Musculoskeletal Imaging
Original Research
Tibialis Anterior Tendon and Extensor Retinaculum: Imaging in Cadavers and Patients with Tendon Tear
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OBJECTIVE. Under the hypothesis that the anatomic relationship of the tibialis anterior tendon and extensor retinaculum of the foot and ankle is relevant to the clinical aspects of a tear in that tendon, we assessed the anatomic details of these structures using MRI in cadavers and evaluated MRI in patients with a tibialis anterior tendon tear.
MATERIALS AND METHODS. Seven cadaveric feet underwent detailed MRI using standard and oblique coronal planes with respect to the course of the tibialis anterior tendon and extensor retinaculum. Cadaveric sections subsequently provided an anatomic correlation. MR images of seven patients with tibialis anterior tendon tear were analyzed by consensus of two musculoskeletal radiologists.
RESULTS. Imaging-anatomic correlations allowed identification of the tibialis anterior tendon and extensor retinaculum. The tendon passed through three tunnels formed by the superior extensor retinaculum, oblique superomedial, and oblique inferomedial limbs of the inferior extensor retinaculum. Of seven patients with the tendon tear, three patients had complete tears and four patients had partial tears. In all partial tears, the level of the tear was at the ankle joint, corresponding to the approximate level of the oblique superomedial limb. In all complete tears, the proximal ends of torn tendons were retracted to a level below the oblique superomedial limb. In all tears, the oblique superomedial limb surrounding the torn tendon was seen with thickening in four patients and enhancement after IV gadolinium injection in two patients. Other findings included a bulbous appearance or swelling of the torn tendon in two complete and two partial tears and fluid collections within the tendon sheath and in an area confined by the extensor retinaculum in four patients.
CONCLUSION. The relationship of the tibialis anterior tendon and extensor retinaculum is well depicted on MRI, even in patients with a tibialis anterior tendon tear, and is clinically relevant to the tear of this tendon.
Keywords: anatomy, ankle, foot, MRI, sports medicine, tendons
| Introduction |   |
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Injuries of the ankle are among those most commonly encountered in sports-related and routine activities. This coupled with the fact that the anatomy of the ankle is quite complex requires a detailed understanding of the anatomy and common injuries around this articulation. The ankle joint is a composite joint reinforced by various ligaments. More than 10 tendons and many nerves and vessels cross the ankle and are held in place by several retinacula.
The tibialis anterior tendon is the strongest of the anterior tendons. It is covered by the extensor retinaculum, which stabilizes the tendons in the frontal aspect of the ankle and foot [1]. Its injury in the distal leg or at the level of the ankle is infrequent [2]. Often the diagnosis can be confusing and is delayed. The injury may be overlooked by the patient, and the clinical presentation of a tender bulbous mass at the level of the ankle joint without awareness of any definite functional impairment may cause concern for a neoplasm [3, 4]. In such instances, MRI can help to establish an accurate and prompt diagnosis. It confers the added advantage of evaluation of the anatomic relationship of the tibialis anterior tendon with the surrounding structures. Sonography is known to be a second imaging method for assessment of the injured tendon because of its cost-effectiveness and easy accessibility, as shown by a previous investigation [5].
To our knowledge, about 50 ruptures of the tibialis anterior tendon have been reported [6]; however, little attention has been given to the extensor retinaculum and its influence on the causation and the clinical presentation of such a rupture.
