Surg Radiol Anat (2006) 28: 142–149 DOI 10.1007/s00276-006-0077-0

O R I GI N A L A R T IC L E

Nabil A. Ebraheim Æ Figen Taser Æ Qaiser Shafiq Richard A. Yeasting

Anatomical evaluation and clinical importance of the tibiofibular syndesmosis ligaments

Received: 18 July 2005 / Accepted: 21 October 2005 / Published online: 7 February 2006
Springer-Verlag 2006

Abstract The aim of this study was to describe the detailed anatomical arrangement of ligaments of the tibiofibular syndesmosis and to highlight the clinical aspects of fracture dislocations. This study was performed on 42 legs of adult human embalmed cadavers. Tibiofibular syndesmosis ligaments attachments and their mutual relationships were described and their dimensions were measured. The anterior tibiofibular ligament is usually composed of three parts. This ligament runs obliquely at laterodistaly direction making 35 angle with horizontal plane and posteriorly 65 angle with sagittal plane. The posterior tibiofibular ligament runs almost horizontally 20 angle with horizontal plane. The mean thicknesses of tibial and fibular attachments are 6.38±1.91 mm and 9.67±1.74 mm, respectively. The inferior transverse ligament originates from just below the posterior tibiofibular ligament, which has variations on the shape and dimensions due to its attachment points. The average length is 36.60±9.51 mm. The network between the fibular notch and the distal fibula has been filled with the interosseous tibiofibular ligament whose fibers follow the laterodistal and anterior direction from the tibia to the fibula. It lies proximally 30–40 mm from the mortise. At the inferior view of the tibiofibular syndesmosis a pyramidal shaped cartilaginous facet was observed which was attached to the fibula. The length of this cartilage was variable. Some of synovial plicas from the ankle joints

N. A. Ebraheim Æ F. Taser (&) Æ Q. Shafiq Department of Orthopaedic Surgery, Medical University of Ohio, 3065 Arlington Avenue, Toledo, OH 43614, USA E-mail: fi[email protected] Tel.: +1-419-3836206 Fax: +1-419-3832809 R. A. Yeasting Department of Neuroscience and Anatomy, Medical University of Ohio, 3065 Arlington Avenue, Toledo, OH 43614, USA

synovial membrane were observed at this view. We conclude that the results of this study may be useful to both orthopedic surgeons and radiologists for anatomic evaluation of the tibiofibular syndesmosis area. Keywords Tibiofibular syndesmosis Æ Distal tibiofibular joint Æ Anatomy Æ Ankle Æ Ligaments

Introduction The distal tibiofibular joint which is named usually as tibiofibular syndesmosis, is between the rough medial convex surface of the distal fibula and the triangular fibular notch of the lateral surface of the distal tibia. This complex forms a mortise for the trochlea of the talus [3, 13, 23, 33, 36]. This is a fibrous joint that the rough opposed surfaces of the bones are united by a strong interosseous ligament. In addition, the joint is strengthened in the front and in the behind by longer bands called the anterior and posterior tibiofibular ligaments. Under the cover of the posterior tibiofibular ligament there is a longer band, called the inferior transverse ligament or transverse tibiofibular ligament [3, 5, 29, 36]. The syndesmotic ligament complex maintains the integrity between the distal tibia and the fibula, and resists the axial, rotational, and translational forces that attempt to separate these two bones [28, 33, 34, 36]. Eighty-five percent of ankle injuries are sprains, and 85% of those are lateral inversion sprains [2, 11]. Most ankle sprains occur on the lateral aspect of the ankle. They are also the most commonly seen sports injury, comprising 14–21% of sports injuries [20, 27]. Athletes participating in basketball, volleyball, soccer, and football are at especially high risk for ankle sprains, comprising 25–45% of injuries in these sports [27]. The bony and soft tissue anatomy of the ankle place the lateral side of the ankle at higher risk than the medial side. The distal end of the fibula (i.e., the lateral malleolus) extends further inferiorly than the distal end of the

143

tibia (i.e., the medial malleolus). This discrepancy in length gives the medial ankle superior stability by improving bony resistance to eversion [39, 40]. Considerable knowledge of anatomy is required to understand the fracture mechanism and to restore the stability of ankle mortise after fracture dislocations. However, there is lack of the detailed knowledge of this important part of the ankle joint in the anatomical literature. The aim of this study was to describe the detailed anatomical arrangement and relationship of ligaments of the tibiofibular syndesmosis and to highlight the clinical aspects of fracture dislocations in this area.

