| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Original Report |
1
Department of Radiology, Thomas Jefferson University Hospital, 111 S. 11th
St., Rm. 3350 G, Philadelphia, PA 19107.
2
Present address: Department of Radiology, University of Pennsylvania Medical
Center, 3400 Spruce St., Philadelphia, PA 19104.
3
Department of Orthopedic Surgery, Pennsylvania Hospital, 800 Spruce St.,
Philadelphia, PA 19107.
Received August 23, 2000;
accepted after revision October 9, 2000.
Presented at the annual meeting of the American Roentgen Ray Society, New
Orleans, May 1999.
Abstract
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CONCLUSION. Entrapment of the flexor hallucis longus tendon may be due to an enlarged os trigonumtarsitarsi, calcaneal fracture, and soft-tissue scar. These disorders have characteristic imaging findings that may be revealed on MR imaging.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
MR imaging was performed on a 1.5-T scanner (Signa; General Electric Medical Systems, Milwaukee, WI) using an extremity coil. The foot and ankle were in neutral position. The following MR imaging sequences were typically performed: sagittal T1-weighted imaging (TR/TE, 500/10), sagittal fast short tau inversion recovery imaging (TR/TEeff, 6000/40; inversion time, 150 msec), axial proton density—weighted imaging (TR/TE, 4000/40), and axial fat-suppressed fast spin-echo imaging TR/TEeff, 6000/90). The field of view was 16 cm, the matrix was 256 x 256 (except the axial proton density—weighted sequence, which had a 512 x 256 matrix), the slice thickness was 4 mm with a 1-mm interslice gap.
The medical record of each patient was reviewed for clinical signs and symptoms, treatment method and outcome, and operative reports if available. MR images were reviewed by two observers with agreement by consensus for the following: the presence of mechanical entrapment of the flexor hallucis longus tendon, abrupt cutoff of the flexor hallucis longus tendon synovial sheath fluid at the posterior talus, abnormal flexor hallucis longus tendon morphology or signal, and the presence of an os trigonumtarsitarsi. On the basis of these findings, the presumed level of entrapment was determined.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
MR imaging revealed flexor hallucis longus tendon entrapment by bone or soft tissue in all 12 patients. Seven flexor hallucis longus tendons were entrapped by variably sized os trigona (Fig. 1), three by old calcaneal fractures (Fig. 2), one by prior posterior malleolus—capsule injury, one by previous medial malleolar fracture, and one by soft-tissue scarring from penetrating injury (Fig. 3A,3B).
|
|
|
|
Abrupt cutoff of flexor hallucis longus tendon synovial sheath fluid with differential volumes of fluid above and below the site of entrapment was seen in eight of 13 ankles (Fig. 4A,4B). Abnormal flexor hallucis longus tendon morphology with alterations in either tendon size or signal intensity on T1- or T2-weighted images was observed in six of 13 ankles.
|
|
Surgical findings confirmed the imaging diagnosis of flexor hallucis longus tendon entrapment in all six patients who underwent surgery. The surgical findings included abnormal motion of the flexor hallucis longus tendon (n = 4) and tendon scarring (n = 2). The remaining patients were treated nonoperatively with aggressive physical therapy. Four patients had prior fractures of the ankle and presumably had osseous or soft-tissue scarring in the region of the flexor hallucis longus tendon. Two patients were ballet dancers who had flexor hallucis longus tendon entrapment caused by an os trigonum; one of these two patients had bilateral flexor hallucis longus tendon entrapment.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Similar to the other two medial tendons, the flexor hallucis longus tendon is contained within a fibroosseous tunnel behind the medial malleolus, beneath the flexor retinaculum. The tendon courses through the tunnel between the medial and lateral talar tubercles of the posterior talus, which is lined by a synovial sheath [3]. The tendon enters the foot by crossing the posterior subtalar joint and passing under the inferior aspect of the sustentaculum tali. This is analogous to a "rope through a pulley." The usual location for tendon entrapment is the fibroosseous tunnel where the tendon changes direction from a vertical course dorsal to the talus to a horizontal course beneath the calcaneus [4].
Injuries of the flexor hallucis longus tendon have classically been described in ballet dancers from plantar flexion stress [5]. This tendon is considered the "Achilles tendon" of the foot in dancers. These individuals must perform repetitive push-off maneuvers from their fore-feet. Symptoms are exacerbated in the en pointe position, in which the flexor hallucis longus tendon may be stretched beyond its physiologic limits. Sporting activities that involve forced plantar flexion, such as downhill running and soccer, also predispose to flexor hallucis longus tendon injury.