 View larger version (20K) | Fig. 1A —Extensor retinaculum and extensor tendons of foot and ankle. Schematic drawing of frontal aspect of foot and ankle shows components of extensor retinaculum and main extensor tendons. Superior and inferior extensor retinacula cover anterior aspect of ankle and foot, bracing extensor tendons. |
 View larger version (183K) | Fig. 1B —Extensor retinaculum and extensor tendons of foot and ankle. Photograph of dissected cadaveric ankle and foot shows Y-shaped inferior extensor retinaculum and extensor tendons in anterior aspect. Tibialis anterior tendon (arrowheads) is most medially located and passes though tunnels formed by oblique superomedial limb (short arrows) and oblique inferomedial limb (long arrows) of inferior extensor retinaculum. |
 View larger version (131K) | Fig. 2A —Tibialis anterior tendon and superior extensor retinaculum in cadaveric ankle. Transverse T1-weighted MR image (TR/TE, 600/24) obtained at level of musculotendinous junction of extensor tendons (A) and transverse anatomic section (B) show superior extensor retinaculum (arrows) covering extensor tendons, including tibialis anterior tendon (A), which is visualized as linear structure of low signal intensity in A. |
 View larger version (104K) | Fig. 2B —Tibialis anterior tendon and superior extensor retinaculum in cadaveric ankle. Transverse T1-weighted MR image (TR/TE, 600/24) obtained at level of musculotendinous junction of extensor tendons (A) and transverse anatomic section (B) show superior extensor retinaculum (arrows) covering extensor tendons, including tibialis anterior tendon (A), which is visualized as linear structure of low signal intensity in A. |
On the basis of the hypothesis that the anatomic relationship of the tibialis anterior tendon and the extensor retinaculum is relevant to the clinical aspects of tendon rupture, we performed this study with two purposes: first, to show the imaging anatomy of the normal relationship of the tibialis anterior tendon and the extensor retinaculum of the foot and ankle using MRI and, second, to evaluate MRI findings in patients with a tibialis anterior tendon tear.
| Materials and Methods | |
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The tibialis anterior tendon is the most medially located tendon in the ankle and foot. This tendon begins at about the level of the junction between the lower and middle thirds of the tibia and courses toward the medial border of the foot, inserting vertically on the first metatarsal base and the first cuneiform bone. In its course, the tendon is tightly and serially held against the front of the ankle and foot by three retention tunnels formed by the superior extensor retinaculum and the superomedial and inferomedial limbs of the inferior extensor retinaculum [1, 2].
The extensor retinaculum covers the anterior aspect of the ankle and foot. It is the reinforced superficial crural aponeurosis of the leg and composed of both superior and inferior components. The superior extensor retinaculum braces the tendons in the distal leg and the ankle. The inferior extensor retinaculum, which is Y-shaped, forms three compartments for tendons and their synovial sheaths: first, the tibialis anterior tendon lies most medially in both arms of the Y; second, the extensor hallucis longus tendon is located in both arms of the Y; and, third, the extensor digitorum longus tendon and peroneus tertius tendon lie in the medial part of the stem [1, 2, 7] (Figs. 1A and 1B).
The superior extensor retinaculum is a transverse aponeurotic band in the distal leg. Its lateral attachment sites include the lateral crest of the lower fibula and the lateral surface of the lateral malleolus. Medially, it attaches to the anterior crest of the tibia and the medial malleolus. It is in continuity with the superior peroneal retinaculum laterally and with the flexor retinaculum medially. The extensor tendons pass beneath this retinaculum; however, in 25% of cases, there is a separate tunnel for the tibialis anterior tendon formed by superficial and deep layers of the superior extensor retinaculum [1].
The inferior extensor retinaculum is a complex Y- or X-shaped structure located in the anterior aspect of the foot and ankle comprising four components: the stem or frondiform ligament, the oblique superomedial limb, the oblique inferomedial limb, and the oblique superolateral limb. The stem is a sling ligament retaining the tendons of the extensor digitorum longus and peroneus tertius muscles against the talus and the calcaneus. Medially it bifurcates into the oblique superomedial and inferomedial limbs. Laterally it has three roots originating in the tarsal sinus and canal: lateral, intermediary, and medial [1].
