- Email: [email protected]
Visualization of Concurrent Anterolateral and Anterior Cruciate Ligament Injury on Magnetic Resonance Imaging
Visualization of Concurrent Anterolateral and Anterior Cruciate Ligament Injury on Magnetic Resonance Imaging Bradley L. Young, M.D., John A. Ruder, M.D., David P. Trofa, M.D., and James E. Fleischli, M.D.
Purpose: To investigate the ability to visualize the anterolateral ligament (ALL) on magnetic resonance imaging (MRI) and identify ALL injuries in an intact- anterior cruciate ligament (ACL) and torn-ACL cohort. We also aimed to assess inter-rater reliability between 2 radiologists when it comes to the aforementioned assessment. Methods: MRIs that met inclusion and exclusion criteria were placed into a control (ACL-intact) or study (ACL-injured) cohort. MRIs were independently analyzed by 2 radiologists for data points pertaining to demographics, ALL visualization, presence of ALL injury, and concomitant knee abnormalities. Inter-rater reliabilities for visualizing the ALL and identifying ALL injuries were assessed. Results: The control and study groups consisted of 116 and 82 MRIs, respectively. Age varied between the 2 groups, but sex distribution was similar. With near-perfect agreement (kappa ¼ 0.92), both radiologists visualized at least part of the ALL in more than 95% of MRIs irrespective of ACL integrity. The mean incidence of ALL injury in the ACL injured group was 53.05% with minimal inter-rater agreement (kappa ¼ 0.38). Segond fractures were noted in a mean 13.95% of MRIs with concomitant ALL and ACL injuries. Conclusions: The ALL was reliably visualized on MRI irrespective of whether the ACL was intact or torn. However, ALL injuries were not reliably diagnosed on MRI in the setting of an ACL tear. Poor interobserver reliability shows the potential for false-positive and -negative interpretation. These findings suggest that, in this study, ALL injuries could not be accurately diagnosed in the presence of an ACL tear using MRI. On the basis of these findings, it is recommended that physicians should not rely on MRI to diagnose an ALL injury in the presence of an ACL injury. Level of Evidence: Level III, retrospective comparative trial
he anterolateral ligament (ALL) of the knee was first described more than a century ago as the “pearly band” associated with Segond fractures.1 It runs superficial to the lateral collateral ligament, originating on the lateral femoral epicondyle and inserting on the anterolateral tibia and lateral meniscus.2-4 Its exact role in knee kinematics and clinical relevance remains undetermined. Studies have shown varying results when it comes to the ability to identify the ALL as an independent structure on advanced imaging.5-8 The ALL was first
T
From the Department of Orthopaedic Surgery, Atrium Health Musculoskeletal Institute, OrthoCarolina Research Institute, and OrthoCarolina Sports Medicine Center, Charlotte, North Carolina, U.S.A. The authors report that they have no conflicts of interest in the authorship and publication of this article. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Received March 6, 2019; accepted September 25, 2019. Address correspondence to James E. Fleischli, M.D., Department of Orthopaedic Surgery, Atrium Health Musculoskeletal Institute, 1025 Morehead Medical Dr., Suite 300, Charlotte, NC 28204. E-mail: james.fleischli@ orthocarolina.com Ó 2019 by the Arthroscopy Association of North America 0749-8063/19258/$36.00 https://doi.org/10.1016/j.arthro.2019.09.039
described in a magnetic resonance imaging (MRI) study by Caterine et al.,9 in which they identified the ALL in 100% of their cadaveric specimens. High detection rates have been described in additional MRI studies.6,10,11 In contrast, there also have been studies that have found MRI to be unreliable for detecting the ALL.8,12 The inability to consistently identify concurrent ALL injury in the setting of anterior cruciate ligament (ACL) tear presents a significant challenge to determining the ligament’s clinical relevance. The purpose of this study was to investigate the ability to visualize the ALL on MRI and identify ALL injuries in an ACL-intact and ACL-injured (complete ACL tear) cohort. We also aimed to assess inter-rater reliability between 2 radiologists when it comes to the aforementioned assessment. Our null hypothesis was that inter-rater reliability for identifying ALL injuries on MRI would not differ between an ACL-intact or ACL-injured cohort.
Methods The institutional review board determined this study met the criteria for approval (File #02-16-34E).
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol
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Electronic medical records were queried to identify patients with a lower-extremity MRI (Current Procedural Terminology code 73721). These patients were then placed into the control (ACL intact; diagnoses: chondromalacia or meniscal tear) or study (ACL injured; diagnoses: complete ACL tear) group. Patients with multiligamentous knee injury, chronic ACL injury (greater than 6 months), and previous ligament injury/ surgery were excluded. Two fellowship-trained musculoskeletal radiologists evaluated each MRI for the presence of the ALL and ALL injury. Each MRI was evaluated one time (no time constraint) by each radiologist, separately. The radiologists had 21 years and 18 years of practice experience. The MRI specifics and procedure have been previously published by several of our authors.7 All MRIs were performed on 1.5-Tesla machines without contrast at 1 of 2 scanner sites with the patient supine and knee extended. Scanner sequences can be found in Table 1. The protocol for identifying the ALL on MRI previously defined by Helito et al.6 was used and reviewed by the musculoskeletal radiologist within a week before conducting this study; however, our study did not stratify ALL identification into femoral, meniscal, and tibial portions. The protocol involves localizing the femoral attachment of the ALL via its close proximity to the insertion of the fibular collateral ligament (Fig 1).7 The ALL was deemed visual if at least one-third (proximal, middle, distal) of the ligament was seen on MRI. ALL injury was defined as increased signal, overt tear, or avulsion fracture at the femoral or tibial attachment sites, if visible. The radiologists also noted any other knee pathology (i.e., effusion, lateral capsular injury, Segond fracture, and presence of bone bruising). Inter-rater reliability was assessed between raters 1 and 2 concerning their ability to visualize the ALL and identify an ALL injury. Statistical Analysis Standard descriptive statistics, including measures of central tendency, variance, as well as frequencies and proportions, were calculated for all data points. For bivariate analyses, the Fisher exact test was used for categorical data to determine statistical differences. Continuous data were evaluated for statistical
differences between groups using a Wilcoxon rank sum test. Inter-rater agreement was assessed between all radiologists for each data point of interest. Interobserver reliability was assessed using Cohen’s Kappa coefficient.13 All analyses were performed using SAS 9.4 (SAS Institute, Cary, NC).
