Deltoid ligament in acute ankle injury: MR imaging analysis

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1 Skeletal Radiol (2014) 43: DOI /s SCIENTIFIC ARTICLE Deltoid ligament in acute ankle injury: MR imaging analysis Min Sun Jeong & Yun Sun Choi & Yun Jung Kim & Jin Su Kim & Ki Won Young & Yoon Young Jung Received: 26 November 2013 /Revised: 23 January 2014 /Accepted: 3 February 2014 /Published online: 6 March 2014 # ISS 2014 Abstract Objective To identify the pattern of deltoid ligament injury after acute ankle injury and the relationship between ankle fracture and deltoid ligament tear by magnetic resonance imaging (MRI). Materials and methods Thirty-six patients (32 male, and 4 female; mean age, 29.8 years) with acute deltoid ligament injury who had undergone MRI participated in this study. The deltoid ligament was classified as having 3 superficial and 2 deep components. An image analysis included the integrity and tear site of the deltoid ligament, and other associated injuries. Association between ankle fracture and deltoid ligament tear was assessed using Fisher s exact test (P<0.05). Results Of the 36 patients, 21 (58.3 %) had tears in the superficial and deep deltoid ligaments, 6 (16.7 %) in the superficial ligaments only, and 4 (11.1 %) in the deep ligaments only. The most common tear site of the three components of the superficial deltoid and deep anterior tibiotalar ligaments was their proximal attachments (94 % and 91.7 % respectively), and that of the deep posterior tibiotalar ligament (pttl) was its distal attachment (82.6 %). The common associated injuries were ankle fracture (63.9 %), syndesmosis tear (55.6 %), and lateral collateral ligament complex tear (44.4 %). All the components of the deltoid ligament were frequently torn in patients with ankle fractures (tibionavicular ligament, P=0.009). Conclusion The observed injury pattern of the deltoid ligament was complex and frequently associated with M. S. Jeong: Y. S. Choi (*) : Y. J. Kim : Y. Y. Jung Department of Radiology, Eulji Hospital, Eulji University, 68, Hangeulbiseok-ro, Nowon-gu, Seoul , Korea mdcys0128@hanmail.net J. S. Kim: K. W. Young Department of Orthopedic Surgery, Eulji Hospital, Eulji University, 68, Hangeulbiseok-ro, Nowon-gu, Seoul , Korea concomitant ankle pathology. The most common tear site of the superficial deltoid ligament was the medial malleolar attachment, whereas that of the deep pttl was near its medial talar insertion. Keywords Ankle. Acute injury. Deltoid. Magnetic resonance imaging Introduction The deltoid ligament is a strong multibanded complex of various components and an important medial stabilizer of the ankle [1 4]. Wide anatomical variations of the deltoid ligament have been reported, but a general consensus considered the deltoid ligament as having superficial and deep components [4 8]. The superficial deltoid layer includes the tibionavicular (TNL), tibiospring (TSL), and tibiocalcaneal ligaments (TCL), which originate from the anterior colliculus of the medial malleolus, cross the ankle and subtalar joints, and insert onto the navicular bone, spring ligament, and sustentaculum tali respectively [1, 4, 6, 9]. The deep deltoid layer includes the anterior and posterior tibiotalar ligaments (attl and pttl respectively), and crosses only the ankle joint [2, 4 6, 9]. The deep attl originates from the tip of the anterior colliculus and anterior part of the intercollicular groove of the medial malleolus, and inserts onto the talar neck. The deep pttl originates from the posterior colliculus and intercollicular groove of the medial malleolus, and inserts onto the medial surface of the talus (Fig. 1) [1]. The deltoid ligament complex has been reported to limit external rotation, abduction, and pronation of the talus, and to act as the main stabilizers of the ankle [2, 4, 5, 10, 11]. Deltoid ligament injuries account for 5 15 % of ankle sprain cases [1, 5]. Single or repeated episodes of ankle sprain

