Published online August 21, 2007, 10.1148/rg.e26
(RadioGraphics 2007;27:e26.)
A more recent version of this article appeared on November 1, 2007
© RSNA, 2007
Cyclops Lesions That Occur in the Absence of Prior Anterior Ligament Reconstruction1
Brandon R. Runyan, MD,
Laura W. Bancroft, MD,
Jeffrey J. Peterson, MD,
Mark J. Kransdorf, MD,
Thomas H. Berquist, MD, and
Cedric J. Ortiguera, MD
1 From the Departments of Radiology (B.R.R., L.W.B., J.J.P., M.J.K., T.H.B) and Orthopedic Surgery (C.J.O.), Mayo Clinic, 4500 San Pablo Blvd, Jacksonville, Fla 32224. Presented as an education exhibit at the 2006 RSNA Annual Meeting. Received April 30, 2007; revision requested June 20; revision received and accepted July 27. All authors have no financial relationship to disclose.
Address correspondence to B.R.R. (e-mail: Runyan.Brandon{at}mayo.edu).
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Abstract
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Loss of full extension after anterior cruciate ligament (ACL) reconstruction, with development of an audible and palpable "clunk" with terminal extension was first described by Jackson and Schaefer as "cyclops syndrome." This syndrome, which is the result of a fibrous nodule (termed a cyclops nodule), has recently been described in patients who have sustained ACL injury but have not undergone reconstructive surgery. From 2001 to 2006, the authors identified 10 patients (five women and five men, ages 27–76 years) with cyclops nodules seen at magnetic resonance (MR) imaging. All patients had a history of trauma but no history of ACL reconstruction. The cyclops lesions had a mean size of 16 x 12 x 11 mm, with 90% of them located just anterior to the distal ACL. MR imaging showed a well-defined, somewhat heterogeneous soft-tissue nodule with a signal intensity typically similar to that of skeletal muscle. The authors suspect that the cause of cyclops lesions that occur in the absence of ACL reconstruction is similar to that suggested in the classic postoperative patient. Cyclops syndrome should be suspected in any patient in whom an ACL nodule is identified at MR imaging, and similarly a cyclops nodule should be considered as a possible cause of loss of extension in any patient who has sustained ACL injury.
Movies available at http://radiographics.rsnajnls.org/cgi/content/full/e26/DC1.
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Introduction
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Cyclops syndrome was first described by Jackson and Schaefer in 1990 in patients who had undergone anterior cruciate ligament (ACL) reconstruction with a patellar autograft (1). In the article, the authors reported that 13 of 230 (5.7%) patients who underwent patellar autograft ACL reconstruction lost full extension and developed an audible and palpable "clunk" with terminal extension (1). At arthroscopy, the loss of extension was seen to be caused by a soft-tissue nodule abutting the anterior notch. The authors termed this constellation of findings cyclops syndrome to emphasize that arthroscopy revealed a soft-tissue mass with surface vessels reminiscent of the eye of the cyclops of Greek mythology (1).
Further experience with this lesion has shown that patients typically present with pain and loss of extension 8 to 32 weeks (16 weeks on average) after the ACL reconstruction (1–12). The frequency of cyclops syndrome in patients undergoing ACL reconstruction varies widely in the literature, from 2% to 24 % (1–4). A decreased frequency of cyclops syndrome has been shown in patients who regain complete extension early in the postoperative period and in those in whom synthetic graft materials are used (4).
Although the original description of cyclops syndrome was in patients who had undergone ACL reconstruction, more recent reports have documented its occurrence after ACL injury in the absence of ACL reconstruction. In this article, we review cyclops lesions in 10 proved cases in which the lesions occurred in the absence of reconstruction. In addition to reviewing the imaging features of these lesions, we propose a mechanism for their occurrence and correlate the magnetic resonance (MR) imaging appearance of cyclops nodules with the underlying histologic findings.
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Pathogenesis of Cyclops Syndrome
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On the basis of pathologic specimens, Jackson and Schaefer proposed that the nodule identified at arthroscopy was the result of a natural fibroproliferative process that results from drilling debris or from broken graft fibers (1). They postulated that the development of the fibrous cyclops nodule was stimulated by residual tissue at the rim of the tibial tunnel (1). This residual tissue, pushed into the joint during placement of the graft, was believed to contribute to the fibroproliferative process and granulation tissue that forms the cyclops lesion (1). They also postulated that anterior placement of the tibial tunnel exacerbated problems created by the reactive tissue. Although this theory has been disputed by other authors (4), Jackson and Schaefer dramatically reduced their frequency of cyclops syndrome by thoroughly debriding the tissue at the articular aspect of the tibial tunnel and by avoiding anterior positioning of the tibial tunnel, on the basis of their proposed mechanism for pathogenesis (1).