Materials and methods This study was performed on 42 ankles of 22 adult human embalmed cadavers which had normal appearance and no macroscopic and radiographic evidence of previous trauma or degenerative changes. Investigations were carried out on both ankles in 20 and on single ankles in 2 (1 right, 1 left) because the contralateral ankles were not suitable for the study. The cadavers were constituted from 9 male and 13 female, age range at the time of death, 74–96 years; mean age, 85 years. All specimens were examined with radiography to exclude those with apparent arthritic changes and previous injuries. The first step involved a basic dissection of the all ankle ligaments, using a 2.5 · surgical loupe for magnification. Distal tibiofibular joint ligaments insertion points are determined and described with detail. And then, the dimensions of ligaments were measured by Mitutoyo Caliper (accuracy value 0.01 mm), and their size and mutual relationships were recorded. Goniometer was used for angular measurements. The measurements were repeated three times by the same investigator, and the average values were recorded. The length, width and thickness measurements were taken of proximal, middle and distal parts of the anterior tibiofibular ligament. The posterior tibiofibular ligament’s width, proximal and distal edges length and tibial and fibular insertion thicknesses were measured. Also the angles between these ligaments and their angles with horizontal and the sagittal planes were measured using a goniometer. The length, width and thickness of the inferior transverse ligament were measured. After the anterior and posterior tibiofibular ligaments were cut, the following dimensions of the interosseous ligament were taken: The length of the fibers at the proximal and distal ends, the width of ligament at tibial and fibular insertions, thickness at the distal edge, distance between origin of ligament and beginning of articular surface of the ankle joint. The cartilage thickness was taken by measuring the distance between two ends of the cartilage on inferior view of ankle syndesmosis using calipers (Fig. 5) Statistical analysis was done with the SPSS 11.0 software.

Results Anterior tibiofibular ligament The anterior tibiofibular ligament inserts on the anterior tubercle of the distal tibia and attaches to the anterior surface of the fibula at the lateral malleolus. The ligament has a trapezoid shape because its tibial insertion is wider than the fibular attachment. This ligament runs obliquely in the laterodistal direction with approximately 35 angle with the horizontal plane and approximately 65 angle with the sagittal plane (Table 1). The anterior tibiofibular ligament is usually composed of three parts with some exceptions as four parts. These sections are generally separated by fibrofatty tissue gaps but in few cases they look continuous (Fig. 1a, 1b, 1c). The mean length of the upper part is 8.89±2.90 mm, while the mean width and thickness are 4.92±1.21 mm and 1.76±0.26 mm, respectively. The middle part is the widest and the most anterior protruding part because it originates at the anterior tubercle of the tibia and attaches to the top of the anterior tubercle of the fibula. The mean length of this part is 15.46±4.22 mm, the width 8.28±2.20 mm and the thickness 2.62±0.53 mm. The lower part has a length 20.57±5.36 mm, width 3.76±0.52 mm and thickness 2.15±0.70 mm and so it is the longest part of the anterior tibiofibular ligament (Table 2). The lower margin of this part crosses the lateral corner of the talocrural joint and at some positions it touches the lateral ridge of the trochlea of the talus. The anterior talofibular ligament originates just below the fibular insertion of the anterior tibiofibular ligament. Posterior tibiofibular ligament The posterior tibiofibular ligament inserts to the posterior edge of the fibular notch of the distal tibia and attaches to the rough malleolar fossa behind the triangular articular facet of the lateral malleolus of the fibula. It has almost continuous transition with the interosseous tibiofibular ligament which is situated at its upper neighborhood. Some fibers from the fibular insertion sometimes appear to be continuous with the inferior transverse ligament. Therefore it is sometimes difficult to recognize its upper and lower margins between the close related ligaments (Fig. 2a, b). Table 1 Angular measurements of the anterior and posterior tibiofibular ligaments