2 656 Skeletal Radiol (2014) 43: cause insufficiency of the deltoid ligament and may lead to instability or impingement syndrome of the ankle [1, 2]. Many clinicians have relied on initial ankle radiographs with medial clear space (MCS) widening and clinical signs such as ecchymosis, swelling, and tenderness to evaluate the integrity of the deltoid ligament [11, 12]. However, deltoid rupture could be easily missed on standard ankle radiographs [13]. In addition, recent studies suggest that these clinical signs are inadequate for complete evaluation of the deltoid ligament integrity [5]. Magnetic resonance imaging (MRI) could be helpful in evaluating deltoid ligament injury, and useful in individual cases in which doubt about joint stability and soft tissue integrity exists [11, 12]. However, only a few previous reports have described MRI features of the deltoid ligament and its associated injuries. To our knowledge, injury pattern analysis of the deltoid ligament on MR images has not been described in acute ankle injury. Therefore, the purpose of this study was to identify the pattern of deltoid ligament injury after acute ankle injury and the relationship between ankle fracture and deltoid ligament tear using MRI. Materials and methods Milwaukee, WI, USA) or 3-T imaging system (Skyra; Siemens Health Care, Erlangen, Germany). The patients were examined in the supine position with a neutral ankle position, using either a linear extremity coil or phased-array foot-and-ankle coil. At 3 T, a sagittal T2-weighted fat suppression image was obtained using the Dixon technique witharepetitiontimeof4,100ms,anechotimeof73ms,a turbo factor of 19, and a slice thickness of 3 mm with no interslice gap. Sagittal, axial, coronal fat suppression, and coronal oblique proton-weighted turbo spin echo (TSE) images were obtained with a repetition time of 3,160 3,500 ms, an effective echo time of ms, a turbo factor of6or7,aslicethicknessof3mmwithnointerslicegap, and a field of view of cm. A matrix was obtained with a number of excitations (NEX) of 1 or 2. A coronal oblique image was scanned perpendicular to the long axis of the navicular bone. An axial fat suppression T2-weighted TSE image was alsoobtainedwitharepetition time of 3,130 ms, an effective echo time of 78 ms, a turbo factor of 11, and a matrix of At 1.5 T, a sagittal inversion recovery image was obtained with a 16-cm field of view, a repetition time of 5,000 ms, an echo time of 16 ms, an inversion time of 150 ms, an echo train length Patients This study was approved by our institutional review board, and informed consent was obtained from all patients. The study population comprised 54 patients who had undergone MRI examination at our institution between November 2009 and February 2013, after experiencing an acute ankle injury (range, 1 7 days; mean duration, 2.7 days). Data inclusion in this study was confined to MRI reports indicating acute deltoid ligament injury from a prospectively collected database. All of 54 patients had severe pain, tenderness, and swelling over their medial ankle, or instability of their medial ankle on the physical examination. We excluded 18 patients who were <15 years of age or had a recurrent sprain or penetrating injury. Finally, 36 patients were enrolled in the study, of whom 32 were male and 4 were female. Their mean age was 29.8 years (range, years). All 36 patients had initial standard ankle radiographs in the anteroposterior, lateral, and mortise views. The clinical and surgical data were reviewed. Sixteen of the 36 patients underwent surgery for deltoid ligament tear: deltoid ligament repair in 8 and reattachment (anchoring) with deltoid ligament repair in 8. Fourteen patients underwent internal fixation of an associated ankle fracture. All MRI findings correlated with surgical findings. MR imaging techniques Magnetic resonance imaging studies were performed using a 1.5-T (Twinspeed; General Electric Health Care, Fig. 1 The medial ankle displaying the superficial and deep layer of the deltoid ligament. The superficial deltoid ligament is shown as semitransparent to expose the covered deep deltoid ligament. The superficial deltoid ligament consists of three components (1, tibionavicular ligament; 2, tibiospring ligament; 3, tibiocalcaneal ligament) and courses from the medial malleolus to the navicular bone, spring ligament, and calcaneus bone. The deep deltoid ligament consists of two components (4, deep anterior tibiotalar ligament; 5, deep posterior tibiotalar ligament). The two arrows indicate the intercollicular groove. a-c anterior colliculus, p-c posterior colliculus, SL superomedial band of spring ligament, Ti tibia, T talus, ST sustentaculum tali, C calcaneus, N navicular

