Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-3024-3
SHOULDER
Secondary synovial chondromatosis of the shoulder Jong-Hun Ji • Mohamed Shafi • Dong-Seok Jeong
Received: 19 October 2013 / Accepted: 19 April 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Synovial chondromatosis is classified as either primary or secondary. Primary synovial chondromatosis results from a proliferation of chondrocytes in the synovial membrane leading to the formation of cartilaginous loose bodies. Secondary synovial chondromatosis is a rare condition characterized by the growth of separated particles from the articular cartilage or osteophytes in joint diseases. The present article aims to report the secondary chondromatosis of the shoulder and to discuss the clinical manifestations, pathogenesis, diagnosis, histological findings and management of this condition. Level of evidence IV. Keywords
loose bodies in synovial chondromatosis are usually distinctive, whereas the clinical findings may be ambiguous. Secondary synovial chondromatosis of the shoulder joint is a very rare condition [5]. We present here two cases suggestive of secondary synovial chondromatosis of the shoulder following the histological examination. Primary synovial chondromatosis in the shoulder joint has been previously reported [1, 2, 4]. The present study aimed to evaluate the clinical presentation, pathophysiology, diagnostic modalities, histological findings, differential diagnosis and management aspects of secondary synovial chondromatosis involving the shoulder joint.
Synovial Chondromatosis Shoulder Case reports
Introduction
Case 1
Primary synovial chondromatosis is a rare disorder in which cartilaginous or osteocartilaginous loose bodies, usually in large numbers, form in the joint space without an apparent underlying injury to the cartilage or synovium [8]. In contrast, secondary synovial chondromatosis results from the growth of separated particles from the articular cartilage or osteophytes in joint diseases, such as osteochondritis dissecans, osteoarthritis, and osteochondral fractures [8]. Although morphologic overlap with the secondary types may occur, the histopathological features of
A 20-year-old right-hand dominant male athlete presented with pain and limited range of motion of the right shoulder. He was perfectly well until the age of 15 years, when he dislocated his shoulder while playing baseball. Since the initial shoulder injury, his shoulder was dislocated at least another 20 times; on these occasions, he was able to reduce his shoulder by himself. One year previously, he dislocated his shoulder again, but this time, he was unable to reduce his shoulder by himself and experienced significant pain. His shoulder continued to dislocate more frequently while resisting easy reduction. His pain also increased further, and he was referred to our hospital by his athletic trainer for further management. On physical examination, he had positive findings on the anterior apprehension test and anterior drawer test for shoulder instability. Plain radiographs demonstrated multiple discrete radiopaque bodies within the shoulder joint (Fig. 1a). Magnetic resonance
J.-H. Ji M. Shafi (&) D.-S. Jeong Department of Orthopedic Surgery, College of Medicine, Daejeon St. Mary’s Hospital, The Catholic University of Korea, 520-2, Daehung-dong, Jung-gu, Daejeon 302-803, South Korea e-mail: [email protected]
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imaging (MRI) in the axial and sagittal views showed multiple loose bodies in the axillary pouch and subcoracoid space (Fig. 1b). Shoulder arthroscopy was performed via the standard posterior portal with the patient in the lateral position. Many cartilaginous loose bodies and active intrasynovial proliferation were identified in the axillary pouch (Fig. 2a, b) and the rotator interval with severe fraying of the humeral head cartilage (Outerbridge grade III) and fraying of the biceps tendon. All the loose bodies were removed followed by partial synovectomy was performed. Subsequently, Bankart repair with an anterior capsuloplasty was performed, and a rotator interval closure was performed. A synovial biopsy showed slight non-specific chronic synovitis and loose bodies with metaplastic cartilage underlying the connective tissue. The cartilage of the loose bodies was cellular and frequently showed extensive concentric zonal annular calcification. There were no foci of chondrometaplasia, and binucleated, empty lacunae were seen frequently (Fig. 3a, b). At the one-year follow-up, MRI showed no evidence of recurrence of synovial chondromatosis. At his last followup (3 years postoperatively), he remained asymptomatic, and there was no clinical or radiographic evidence of recurrence.
