Background: Hip arthroscopy has led to a greater understanding of intra-articular hip pathology. Non-contrast magnetic resonance imaging (MRI) is currently the gold standard in non-invasive imaging diagnosis, with high sensitivity in identifying labral pathology but equivocal results for ligamentum teres damage and chondral defects. The aim of this study is to determine the accuracy of non-contrast MRI for diagnosis of intra-articular hip derangements and identify radiological features that could increase the accuracy of the diagnosis. Methods: A prospective study of 71 hips on 68 patients undergoing hip arthroscopy was conducted comparing pre- operative analysis of MRI imaging versus an arthroscopic examination. Two musculoskeletal radiologists reported the data independently. All hip arthroscopies were performed by a single surgeon. Patients with MRIs performed within 6 months before hip arthroscopy were included. Outcome measures included observer accuracy identifying ligamentum teres tears, labral lesions, and chondral rim damage. Secondary outcome measures included inter-observer variability and correctly staged ligamentum teres tears. Results: The accuracy of radiology reporting for ligamentum teres tears, labral damage, and chondral rim lesions was 85.92% for each instance. The MRI findings most consistent with labral tears include the presence of linear high signal traversing the articular surface into the labrum, presence of intra-labral fluid signal, and loss of homogenous low signal triangular morphology. Chondral rim damage was difficult to diagnose, but abnormal signal at the chondrolabral junction with partial thickness defects would suggest damage. Ligamentum teres tears are commonly found but poorly graded. Thickening and increased signal suggests synovitis while discontinuity and fraying suggests partial tearing. Conclusion: Conventional non-arthrographic MRI offers an accurate non-invasive method to screen patients with symptoms referable to the hip by revealing the presence of labral tears, chondral defects, and ligamentum teres tears/ synovitis. This study demonstrates that tears and synovitis of the ligamentum teres as potential sources of hip pain can be accurately identified on conventional non-arthrographic MRI. However, MRI has poor specificity and negative predictive value, and thus, a negative MRI result may warrant further investigation. Keywords: Hip arthroscopy, Ligamentum teres, MRI, Magnetic resonance imaging Background lesions [1, 2]. Magnetic resonance arthrography (MRA) Hip pain in young adults can be a difficult clinical diag- has been shown to be more sensitive than conventional nosis. Common symptom generators include acetabular MRI but can be less specific and has recognised risks as labral tears, ligamentum teres tears, and chondral dam- an invasive procedure [3–5]. age. Conventional non-invasive imaging of the hip has a The acetabular labrum is a fibrocartilaginous ring that varied ability to detect lesions of the hip. Magnetic res- surrounds the bony acetabulum and blends inferiorly with onance imaging (MRI) has been shown to be more sen- the transverse acetabular ligament. It increases the joint sitive and specific than other non-invasive imaging surface area by adding depth to the acetabulum, and techniques for the identification of ligamentum teres thereby reduces mechanical stress on the articular cartilage. Younger individuals have a triangular labrum with * Correspondence: firstname.lastname@example.org sharply defined margins and homogeneous low signal Department of Orthopaedics, Western Health, 160 Gordon Street, Footscray, that undergoes a progressive change in morphology, Melbourne, VIC 3011, Australia Full list of author information is available at the end of the article © The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Annabell et al. Journal of Orthopaedic Surgery and Research (2018) 13:127 Page 2 of 5 becoming rounded or blunted, and increasing in signal Comparison of findings intensity with age. Although there is anatomic variation, The MRI reports and arthroscopic findings were com- the majority of changes seen in labral morphology are pared for the investigation of labral tears, ligamentum due to the dynamic and translational stresses placed on teres damage, and chondral rim damage. For the arthro- the hip labrum. scopic findings, labral tears were graded in direction and Minimal data is available