Subsequently, Marzo et al suggested that microtrauma related to the position of the graft in the anterior third of the tibia caused graft impingement on the notch at full extension, leading to the formation of scar tissue (2). Regardless of the mechanism of pathogenesis, microscopic analysis of cyclops nodules after ACL reconstruction reveals they are composed of dense fibroconnective tissue, rich in newly formed vessels, with variable content of cartilage, osseous tissue, and occasionally necrotic lamellar bone (1,3), a histologic composition consistent with microtrauma pathophysiology.
The microtrauma pathophysiology proposed by Marzo et al (2) likely also plays an important role in the occurrence of cyclops lesions after ACL injury without reconstruction (Movie 1). Cyclops lesions that occur after trauma, even remote trauma, have a similar spectrum of pathologic (13–15) and imaging findings, supporting a similar pathophysiology. We speculate that cyclops nodules that occur in patients after trauma in whom there is a clinically or radiologically intact ACL are likely also the result of microtrauma to subclinically torn ACL fibers.
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Our Experience with Cyclops Lesions That Occur after ACL Injury without Reconstruction
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Between 2001 and 2007, we identified 10 patients with cyclops lesions without ACL reconstruction. The study group consisted of five men and five women, with a mean age of 53.3 years (range, 27–76 years). Patients were examined in our Department of Orthopedic Surgery on initial presentation for evaluation of knee pain. All patients had a history of trauma.
All MR imaging examinations were performed with a 1.5-T magnet and included coronal T1-weighted spin-echo and sagittal fast-spin-echo (FSE) proton-density images, T2-weighted fat-suppressed images, and axial FSE fat-suppressed proton-density images. Double-echo steady-state (DESS) gradient sequences were available for nine of the patients. In addition to helping determine the size and shape of the cyclops lesion, the MR signal characteristics of the lesion were assessed in relation to those of skeletal muscle as either hyperintense, isointense, or hypointense. Lesions were also subjectively evaluated as either homogeneous or heterogeneous, and the integrity of the ACL was evaluated and categorized as intact, partially torn, or completely torn. Determination of a complete tear of the ACL was made by identification of direct signs of disruption, including focal or generalized increased signal within the ACL with discontinuity or focal nonvisualization, nonvisualization of the ACL, or an irregular, wavy anterior ACL contour (16,17).
A partial tear of the ACL was suggested when the ACL demonstrated abnormal intrasubstance signal intensity, abnormal bowing, or inconsistent visualization of intact fibers with all pulse sequences (18,19). Additional data reviewed included trauma history, presenting complaint, and correlation with arthroscopic findings, which were available in six of the 10 patients.
Although all 10 patients presented for evaluation of knee pain after trauma, eight (80%) also had loss of extension at physical examination and three (30%) had a history of arthroscopic knee surgery. Specifically, one patient had arthroscopic repair of a tibial plateau fracture (Fig 1), one patient had arthroscopic meniscectomy 4 months prior to examination, and one patient had a remote history of arthroscopy for a "cartilage tear" (Fig 2). At MR imaging, the ACL was partially torn in five of the 10 patients, completely torn in one, and normal in the remaining four patients. The lesions were proved at arthroscopy in six of 10 cases, with histology obtained in one. The cyclops lesions had an average size of 15 x 12 x 10 mm (range, 5 x 10 x 4 to 22 x 13 x 14 mm). The location of the nodule was anterior to the ACL (Fig 3) in nine patients and lateral to the ACL in the remaining case (Fig 4). Interestingly, the patient with an atypical location of the cyclops lesion had lateral knee pain and no loss of extension. Patient demographics, history, and clinical symptoms are summarized in Table 1.
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Figure 1a. Posttrauma cyclops lesion in a 31-year-old woman with a chronic ACL tear and repaired tibial plateau fracture after skiing accident 1 year before. (a) Axial proton-density fat-suppressed image (repetition time msec/echo time msec, 3000/25) demonstrates intermediate-intensity cyclops nodule (arrow) in the intercondylar notch, joint effusion, and a popliteal cyst. (b) Sagittal proton-density image (3000/25) shows a slightly heterogeneous cyclops nodule (arrow) anterior to the ACL attachment. (c, d) Correlative arthroscopic images demonstrate the proximally torn ACL (arrow) and the cyclops lesion (*) (c) before and (d) during elevation by the probe.