Case 2 A 67-year-old woman experienced pain in her dominant right shoulder for 2 years. The pain and stiffness worsened in the 6 months before presentation. She had a history of surgical repair of a rotator cuff tear 5 years previously. Physical examination showed no atrophy or deformity in the right shoulder. She had positive findings for Neer and Hawkins impingement signs and a negative lift-off or bear hug test. Plain radiographs showed several loose bodies in the shoulder joint, severe subchondral cysts with marked erosion, and the anchor screw of the greater tuberosity. Coronal T1-weighted MRI images revealed a large, fullthickness supraspinatus tendon tear, several loose bodies in the shoulder joint, and severe erosion in the greater tuberosity. An enhancement study showed marked synovial and fluid enhancement, suggesting synovitis and associated synovial chondromatosis. Given the extent of shoulder involvement, and in line with the patient’s wishes, a reverse shoulder arthroplasty was planned. After opening the shoulder joint through the deltopectoral approach, multiple large loose bodies were observed in both the greater tuberosity area and the shoulder joint and were retrieved. Although the joint capsule showed mild synovitis, the articular cartilage of the
Fig. 1 a Anteroposterior radiograph of the right shoulder b axial MRI showing the loose bodies
Fig. 2 a Arthroscopic findings of loose bodies b sample of gross specimen removed from the shoulder
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Knee Surg Sports Traumatol Arthrosc
Fig. 3 a Histological section of a loose body showing a fragment of articular cartilage, focal calcification, multiple foreign-body giant cells, and superficial loose connective tissue (H&E940) b histological section showed—chondrocytes with large hyperchromatic nuclei (H&E9200)
humeral head and glenoid showed severe arthritic changes (Fig. 4). The rotator cuff showed complete tear of the supraspinatus and infraspinatus. The patient underwent reverse shoulder arthroplasty (Tornier S.A. Aequalis, cemented). Post-operative histopathological examination of the loose bodies confirmed the diagnosis of secondary synovial chondromatosis. At her last follow-up (2.6 years), the patient was free from pain and stiffness and was continuing her daily activities.
Discussion Synovial chondromatosis is a rare metaplastic condition characterized by the formation of multiple cartilaginous foci within the synovium; these foci eventually break free to form loose bodies [8]. This condition is often monoarticular and most commonly affects the knee joint and to a lesser extent the hip, elbow, wrist, and ankle joints [6]. Synovial chondromatosis within the shoulder joint has been reported previously, although only approximately 5 % of documented cases involve the shoulder [1, 2, 4, 7]. In 70–95 % of cases of primary synovial chondromatosis, radiographs reveal multiple intraarticular calcifications that are typically evenly distributed throughout the joint. In cases of secondary synovial chondromatosis, osteochondral intraarticular fragments are also observed. However, these are fewer in numbers and more variable in size (suggesting various times of origin) as compared with the fragments observed in primary disease. In addition, in the secondary type, several rings of calcification may be identified on radiographs, compared with the single ring seen in primary disease [9]. The present cases were considered to have been at a late stage of the disease where ossification had already occurred. MR imaging of the loose bodies is useful for demonstrating variable intrinsic
Fig. 4 Intra-operative finding showing cartilage erosion on the humeral head
appearances, depending on the degree of calcification, although the extent of the disease (particularly soft-tissue or bursal involvement) is optimally depicted [3]. Villacin et al. [12] proposed histological criteria for the differentiation of primary and secondary synovial chondromatosis. Loose bodies in primary synovial chondromatosis were nodular, showing plump chondrocytes and irregular calcification, and all contained proliferative cell nuclear antigen-positive chondrocytes. Loose bodies in secondary synovial chondromatosis showed uniform chondrocytes and annular calcification surrounding the
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core tissue. Histological examination of the extracted loose bodies in the reported cases revealed evenly distributed chondrocytes and concentric rings of calcification, thereby leading to a diagnosis of secondary chondromatosis. Secondary chondromatosis may be caused by joint diseases such as OA, osteochondral fractures, osteonecrosis, osteochondritis dissecans, Charcot joints, metabolic arthritis, and villonodular synovitis pigmentosa. In the first case, considering the patient’s young age and the association with recurrent shoulder dislocations and athletic activity, osteochondritis dissecans may have been the condition leading to the formation of loose bodies in the shoulder joint. In this case, arthroscopy revealed a depression in the upper region of the humeral head with severe fraying of the humeral head cartilage (Outerbridge grade III). The smooth margins of the depression and the calcification of the extracted loose bodies suggest that a considerable period had elapsed since their formation. The osteochondral fragments grew within the joint through the years, and the multiple loose bodies caught within the shoulder joint prevented redislocation in this patient in the later stage of the condition. Arthroscopic removal of the loose bodies relieved the patient’s discomfort and prevented future injuries. In cases of recurrent dislocations of the shoulder where