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1 Downloaded from by on 01/07/18 from IP address opyright RRS. For personal use only; all rights reserved Disorders of the Plantar poneurosis: Spectrum of MR Imaging Findings Daphne J. Theodorou 1, Stavroula J. Theodorou, Shella Farooki, Y. Kakitsubata, Donald Resnick T he plantar aponeurosis, or plantar fascia, has received considerable attention in the scientific literature and has been shown to be the most important structure for dynamic longitudinal arch support in the foot [1]. The plantar aponeurosis comprises histologically both collagen and elastic fibers arranged in a particular network of bundles and is a tough tendinous (rather than a fascial) layer of the plantar aspect of the foot. This sophisticated combination of fibers, having different biomechanical properties during stress application to the plantar aponeurosis, affords an increased modulus of elasticity during weight bearing [2]. bnormalities affecting the plantar aponeurosis are well recognized. Patients with suspected abnormality involving the aponeurosis traditionally have been examined with conventional radiography and bone scintigraphy and occasionally with sonography. lthough conventional radiography remains essential in the initial diagnostic approach, MR imaging is particularly well Pictorial Review suited for depicting the plantar aponeurosis (Fig. 1) and for detecting the presence of a wide range of disorders. MR imaging also may be useful in limiting the broad differential diagnosis of subcalcaneal heel pain. This pictorial review summarizes the most common abnormalities that affect the plantar aponeurosis and addresses their characteristic MR imaging features. lthough in clinical practice plantar fasciitis is the most common diagnosis in patients with heel pain, a spectrum of disorders may also affect the Fig. 1. MR imaging configuration of normal plantar aponeurosis with anatomic correlation., In cadaveric specimen, sagittal T1-weighted spin-echo MR image (TR/TE, 600/20) outlines plantar aponeurosis as uniform bandlike structure of low signal intensity (arrows)., natomic section, approximately 8 mm more laterally to mid-sagittal level than MR image, delineates central component of plantar aponeurosis (arrows). Received March 13, 2000; accepted after revision June 20, Supported by Veterans dministration grant S-360 and the. S. Onassis Public enefit Foundation Educational Stipend U ll authors: Department of Radiology, School of Medicine, University of alifornia San Diego and Veterans dministration Medical enter, 3350 La Jolla Village Dr., San Diego, ddress correspondence to D. Resnick. JR 2001;176: X/01/ merican Roentgen Ray Society JR:176, January

2 Theodorou et al. Downloaded from by on 01/07/18 from IP address opyright RRS. For personal use only; all rights reserved plantar aponeurosis, including enthesopathy, traumatic and corticosteroid-induced rupture, rheumatologic and infectious processes, and plantar fibromatosis. Fig. 2. cute plantar fasciitis in 42-year-old man with subcalcaneal pain. (ourtesy of Skaf, Sao Paolo, razil) and, Unenhanced T1-weighted spin-echo MR image (TR/TE, 620/25) () and short tau inversion-recovery (STIR) MR image (3760/16; inversion time,150 msec) () show thickening of central component of plantar aponeurosis (large arrows ). Extensive edema infiltrates perifascial soft tissue (curved arrows). Note abnormal foci of intrafascial high signal intensity corresponding to intrasubstance edema because of acute inflammation evident on STIR image (small arrows)., T2-weighted fast spin-echo MR image (4367/86) with fat saturation shows thickening of plantar fascia (straight arrows), extensive high signal intensity infiltrating perifascial soft tissues (curved arrows), and abnormal intermediate intrafascial signal intensity. Plantar Fasciitis Plantar fasciitis, the most common cause of heel pain in the athlete, is a low-grade inflammation involving the plantar aponeurosis and the perifascial structures. ffecting a wide range of age groups, it is a relatively common disorder that is characterized by chronic deep pain in the subcalcaneal area and along the medial aspect of the plantar surface of the foot. In general, the factors associated with plantar fasciitis fall into three major categories [3]: mechanical, degenerative, and systemic. Mechanical causes of plantar fasciitis include overuse syndromes (participation in competitive sports involving repetitive application of tension force to the aponeurosis), various foot deformities, tight chilles tendon or limited dorsiflexion, increased body weight, leg length inequality, and externally rotated lower extremity. Degenerative factors associated with plantar fasciitis include age-related increases in foot pronation and atrophy of