Usefulness of MR arthrography of the hip with leg traction in the evaluation of ligamentum teres injuries Luis Cerezal, Luis Pérez Carro, Javier Llorca, Moisés Fernández-Hernando, Eva Llopis, Juan Antonio Montero & Ana Canga Skeletal Radiology Journal of the International Skeletal Society A Journal of Radiology, Pathology and Orthopedics ISSN 0364-2348 Skeletal Radiol DOI 10.1007/s00256-015-2210-9
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Author's personal copy Skeletal Radiol DOI 10.1007/s00256-015-2210-9
SCIENTIFIC ARTICLE
Usefulness of MR arthrography of the hip with leg traction in the evaluation of ligamentum teres injuries Luis Cerezal 1 & Luis Pérez Carro 2 & Javier Llorca 3,4 & Moisés Fernández-Hernando 1 & Eva Llopis 6 & Juan Antonio Montero 5 & Ana Canga 5,7
Received: 1 April 2015 / Revised: 19 June 2015 / Accepted: 24 June 2015 # ISS 2015
Abstract Purpose To retrospectively evaluate the diagnostic accuracy of magnetic resonance (MR) arthrography of the hip with leg traction in the evaluation of ligamentum teres lesions and to evaluate whether there is increased articular distraction, possibly indicating secondary instability, in hips with ligamentum teres injuries. Materials and methods Institutional review board approval and informed consent were obtained for this retrospective study. MR arthrograms of the hip with leg traction of 184 consecutive patients, including 108 men (mean age, 32.6 years; range, 19–53 years) and 76 women (mean age, 38.5 years; range, 18–56 years), who underwent hip arthroscopy were assessed for the presence of ligamentum teres lesions. The MR arthrographic findings were independently assessed by two radiologists who were blinded to the arthroscopic results. The inclusion criteria stipulated no previous surgery, arthroscopy within 1 month after MR arthrography, The authors did not receive any funding support. * Luis Cerezal
[email protected] 1
Department of Radiology, Diagnóstico Médico Cantabria, Calle Castilla 6 Bajo, 39002 Santander, Cantabria, Spain
2
Learnig Trauma Med. Centro de Consultas Médicas CCM, Orthopedic Surgery department, Santander, Spain
3
University of Cantabria - IDIVAL, Santander, Spain
4
CIBER Epidemiology and Public Health, Santander, Spain
5
Anatomy and Cell Biology, Cantabria University, Santander, Spain
6
Department of Radiology, Alzira Hospital, Valencia, Spain
7
Department of Radiology Marqués de Valdecilla University Hospital, Santander, Cantabria, Spain
and availability of a detailed surgical report with ligamentum teres findings. The arthroscopy findings served as the reference standard. Sensitivity, specificity, accuracy, and K statistics for interobserver and intraobserver agreement were calculated. Results At arthroscopy, 32 ligamentum teres injuries were found. The ligamentum teres was normal in 152 (82.6 %) patients and had suffered low-grade partial tears in 15 (8.1 %) patients, high-grade partial tears in 10 (5.4 %) patients, and complete ruptures in 7 (3.8 %) patients. MR arthrography with axial traction demonstrated moderate sensitivity and high specificity for both low-grade (62/ 93 %) and high-grade (66/96 %) partial tears. Grouping lowand high-grade partial tears increased the diagnostic performance of MR arthrography, yielding a sensitivity of 87 % and a specificity of 95 %. For complete ligamentum teres tears, MR arthrography with leg traction demonstrated high sensitivity (92 %) and specificity (98 %). Articular distraction was significantly increased in patients with complete ruptures of the ligamentum teres (p=0.001). Conclusion MR arthrography with leg traction offers accurate diagnosis of ligamentum teres injuries. Patients with complete tears of the ligamentum teres exhibit increased articular distraction that may indicate secondary hip instability.