Results Of the 273 MRIs reviewed for this study, 75 MRIs (27.5%) were excluded. The most common reason for exclusion was because the radiologist did not use the standardized ALL protocol referenced previously. After exclusion, there were 198 (72.5%) cases available for analysis, including 82 (41.4%) study patients and 116 (58.6%) control patients (Fig 2). Patient age differed between groups (P < .0001), but sex distribution was similar (P ¼ .0609) (Table 2). Concerning all MRIs, raters 1 and 2 were able to visualize the ALL in 195 of 198 (98.5%) and 193 of 198 (97.5%), respectively. In the ACL-intact cohort, the ALL was visualized in 114 of 116 (98.3%) and 111 of 116 (95.7%) of MRIs by raters 1 and 2, respectively. In the ACL-injured group, the ALL visualization rates were 98.8% and 100% by raters 1 and 2, respectively. Inter-rater reliability for ALL visualization in the entire sample and after cohort stratification was near perfect (kappa > 0.88) (Table 3). Pertaining to ALL injuries on MRI, visualization rates were stratified by observer and group (Table 4). For the entire sample, raters 1 and 2 visualized an ALL injury in 42 of 198 (21.2%) and 50 of 198 (25.3%) MRIs, respectively. In the ACL intact group, only 3 (2.6%) and 2 (1.7%) ALL injuries were seen by raters 1 and 2, respectively. In the ACL-injured group, ALL injuries were seen in 39 of 82 (47.6%) and 48 of 82 (58.5%) MRIs by raters 1 and 2, respectively. Inter-rater reliability for the ability to visualize an ALL injury was near perfect (kappa ¼ 0.95; confidence interval 0.88-1.0) for the ACL-intact group and minimal (kappa ¼ 0.38; confidence interval 0.17-0.58) for the ACL-injured group (Table 4). Raters 1 and 2 identified 42 and 50 ALL injuries among all included MRIs, respectively. Both raters independently recorded the aforementioned results in Table 5. The most common abnormality associated with ALL
Table 1. MRI Specifications Sequence Axial Fat Sat FSE Cor PD fs FSE Sag T1 FSE Sag PC-Fat Sat FSE Sag T2
TE 36 36 M in-Full 30 12
TR 3,384 2,634 517 3,134 28
ETL 8 8 3 8 8
BW 20.8 20.8 35.7 20.8 20.8
Freq 320 288 512 320 320
Phase 224 224 256 224 192
NEX 2 2 2 2 0.75
FOV 14 14 14 14 16
Space 0.5 0.5 0 0 0
Thick 4 4 4 4 2
BW, bandwidth (Hz); Cor, coronal; ETL. echo train length; FOV, field of view (cm); Freq, frequency (MHz); fs, fat suppressed; FSE, fait spion echo; NEX, number of excitations; PD, proton density; Sag, sagittal; Sat, saturation; Space, slice spacing (mm); TE, echo time (ms); Thick, slice thickness (mm); TR, repetition time (ms).
CONCURRENT ALL AND ACL INJURY ON MRI
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Fig 1. Flow diagram depicting sample and cohort size, as well the number of excluded MRIs with respective criteria. (ACL, anterior cruciate ligament; ALL, anterolateral ligament; MRI, magnetic resonance imaging.)
injury on MRI was an effusion (80.0, 100.0%) followed by bone bruising (74.0, 95.2%), lateral capsule injury (38.0, 59.5%), and Segond fracture (11.9, 16.0%).