The oblique superomedial limb continues from the stem and inserts in the anterior aspect of the medial malleolus. This limb passes over the extensor hallucis longus tendon, and medially, at the level of the tibialis anterior tendon, it bifurcates into superior and inferior tunnels. The superior tunnel has a thick deep wall and a thin or even absent superficial wall. The inferior tunnel is well formed, with insertional fibers reaching the medial malleolus [1].
The oblique inferomedial limb arises from the lateral apex of the sling, advances inferomedially, and reaches the medial border of the foot at the level of the cuneonavicular joint. At the level of the tibialis anterior tendon, most of the fibers pass superficial to the tendon and the remaining fibers slide under the tendon, forming a tunnel. The oblique superolateral limb is present in 25% of cases, which gives an X-shape to the inferior extensor retinaculum [1].
Seven fresh cadaveric foot specimens sectioned across the distal portions of the tibia and fibula more than 5 cm above the ankle joint were obtained from six nonembalmed cadavers (two women, four men; age range at death, 72-86 years; mean age at death, 82.8 years). The specimens were immediately deep-frozen at -40°C (Bio-Freezer, Forma Scientific). All specimens were allowed to thaw for 24 hours at room temperature before imaging.
MRI was performed on a 1.5-T unit (Signa, GE Healthcare) using a dedicated extremity coil. The foot was placed in the supine position with 90° flexion at the ankle. Initially, axial, coronal, and sagittal T1-weighted MR images were acquired from about 4-5 cm proximal to the ankle joint to the metatarsal base with the following parameters: TR/TE, 600/24; 3-mm section thickness with 1-mm interslice gap; field of view, 10-12 cm; number of excitations (NEX), 2; and 512 × 256 matrix. Considering the study by Khoury et al. [8], oblique coronal imaging planes with 2-mm section thickness and 0.1-mm interslice gap were acquired approximately 45° between the coronal and axial planes, perpendicular to the posterior facet of the subtalar joints, and also at an acute angle of about 10° off the coronal plane of the foot toward the lateral malleolus. This plane was obtained only at the level of the tarsal sinus for visualization of the oblique superomedial limb and stem of the inferior extensor retinaculum with regard to its orientation and attachments to the tibia and tarsal sinus.
After imaging, the specimens were refrozen at -40°C for more than 72 hours and sectioned with a band saw into 2- to 3-mm sections in planes corresponding to those of the MR images. The plane of anatomic section in each specimen corresponded to one of the imaging planes according to lines drawn on the specimen at the time of imaging and included the axial, coronal, and oblique coronal. One of the specimens was dissected by an experienced anatomist to reveal the gross anatomy of the extensor retinaculum and tibialis anterior tendon.
All anatomic sections were reviewed and correlated with MR images. MR images of the ankle and foot were evaluated to characterize the normal appearance of the extensor retinaculum and the tibialis anterior tendon with respect to course, their relationship, and their signal intensity. In addition, the best plane of visualization of each of the components of the extensor retinaculum was noted.
MR images of the foot or ankle obtained in seven patients (six men, one woman; age range, 21-74 years; mean age, 52.8 years) with a clinical and imaging diagnosis of a spontaneous tibialis anterior tendon tear were reviewed retrospectively, after approval from the investigational review board at our institution had been obtained. The tear in one patient was confirmed surgically. Because the patients were seen in consultation from different institutions, the imaging protocols varied and included T1- and T2-weighted sequences with or without fat saturation in the axial, sagittal, and coronal planes. The imaging parameters used were TR range/TE range, 450-633/12-15 for T1; 1,800-7,500/90-103 for T2; field of view, 14-18 cm; 3- to 5-mm section thickness with 1.0- to 1.5-mm interslice gap; NEX, 1-3; and matrix, 128-256 × 256. In three of seven patients, T1-weighted fat-saturated sequences obtained after the IV administration of a contrast agent (gadopentetate dimeglumine [Magnevist, Schering]) were available.
