaluation. We did not perform clinical outcome follow-up in these patients after arthroscopic treatment. lso, no attempt was made to classify the ligamentum teres tears by traumatic or nontraumatic cause. In addition, we did not evaluate the presence of additional intraor extraarticular findings on MRI or MR arthrography. s mentioned earlier, the size of ligamentum teres was deliberately not included in this study. Conclusion Hip MRI is equally suited for diagnosis of complete ligamentum teres tears when com- 422 JR:203, ugust 2014

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