Discussion This study revealed that, with near perfect inter-rater agreement, at least part of the ALL was visualized in more than 95% of MRIs despite the degree of ACL integrity. It also showed that the mean rate of identifying an ALL injury in the setting of a complete ACL tear on MRI was 53.05% with minimal inter-rater agreement between radiologist. Secondary findings were that effusions and bone bruising were commonly visualized on MRI in the setting of ALL injuries. In addition, a Segond fracture was seen in 11.90% to 16.00% of MRIs also demonstrating ALL injury. This study aimed to assess the utility of MRI to visualize the ALL in the setting of an ACL injury. It was
found that the ALL was at least partially visualized in more than 95% of MRIs in this study despite the degree of ACL integrity. Moreover, there was near-perfect inter-rater agreement when it came to ALL visualization rates between the 2 musculoskeletal radiologists. This finding is in line with a previous study by Helito et al.,6 in which 2 radiologists, who used the same ALL identification protocol as we used, prospectively assessed 42 1.5-Tesla MRI scans without ACL injuries, visualizing at least part of the ALL in 98% of their sample with relatively good interobserver agreement. Of note, we included coronal proton densityeweighted sequences in our protocol, which Helito et al.6 found to be superior to T1 when assessing the ALL. In contrast, a prospective case control study by Devitt et al.8 reported that the ALL was partially visualized in only 64% of 3-Tesla MRIs without ACL injuries and 72% of MRIs with ACL injuries. They go on to discuss
Fig 2. (A) Axial imaging of the right knee with the biceps tendon (green arrow), the fibular collateral ligament (FCL) (red arrow), the anterolateral ligament (ALL) (yellow arrow), and the iliotibial (IT) band (white arrow). Scanning the axial images and finding the FCL insertion, just anterior to this is the approximate femoral insertion of the ALL. Following this caudad, you should be able to track the thickened tissue between the FCL and the IT band. (B) On the coronal image of the right knee, the FCL insertion is located. This is right near the ALL femoral insertion (white arrow). The ALL moves superficial to the popliteus tendon (green arrow); after this, the tendon gives off the meniscal branch (yellow arrow). It is superficial to the inferior lateral geniculate arteries and then inserts approximately 5 to 6 mm distal on the proximal tibia (red arrow). Reproduced with permission from Hartigan et al.7
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Table 2. Demographics of 198 Included MRIs ACL-Injured (n ¼ 82) Age, y Median Range Sex, n (%) Male
Table 4. Ability to Visualize ALL Injuries on MRI
ACL-Intact (n ¼ 116)
Rater 2 P Value <.0001
22.2 11-48
36.2 11-71
49 (59.76%)
53 (45.69%)
.0609
NOTE. Shown are the demographics of the control (ACL-intact) and study (ACL-injured) groups. P values for age and sex were calculated via Wilcoxon and Fisher exact 2-tailed tests, respectively. ACL, anterior cruciate ligament; MRI, magnetic resonance imaging.
that such variation among ALL visualization rates in the literature may be explained by discrepancies in the anatomical description of the ALL.8 In another recent study, the average visualization rate of the ALL on 3-Tesla MRI between 3 radiologists was 68%, with relatively poor agreement between observers.14 From a broader perspective, a recent systematic review of the literature in 2018 found that the MRI visualization rate of the ALL in the setting of ACL injury ranges from 76% to 100%, highlighting even further inconsistencies of ALL detection on MRI.15 This study also aimed to assess the utility of MRI in diagnosing ALL injuries in the setting of concomitant ACL injury. Our data showed that radiologists identified ALL injuries in 21.21% and 25.25% of the MRIs evaluated in this study. Moreover, they identified concomitant ALL injury in a mean 53.05% of MRIs with an injured ACL. For comparison, a wide range of concomitant ALL and ACL injury rates has been reported in a recent systematic review of the literature, 10.8% to 62.5%.15 In our study, we found that there was minimal agreement between musculoskeletal radiologists when it came to their ability to visualize an ALL injury in the setting of an injured ACL. In contrast, agreement improved between radiologists in the setting of an intact ACL. These findings are in line with Table 3. Ability to Visualize the ALL on MRI Rater 2 Rater 1 Entire sample No Yes Control (ACL-intact) group No Yes Study (ACL-injury) group No Yes
Inter-rater Reliability
No
Yes
0 5
3 190
0.92 (0.86-0.97)
0 5
2 109
0.88 (0.79-0.97)
0 0
1 81
0.98 (0.93-1.0)
NOTE. Shown is the inter-rater reliability for determining ALL visualization on MRI. Confidence intervals for inter-rater reliability can be found in parentheses. ALL, anterolateral ligament; MRI, magnetic resonance imaging.
Rater 1 Entire sample No Yes Control (ACL-intact) group No Yes Study (ACL-injury) group No Yes
Inter-rater Reliability
No
Yes
130 10
18 32
0.92 (0.86-0.97)
106 2
1 1
0.95 (0.88-1.0)
24 8
17 31
0.38 (0.17-0.58)
NOTE. Shown is the inter-rater reliability of whether an ALL injury was visualized or not on MRI. Confidence intervals for inter-rater reliability can be found in parentheses. ALL, anterolateral ligament; MRI, magnetic resonance imaging.
findings by Marshall et al.,14 who showed that 3 radiologists had poorer agreement when classifying ALL injury status if the ACL was injured versus not injured. These findings suggest that the visualization of ALL abnormalities on MRI may be suboptimal in the setting of concurrent ACL injury. Possible explanations for this may include distracting injury phenomenon on MRI reading or difficulty with signal differentiation by the observer over the area of the ALL in the setting of large effusion and nearby traumatic injury. A secondary goal of this study was to explore the incidence of and characterize abnormal MRI findings associated with ALL injuries. It is not surprising that an effusion was present in 80% to 100% of MRIs with ALL injuries, as a trauma likely occurred before an MRI of the knee was obtained. On the basis of retrospective review of 193 MRIs of patients who underwent ACL reconstruction, Song et al.16 found that bony contusions of the lateral femoral condyle and lateral tibial plateau (but not the medial femoral condyle or medial tibial plateau) were significantly associated with ALL injury. We found a similar high incidence of bone bruising in patients with an ALL injury. Pertaining to Segond fractures associated with ALL injury visualized on MRI, the incidence is highly variable, ranging from 1.9% to 36.6%.16 We report that a Segond fracture was Table 5. Abnormal Findings Associated With ALL Injuries on MRI ALL injuries, n Associated injuries, n (%) Effusion Lateral capsule injury Segond fracture Bone bruising
Rater 1 42 42 25 5 40
(100.00) (59.52) (11.90) (95.24)
Rater 2 50 40 19 8 37
(80.00) (38.00) (16.00) (74.00)
NOTE. Shown is the proportion of ALL injuries seen on MRI that were accompanied by other MRI abnormalities. ALL, anterolateral ligament; MRI, magnetic resonance imaging.