Horizontal plane Sagittal plane

ATFL

PTFL

35±5 65±7

20±5 85±7

ATFL Anterior tibiofibular ligament, PTFL Posterior tibiofibular ligament

144 Table 2 Dimensions of the proximal, middle and distal parts of the anterior tibiofibular ligament (mm)

Length Width Thickness

Proximal Part

Middle Part

Distal Part

8.89±2.90 4.92±1.21 1.76±0.26

15.46±4.22 8.28±2.20 2.62±0.53

20.57±5.36 3.76±0.52 2.15±0.70

The posterior tibiofibular ligament is quite compact and strong ligament. This ligament runs almost horizontally approximately at 20 angle with the horizontal plane (Table 1). The mean length of the upper margin of the ligament is approximately 9.71±6.91 mm, while the lower margin is 21.83±7.52 mm long. The mean width of the ligament is 17.44±3.54 mm. The mean thickness of the tibial insertion is 8.27±0.95 mm, and the fibular attachment is 11.30±0.49 mm (Table 3). A strong inferior margin of the posterior tibiofibular ligament fills the angle between the posterior ridge of the tibia and the lateral malleolus and contacts with the oblique facet on the trochlea of the talus.

Fig. 1 a, b Anterolateral view of the left tibiofibular syndesmosis. a. A tripartite form of the anterior tibiofibular ligament. Arrows indicate the three parts of the anterior tibiofibular ligament. b. Arrow indicates the compact unipartite anterior tibiofibular ligament. (Ti Tibia, F Fibula, Ta Talus). c Anterolateral view of the right tibiofibular syndesmosis shows anterior tibiofibular ligament. Arrows indicate the four parts of the anterior tibiofibular ligament. Arrowheads indicate the fibers covering the interosseous ligament on anterior surface, which are in reverse direction. Asteriks indicates the crural fascia

Fig. 2 a, b The posterior view of the two different specimens of ankle joint. Posterior tibiofibular ligament (1), inferior transverse ligament (2), posterior talofibular ligament (3). Arrows indicate attachment points of the inferior transverse ligament

145 Table 3 Dimensions of the posterior tibiofibular ligament (mm)

Proximal length Distal length Mean width Tibial insertion thickness Fibular insertion thickness

Mean±SD

Range

9.71±6.91 21.83±7.52 17.44±3.54 6.38±1.91 9.67±1.74

3.35–21.20 6.40–32.50 11.10–21.45 4.40–8.95 8.00–11.40

the posterior border of the tibial articular surface. The mean length is 36.60±9.51 mm, mean width 4.20± 0.74 mm, and thickness 2.12±0.67 mm (Table 4). Interosseous tibiofibular ligament

The inferior transverse ligament originates from the lateral malleolar fossa just below the posterior tibiofibular ligament. It has variations in the shape and dimensions due to its attachment points. It attaches generally to the postero-inferior corner of the fibular notch on the distal tibia, but in some cases it reaches the medial malleolar fossa (Fig. 2a, b). The inferior transverse ligament appears to be a labrumlike extension of

The network between the fibular notch of the tibia and the medial aspect of the distal fibula is filled by the interosseous tibiofibular ligament. The fibers of the interosseous tibiofibular ligament generally follow the laterodistal and anterior direction from the tibia to the fibula. There are some fibers that follow the reverse direction on the anterior aspect of the interosseous ligament (Fig. 1c). It is observed that the fibers of interosseous ligament are longer than the network when both the anterior and posterior tibiofibular ligaments are cut and the joint space is separated to show clearly the interosseous ligament (Fig. 3). These fibers are folded to situate in this narrow space. The most distal fibers attach to the tibia at the anterior tubercle level, descend straight to the fibula and attach to the fibula just above the talocrural joint level (Fig. 4). Thus pyramidal shape space is found between the tibia, interosseous ligament and base of the tibiofibular contact area. This space generally is filled by the synovial plica from joint capsule of the ankle joint.