the heel fat pad. Predisposing systemic factors include various rheumatoid disorders, especially rheumatoid arthritis, seronegative spondyloarthropathies, and gout [3]. Repetitive trauma produces microtears of some fibers of the plantar aponeurosis, mostly close to the site of its attachment, that are accompanied by a local inflammatory reaction. cute plantar fasciitis may be displayed conspicuously with MR imaging. The inflamed plantar aponeurosis may show abnormal high intrasubstance signal intensity on T2-weighted and short tau inversion-recovery (STIR) MR images, with or without associated fascial thickening (Fig. 2). The signal-intensity changes of perifascial soft-tissue edema either deep, superficial, or both deep and superficial in relation to the plantar aponeurosis are revealed. Marrow edema of the calcaneus also may be observed. fter administration of gadolinium-containing contrast material, ample enhancement of the inflamed perifascial soft tissues may be seen (Fig. 3). With chronicity, the plantar aponeurosis may show significant fusiform thickening extending to its calcaneal origin. Erosive changes of the calcaneus also may occur as a result of chronic inflammation at the osseotendinous junction. hronic inflammation of the aponeurosis and the perifascial structures is characterized by collagen degeneration and necrosis, angiofibroblastic 98 JR:176, January 2001

3 MR Imaging of the Plantar poneurosis Downloaded from by on 01/07/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 3. MR imaging findings of acute plantar fasciitis in 23-year-old male athlete. (ourtesy of Skaf, Sao Paolo, razil) and, Unenhanced T1-weighted spin-echo MR image (TR/TE, 400/10) () and enhanced T2-weighted fat-suppressed fast spin-echo MR image (4000/105) () show the signal-intensity changes of edema in perifascial soft tissues (straight arrows). Note foci of abnormal marrow high signal intensity at calcaneal insertion of plantar fascia (curved arrows), evident on fast spin-echo T2- weighted MR image ()., Short tau inversion-recovery MR image (TR/TE, 3000/ 48; inversion time,150 msec) again reveals prominent abnormal high signal intensity in perifascial soft tissues consistent with edema (arrows). Fig. 4. hronic plantar fasciitis in 42-year-old woman. (ourtesy of Kerr R, Los ngeles, ) and, Unenhanced T1-weighted spin-echo MR image (TR/TE, 720/12) () and enhanced T1-weighted fat-suppressed spin-echo MR image (610/12) () display abnormal intermediate and high signal intensity, respectively, in soft tissues superficial to plantar aponeurosis (solid arrows). ontrast enhancement of soft tissues deep in relation to plantar aponeurosis (open arrows) because of edema also can be appreciated. JR:176, January

4 Theodorou et al. Downloaded from by on 01/07/18 from IP address opyright RRS. For personal use only; all rights reserved hyperplasia, chondroid metaplasia, and matrix calcification. On MR imaging, these histopathologic changes may correspond to abnormal intrafascial intermediate signal intensity on T1- weighted MR images and high signal intensity on T2-weighted and STIR MR images. On T2- weighted and STIR images, however, areas of high signal intensity reflecting edema also may be shown in the marrow of the calcaneus and in the adjacent subcutaneous tissues. fter administration of gadolinium-containing contrast material, enhancement of the aponeurosis and the surrounding soft tissues may be evident (Fig. 4). In almost all patients, however, fluid-sensitive sequences are sufficient, and the use of IV gadolinium rarely is required. ecause the imaging findings of acute and chronic plantar fasciitis may be similar, accurate diagnosis requires adequate clinical information. In the correct clinical circumstances, MR imaging may be of particular value in differentiating plantar fasciitis from other causes of plantar heel pain, including fascial strain or rupture, infections, tumors, tendinosis and tenosynovitis, subcalcaneal bursitis, nerve entrapment syndromes, and calcaneal stress fractures [3]. alcaneal Enthesophyte Plantar calcaneal enthesophytes originate from the medial calcaneal tuberosity at the attachment of the flexor digitorum brevis and abductor hallucis muscles. s with enthesophytes at other sites, calcaneal enthesophytes may occur as a result of excessive repetitive traction by these intrinsic muscles, causing chronic microtrauma, which in turn, leads to periostitis and calcification. Systemic arthritis with reactive bone proliferation and the aging process may also be associated with the formation of calcaneal enthesophytes, which may become symptomatic in the setting of plantar heel pad atrophy. lthough calcaneal enthesophytes have been described in association with plantar fasciitis, most publications conclude that they rarely cause