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Figure 1b. Posttrauma cyclops lesion in a 31-year-old woman with a chronic ACL tear and repaired tibial plateau fracture after skiing accident 1 year before. (a) Axial proton-density fat-suppressed image (repetition time msec/echo time msec, 3000/25) demonstrates intermediate-intensity cyclops nodule (arrow) in the intercondylar notch, joint effusion, and a popliteal cyst. (b) Sagittal proton-density image (3000/25) shows a slightly heterogeneous cyclops nodule (arrow) anterior to the ACL attachment. (c, d) Correlative arthroscopic images demonstrate the proximally torn ACL (arrow) and the cyclops lesion (*) (c) before and (d) during elevation by the probe.
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Figure 1c. Posttrauma cyclops lesion in a 31-year-old woman with a chronic ACL tear and repaired tibial plateau fracture after skiing accident 1 year before. (a) Axial proton-density fat-suppressed image (repetition time msec/echo time msec, 3000/25) demonstrates intermediate-intensity cyclops nodule (arrow) in the intercondylar notch, joint effusion, and a popliteal cyst. (b) Sagittal proton-density image (3000/25) shows a slightly heterogeneous cyclops nodule (arrow) anterior to the ACL attachment. (c, d) Correlative arthroscopic images demonstrate the proximally torn ACL (arrow) and the cyclops lesion (*) (c) before and (d) during elevation by the probe.
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Figure 1d. Posttrauma cyclops lesion in a 31-year-old woman with a chronic ACL tear and repaired tibial plateau fracture after skiing accident 1 year before. (a) Axial proton-density fat-suppressed image (repetition time msec/echo time msec, 3000/25) demonstrates intermediate-intensity cyclops nodule (arrow) in the intercondylar notch, joint effusion, and a popliteal cyst. (b) Sagittal proton-density image (3000/25) shows a slightly heterogeneous cyclops nodule (arrow) anterior to the ACL attachment. (c, d) Correlative arthroscopic images demonstrate the proximally torn ACL (arrow) and the cyclops lesion (*) (c) before and (d) during elevation by the probe.
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Figure 2a. Cyclops lesion in a 45-year-old-man with 2-year history of chronic ACL tear and loss of extension.(a) Sagittal FSE proton-density image demonstrates the well-circumscribed, slightly heterogeneous cyclops nodule. (b) Coronal DESS image demonstrates a soft-tissue nodule in the anterior intercondylar notch.
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Figure 2b. Cyclops lesion in a 45-year-old-man with 2-year history of chronic ACL tear and loss of extension.(a) Sagittal FSE proton-density image demonstrates the well-circumscribed, slightly heterogeneous cyclops nodule. (b) Coronal DESS image demonstrates a soft-tissue nodule in the anterior intercondylar notch.
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Figure 3a. Posttrauma cyclops nodule in a 41-year-old-man with chronic ACL tear after hyperextension 2 years before. (a) Coronal T1-weighted image through the intercondylar notch shows a well-circumscribed nodule (arrow) isointense to skeletal muscle. (b) Coronal DESS image demonstrates cyclops lesion (arrow) that is heterogeneously hyperintense to muscle.
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Figure 3b. Posttrauma cyclops nodule in a 41-year-old-man with chronic ACL tear after hyperextension 2 years before. (a) Coronal T1-weighted image through the intercondylar notch shows a well-circumscribed nodule (arrow) isointense to skeletal muscle. (b) Coronal DESS image demonstrates cyclops lesion (arrow) that is heterogeneously hyperintense to muscle.
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Figure 4a. Cyclops nodule in an atypical position, lateral to the anterior intercondylar notch, in a 67-year-old woman with normal ACL and history of trauma four months before with partial meniscectomy. Sagittal FSE proton-density (a) and FSE T2-weighted (b) images slightly lateral to the anterior intercondylar notch demonstrate a heterogeneous nodule (arrow) abutting the anterior horn of the lateral meniscus.
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Figure 4b. Cyclops nodule in an atypical position, lateral to the anterior intercondylar notch, in a 67-year-old woman with normal ACL and history of trauma four months before with partial meniscectomy. Sagittal FSE proton-density (a) and FSE T2-weighted (b) images slightly lateral to the anterior intercondylar notch demonstrate a heterogeneous nodule (arrow) abutting the anterior horn of the lateral meniscus.