there is difficulty in spontaneous reduction when the shoulder was easily reduced previously, osteochondritis dissecans that may have developed into secondary chondromatosis should be suspected. In the second case, the patient underwent an arthroscopic rotator cuff repair 5 years previously, and 3 years after the surgery, she developed progressively worsening pain and other symptoms similar to those she experienced preoperatively. She may have re-torn her rotator cuff at this stage, resulting in the loss of the balanced force couples needed to establish a stable fulcrum for the shoulder joint, in turn causing instability. The shoulder instability caused by rotator cuff dysfunction and proximal migration of the humeral head to the point of acromial impingement results in degenerative changes on the humeral head, superior glenoid, and the undersurface of acromion. The end result is a shoulder joint with severe joint destruction, where articular cartilage is shredded and found as loose bodies in the joint. In particular, synovectomy is recommended for the prevention of relapses [11]. Therefore, arthroscopic partial synovectomy was performed in the first case, and complete open synovectomy was performed in the second case. These patients were followed for more than 2 years, and no recurrence was observed. Although the diagnosis of synovial chondromatosis is often obvious from the radiologic and intraoperative findings, definite diagnoses as well as lesion characterization
123
(benign vs. malignant) require histological confirmation. On the basis of currently known molecular abnormalities, primary synovial chondromatosis is believed to be a benign neoplastic condition rather than a metaplastic disease. These cytogenetic aberrations are absent in secondary synovial chondromatosis [10]. The primary form is thought to be progressive and more likely to recur, and its longterm presence may lead to severe degenerative arthritis, while the secondary form is not likely to recur following surgical removal [4]. In cases of primary synovial chondromatosis, regular follow-up examinations that include MRI are recommended for up to 2 years. Recognizing the clinical importance of secondary synovial chondromatosis, which reflects its underlying pathological characteristics, improves its assessment and in turn facilitates optimal patient management.
References 1. Buess E, Friedrich B (2001) Synovial chondromatosis of the glenohumeral joint: a rare condition. Arch Orthop Trauma Surg 121:109–111 2. Chillemi C, Marinelli M, de Cupis V (2005) Primary synovial chondromatosis of the shoulder: clinical, arthroscopic and histopathological aspects. Knee Surg Sports Traumatol Arthrosc 13:483–488 3. Crotty JM, Monu JUV, Pope TL (1996) Synovial osteochondromatosis. Radiol Clin North Am 34:327–341 4. Gasbarrini A, Biscaglia R, Donati D, Casedei R, Picci P (1997) Synovial chondromatosis of the shoulder. A review of the literature and description of a clinical case. Chir Organi Mov 82:73–81 5. Hamada J, Tamai K, Koguchi Y, Ono W, Saotome K (2005) Case report: a rare condition of secondary synovial osteochondromatosis of the shoulder joint in a young female patient. J Shoulder Elbow Surg 14:653–656 6. Imhoff A, Schreiber A (1988) Synovial chondromatosis. Orthopade 17:233–244 7. Jung KA, Kim SJ, Jeong JH (2007) Arthroscopic treatment of synovial chondromatosis that possibly developed after open capsular shift for shoulder instability. Knee Surg Sports Traumatol Arthrosc 15:1499–1503 8. Milgram JW (1977) The classification of loose bodies in human joints. Clin Orthop Relat Res 124:282–291 9. Murphey MD, Vidal JA, Fanburg-Smith JC, Gajewski DA (2007) Imaging of synovial chondromatosis with radiologic-pathologic correlation. Radiographics 27:1465–1488 10. Robinson D, Hasharoni A, Evron Z, Segal M, Nevo Z (2000) Synovial chondromatosis: the possible role of FGF 9 and FGF receptor 3 in its pathology. Int J Exp Pathol 81:183–189 11. Shpitzer T, Ganel A, Engelberg S (1990) Surgery for synovial chondromatosis: 26 cases followed up for 6 years. Acta Orthop Scand 61:567–569 12. Villacin AB, Brigham LN, Bullough PG (1979) Primary and secondary synovial chondrometaplasia: histopathologic and clinicoradiologic differences. Hum Pathol 10:439–451
SHOULDER
Secondary synovial chondromatosis of the shoulder Jong-Hun Ji • Mohamed Shafi • Dong-Seok Jeong
Received: 19 October 2013 / Accepted: 19 April 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract Synovial chondromatosis is classified as either primary or secondary. Primary synovial chondromatosis results from a proliferation of chondrocytes in the synovial membrane leading to the formation of cartilaginous loose bodies. Secondary synovial chondromatosis is a rare condition characterized by the growth of separated particles from the articular cartilage or osteophytes in joint diseases. The present article aims to report the secondary chondromatosis of the shoulder and to discuss the clinical manifestations, pathogenesis, diagnosis, histological findings and management of this condition. Level of evidence IV. Keywords
loose bodies in synovial chondromatosis are usually distinctive, whereas the clinical findings may be ambiguous. Secondary synovial chondromatosis of the shoulder joint is a very rare condition [5]. We present here two cases suggestive of secondary synovial chondromatosis of the shoulder following the histological examination. Primary synovial chondromatosis in the shoulder joint has been previously reported [1, 2, 4]. The present study aimed to evaluate the clinical presentation, pathophysiology, diagnostic modalities, histological findings, differential diagnosis and management aspects of secondary synovial chondromatosis involving the shoulder joint.