3 Skeletal Radiol (2014) 43: (ETL) of 9, and a slice thickness of 3.5 mm with no interslice gap. Sagittal, axial, coronal fat suppression, and coronal oblique proton-weighted fast spin echo (FSE) images were obtained with a repetition time of 4,000 4,250 ms, an effective echo time of ms, an ETL of 7 9,andaslicethicknessof3mmwithnointerslicegap.A matrix was obtained with a NEX of 1 or 2. An axial fat suppression T2-weighted FSE image was also obtained with a repetition time of 4,000 ms, an effective echo time of 98 ms, an ETL of 13, and a matrix of Image analysis During assessment of the MRI findings, we classified the deltoid ligament component as being in a superficial layer such as the TNL, TSL, and TCL, or in a deep layer such as the attl and pttl (Fig. 1). For the evaluation, we analyzed all the deltoid ligament components using our preferred imaging planes as follows: TNL in coronal and axial images, TSL and TCL in the coronal and coronal oblique planes, and both deep deltoid ligaments in coronal, coronal oblique, and axial images [14]. Non-visibility of the ligament was considered as the congenital absence of the ligament on MR images. We assessed by MRI the integrity and tear site of the deltoid ligaments after acute ankle injury, and the correlation between the deltoid ligament integrity on MRI and MCS widening (>4 mm) on radiographs [5, 6, 13, 15]. Deltoid ligament integrity was classified as grade 0, I, II, or III on the basis of the morphological features and signal alterations of the ligaments. Grade 0 indicated an intact ligament. Grade I was characterized by periligamentous edema; grade II, by a partial tear presenting as laxity, irregular contour, or partial discontinuity with the hyperintensity of the ligament; and grade III, by a complete tear of the ligament. According to the craniocaudal extent, the site of the ligament tear was classified as proximal or medial malleolar, intermediate, or distal or talar injury. We also determined other concomitant pathological conditions, including ankle fractures and injuries to the syndesmosis joint, lateral collateral ligament complex (LCLC), posterior tibial tendon (PTT), and flexor retinaculum. The tear of the LCLC and syndesmosis joint was defined as partial or complete tear depending on the involvement of one component or more than one component of the ligament complex respectively. Finally, we analyzed the relationship between the ankle fracture and deltoid ligament tearing. MCS was measured twice on the ankle mortise view. The radiographic and MRI findings were recorded after consensus between two musculoskeletal radiologists (with 10 years and 2 years of experience in musculoskeletal imaging respectively) who were blinded to the arthroscopic or surgical findings. Statistical analysis The agreement between MCS widening on radiograph and deltoid ligament tearing on MRI was evaluated using the kappa test. The proportions of the deltoid ligament tear in the patients with MCS widening and those without MCS widening were compared using the Chi-squared test. In addition, we used Fisher s exact test to compare the proportion of the deltoid ligament tear between the ankles with fractures and those without fractures. A statistical significance threshold of P=0.05 was used. Statistical analyses were performed using SAS software version 9.3 (SAS Institute, Cary, NC, USA). Results On the MR images, we were able to identify the TNL in 30 (83.3 %), TCL in 35 (97.2 %), deep attl in 33 (91.7 %), and TSL and deep pttl in all (100 %) of the 36 patients. The TNL, TCL, and attl were not visualized on the MR images of 6 (16.7 %), 1 (2.8 %), and 3 (8.3 %) of the 36 patients respectively. There was no soft tissue edema in areas of the fat suppression or inversion recovery images where the ligaments were thought to be absent because of anatomical variation. Integrity of the deltoid ligament The integrity of the superficial and deep components of the deltoid ligament in acute ankle injury is summarized in Table 1. Superficial ligament injuries were more common than deep ligament injuries. Of the 36 patients assessed, 21 (58.3 %) had tears (grade II and III) in the superficial and deep deltoid ligaments (Fig. 2), 4 (11.1 %) had tears in the deep ligaments only (Fig. 3), and 6 (16.7 %) had tears in the superficial Table 1 Integrity of the deltoid ligament in acute ankle injury Components Superficial Deep Grade III 50.0 (15/30) Grade II 13.3 (4/30) Grade I 20.0 (6/30) Grade (5/30) TNL TSL TCL attl pttl 41.7 (15/36) 27.7 (10/36) 13.9 (5/36) 16.7 (6/36) 42.8 (15/35) 22.9 (8/35) 22.9 (8/35) 11.4 (4/35) 21.2 (7/33) 15.2 (5/33) 30.3 (10/33) 33.3 (11/33) 38.9 (14/36) 25.0 (9/36) 11.1 (4/36) 25.0 (9/36) Data are expressed as percentages. The numbers in parentheses were used to calculate the percentages TNLtibionavicular ligament, TSLtibiospring ligament, TCLtibiocalcaneal ligament, attlanterior tibiotalar ligament, pttlposterior tibiotalar ligament

