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Medial Collateral Ligament Complex of the Ankle: MR Appearance in Asymptomatic Subjects¹

¹ From the Departments of Radiology (B.M., M.Z., J.H., C.W.A.P.) and Orthopedic Surgery (P.V.), Orthopedic University Hospital Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland. Received January 11, 2006; revision requested March 9; revision received April 17; accepted May 17; final version accepted June 28. Address correspondence to B.M. (e-mail: mengiardi{at}yahoo.de).

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 
Purpose: To prospectively characterize the spin-echo magnetic resonance (MR) imaging appearance of the medial collateral ligament (MCL) complex of the ankle in asymptomatic volunteers.

Materials and Methods: The study was approved by institutional review board. Informed consent was obtained. MR images in 56 asymptomatic subjects (29 women, 27 men; mean age, 40.7 years; range, 23–60 years) were analyzed by two musculoskeletal radiologists. Visibility and signal intensity characteristics were analyzed for deep (anterior and posterior tibiotalar ligaments [TTLs]) and superficial (tibionavicular ligament [TNL], tibiospring ligament [TSL], and tibiocalcaneal ligament [TCL]) components of the MCL complex. Thickness of ligaments was compared between sexes (Mann-Whitney U test). Associations between age and variables of signal intensity characteristics and morphology were evaluated with Kruskal-Wallis test.

Results: Anterior and posterior TTLs, TNL, TSL, and TCL were visible in 31 (55%), 56 (100%), 31 (55%), 56 (100%), and 49 (88%) subjects, respectively. On T1-weighted images, anterior and posterior TTLs, TNL, TSL, and TCL were more commonly of intermediate signal intensity than hypointense (77%, 100%, 93%, 50%, and 73% of subjects, respectively); on T2-weighted images, they were commonly hypointense (55%, 52%, 42%, 75%, and 78% of subjects, respectively). On T2-weighted images, posterior TTL had a striated appearance that was significantly associated with age (P = .004) in 89% of subjects: In subjects younger than 45 years, this striated appearance was present. On T1-weighted images, striation was present in 48% of subjects. Striation was uncommon in remaining ligaments. Mean thickness and range were 1.5 mm and 1–4 mm (anterior TTL), 8.2 mm and 6–11 mm (posterior TTL), 1.6 mm and 1–2 mm (TNL), 2.0 mm and 1–4 mm (TSL), and 1.2 mm and 1–3 mm (TCL). TNL (P = .001) and TSL (P = .003) were significantly thicker in men than in women.

Conclusion: In asymptomatic volunteers, posterior TTL and TSL were always visible, but anterior TTL and TNL are only seen in approximately half of subjects. Posterior TTL has a typically striated appearance.

© RSNA, 2007

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 
The medial collateral ligament (MCL) of the ankle—also called deltoid ligament—is a strong ligamentous complex with various components (1–7). Although descriptions vary widely, there is general agreement that the MCL consists of a deep layer that courses from the medial malleolus to the talus and of a delta-shaped superficial layer that courses from the medial malleolus to the navicular, the spring ligament, and the calcaneus. The MCL complex is an important stabilizer not only against valgus forces but also against anterior and lateral talar excursion, as well as rotatory forces (8). Insufficiency of the MCL may lead to osteoarthritis of the ankle joint (5,8). In addition, the interlacing of the tibiospring ligament (TSL), the tibionavicular ligament (TNL), and the spring ligament complex supports the talar head and stabilizes the talocalcaneonavicular joint. A relationship between the laxity of this ligament complex and medial ankle instability has been suggested (9).

Ankle ligament injuries are among the most common injuries in sports and recreational activities (10). Eighty-five percent of ankle injuries are inversion injuries (11), which are typically associated with lesions of the lateral collateral ligaments. Several studies have shown that magnetic resonance (MR) imaging is capable of depicting injuries of the lateral collateral ligaments (12–14). The effect of findings at MR imaging on therapy, however, is moderate because most acute sprains of the ankle are initially treated conservatively (15). Imaging of injuries of the MCL complex is relevant because these injuries may lead to chronic pain and instability if they are not surgically treated (16–18). Furthermore, in displaced lateral malleolar fractures with a tear of the deep MCL, surgical reduction is indicated to restore the ankle mortise (19,20).

Injuries of the MCL complex account for approximately 15% of ligamentous ankle trauma (21) and are usually associated with injuries of the lateral collateral ligaments (16) and the tibiofibular syndesmosis, as well as malleolar fractures (22). Isolated lesions of the MCL complex are rare (18).