this condition as also indicated by erkowitz et al. [4], who found calcaneal enthesophytes in patients with plantar fasciitis, as well as in asymptomatic controls. MR imaging can display conspicuously calcaneal enthesophytes and may show abnormalities at the enthesis of the plantar aponeurosis in some patients in whom the outgrowths are associated with enthesitis [3] (Figs. 5 and 6). Fascial Rupture lthough plantar fasciitis is common, rupture of the plantar aponeurosis, either complete or partial, is not a commonly encountered diagnosis because it occurs infrequently or is not recognized. Most commonly seen in competitive athletes at the time of injury by an acceleration type of motion that leads to forcible plantar flexion, rupture of the plantar aponeurosis also may occur as a result of repetitive stress or repetitive minor trauma to the aponeurosis in recreational running and jumping. Spontaneous rupture of the plantar aponeurosis, however, may occur in patients with prior plantar fasciitis and most commonly in those patients treated with local steroid injections (Fig. 7). Research by cevedo and eskin [5] indicates a 10% plantar aponeurosis rupture rate after corticosteroid injection for plantar fasciitis. Regardless of the mechanism of rupture, MR imaging clearly reveals and localizes the lesion and aids in distinguishing recent and longstanding ruptures of the plantar aponeurosis. In many patients, MR imaging also may provide additional diagnostic information with regard to inflammatory changes of the heel fat pad, accompanying rupture. Recent rupture may be diagnosed when the aponeurosis shows disruption of its continuity with abnormal loss of its low signal intensity on T1-weighted MR images at the site of the complete rupture (Fig. 8) or when it shows partial loss of its low signal intensity with partial rupture (Fig. 9). Typically, the aponeurosis appears thickened at the site of partial disruption of its continuity. Soft tissues show abnormal high signal intensity on T2-weighted MR images because of edema or hemorrhage, or both, and show considerable enhancement after administration of gadolinium-containing contrast material. hronic rupture, however, is displayed as a scar of intermediate-to-low signal intensity on both T1- and T2-weighted MR images. This scar shows no enhancement after contrast administration. The plantar aponeurosis appears focally thickened, and chronic hematoma formation also Fig. 5. alcaneal enthesophyte in asymptomatic 53-year-old man., Lateral radiograph of heel shows calcaneal enthesophyte (arrow) with smooth margins and normal adjacent soft tissues., Unenhanced T1-weighted spin-echo MR image (TR/TE, 516/20) again shows calcaneal enthesophyte (curved arrow). Plantar aponeurosis (straight arrow ) and adjacent soft tissues appear unremarkable. Fig. 6. alcaneal enthesophyte in 51-year-old man with chronic heel pain. Gradient-echo MR image (TR/TE, 620/25; flip angle, 25 ) shows enthesophyte (curved arrow) and abnormal high signal intensity in soft tissues superficial to plantar aponeurosis consistent with edema (open arrow). (ourtesy of Roger, Paris, France) 100 JR:176, January 2001

5 MR Imaging of the Plantar poneurosis Downloaded from by on 01/07/18 from IP address opyright RRS. For personal use only; all rights reserved Fig year-old man with complete rupture of plantar aponeurosis after local corticosteroid injections for chronic plantar fasciitis., Lateral radiograph of foot shows calcaneal enthesophyte (curved arrow) with erosion of undersurface of calcaneus (straight arrows) and small bone fragment (open arrow)., Unenhanced T1-weighted fast spin-echo MR image (TR/TE, 466/12.6) of foot shows prominent pointed calcaneal enthesophyte (arrow)., Enhanced T1-weighted fat-suppressed fast spin-echo MR image (716/13.8) shows large osseous defect at plantar aspect of calcaneus (long arrow) and absence of plantar aponeurosis. Note remarkable enhancement of bone caused by marrow edema (short arrows). Soft-tissue edema also is evident (open arrow). may be seen (Fig. 10). On some occasions, secondary formation of a cyst is revealed as a welldefined collection of abnormal intermediate signal intensity on T1-weighted MR images and high signal intensity on T2-weighted images, located between the superficial and the deep layers of the aponeurosis. Rheumatoid Nodules mong pedal manifestations of rheumatoid arthritis, rheumatoid nodules are considered one of the most common soft-tissue lesions, occurring in 20 30% of instances of rheumatoid arthritis [6]. lthough rheumatoid nodules Fig. 8. Posttraumatic acute complete rupture of plantar aponeurosis in 48-year-old sheriff who was running after suspect. (ourtesy of Edwards J, Savannah, G) and, Unenhanced T1-weighted spin-echo (TR/TE, 760/20) () and short tau