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MR imaging signal characteristics of the cyclops lesions are summarized in Table 2. On T1-weighted images, seven of the 10 cyclops lesions were hyperintense to skeletal muscle and three were isointense. Seven of the 10 cyclops nodules were isointense to muscle on FSE T2-weighted images, and the other three were hyperintense to muscle. On gradient DESS images acquired in nine of the patients, six nodules were isointense to muscle and three were hyperintense. On proton-density images, six nodules had heterogeneous signal intensity, three were isointense to muscle, and one was hypointense.
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Discussion
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Cyclops lesions that occur after ACL reconstruction are a well-recognized phenomenon; posttrauma cyclops lesions in the absence of prior ACL reconstruction are less well recognized. Regardless of any association with ACL grafting, cyclops lesions are important to recognize because they are typically symptomatic and readily amenable to arthroscopic resection (Movie 2, Fig 5).
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Figure 5a. Posttrauma cyclops lesion in a 27-year-old woman with a high-grade partial-thickness ACL tear and loss of extension. (a) Sagittal FSE T2-weighted image demonstrates a complete tear of the ACL (arrow), which was later characterized as a high-grade partial-thickness tear at arthroscopy. (b) Coronal FSE T2-weighted image shows a small cyclops nodule (arrow) in the anterior intercondylar notch. Note the lateral femoral condylar bone contusion and associated medial collateral ligament tear. (c-e) Arthroscopic images show the well-defined cyclops nodule (arrow) protruding from the anteromedial bundle of the ACL (c) before, (d) during, and (e) after debridement. (f) Histomicrograph at low power demonstrates fibroblastic and fibrotendinous areas throughout the central portion of the section, with neovascularity (arrowheads). (Hematoxylin-eosin stain; original magnification, x10.) (g) Histomicrograph at high power demonstrates small foci of hemosiderin (arrow) and blood vessels (arrowheads) within a matrix of fibrotendinous tissue. (Hematoxylin-eosin stain; original magnification, x40.)
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Figure 5b. Posttrauma cyclops lesion in a 27-year-old woman with a high-grade partial-thickness ACL tear and loss of extension. (a) Sagittal FSE T2-weighted image demonstrates a complete tear of the ACL (arrow), which was later characterized as a high-grade partial-thickness tear at arthroscopy. (b) Coronal FSE T2-weighted image shows a small cyclops nodule (arrow) in the anterior intercondylar notch. Note the lateral femoral condylar bone contusion and associated medial collateral ligament tear. (c-e) Arthroscopic images show the well-defined cyclops nodule (arrow) protruding from the anteromedial bundle of the ACL (c) before, (d) during, and (e) after debridement. (f) Histomicrograph at low power demonstrates fibroblastic and fibrotendinous areas throughout the central portion of the section, with neovascularity (arrowheads). (Hematoxylin-eosin stain; original magnification, x10.) (g) Histomicrograph at high power demonstrates small foci of hemosiderin (arrow) and blood vessels (arrowheads) within a matrix of fibrotendinous tissue. (Hematoxylin-eosin stain; original magnification, x40.)
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Figure 5c. Posttrauma cyclops lesion in a 27-year-old woman with a high-grade partial-thickness ACL tear and loss of extension. (a) Sagittal FSE T2-weighted image demonstrates a complete tear of the ACL (arrow), which was later characterized as a high-grade partial-thickness tear at arthroscopy. (b) Coronal FSE T2-weighted image shows a small cyclops nodule (arrow) in the anterior intercondylar notch. Note the lateral femoral condylar bone contusion and associated medial collateral ligament tear. (c-e) Arthroscopic images show the well-defined cyclops nodule (arrow) protruding from the anteromedial bundle of the ACL (c) before, (d) during, and (e) after debridement. (f) Histomicrograph at low power demonstrates fibroblastic and fibrotendinous areas throughout the central portion of the section, with neovascularity (arrowheads). (Hematoxylin-eosin stain; original magnification, x10.) (g) Histomicrograph at high power demonstrates small foci of hemosiderin (arrow) and blood vessels (arrowheads) within a matrix of fibrotendinous tissue. (Hematoxylin-eosin stain; original magnification, x40.)