for the diagnosis of liga- magnitude. Ligamentum teres tears were graded using mentum teres tears and chondral rim damage. It is also the Gray and Villar classification (Table 1). Chon- noted that it can be difficult to quantify the degree of dral rim damage was graded using a modified Outer- damage with conventional imaging . Furthermore, the bridge classification (Table 2). Both the acetabular and experience of the radiologist reporting the images can femoral articular surfaces were assessed. The articular affect the accuracy of diagnosis . It has been shown that cartilage was graded on the MRI and at arthroscopy the musculoskeletal-trained radiologists have better diagnostic classification system of Outerbridge. Grade 0 indicated accuracy than those without subspecialty training . intact articular cartilage; grade 1, chondral softening Arthroscopy has become a valuable diagnostic tool for (high signal); grade 2, superficial ulceration, fissuring, or hip joint pathology, as well as having a therapeutic cap- fibrillation involving less than 50% of the depth of the acity . As with any surgery, it does have recognised articular surface; grade 3, ulceration, fissuring, or fibrilla- complications. In patients where imaging has failed to tion involving more than 50% of the depth of the articu- provide a clear diagnosis however, direct visualisation of lar cartilage; and grade 4, full-thickness chondral wear the joint by arthroscopy provides both diagnostic and with exposure of subchondral bone. All chondral lesions therapeutic capacity. on MRI were confirmed in at least two separate planes Non-contrast MRI imaging is currently part of the pre and specific attention to the weight-bearing acetabulum, diagnostic work up of hip pain at Western Health, fovea, and posterior joint space. Figure 1 shows examples Victoria. This study was designed to analyse the sensitiv- of some of the pathology noted on arthroscopy while Fig. 2 ity and specificity of MRI in identifying intra-articular shows pathology reported by the radiologists. hip pathology, specifically, tears of the ligamentum teres The radiologists were asked to report whether damage and chondral rim damage, in comparison to hip arthros- was present, and also to what grade, for each of the copy at a single institution. three pathologies. Each radiologist’s reports were also compared to investigate the inter-observer reliability of Methods the findings. A retrospective review of a consecutive series of hip arth- roscopies performed between March 2011 and January Statistics 2013 was conducted. A total of 71 cases (41 male, 30 The accuracy of the MRI reports were judged by the female) with MRI in 68 patients were thus available for arthroscopic findings and were calculated by true posi- prospective review by musculoskeletal radiologists. tives, true negatives, false positives, and false negatives. From these results, positive predictive values, negative MRI predictive values, overall sensitivity, specificity, and ac- The 71 cases were obtained from four different radi- curacy were calculated. ology providers. All had been previously reported by Statistical analysis was performed with SPSS software. board-certified radiologists. These images were re-reported Paired student T tests were conducted to determine the by two musculoskeletal-trained radiologists blinded to the accuracy of each observer. All p values were given a stat- original report and the findings at hip arthroscopy. istical significance value of 0.05. Inter-observer reliability The MRI sequences reviewed included coronal T1, scores were calculated with kappa values. Scores be- coronal PD FS, sagittal PD FS, and Ax Obl PD FS se- tween 0 and 0.20 were graded as slight, 0.21 and 0.40 as quences. All scans were performed on a GE 3 Tesla twin poor, 0.41 and 0.60 as fair, 0.61 and 0.80 as moderate, speed HDx (Peak gradient 790 gauss/cm). All studies and 0.81 and 1 as substantial. were judged to be of diagnostic quality. Table 1 Grading system for ligamentum teres tears Hip arthroscopy All hip arthroscopies were performed by a single sur- Grade of tear Modified Gray and Villar classification geon between March 2011 and January 2013. All pa- 0 No tear tients were intraoperatively reviewed for labral tears, 1 Low grade tear < 50% ligamentum teres tears, and chondral rim damage. All 2 High grade tear > 50% operative reports were available and collected for review 3 