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CONCURRENT ALL AND ACL INJURY ON MRI
seen in 11.9% and 16.0% of MRIs also demonstrating ALL injury by our radiologists. De Maeseneer et al.17 retrospectively reviewed the MRIs of 13 cases of a Segond fracture and found that the ALL inserted on the Segond bone fragment in 10 of 13 (77%) cases. Similarly, Porrino et al.10 evaluated 20 knee MRIs with a Segond fracture and found that the ALL was attached to the fracture fragment in all but one case limited by anatomic distortion. However, it should be recognized that injury to the ALL is more likely to be in the absence of a Segond fracture. It should again be noted that this study deemed the ALL was visible even if only part of the ligament was seen on MRI. This may explain our high ALL visualization rates and inter-rater agreement on MRI, as well as the lower inter-rater agreement concerning visualization of ALL injuries. Other studies have stratified the ability to visualize the ALL on MRI into 3 regions: femoral, meniscal (middle), and tibial. Marshall et al. also reported on ALL visualization on MRI between 3 radiologists in an ACL-intact and -injured cohort. They found that the ALL could be fully and partially visualized in 11% and 68% of patients, respectively. However, they reported universally poor inter-rater agreement on the radiologists’ ability to visualize the ALL when stratified into regions other than when it came to visualizing the middle segment of the ALL in an ACL-injured cohort.14 Limitations There were several limitations to this study. First, the data compiled by observers in this study were subject to variable inter-rater reliability. Although we were able to demonstrate acceptable agreement between our reviewers for ALL visualization on MRI in general, we did find less-than-ideal agreement between observers concerning their ability to visualize an ALL injury on MRIs with an injured ACL. This poor inter-rater reliability should be taken into account when interpreting our findings concerning knee abnormalities found in association with ALL injury in ACL-deficient knees, as those findings are dependent on the presence of an ALL injury seen on MRI. Another limitation is that we were unable to compare our MRI data with a reference gold standard, direct visualization by dissection.
Conclusions The ALL was reliably visualized on MRI irrespective of whether the ACL was intact or torn. However, ALL injuries were not reliably diagnosed on MRI in the setting of an ACL tear. Poor interobserver reliability shows the potential for false-positive and -negative interpretation. These findings suggest that in this study, ALL injuries could not be accurately diagnosed in the presence of an ACL tear using MRI. On the basis of
these findings, it is recommended that physicians should not rely on MRI to diagnose an ALL injury in the presence of an ACL injury.
Acknowledgments We thank OrthoCarolina Research Institute (OCRI) for data management, statistical analysis, and study oversight and Mecklenburg Radiology Associates for study participation and data collection.
References 1. Segond P. Recherches cliniques et experimentales sur les epanchements sanguins du genou par entorse, Publications du Progres Medical. Paris: Au Bureau du Proges Medical, 1879;1-85. 2. Claes S, Vereecke E, Maes M, Victor J, Verdonk P, Bellemans J. Anatomy of the anterolateral ligament of the knee. J Anat 2013;223:321-328. 3. Macchi V, Porzionato A, Morra A, et al. The anterolateral ligament of the knee: A radiologic and histotopographic study. Surg Radiol Anat 2016;38:341-348. 4. Dodds AL, Halewood C, Gupte CM, Williams A, Amis AA. The anterolateral ligament: Anatomy, length changes and association with the Segond fracture. Bone Joint J 2014;96B:325-331. 5. Claes S, Bartholomeeusen S, Bellemans J. High prevalence of anterolateral ligament abnormalities in magnetic resonance images of anterior cruciate ligament-injured knees. Acta Orthop Belg 2014;80:45-49. 6. Helito CP, Helito PV, Costa HP, et al. MRI evaluation of the anterolateral ligament of the knee: assessment in routine 1.5-T scans. Skeletal Radiol 2014;43:1421-1427. 7. Hartigan DE, Carroll KW, Kosarek FJ, Piasecki DP, Fleischli JF, D’Alessandro DF. Visibility of anterolateral ligament tears in anterior cruciate ligament-deficient knees with standard 1.5-Tesla magnetic resonance imaging. Arthroscopy 2016;32:2061-2065. 8. Devitt BM, O’Sullivan R, Feller JA, et al. MRI is not reliable in diagnosing of concomitant anterolateral ligament and anterior cruciate ligament injuries of the knee. Knee Surg Sports Traumatol Arthrosc 2017;25:1345-1351. 9. Caterine S, Litchfield R, Johnson M, Chronik B, Getgood A. A cadaveric study of the anterolateral ligament: Re-introducing the lateral capsular ligament. Knee Surg Sports Traumatol Arthrosc 2015;23:3186-3195. 10. Porrino J Jr, Maloney E, Richardson M, Mulcahy H, Ha A, Chew FS. The anterolateral ligament of the knee: MRI appearance, association with the Segond fracture, and historical perspective. AJR Am J Roentgenol 2015;204: 367-373. 11. Cavaignac E, Wytrykowski K, Reina N, et al. Ultrasonographic identification of the anterolateral ligament of the knee. Arthroscopy 2016;32:120-126. 12. Taneja AK, Miranda FC, Braga CA, et al. MRI features of the anterolateral ligament of the knee. Skeletal Radiol 2015;44:403-410. 13. Mchugh ML. Interrater reliability: the kappa statistic. Biochem Med (Zagreb) 2012;22:276-282.
