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(Radiographics. 2000;20:S181-S197.)
© RSNA, 2000

Extremities

Plantar Fasciitis and Fascial Rupture: MR Imaging Findings in 26 Patients Supplemented with Anatomic Data in Cadavers1

Daphne J. Theodorou, MD, Stavroula J. Theodorou, MD, Yousuke Kakitsubata, MD, Nittaya Lektrakul, MD, Garry E. Gold, MD, Bernard Roger, MD and Donald Resnick, MD

1 From the Department of Radiology, School of Medicine, University of California San Diego (D.J.T., S.J.T., Y.K., N.L., G.E.G., D.R.); and the Department of Radiology, Hôpital Pitié-Salpêtrière, Paris, France (B.R.). Presented as a scientific exhibit at the 1999 RSNA scientific assembly. Received March 2, 2000; revision requested April 11 and received May 18; accepted June 2. Supported in part by grant SA-360 from the U.S. Veterans Administration and educational grant U-033 from the A. S. Onassis Public Benefit Foundation. Address correspondence to D.R., Department of Radiology (114), Veterans Affairs Medical Center, 3350 La Jolla Village Dr, San Diego, CA 92161.


   Abstract
Top
 Abstract
Introduction
 Anatomic Considerations
 Materials and Methods
 Results
 Discussion
 References
 
Understanding of the normal anatomy of the plantar aponeurosis (PA) and familiarity with pathologic conditions are required for an accurate evaluation of the patient with subcalcaneal heel pain. In this study, we evaluated the diagnostic capabilities of magnetic resonance (MR) imaging in the assessment of the PA with close anatomic correlation. Herein, we describe the MR imaging features of plantar fasciitis and fascial rupture in 26 patients. High-spatial-resolution MR imaging was performed in four cadaveric feet, and a prescribed imaging plane was used for depiction of the peroneal component of the PA. MR imaging delineated the anatomy of the PA and perifascial soft tissues. The peroneal component was best visualized in prescribed sagittal oblique images. Perifascial edema was the most common finding of plantar fasciitis, and it was remarkable in those cases with acute fascial rupture. MR imaging reliably delineated the anatomy of the PA and may allow precise localization and definition of the extent of involvement in disease processes.

Index Terms: Fasciitis, 46.24 • Foot, abnormalities, 46.24 • Foot, MR, 46.121411, 46.121412, 46.121413, 46.12143


   Introduction
Top
 Abstract
 Introduction
Anatomic Considerations
 Materials and Methods
 Results
 Discussion
 References
 
The plantar aponeurosis (PA), or plantar fascia, is the strong, fibrous investing layer of the sole of the foot (1). Because of its combined static and dynamic role in longitudinal arch support in the foot (2,3) and the capability of allowing the loading capacity on the foot during weight bearing, abnormalities of the PA are commonly encountered in the diagnostic evaluation of subcalcaneal heel pain. Differential diagnostic considerations specific to the PA, however, include numerous diseases and pathologic processes (4,5).

Plantar fasciitis, a frequent cause of heel pain, is a low-grade inflammatory process involving the PA with or without involvement of the perifascial structures. Plantar fasciitis can result from a number of causes, which in general fall into three major categories: mechanical, degenerative, and systemic (6). Although usually not disabling, plantar fasciitis may deter patients from occupational weight-bearing and athletic and recreational activities, and it also may be associated with altered gait patterns (5). In addition, the inflammatory process may extend to adjacent anatomic structures, including the medial calcaneal nerve and the mixed nerve to the abductor digiti minimi muscles (4,7).

Among the indications for imaging of the PA, assessment of its anatomic integrity is important in athletes engaged in running and jumping activities (8,9), as ruptures of the PA (either complete or partial) are caused by forcible plantar flexion and are common in competitive athletes. Repetitive stress or minor trauma to the PA, however, also may result in rupture, and spontaneous rupture of the PA may occur in patients with prior plantar fasciitis, especially in those treated with local steroid injections (8–10).

Conventional radiography, bone scintigraphy, and ultrasonography (US) have been recognized previously as aids in the clinical evaluation of patients with abnormalities affecting the PA (4,11–14). MR imaging also has been reported to be helpful in the detection and diagnosis of most of these abnormalities (15–19). The purpose of this study was to evaluate the usefulness of MR imaging in depiction of anatomic features of the plantar fascia and perifascial structures in cadaveric feet and to describe and illustrate the MR imaging findings in 26 patients with plantar fasciitis and fascial rupture. Findings in our study suggest that the gracile PA can be best visualized with high-spatial-resolution MR imaging in all three imaging planes and, if clinically indicated, a prescribed sagittal lateral oblique imaging plane can provide additional information regarding its peroneal component.


   Anatomic Considerations
Top
 Abstract
 Introduction
 Anatomic Considerations
Materials and Methods
 Results
 Discussion
 References
 
The PA is a subcutaneous, complex ligamentous structure extending from the calcaneus to the ball of the foot. Arising from the plantar aspect of the posteromedial calcaneal tuberosity in the hindfoot, the PA progressively subdivides into central, medial, and lateral components as it gradually widens and courses distally (Fig 1) (1,20). The central, or major, component of the PA is the largest, thickest, and strongest. It is triangular and divides into five bands at the midmetatarsal level. Proximal to the metatarsal heads, each longitudinally oriented band divides into a deep tract (lacertus aponeuroticus profundus) and a superficial tract (lacertus aponeuroticus superficialis) (21). The central three superficial tracts continue their course distally toward the toes. Anterior to the metatarsal heads and proximal to the skin creases, these three central superficial components insert into the skin. The two marginal superficial tracts run to the margins of the foot; the medial tract passes distally toward the hallux, and the lateral tract continues in the direction of the fifth toe.



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  		Figure 1. Schematic of the PA. C = calcaneus, DB = digital bands of PA, PAC = PA central component, PAL = PA lateral component, PAM = PA medial component.

 
Proximal and superficial to the metatarsal heads, the PA is crossed by transverse retinacular bands. Oblique fibers extend from the subcutaneous transverse bands into the depth and connect with longitudinal septae of the PA and the bases of the proximal phalanges (22).

Distal and deep to the metatarsal heads, a transverse retinacular system attaches to the five flexor tendon sheaths, and superficially the system is attached to the skin. In the plantar aspect of the region of the metatarsal heads, transversely oriented aponeurotic bands form a weblike retinacular system, which divides the area between the web spaces and dermis (1,21–23).

The medial border of the central component of the PA is in continuity with longitudinal thin fibers covering the abductor hallucis muscle, and it blends with the dorsal aponeurosis. The lateral border of the central component of the PA is filled in by a fine network of aponeurotic fibers and fatty lobules. The central segment of the PA is connected laterally and medially to the intermuscular longitudinal septae of the planta pedis (24).