There are only a few investigations about MR imaging of the MCL complex (12,23–25). These investigations were performed in either cadaveric feet (23) or a small number of asymptomatic subjects. Furthermore, imaging was performed by using low-field-strength MR units (12,24) and T2*-weighted three-dimensional gradient-echo sequences (25). To our knowledge, the MR appearance of the MCL complex on images obtained with more commonly used spin-echo sequences has not been described in asymptomatic individuals. Thus, the purpose of our study was to prospectively characterize the spin-echo MR appearance of the MCL complex of the ankle in asymptomatic volunteers.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 
Volunteers
Fifty-six asymptomatic volunteers (29 women, 27 men; mean age, 40.7 years; range, 23–60 years) were prospectively included in the study. For each decade of age between 20 and 60 years, at least six women and six men were included. Criteria for inclusion were that the volunteer (a) had not undergone prior foot and/or ankle surgery, (b) had no foot and/or ankle pain, (c) had never seen a physician for foot and/or ankle complaints, (d) had no injury of the foot or ankle during the last 2 years, and (e) had no systemic inflammatory disease. The study was approved by the institutional review board. Informed consent was obtained from each volunteer.

MR Imaging Protocol
MR imaging was performed with a 1.5-T system (Symphony; Siemens Medical Solutions, Erlangen, Germany). Subjects were examined in the supine position with one ankle placed in a neutral position in a dedicated circularly polarized send-receive extremity coil. T1-weighted spin-echo images were obtained in the coronal plane (repetition time msec/echo time msec, 572/14; section thickness, 3.5 mm; field of view, 96 x 170 mm; acquisition time, 3 minutes 22 seconds); in the transverse oblique plane, which was 45° between the coronal and transverse planes (572/14; section thickness, 4 mm; field of view, 113 x 150 mm; acquisition time, 3 minutes 43 seconds); and in the sagittal plane (330/14; section thickness, 3 mm; field of view, 190 x 190 mm; acquisition time, 1 minute 55 seconds). T2-weighted fast spin-echo images were obtained in the coronal plane (4130/86; section thickness, 3.5 mm; field of view, 104 x 170 mm; acquisition time, 3 minutes 51 seconds) and in the transverse plane (3900/85; section thickness, 4 mm; field of view, 124 x 180 mm; acquisition time, 2 minutes 43 seconds). A fast spin-echo short inversion time inversion-recovery sequence (repetition time msec/echo time msec/inversion time msec, 4000/89/170; section thickness, 3 mm; field of view, 190 x 190 mm; acquisition time, 3 minutes 38 seconds) was performed in the sagittal plane.

Analysis of MR Images
Definition of components.—The anterior and posterior tibiotalar ligaments (TTLs) from the deep layer—as well as the TNL, TSL, and tibiocalcaneal ligament (TCL) from the superficial layer—were qualitatively and quantitatively evaluated (Fig 1). These components were defined on the basis of their attachments according to data in studies by Sarrafian (1) and Milner and Soames (2,3): The anterior TTL originates from the tip of the anterior colliculus and the anterior part of the intercollicular groove of the medial malleolus (Fig 1) and inserts on the medial surface of the talus just distal to the anterior part of the medial talar articular surface. The posterior TTL originates from the upper segment of the posterior surface of the anterior colliculus, from the intercollicular groove, and of the anterior surface of the posterior colliculus of the medial malleolus. The fibers insert onto the medial surface of the talus under the tail of the articular facet, as far as the posteromedial talar tubercle. The TNL originates from the anterior border of the anterior colliculus of the medial malleolus and inserts onto the dorsomedial aspect of the navicular. Some fibers may extend onto the superomedial part of the spring ligament. The TSL originates from the anterior segment of the anterior colliculus of the medial malleolus. Its fibers insert on the superior border of the superomedial part of the spring ligament complex. The TCL originates from the medial aspect of the anterior colliculus of the medial malleolus, descends vertically, and inserts on the medial border of the sustentaculum tali.

View larger version (48K): [in this window] [in a new window] [Download PPT slide]   Figure 1: Left: Drawing of the medial aspect of the ankle displays the deep and superficial layer of the MCL complex. The superficial layer is semitransparently displayed to visualize the covered portions of the deep layer. Deep layer consists of anterior and posterior TTLs. Superficial layer consists of TNL, TSL (covers the anterior TTL of the deep layer), and TCL (covers the anterior portions of the posterior TTL of the deep layer). Three portions of the spring ligament complex are displayed: superomedial calcaneonavicular ligament (smCNL), medioplantar oblique calcaneonavicular ligament (1), and inferoplantar longitudinal calcaneonavicular ligament (2). Intercollicular groove (arrowheads) is shown. aColl = anterior colliculus, pColl = posterior colliculus. Right: Drawing shows location of the coronal planes of the MR images in Figures 2–5.