Keywords Ligamentum teres . Hip injuries . MR arthrography . Hip arthroscopy . Hip pain . Instability . Ligamentum teres pathology
Abbreviations LT ligamentum teres FAI femoroacetabular impingement
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Introduction The ligamentum teres (LT) of the hip has traditionally been regarded as an embryonic remnant with no significant function in adult life, and previously, it was often sacrificed in open hip surgery [1, 2]. However, the detection of LT tears has become an issue of greater concern in imaging diagnosis and hip arthroscopy because of the role of the LT as a generator of hip pain, and its potential involvement in hip microinstability has been further elucidated [3–6]. Recent studies confirm that the LT is an important stabilizer structure and, in many ways, is similar to the anterior cruciate ligament of the knee [2, 7]. The treatment of these injuries has also evolved in recent years with advancements in arthroscopy. Partial and complete tears are typically treated with arthroscopic debridement [2, 8, 9]; however, in select patients with high athletic demands who suffer residual instability after arthroscopic debridement, LT reconstruction can be performed [6, 10, 11]. There are few articles devoted to the utility of magnetic resonance (MR) imaging and MR arthrography in the evaluation of LT injuries. In arthroscopic series, the utility of MR imaging is questioned, as sensitivities have been reported to be as low as 1.8 % [8]. The MR diagnosis of partial LT tears appears to be especially challenging. Recent articles examining LT injuries in 3-T MR imaging and MR arthrography indicate that these modalities demonstrate better diagnostic performance for the assessment of LT injuries [12–15]. MR arthrography with axial traction allows for the separation of the articular surfaces and may provide a better assessment of the central compartment, including the LT [16–18]. Recently, an MR arthrography study with axial traction and arthroscopic correlation demonstrated the utility of this technique in the diagnosis of labral and chondral injuries [18]. To the best of our knowledge, this is the first study to analyze the utility of MR arthrography with axial traction for the diagnosis of LT injuries with arthroscopic correlation using a modified descriptive classification of LT injuries. The purpose of this study was to retrospectively assess the performance of MR arthrography of the hip with leg traction in the evaluation of LT lesions with arthroscopic correlation and to evaluate whether there is increased articular distraction, possibly indicating secondary instability, in hips with ligamentum teres injuries.
Material and methods Study population The study was approved by our institutional review board, and informed consent was obtained from all patients. This was a retrospective study of 184 consecutive patients, including 108 men (mean age, 32.6 years; range, 19–53 years) and 76
women (mean age, 38.5 years; range, 18–56 years), with various hip problems who were arthroscopically treated (“reference standard^) between January 1, 2009, and January 1, 2013, and evaluated preoperatively using MR arthrography in combination with a lower-extremity axial traction system. The inclusion criteria were as follows: (1) MR arthrography performed at our institution using a standardized protocol and (2) subsequent arthroscopy performed within 1 month after the preoperative imaging, with the availability of a detailed report concerning the LT. The exclusion criteria were severe degenerative hip joint disease (Tönnis 3) and any history of previous surgery. Arthroscopy Diagnosis at arthroscopy, which served as the reference standard, was performed within 1 month after preoperative imaging by a single fellowship-trained orthopedic surgeon (L.P.C.) with 12 years of experience in hip arthroscopy. The surgeon was aware of the results of the MR examination. LT tears were classified according to the tear percentage of the ligament (Botser classification) as follows [8]: grade 0, no tear (including degenerative changes in the LT without tearing); grade 1, low-grade partial LT tear 50 %; and grade 3, full-thickness LT tear (Fig. 1). The presence of degenerative changes of the LT, manifested by ligamentous thickening, superficial fraying or focal synovitis was also recorded. MR arthrography MR imaging studies were performed in our outpatient imaging center, which only has CT and MR scanners on site. For this reason, CT was used for guidance of the articular puncture. Intraarticular contrast medium was injected in a standardized fashion. A total volume of 12–15 ml of a mixture that contained 4 ml of ionic contrast material (Omnipaque 240 [iohexol, 240 mg of iodine per ml]; GE Healthcare, Cork, Ireland), 4 ml of lidocaine, 12 ml of saline solution, and 0.1 ml of gadodiamide (Omniscan; GE Healthcare; final concentration of 2.0 mmol/L) was injected into the femoroacetabular joint with CT guidance using an anterior approach. CT scout images or axial CT slices were obtained for confirmation of intraarticular contrast injection. MR imaging was performed within 20 min after contrast agent injection. Leg traction was applied on the MR imaging table using a standard MR-compatible orthopedic skin traction device (Noba-Extensionsverband, Noba) with a load of 8 kg, consisting of two 4-kg sandbags attached to the leg over a deflection pulley. Manual traction was applied by the radiologist before the load was applied. Traction was continuous throughout the MR imaging study.