The peroneal or lateral component of the PA is variable as it may be of four distinctive types: complete and well developed, complete and thin, incomplete with only partial distal extension, or absent distal extension (25). The peroneal component originates from the lateral margin of the medial calcaneal tubercle, in close connection with the origin of the abductor digiti minimi muscle, and extends in the direction of the cuboid and bifurcates into a medial and a lateral component. The lateral band, or crux, is the stronger component and inserts in the base of the fifth metatarsal bone. The medial band, or crux, turns around the abductor digiti minimi muscle, passes into the depth under the neurovascular bundle to the fifth toe, and blends with the plantar plate of the fourth and, occasionally, the third metatarsophalangeal joints (1,26).

The tibial or medial component of the PA forms the covering fascia of the abductor hallucis muscle. The fibers are oriented distally and medially and are in continuity with the dorsal aponeurosis of the foot, the inferomedial arm of the inferior extensor retinaculum, and the flexor retinaculum (1).

Several nerve branches supply the medial heel region. The posterior tibial nerve is located on the medial side of the foot posterior to the tendons of the posterior tibialis and flexor digitorum longus muscle and beneath the flexor retinaculum. One or two branches of the medial calcaneal nerve arise at approximately the level of the medial malleolus and pass subcutaneously and superficially to the PA to innervate the heel pad and skin. The nerve to the abductor digiti quinti muscle, which is next to the medial calcaneal nerve, branches off the lateral plantar nerve, passes deep to the PA between the abductor hallucis and the medial head of the quadratus plantae muscle, and then turns laterally to innervate the abductor digiti quinti muscle. The medial and lateral plantar nerves, which are the anterior and posterior division branches of the posterior tibial nerve, also pass deep to the abductor hallucis and, through separate foramina of the abductor muscles, they exit in the abductor muscles continuing their course to the foot (4,7,27).


   Materials and Methods
Top
 Abstract
 Introduction
 Anatomic Considerations
 Materials and Methods
Results
 Discussion
 References
 
To better characterize the anatomic features of the PA as seen with MR imaging and to understand the implications of a pathologic condition involving the plantar fascia and perifascial tissues, high-spatial-resolution MR imaging studies were performed in cadaveric feet, and specimen images were compared with corresponding anatomic slices. Subsequently, we retrospectively reviewed the MR imaging examinations of 26 patients referred for imaging evaluation of subcalcaneal heel pain, with particular attention to identification of the PA and surrounding structures in all imaging planes.

Cadaveric Study
Four fresh human feet (transected at the level of the ankle joint) were harvested from nonembalmed cadavers (two men, two women; age range, 78–91 years at the time of death; mean age, 83 years). The cadaveric specimens were immediately deep-frozen at –40°C (Bio-Freezer; Forma Scientific, Marietta, Ohio). None of the cadavers had evidence of surgical intervention or previous injuries in or about the studied foot. All cadaveric specimens were examined with radiography to be certain there were no obvious bone or soft-tissue pathologic conditions. The cadaveric specimens were allowed to thaw for 24 hours at room temperature prior to MR imaging. Subsequently, the cadaveric specimens were prepared according to the methods described in the literature (28).

MR images were obtained with a 1.5-T superconducting MR imager (Signa; GE Medical Systems, Milwaukee, Wis) with a 5-inch (13-cm) standard small flexible surface coil (Flex Coil; Medical Advances, Milwaukee, Wis). All cadaveric feet were placed in an approximately neutral weight-bearing position and immobilized with foam pads. Additional stress by means of dorsiflexion (extension) and plantar flexion (flexion) also was manually applied to the toes.

Imaging was performed in the coronal, transverse, and sagittal planes. Because the course of the peroneal (lateral) component of the PA is oriented obliquely, a special sagittal oblique imaging plane was electronically prescribed (to parallel either the abductor digiti minimi muscle or the peroneus brevis tendon toward its attachment at the base of the fifth metatarsal bone) from a conventional transverse image of the foot (Fig 2).



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  		Figure 2. Cadaveric transverse T1-weighted SE MR image (600/22, 256 x 160 matrix, one signal acquired, 16-cm field of view) demonstrates the technique used to prescribe the sagittal lateral oblique sequence. The prescription grid is tilted to parallel the peroneus brevis tendon (arrow).

 
The MR imaging protocol consisted of T1-weighted spin-echo (SE) sequences (repetition time msec/echo time msec = 600/22, two signals acquired ). To acquire a higher signal-to-noise ratio, a section thickness of 1.0 mm was used without an intersection gap. The field of view was 10 x 10 cm in the coronal, transverse, and sagittal planes and 13 x 13 cm in the prescribed oblique sagittal plane. A 16 x 16-cm field of view was used when the foot was imaged in the sagittal plane with forceful manual stress applied to the toes. The data acquisition matrix was 512 x 256 pixels. Subsequently, three-dimensional spoiled gradient-recalled acquisition in the steady state (SPGR) images (38/12, 60° flip angle, 128 partitions) were obtained in the coronal and sagittal imaging planes. For the volumetric acquisitions, a matrix of 256 x 256 and section thickness of 1 mm with no gap were used, and two signals were acquired. MR images were evaluated by consensus by two musculoskeletal radiologists (D.J.T., S.J.T.) with emphasis on the components of the PA and adjacent structures.

After MR imaging was complete, the cadaveric specimens were frozen again at –60°C for more than 72 hours and were subsequently cut with a band saw (28) into 3-mm-thick slices, so that anatomic slices corresponded closely to each of the four MR imaging planes. The anatomic slices were cleaned with running water for macroscopic inspection. Each slice was recorded photographically (28) and imaged (Faxitron; Hewlett Packard, McMinnville, Ore). To determine the anatomic relationships of the PA, the findings at MR imaging were correlated with those derived from inspection of cadaveric slices.

Clinical Study
Available clinical information and MR imaging studies in 26 clinical cases (15 female, 11 male patients; age range, 15–65 years; mean age, 39 years) with subcalcaneal heel pain and clinical evidence of plantar fasciitis or fascial rupture were reviewed, tabulated, and analyzed. Cases were collected from three institutions, with 0.5- and 1.5-T MR imagers and varying imaging parameters. In all cases, imaging was performed in three standard planes with the following sequences: coronal and sagittal gradient echo (360–620/12–25, 25° flip angle), SE T1 weighted (360–850/12–25), fat-suppressed fast SE T2 weighted (3,267–4,394/67–75, echo train length of four to six), fat-suppressed fast SE intermediate weighted (2,000–2,200/20–23), and short inversion time inversion recovery (STIR) (3,000–4,585/34–60/150 [inversion time msec]). In six cases, SE T1-weighted or gradient-echo MR images were acquired before and after intravenous administration of gadolinium-containing contrast material (Magnevist; Schering, Berlin, Germany). Retrospective analysis of the MR images was accomplished by consensus by two musculoskeletal radiologists (D.J.T., S.J.T.) who recorded the anatomic integrity, course, and size of the PA; lesion location in the longitudinal and transverse planes; intrafascial and perifascial soft-tissue edema; and calcaneal marrow edema.