Entrapment of the flexor hallucis longus tendon may result from an enlarged os trigonum as repetitive pressure is placed on the flexor hallucis longus tendon by the ossicle. The os trigonum is the unfused lateral tubercle of the posterior talus, found in approximately 14-25% of the healthy population [6]. The flexor hallucis longus tendon may be compressed by the os trigonum, which is on the lateral side of the fibroosseous tunnel. This compression can result in posterior ankle impingement when weight bearing occurs with plantar flexion [7]. This activity decreases the space between the posterior tibia and the superior calcaneus and can cause posteromedial ankle pain directly posterior to the medial malleolus. This pain can be elicited on physical examination by placing the foot in extreme plantar flexion or maximum dorsiflexion of the great toe with resistance [8]. We found seven cases in six patients that were entrapped by an os trigonum, but the size of the os trigonum is a poor predictor of clinical symptoms. Posterior ankle impingement can occur in the absence of an os trigonum as a result of osseous fragments from a calcaneal fracture or soft-tissue scar between the calcaneus and talus [9].
We found flexor hallucis longus tendon abnormalities were best visualized on sagittal and axial MR images. On the sagittal MR image, the flexor hallucis longus tendon is usually seen one slice lateral to the posterior tibial tendon, as it curves around the sustentaculum. The flexor hallucis longus tendon is the most posterior of the medial tendons on axial MR images. Excessive fluid loculated around a normal-appearing tendon is characteristic of tenosynovitis, usually proximal to the talar fibroosseous tunnel [10]. Because up to 20% of individuals have a normal communication between the flexor hallucis longus tendon synovial sheath and the ankle joint, it is important not to mistake physiologic synovial fluid within the tendon sheath with an abnormality [11]. It is often difficult to determine how much synovial fluid is abnormal. We found that a large amount of fluid within the flexor hallucis longus tendon sheath with abrupt cutoff of fluid at the level of the posterior talus is most suggestive of entrapment. This finding was identified in all six patients with an os trigonum and in one patient with prior calcaneal fracture.
Most of the reported cases of flexor hallucis longus tendon abnormalities have focused on ballet dancers and have implicated an enlarged os trigonum. Two of our patients were ballet dancers, including one who had bilateral flexor hallucis longus tendon entrapment caused by os trigonum. Four of our patients with suspected flexor hallucis longus tendon entrapment from an os trigonum had a surgical resection of the os with resolution of symptoms after surgery.
In our current series, six of 12 patients had a posttraumatic cause for the flexor hallucis longus tendon entrapment by either osseous or soft-tissue scar. With hindfoot trauma, especially calcaneal fractures, fracture comminution with multiple small fragments is frequent. These fragments can impinge on the flexor hallucis longus tendon in a mechanism similar to that of peroneal tendon subluxation, another well-known complication of calcaneal injuries [12]. Bony impingement was identified in two patients and soft-tissue scar was seen in two patients. Five of these six patients had abnormal morphology of the flexor hallucis longus tendon in association with the other findings. Two of the six patients underwent surgical release of the flexor hallucis longus tendon that resulted in symptomatic and functional improvement. The other four patients declined surgery and proceeded with intensive physical therapy.
We acknowledge several limitations to this study. The total number of patients was small and not all the patients underwent subsequent surgical correlation. However, to our knowledge, this series describes the largest number of non—ballet dancers with abnormalities of the flexor hallucis longus tendon. This series also represents the first description of the MR imaging findings of flexor hallucis longus tendon entrapment.
In summary, MR imaging assessment of entrapment of the flexor hallucis longus tendon may be helpful in patients who have persistent posterior ankle pain, especially in patients with a known os trigonum or previous trauma. MR imaging in the axial and sagittal planes is sufficient to detect abnormalities of the flexor hallucis longus tendon. In patients with an os trigonum, the presence of differential amounts of synovial fluid above and below the os was the most helpful sign. In patients with previous trauma, the identification of soft-tissue or osseous scar surrounding an abnormal flexor hallucis longus tendon was most characteristic.
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  J.-B. Na, A. G. Bergman, L. M. Oloff, and C. F. Beaulieu The Flexor Hallucis Longus: Tenographic Technique and Correlation of Imaging Findings with Surgery in 39 Ankles Radiology, September 1, 2005; 236(3): 974 - 982. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J C Hillier, K Peace, A Hulme, and J C Healy MRI features of foot and ankle injuries in ballet dancers Br. J. Radiol., June 1, 2004; 77(918): 532 - 537. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