Quantitative evaluation.—The thickness of the ligaments was measured by a fellowship-trained musculoskeletal radiologist (B.M.) by using a picture archiving and communication system workstation (Cerner Image Devices, Idstein, Germany) and was obtained to the nearest 0.1 of a millimeter and then rounded to the nearest millimeter. All measurements were performed at the middle of each ligament.

Statistical Analysis
The thicknesses of all the evaluated ligaments obtained in men and women were compared by using the Mann-Whitney U test (two tailed). Because the comparison involved five ligaments in each subject, the inflated type I error was adjusted with Bonferroni correction: A difference with P < .01 was considered statistically significant. To analyze associations between age and the variables of signal intensity characteristics and morphology, the Kruskal-Wallis test was used. A difference with P < .05 was considered statistically significant. For statistical analyses, software (SPSS for Windows, version 10.0.1, 1999; SPSS, Chicago, Ill) was used.

	RESULTS

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Qualitative Evaluation
The components of the MCL complex in asymptomatic subjects were evaluated on MR images (Table 1). The anterior TTL was visible in 31 (55%) subjects and was best seen on coronal images (100%) (Fig 2). The signal intensity was usually intermediate on T1-weighted images (77%) and less commonly low on T2-weighted images (55%). A significant association was observed between age and signal intensity pattern on T1-weighted images (P = .006): An inhomogeneous pattern of the anterior TTL on T1-weighted images was seen in 21% (four of 19) of the volunteers younger than 45 years and in 67% (eight of 12) of the volunteers older than 45 years. In regard to morphology, the anterior TTL most commonly had a uniform thickness (74%) with well-delineated borders (68%).

View larger version (30K): [in this window] [in a new window] [Download PPT slide]   Figure 2a: Anterior TTL (anterior portion of the deep layer of the MCL complex) and TSL (middle portion of the superficial layer of the MCL complex) in asymptomatic 25-year-old man. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The TSL (thick black arrow) originates from the anterior segment of the anterior colliculus and inserts on the superomedial calcaneonavicular ligament (thin black arrows), a portion of the spring ligament complex. The anterior TTL (white arrow) is situated underneath the TSL, originates from the tip of the anterior colliculus and the anterior part of the intercollicular groove, and inserts on the medial surface of the talus just distal to the anterior part of the medial talar articular surface. Between the superomedial calcaneonavicular ligament and the distal portion of the posterior tibial tendon (PTT), a gliding zone (curved arrow) for the tendon that contains some fibrocartilage lined by a single layer of synovial cells is present (26). Flexor retinaculum (open arrow), flexor digitorum longus tendon (FDL), and flexor hallucis longus tendon (FHL) are observed. For location of the imaging plane see Figure 1, right.

View larger version (183K): [in this window] [in a new window] [Download PPT slide]   Figure 2b: Anterior TTL (anterior portion of the deep layer of the MCL complex) and TSL (middle portion of the superficial layer of the MCL complex) in asymptomatic 25-year-old man. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The TSL (thick black arrow) originates from the anterior segment of the anterior colliculus and inserts on the superomedial calcaneonavicular ligament (thin black arrows), a portion of the spring ligament complex. The anterior TTL (white arrow) is situated underneath the TSL, originates from the tip of the anterior colliculus and the anterior part of the intercollicular groove, and inserts on the medial surface of the talus just distal to the anterior part of the medial talar articular surface. Between the superomedial calcaneonavicular ligament and the distal portion of the posterior tibial tendon (PTT), a gliding zone (curved arrow) for the tendon that contains some fibrocartilage lined by a single layer of synovial cells is present (26). Flexor retinaculum (open arrow), flexor digitorum longus tendon (FDL), and flexor hallucis longus tendon (FHL) are observed. For location of the imaging plane see Figure 1, right.