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14. Marshall T, Oak SR, Subhas N, Polster J, Winalski C, Spindler KP. Can the anterolateral ligament be reliably identified in anterior cruciate ligament-intact and anterior cruciate ligament-injured knees on 3-T magnetic resonance imaging? Orthop J Sports Med 2018;6: 2325967118796452. 15. Puzzitiello RN, Agarwalla A, Zuke WA, Garcia GH, Forsythe B. Imaging diagnosis of injury to the anterolateral ligament in patients with anterior cruciate ligaments: Association of anterolateral ligament injury with other types of knee pathology and grade of pivot-shift
examination: A systematic review. Arthroscopy 2018;34: 2728-2738. 16. Song GY, Zhang H, Wang QQ, Zhang J, Li Y, Feng H. Bone contusions after acute noncontact anterior cruciate ligament injury are associated with knee joint laxity, concomitant meniscal lesions, and anterolateral ligament abnormality. Arthroscopy 2016;32:2331-2341. 17. De Maeseneer M, Boulet C, Willekens I, et al. Segond fracture: Involvement of the iliotibial band, anterolateral ligament, and anterior arm of the biceps femoris in knee trauma. Skeletal Radiol 2015;44:413-421.
Purpose: To investigate the ability to visualize the anterolateral ligament (ALL) on magnetic resonance imaging (MRI) and identify ALL injuries in an intact- anterior cruciate ligament (ACL) and torn-ACL cohort. We also aimed to assess inter-rater reliability between 2 radiologists when it comes to the aforementioned assessment. Methods: MRIs that met inclusion and exclusion criteria were placed into a control (ACL-intact) or study (ACL-injured) cohort. MRIs were independently analyzed by 2 radiologists for data points pertaining to demographics, ALL visualization, presence of ALL injury, and concomitant knee abnormalities. Inter-rater reliabilities for visualizing the ALL and identifying ALL injuries were assessed. Results: The control and study groups consisted of 116 and 82 MRIs, respectively. Age varied between the 2 groups, but sex distribution was similar. With near-perfect agreement (kappa ¼ 0.92), both radiologists visualized at least part of the ALL in more than 95% of MRIs irrespective of ACL integrity. The mean incidence of ALL injury in the ACL injured group was 53.05% with minimal inter-rater agreement (kappa ¼ 0.38). Segond fractures were noted in a mean 13.95% of MRIs with concomitant ALL and ACL injuries. Conclusions: The ALL was reliably visualized on MRI irrespective of whether the ACL was intact or torn. However, ALL injuries were not reliably diagnosed on MRI in the setting of an ACL tear. Poor interobserver reliability shows the potential for false-positive and -negative interpretation. These findings suggest that, in this study, ALL injuries could not be accurately diagnosed in the presence of an ACL tear using MRI. On the basis of these findings, it is recommended that physicians should not rely on MRI to diagnose an ALL injury in the presence of an ACL injury. Level of Evidence: Level III, retrospective comparative trial
he anterolateral ligament (ALL) of the knee was first described more than a century ago as the “pearly band” associated with Segond fractures.1 It runs superficial to the lateral collateral ligament, originating on the lateral femoral epicondyle and inserting on the anterolateral tibia and lateral meniscus.2-4 Its exact role in knee kinematics and clinical relevance remains undetermined. Studies have shown varying results when it comes to the ability to identify the ALL as an independent structure on advanced imaging.5-8 The ALL was first
T
From the Department of Orthopaedic Surgery, Atrium Health Musculoskeletal Institute, OrthoCarolina Research Institute, and OrthoCarolina Sports Medicine Center, Charlotte, North Carolina, U.S.A. The authors report that they have no conflicts of interest in the authorship and publication of this article. Full ICMJE author disclosure forms are available for this article online, as supplementary material. Received March 6, 2019; accepted September 25, 2019. Address correspondence to James E. Fleischli, M.D., Department of Orthopaedic Surgery, Atrium Health Musculoskeletal Institute, 1025 Morehead Medical Dr., Suite 300, Charlotte, NC 28204. E-mail: james.fleischli@ orthocarolina.com Ó 2019 by the Arthroscopy Association of North America 0749-8063/19258/$36.00 https://doi.org/10.1016/j.arthro.2019.09.039
described in a magnetic resonance imaging (MRI) study by Caterine et al.,9 in which they identified the ALL in 100% of their cadaveric specimens. High detection rates have been described in additional MRI studies.6,10,11 In contrast, there also have been studies that have found MRI to be unreliable for detecting the ALL.8,12 The inability to consistently identify concurrent ALL injury in the setting of anterior cruciate ligament (ACL) tear presents a significant challenge to determining the ligament’s clinical relevance. The purpose of this study was to investigate the ability to visualize the ALL on MRI and identify ALL injuries in an ACL-intact and ACL-injured (complete ACL tear) cohort. We also aimed to assess inter-rater reliability between 2 radiologists when it comes to the aforementioned assessment. Our null hypothesis was that inter-rater reliability for identifying ALL injuries on MRI would not differ between an ACL-intact or ACL-injured cohort.