Complete tear for the purposes of this study. Annabell et al. Journal of Orthopaedic Surgery and Research (2018) 13:127 Page 3 of 5 Table 2 Grading system for chondral rim damage Grade of chondrosis Original Outerbridge classification Modified Outerbridge classification for acetabular chondrosis 1 Softening and swelling of cartilage Softening of cartilage 2 Fragmentation and fissuring in an area 1.5 cm or Cleavage tear less in diameter 3 Fragmentation and fissuring to the level of subchondral Delamination bone in an area with a diameter more than 1.5 cm 4 Exposed subchondral bone Erosion of cartilage down to exposed bone Results positive cases correctly. For the 13 patients with no chon- There were 71 patients, with an age range of 21 to 66, dral disease at arthroscopy, observer A incorrectly re- and an average age of 39. There were 30 women (42%) ported 6 cases and correctly reported 7 while observer B and 41 men (58%). There were 35 right hips and 38 left incorrectly reported 4 cases and correctly reported 9 cases. hips examined. The average time between MRI and hip arthroscopy was 71 days (range 1 to 179 days). Inter-observer variation Of the cases positive for pathology, inter-observer vari- Ligamentum teres tears ation for ligamentum teres tears, the kappa value was At arthroscopy, 63 patients had a grade 1, 2, or 3 tear of 0.470 (fair); for labral tears, the kappa value was 0.501 their ligamentum teres. Observer A correctly identified (fair); and for chondral damage, the kappa value was 55 out of 63 tears. From the 8 cases that were normal at 0.510 (fair). arthroscopy, observer A correctly reported 2 while he described 6 as torn. Observer B correctly identified 59 out of 63 tears, and from the 8 normal ligamentum teres Discussion cases, he described 2 as torn and 6 correctly. Table 3 Hip arthroscopy and direct visualisation of the hip joint outlines the results of the individual observers compar- is the gold standard for the diagnosis of internal de- ing MRI results with arthroscopic findings. Table 4 out- rangement of the hip joint, with X-ray, ultrasound, com- lines the average accuracy between observers A and B. puted tomography (CT), and bone scan providing very The accuracy between observers A and B was taken as little information regarding the internal structures of the the mean of the individual observer results. hip joint. MRA with fluoroscopically guided intra-articular con- Labral tears trast (Gadolinium) injection has shown the best correla- For the patients who had labral tears identified at arth- tive results after hip joint arthroscopy, for labral tears roscopy, observer A correctly identified 54 out of 56 with 92% sensitivity and 100% specificity . Chondral cases while observer B correctly identified 47 cases. Of rim derangement detection is, however, poor, demon- the 15 cases without tears, observer A reported 10 cor- strating 79% sensitivity and 77% specificity. Concomitant rectly and 5 incorrectly. Observer B reported 11 cor- ligamentum teres tear and synovitis detection is limited, rectly and 4 incorrectly. demonstrating 1.8% sensitivity and 98.5% specificity . Furthermore, all invasive techniques, including MRA Chondral damage with intra-articular contrast injection, are associated The comparison of MRI grading with arthroscopy within 1 with a risk of infection and pain. MRI without grade was correct in 54 out of 58 cases with chondral intra-articular contrast injection is the non-invasive im- damage for observer A, while observer B identified 51 aging of choice for the hip, demonstrating lower risk of Fig. 1 Arthroscopic findings. a Labral tear. b Ligamentum teres tear and chondral damage. c Inflamed ligamentum teres Annabell et al. Journal of Orthopaedic Surgery and Research (2018) 13:127 Page 4 of 5 Fig. 2 MRI findings. a Chondral rim damage. b Ligamentum teres tear. c Labral tear infection and pain, being readily available and being of subject to continuous weight-bearing stresses, undergo- lower cost. ing morphologic change, and degeneration with age . In the current literature, non-contrast MRI is moder- Abnormal hip stress results in labral injury, which usu- ately accurate for identifying labral tears (85% sensitivity) ally manifests as a tear, sometimes with displacement or and chondral rim damage (92% sensitivity) . MRI is detachment of a labral flap . poor at quantifying chondral damage . The MRI criteria used for a labral tear