   Results
Top
 Abstract
 Introduction
 Anatomic Considerations
 Materials and Methods
 Results
Discussion
 References
 
Cadaveric Study
The complex anatomy of the PA was well demonstrated on T1-weighted SE MR images. Gradient-echo MR images did not improve visualization of the PA.

On T1-weighted images, all three components of the PA had low signal intensity in all imaging planes. Owing to the characteristic high signal intensity of the adjacent heel fat pad and the intermediate signal intensity of muscles, the PA was clearly outlined as a uniform, hypointense, bandlike structure. Optimal contrast resolution achieved on T1-weighted MR images allowed depiction of all bones, ligaments, tendons, perifascial soft tissues, and the heel pad. In addition, high-spatial-resolution MR images adequately depicted the major components of the delicate plantar neurovascular bundle.

No definite alterations in intra- or perifascial signal intensity were found on T1-weighted SE MR images. Macroscopic inspection of the sliced cadaveric specimens confirmed the absence of a pathologic condition involving the PA and perifascial tissue.

Transverse Plane
The medial and lateral calcaneal tubercles were visualized in the transverse plane. Proximally, the attachment of the PA to the calcaneus was demonstrated, but this plane did not provide satisfactory delineation of the components of the PA (Fig 3). MR imaging in the transverse plane, however, permitted clear delineation of the long plantar ligament and its attachment to the medial and anterior calcaneal tubercles. In this plane, the abductor digiti minimi, the flexor digitorum brevis, and the abductor hallucis muscles were also seen although their intimate relationship with the components of the PA could not be demonstrated. Transverse images also displayed the position and portions of or part of the anatomic course of the lateral and medial plantar nerves.



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  		Figure 3a. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Transverse T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view). (b) Corresponding anatomic slice. C = calcaneus, LP = lateral calcaneal process, MP = medial calcaneal process, PAC = PA central component, PAL = PA lateral component.

 


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  		Figure 3b. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Transverse T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view). (b) Corresponding anatomic slice. C = calcaneus, LP = lateral calcaneal process, MP = medial calcaneal process, PAC = PA central component, PAL = PA lateral component.

 
Coronal Plane
The origin of the PA from the plantar aspect of the posteromedial calcaneal tuberosity was readily demonstrated (Fig 4). MR imaging in the coronal plane was best suited for delineating the trifurcation of the PA into its central, medial, and lateral components. Coronal images allowed simultaneous visualization of all three components of the PA (Fig 5). The central component of the PA was narrow at the site of its attachment to the calcaneus, and it conformed to the convexity of the calcaneal tuberosity (Fig 4). The central component was broader and thicker distally, near the metatarsal heads. In all cadaveric specimens, the peroneal (or lateral) component of the PA was well developed. It was visualized originating from the lateral margin of the medial calcaneal tubercle and coursing distally toward its site of attachment at the base of the fifth metatarsal bone. Although the lateral crux was optimally depicted, the bifurcation of the peroneal component of the PA was not well demonstrated. The medial component of the PA was also well demonstrated. It was thinner than the other components of the PA, and it was seen blending with the flexor retinaculum.



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  		Figure 4a. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view). (b) Corresponding anatomic slice. C = calcaneus, CFP = calcaneal fat pad, PAC = PA central component (curved arrow).

 


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  		Figure 4b. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view). (b) Corresponding anatomic slice. C = calcaneus, CFP = calcaneal fat pad, PAC = PA central component (curved arrow).

 


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  		Figure 5a. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view). (b) Corresponding anatomic slice. Long white arrow = medial plantar nerve, open arrow = lateral plantar nerve, short white arrow = posterior tibial artery; a = lateral plantar artery, C = calcaneus, CFP = calcaneal fat pad, ITCL = interosseous talocalcaneal ligament, PAC = PA central component (curved arrow), PAL = PA lateral component (black arrow), PAM = PA medial component (arrowheads), T = talus; 1 = peroneus brevis tendon, 2 = peroneus longus tendon, 3 = long plantar ligament, 4 = abductor digiti minimi muscle, 5 = flexor digitorum brevis muscle, 6 = quadratus plantae muscle, 7 = abductor hallucis muscle, 8 = flexor digitorum longus tendon, 9 = flexor hallucis longus tendon.

 


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  		Figure 5b. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view). (b) Corresponding anatomic slice. Long white arrow = medial plantar nerve, open arrow = lateral plantar nerve, short white arrow = posterior tibial artery; a = lateral plantar artery, C = calcaneus, CFP = calcaneal fat pad, ITCL = interosseous talocalcaneal ligament, PAC = PA central component (curved arrow), PAL = PA lateral component (black arrow), PAM = PA medial component (arrowheads), T = talus; 1 = peroneus brevis tendon, 2 = peroneus longus tendon, 3 = long plantar ligament, 4 = abductor digiti minimi muscle, 5 = flexor digitorum brevis muscle, 6 = quadratus plantae muscle, 7 = abductor hallucis muscle, 8 = flexor digitorum longus tendon, 9 = flexor hallucis longus tendon.

 
The coronal imaging plane afforded clear delineation of the various musculotendinous units. Coronal images also showed the position of the long plantar ligament. Deep to the central component of the PA, the flexor digitorum brevis muscle was evident, as was the intimate relationship of the abductor digiti minimi and the abductor hallucis muscles with their investing lateral and medial components of the PA (Figs 5, 6).



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  		Figure 6a. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view). (b) Corresponding anatomic slice. Black arrows = flexor digitorum brevis tendons, curved arrows = flexor digitorum longus tendons, open arrows = plantar metatarsal arteries,; M1-M5 = metatarsal bones 1-5, PAC = PA central component (arrowheads); 1 = abductor hallucis muscle, 2 = abductor hallucis tendon, 3 = flexor hallucis brevis muscle, 4 = flexor hallucis longus tendon, 5 = abductor hallucis muscle oblique head, 6 = abductor digiti minimi tendon, 7 = flexor digiti minimi brevis muscle.