Two musculoskeletal radiologists reviewed the images by consensus. The type of tear (complete or partial) and its level, the presence or absence of tendon retraction, the appearance of the torn tendon, any abnormalities of the extensor retinaculum covering the torn tendon, and other ancillary findings such as abnormal fluid collections were recorded.
| Results | |
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In all seven cadaveric specimens, MRI revealed three tunnels covering the tibialis anterior tendon, formed by three limbs of the extensor retinaculum, and the course of each limb.
The superior extensor retinaculum was seen as a low-signal-intensity band on axial images at the level of the musculotendinous junction of the extensor tendons. Under this, the tibialis anterior tendon passed (Figs. 2A and 2B).
The oblique superomedial limb of the inferior extensor retinaculum, seen as a low-signal-intensity band, was visualized optimally on oblique coronal MR images obtained through the tarsal sinus, although it was seen in both the axial and oblique coronal planes. From the stem, the oblique superomedial limb extended superomedially, attaching to the anterior crest of the tibia. Far medially, the limb bifurcated into superficial and deep walls forming a tunnel for the tibialis anterior tendon at about the level of the ankle joint. Laterally, the limb continued to the stem, which had three thick roots of low-signal-intensity fibers originating from the tarsal sinus and creating slings for tunnels and compartments of the extensor hallucis and extensor digitorum longus tendons (Figs. 3A and 3B).
The oblique inferomedial limb of the inferior extensor retinaculum was identified on coronal images as a thin low-signal-intensity structure passing over the tibialis anterior tendon at the level of the cuneiform bones, attaching to the anteromedial aspect of the cuneiform and the first metatarsal bones. However, the fibers under the tendon were not well identified (Figs. 4A and 4B).
The results of analysis of MR images are summarized in Table 1. Of the seven patients with a tibialis anterior tendon tear, a complete tear was present in three patients, and a partial tear was present in four. All partial tears were located at the level of the ankle joint corresponding to the interval between the superior extensor retinaculum and oblique superomedial limb of the inferior extensor retinaculum or around the oblique superomedial limb of the inferior extensor retinaculum (Figs. 5A, 5B, and 5C). In all complete tears, the proximal ends of the torn tendons were retracted to the level below the oblique superomedial limb of the inferior extensor retinaculum (Figs. 6A, 6B, and 6C). The torn tendon appeared bulbous in two cases (one partial, one complete tear) (Figs. 5A and 5B) and mildly enlarged in two cases (one partial, one complete tear). In all tears, the oblique superomedial limb of the inferior extensor retinaculum surrounding the torn tendon was visualized, with prominent thickening in four cases and with enhancement in two of three patients in whom IV contrast material was used (Fig. 5C). Abnormal fluid collections were seen within the tibialis anterior tendon sheath and in areas confined by the extensor retinaculum in four cases (Fig. 6C).