View larger version (176K): [in this window] [in a new window] [Download PPT slide]   Figure 2c: Anterior TTL (anterior portion of the deep layer of the MCL complex) and TSL (middle portion of the superficial layer of the MCL complex) in asymptomatic 25-year-old man. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The TSL (thick black arrow) originates from the anterior segment of the anterior colliculus and inserts on the superomedial calcaneonavicular ligament (thin black arrows), a portion of the spring ligament complex. The anterior TTL (white arrow) is situated underneath the TSL, originates from the tip of the anterior colliculus and the anterior part of the intercollicular groove, and inserts on the medial surface of the talus just distal to the anterior part of the medial talar articular surface. Between the superomedial calcaneonavicular ligament and the distal portion of the posterior tibial tendon (PTT), a gliding zone (curved arrow) for the tendon that contains some fibrocartilage lined by a single layer of synovial cells is present (26). Flexor retinaculum (open arrow), flexor digitorum longus tendon (FDL), and flexor hallucis longus tendon (FHL) are observed. For location of the imaging plane see Figure 1, right.

View larger version (32K): [in this window] [in a new window] [Download PPT slide]   Figure 3a: Posterior TTL (posterior portion of the deep layer of the MCL complex) in asymptomatic 28-year-old woman. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The posterior TTL (arrows) originates from the upper segment of the posterior surface of the anterior colliculus, the intercollicular groove, and the anterior surface of the posterior colliculus. The fibers insert onto the medial surface of the talus. A typical striated appearance is seen on both T1- and T2-weighted images. Keys are the same as in Figure 2a. For location of the imaging plane, see Figure 1, right.

View larger version (176K): [in this window] [in a new window] [Download PPT slide]   Figure 3b: Posterior TTL (posterior portion of the deep layer of the MCL complex) in asymptomatic 28-year-old woman. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The posterior TTL (arrows) originates from the upper segment of the posterior surface of the anterior colliculus, the intercollicular groove, and the anterior surface of the posterior colliculus. The fibers insert onto the medial surface of the talus. A typical striated appearance is seen on both T1- and T2-weighted images. Keys are the same as in Figure 2a. For location of the imaging plane, see Figure 1, right.

View larger version (174K): [in this window] [in a new window] [Download PPT slide]   Figure 3c: Posterior TTL (posterior portion of the deep layer of the MCL complex) in asymptomatic 28-year-old woman. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The posterior TTL (arrows) originates from the upper segment of the posterior surface of the anterior colliculus, the intercollicular groove, and the anterior surface of the posterior colliculus. The fibers insert onto the medial surface of the talus. A typical striated appearance is seen on both T1- and T2-weighted images. Keys are the same as in Figure 2a. For location of the imaging plane, see Figure 1, right.

View larger version (23K): [in this window] [in a new window] [Download PPT slide]   Figure 4a: TNL (anterior portion of the superficial layer of the MCL complex) in asymptomatic 48-year-old woman. (a) Corresponding drawing of (b–d) sequential T1-weighted coronal MR images (572/14) from posterior to anterior. The TNL (open arrow) originates from the anterior border of the anterior colliculus and inserts onto the dorsomedial surface of the navicular (Nav) in d. On the most posterior plane in b, the most anterior portions of the TSL (thick arrow) in continuity with the TNL and the superomedial calcaneonavicular ligament (thin arrows) (portion of the spring ligament complex) are seen. Gliding layer between the posterior tibialis tendon (PTT) and the superomedial calcaneonavicular ligament (curved arrow) is observed. Main portion of the posterior tibialis tendon and plantar portion of the same tendon (pl PTT) after division are shown in a. For location of the imaging plane, see Figure 1, right.

View larger version (157K): [in this window] [in a new window] [Download PPT slide]   Figure 4b: TNL (anterior portion of the superficial layer of the MCL complex) in asymptomatic 48-year-old woman. (a) Corresponding drawing of (b–d) sequential T1-weighted coronal MR images (572/14) from posterior to anterior. The TNL (open arrow) originates from the anterior border of the anterior colliculus and inserts onto the dorsomedial surface of the navicular (Nav) in d. On the most posterior plane in b, the most anterior portions of the TSL (thick arrow) in continuity with the TNL and the superomedial calcaneonavicular ligament (thin arrows) (portion of the spring ligament complex) are seen. Gliding layer between the posterior tibialis tendon (PTT) and the superomedial calcaneonavicular ligament (curved arrow) is observed. Main portion of the posterior tibialis tendon and plantar portion of the same tendon (pl PTT) after division are shown in a. For location of the imaging plane, see Figure 1, right.