was a line of 3 Tesla MRI has also been confirmed as superior to 1.5 high signal coursing from the articular side through the Tesla for quantifying internal derangement of the hip . base or into the substance of the labrum, with or with- Our results demonstrated reasonable sensitivity out distraction of the labrum . Chondrolabral junc- (90.92%) and positive predictive values (91.96%). The tion signal abnormality was regarded as a labral tear, intra-observer reliability was only fair, and this may be although this may be difficult to distinguish from an ar- attributed to a learning effect of each observer as the ticular cartilage abnormality at the base of the labrum. study progressed. We found MRI to be poorly specific Importantly, chondral damage grading is poorly accur- and inaccurate for measuring or grading chondral le- ate with the planar sequences used, the cartilage only sions. MRI was shown to have a poor negative predictive well seen (directly perpendicular) on two to three slices value. The investigators did note that there was an aver- on the coronal PDFS sequences; therefore, the whole age time difference of 71 days between patients undergo- cartilage surface was not seen in its entirety on conven- ing the MRI and arthroscopy. This difference in time may tional imaging. have resulted in deterioration of the lesions between hav- The limitations of this study included possible sampling ing the MRI and undergoing the arthroscopy; leading to bias, with the high prevalence of disease in the patient co- larger- more detectable- lesions at the time of arthroscopy. hort, which clearly reflects the presentation of hip symp- Assessment for ligamentum teres damage was based toms. Patients without hip pain were not included. on alteration in the normal smooth contour and loss of the normal low signal. Focal high signal with loss of the Conclusion normal smooth contour was indicative of a partial liga- This study demonstrates that tears and synovitis of the mentum teres tear, while complete loss of continuity in- ligamentum teres, as potential sources of hip pain, can be dicated complete tear. High signal change within and accurately identified on conventional non-arthrographic surrounding the ligamentum was considered indicative MRI. MRI is able to detect the presence of labral tears, of synovitis. Changes in signal intensity reflect degener- chondral defects, and ligamentum teres tears/synovitis; ation and injury, simulating the changes seen in the however, MRI was found to be poor at grading the path- meniscal fibrocartilage of the knee. The labrum is ology compared to direct visualisation during arthroscopy. Table 3 MRI results compared with arthroscopy—individual observers Accuracy Sensitivity (%) Specificity (%) PPV (%) NPV (%) Observer A B A B A B A B A B Lig Teres 80.28 91.55 88.71 93.65 22.22 75.00 88.71 96.72 22.22 60.00 95% CI –– 78.11–95.34 84.53–98.24 2.81–60.01 34.91–96.81 78.11–95.34 88.55–99.61 2.81–60.01 26.24–87.84 Labrum 90.14 81.69 96.43 83.93 66.67 73.33 91.53 92.16 83.33 55.00 95% CI –– 87.69–99.56 71.67–92.38 38.38–88.18 44.9–92.21 81.32–97.19 81.12–97.82 51.59–97.91 31.53–76.94 Chondral rim 85.92 85.92 93.22 89.47 50.00 71.43 90.16 92.73 60.00 62.50 95% CI –– 83.54–98.12 78.48–96.04 21.09–78.91 41.9–91.61 79.70–96.34 82.41–97.98 26.24–87.84 34.52–85.41 Abbreviations: PPV positive predictive value, NPV negative predictive value Annabell et al. Journal of Orthopaedic Surgery and Research (2018) 13:127 Page 5 of 5 Table 4 MRI results compared with arthroscopy—combined results Accuracy Sensitivity (%) Specificity (%) PPV (%) NPV (%) Lig Teres 85.92 91.20 47.06 92.68 42.11 95% CI – 84.80–95.52 22.98–72.19 86.56–96.6 19.72–67.17 Labrum 85.92 90.18 70.00 91.82 65.63 95% CI – 83.11–94.99 50.60–85.27 85.00–96.21 46.81–81.43 Chondral rim 85.92 91.38 61.54 91.38 61.54 95% CI – 84.72–95.79 40.57–79.77 84.72–95.79 40.13–80.10 Abbreviations: PPV positive predictive value, NPV negative predictive value MRI has poor specificity and negative predictive value, teres tears: a retrospective analysis of 187 patients with hip pain. Am J Roentgenol. 2014;203(2):418–23. and thus, a negative MRI result may warrant further in- 3. Schmid MR, Nötzli HP, Zanetti M, Wyss TF, Hodler J. Cartilage lesions in the vestigation. Conventional non-arthrographic MRI offers hip: diagnostic effectiveness of MR arthrography. 