 


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  		Figure 6b. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view). (b) Corresponding anatomic slice. Black arrows = flexor digitorum brevis tendons, curved arrows = flexor digitorum longus tendons, open arrows = plantar metatarsal arteries,; M1M5 = metatarsal bones 15, PAC = PA central component (arrowheads); 1 = abductor hallucis muscle, 2 = abductor hallucis tendon, 3 = flexor hallucis brevis muscle, 4 = flexor hallucis longus tendon, 5 = abductor hallucis muscle oblique head, 6 = abductor digiti minimi tendon, 7 = flexor digiti minimi brevis muscle.

 
Posterior to the posterior tibialis tendon, the tibial nerve was seen. Deep to the abductor hallucis muscle, the medial plantar and, inferior to it, the lateral plantar nerves also were recognized (Figs 5, 6). In this plane, application of excessive mechanical stress to the foot by means of dorsal and plantar flexion allowed demonstration of the functional properties of the PA. In particular, hyperextension (excessive dorsal flexion) of the toes was shown to increase tension in the PA (Fig 7a–7c), and hyperflexion (excessive plantar flexion) of the toes was shown to increase flexion and creasing of the PA (Fig 7b–7d).



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  		Figure 7a. MR imaging demonstration of the elastic properties of the PA after application of manual stress to the toes in a cadaveric foot specimen (a and b are from slices at approximately the same level, c and d are from a slice 6 mm more distal to the metatarsal bones). a and c were obtained with dorsiflexion (extension) of the toes, b and d were obtained with plantar flexion of the toes. Scale is in centimeters. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows the straightened central component of the PA (arrows). (b) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows bowing of the central component of the PA (arrows). (c) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows the straightened central component of the PA (arrows). (d) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows creasing of the central component of the PA (arrows).

 


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  		Figure 7b. MR imaging demonstration of the elastic properties of the PA after application of manual stress to the toes in a cadaveric foot specimen (a and b are from slices at approximately the same level, c and d are from a slice 6 mm more distal to the metatarsal bones). a and c were obtained with dorsiflexion (extension) of the toes, b and d were obtained with plantar flexion of the toes. Scale is in centimeters. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows the straightened central component of the PA (arrows). (b) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows bowing of the central component of the PA (arrows). (c) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows the straightened central component of the PA (arrows). (d) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows creasing of the central component of the PA (arrows).

 


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  		Figure 7c. MR imaging demonstration of the elastic properties of the PA after application of manual stress to the toes in a cadaveric foot specimen (a and b are from slices at approximately the same level, c and d are from a slice 6 mm more distal to the metatarsal bones). a and c were obtained with dorsiflexion (extension) of the toes, b and d were obtained with plantar flexion of the toes. Scale is in centimeters. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows the straightened central component of the PA (arrows). (b) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows bowing of the central component of the PA (arrows). (c) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows the straightened central component of the PA (arrows). (d) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows creasing of the central component of the PA (arrows).

 


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  		Figure 7d. MR imaging demonstration of the elastic properties of the PA after application of manual stress to the toes in a cadaveric foot specimen (a and b are from slices at approximately the same level, c and d are from a slice 6 mm more distal to the metatarsal bones). a and c were obtained with dorsiflexion (extension) of the toes, b and d were obtained with plantar flexion of the toes. Scale is in centimeters. (a) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows the straightened central component of the PA (arrows). (b) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows bowing of the central component of the PA (arrows). (c) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows the straightened central component of the PA (arrows). (d) Coronal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 10-cm field of view) shows creasing of the central component of the PA (arrows).

 
Sagittal Plane
The sagittal imaging plane allowed the best depiction of the extent, anatomic integrity, and course of the central component of the PA (Fig 8). In the sagittal plane, the three components of the PA could be identified on serial images, but this plane was not useful for simultaneous assessment of all three components of the PA and demonstration of its lateral component. The origin of the PA from the posteromedial calcaneal tuberosity was also well demonstrated. Sagittal imaging allowed the best delineation of the dorsoplantar (anteroposterior) thickness of the PA (Fig 8). Sagittal images also showed the position of the abductor digiti minimi, flexor digitorum brevis, and abductor hallucis muscles deep to each one of the three components of the PA. Delineation of the long plantar ligament in its entirety was optimal. Evaluation of the functional properties of the PA was also possible in this imaging plane by means of dynamic application of mechanical stress to the foot (dorsiflexion and plantar flexion). Alterations in pulling of the PA were best appreciated on the sagittal MR images.



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  		Figure 8a. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Sagittal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 16-cm field of view). Scale is in centimeters. (b) Corresponding anatomic slice. Arrowheads = PA, open arrow = lateral plantar nerve, solid arrow = lateral plantar artery; C = calcaneus, CFP = calcaneal fat pad, CU = cuboid bone, IC = intermediate cuneiform bone, LC = lateral cuneiform bone, M2 = second metatarsal bone, N = navicular bone, QP = quadratus plantae muscle, T = talus; 1 = flexor digitorum brevis muscle, 2 = flexor hallucis brevis muscle, 3 = flexor digitorum longus tendon.

 


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  		Figure 8b. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Sagittal T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 16-cm field of view). Scale is in centimeters. (b) Corresponding anatomic slice. Arrowheads = PA, open arrow = lateral plantar nerve, solid arrow = lateral plantar artery; C = calcaneus, CFP = calcaneal fat pad, CU = cuboid bone, IC = intermediate cuneiform bone, LC = lateral cuneiform bone, M2 = second metatarsal bone, N = navicular bone, QP = quadratus plantae muscle, T = talus; 1 = flexor digitorum brevis muscle, 2 = flexor hallucis brevis muscle, 3 = flexor digitorum longus tendon.

 
Prescribed Sagittal Lateral Oblique Plane
The prescribed sagittal lateral oblique plane permitted the best assessment of the lateral component of the PA and substantially improved imaging of the PA (Fig 2). The origin, anatomic course, and attachment of the peroneal component of the PA were depicted in great detail (Fig 9), although visualization of the bifurcation of the peroneal component into the medial and lateral crux was not feasible.



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  		Figure 9a. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Prescribed sagittal lateral oblique T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 13-cm field of view). (b) Corresponding anatomic slice. C = calcaneus, CU = cuboid bone, M5 = fifth metatarsal bone, PAL = PA lateral component (arrows); 1 = peroneus brevis tendon, 2 = peroneus longus tendon, 3 = abductor digiti minimi muscle, 4 = flexor digiti minimi brevis muscle.

 


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  		Figure 9b. Correlation of MR imaging with gross anatomic findings in the cadaveric PA and perifascial tissues. (a) Prescribed sagittal lateral oblique T1-weighted SE MR image (600/22, 512 x 256 matrix, two signals acquired, 13-cm field of view). (b) Corresponding anatomic slice. C = calcaneus, CU = cuboid bone, M5 = fifth metatarsal bone, PAL = PA lateral component (arrows); 1 = peroneus brevis tendon, 2 = peroneus longus tendon, 3 = abductor digiti minimi muscle, 4 = flexor digiti minimi brevis muscle.