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Figure 5d. Posttrauma cyclops lesion in a 27-year-old woman with a high-grade partial-thickness ACL tear and loss of extension. (a) Sagittal FSE T2-weighted image demonstrates a complete tear of the ACL (arrow), which was later characterized as a high-grade partial-thickness tear at arthroscopy. (b) Coronal FSE T2-weighted image shows a small cyclops nodule (arrow) in the anterior intercondylar notch. Note the lateral femoral condylar bone contusion and associated medial collateral ligament tear. (c-e) Arthroscopic images show the well-defined cyclops nodule (arrow) protruding from the anteromedial bundle of the ACL (c) before, (d) during, and (e) after debridement. (f) Histomicrograph at low power demonstrates fibroblastic and fibrotendinous areas throughout the central portion of the section, with neovascularity (arrowheads). (Hematoxylin-eosin stain; original magnification, x10.) (g) Histomicrograph at high power demonstrates small foci of hemosiderin (arrow) and blood vessels (arrowheads) within a matrix of fibrotendinous tissue. (Hematoxylin-eosin stain; original magnification, x40.)
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Figure 5e. Posttrauma cyclops lesion in a 27-year-old woman with a high-grade partial-thickness ACL tear and loss of extension. (a) Sagittal FSE T2-weighted image demonstrates a complete tear of the ACL (arrow), which was later characterized as a high-grade partial-thickness tear at arthroscopy. (b) Coronal FSE T2-weighted image shows a small cyclops nodule (arrow) in the anterior intercondylar notch. Note the lateral femoral condylar bone contusion and associated medial collateral ligament tear. (c-e) Arthroscopic images show the well-defined cyclops nodule (arrow) protruding from the anteromedial bundle of the ACL (c) before, (d) during, and (e) after debridement. (f) Histomicrograph at low power demonstrates fibroblastic and fibrotendinous areas throughout the central portion of the section, with neovascularity (arrowheads). (Hematoxylin-eosin stain; original magnification, x10.) (g) Histomicrograph at high power demonstrates small foci of hemosiderin (arrow) and blood vessels (arrowheads) within a matrix of fibrotendinous tissue. (Hematoxylin-eosin stain; original magnification, x40.)
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Figure 5f. Posttrauma cyclops lesion in a 27-year-old woman with a high-grade partial-thickness ACL tear and loss of extension. (a) Sagittal FSE T2-weighted image demonstrates a complete tear of the ACL (arrow), which was later characterized as a high-grade partial-thickness tear at arthroscopy. (b) Coronal FSE T2-weighted image shows a small cyclops nodule (arrow) in the anterior intercondylar notch. Note the lateral femoral condylar bone contusion and associated medial collateral ligament tear. (c-e) Arthroscopic images show the well-defined cyclops nodule (arrow) protruding from the anteromedial bundle of the ACL (c) before, (d) during, and (e) after debridement. (f) Histomicrograph at low power demonstrates fibroblastic and fibrotendinous areas throughout the central portion of the section, with neovascularity (arrowheads). (Hematoxylin-eosin stain; original magnification, x10.) (g) Histomicrograph at high power demonstrates small foci of hemosiderin (arrow) and blood vessels (arrowheads) within a matrix of fibrotendinous tissue. (Hematoxylin-eosin stain; original magnification, x40.)
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Figure 5g. Posttrauma cyclops lesion in a 27-year-old woman with a high-grade partial-thickness ACL tear and loss of extension. (a) Sagittal FSE T2-weighted image demonstrates a complete tear of the ACL (arrow), which was later characterized as a high-grade partial-thickness tear at arthroscopy. (b) Coronal FSE T2-weighted image shows a small cyclops nodule (arrow) in the anterior intercondylar notch. Note the lateral femoral condylar bone contusion and associated medial collateral ligament tear. (c-e) Arthroscopic images show the well-defined cyclops nodule (arrow) protruding from the anteromedial bundle of the ACL (c) before, (d) during, and (e) after debridement. (f) Histomicrograph at low power demonstrates fibroblastic and fibrotendinous areas throughout the central portion of the section, with neovascularity (arrowheads). (Hematoxylin-eosin stain; original magnification, x10.) (g) Histomicrograph at high power demonstrates small foci of hemosiderin (arrow) and blood vessels (arrowheads) within a matrix of fibrotendinous tissue. (Hematoxylin-eosin stain; original magnification, x40.)