4 658 Skeletal Radiol (2014) 43: ligaments only (Fig. 4). In 15 (41.7 %) of the 36 patients, complete tears (grade III) occurred in all three of the components of the superficial deltoid ligament. Complete tears of the posterior tibiotalar component of the deep deltoid ligament were observed in 14 of the 36 patients (38.9 %). Approximately 78.3 % of the ankles with a pttl tear showed tearing of all the superficial deltoid ligaments. In 84 % of the ankles with a TSL tear, the TNL and TCL were torn. The intraoperative integrity of the deltoid ligament correlated with the MRI findings in 15 of the 16 patients who had undergone surgical treatment of a deltoid ligament injury (93.7 %). Correlation between deltoid ligament integrity and MCS widening Seventeen (47.2 %) of the 36 patients showed widening (>4 mm) of the MCS on the initial ankle mortise radiographs. We observed moderate agreement between MCS widening on radiographs and tears of the superficial and deep deltoid ligaments on MRI (kappa=0.48 to 0.6). Tearing of the superficial and deep deltoid ligaments was more frequently observed in the patients with widened MCS than in those without MCS widening. There were significant intergroup Fig. 2 A 41-year-old man with fractures of the distal fibula and posterior malleolus. a An anteroposterior radiograph of an ankle shows widening of the medial clear space and fracture (arrow) of the distal fibula. b Axial T2-weighted fat-suppressed and c coronal oblique protonweighted TSE MR images show the deep posterior tibiotalar ligament (arrows) fully detached from its medial talar attachment. On d coronal oblique and e sagittal proton-weighted TSE MR images, the tibiocalcaneal (d; arrow), tibiospring (e; long arrow), and tibionavicular ligaments (e; short arrow) are detached from the proximal tibial attachment of the ligaments. The patient underwent surgical repair of the deep and superficial deltoid ligaments, with internal fixation of the distal fibular fracture

5 Skeletal Radiol (2014) 43: Fig. 3 A 44-year-old man with an acute ankle injury. a Coronal oblique proton-weighted TSE MR image shows swelling and partial discontinuity of the deep posterior tibiotalar ligament (arrows). b, c The tibiospring (b; arrow) and tibiocalcaneal ligaments (c; arrow) ofthe superficial deltoid ligament show preserved continuity on coronal proton-weighted fat-suppressed MR images. Bone marrow edema of the medial talus (b; arrowheads) is also noted. The patient underwent conservative treatment differences for all components of the deltoid ligament (p<0.05; Table 2). Localization of deltoid ligament injury The tear (grades II and III) sites of the deltoid ligaments are described in Table 3. The most common tear site of all three components of the superficial deltoid and deep attl was the tibial attachment ( %; Figs. 2, 4), whereas that of the deep pttl was near its medial talar insertion (82.6 %; Fig. 2). Concomitant injuries Isolated deltoid injury was observed in 3 (8.3 %) of the 36 patients, and only the superficial component of the deltoid ligament was involved in these cases. Among the other injuries that occurred along with the deltoid ligament injury, ankle fracture was identified in 23 (63.9 %) of the 36 patients. The injury mechanisms in the ankle fractures, according to the Lauge Hansen classification, were pronation external rotation injury in 10 patients, supination external rotation injury in 8, and pronation abduction injury in 5. There were 10 distal fibular fractures, 6 posterior malleolar fractures, 4 medial malleolar fractures, and 3 fractures of the distal fibula and posterior malleolus. The superficial and deep deltoid ligaments were more frequently torn in the patients with an ankle fracture than in those without an ankle fracture (Table 4). Significant differences in the TNL (p=0.009) and deep attl (p= 0.022) were especially observed between the two groups. However, no significant differences in the deep pttl tears were observed (P >0.999). Twenty patients (55.6 %; Fig. 4) had a syndesmosis tear and all of them had anterior inferior tibiofibular ligament tear. LCLC tear wasobservedin16(44.4%)and11outof16patients had a tear in both the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL). PTT tearing was observed in 6 patients (16.7 %), 5 of whom had a complete tear in the TSL. Ten patients (27.8 %) had a tear of the flexor retinaculum. Discussion According to many investigators, the deltoid ligament components, also known as the medial collateral ligament (MCL) complex, are variably present [1, 3, 9, 16, 17]. In the present study, we categorized the deltoid ligament as having three superficial and two deep components, according to the report by Schneck et al. [9].

