A 1-year-old male neutered ferret (Mustela putorius furo) was evaluated for an abnormal left cubital joint. Radiographs demonstrated a proliferative osseous lesion of the left proximal antebrachium. Computed tomography confirmed a large thin-walled expansile osseous lesion of the left proximal radius and identified multifocal proliferative lesions of the axial spine, two of which caused spinal cord compression. A left forelimb amputation with total scapulectomy was performed. Histopathology revealed a well-demarcated mass with a thin rim of mature lamellar bone and a discontinuous cartilage cap covered by a perichondrial/periosteal membrane continuous with the adjacent bone. Findings were most consistent with an osteochondroma or osteochondromatosis (i.e., multiple cartilaginous exostoses, hereditary multiple exostoses). No evidence of malignant transformation was observed within this specimen. Three months post-surgery, verbal correspondence with the owner confirmed return to normal activity level and no emergence of neurological signs. Repeat examination and imaging were recommended.

Synovial chondromatosis is a rare benign condition defined by the presence of cartilaginous lesions in the synovium of joints, tendon sheaths, and bursae. It most typically affects large joints, such as the knee, hip, and shoulder, but it is also reported in smaller joints. Nonetheless, ankle involvement is relatively uncommon. A complete history and clinical, physical, and radiographic examinations are usually used to determine the diagnosis. Hence, we reported a case of a young patient with left ankle primary synovial chondromatosis who presented with a left ankle mass and chronic pain.

Synovial chondromatosis is a rare and benign disorder that involves the synovial lining of joints, synovial sheaths and bursae. The synovial layer of the joint is affected by a metaplastic process which in turn converts it into cartilagenous tissue. Eventually, it gets dislodged and transformed into a loose body in the large joints. We report the case of a 24-year-old young athlete who presented with complaints of painful movements and restriction of joint movements associated with a growing deformity in the right knee joint. This case report aims to describe a rare synovial pathology that necessitated arthroscopic synovectomy and diagnostic arthroscopy to treat, particularly in younger individuals. The atypical feature, in this case, was metaplastic development from the peripheral joint capsule attached to the surrounding cartilage, which, to the extent that the authors are aware, has only been documented in one instance in the record. Magnetic resonance imaging (MRI) was performed which demonstrated evidence of the joint effusion, synovial hypertrophy and a loose calcific body just anterior of the distal femoral condyle causing pressure over the patellar tendon anteriorly as well as a hyper-dense cyst in the popliteal region. Treatment often requires partial or complete synovectomy with either an arthroscopic or open approach.

Synovial osteochondromatosis or synovial chondromatosis is a benign joint pathology characterized by the development of multiple cartilaginous nodules or loose bodies in the synovial membrane that typically arise in the larger joints of the body. It usually presents as joint pain and, as seen in the present case, can occasionally be missed. Diagnosis involves a combination of clinical evaluation, imaging studies, and histopathological evaluation (which is confirmatory). Treatment depends on the severity of the disease, symptoms, and the patient\'s social situation, and may include monitoring for asymptomatic cases, non-surgical management (pain medications and physical therapy), or surgical intervention. Surgical intervention may include arthroscopic removal of loose bodies, synovectomy, or reconstruction/replacement in severe situations. Prognosis has a direct relationship to how early the disease is diagnosed. Early intervention with appropriate management can help alleviate symptoms; however, if left unmanaged, it can lead to joint damage and osteoarthritis or very rarely, malignant transformation into chondrosarcoma. This report describes the case of a 62-year-old female with complaints of bilateral knee pain who was originally diagnosed with osteoarthritis based on clinical exam and X-rays. Two magnetic resonance imaging (MRI) scans were done three years apart, with synovial osteochondromatosis being on the differential after the second scan. A left knee major synovectomy was conducted after the second MRI reading, where rubbery masses of tissue along with loose fragments were removed. Fluid from the tissue masses was sent to culture and pathology for interpretation. Two weeks post the surgery, the patient\'s pain improved tremendously, with adequate ambulation independently. Histopathology came back positive for synovial osteochondromatosis. This case report highlights the importance of keeping this joint pathology on the differential when treating patients with joint pain and interpreting imaging.

Feline osteochondromatosis is a spontaneous osteocartilaginous exostosis associated with feline leukaemia virus (FeLV) infection or due to a frameshift variant in the exostosin glycosyltransferase 1 (EXT1) gene. Osteochondromatosis was diagnosed in an indoor-only, 12-year-old, neutered female, Russian Blue cat. Radiographs revealed bilateral calcified proliferations in the elbow, costochondral and sternochondral joints, which distorted the normal skeletal structure. Grossly, the proliferated joints presented with consistent, rounded masses, causing complete ankylosis. The main histopathological finding was an osteocartilaginous proliferation composed of multiple irregular islands of well-differentiated hyaline cartilage surrounded and delimited by osteoid tissue. Immunohistochemistry of the osteochondromas, bone marrow and mediastinal lymph nodes, using a primary anti-FeLV gp70 antibody, and FeLV proviral DNA real-time polymerase chain reaction on bone marrow were negative. Sequencing of exon 6 of the EXT1 gene was performed and nucleotide BLAST analysis demonstrated the absence of a frameshift variant. This study reports the only case of spontaneous feline osteochondromatosis in an animal more than 10 years old.