 View larger version (207K) | Fig. 3A —Inferior extensor retinaculum with tibialis anterior tendon and other extensor tendons in cadaveric foot. Oblique coronal T1-weighted MR image (TR/TE, 600/24) obtained at level of tarsal sinus (A) and corresponding anatomic section (B) show tibialis anterior tendon located within tunnel formed by oblique superomedial limb of inferior extensor retinaculum (straight arrows), visualized as low-signal-intensity band in A. This limb inserts at anterior crest of tibia (T) medially and continues to stem (curved arrow) laterally. From stem, intermediary (crossed arrow) and lateral (arrowheads) roots are seen, forming another tunnel for extensor tendon. A = tibialis anterior tendon, H = extensor hallucis longus tendon, D = extensor digitorum longus tendon. |
 View larger version (164K) | Fig. 3B —Inferior extensor retinaculum with tibialis anterior tendon and other extensor tendons in cadaveric foot. Oblique coronal T1-weighted MR image (TR/TE, 600/24) obtained at level of tarsal sinus (A) and corresponding anatomic section (B) show tibialis anterior tendon located within tunnel formed by oblique superomedial limb of inferior extensor retinaculum (straight arrows), visualized as low-signal-intensity band in A. This limb inserts at anterior crest of tibia (T) medially and continues to stem (curved arrow) laterally. From stem, intermediary (crossed arrow) and lateral (arrowheads) roots are seen, forming another tunnel for extensor tendon. A = tibialis anterior tendon, H = extensor hallucis longus tendon, D = extensor digitorum longus tendon. |
 View larger version (189K) | Fig. 4A —Tibialis anterior tendon and oblique inferomedial limb of inferior extensor retinaculum in cadaveric foot. Coronal T1-weighted MR image (TR/TE, 600/24) obtained at level of cuneiform bones (A) and nearly corresponding anatomic section (B) show tibialis anterior tendon (A) passing under oblique inferomedial limb of inferior extensor retinaculum (arrows) as thin low-signal-intensity line in A. |
 View larger version (148K) | Fig. 4B —Tibialis anterior tendon and oblique inferomedial limb of inferior extensor retinaculum in cadaveric foot. Coronal T1-weighted MR image (TR/TE, 600/24) obtained at level of cuneiform bones (A) and nearly corresponding anatomic section (B) show tibialis anterior tendon (A) passing under oblique inferomedial limb of inferior extensor retinaculum (arrows) as thin low-signal-intensity line in A. |
| Discussion | |
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The main extensor tendons of the foot, which are the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius, traverse the lower extremity, turning 90° at the anterior aspect of the ankle. As the tendons descend to the foot, they travel through three retention tunnels formed by the superior and inferior extensor retinacula, which lie across the dorsum of the foot and ankle. These retention tunnels restrict the tendons to a tight osseofibrous canal, preventing forward bowstringing but allowing a change in direction of the tendons by its function as a fibrous pulley. This arrangement enables the internal movement of the tendons along the long axis of the tunnel, a gliding mechanism that is required to avoid unnecessary friction [1, 2].
Histologically, the extensor retinaculum consists of three distinct layers: the inner gliding layer with fibroblasts and cells showing chondroid metaplasia; the thick middle layer containing collagen bundles, fibroblasts, and interspersed elastin fibers; and the outermost layer consisting of loose connective tissue with vascular channels. This basic three-layer composition has been reported to represent an adaptive mechanism to provide a smooth gliding surface and the mechanical strength that prevents bowstringing of the tendons [9].
Being one of the strongest dorsiflexors of the ankle [10], the tibialis anterior tendon, which also assists inversion of the foot, functions during the unloaded, swing phase of walking and controls plantar flexion at initial ground contact [11]. Because of its function and the relatively straight course of the tendon and its passage through retention tunnels formed by the extensor retinaculum, minimal mechanical demands are placed on it, making the tendon less subject to wear than other tendons of the foot and ankle [10].
Therefore, ruptures of the tibialis anterior tendon are uncommon. They can generally be divided into two categories: first, acute rupture secondary to laceration, a sudden violent force, and fractures [8, 12]; and, second, acute-on-chronic or spontaneous rupture [13, 14]. Spontaneous ruptures are less frequent, and most occur through its mid substance, which is the central portion of the tendon along its short axis [6, 11]. For such ruptures to occur, there must be pathophysiologic changes within the tendon causing structural weakness. An underlying degenerative process is an obvious contributing factor, which is often an age-related phenomenon [6, 8]. It may explain why most reported cases of spontaneous tendon rupture occurred in patients between the sixth and seventh decades of life [6, 8, 13, 14]. Sex is another factor that predisposes a patient to rupture of the tibialis anterior tendon. Men are affected more frequently than women. Although the reason for this sex preference is not clear, a few studies have suggested different types of physical activity, hormonal factors, and differences in body mass may be important [6, 15]. The mean age of our patients was 52.8 years, and six of seven patients were men, although one male patient was 21 years old. Other predisposing factors include tendon impingement, inflammatory arthritis, diabetes mellitus, infection, chronic microtrauma, ischemia, gout, obesity, hyperparathyroidism, systemic lupus erythematosus, and oral or local steroid therapy [5, 8, 13, 16]. One of our patients had diabetes mellitus with multiple abscesses throughout the body.