Fig. 3 Anterior aspect of the tibiofibular syndesmosis shows the network of the interosseous tibiofibular ligament. Anterior and posterior tibiofibular ligaments were cut and tibia and fibula were separated to show the interosseous tibiofibular ligament. Arrows indicate the upper and lower margins of the interosseous ligament. (F Fibula, Ti Tibia)

Fig. 4 Schematic diagram of the fibular and tibial attachments of the interosseous ligament. The most distal fibers attach to the tibia at the anterior tubercle level on the fibular notch (a), descend and attach the fibula just above the talocrural joint level (0). The most proximal fibers attach to the tibia at the top point of the fibular notch (b)

Table 4 Dimensions of the inferior transverse ligament (mm)

Length Width Thickness

Mean ± SD

Range

36.60±9.51 4.20±0.74 2.12±0.67

25.65–42.85 3.75–4.40 1.65–2.60

The inferior transverse ligament

146 Table 5 Dimensions of the interosseous ligament (mm)

Proximal length Distal length Fibular attachment width Tibial attachment width Thickness

Mean ± SD

Range

6.64±1.28 10.39±3.05 21.22±1.73 17.72±1.02 4.75±1.05

5.75–7.55 8.23–12.55 20.00–22.45 17.05–18.45 3.80–5.25

The interosseous ligament distal fibers insertion level on the tibia is on average 8.10±3.35 mm (range between 5.15–14.30 mm) proximal to the mortise and at the same level with the anterior tubercle of the tibia. The most proximal fibers attach to the tibia at the top of the fibular notch. This level is mean 32.43±4.11 mm (range between 22.35–43.70 mm) proximal to the mortise (Fig. 4). The mean width of the fibular attachment of the interosseous tibiofibular ligament is wider than the tibial attachment, their lengths are 21.22±1.73 mm and 17.72±1.02 mm, respectively. The length of the distal fibers of this ligament is longer than the proximal fibers. The mean length of the most proximal fibers is 6.64±1.28 mm and their length increases gradually to the distal direction. At the most distal point the mean length of the fibers is 10.39±3.05 mm. There are several connective tissue gaps between these fibers. The thickness of the interosseous ligament is 4.75±1.05 mm (Table 5). Inferior aspect of the tibiofibular contact area Inferior view of the tibiofibular contact zone is clearly shown after the medial and lateral ligaments of the ankle are cut and crural bones are separated from the talus and foot. The small triangular shape fibrous connective tissue strip is situated just behind the anterior tibiofibular ligament. Its length is approximately 4.5 mm.

Fig. 5 Inferior aspect of the tibiofibular joint. (a) Indicates measurement of thickness of pyramidal shaped cartilaginous facet. (b) indicates thickness of the posterior tibiofibular ligament

Both contact facets of the bones are covered with thin articular cartilage (less than 0.5 mm) and they are in direct contact with approximately one-half to one-third of the length of total joint line. In the posterior part, a pyramidal shaped cartilaginous facet is attached to the fibula. The length of this cartilage is variable and varies from one-half to two-third of the total length of the joint line (mean length 15.27±5.05 mm). Its thickness is also variable, varies between 1 mm and 5 mm (Fig. 5). At the corresponding tibial side, the thickness of the articular cartilage is very thin (approximately 0.5 mm). Some of synovial plicas from the ankle joints synovial membrane are observed inside the talocrural joint space. They are situated either at the lateral or medial side of the ankle mortise. At the lateral side synovial plica adheres to the fibula and is situated on the abovementioned cartilaginous facet on the fibula. The medial aspect of this plica lies loosely between the tibia and fibula thus forming an interosseous diverticulum of the tibiofibular syndesmosis joint (Fig. 6).

Discussion Anatomical evaluation of tibiofibular syndesmosis The anatomy of tibiofibular syndesmosis is of excessive importance when exploring the integrity and stability of the ankle joint. Ankle instability is commonly present in patients with chronic ankle sprains, which often includes disruption of ligaments of the tibiofibular syndesmosis. The ligaments of the tibiofibular syndesmosis must be described morphologically before the relationship between the disruption of these structures and ankle instability can be determined.

