Synovial Chondromatosis Osteochondromatosis

Synovial chondromatosis/osteochondromatosis is considered a benign disease that results in a monoarticular arthropathy. The hip is the third most common site of involvement, surpassed by the elbow and the knee.12-15 Synovial chondromatosis was first described by Jaffe as intrasynovial cartilaginous metaplasia, a histologic diagnosis, which can result in formation of multiple intra- and extracapsular loose bodies.15 Surgical findings reveal thickened synovium and loose bodies of varying size and composition adherent to the synovium or floating free within the joint. (Figure 14.1.) Two forms of the disease have been characterized, primary and secondary. The primary form is characterized by innumerable small, cartilaginous, loose "rice bodies," in contrast to the secondary form, which is characterized by larger coalesced masses of osteocartilaginous tissue. (Figure 14.2.) Laus and Capanna, in slight contrast, classify the process as simple synovial chondromatosis and progressive synovial chondromato-sis, the former describing multiple intra-articular bodies and the later a locally aggressive, cartilaginous neoproliferation in and around the hip.16 Milgram further subdivided synovial chondromatosis into 3 recognizable Stages. Stage I shows active intrasynovial disease with no intra-articular loose bodies; stage II reveals additional lesions with active intrasynovial metaplasia, proliferation, and free intra-articular loose bodies, and stage III exhibits multiple osteochondromal loose bodies

Figure 14.1. Loose bodies of varying size and composition adherent to the synovium.

Figure 14.2. Large coalesced bodies of osteocar-tilaginous tissue.

fi in the absence of intrasynovial disease.17 The majority of reported cases involve intra-articular manifestations of the condition, although symptomatic extra-articular foci also have been described and treated surgically.15-17

When this condition involves the hip joint there are usually long delays in accurate diagnosis and initiation of treatment because of its insidious clinical presentation. Symptoms include the onset of dull aching pain, catching or locking sensations, and mild restriction of motion. Compounding the delay in diagnosis, plain roentgenograms demonstrate the presence of periarticular loose bodies in only 50% of the cases, because calcification within the loose bodies is not consistent.13,18 Zwas et al described a case of hip joint synovial chondromatosis that initially presented with normal radiographs and a bone scan suggestive of a destructive, reactive articular process or late manifestation of femoral head avas-

cular necrosis. Six-month follow-up radiographs showed ra-diolucencies and erosive bone changes in the joint.19 McCarthy has reported an 80% false-negative rate for radiological investigations including plain radiography, bone scintigraphy, CT, plain MRI, and arthrography in evaluating intractable hip pain.20 When diagnoses evident on plain films (eg loose bodies and advanced degenerative joint disease) were excluded, the accurate diagnosis of unremitting hip pain by radiographic modalities fell precipitously to 4%.

Noninvasive diagnostic yield may be increased with gadolinium-enhanced MRI.20 (See Chapter 3.) Computed tomography (CT) or magnetic resonance (MR) arthrograms, when performed, will usually demonstrate multiple intra-articular filling defects, and are recommended in the evaluation of patients whose relatively normal initial studies fail to adequately explain the disabling hip symptoms. (Figure 14.3.)

Figure 14.3. Loose bodies demonstrated on CT scan.

Figure 14.3. Loose bodies demonstrated on CT scan.

Loose Bodies Synovial ChondromatosisIntra Articular Loose Body
Figure 14.4. Loose bodies in advanced synovial chondromatosis demonstrated on plain radiographs.

Clinical history and examination therefore remain invaluable in directing the appropriate management of patients with synovial chondromatosis. Those who present with late disease can be diagnosed by plain radiographs, with findings that include lucencies and erosive, secondary juxta-articular bone erosions. (Figure 14.4.)