Synovial Chondromatosis Shoulder Case reports
Introduction
Case 1
Primary synovial chondromatosis is a rare disorder in which cartilaginous or osteocartilaginous loose bodies, usually in large numbers, form in the joint space without an apparent underlying injury to the cartilage or synovium [8]. In contrast, secondary synovial chondromatosis results from the growth of separated particles from the articular cartilage or osteophytes in joint diseases, such as osteochondritis dissecans, osteoarthritis, and osteochondral fractures [8]. Although morphologic overlap with the secondary types may occur, the histopathological features of
A 20-year-old right-hand dominant male athlete presented with pain and limited range of motion of the right shoulder. He was perfectly well until the age of 15 years, when he dislocated his shoulder while playing baseball. Since the initial shoulder injury, his shoulder was dislocated at least another 20 times; on these occasions, he was able to reduce his shoulder by himself. One year previously, he dislocated his shoulder again, but this time, he was unable to reduce his shoulder by himself and experienced significant pain. His shoulder continued to dislocate more frequently while resisting easy reduction. His pain also increased further, and he was referred to our hospital by his athletic trainer for further management. On physical examination, he had positive findings on the anterior apprehension test and anterior drawer test for shoulder instability. Plain radiographs demonstrated multiple discrete radiopaque bodies within the shoulder joint (Fig. 1a). Magnetic resonance
J.-H. Ji M. Shafi (&) D.-S. Jeong Department of Orthopedic Surgery, College of Medicine, Daejeon St. Mary’s Hospital, The Catholic University of Korea, 520-2, Daehung-dong, Jung-gu, Daejeon 302-803, South Korea e-mail: [email protected]
123
Knee Surg Sports Traumatol Arthrosc
imaging (MRI) in the axial and sagittal views showed multiple loose bodies in the axillary pouch and subcoracoid space (Fig. 1b). Shoulder arthroscopy was performed via the standard posterior portal with the patient in the lateral position. Many cartilaginous loose bodies and active intrasynovial proliferation were identified in the axillary pouch (Fig. 2a, b) and the rotator interval with severe fraying of the humeral head cartilage (Outerbridge grade III) and fraying of the biceps tendon. All the loose bodies were removed followed by partial synovectomy was performed. Subsequently, Bankart repair with an anterior capsuloplasty was performed, and a rotator interval closure was performed. A synovial biopsy showed slight non-specific chronic synovitis and loose bodies with metaplastic cartilage underlying the connective tissue. The cartilage of the loose bodies was cellular and frequently showed extensive concentric zonal annular calcification. There were no foci of chondrometaplasia, and binucleated, empty lacunae were seen frequently (Fig. 3a, b). At the one-year follow-up, MRI showed no evidence of recurrence of synovial chondromatosis. At his last followup (3 years postoperatively), he remained asymptomatic, and there was no clinical or radiographic evidence of recurrence.