Fig. 6 Inferior aspect of the tibiofibular contact area. There is a small triangular shape fibrous connective tissue (1) just behind the anterior tibiofibular ligament (a). Direct contact area of both bones is indicated by number 2. A pyramidal shaped cartilaginous facet is attached to the fibula (3). Some of synovial plicas from the ankle joints synovial membrane were observed inside the talocrural joint space (*). Anterior tibiofibular ligament (a), posterior tibiofibular ligament (P), tibia (T), fibula (F)

147

Bartonicek [3] in a cadaveric study presented dimensional information of ligaments of the tibiofibular syndesmosis that are similar to our results with some exceptions. Our and Bartonicek’s results regarding anterior tibiofibular ligament dimensions are similar. Their results showed the thickness of posterior tibiofibular ligament as 6 mm while we measured it 6.38 mm and 9.67 mm at the tibial and fibular insertion points, respectively. According to Bartonicek’s study the inferior transverse ligament was considered a part of the posterior tibiofibular ligament. But our observations showed that it is the separate ligament. Although both ligaments insertion points to the fibula were very close, the inferior transverse ligament’s attachment point to the tibia was more variable. Also between these two ligaments there was a fibro-fatty connective tissue mass. Sabacinski et al. [30] observed that there was an attachment of the synovial fold to the posterior deep transverse ligament (inferior transverse ligament) along its entire length. Akseki et al. [1] found the distal fascicle of the anterior tibiofibular ligament in 83% cadavers as compared to our results where it was present in 90% of the cases. They concluded that presence of the fascicle and its contact with the talus was normal finding, but it may become pathological and cause impingement syndrome due to anatomical variations or instability of the ankle. We observed that distal part of this ligament was crossed to the lateral corner of the talocrural joint and in some cases it touched the lateral ridge of the trochlea of the talus due to the position of the ankle and the angle of ligaments with the horizontal plane. This ligament courses obliquely in the laterodistal direction with on average 35 angle (range 30–42) to the horizontal plane. In cases of larger angle, the possibility of the impingement increases. Sarrafian [31] described the interosseous ligament as formed by a dense mass of short fibers which cover the underlying synovial recess. The ligament originates at the anteroinferior triangular segment of the medial aspect of the distal fibular shaft and inserts on the corresponding area located on the lateral surface of the distal tibia. Our findings show that the most distal fibers attach to the tibia at the anterior tubercle level, descend straight to the fibula and attach the fibula just above the talocrural joint level. The most proximal fibers attach to the tibia at the top of the fibular notch. Also we found that the fibers of the interosseous tibiofibular ligament generally follow the laterodistal and anterior direction from the tibia to the fibula with more vertical angle than the anterior tibiofibular ligament. This oblique direction of the ligament fibers allows proximal and distal translation of the fibula. Monk [22] found a variable attachment of the interosseous ligament that ranged between 2 and 6 cm above the ankle. Our results showed that interosseous tibiofibular ligament distal attachments were situated average 8.10±3.35 mm (range between 5.15–14.30 mm) proximal to the mortise and this ligament lies between tibia and