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Fig. 1 Modified Botser’s classification of ligamentum teres injuries according to the degree of tearing: a grade 0, normal ligament or b intrasubstance degenerative changes without tearing; c grade 1, low-
grade tear (50 % torn); and e grade 3, full-thickness tear (100 % torn)
MR arthrography was performed using a 1.5-T (Excelart Vantage AGV; Toshiba Medical Systems, Tokyo, Japan) MR imaging system with an 8-channel QD Torso Speeder coil. The standard protocol comprised fat-suppressed T1-weighted images obtained in the coronal plane (parallel to the long axis of the femoral neck), sagittal plane, and oblique transverse plane (parallel to the long axis of the femoral neck) as well as T1-weighted and proton-density-weighted images with fat suppression in the oblique coronal plane. The parameters used for all sequences are presented in Table 1.
All MR arthrograms were retrospectively and independently reviewed by two musculoskeletal radiologists (L.C. and A.C., with 12 and 5 years of experience, respectively, in hip MR arthrography). The readings were performed randomly over a period of 2 weeks. To assess intraobserver variability, all MR images were reevaluated by the observer who had more experience with MR arthrography 1 month after the first assessment. Tears in the LT were classified following the same classification that was used in arthroscopy. The criterion for a full-
Table 1
Sequence parameters for MR arthrography
Imaging parameter
Coronal T1Coronal fat Coronal fat Axial oblique fat Sagittal oblique fat Axial T1-weighted weighted spin-echo suppressed PD FSE suppressed T1- suppressed T1suppressed T1spin-echo weighted FSE weighted FSE weighted FSE
Repetition time (ms)/echo time (msec) Matrix size Field of view (cm) Section thickness (mm) Intersection gap No. of signals acquired Resolution (mm) Scan time
495/12
2500/42
522/12
2500/42
500/13
495/12
368×368 16 cm 3 mm 0.6 mm 1.5 0.43 4 min 30 s
368×368 18 cm 4 mm 0.6 mm 1.5 0.46 5 min
368×368 16 cm 3 mm 0.6 mm 1.5 0.43 4 min 30 s
368×368 16 cm 3 mm 0.6 mm 1.5 0.43 4 min 30 s
368×368 16 cm 3 mm 0.6 mm 1.5 0.43 4 min 30 s
368×368 16 cm 4 mm 0.6 mm 1.5 0.43 4 min 30 s
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thickness tear was the spread of the contrast medium throughout the entire thickness of the ligament. The criteria for a lowgrade partial-thickness tear were the disruption of the smooth surface of the ligament and accumulation of the contrast medium within less than 50 % of the ligament. The criteria for a high-grade partial-thickness tear were the disruption of the smooth surface of the ligament and accumulation of the contrast medium within more than 50 % of the ligament. Intrasubstance degenerative changes was defined by inhomogeneous signal in T1 sequences, high signal intensity in proton-density-weighted fat-suppressed images, together with ligament thickening and irregular contours without any focal defects of the LT. The maximum distance between the femoral and acetabular cartilage surfaces was measured on the central image at the most proximal point of the femoral head on coronal and sagittal images, using the measuring tool provided by the Osirix software (Osirix MD, FDA cleared / CE II labeled; 64-bit, http:/www.osirix-viewer.com/; Fig. 2). The mean joint space distraction was calculated and the correlation of joint distraction between patients with normal LTs and those with injuries to the ligament was compared.
Agreement regarding the presence of degenerative changes was reached by consensus to evaluate whether there was a relationship between degenerative changes and diagnostic errors (false positives, namely, degenerative changes misdiagnosed as partial tears, or false negatives, namely, partial tears misinterpreted as degenerative changes without rupture). Pearson’s chi-square test of association was used to discover if there is a relationship between these two categorical variables. The entire cohort was tested for possible differences in the age distributions using Bartlett’s test for differences between variances, and Fisher’s exact test was used to address the sex distribution among the groups. Associations between the articular joint distraction measurements in the coronal and sagittal planes and the arthroscopic grades of LT injury were evaluated using analysis of variance and Bartlett’s test for equal variances, and multiple comparisons between LT injury groups were performed using the Sidak method. Interobserver and intraobserver agreement were calculated for the coronal and sagittal distraction measurements using intraclass correlation coefficients. Statistical significance was defined as a p-value of