The common sites for tibialis anterior tendon rupture are its insertion into the adjacent surface of the medial cuneiform bone, beneath the oblique superomedial limb of the inferior extensor retinaculum, and in a triangular space with a lateral base formed by the superior extensor retinaculum and the oblique superomedial limb of the inferior extensor retinaculum [8, 11, 14]. This seems to be related to the vascularity of this tendon. Petersen et al. [17, 18] found that the distribution of the blood vessels of the tendon is not homogeneous, with the anterior half of the tendon along its long axis having an avascular zone of 4.5-6.7 cm in length. The location of the avascular zone corresponds to the region where the tibialis anterior tendon is under the superior and inferior retinacula and may have a to-and-fro excursion [2, 19]. This is also the site where most spontaneous ruptures of the tibialis anterior tendon occur [8, 11, 18]. In our patients, all tears occurred around the oblique superomedial limb of the inferior extensor retinaculum or in a triangular space between the superior and inferior extensor retinacula, which is consistent with the findings reported previously [8, 11, 14, 18]. This site selection supports the hypothesis that the anatomic relation of the tibialis anterior tendon with the extensor retinaculum may contribute to the vulnerability of the tendon at this site.
Patients with tibialis anterior tendon rupture may have acute or chronic symptoms that include pain, weakness, swelling near the dorsum of the foot and ankle, and foot drop. Generally, signs and symptoms are mild. The condition can be easily overlooked because, even with complete tendon rupture, dorsiflexion of the foot can be preserved by the compensatory use of the other ankle extensors [8, 19]. On physical examination, often a firm soft-tissue mass is the only clinical finding and the most commonly encountered finding in patients with tibialis anterior tendon rupture [3, 4, 6, 20, 21]. This contributes to a delay in accurate diagnosis.
It has been reported that this mass is caused by the retracted tendon stump that is located deep to the superior extensor retinaculum; when the tendon is torn at the site between or beneath the superior and inferior retinacula, the ends of the torn tendon are retracted and are often applied to the tough anterior wall of the tunnel [3, 4, 5, 12, 20]. This suggests that the extensor retinaculum surrounding the tibialis anterior tendon may play a role in causing a soft-tissue mass in patients with tendon rupture. This relationship, however, does not seem to be the only cause responsible for it. In our study, only one patient with a complete tendon tear had a prominent mass in the anterior aspect of the ankle, whereas all three complete tears were associated with the tendon retracted to the level of the oblique superomedial limb of the inferior extensor retinaculum. Moreover, one patient with a partial tear had a prominent bulbous lump on the dorsum of the ankle that was caused by a combination of a markedly swollen torn tendon and soft-tissue swelling. This raised the possibility that a mass at the ankle in patients with tibialis anterior tendon rupture might result from various causes, although the major cause remains the tendon retraction to the level of the extensor retinaculum.