 
Clinical Study
The MR imaging features of ruptures of the PA and plantar fasciitis in our 26 clinical cases are listed in the Table (Figs 10–14). MR imaging criteria in 14 patients with full thickness (n = 9) or partial thickness (n = 5) tears of the PA were abnormal absence of T1-weighted low signal intensity of the PA at the site of complete rupture (Figs 10, 11) or partial loss of T1-weighted low signal intensity (Fig 13), respectively. In all patients, abnormal thickening of the PA at the site of disruption (either complete or partial) was evident. Tears involved the proximal PA in seven cases and the middle PA in seven. Six of the tears were acute, occurring after an episode of trauma to the foot, and eight were chronic. In two of our patients, prior plantar fasciitis was treated with local steroid injections. In our six cases of acute rupture of the PA, prominent edema in perifascial soft tissue was depicted with high signal intensity on T2-weighted images (Figs 10, 11, 14). In our eight cases of chronic rupture of the PA, scar tissue was depicted with low signal intensity on T1-weighted, T2-weighted, and STIR images (Fig 14). Six of the 14 patients with rupture of the PA underwent gadolinium-enhanced T1-weighted imaging; remarkable perifascial contrast enhancement was depicted in the five cases of acute rupture (Figs 10, 13).


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  		MR Imaging Findings in 26 Patients with Plantar Fasciitis and Fascial Rupture
 


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  		Figure 10a. Acute complete rupture of the PA at the enthesis because of sudden pivot shifting in a 25-year-old female jumper. (a) Sagittal T1-weighted SE MR image (400/12) shows rupture of the plantar fascia at the enthesis (straight arrow), fraying of the free fascial end (curved arrow), and abnormal intermediate signal intensity in subcutaneous soft tissues (open arrow) consistent with edema. (b) Sagittal gradient-echo MR image (620/25, 25° flip angle) shows rupture of the plantar fascia at the enthesis (straight arrow), abnormal high signal intensity at the loose end of the ruptured PA (curved arrow), and edema in perifascial soft tissues (arrowheads). (c) Coronal T1-weighted SE gadolinium-enhanced MR image (520/12) shows abnormal contrast enhancement of the plantar fascia and surrounding soft tissues at the site of rupture (arrows).

 


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  		Figure 10b. Acute complete rupture of the PA at the enthesis because of sudden pivot shifting in a 25-year-old female jumper. (a) Sagittal T1-weighted SE MR image (400/12) shows rupture of the plantar fascia at the enthesis (straight arrow), fraying of the free fascial end (curved arrow), and abnormal intermediate signal intensity in subcutaneous soft tissues (open arrow) consistent with edema. (b) Sagittal gradient-echo MR image (620/25, 25° flip angle) shows rupture of the plantar fascia at the enthesis (straight arrow), abnormal high signal intensity at the loose end of the ruptured PA (curved arrow), and edema in perifascial soft tissues (arrowheads). (c) Coronal T1-weighted SE gadolinium-enhanced MR image (520/12) shows abnormal contrast enhancement of the plantar fascia and surrounding soft tissues at the site of rupture (arrows).

 


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  		Figure 10c. Acute complete rupture of the PA at the enthesis because of sudden pivot shifting in a 25-year-old female jumper. (a) Sagittal T1-weighted SE MR image (400/12) shows rupture of the plantar fascia at the enthesis (straight arrow), fraying of the free fascial end (curved arrow), and abnormal intermediate signal intensity in subcutaneous soft tissues (open arrow) consistent with edema. (b) Sagittal gradient-echo MR image (620/25, 25° flip angle) shows rupture of the plantar fascia at the enthesis (straight arrow), abnormal high signal intensity at the loose end of the ruptured PA (curved arrow), and edema in perifascial soft tissues (arrowheads). (c) Coronal T1-weighted SE gadolinium-enhanced MR image (520/12) shows abnormal contrast enhancement of the plantar fascia and surrounding soft tissues at the site of rupture (arrows).

 


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  		Figure 11a. Acute complete rupture of the PA in a 52-year-old female runner. (a) Sagittal T1-weighted SE MR image (850/16) shows discontinuity of the plantar fascia (straight arrow) with fraying of the free ends and abnormal low signal intensity superficial to the PA (curved arrow) consistent with edema at subcutaneous fat tissue. (b) Sagittal STIR MR image (4,389/60/150) shows rupture of the plantar fascia (curved arrow), focal fusiform thickening at the site of rupture, and high signal intensity infiltrating soft tissues both superficial and deep to the PA (straight arrows). (c) Coronal fat-suppressed intermediate-weighted fast SE MR image (2,200/23) shows abnormal intermediate signal intensity within the central component of the PA (arrows) consistent with a complete rupture.

 


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  		Figure 11b. Acute complete rupture of the PA in a 52-year-old female runner. (a) Sagittal T1-weighted SE MR image (850/16) shows discontinuity of the plantar fascia (straight arrow) with fraying of the free ends and abnormal low signal intensity superficial to the PA (curved arrow) consistent with edema at subcutaneous fat tissue. (b) Sagittal STIR MR image (4,389/60/150) shows rupture of the plantar fascia (curved arrow), focal fusiform thickening at the site of rupture, and high signal intensity infiltrating soft tissues both superficial and deep to the PA (straight arrows). (c) Coronal fat-suppressed intermediate-weighted fast SE MR image (2,200/23) shows abnormal intermediate signal intensity within the central component of the PA (arrows) consistent with a complete rupture.

 


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  		Figure 11c. Acute complete rupture of the PA in a 52-year-old female runner. (a) Sagittal T1-weighted SE MR image (850/16) shows discontinuity of the plantar fascia (straight arrow) with fraying of the free ends and abnormal low signal intensity superficial to the PA (curved arrow) consistent with edema at subcutaneous fat tissue. (b) Sagittal STIR MR image (4,389/60/150) shows rupture of the plantar fascia (curved arrow), focal fusiform thickening at the site of rupture, and high signal intensity infiltrating soft tissues both superficial and deep to the PA (straight arrows). (c) Coronal fat-suppressed intermediate-weighted fast SE MR image (2,200/23) shows abnormal intermediate signal intensity within the central component of the PA (arrows) consistent with a complete rupture.