Methods The institutional review board determined this study met the criteria for approval (File #02-16-34E).
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol
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No
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(Month), 2019: pp 1-6
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Electronic medical records were queried to identify patients with a lower-extremity MRI (Current Procedural Terminology code 73721). These patients were then placed into the control (ACL intact; diagnoses: chondromalacia or meniscal tear) or study (ACL injured; diagnoses: complete ACL tear) group. Patients with multiligamentous knee injury, chronic ACL injury (greater than 6 months), and previous ligament injury/ surgery were excluded. Two fellowship-trained musculoskeletal radiologists evaluated each MRI for the presence of the ALL and ALL injury. Each MRI was evaluated one time (no time constraint) by each radiologist, separately. The radiologists had 21 years and 18 years of practice experience. The MRI specifics and procedure have been previously published by several of our authors.7 All MRIs were performed on 1.5-Tesla machines without contrast at 1 of 2 scanner sites with the patient supine and knee extended. Scanner sequences can be found in Table 1. The protocol for identifying the ALL on MRI previously defined by Helito et al.6 was used and reviewed by the musculoskeletal radiologist within a week before conducting this study; however, our study did not stratify ALL identification into femoral, meniscal, and tibial portions. The protocol involves localizing the femoral attachment of the ALL via its close proximity to the insertion of the fibular collateral ligament (Fig 1).7 The ALL was deemed visual if at least one-third (proximal, middle, distal) of the ligament was seen on MRI. ALL injury was defined as increased signal, overt tear, or avulsion fracture at the femoral or tibial attachment sites, if visible. The radiologists also noted any other knee pathology (i.e., effusion, lateral capsular injury, Segond fracture, and presence of bone bruising). Inter-rater reliability was assessed between raters 1 and 2 concerning their ability to visualize the ALL and identify an ALL injury. Statistical Analysis Standard descriptive statistics, including measures of central tendency, variance, as well as frequencies and proportions, were calculated for all data points. For bivariate analyses, the Fisher exact test was used for categorical data to determine statistical differences. Continuous data were evaluated for statistical
differences between groups using a Wilcoxon rank sum test. Inter-rater agreement was assessed between all radiologists for each data point of interest. Interobserver reliability was assessed using Cohen’s Kappa coefficient.13 All analyses were performed using SAS 9.4 (SAS Institute, Cary, NC).
Results Of the 273 MRIs reviewed for this study, 75 MRIs (27.5%) were excluded. The most common reason for exclusion was because the radiologist did not use the standardized ALL protocol referenced previously. After exclusion, there were 198 (72.5%) cases available for analysis, including 82 (41.4%) study patients and 116 (58.6%) control patients (Fig 2). Patient age differed between groups (P < .0001), but sex distribution was similar (P ¼ .0609) (Table 2). Concerning all MRIs, raters 1 and 2 were able to visualize the ALL in 195 of 198 (98.5%) and 193 of 198 (97.5%), respectively. In the ACL-intact cohort, the ALL was visualized in 114 of 116 (98.3%) and 111 of 116 (95.7%) of MRIs by raters 1 and 2, respectively. In the ACL-injured group, the ALL visualization rates were 98.8% and 100% by raters 1 and 2, respectively. Inter-rater reliability for ALL visualization in the entire sample and after cohort stratification was near perfect (kappa > 0.88) (Table 3). Pertaining to ALL injuries on MRI, visualization rates were stratified by observer and group (Table 4). For the entire sample, raters 1 and 2 visualized an ALL injury in 42 of 198 (21.2%) and 50 of 198 (25.3%) MRIs, respectively. In the ACL intact group, only 3 (2.6%) and 2 (1.7%) ALL injuries were seen by raters 1 and 2, respectively. In the ACL-injured group, ALL injuries were seen in 39 of 82 (47.6%) and 48 of 82 (58.5%) MRIs by raters 1 and 2, respectively. Inter-rater reliability for the ability to visualize an ALL injury was near perfect (kappa ¼ 0.95; confidence interval 0.88-1.0) for the ACL-intact group and minimal (kappa ¼ 0.38; confidence interval 0.17-0.58) for the ACL-injured group (Table 4). Raters 1 and 2 identified 42 and 50 ALL injuries among all included MRIs, respectively. Both raters independently recorded the aforementioned results in Table 5. The most common abnormality associated with ALL
Table 1. MRI Specifications Sequence Axial Fat Sat FSE Cor PD fs FSE Sag T1 FSE Sag PC-Fat Sat FSE Sag T2
TE 36 36 M in-Full 30 12
TR 3,384 2,634 517 3,134 28
ETL 8 8 3 8 8
BW 20.8 20.8 35.7 20.8 20.8
Freq 320 288 512 320 320
Phase 224 224 256 224 192
NEX 2 2 2 2 0.75
FOV 14 14 14 14 16
Space 0.5 0.5 0 0 0
Thick 4 4 4 4 2
BW, bandwidth (Hz); Cor, coronal; ETL. echo train length; FOV, field of view (cm); Freq, frequency (MHz); fs, fat suppressed; FSE, fait spion echo; NEX, number of excitations; PD, proton density; Sag, sagittal; Sat, saturation; Space, slice spacing (mm); TE, echo time (ms); Thick, slice thickness (mm); TR, repetition time (ms).