 View larger version (145K) | Fig. 5A —Partial tear of tibialis anterior tendon in 63-year-old man. (Reprinted from Internal Derangements of Joints: Emphasis on MRI, Resnick and Kang, 1997: p. 870 with permission from Elsevier) Sagittal T2-weighted MR image (TR/TE, 5,200/90) of ankle shows torn tendon (arrow) appearing as bulbous mass at level of ankle joint, which corresponds to interval between superior extensor retinaculum and oblique superomedial limb of inferior extensor retinaculum. |
 View larger version (108K) | Fig. 5B —Partial tear of tibialis anterior tendon in 63-year-old man. (Reprinted from Internal Derangements of Joints: Emphasis on MRI, Resnick and Kang, 1997: p. 870 with permission from Elsevier) Transverse T1-weighted MR images (600/13) of ankle with fat saturation after IV contrast enhancement show prominent enhancement of tendon sheath surrounding torn tendon (A) in B and along oblique superomedial limb of inferior extensor retinaculum (arrows) in C. |
 View larger version (114K) | Fig. 5C —Partial tear of tibialis anterior tendon in 63-year-old man. (Reprinted from Internal Derangements of Joints: Emphasis on MRI, Resnick and Kang, 1997: p. 870 with permission from Elsevier) Transverse T1-weighted MR images (600/13) of ankle with fat saturation after IV contrast enhancement show prominent enhancement of tendon sheath surrounding torn tendon (A) in B and along oblique superomedial limb of inferior extensor retinaculum (arrows) in C. |
Barnett and Hammond [4] reported that a patient with tibialis anterior tendon rupture developed a painful mass on the anterior aspect of the ankle 1 month after a minor injury. At surgery, the mass was found to be in continuity with the torn tendon and consisted of an organized hematoma and fibrous tissue surrounding the torn tendon stump, which was adherent to a thickened synovial sheath. Although no evidence of an organized hematoma was evident in our cases, irregular thickening and enhancement of the extensor retinaculum surrounding a torn tendon, which was interpreted as fibrosis, were noted regardless of whether the tendon tear was partial or complete. Such progressing fibrotic change in the tendon sheath and surrounding retinaculum likely represents another cause for a mass.
A tendinous gap that is apparent at the site of a complete tear can be filled with fluid, fat, or scar tissue depending on the age of the tendon rupture [8, 16]. A fluid collection can be observed within the tendon sheath even in cases of a partial tear. The tendon sheath can also be torn such that the fluid within the sheath may extend into the adjacent tissue. In such a circumstance, the extensor retinaculum may function as a barrier, preventing the spread of the fluid collection beyond it. Three of our cases showed fluid collections in the adjacent tendon sheath and in the area confined by the extensor retinaculum.
This study has several limitations. First, both the total number of patients and the number of patients in whom surgical proof was available were small. Nevertheless, to our knowledge, the present study contains the largest number of patients with a partial or complete tear of the tibialis anterior tendon in the radiology literature. Second, the MR protocols conducted in cadavers used technical parameters aimed at a limited portion of the foot. The resulting images, however, showed detailed anatomy about the tibialis anterior tendon and the extensor retinaculum, and such protocols may be useful when the clinical findings are related to assessment of the tibialis anterior tendon and the extensor retinaculum. Third, the clinical study was retrospective in nature, with varying imaging protocols used in patients from different institutes.
In conclusion, we have shown the anatomic relationship of the tibialis anterior tendon and extensor retinaculum of the foot and ankle in cadavers and in patients with a tibialis anterior tendon tear. This relationship may influence the causation and clinical presentations of tears of the tibialis anterior tendon. MRI is an excellent method for visualizing the anatomy of these structures and confirming the diagnosis of tendon tear.
 View larger version (154K) | Fig. 6A —Complete tear of tibialis anterior tendon in 33-year-old man. Sagittal proton density-weighted MR image (TR/TE, 1,800/20) of ankle reveals complete rupture of tibialis anterior tendon (arrow) at level around oblique superomedial limb of inferior extensor retinaculum. |
 View larger version (187K) | Fig. 6B —Complete tear of tibialis anterior tendon in 33-year-old man. Coronal T2-weighted MR image (7,500/60) of ankle with fat saturation shows oblique superomedial limb of inferior extensor retinaculum (arrows) around proximal torn tendon. |
 View larger version (166K) | Fig. 6C —Complete tear of tibialis anterior tendon in 33-year-old man. Coronal T2-weighted MR image (7,500/60) of ankle with fat saturation distal to B shows empty tendon sheath filled with fluid (arrows). |
Address correspondence to D. Resnick.
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