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Cyclops lesions were initially reported to occur relatively soon after ACL repair, with an average interval of 16 weeks between ACL reconstruction and arthroscopy (1). Recent reports describe symptoms, pathology, and imaging appearances of cyclops lesions as long as 24 years after trauma (11–15).
The imaging morphology of a nodule in the intercondylar notch is characteristic of cyclops lesions and is similar in subsets of patient who have undergone ACL reconstruction and those who have not. Cyclops lesions are typically small, with Bradley et al reporting a mean size of 13 x 12 x 12 mm in a review of 20 lesions (6). These lesions can be either pedunculated or sessile (Fig 6), and are typically adjacent to the ACL. Similar to the series of Bradley et al (6), the cyclops lesions in our series had an average size of 15 x 12 x 10 mm. In accord with previous studies, the location of the cyclops nodule in our series was predominantly anterior to the ACL.
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Figure 6a. Atypical-appearing cyclops lesion in a 56-year-old man who bumped his knee on a boat ladder 2 months before. Since then, his knee "gives way" and he has had loss of extension. (a) Axial FSE proton-density fat-suppressed image depicts a small irregular nodule (arrow) in the intercondylar notch that is slightly hypointense to skeletal muscle. This was a somewhat different imaging characteristic from that of other lesions and may be due to a higher hemosiderin content. (b) Correlating arthroscopic image shows the cyclops lesion and the sprained ACL.
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Figure 6b. Atypical-appearing cyclops lesion in a 56-year-old man who bumped his knee on a boat ladder 2 months before. Since then, his knee "gives way" and he has had loss of extension. (a) Axial FSE proton-density fat-suppressed image depicts a small irregular nodule (arrow) in the intercondylar notch that is slightly hypointense to skeletal muscle. This was a somewhat different imaging characteristic from that of other lesions and may be due to a higher hemosiderin content. (b) Correlating arthroscopic image shows the cyclops lesion and the sprained ACL.
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MR imaging is the modality of choice for identifying cyclops nodules after ACL reconstruction. In a series of 31 patients, Bradley et al found MR imaging to be 85% sensitive, 85% specific, and 85% accurate in the detection of cyclops nodules (6). Recht et al (5) originally described the MR imaging appearance of these lesions in a series of five patients, noting the characteristic morphology and location: a nodule that occurs in the anterior intercondylar notch (Fig 1). They also noted a characteristic mixed-to-intermediate signal appearance on T1-weighted and proton-density spin-echo images (5), an appearance which has been confirmed by others (6,7) (Fig 7).
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Figure 7a. Classic cyclops nodule that occurred after ACL reconstruction. (a) Sagittal FSE proton-density image through the knee demonstrates the intact anterior cruciate ligament graft. (b) Sagittal FSE proton-density image obtained slightly lateral to a demonstrates a slightly heterogeneous nodule (arrow) anterior to the graft. (c) Axial FSE proton-density fat-suppressed image again demonstrates the heterogeneous cyclops nodule (arrow) in the anterior intercondylar notch extending from the ACL graft (arrowhead).
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Figure 7b. Classic cyclops nodule that occurred after ACL reconstruction. (a) Sagittal FSE proton-density image through the knee demonstrates the intact anterior cruciate ligament graft. (b) Sagittal FSE proton-density image obtained slightly lateral to a demonstrates a slightly heterogeneous nodule (arrow) anterior to the graft. (c) Axial FSE proton-density fat-suppressed image again demonstrates the heterogeneous cyclops nodule (arrow) in the anterior intercondylar notch extending from the ACL graft (arrowhead).
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Figure 7c. Classic cyclops nodule that occurred after ACL reconstruction. (a) Sagittal FSE proton-density image through the knee demonstrates the intact anterior cruciate ligament graft. (b) Sagittal FSE proton-density image obtained slightly lateral to a demonstrates a slightly heterogeneous nodule (arrow) anterior to the graft. (c) Axial FSE proton-density fat-suppressed image again demonstrates the heterogeneous cyclops nodule (arrow) in the anterior intercondylar notch extending from the ACL graft (arrowhead).
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The MR imaging signal characteristics of the cyclops lesions in our series are similar to those in previous reports, with predominantly heterogeneous or intermediate signal intensity on T2-weighted FSE and proton-density images. On gradient DESS images, two-thirds (six of nine) of the nodules were isointense to skeletal muscle and one-third (three of nine) were hyperintense. DESS imaging was also helpful in differentiating the cyclops lesion from joint fluid and the adjacent ACL. The MR imaging, histopathologic, and arthroscopic findings in our study are similar to those described for cyclops lesions that occur after ACL reconstruction or after trauma (11,13).