fibula by 30–40 mm proximal to the joint line. The mean width of the fibular attachment was 21.22±1.73 mm and the tibial attachment was 17.72±1.02 mm. Bartonicek [3] reported that in three-fourth of cases of cadaveric study the connection of the distal tibia and fibula is not mere syndesmosis but also a synovial joint. In these cases direct contact between two bones was found and contact facets which were covered with articular cartilage were located in the anterior half of the tibiofibular contact line. In one-quarter of cases where there was no direct contact between the two bones the synovial plica extended anteriorly to the anterior tibiofibular ligament. Clinical importance of ankle syndesmosis ligaments According to Danis–Weber classification of ankle fractures, type B which indicates partial instability of the syndesmosis is the fracture of the fibula at the level of the syndesmosis. Type C is the fracture of the fibula above the level of the syndesmosis. It is interesting to note that it causes complete instability of the syndesmosis regardless of its location which is above the syndesmosis [33]. Pankovich [24, 25] detailed the pathologic anatomy of 90 low distal fibula fractures and reported that 7% had diastasis. He found that supination eversion (external rotation) fibula fractures that begin near the anterior tubercle of the tibia and typically propagate below the interosseous ligament did not injure that ligament. According to Scurran [33], in this type of fractures foot is supinated at the time of injury when it is on ground. The internal rotation of the leg produces a relative external rotation of the talus out of the ankle joint. Since the foot is supinated, the injury pattern propagates from lateral (near the anterior tubercle of the tibia) to medial direction and below the interosseous ligament and in majority of cases does not injure interosseous ligament. Tibiofibular diastasis without associated fibular fracture has been documented in the literature [4, 9, 14, 38]. These isolated injuries of the tibiofibular syndesmosis are frequently overlooked or misdiagnosed. Their incidence lies between 1–11% in acute ankle sprains. Even when treated surgically, the greatest problem is the correct fixation of the fibula in the incisura fibularis [34, 35]. Furthermore incomplete injuries of the syndesmosis tibiofibularis require a longer recovery period than other types of ankle sprains [4, 14, 38]. The partial diastasis of the tibiofibular syndesmosis is often overlooked cause of functional instability. If these ruptures are left undiagnosed or there is insufficient treatment chronic ankle instability, pain, and arthritic changes may occur [4, 18, 30, 34]. The lateral malleolus has importance role in maintaining a congruent ankle joint [12]. Ramsey and Hamilton [26] demonstrated that the tibiotalar contact area changes with tibiofibular diastasis. Their study has shown that even 1 mm of lateral displacement decreases the contact area by 42%. Thus this widening leads to an increase in tibiotalar

148

contact stresses and ultimately early arthrosis of the tibiotalar joint. In our previous studies, it has been shown that shallow incisura fibularis might lead to the instability of the distal tibiofibular syndesmosis [7, 8]. It was detected that the incisura fibularis was shallow in seven patients who had a Type B Weber fibular fracture with syndesmosis disruption [7]. The anterior tibiofibular ligament, of all the tibiofibular syndesmotic ligaments, is best positioned to resist external rotation. It was approximately 2 cm wide and situated 1.25 cm above and 0.75 cm below the edge of the ankle. This ligament is the most commonly ruptured ligament in ankle fractures [33, 34]. Snedden and Shea [34] determined that the posterior tibiofibular ligament was the least important ligament for fibular stability. However, this ligament is very important to inhibit internal rotation forces. But rupture of the distal tibiofibular structures frequently occurs only in external rotation trauma. Our findings showed that the posterior tibiofibular ligament is quite compact and strong ligament. Especially when its thickness was compared, we observed that it was the thickest ligament of all the tibiofibular syndesmotic ligaments. In spite of its thickness it may not be vital for stability due to its position and function, but additional biomechanical studies are required to establish its importance [34]. According to Snedden and Shea [34], the intact deltoid ligament prevents lateral shift of the talus but not diastasis of the fibula and tibia. The lateral collateral ligaments that connect the fibula to the talus and calcaneus prevent talar tilt, but have no effect on diastasis. They emphasized that the interosseous ligament with variable anatomical structure must be torn for diastasis to occur. But they defined ‘‘diastasis’’ as a complete separation. Most of the interosseous ligaments that attach above the course of a low fibula fracture are not disrupted. The variable attachment in 6% cases at the joint line is the anatomic basis for the infrequent diastasis in the low distal fibula fracture [34]. The presence of synovial folds (plicae) in ankle syndesmosis and other foot joints has been documented previously by several authors [3, 6, 7, 10, 15, 16, 17, 19, 21, 29, 30]. According to the descriptions of anatomy textbooks [29, 36], a synovial fold extends into the syndesmotic recess. In Gray’s Anatomy [36], the synovial membrane of the ankle joint was described as a lining in the fibrous capsule which extends for a short distance, approximately 0.4 cm by an upward projection between the tibia and fibula. Sabacinski et al. [30] defined the synovial fold as the synovium-lined capsular tissue visible within the ankle joint at the interspace between the inferior lateral aspect of the tibia and the inferior medial aspect of the fibula. They found the synovial fold in the syndesmotic area in 97% of the specimens. The average size of the fold is 1.4 cm in the anterior to posterior dimension while 0.4 cm in medial to lateral dimension. The upward extension of the recess was found on average 0.5 cm in