Case 2 A 67-year-old woman experienced pain in her dominant right shoulder for 2 years. The pain and stiffness worsened in the 6 months before presentation. She had a history of surgical repair of a rotator cuff tear 5 years previously. Physical examination showed no atrophy or deformity in the right shoulder. She had positive findings for Neer and Hawkins impingement signs and a negative lift-off or bear hug test. Plain radiographs showed several loose bodies in the shoulder joint, severe subchondral cysts with marked erosion, and the anchor screw of the greater tuberosity. Coronal T1-weighted MRI images revealed a large, fullthickness supraspinatus tendon tear, several loose bodies in the shoulder joint, and severe erosion in the greater tuberosity. An enhancement study showed marked synovial and fluid enhancement, suggesting synovitis and associated synovial chondromatosis. Given the extent of shoulder involvement, and in line with the patient’s wishes, a reverse shoulder arthroplasty was planned. After opening the shoulder joint through the deltopectoral approach, multiple large loose bodies were observed in both the greater tuberosity area and the shoulder joint and were retrieved. Although the joint capsule showed mild synovitis, the articular cartilage of the
Fig. 1 a Anteroposterior radiograph of the right shoulder b axial MRI showing the loose bodies
Fig. 2 a Arthroscopic findings of loose bodies b sample of gross specimen removed from the shoulder
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Knee Surg Sports Traumatol Arthrosc
Fig. 3 a Histological section of a loose body showing a fragment of articular cartilage, focal calcification, multiple foreign-body giant cells, and superficial loose connective tissue (H&E940) b histological section showed—chondrocytes with large hyperchromatic nuclei (H&E9200)
humeral head and glenoid showed severe arthritic changes (Fig. 4). The rotator cuff showed complete tear of the supraspinatus and infraspinatus. The patient underwent reverse shoulder arthroplasty (Tornier S.A. Aequalis, cemented). Post-operative histopathological examination of the loose bodies confirmed the diagnosis of secondary synovial chondromatosis. At her last follow-up (2.6 years), the patient was free from pain and stiffness and was continuing her daily activities.
Discussion Synovial chondromatosis is a rare metaplastic condition characterized by the formation of multiple cartilaginous foci within the synovium; these foci eventually break free to form loose bodies [8]. This condition is often monoarticular and most commonly affects the knee joint and to a lesser extent the hip, elbow, wrist, and ankle joints [6]. Synovial chondromatosis within the shoulder joint has been reported previously, although only approximately 5 % of documented cases involve the shoulder [1, 2, 4, 7]. In 70–95 % of cases of primary synovial chondromatosis, radiographs reveal multiple intraarticular calcifications that are typically evenly distributed throughout the joint. In cases of secondary synovial chondromatosis, osteochondral intraarticular fragments are also observed. However, these are fewer in numbers and more variable in size (suggesting various times of origin) as compared with the fragments observed in primary disease. In addition, in the secondary type, several rings of calcification may be identified on radiographs, compared with the single ring seen in primary disease [9]. The present cases were considered to have been at a late stage of the disease where ossification had already occurred. MR imaging of the loose bodies is useful for demonstrating variable intrinsic
Fig. 4 Intra-operative finding showing cartilage erosion on the humeral head
appearances, depending on the degree of calcification, although the extent of the disease (particularly soft-tissue or bursal involvement) is optimally depicted [3]. Villacin et al. [12] proposed histological criteria for the differentiation of primary and secondary synovial chondromatosis. Loose bodies in primary synovial chondromatosis were nodular, showing plump chondrocytes and irregular calcification, and all contained proliferative cell nuclear antigen-positive chondrocytes. Loose bodies in secondary synovial chondromatosis showed uniform chondrocytes and annular calcification surrounding the
123
Knee Surg Sports Traumatol Arthrosc