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7 Skeletal Radiol (2014) 43: Fig. 4 A 34-year-old man with fractures of the proximal fibular shaft and posterior malleolus. a An ankle mortise radiograph shows widening of the medial and tibiofibular clear spaces. b Axial and c e coronal oblique proton-weighted TSE MR images show a complete tear (arrows) of the superficial deltoid ligament, including all three of the following components: tibionavicular (b; arrow), tibiospring (c; arrow), and tibiocalcaneal ligaments (d; long arrow). A tear in the proximal portion of the deep anterior tibiotalar part (c; clear arrow) is also noted. In addition, edema is present, but tearing of the deep posterior tibiotalar ligament is not in e (arrows). f, g Axial proton-weighted TSE MR images reveal a complete tear (f; arrow) of the anterior inferior tibiofibular ligament. The anterior talofibular ligament (g; arrow) is not torn. The patient underwent surgical repair and reattachment of the superficial deltoid ligament, with syndesmotic screw fixation MRI was highly reliable in evaluating the deltoid ligament integrity of the ankle. Moreover, it was able to demonstrate a detailed anatomy and other concomitant pathological conditions such as injuries to the syndesmosis joint, LCLC, and PTT [2, 5, 18 20]. Our study results showed a high degree of visibility in the deep attl (91.7 %) on MRI. The attl had been seen in 50 % to 84 % of normal asymptomatic ankles in previous reports [1, 16]. We assume that the reason the attl was highly discernible in our study is because we used a coronal oblique imaging plane, which might be helpful for visualizing the oblique course of this ligament, with thinner sections, and a high field-strength MR unit. The other deltoid ligament components were detected at a similar degree of visibility to those described in previous reports [1, 16, 17]. Regarding deltoid ligament integrity, our study results showed a higher rate of acute injury in the superficial deltoid than in the deep deltoid. Moreover, the strongest ligaments were the deep pttl and TSL, whereas the weakest component was the TNL. Our results were in agreement with the findings of anatomical studies, with the incidence of tearing suggesting the following order of decreasing ligament strength: deep pttl, TSL, TCL, and TNL [1, 7, 17]. Our results also suggested that deltoid ligament tearing after acute Table 3 Localization of the deltoid ligament tear (grade II and III injuries) Components Superficial Deep Sites Proximal or avulsion 100 (19/19) 92.0 (23/25) Intermediate (2/25) TNL TSL TCL attl pttl 91.3 (21/23) 8.7 (2/23) Distal or avulsion (1/12) (11/12) (4/23) 82.6 (19/23) Data are expressed as percentages. The numbers in parentheses were used to calculate the percentages injury was common in both the superficial and deep ligaments, whereas some authors have reported that deltoid ligament tearing was more common in the deep ligament than in the superficial ligament [3, 21]. In this study, there was moderate agreement between MCS widening on radiographs and the complete tear of the superficial and deep deltoid ligaments on MRI. However, a previous arthroscopic study reported a significant false-positive rate of 53.6 % for complete tears of the deep PTTL, which is known to be a major contributor to ankle stability, by radiographic widening of the MCS ( 4 mm)[13]. Cheung et al. [17] have reported that MCS widening usually correlates with tears of the anterior inferior tibiofibular ligament and deep pttl. Therefore, additional imaging studies, including MRI, should be recommended for appropriate diagnosis and treatment of ankle injuries. In some previous studies, deltoid ligament injuries have been categorized clinically. Proximal injury (71 %) of the superficial deltoid ligament was the most frequent, followed by distal injury (19 %) [3, 6]. In this study, we found a high incidence of proximal tears of all the superficial components. The most common tear site of the deep attl was different Table 2 Correlation between deltoid ligament integrity on MRI and medial clear space (MCS) widening Components Superficial Deep TNL TSL TCL attl pttl Ctear No Ctear No Ctear No CTear No Ctear No MCS >4 mm mm p value Data are expressed as number of patients C tear means grade III injuries of the deltoid ligament No means intact or grade I injury of the deltoid ligament