length, which is similar to our findings. According to this study, they concluded that both the gross and histologic observations may indicate that this fold functions like meniscus and is needed for stability and proper ankle function. Histological structure of synovial fold is composed of loose connective tissue with nerve fibrils, several synovial cell layers and vascular tissue [3, 10, 15, 17, 19, 29, 30]. Because these folds contain synovial cells and vascular tissue, damage to them can result in considerable pain [16, 19, 29]. The primary complexity of visualization of the ankle ligaments with MR imaging is the difficulty of the threedimensional orientation of each ligament and the extent of its bone attachments. Knowledge of the spatial anatomy of each ligament is required to find a proper foot position and imaging plane that will optimize fulllength visualization of the ligament. Axial images obtained within a centimeter of the tibial plafond provided the best visualization of anterior and posterior tibiofibular ligaments. The inferior transverse ligament is best imaged in full length in the axial plane, although its labrumlike character is best appreciated in sagittal images [32, 37]. In our study the angular measurements of the ligaments were taken. The angle between the anterior tibiofibular ligament and horizontal plane is 35±5 while with sagittal plane 65±7. The posterior tibiofibular ligament lies 20±5 and 85±7 with horizontal and sagittal planes, respectively.

Conclusion We have presented important anatomical data that highlights the strengths and vulnerabilities of various ankle ligaments. Clinical correlation and functions of major ankle ligaments that provide stability to tibiofibular syndesmosis has been described as well. We conclude that the results of this study may be useful for anatomic evaluation of the tibiofibular syndesmosis area to both orthopedic surgeons and radiologists.

References 1. Akseki D, Pinar H, Yaldiz K et al (2002) The anterior inferior tibiofibular ligament and talar impingement: A cadaveric study. Knee Surg Sports Tr Ar 10:321–326 2. Balduini FC, Tetzlaff J (1983) Historical perspectives on injuries of the ligaments of the ankle. Clin Sports Med 1220(1):3–12 3. Bartonicek J (2003) Anatomy of the tibiofibular syndesmosis and its clinical relevance. Surg Radiol Anat 25:379–386 4. Boytim MJ, Fischer DA, Neumann L (1991) Syndesmotic ankle sprains. Am J Sports Med 19(3):294–298 5. Bozic KJ, Jaramillo D, DiCanzio J et al (1999) Radiographic appearance of the normal distal tibiofibular syndesmosis in children. J Pediatr Orthop 19(1):14–21 6. Doskocil M (1988) The distal connection of the tibia and fibula is not just a syndesmosis. Sb Lek 90(1):1–7 7. Ebraheim NA, Elgafy H, Panadilam T (2003) Syndesmotic disruption in low fibular fractures associated with deltoid ligament injury. Clin Orthop Related Res 409:260–267