core tissue. Histological examination of the extracted loose bodies in the reported cases revealed evenly distributed chondrocytes and concentric rings of calcification, thereby leading to a diagnosis of secondary chondromatosis. Secondary chondromatosis may be caused by joint diseases such as OA, osteochondral fractures, osteonecrosis, osteochondritis dissecans, Charcot joints, metabolic arthritis, and villonodular synovitis pigmentosa. In the first case, considering the patient’s young age and the association with recurrent shoulder dislocations and athletic activity, osteochondritis dissecans may have been the condition leading to the formation of loose bodies in the shoulder joint. In this case, arthroscopy revealed a depression in the upper region of the humeral head with severe fraying of the humeral head cartilage (Outerbridge grade III). The smooth margins of the depression and the calcification of the extracted loose bodies suggest that a considerable period had elapsed since their formation. The osteochondral fragments grew within the joint through the years, and the multiple loose bodies caught within the shoulder joint prevented redislocation in this patient in the later stage of the condition. Arthroscopic removal of the loose bodies relieved the patient’s discomfort and prevented future injuries. In cases of recurrent dislocations of the shoulder where there is difficulty in spontaneous reduction when the shoulder was easily reduced previously, osteochondritis dissecans that may have developed into secondary chondromatosis should be suspected. In the second case, the patient underwent an arthroscopic rotator cuff repair 5 years previously, and 3 years after the surgery, she developed progressively worsening pain and other symptoms similar to those she experienced preoperatively. She may have re-torn her rotator cuff at this stage, resulting in the loss of the balanced force couples needed to establish a stable fulcrum for the shoulder joint, in turn causing instability. The shoulder instability caused by rotator cuff dysfunction and proximal migration of the humeral head to the point of acromial impingement results in degenerative changes on the humeral head, superior glenoid, and the undersurface of acromion. The end result is a shoulder joint with severe joint destruction, where articular cartilage is shredded and found as loose bodies in the joint. In particular, synovectomy is recommended for the prevention of relapses [11]. Therefore, arthroscopic partial synovectomy was performed in the first case, and complete open synovectomy was performed in the second case. These patients were followed for more than 2 years, and no recurrence was observed. Although the diagnosis of synovial chondromatosis is often obvious from the radiologic and intraoperative findings, definite diagnoses as well as lesion characterization
123
(benign vs. malignant) require histological confirmation. On the basis of currently known molecular abnormalities, primary synovial chondromatosis is believed to be a benign neoplastic condition rather than a metaplastic disease. These cytogenetic aberrations are absent in secondary synovial chondromatosis [10]. The primary form is thought to be progressive and more likely to recur, and its longterm presence may lead to severe degenerative arthritis, while the secondary form is not likely to recur following surgical removal [4]. In cases of primary synovial chondromatosis, regular follow-up examinations that include MRI are recommended for up to 2 years. Recognizing the clinical importance of secondary synovial chondromatosis, which reflects its underlying pathological characteristics, improves its assessment and in turn facilitates optimal patient management.
References 1. Buess E, Friedrich B (2001) Synovial chondromatosis of the glenohumeral joint: a rare condition. Arch Orthop Trauma Surg 121:109–111 2. Chillemi C, Marinelli M, de Cupis V (2005) Primary synovial chondromatosis of the shoulder: clinical, arthroscopic and histopathological aspects. Knee Surg Sports Traumatol Arthrosc 13:483–488 3. Crotty JM, Monu JUV, Pope TL (1996) Synovial osteochondromatosis. Radiol Clin North Am 34:327–341 4. Gasbarrini A, Biscaglia R, Donati D, Casedei R, Picci P (1997) Synovial chondromatosis of the shoulder. A review of the literature and description of a clinical case. Chir Organi Mov 82:73–81 5. Hamada J, Tamai K, Koguchi Y, Ono W, Saotome K (2005) Case report: a rare condition of secondary synovial osteochondromatosis of the shoulder joint in a young female patient. J Shoulder Elbow Surg 14:653–656 6. Imhoff A, Schreiber A (1988) Synovial chondromatosis. Orthopade 17:233–244 7. Jung KA, Kim SJ, Jeong JH (2007) Arthroscopic treatment of synovial chondromatosis that possibly developed after open capsular shift for shoulder instability. Knee Surg Sports Traumatol Arthrosc 15:1499–1503 8. Milgram JW (1977) The classification of loose bodies in human joints. Clin Orthop Relat Res 124:282–291 9. Murphey MD, Vidal JA, Fanburg-Smith JC, Gajewski DA (2007) Imaging of synovial chondromatosis with radiologic-pathologic correlation. Radiographics 27:1465–1488 10. Robinson D, Hasharoni A, Evron Z, Segal M, Nevo Z (2000) Synovial chondromatosis: the possible role of FGF 9 and FGF receptor 3 in its pathology. Int J Exp Pathol 81:183–189 11. Shpitzer T, Ganel A, Engelberg S (1990) Surgery for synovial chondromatosis: 26 cases followed up for 6 years. Acta Orthop Scand 61:567–569 12. Villacin AB, Brigham LN, Bullough PG (1979) Primary and secondary synovial chondrometaplasia: histopathologic and clinicoradiologic differences. Hum Pathol 10:439–451
