Skeletal Radiol (2005) 34: 736–739 DOI 10.1007/s00256-005-0923-x
CASE REPORT
Srinivasan Harish Asif Saifuddin Stephen R. Cannon Adrienne M. Flanagan
Synovial chondromatosis of the foot presenting with Lisfranc dislocation
Received: 21 February 2005 Revised: 7 March 2005 Accepted: 7 March 2005 Published online: 1 July 2005 # ISS 2005
A. M. Flanagan Institute of Orthopaedics & Musculoskeletal Sciences, The Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex, HA7 4LP, UK
S. Harish . A. Saifuddin (*) Department of Radiology, The Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex, HA7 4LP, UK e-mail:
[email protected] Tel.: +44-20-89095443 Fax: +44-20-89095281 S. R. Cannon Department of Orthopaedic Surgery, The Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex, HA7 4LP, UK
Abstract Primary synovial chondromatosis is rare in the foot. We report a case of synovial chondromatosis affecting multiple sites of the foot and causing bone erosions in a 44-year-old woman. Radiographs demonstrated erosions of multiple metatarsals including the tarsometatarsal joints, resulting in Lisfranc tarsometatarsal dislocation. Magnetic resonance imaging showed the widespread
synovial proliferation and soft tissue masses affecting the foot and helped in arriving at a differential diagnosis and plan for needle biopsy. Diagnosis was made initially by needle biopsy under computed tomography guidance and was subsequently confirmed by histopathological assessment of the surgically excised synovial masses. To our knowledge, multifocal synovial chondromatosis causing Lisfranc dislocation in the foot has not been reported previously. Keywords Foot . Synovial chondromatosis . Lisfranc dislocation . Radiographs . MRI
Introduction
Case report
Synovial chondromatosis (SC) is a benign disorder of uncertain aetiology. It is not clear whether SC is a neoplastic or a reactive process, and chromosomal rearrangements have recently been documented to suggest that SC is a true neoplastic lesion [1]. The lesion shows chondroid nodules within synovial tissue in joints and/or associated with tendons. It is typically monoarticular, and large joints are most commonly involved, with the knee being the most common location [2]. SC usually occurs in the 3rd–5th decades of life, with a 2:1 male preponderance. There are only a few previous reports of SC occurring in the foot [3, 4]. Also, most reported cases describe involvement of a single joint within the foot. We describe a rare case of SC of the foot that involved multiple joints, resulting in a Lisfranc tarsometatarsal dislocation. The importance of magnetic resonance imaging (MRI) and needle biopsy in the preoperative evaluation is emphasised.
A 44-year-old woman of Afro-Caribbean origin presented with a history of pain and swelling of the left foot. She reported a gradual increase in the size of the swelling over the past 5 years, with a more rapid increase over the past 1 year. The pain prevented her from walking normally, and she had a sensation of forefoot instability. On examination, the overlying skin was normal. There was impression of a mass on the dorsum of the foot, but larger nodules were also palpated on the medial and lateral sides of the foot. The lateral side of the foot was exquisitely tender. Ankle movements were normal, and no neurovascular deficit was present. Radiographs performed at the referring hospital showed multiple large erosions in the tarsus and at the bases of the metatarsals (Fig. 1). There was displacement of the 2nd metatarsal, with lateral offset of the medial cortex of the 2nd metatarsal with respect to the medial cuneiform bone,
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Fig. 1 Initial radiograph of the left foot demonstrates erosions at the base of the 2nd–4th metatarsals (arrowheads) and displacement of the 2nd metatarsal, with lateral offset of the medial cortex of the 2nd metatarsal with respect to the medial cuneiform bone (white arrow).
Fig. 2 A, B Axial spin echo T1-weighted and sagittal STIR image of the foot demonstrate soft tissue nodules isointense to muscle on T1 and high signal intensity on STIR, causing erosive change in the cuneiform bones, cuboid, and bases of the metatarsals, including the 1st web space, at the expected position of the Lisfranc lig-
in keeping with Lisfranc tarsometatarsal dislocation. An MRI study of the left foot was performed. Axial and sagittal SE T1-weighted and STIR images of the left foot showed erosive change in the cuneiform bones, cuboid, and bases of the metatarsals (Fig. 2a,b). On T1-weighted images, the soft tissue masses were isointense to muscle, with heterogeneous high signal intensity on STIR images. The soft tissue appeared to interdigitate between the metatarsals (Fig. 2c). The initial diagnosis at the referring hospital was that of an erosive arthropathy or soft tissue sarcoma, and hence a referral was made to the bone and soft tissue tumour unit. Review of radiographs and MRI suggested a differential diagnosis of pigmented villonodular synovitis (PVNS) or SC, with chondrosarcoma considered less likely. Biopsy guided by computed tomography (CT) was done, and pathological assessment revealed tissue consisting of hyaline cartilage and showing a distinctive pattern of clonal proliferation. One core consisted of closely packed nodules, while another was covered at one margin by synovium (Fig. 3). A diagnosis of synovial chondromatosis was made. The patient subsequently underwent operative excision of the lesion. Given the extent of the lesion, a subtotal excision was performed, as complete excision was considered impossible. Histology postexcision confirmed the diagnosis of SC. The periphery of some nodules showed a greater degree of cellularity compared with the centre of the nodules, a find-
ament (arrow). The high signal intensity of the soft tissue nodules on STIR is consistent with a cartilaginous lesion. C Axial STIR image of the foot shows high signal intensity soft tissue nodules interdigitating between the metatarsals (arrows).