149 8. Ebraheim NA, Lu J, Yang H et al (1998) The fibular incisure of the tibia on CT scan: a cadaver study. Foot ankle 19(5):318–321 9. Edwards GS Jr, DeLee JC (1984) Ankle diastasis without fracture. Foot Ankle 4(6):305–312 10. Fick R (1904) Hanbuch de Anatomie und Mechanik der Gelenke unter berucksichtigung der bewegenden Muskeln. Part 1: Anatomie der Gelenke. Fischer, Jena, pp 440–421 11. Garrick JG (1982) Epidemiologic perspective. Clin Sports Med 1(1):13–8 12. Harper MC (1983) An anatomic study of the short oblique fracture of the distal fibula and ankle stability. Foot Ankle 4(1):23–29 13. Harper MC, Keller TS (1989) A radiographic evaluation of the tibiofibular syndesmosis. Foot Ankle 10(3):156–160 14. Hopkinson WJ, St Pierre P, Ryan JB et al (1990) Syndesmosis sprains of the ankle. Foot Ankle 10(6):325–330 15. Johnston TB, Davis DV, Davis F (eds) (1958) Gray’s anatomy, 32nd edn. Longmans Green, London, pp 530–536 16. Kelikian H, Kelikian AS (1952) Disorders of the ankle. Saunders, Philadelphia, pp 1–91 17. Kos J (1957) CevnT zasobenT pouzdra hlezenneho kloubu. (Blood supply of the articular capsule of the ankle.). Cs Morf 5:80–93 18. Leeds HC, Ehrlich MG (1984) Instability of the distal tibiofibular syndesmosis after bimalleolar and trimalleolar ankle fractures. J Bone Joint Surg 66-A(4):490–503 19. Lidtke RH, George J (2004) Anatomy, biomechanics, and surgical approach to synovial folds within the joints of the foot. J Am Podiatr Med Assoc 94(6):519–527 20. Liu SH, Nguyen TM (1999) Ankle sprains and other soft tissue injuries. Curr Opin Rheumatol 11(2):132–137 21. Lutz W (1942) Zur Struktur der unteren Tibiofibularverbindung und der membrane interossea cruris. Anat Entwickl Gesch 111:315–321 22. Monk CJE (1969) Injuries of the tibiofibular ligaments. J Bone Joint Surg 51B:330–337 23. Oae K, Takao M, Naito K et al (2003) Injury of the tibiofibular syndesmosis: Value of MR imaging for diagnosis. Radiology 227:155–161 24. Pankovich AM (1978) Fractures of the fibula proximal to the distal tibiofibular syndesmosis. J Bone and Joint Surg 60-A(2):221–229 25. Pankovich AM (1979) Fractures of the fibula at the distal tibiofibular syndesmosis. Clin Orthop Relat Res 143:138–147

26. Ramsey PL, Hamilton W (1976) Changes in tibiotalar area of contact caused by lateral talar shift. J Bone Joint Surg 58A:356–357 27. Renstrom PAFH, Kannus P (1994) Injuries to the foot and ankle. Orthop Sports Med pp 1705–1767 28. Rockwood CA, Green DP, Bucholz RW et al (1976) Fractures in Adults. Fourth Edition, vol 2. Lippincott & Raven 1976 Chapter 31 pp 2206 29. Romanes GJ (1972) Cunningham’s textbook of anatomy, 11th edn. Oxford University Press, London, pp 247–249 30. Sabacinski KA, Walter JH, Saffo G (1990) Anatomical and histologic investigation of the syndesmotic area in the ankle joint. J Am Pod Med Assoc 80(4):204–210 31. Sarrafian S (1983) Anatomy of the foot and ankle. Lippincott, Philadelphia 32. Schneck CD, Mesgarzadeh M, Bonakdarpour A et al (1992) MR imaging of the most commonly injured ankle ligaments I. Normal anatomy. Radiology 184:499–506 33. Scurran BL (1990) Foot and Ankle Trauma. Chapter 28, Ankle Fractures by Gumann G. Churchill Livingstone, New York, pp 579–625 34. Snedden MH, Shea JP (2001) Diastasis with low distal fibula fractures: An anatomic rationale. Clin Orthop Relat Res 382:197–205 35. Sora MC, Strobl B, Staykov D et al (2004) Evaluation of the ankle syndesmosis: A plastination slices study. Clin Anat 17:518–517 36. Standring S, Editor; Gray’s Anatomy (2005) Williams A, Davies MS. Chapter 115, Ankle and Foot. 39th edn. Churchill Livingstone, London, pp 1525 37. Stoller DW (1998) MRI, arthroscopy, and surgical anatomy of the joints. Raven Publishers, New York 38. Taylor DC, Englehardt DL, Bassett FH 3rd (1992) Syndesmosis sprains of the ankle. The influence of heterotopic ossification. Am J Sports Med 20(2):146–150 39. Yablon IG, Heller FG, Shouse L (1973) The key role of the lateral malleolus in displaced fractures of the ankle. J Bone Joint Surg 59A:165 40. Yablon IG, Segal D, Leach RE (1983) Ankle injuries. Churchill Livingstone, New York