 


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  		Figure 12a. Chronic complete rupture of the PA in a 31-year-old male basketball player. (a) Sagittal T1-weighted SE MR image (360/13) of the foot demonstrates complete rupture of the plantar fascia at the junction (arrows) of its proximal and middle thirds. (b) Sagittal gradient-echo MR image (360/20, 25° flip angle) displays abnormal high signal intensity at the junction (arrow) of the proximal and middle thirds of the PA and mild surrounding soft-tissue edema. (c) Sagittal T1-weighted SE gadolinium-enhanced MR image (360/13) reveals contrast enhancement at the site of fascial rupture (arrow). Note absence of remarkable perifascial soft-tissue enhancement.

 


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  		Figure 12b. Chronic complete rupture of the PA in a 31-year-old male basketball player. (a) Sagittal T1-weighted SE MR image (360/13) of the foot demonstrates complete rupture of the plantar fascia at the junction (arrows) of its proximal and middle thirds. (b) Sagittal gradient-echo MR image (360/20, 25° flip angle) displays abnormal high signal intensity at the junction (arrow) of the proximal and middle thirds of the PA and mild surrounding soft-tissue edema. (c) Sagittal T1-weighted SE gadolinium-enhanced MR image (360/13) reveals contrast enhancement at the site of fascial rupture (arrow). Note absence of remarkable perifascial soft-tissue enhancement.

 


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  		Figure 12c. Chronic complete rupture of the PA in a 31-year-old male basketball player. (a) Sagittal T1-weighted SE MR image (360/13) of the foot demonstrates complete rupture of the plantar fascia at the junction (arrows) of its proximal and middle thirds. (b) Sagittal gradient-echo MR image (360/20, 25° flip angle) displays abnormal high signal intensity at the junction (arrow) of the proximal and middle thirds of the PA and mild surrounding soft-tissue edema. (c) Sagittal T1-weighted SE gadolinium-enhanced MR image (360/13) reveals contrast enhancement at the site of fascial rupture (arrow). Note absence of remarkable perifascial soft-tissue enhancement.

 


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  		Figure 13a. Recent extensive, almost complete rupture of the PA in a 23-year-old woman with chronic plantar fasciitis. (a) Sagittal T1-weighted SE MR image (400/12) demonstrates an area of abnormal intermediate signal intensity at the junction (arrows) of the proximal and middle thirds of the thickened PA. (b) Sagittal gradient-echo MR image (620/25, 25° flip angle) shows fusiform thickening of the plantar fascia and abnormal intrafascial and perifascial high signal intensity consistent with edema at the site of rupture (arrows). (c) Coronal T1-weighted SE gadolinium-enhanced MR image (610/12) displays intrafascial (curved arrow) and perifascial (arrow) contrast enhancement at the site of rupture of the PA.

 


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  		Figure 13b. Recent extensive, almost complete rupture of the PA in a 23-year-old woman with chronic plantar fasciitis. (a) Sagittal T1-weighted SE MR image (400/12) demonstrates an area of abnormal intermediate signal intensity at the junction (arrows) of the proximal and middle thirds of the thickened PA. (b) Sagittal gradient-echo MR image (620/25, 25° flip angle) shows fusiform thickening of the plantar fascia and abnormal intrafascial and perifascial high signal intensity consistent with edema at the site of rupture (arrows). (c) Coronal T1-weighted SE gadolinium-enhanced MR image (610/12) displays intrafascial (curved arrow) and perifascial (arrow) contrast enhancement at the site of rupture of the PA.

 


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  		Figure 13c. Recent extensive, almost complete rupture of the PA in a 23-year-old woman with chronic plantar fasciitis. (a) Sagittal T1-weighted SE MR image (400/12) demonstrates an area of abnormal intermediate signal intensity at the junction (arrows) of the proximal and middle thirds of the thickened PA. (b) Sagittal gradient-echo MR image (620/25, 25° flip angle) shows fusiform thickening of the plantar fascia and abnormal intrafascial and perifascial high signal intensity consistent with edema at the site of rupture (arrows). (c) Coronal T1-weighted SE gadolinium-enhanced MR image (610/12) displays intrafascial (curved arrow) and perifascial (arrow) contrast enhancement at the site of rupture of the PA.

 


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  		Figure 14a. Chronic incomplete rupture of the PA in a 45-year-old female runner. (a) Sagittal T1-weighted SE MR image (400/12) shows fusiform thickening of the middle portion of the PA (arrow). (b) Sagittal gradient-echo MR image (560/25, 25° flip angle) shows focal fusiform thickening of the PA with a region of abnormal intrafascial high signal intensity (solid straight arrow) and edema infiltrating soft tissues superficial to the PA (curved arrow). Note that there is also a fine lining of high signal intensity (open arrows) consistent with mild edematous infiltration of soft tissue deep to the plantar fascia. (c) Coronal T1-weighted SE gadolinium-enhanced MR image (560/12) depicts fusiform thickening of the PA (small arrows). Note foci of intrafascial abnormal high signal intensity (large arrow).

 


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  		Figure 14b. Chronic incomplete rupture of the PA in a 45-year-old female runner. (a) Sagittal T1-weighted SE MR image (400/12) shows fusiform thickening of the middle portion of the PA (arrow). (b) Sagittal gradient-echo MR image (560/25, 25° flip angle) shows focal fusiform thickening of the PA with a region of abnormal intrafascial high signal intensity (solid straight arrow) and edema infiltrating soft tissues superficial to the PA (curved arrow). Note that there is also a fine lining of high signal intensity (open arrows) consistent with mild edematous infiltration of soft tissue deep to the plantar fascia. (c) Coronal T1-weighted SE gadolinium-enhanced MR image (560/12) depicts fusiform thickening of the PA (small arrows). Note foci of intrafascial abnormal high signal intensity (large arrow).

 


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  		Figure 14c. Chronic incomplete rupture of the PA in a 45-year-old female runner. (a) Sagittal T1-weighted SE MR image (400/12) shows fusiform thickening of the middle portion of the PA (arrow). (b) Sagittal gradient-echo MR image (560/25, 25° flip angle) shows focal fusiform thickening of the PA with a region of abnormal intrafascial high signal intensity (solid straight arrow) and edema infiltrating soft tissues superficial to the PA (curved arrow). Note that there is also a fine lining of high signal intensity (open arrows) consistent with mild edematous infiltration of soft tissue deep to the plantar fascia. (c) Coronal T1-weighted SE gadolinium-enhanced MR image (560/12) depicts fusiform thickening of the PA (small arrows). Note foci of intrafascial abnormal high signal intensity (large arrow).

 
MR imaging studies in the 12 patients with acute (n = 2) or chronic (n = 10) symptoms of plantar fasciitis revealed the signal intensity changes of perifascial edema either superficial to (n = 4) or both superficial and deep to (n = 8) the PA (Figs 15, 16). In four patients, the PA displayed abnormal intrafascial high signal intensity on T2-weighted images, STIR images, or both (Fig 15). The PA was abnormally thickened (5–7 mm) in seven patients. At MR imaging, marrow edema at the calcaneal insertion of the PA was evident in two patients. In three of the 10 patients with chronic plantar fasciitis, MR imaging revealed a calcaneal enthesophyte. Two patients with acute plantar fasciitis underwent gadolinium-enhanced T1-weighted imaging that depicted considerable contrast enhancement of the plantar fascia and perifascial soft tissue.