inversion-recovery (STIR) () MR images (5830/30; inversion time, 150 msec) display complete disruption of plantar aponeurosis with abnormal intermediate and high signal intensity, respectively, at proximal part of plantar aponeurosis (straight arrows). On STIR images, edema infiltrating perifascial soft tissues (open arrows) mostly deep in relation to plantar aponeurosis is evident. Signal-intensity changes of minimal bone marrow edema involving calcaneal enthesophyte also are present (curved arrows)., T2-weighted fat-suppressed fast spin-echo MR image (3901/98) shows area of abnormal high signal intensity in central component of plantar aponeurosis (arrows), corresponding to complete disruption of aponeurosis. have traditionally been associated with advanced rheumatoid arthritis and treatment with methotrexate, they also may occur in patients with rheumatic fever, ankylosing spondylitis, systemic lupus erythematosus, and agammaglobulinemia. These subcutaneous lesions are commonly found in areas that are subject to repetitive minor trauma and, specifically, in those areas overlying osseous prominences. Typically, rheumatoid nodules are revealed as subcutaneous focal demarcated nodular areas of fibroinflammatory reaction. With MR imaging, rheumatoid nodules usually appear nearly isointense to muscle in T1- weighted images and display slightly heterogeneous intermediate-to-high signal intensity in T2-weighted images. On enhanced MR images, rheumatoid nodules may reveal a spectrum of appearances, including areas of heterogeneous increased signal intensity, faint peripheral enhancement, or homogeneous enhancement in solid lesions with no central necrosis (Fig. 11). Plantar Infection s with infections at the plantar aspect of the foot in general, the plantar aponeurosis may be contaminated by direct implantation of foreign bodies, puncture wounds, surgical JR:176, January

6 Theodorou et al. Downloaded from by on 01/07/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 9. MR imaging findings of acute incomplete rupture of plantar aponeurosis in 38-year-old man. (ourtesy of Edwards J, Savannah, G) and, Short tau inversion-recovery MR image (TR/ TE, 5800/30; inversion time,150 msec) () and T2- weighted fast spin-echo MR image (3901/98) () show incomplete rupture of central component of plantar aponeurosis with abnormal intrafascial signal intensity (curved arrows) at junction of proximal and middle portion of plantar aponeurosis. Note fusiform thickening of plantar aponeurosis (straight arrows) and perifascial soft-tissue edema (open arrows). Fig. 10. hronic partial rupture of plantar aponeurosis in 42-year-old male jogger. (ourtesy of Roger, Paris, France) and, Unenhanced T1-weighted spin-echo (TR/TE, 400/13) () and gradient-echo MR images (340/20; flip angle, 25 ) () show fusiform thickening of plantar fascia (straight arrows) with abnormal intermediate () and high () intrafascial signal intensity (open arrows). Extensive edema infiltrating subcutaneous soft tissues can be seen (curved arrows)., Unenhanced T1-weighted MR image (400/13) reveals thickening of central component of plantar aponeurosis (thin arrows) and linear regions of intrafascial abnormal high signal intensity consistent with intrasubstance tear (arrowheads). Normal contralateral central component of plantar aponeurosis (thick arrow) is shown for comparison. 102 JR:176, January 2001

7 MR Imaging of the Plantar poneurosis Downloaded from by on 01/07/18 from IP address opyright RRS. For personal use only; all rights reserved Fig. 11. Rheumatoid nodule in 45-year-old woman with rheumatoid arthritis and swelling over plantar aspect of calcaneus. (ourtesy of Eilenberg S, San Diego, ) and, Unenhanced T1-weighted fast spin-echo MR image (TR/TE, 433/16) () and enhanced T1-weighted fat-suppressed fast spin-echo MR image (466/17) () show large lobulated soft-tissue mass of intermediate signal intensity located between skin and calcaneal tubercle (arrow). Note that underlying bone appears unremarkable. procedures, spread from a contiguous source of infection, and, in diabetic foot disease, via plantar skin ulceration and inoculation of infectious agents. variety of bacteria can cause infectious fasciitis, with Streptococci being most commonly reported. ecause fascial inflammation can cause destruction of mechanical barriers, spread of infection along the intermuscular fascial tissue planes to adjacent soft tissues, underlying bone, or both, may require amputation. Necrotizing fasciitis, however, is a rare type of pedal softtissue infection limited to the fascia only, and it is associated with generalized sepsis, endotoxic shock, and high mortality rates. Fig. 12. Local infection of plantar soft tissues in 43-year-old man with no known history of diabetes. (ourtesy of