View larger version (72K): [in this window] [in a new window] [Download PPT slide]   Figure 4c: TNL (anterior portion of the superficial layer of the MCL complex) in asymptomatic 48-year-old woman. (a) Corresponding drawing of (b–d) sequential T1-weighted coronal MR images (572/14) from posterior to anterior. The TNL (open arrow) originates from the anterior border of the anterior colliculus and inserts onto the dorsomedial surface of the navicular (Nav) in d. On the most posterior plane in b, the most anterior portions of the TSL (thick arrow) in continuity with the TNL and the superomedial calcaneonavicular ligament (thin arrows) (portion of the spring ligament complex) are seen. Gliding layer between the posterior tibialis tendon (PTT) and the superomedial calcaneonavicular ligament (curved arrow) is observed. Main portion of the posterior tibialis tendon and plantar portion of the same tendon (pl PTT) after division are shown in a. For location of the imaging plane, see Figure 1, right.

View larger version (72K): [in this window] [in a new window] [Download PPT slide]   Figure 4d: TNL (anterior portion of the superficial layer of the MCL complex) in asymptomatic 48-year-old woman. (a) Corresponding drawing of (b–d) sequential T1-weighted coronal MR images (572/14) from posterior to anterior. The TNL (open arrow) originates from the anterior border of the anterior colliculus and inserts onto the dorsomedial surface of the navicular (Nav) in d. On the most posterior plane in b, the most anterior portions of the TSL (thick arrow) in continuity with the TNL and the superomedial calcaneonavicular ligament (thin arrows) (portion of the spring ligament complex) are seen. Gliding layer between the posterior tibialis tendon (PTT) and the superomedial calcaneonavicular ligament (curved arrow) is observed. Main portion of the posterior tibialis tendon and plantar portion of the same tendon (pl PTT) after division are shown in a. For location of the imaging plane, see Figure 1, right.

The TCL was visible in 49 (88%) subjects and was always best seen on coronal images (Fig 5). On T1-weighted images, the signal intensity was typically intermediate (73%), with a homogeneous signal intensity pattern (71%). On T2-weighted images, the signal intensity of the TCL was low (78%), with a homogeneous signal intensity pattern (78%). The TCL had either a uniform thickness (53%) or demonstrated broadening at the distal insertion (45%). The ligament most commonly had well-delineated borders (76%).

View larger version (28K): [in this window] [in a new window] [Download PPT slide]   Figure 5a: TCL (posterior portion of the superficial layer of the MCL complex) in asymptomatic 25-year-old man. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The TCL (arrowheads) originates from the medial aspect of the anterior colliculus and inserts onto the medial border of the sustentaculum tali. Flexor retinaculum (open arrow) and posteromedial border of the posterior TTL (white arrow) are seen. Keys are the same as in Figure 2a. For location of the imaging plane, see Figure 1, right.

View larger version (159K): [in this window] [in a new window] [Download PPT slide]   Figure 5b: TCL (posterior portion of the superficial layer of the MCL complex) in asymptomatic 25-year-old man. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The TCL (arrowheads) originates from the medial aspect of the anterior colliculus and inserts onto the medial border of the sustentaculum tali. Flexor retinaculum (open arrow) and posteromedial border of the posterior TTL (white arrow) are seen. Keys are the same as in Figure 2a. For location of the imaging plane, see Figure 1, right.

View larger version (164K): [in this window] [in a new window] [Download PPT slide]   Figure 5c: TCL (posterior portion of the superficial layer of the MCL complex) in asymptomatic 25-year-old man. (a) Corresponding drawing. (b) T1-weighted coronal MR image (572/14). (c) T2-weighted coronal MR image (4130/86). The TCL (arrowheads) originates from the medial aspect of the anterior colliculus and inserts onto the medial border of the sustentaculum tali. Flexor retinaculum (open arrow) and posteromedial border of the posterior TTL (white arrow) are seen. Keys are the same as in Figure 2a. For location of the imaging plane, see Figure 1, right.

	DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

In our study, the posterior TTL and the TSL were the only two ligaments that were visible in all volunteers, whereas the TCL was seen in 88% of the ankles and the anterior TTL and TNL were seen in 55% of the ankles. This is not fundamentally different from the results presented by Boss and Hintermann (4) that were based on 12 human cadaveric feet; these investigators observed the anterior TTL in 50% of the specimens, and they observed the posterior TTL, TSL, and TCL in all specimens. In their study, however, the TCL could not clearly be distinguished from the deep TTL in two of 12 specimens. Instead of a TNL, they described a reinforcing fibrous capsular layer. In contrast, other investigators described the TNL (1,3) as a constantly seen structure. We assume that the limited visibility of the TNL in our study is at least in part explained by the oblique course of this ligament. It has been suggested that the ankle be examined in 40°–50° plantar flexion or that transverse oblique imaging (23,24) or three-dimensional gradient-echo sequences with reformation (25) be performed to visualize this ligament. The low visibility of the anterior TTL (55% of ankles) in our study reflects the known anatomic variability of this ligament, which is in some cases hardly discernible and in other cases completely absent (7,23).