Not all cyclops nodules lead to cyclops syndrome. Muellner et al (10), in a study of 119 patients who underwent patellar tendon autograft ACL reconstruction identified two distinct types of cyclops nodules: true cyclops nodules and cyclopoid scars. According to the authors, these nodules result from two different histomorphologic processes. True cyclops nodules are hard, contain bone or cartilaginous debris, and are typically associated with clinical cyclops syndrome. Cyclopoid scars, in contradistinction, contain only fibroproliferative tissue and typically do not cause cyclops syndrome, since the nodule is soft and is compressed by the bone and does not prevent full extension (10). These findings have several important implications. Patients presenting with lack of extension should be evaluated for cyclops nodules. Similarly, patients with cyclops nodules should be evaluated for loss of extension. Our experience is in keeping with previous reports that not all patients with cyclops nodules will demonstrate loss of extension. The distinction between cyclopoid scars and true cyclops nodules likely explains this difference.
A differential diagnostic consideration for a focal low-signal-intensity nodule adjacent to the knee joint would be nodular synovitis (focal pigmented villonodular synovitis). In our experience, the most useful imaging feature differentiating cyclops lesions is the intimate association of the lesion with the ACL or ACL remnant. A clinical history of extension loss is also helpful. In certain cases, however, the imaging distinction may be difficult. Additionally, there is overlap between the histology of nodular synovitis and cyclops nodules, and both entities have a stroma of collagen fibers with varying hemosiderin deposition.
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Implications
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For radiologists evaluating MR imaging of the knee, cyclops lesions are infrequently considered because they are typically associated with ACL reconstruction. A nodule in the intercondylar notch that causes loss of extension is, by definition, a cyclops nodule. Not all cyclops nodules cause a loss of extension, but patients with cyclops nodules discovered at MR imaging need further evaluation for loss of extension. Radiologists should be aware that cyclops syndrome is always a clinical consideration in patients presenting with loss of knee extension and has been reported as late as 24 years after initial injury (13). Because they can be readily excised arthroscopically, cyclops lesions should be excluded in examination of any patient with loss of extension.
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Acknowledgments
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Masaaki Takahashi, MD, Department of Orthopedic Surgery, Knee Surgery and Sports Medicine, Hamamatsu University School of Medicine, provided pathology images for the educational exhibit. Xochiquetzal J. Geiger MD, Assistant Professor of Pathology and Laboratory Medicine, Mayo Clinic College of Medicine, Jacksonville, Fla, provided histopathology images for this publication.
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Footnotes
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Abbreviations: ACL = anterior cruciate ligament, DESS = dual-echo steady state, FSE - fast spin echo
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References
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- Jackson DW, Schaefer RK. Cyclops syndrome: loss of extension following intra-articular anterior cruciate ligament reconstuction. Arthroscopy 1990;6:171–178.[Medline]
- Marzo JM, Bowen MK, Warren RF, Wickiewicz TL, Altchek DW. Intraarticular fibrous nodule as a cause of loss of extension following anterior cruciate ligament reconstruction. Arthroscopy 1992;8:10–18.[Medline]
- Delcogliano A, Franzese S, Branca A, Magi M, Fabbriciani C. Light and scan electron microscopic analysis of cyclops syndrome: etiopathogenic hypothesis and technical solutions. Knee Surg Sports Traumatol Arthosc 1996;4:194–199.[CrossRef]
- Dandy DJ, Edwards DJ. Problems in regaining full extension of the knee after anterior cruciate ligament reconstruction: does arthrofibrosis exist? Knee Surg Sports Traumatol Arthroscopy 1994;2:76–79.[CrossRef][Medline]