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  		Figure 15a. Acute plantar fasciitis in a 37-year-old woman with heel pain exacerbated while walking. (a) Sagittal T1-weighted SE (750/12) MR image shows thickened PA (straight arrows) and extensive low signal intensity in the adjacent heel fat pad (curved arrows) consistent with edema. (b) Sagittal fat-suppressed T2-weighted fast SE MR image (4,394/71) reveals thickened PA (solid straight arrows) with intrasubstance abnormal increased signal intensity (open arrow) and widespread abnormal high signal intensity (edema) infiltrating perifascial soft tissues (curved arrows). (c) Coronal STIR MR image (3,000/34/150) shows irregular thickened PA (short straight arrows) with intrasubstance foci of abnormal high signal intensity (long straight arrow). Extensive perifascial increased signal intensity (curved arrows) corresponds to soft-tissue edema.

 


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  		Figure 15b. Acute plantar fasciitis in a 37-year-old woman with heel pain exacerbated while walking. (a) Sagittal T1-weighted SE (750/12) MR image shows thickened PA (straight arrows) and extensive low signal intensity in the adjacent heel fat pad (curved arrows) consistent with edema. (b) Sagittal fat-suppressed T2-weighted fast SE MR image (4,394/71) reveals thickened PA (solid straight arrows) with intrasubstance abnormal increased signal intensity (open arrow) and widespread abnormal high signal intensity (edema) infiltrating perifascial soft tissues (curved arrows). (c) Coronal STIR MR image (3,000/34/150) shows irregular thickened PA (short straight arrows) with intrasubstance foci of abnormal high signal intensity (long straight arrow). Extensive perifascial increased signal intensity (curved arrows) corresponds to soft-tissue edema.

 


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  		Figure 15c. Acute plantar fasciitis in a 37-year-old woman with heel pain exacerbated while walking. (a) Sagittal T1-weighted SE (750/12) MR image shows thickened PA (straight arrows) and extensive low signal intensity in the adjacent heel fat pad (curved arrows) consistent with edema. (b) Sagittal fat-suppressed T2-weighted fast SE MR image (4,394/71) reveals thickened PA (solid straight arrows) with intrasubstance abnormal increased signal intensity (open arrow) and widespread abnormal high signal intensity (edema) infiltrating perifascial soft tissues (curved arrows). (c) Coronal STIR MR image (3,000/34/150) shows irregular thickened PA (short straight arrows) with intrasubstance foci of abnormal high signal intensity (long straight arrow). Extensive perifascial increased signal intensity (curved arrows) corresponds to soft-tissue edema.

 


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  		Figure 16a. Chronic plantar fasciitis in a 65-year-old woman with subcalcaneal heel pain. (a) Sagittal gradient-echo MR image (620/25, 25° flip angle) reveals soft-tissue edema both superficial and deep to the proximal third of the plantar fascia (arrows). (b) Sagittal T1-weighted SE MR image (440/12) appears unremarkable. (c) Sagittal T1-weighted SE gadolinium-enhanced MR image (420/12) also shows lack of inflammation in the plantar fascia and perifascial soft tissues.

 


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  		Figure 16b. Chronic plantar fasciitis in a 65-year-old woman with subcalcaneal heel pain. (a) Sagittal gradient-echo MR image (620/25, 25° flip angle) reveals soft-tissue edema both superficial and deep to the proximal third of the plantar fascia (arrows). (b) Sagittal T1-weighted SE MR image (440/12) appears unremarkable. (c) Sagittal T1-weighted SE gadolinium-enhanced MR image (420/12) also shows lack of inflammation in the plantar fascia and perifascial soft tissues.

 


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  		Figure 16c. Chronic plantar fasciitis in a 65-year-old woman with subcalcaneal heel pain. (a) Sagittal gradient-echo MR image (620/25, 25° flip angle) reveals soft-tissue edema both superficial and deep to the proximal third of the plantar fascia (arrows). (b) Sagittal T1-weighted SE MR image (440/12) appears unremarkable. (c) Sagittal T1-weighted SE gadolinium-enhanced MR image (420/12) also shows lack of inflammation in the plantar fascia and perifascial soft tissues.

 

   Discussion
Top
 Abstract
 Introduction
 Anatomic Considerations
 Materials and Methods
 Results
 Discussion
References
 
Several pathologic conditions may affect the PA. It can be a target site for inflammatory disorders such as acute or chronic plantar fasciitis, especially in athletes and active persons (6,8,9). The PA also may be affected by various rheumatologic processes (29), plantar fascia neuromas (30), or fibromatosis (19,31). Rupture of the PA is associated with injuries (8,32) and treatment with local corticosteroid injections (10). Postoperative pathologic conditions (eg, infection) and postsurgical changes are also included in the broad spectrum of abnormalities involving the PA.

Although significant anatomic studies (21,23,33) and biomechanical analyses (34,35) have described the particular structure and function of the PA and have addressed its role in both stability and maintenance of the arch of the foot, little emphasis has been placed on the imaging features of this structure. Owing to the limited contrast resolution, conventional radiography is often inadequate in the diagnosis of a pathologic condition affecting the PA. Findings at US (13,14) and radionuclide studies (11,12) have been reported as helpful in the assessment of disorders of the PA. Although findings in previous studies (15–19) have suggested the use of MR imaging in the evaluation of disorders of the PA, the MR imaging abnormalities in diseases of the PA have not been adequately defined.

In our cadaveric study, results derived from close correlation of MR images and anatomic slices indicate that the anatomy of the PA and the perifascial tissue can be demonstrated in great detail with MR imaging. MR images obtained in at least three orthogonal planes provide optimal characterization of the complex soft-tissue anatomy. All three components of the PA are best delineated with thin-section imaging in the coronal plane. Thin-section imaging may also be necessary to display abnormalities of the delicate neurovascular structures of the heel, but we did not include this investigation in our study. Depiction of the attachment of the PA to the calcaneus, especially of the portion of the PA about its origin, is the most critical diagnostic consideration in cases of plantar fasciitis, as opposed to plantar fibromatosis, which usually does not involve the calcaneal attachment (36). The calcaneal attachment of the PA is partially demonstrated on transverse images, well demonstrated on sagittal images, and best demonstrated on coronal images. The PA is best demonstrated in its entirety in the sagittal plane, which allowed global assessment of the anatomic course, integrity, and intimate relationship of the PA with the perifascial soft tissues. The lateral component of the PA can be evaluated best on prescribed oblique images, although it can also be seen on coronal and sagittal images. The medial component of the PA is well demonstrated on coronal and sagittal images.