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Abbreviations MRI of the knee: how do field strength and radiologist’s experience CI: Confidence interval; CT: Computed tomography; MRA: Magnetic influence diagnostic accuracy and interobserver correlation in assessing resonance arthrography; MRI: Magnetic resonance imaging; NPV: Negative chondral and meniscal lesions and the integrity of the anterior cruciate predictive value; PPV: Positive predictive value ligament? Eur Radiol. 2009;19(6):1519–28. 8. Theodoropoulos JS, Andreisek G, Harvey EJ, Wolin P. Magnetic resonance Availability of data and materials imaging and magnetic resonance arthrography of the shoulder: Summary of the data generated or analysed during this study has been included dependence on the level of training of the performing radiologist for in this published article. The datasets used and/or analysed during the current diagnostic accuracy. Skelet Radiol. 2010;39(7):661–7. study are available from the corresponding author on reasonable request. 9. Baber YF, Robinson AHN, Villar RN. Is diagnostic arthroscopy of the hip worthwhile? A prospective review of 328 adults investigated for hip pain. Authors’ contributions J Bone Joint Surg Br. 1999;81-B(4):600–3. LA is the principle author for this project; he was involved in the study 10. Gray AJ, Villar RN. The ligamentum teres of the hip: an arthroscopic classification design, data collection and analysis, draft, and final approval of the article. of its pathology. Arthroscopy. 1997;13(5):575–8. VM and AR are the secondary authors and were involved in the data 11. Toomayan GA, Holman WR, Major NM, Kozlowicz SM, Vail TP. Sensitivity of acquisition. BM was involved in the data collection and analysis. CC was MR arthrography in the evaluation of acetabular labral tears. Am J Roentgenol. involved in the article revision and submission and is the corresponding 2006;186(2):449–53. author for the project. PT is the project supervisor and was also involved in 12. Potter HG, Schachar J. High resolution noncontrast MRI of the hip. J Magn the data acquisition. All authors read and approved the final manuscript. Reson Imaging. 2010;31(2):268–78. 13. Zlatkin MB, Pevsner D, Sanders TG, Hancock CR, Ceballos CE, Herrera MF. Ethics approval and consent to participate Acetabular labral tears and cartilage lesions of the hip: indirect MR Ethics approval was obtained from the Western Health Low Risk Ethics Panel, arthrographic correlation with arthroscopy—a preliminary study. Am J project number QA2013.34. Roentgenol. 2010;194(3):709–14. 14. James SLJ, Ali K, Malara F, Young D, O'Donnell J, Connell DA. MRI findings Competing interests of femoroacetabular impingement. Am J Roentgenol. 2006;187(6):1412–9. The authors declare that they have no competing interests. 15. Sundberg TP, Toomayan GA, Major NM. Evaluation of the acetabular labrum at 3.0-T MR imaging compared with 1.5-T MR arthrography: preliminary experience. Radiology. 2006;238(2):706–11. Publisher’sNote 16. Lecouvet FE, Vande Berg BC, Malghem J, Lebon CJ, Moysan P, Jamart J, Springer Nature remains neutral with regard to jurisdictional claims in Maldague BE. MR imaging of the acetabular labrum: variations in 200 published maps and institutional affiliations. asymptomatic hips. Am J Roentgenol. 1996;167(4):1025–8. 17. Ipavec M, Iglic A, Iglic V, Srakar F. Stress distribution on the hip joint articular Author details surface during gait. Pflugers Arch. 1996;431:R275–6. Department of Orthopaedics, Western Health, 160 Gordon Street, Footscray, 18. Schmitz MR, Campbell SE, Fajardo RS, Kadrmas WR. Identification of Melbourne, VIC 3011, Australia. Department of Radiology, Western Health, acetabular labral pathological changes in asymptomatic volunteers using 160 Gordon Street, Footscray, Melbourne, VIC 3011, Australia. optimized, noncontrast 1.5-T magnetic resonance imaging. Am J Sports Med. 2012;40(6):1337–41. Received: 1 February 2018 Accepted: 10 May 2018 References 1. Byrd JWT, Jones KS. Diagnostic accuracy of clinical assessment, magnetic resonance imaging, magnetic resonance arthrography, and intra-articular injection in hip arthroscopy patients. Am J Sports Med. 2004;32(7):1668–74. 2. Datir A, Xing M, Kang J, Harkey P, Kakarala A, Carpenter WA, Terk MR. Diagnostic utility of MRI and MR arthrography for detection of ligamentum
Journal of Orthopaedic Surgery and Research – Springer Journals
Published: May 29, 2018
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