- Recht MP, Piraino DW, Cohen MA, Parker RD, Bergfeld JA. Localized anterior arthrofibrosis (cyclops lesion) after reconstruction of the anterior cruciate ligament: MR imaging findings. AJR Am J Roentgenol. 1995;165:383–385.[Abstract/Free Full Text]
- Bradley DM, Bergman AG, Dillingham MF. MR imaging of cyclops lesions. AJR Am J Roentgenol. 2000;174:719–726.[Abstract/Free Full Text]
- McCauley TR, Elfar A, Moore A, et al. MR arthrography of anterior cruciate ligament reconstruction grafts. AJR Am J Roentgenol. 2003;181:1217–1223.[Abstract/Free Full Text]
- Nuccion SL, Hame SL. A symptomatic cyclops lesion 4 years after anterior cruciate ligament reconstruction. Arthroscopy 2001;17:E8.[Medline]
- Olson PN, Rud P, Griffiths HJ. Cyclops lesion. Orthopedics 1995;18:1041,1044–1045.[Medline]
- Muellner T, Kdolsky R, Grossschmidt K, Schabus R, Kwasny O, Plenk H Jr. Cyclops and cyclopoid formation after anterior cruciate ligament reconstruction: clinical and histomorphological differences. Knee Surg Sports Traumatol Arthrosc 1999;7:284–289.[CrossRef][Medline]
- Petsche TS, Hutchinson MR. Loss of extension after reconstruction of the anterior cruciate ligament. J Am Acad Orthop Surg 1999;7:119–127.[Abstract]
- McMahon PJ, Dettling JR, Yocum LA, Glousman RE. The cyclops lesion: a cause of diminished knee extension after rupture of the anterior cruciate ligament. Arthroscopy 1999;15:757–761.[Medline]
- Irisawa H, Takahashi M, Hosokawa T, Nagano A. Cyclops syndrome occurring after chronic partial rupture of the anterior cruciate ligament without surgical reconstruction. Knee Surg Sports Traumatol Arthrosc 2007;15:144–146. Epub 2006 Jul 15.[CrossRef][Medline]
- Veselko M, Rotter A, Tonin M. Cyclops syndrome occurring after partial rupture of the anterior cruciate ligament not treated by surgical reconstruction. Arthroscopy 2000;16:328–331.[Medline]
- Tonin M, Saciri V, Veselko M, Rotter A. Progressive loss of knee extension after injury: cyclops syndrome due to a lesion of the anterior cruciate ligament. Am J Sports Medicine 2001;29:545–549.
- Reicher MA, Hartzman S, Bassett LW, Mandelbaum B, Duckwiler G, Gold RH. MR imagiing of the knee. Part I. Traumatic disorders. Radiology 1987;162:547–551.[Abstract/Free Full Text]
- Lee JK, Yao L, Phelps CT, Wirth CR, Czajka J, Lozman J. Anterior cruciate ligament tears: MR imaging compared with arthroscopy and clinical tests. Radiology 1988;166:861–864.[Abstract/Free Full Text]
- Umans H, Wimpfheimer O, Haramati N, Applbaum YH, Adler M, Bosco J. Diagnosis of partial tears of the anterior cruciate ligament of the knee: value of MR imaging. AJR Am J Roentgenol 1995;165:893–897.[Abstract/Free Full Text]
- Roychowdhury S, Fitzgerald SW, Sonin AH, Peduto AJ, Miller FH, Hoff FL. Using MR imaging to diagnose partial tears of the anterior cruciate ligament: value of axial images. AJR Am J Roentgenol 1997;168:1487–1491.[Abstract/Free Full Text]
- Nakagawa T, Hiraoka H, Fukuda A, Matsubara T, Nakayama S, Nakamura K. Symptomatic cyclops lesion after rupture of the anteromedial bundle of the anterior cruciate ligament. J Orthop Sci 2006;11:537–540.[CrossRef][Medline]
- Huang GS, Lee CH, Chan WP, Chen CY, Yu JS, Resnick D. Localized nodular synovitis of the knee: MR imaging appearance and clinical correlates in 21 patients. AJR Am J Roentgenol. 2003;181:539–543.[Abstract/Free Full Text]
- Delince P, Krallis P, Descamps PY, Fabeck L, Hardy D. Different aspects of the cyclops lesion following anterior cruciate ligament reconstruction: a multifactorial etiopathogenesis. Arthroscopy 1998;14:869–876.[Medline]
- Kartus J, Magnusson L, Stener S, Brandsson S, Eriksson BI, Karlsson J. Complications following arthroscopic anterior cruciate ligament reconstruction: a 2–5-year follow-up of 604 patients with special emphasis on anterior knee pain. Knee Surg Sports Traumatol Arthrosc 1999;7:2–8.[CrossRef][Medline]
- Mayr HO, Weig TG, Plitz W. Arthrofibrosis following ACL reconstruction: reasons and outcome. Arch Orthop Trauma Surg 2004;124:518–522. Epub 2004 Aug 3.[CrossRef][Medline]
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Abstract
Introduction