Roger, Paris, France), Unenhanced T1-weighted spin-echo MR image (TR/TE, 380/12) shows abnormal intermediate signal intensity in plantar aponeurosis and adjacent plantar soft tissues (arrows)., Enhanced T1-weighted spin-echo MR image (390/12) at same level as () shows diffuse enhancement of signal intensity in plantar aponeurosis and perifascial soft tissues (arrows ). MR imaging may be helpful in the early detection, localization, and determination of the depth of inflammation. Infectious fasciitis may be diagnosed when the plantar fascia and perifascial soft tissues show abnormal high signal intensity on T2-weighted MR images. It has been suggested [7] that high T2-weighted signal intensity in the deep fascial planes and muscles, along with rim enhancement after gadolinium administration, are specific findings for necrotizing fasciitis, whereas high signal intensity on T2-weighted MR images limited to the subcutaneous fat, with or without contrast enhancement, are findings consistent with nonnecrotizing soft-tissue infections (Fig. 12). However, it remains to be further investigated whether these MR imaging findings may allow differentiation between the two entities. Plantar Fibromatosis Superficial plantar fibromatosis is a benign fibroblastic proliferative disorder associated with replacement of elements of the plantar aponeurosis with abnormal fibrous tissue. lthough several etiologic factors have been proposed [8], including trauma, infection, neuropathy, biochemical and metabolic imbalance, faulty development, and the patient s occupation, the precise etiology of plantar JR:176, January

8 Theodorou et al. Downloaded from by on 01/07/18 from IP address opyright RRS. For personal use only; all rights reserved fibromatosis remains unclear. Typically, plantar fibromatosis is multinodular and occurs along the medial aspect of the central part of the plantar aponeurosis. Single or multiple plantar fibromas, usually measuring less than 3 cm in diameter, are located in the plantar aponeurosis and the subcutaneous tissues. With MR imaging, plantar fibromas appear as well-defined nodules with abnormal low signal intensity on T1-weighted and low-tointermediate signal intensity on T2-weighted MR images. In some instances associated with a more aggressive disorder, areas of abnormal high and low signal intensity on T2- weighted and STIR images reflect the relative proportions of cellular elements within the mass [8] (Fig. 13). With administration of gadolinium-containing contrast material, however, a spectrum of enhancement patterns Fig. 13. Solitary plantar fibroma in 64-year-old woman with palpable soft-tissue mass in sole of foot. (ourtesy of Taketa R, Long each, ), Unenhanced T1-weighted spin-echo MR image (TR/TE, 600/11) reveals large fusiform mass of intermediate signal intensity in plantar soft tissues (arrows). and, T2-weighted fat-suppressed fast spin-echo MR image (4900/46) () and enhanced T1-weighted spin-echo MR image (800/17) () show lobulated mass of high signal intensity with internal septation (open arrows) in continuity with plantar fascia (long arrows). Note distortion of contour in plantar aspect of foot. corresponding to the cellular portions of the lesion may be seen, varying from heterogeneously moderate or marked contrast enhancement to absolutely no enhancement. Local infiltrative growth associated with poor margination of the lesion and involvement of the subcutaneous tissue, muscles, or bones may be observed in aggressive or deep fibromatosis [8]. In deep fibromatosis, lesions are most commonly solitary and are characterized by a high recurrence rate. In summary, subcalcaneal heel pain is a common presenting complaint associated with a multitude of etiologic factors. The most common abnormalities are plantar fasciitis, calcaneal enthesopathy, fascial rupture, rheumatoid nodules, plantar infection, and plantar fibromatosis. MR imaging is particularly helpful for the diagnosis of these entities. References 1. Thordarson D, Schmotzer H, hon J, Peters J. Dynamic support of the human longitudinal arch: a biomechanical evaluation. lin Orthop 1995;316: Straub H. Die elastischen fasern in ändern des menschlichen Fuβes. cta nat ;11: Resnick D. bnormalities of the plantar soft tissues. In: Resnick D, ed. Diagnosis of bone and joint disorders. Philadelphia: Saunders, 1995: erkowitz J, Kier R, Rudicel S. Plantar fasciitis: MR imaging. Radiology 1991;179: cevedo J, eskin J. omplications of plantar fascia rupture associated with corticosteroid injection. Foot nkle Int 1998;19: Kaye R, Kaye PL, obrove. Rheumatoid nodules. m J Med 1984;76: Rahmouni. MR imaging in acute infectious cellulitis. Radiology 1994;192: Lee TH, Wapner KL, Hecht PJ. Plantar fibromatosis: current concepts review. J one Joint Surg m 1993;75-: JR:176, January 2001