CONCURRENT ALL AND ACL INJURY ON MRI
3
Fig 1. Flow diagram depicting sample and cohort size, as well the number of excluded MRIs with respective criteria. (ACL, anterior cruciate ligament; ALL, anterolateral ligament; MRI, magnetic resonance imaging.)
injury on MRI was an effusion (80.0, 100.0%) followed by bone bruising (74.0, 95.2%), lateral capsule injury (38.0, 59.5%), and Segond fracture (11.9, 16.0%).
Discussion This study revealed that, with near perfect inter-rater agreement, at least part of the ALL was visualized in more than 95% of MRIs despite the degree of ACL integrity. It also showed that the mean rate of identifying an ALL injury in the setting of a complete ACL tear on MRI was 53.05% with minimal inter-rater agreement between radiologist. Secondary findings were that effusions and bone bruising were commonly visualized on MRI in the setting of ALL injuries. In addition, a Segond fracture was seen in 11.90% to 16.00% of MRIs also demonstrating ALL injury. This study aimed to assess the utility of MRI to visualize the ALL in the setting of an ACL injury. It was
found that the ALL was at least partially visualized in more than 95% of MRIs in this study despite the degree of ACL integrity. Moreover, there was near-perfect inter-rater agreement when it came to ALL visualization rates between the 2 musculoskeletal radiologists. This finding is in line with a previous study by Helito et al.,6 in which 2 radiologists, who used the same ALL identification protocol as we used, prospectively assessed 42 1.5-Tesla MRI scans without ACL injuries, visualizing at least part of the ALL in 98% of their sample with relatively good interobserver agreement. Of note, we included coronal proton densityeweighted sequences in our protocol, which Helito et al.6 found to be superior to T1 when assessing the ALL. In contrast, a prospective case control study by Devitt et al.8 reported that the ALL was partially visualized in only 64% of 3-Tesla MRIs without ACL injuries and 72% of MRIs with ACL injuries. They go on to discuss
Fig 2. (A) Axial imaging of the right knee with the biceps tendon (green arrow), the fibular collateral ligament (FCL) (red arrow), the anterolateral ligament (ALL) (yellow arrow), and the iliotibial (IT) band (white arrow). Scanning the axial images and finding the FCL insertion, just anterior to this is the approximate femoral insertion of the ALL. Following this caudad, you should be able to track the thickened tissue between the FCL and the IT band. (B) On the coronal image of the right knee, the FCL insertion is located. This is right near the ALL femoral insertion (white arrow). The ALL moves superficial to the popliteus tendon (green arrow); after this, the tendon gives off the meniscal branch (yellow arrow). It is superficial to the inferior lateral geniculate arteries and then inserts approximately 5 to 6 mm distal on the proximal tibia (red arrow). Reproduced with permission from Hartigan et al.7
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B. L. YOUNG ET AL.
Table 2. Demographics of 198 Included MRIs ACL-Injured (n ¼ 82) Age, y Median Range Sex, n (%) Male
Table 4. Ability to Visualize ALL Injuries on MRI
ACL-Intact (n ¼ 116)
Rater 2 P Value <.0001
22.2 11-48
36.2 11-71
49 (59.76%)
53 (45.69%)
.0609
NOTE. Shown are the demographics of the control (ACL-intact) and study (ACL-injured) groups. P values for age and sex were calculated via Wilcoxon and Fisher exact 2-tailed tests, respectively. ACL, anterior cruciate ligament; MRI, magnetic resonance imaging.
that such variation among ALL visualization rates in the literature may be explained by discrepancies in the anatomical description of the ALL.8 In another recent study, the average visualization rate of the ALL on 3-Tesla MRI between 3 radiologists was 68%, with relatively poor agreement between observers.14 From a broader perspective, a recent systematic review of the literature in 2018 found that the MRI visualization rate of the ALL in the setting of ACL injury ranges from 76% to 100%, highlighting even further inconsistencies of ALL detection on MRI.15 This study also aimed to assess the utility of MRI in diagnosing ALL injuries in the setting of concomitant ACL injury. Our data showed that radiologists identified ALL injuries in 21.21% and 25.25% of the MRIs evaluated in this study. Moreover, they identified concomitant ALL injury in a mean 53.05% of MRIs with an injured ACL. For comparison, a wide range of concomitant ALL and ACL injury rates has been reported in a recent systematic review of the literature, 10.8% to 62.5%.15 In our study, we found that there was minimal agreement between musculoskeletal radiologists when it came to their ability to visualize an ALL injury in the setting of an injured ACL. In contrast, agreement improved between radiologists in the setting of an intact ACL. These findings are in line with Table 3. Ability to Visualize the ALL on MRI Rater 2 Rater 1 Entire sample No Yes Control (ACL-intact) group No Yes Study (ACL-injury) group No Yes
Inter-rater Reliability
No
Yes
0 5
3 190
0.92 (0.86-0.97)
0 5
2 109
0.88 (0.79-0.97)
0 0
1 81
0.98 (0.93-1.0)
NOTE. Shown is the inter-rater reliability for determining ALL visualization on MRI. Confidence intervals for inter-rater reliability can be found in parentheses. ALL, anterolateral ligament; MRI, magnetic resonance imaging.