Apart from a few case reports, sacroiliac joint (SIJ) involvement in osteochondromatosis has not been studied. We aimed to determine the prevalence and characteristics of such involvement using cross-sectional imaging.
In this retrospective study, three observers (one junior radiologist and two musculoskeletal radiologists) independently reviewed computed tomography (CT) or magnetic resonance imaging (MRI) of patients in our database who had osteochondromatosis (≥2 osteochondromas across the skeleton) for SIJ involvement. The final decision was reached by the consensus of the two musculoskeletal radiologists in a later joint session.
Of the 36 patients with osteochondromatosis in our database, 22 (61%) had cross-sectional imaging covering SIJs (14 females, 8 males; age range 7-66 years; mean age 23 years; 13 MRI, 9 CT). Of these, 16 (73%) had intra-articular osteochondromas. For identifying SIJ osteochondromas on cross-sectional imaging, interobserver agreement was substantial [κ = 0.67; 95% confidence interval (CI): 0.34, 1.00] between the musculoskeletal radiologists and moderate (κ = 0.59; 95% CI: 0.23, 0.94) between the junior radiologist and the final consensus decision of the two musculoskeletal radiologists. In the cohort with cross-sectional imaging, the anatomical variations of the accessory SIJ (n = 6, 27%) and iliosacral complex (n = 2, 9%) were identified in six different patients with (n = 2) and without (n = 4) sacroiliac osteochondromas.
Cross-sectional imaging shows frequent (73%) SIJ involvement in osteochondromatosis, which, although a rare disorder, nevertheless needs to be considered in the differential diagnosis of such SIJ anatomical variants as the accessory SIJ and iliosacral complex. Differentiating these variants from osteochondromas is challenging in patients with osteochondromatosis.

UNASSIGNED: Synovial osteochondromatosis (SOC) of the shoulder is a rare condition with unclear characteristics. This study evaluated the clinical features and postoperative functional outcomes of SOC of the shoulder that are distinct from SOC of other joints.
UNASSIGNED: The characteristics of 28 shoulders with SOC that underwent arthroscopy were retrospectively assessed. Ten shoulders (35.7%) had rotator cuff tears (RCTs) and underwent concomitant arthroscopic rotator cuff repair. The mean follow-up period was 83.6 months (range, 24-154 months). Demographic characteristics and loose bodies localized under arthroscopy were compared between cases with and without concomitant RCTs. Radiography, ultrasonography, or magnetic resonance imaging were performed preoperatively and postoperatively. Visual analog scale (VAS) scores for pain and satisfaction were evaluated for all cases, and functional scores were assessed in shoulders with concomitant RCTs.
UNASSIGNED: The average age was 36.2 ± 15.6 years among patients without RCTs and 58.3 ± 7.2 years among patients with RCTs. Seven shoulders (7%) had osteoarthritis. Arthroscopy revealed loose bodies in multiple spaces, including the glenohumeral joint, subacromial (SA) space, and biceps tendon sheath. Overall, loose bodies were found in multiple spaces in 12 shoulders (42.9%). Loose bodies were found in the SA space only in 4 shoulders (22.2%) without RCTs and in 7 shoulders (70.0%) with RCTs. VAS for pain decreased significantly from 3.9 ± 2.3 to 1.1 ± 1.3 (p < 0.001). The functional scores increased significantly after arthroscopic management for patients with concurrent RCTs (all p < 0.05). Recurrence of SOC occurred in 3 of the 22 shoulders (13.6%) who underwent postoperative imaging, but no patient had a recurrent RCT.
UNASSIGNED: Pain relief and patient satisfaction were achieved via arthroscopic management. Unlike in other joints, loose bodies can occur simultaneously in several spaces in the shoulder, including the glenohumeral joint, SA space, and biceps tendon sheath. Early diagnosis of SOC of the SA space can help prevent osteoarthritis and RCT progression.

Primary synovial osteochondromatosis of the ankle is a rare and benign disease of the young adult. It is characterized by the formation of multiple nodules of hyaline cartilage under the synovium. It is usually asymptomatic but can sometimes be revealed by pain or joint mobility disorders. X-rays and CT scans can easily diagnose calcified osteochondromas, but ultrasound and MRI can provide a quicker diagnosis by visualizing non-calcified foreign bodies. Surgery under arthroscopy remains the best therapeutic choice, however, this pathology still causes recurrence in less than 1/3 of cases.

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UNASSIGNED: Synovial chondromatosis is a condition where the cells lining a joint form benign cartilaginous tumors. This benign cartilage metaplasia results in the formation of multiple intra-articular loose bodies within a joint.
UNASSIGNED: This case is a 59-year-old female that presented with constant, severe left hip pain that was localized to the groin and began 2 years ago. There were severe limitation of hip flexion, extension, pain on internal rotation, and a half inch left leg shortening. Radiographs demonstrated multiple round opacities surrounding the left femoral neck. MRI showed numerous, small rounded intra-articular loose bodies, measuring about 5-6 mm each within the left hip joint.
UNASSIGNED: A lateral approach toward the hip was used to perform an osteotomy at the portion of the greater trochanter. The hip capsule was identified and an S-shaped incision was then made through the capsule. Repetitive hip dislocations allowed for improved visualization making further removal of the difficult fragments much easier. The capsule was closed and the osteotomy was reattached. Range of motion was found to be significantly improved compared to preoperatively. No further fixation was necessary and the patient\'s subcutaneous tissue was closed in normal fashion.
UNASSIGNED: The technique used in our case involves a lateral approach with a trochanteric flip osteotomy to preserve the medial femoral circumflex artery and external rotators. This is similar to the approach described by Ganz in 2001 who used a posterior approach. Following the approach, the hip is then dislocated and exposed anteriorly with full visualization of the joint with a gap of about 11 cm between the femoral head and acetabulum. Surgical dislocation allows for the removal of difficult chondromas and osteophytes around the femoral head-and-neck junction. Multiple studies support the idea of surgical dislocation as an exceptional treatment method for SC.