Single images viewed in the transverse and coronal planes simultaneously demonstrate the abductor digiti minimi, flexor digitorum brevis, and abductor hallucis muscles as a muscular group, and individual sagittal images also show portions of these muscles. The abductor digiti minimi muscle is best delineated in the prescribed oblique imaging plane.

All the ligaments, musculotendinous units, and intrinsic muscles of the foot surrounding the PA can also be recognized with conventional MR imaging sequences. The long plantar ligament is identified on coronal, transverse, and sagittal images, although the sagittal plane is the most appropriate for demonstrating the extent of the ligament. Transverse images, however, provide optimal assessment of the calcaneal attachment of the long plantar ligament. Diagnostically important fine structures in the pathogenesis of heel pain, such as the medial and lateral plantar nerves (4,7,37,38), may necessitate use of high-spatial-resolution MR imaging sequences.

MR imaging also provides accurate assessment of the biomechanical properties of the PA as related to the "windlass mechanism" described by Hicks (35). In the initial description of this mechanism, Hicks introduced the concept that passive extension of the proximal phalanx tightens the PA, but this particular function fails when the PA is sliced. In our cadaveric specimens, observation of the elastic properties of the PA was possible in the sagittal and coronal planes during application of dynamic stress to the foot. Our images were obtained in cadavers, however, so that motion artifacts were eliminated. These results are promising with regard to the potential of MR imaging in assessment of traumatic injuries, postsurgical changes, and nontraumatic disorders affecting the PA. In addition, the capability of MR imaging to allow direct evaluation of supporting structures about the PA suggests an important role in the evaluation of injuries about the PA.

In our patients with a clinical diagnosis of rupture of the PA, MR imaging allowed demonstration, exact localization, and determination of severity of the lesion with regard to the proportionate thickness of the affected PA. By demonstrating the presence and extent of edema, MR imaging helped distinguish between recent and long-standing rupture of the PA.

Detailed diagnostic information provided at MR imaging helps elucidate implications of treatment in the clinical context of subcalcaneal heel pain. Conservative treatment of fascial rupture consists of restriction of physical activity, anti-inflammatory medications, and orthotic devices. Surgical release of the PA may be required if conservative treatment fails, refractory symptoms recur, or participation in active sports is desired within a short time (8,10,32,39).

In all our patients suspected of having plantar fasciitis, increased signal intensity consistent with edema in the perifascial soft tissue was depicted on T2-weighted images. Our findings are in agreement with those of a previous study (40), in which perifascial edema was considered to be the most common manifestation of plantar fasciitis. In our patients with chronic plantar fasciitis, soft-tissue edema both superficial and deep to the PA was the dominant abnormal imaging finding in 70% of cases, although a higher frequency for edema superficial to the PA was reported previously (40). The second most common MR imaging finding of plantar fasciitis, seen in 58% of our patient population, was mild to moderate thickening of the PA, which presumably corresponded to the presence of granulation tissue. This particular finding was more common in our study than was previously reported (40). The third most common MR imaging finding of plantar fasciitis, observed in 33% of our cases, was increased signal intensity within the involved plantar fascia on T2-weighted and STIR images; this finding presumably was consistent with edema and intrasubstance microtears. Although this pattern of signal intensity changes was less common in our study than was previously reported (40), we believe that the discrepancy is related to suboptimal sensitivity of conventional SE pulse sequences available in our retrospective study (in contradistinction to the most fluid-sensitive STIR sequences that are currently in use) to depict areas of intrasubstance edema. Finally, the least common MR imaging finding of plantar fasciitis, observed in 17% of patients, was calcaneal marrow edema. This MR imaging finding is dissimilar to the changes described at the enthesis of the plantar fascia in a previous study (40), in which bone marrow abnormality was found to be the second most common MR imaging feature of plantar fasciitis. In our series, however, as previously (40), calcaneal marrow edema was observed in patients with chronic plantar fasciitis.

In clinical terms, consideration of differential imaging features between acute and chronic plantar fasciitis may have a sound contribution in patient treatment. Management of plantar fasciitis is primarily conservative, consisting of restriction of physical activity and treatment with physical therapy, nonsteroidal antiinflammatory medications, heel pads, and night splints. Steroid injections and surgical release of the PA are therapeutic options reserved for chronic, recalcitrant cases of plantar fasciitis (37,38).

We recognize that our clinical study has some limitations. Although all patients had similar clinical presentations and imaging findings, study of a larger series would allow a more comprehensive evaluation of the significance of our conclusions. Also, our clinical study was retrospective with an inherent selection bias that did not allow assessment of the frequency with which plantar fasciitis and rupture affect patients with subcalcaneal heel pain. Consequently, we did not advocate use of the same imaging protocol in our clinical cases as in our cadaveric specimens. Furthermore, surgical and histopathologic proof of the imaging findings were not available in our series, so a true standard of reference was not available. As most cases of plantar fasciitis and rupture are treated conservatively, however, the lack of pathologic confirmation is unavoidable. We used a consensus opinion of two radiologists who reviewed MR images simultaneously and, therefore, we have no data regarding interobserver disagreement in either the cadaveric or clinical cases. Finally, we did not use an oblique imaging plane to evaluate the tibial component of the PA in our cadaveric specimens, although it is the central component of the PA that is of biomechanical and clinical importance (15,21). Instead, we emphasized imaging evaluation of the peroneal component of the PA as this component may be involved in injuries of the lateral aspect of the hindfoot and midfoot.

In conclusion, MR imaging helped delineate the anatomy of the PA and perifascial tissue including musculotendinous, ligamentous, neuromuscular, and osseous structures in our cadaveric specimens and patients. Since detailed depiction of anatomy may allow precise localization and definition of the extent of pathologic processes involving the PA and perifascial structures, we believe our results may be of clinical importance. In our clinical practice, the superior contrast discrimination and multiplanar imaging capabilities provided by MR imaging are particularly helpful in limiting the broad differential diagnosis of causes of plantar heel pain, including plantar fasciitis, fascial rupture, infections, tumors, nerve entrapment syndromes, and calcaneal stress fractures.


   Acknowledgments
 
The authors appreciate the technical assistance provided by Debra Trudell, RA.


   Footnotes
 
Abbreviations: PA = plantar aponeurosis, SE = spin-echo, STIR = short inversion time inversion-recovery


   References
Top
 Abstract
 Introduction
 Anatomic Considerations
 Materials and Methods
 Results
 Discussion
 References
 

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