The anterior TTL, the TNL, and the TSL in patients older than 45 years had variable signal intensity on T2-weighted images; this finding means that the assessment of signal intensity is not a good indicator for diagnosis of ligamentous abnormalities. In contrast, the TSL (88%) and the TCL (78%) in patients younger than 45 years typically were hypointense on T2-weighted images. In our population, the posterior TTL had a striated appearance in all subjects younger than 45 years and in 89% of the entire study population. This is in accordance with anatomic descriptions of striations with interlaced fatty tissue (1,3). The absence of this striation in young patients is a possible sign of a posterior TTL abnormality. This concept is supported by findings in an orthopedic study about posteromedial impingement caused by posterior TTL injury. In that study, all 12 posterior TTLs with surgically proved degeneration had loss of normal striation on MR images (18).

As shown by other investigators (1,3–6), the posterior TTL is the thickest and strongest ligament of the MCL complex. In our study, the measured thickness (mean, 8.2 mm; range, 6–11 mm) corresponded well to measurements in the range of 5–15 mm in the textbook by Sarrafian (1). For the TSL and TCL, there are contradictory descriptions of thickness in the literature. Although some investigators (1,4,7) describe the TCL to be the strongest ligament—with a mean and range of thickness of 1.8 mm (4) and 2–3 mm, respectively (1)—of the superficial layer, others describe the TCL as not always existing (2,3) or as very weak (6). In our study, the TSL was the thickest ligament (mean thickness, 2.0 mm) of the superficial layer, whereas the TCL was the thinnest portion with a mean thickness of 1.2 mm. We were unable to find any comparison between thickness of ligaments and sex in the anatomic literature. In our study, the posterior TTL, TSL, and TNL were significantly thicker in men than they were in women.

In medial ankle instability, the most commonly injured ligaments are the TNL and TSL, either with a proximal tear or avulsion (79%) or a distal tear (19%) close to the spring ligament (16,26). In displaced lateral malleolar fractures with a tear of the deep MCL, surgical reduction is indicated to restore the ankle mortise (19,20). Widening of the medial tibiotalar joint space on the mortise view has been shown to be unreliable in the diagnosis of a posterior TTL tear (22). As shown in our study, these most commonly injured anatomic structures can be well depicted with a standard ankle MR examination. To display the entire course of the TNL in an oblique transverse plane, secondary image reformation or an MR examination with a foot in plantar flexion may be considered. The value of MR imaging to reliably detect lesions of the MCL complex, however, still has to be evaluated in a surgically controlled population.

Theoretically, it is still possible that investigated asymptomatic volunteers have lesions of the MCL complex that are at the moment not symptomatic. According to our criteria for inclusion for the asymptomatic study population, however, we are confident that we excluded subjects with any relevant acute or chronic lesion of the MCL complex, as well as any postoperative changes.

In conclusion, in asymptomatic volunteers, the posterior TTL and the TSL are always visible on MR images of the ankle. The TCL usually is visible, but the anterior TTL and TNL ligaments, which are seen in approximately half of the subjects, are not. The posterior TTL has a typically striated appearance, notably in subjects younger than 45 years.

	ADVANCES IN KNOWLEDGE

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 

• In asymptomatic volunteers, the posterior tibiotalar ligament (TTL) and the tibiospring ligament are always visible on MR images of the ankle.
  
• The tibiocalcaneal ligament is usually visible, but not the anterior TTL and tibionavicular ligament, which are seen in approximately half of subjects.
  
• The posterior TTL has a typically striated appearance, notably in subjects younger than 45 years.
  

	FOOTNOTES

 

Abbreviations: MCL = medical collateral ligament • TCL = tibiocalcaneal ligament • TNL = tibionavicular ligament • TSL = tibiospring ligament • TTL = tibiotalar ligament

Authors stated no financial relationship to disclose.

Author contributions: Guarantors of integrity of entire study, B.M., M.Z.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, B.M., P.V.; clinical studies, B.M., P.V., J.H., M.Z.; statistical analysis, B.M., C.W.A.P., J.H., M.Z.; and manuscript editing, all authors

	References

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION ADVANCES IN KNOWLEDGE References

 

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