Rater 1 Entire sample No Yes Control (ACL-intact) group No Yes Study (ACL-injury) group No Yes
Inter-rater Reliability
No
Yes
130 10
18 32
0.92 (0.86-0.97)
106 2
1 1
0.95 (0.88-1.0)
24 8
17 31
0.38 (0.17-0.58)
NOTE. Shown is the inter-rater reliability of whether an ALL injury was visualized or not on MRI. Confidence intervals for inter-rater reliability can be found in parentheses. ALL, anterolateral ligament; MRI, magnetic resonance imaging.
findings by Marshall et al.,14 who showed that 3 radiologists had poorer agreement when classifying ALL injury status if the ACL was injured versus not injured. These findings suggest that the visualization of ALL abnormalities on MRI may be suboptimal in the setting of concurrent ACL injury. Possible explanations for this may include distracting injury phenomenon on MRI reading or difficulty with signal differentiation by the observer over the area of the ALL in the setting of large effusion and nearby traumatic injury. A secondary goal of this study was to explore the incidence of and characterize abnormal MRI findings associated with ALL injuries. It is not surprising that an effusion was present in 80% to 100% of MRIs with ALL injuries, as a trauma likely occurred before an MRI of the knee was obtained. On the basis of retrospective review of 193 MRIs of patients who underwent ACL reconstruction, Song et al.16 found that bony contusions of the lateral femoral condyle and lateral tibial plateau (but not the medial femoral condyle or medial tibial plateau) were significantly associated with ALL injury. We found a similar high incidence of bone bruising in patients with an ALL injury. Pertaining to Segond fractures associated with ALL injury visualized on MRI, the incidence is highly variable, ranging from 1.9% to 36.6%.16 We report that a Segond fracture was Table 5. Abnormal Findings Associated With ALL Injuries on MRI ALL injuries, n Associated injuries, n (%) Effusion Lateral capsule injury Segond fracture Bone bruising
Rater 1 42 42 25 5 40
(100.00) (59.52) (11.90) (95.24)
Rater 2 50 40 19 8 37
(80.00) (38.00) (16.00) (74.00)
NOTE. Shown is the proportion of ALL injuries seen on MRI that were accompanied by other MRI abnormalities. ALL, anterolateral ligament; MRI, magnetic resonance imaging.
5
CONCURRENT ALL AND ACL INJURY ON MRI
seen in 11.9% and 16.0% of MRIs also demonstrating ALL injury by our radiologists. De Maeseneer et al.17 retrospectively reviewed the MRIs of 13 cases of a Segond fracture and found that the ALL inserted on the Segond bone fragment in 10 of 13 (77%) cases. Similarly, Porrino et al.10 evaluated 20 knee MRIs with a Segond fracture and found that the ALL was attached to the fracture fragment in all but one case limited by anatomic distortion. However, it should be recognized that injury to the ALL is more likely to be in the absence of a Segond fracture. It should again be noted that this study deemed the ALL was visible even if only part of the ligament was seen on MRI. This may explain our high ALL visualization rates and inter-rater agreement on MRI, as well as the lower inter-rater agreement concerning visualization of ALL injuries. Other studies have stratified the ability to visualize the ALL on MRI into 3 regions: femoral, meniscal (middle), and tibial. Marshall et al. also reported on ALL visualization on MRI between 3 radiologists in an ACL-intact and -injured cohort. They found that the ALL could be fully and partially visualized in 11% and 68% of patients, respectively. However, they reported universally poor inter-rater agreement on the radiologists’ ability to visualize the ALL when stratified into regions other than when it came to visualizing the middle segment of the ALL in an ACL-injured cohort.14 Limitations There were several limitations to this study. First, the data compiled by observers in this study were subject to variable inter-rater reliability. Although we were able to demonstrate acceptable agreement between our reviewers for ALL visualization on MRI in general, we did find less-than-ideal agreement between observers concerning their ability to visualize an ALL injury on MRIs with an injured ACL. This poor inter-rater reliability should be taken into account when interpreting our findings concerning knee abnormalities found in association with ALL injury in ACL-deficient knees, as those findings are dependent on the presence of an ALL injury seen on MRI. Another limitation is that we were unable to compare our MRI data with a reference gold standard, direct visualization by dissection.
Conclusions The ALL was reliably visualized on MRI irrespective of whether the ACL was intact or torn. However, ALL injuries were not reliably diagnosed on MRI in the setting of an ACL tear. Poor interobserver reliability shows the potential for false-positive and -negative interpretation. These findings suggest that in this study, ALL injuries could not be accurately diagnosed in the presence of an ACL tear using MRI. On the basis of
these findings, it is recommended that physicians should not rely on MRI to diagnose an ALL injury in the presence of an ACL injury.
Acknowledgments We thank OrthoCarolina Research Institute (OCRI) for data management, statistical analysis, and study oversight and Mecklenburg Radiology Associates for study participation and data collection.
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examination: A systematic review. Arthroscopy 2018;34: 2728-2738. 16. Song GY, Zhang H, Wang QQ, Zhang J, Li Y, Feng H. Bone contusions after acute noncontact anterior cruciate ligament injury are associated with knee joint laxity, concomitant meniscal lesions, and anterolateral ligament abnormality. Arthroscopy 2016;32:2331-2341. 17. De Maeseneer M, Boulet C, Willekens I, et al. Segond fracture: Involvement of the iliotibial band, anterolateral ligament, and anterior arm of the biceps femoris in knee trauma. Skeletal Radiol 2015;44:413-421.