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Discussion
Fig. 3 Transmitted light microscopic image of a haematoxylin and eosin-stained section showing synovial tissue in which there are cartilaginous nodules composed of mature hyaline matrix. The nodules merge with surrounding dense fibrous tissue. The cell density increases toward the periphery of the nodules, and there is a minor degree of cellular atypia.
ing entirely in keeping with the diagnosis and which does not indicate malignancy. Follow-up MRI performed at 7 and 36 months postexcision showed residual soft tissue nodules in the foot but no definite interval growth. Follow-up radiography also showed the continuing lateral subluxation of the 2nd metatarsal (Fig. 4). The patient had hypersensitive scars at follow-up but no increase in swelling clinically.
Fig. 4 Follow-up radiograph of the foot demonstrates continuing lateral displacement of the 2nd metatarsal.
SC is rare in the foot, with the few reported cases showing predominant involvement of a single joint with some radiographic evidence of mineralization [3, 4]. In the series by Young-In Lee et al. [3], all four cases involved a single joint in the foot and showed evidence of mineralization on radiographs and CT. Radiographic evidence of fine calcification has been reported in 85% of cases of SC [5]. Overall, calcification/ossification is seen in approximately 80% of cases of SC [6]. Calcification on MRI manifests as signal void on all sequences and is best seen on gradientecho images [7, 8]. Care must be taken not to mistake the signal void in SC with the haemosiderin deposits of PVNS [9, 10]. Although PVNS was considered in the differential diagnosis because of the multifocal erosions and soft tissue nodules, there were no low signal intensity foci typical of haemosiderin on MRI. If typical calcific/ossific loose bodies are seen, diagnosis of SC is relatively easy. However, in our case, calcification was not evident on radiography or CT. When soft tissue masses of SC are large and multifocal, they can be mistaken for sarcoma, as in our patient. Hence, careful evaluation of the images at an appropriate centre, with a needle biopsy for histological diagnosis, is required before any operative intervention is contemplated, especially when there are no specific imaging features to provide the diagnosis. Bone erosions adjacent to masses of SC may be seen. Tightness of the capsule has been postulated as the cause of erosions in joints such as the wrist and hip [2, 6, 11]. In the absence of calcification, large soft tissue masses eroding bones suggest aggressive lesions [11]. MRI demonstrates more erosions than radiographs do [5]. The MRI appearance of SC is variable and depends on the relative presence of loose bodies and proliferative synovium. On T1-weighted images, they are usually homogeneous and isointense to muscle and are heterogeneously high signal on T2-weighted and STIR sequences. Contrast enhancement with gadolinium has also been suggested to differentiate synovial fluid from the synovial masses of SC [6, 7]. Lisfranc dislocation involving the forefoot is most commonly seen in the setting of trauma due to multiple metatarsal fractures. The important Y-shaped interosseous metatarsocuneiform ligament (also called the Lisfranc ligament) extends on the plantar surface from the proximal medial base of the 2nd metatarsal to the distal lateral aspect of the medial cuneiform bone [12]. When this is torn, it leads to forefoot instability. The most frequent nontraumatic cause is neuropathic foot due to diabetes [13]. Our case illustrates another cause of nontraumatic Lisfranc dislocation of the forefoot, namely an aggressive arthropathy such as SC. The sensation of foot instability and pain described in this case was most likely the result of disruption of the Lisfranc ligament by masses of SC at the
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bases of the metatarsals. The lateral subluxation of the 2nd metatarsal at the tarsometatarsal joint probably resulted from a combination of the patient walking on the foot and the SC mass between the 1st and 2nd metatarsals exerting a gradual displacing force on the 2nd metatarsal. Although there was lateral offset of the 2nd metatarsal in our case, there was no offset of the 1st metatarsal, presumably be-
cause the dorsal medial ligament connecting the medial cuneiform to the base of the 1st metatarsal was intact [14]. It should be noted that there are no stabilising ligaments connecting the bases of the 1st and 2nd metatarsal bones [12]. To the best of our knowledge, SC causing Lisfranc tarsometatarsal dislocation has not been reported in the world literature before.
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