8 662 Skeletal Radiol (2014) 43: Table 4 Relationship between deltoid ligament tear and ankle fracture Components Superficial Deep TNL TSL TCL attl pttl Tear No Tear No Tear No Tear No Tear No Fracture (+) ( ) Total p value > Data are expressed as number of patients "Tear" means grade II or III injuries of the deltoid ligament "No" means intact or grade I injury of the deltoid ligament from that of the deep pttl on the craniocaudal extent. These areas in which tears most commonly occurred should be carefully scrutinized on MR images. Isolated deltoid ligament injury is rare, reported only in 3 out of 281 ankle injuries [2, 10]. Up to 10 % of deltoid ligament injuries in the ankles were associated with syndesmosis injuries [21]. In this study, more than half of the patients with a deltoid ligament tear also had a syndesmosis tear. This result could be explained by the shared injury mechanism via the external rotation, ankle dorsiflexion, and foot pronation of the deltoid ligament and syndesmosis joint [5, 10, 22]. Partial or complete tear of the LCLC was present in 44.4 % of the patients, which might be explained by the frequent association of the deep tibiotalar component with inversion and adduction, known injury mechanisms of the LCLC [9, 23, 24]. Acute injuries to the deltoid ligament can also occur in association with ankle fracture [6, 13, 25]. Our study results also revealed that the pronation or supination with the external rotation mechanism led to deltoid ligament injuries in 78.3 % of the patients with an ankle fracture. In our study, the TNL and deep attl were more frequently torn in the patients with an ankle fracture than in those without an ankle fracture. In this study, no significant statistical differences in the deep pttl tearing were found regardless of whether the patient had an ankle fracture or not. However, the frequency of deep pttl tear (65.2 %) was higher than previously expected (20 to 50 % occurrence in ankle fracture) [11]. Therefore, the evaluation of the deep pttl, known as an intra-articular component and a major stabilizer of the mortise, may be important in predicting ankle stability for appropriate treatment of the ankle fracture. The PTT is an important stabilizer of the medial plantar arch, and its dysfunction is often associated with a tibiospring ligament disorder, which contributes to medial ankle instability. We observed 6 cases of PTT tear, 5 of which had a complete tear in the TSL, corresponding to the results of preexisting studies [26, 27]. The treatment of deltoid ligament injuries is controversial and depends on the stability of the ankle [12]. Generally, acute deltoid ligament injury is treated conservatively or is allowed to heal on its own, provided bone stabilization can be obtained [5]. However, surgical management is needed for the patient who has complex ankle fractures with medial soft tissue interposition or instability of the mortise due to complete rupture of the majority in the deltoid ligament [5, 10, 12, 18]. Our study suggested high correlations between MRI and direct surgical or arthroscopic findings. Therefore, MRI allows evaluation of the extensive or complex injury of the deltoid ligament and can be useful in decision-making regarding the appropriate treatment strategies. This study had limitations. First, we included only a small number of patients who had deltoid ligament injuries. Second, an imaging-based selection bias might have existed because the patients who had severe acute ankle injury with ankle fractures tended to undergo MRI. In addition, consensus review by two readers who had a disparity in experience levels might be another limitation. In a future study, a large population should be included and it will be helpful to increase the statistical confidence in the MRI analysis of deltoid ligament integrity. In conclusion, superficial deltoid ligament injury is more frequently observed than deep deltoid ligament injury. The most common tear site of the superficial deltoid is the medial malleolar attachment site, whereas that of the deep pttl is near its medial talar insertion. The observed injury pattern of the deltoid ligament is more complex than we expected and frequently associated with concomitant pathological conditions of the ankle. Conflict of interest interest. The authors declare that they have no conflicts of

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