The loose bodies associated with synovial chondromatosis/ osteochondromatosis, when small and cartilaginous, can be found in a joint with little articular destruction, while large ossified bodies may result in destructive pressure erosions of the femoral head and neck.19 Although considered benign, synovial chondromatosis as described can be locally aggressive, and reports of sarcomatous change have been pub-lished.16,21-24 Treatment of the condition is based on the premise that the loose and sessile bodies within the tight confines of the hip joint damage the articular cartilage and intra-articular structures. (Figure 14.5.) When proliferative, the disease may present with extensive bony pressure erosions, subluxation of the hip joint, secondary joint degeneration, in-trapelvic mass formation, and pathologic fracture.16,19,25-28

Treatment modalities have traditionally focused on removal of loose bodies, lavage, and synovectomy. Laus and Capanna, based on their classification, concluded that simple synovial chondromatosis should be treated by partial or total syn-ovectomy, while progressive synovial chondromatosis should be treated by total synovectomy with or without arthro-plasty.16 Radiation treatment has been attempted to halt the metaplastic process, but has proven ineffective and may also result in post-irradiation sarcomatous change.21 Most orthopedic surgeons agree that operative treatment is indicated at an early stage in the disease when it is symptomatic and before irreversible degenerative changes have occurred. Surgical removal of loose bodies and synovectomy may relieve symptoms and prevent hip joint degeneration, the sequelae of which can be especially devastating in the younger patient population commonly affected by the condition.

Arthroscopic management of synovial chondromatosis in the knee and shoulder is well documented in the literature, and has essentially been extrapolated into similar treatment options for the hip.14,29-36 Conflicting results in these reports have created controversies in management. Some advocate simple removal of loose bodies within the joint,14,30,37 although others support complete or partial synovectomy to prevent recurrence.13,15,38,39 Maurice et al reported effective treatment with removal of all loose bodies and partial syn-ovectomy in areas of obvious synovial involvement. Their treatment is based on the theory that synovial metaplasia may be confined in focal regions; partial synovectomy in regions with abnormal appearance is therefore curative, and total syn-ovectomy is unnecessary.15 The classification proposed by Milgram would support management of patients with multiple intra-articular loose bodies and quiescent synovium (stage III) with simple removal of loose bodies; this, however, has not correlated well with prognosis or recurrence.15,17 Recurrence rates for synovial chondromatosis following surgical management are reported to range between 7 and 23%.15,30,31 Ogilvie-Harris, in patients with synovial chondromatosis of the knee, demonstrated a statistically lower recurrence rate in patients treated with arthroscopic synovectomy versus simple loose body removal.31 Other authors have demonstrated essentially equivalent recurrence rates with removal of loose bodies alone.30,15

Open hip arthrotomy and synovectomy after dislocation of the femoral head remains the gold standard for definitive treatment of synovial chondromatosis at an advanced stage. Pos-tel et al have reported on 23 cases of synovial chondromatosis treated with open arthrotomy. Eleven hips were left in situ, and 12 were dislocated. The results were better when the hip was dislocated, and the inflammatory pulvinar in the acetab-ular fossa was debrided; the recurrence rate and prevention of secondary arthrosis were also more favorable.44 Gilbert et al have reported favorable results with arthrotomy in two patients with 5- to 7-year follow-up, and feel that synovectomy

Figure 14.5. Late disease with erosive secondary juxta-articular bone erosions.

Figure 14.5. Late disease with erosive secondary juxta-articular bone erosions.

relieves pain and may prevent or delay the progression of degenerative changes.41

As mentioned, the role of hip arthroscopy in the treatment of synovial chondromatosis has been based on treatment of the process in the knee. Only sporatic reports of arthroscopic loose body removal from the hip have appeared in the literature in association with the diagnosis of synovial chondromatosis, and no single large series has been reported.42-45 Witwity reported a case of arthroscopic removal of multiple loose bodies consistent with synovial chondromatosis.45 Okada reported a similar case in which multiple intra-articu-

lar loose bodies were identified and removed with suction lavage during hip arthroscopy.44 Mason et al have presented a series of 10 patients with histologically confirmed synovial chondromatosis of the hip managed initially by arthroscopy. One patient required open debridment for extracapsular disease, after arthroscopy revealed only one intra-articular loose body and numerous sessile intracapsular coalitions that could not be adequately resected. In the other 9 cases, partial synovectomy was performed. The majority of the loose bodies were non-ossified and adherent to the synovium or within the acetabular fovea and ligamenum teres. (Figure 14.6.) Chon-

ni f

Figure 14.6. Loose bodies adherent to the syn-ovium within the acetabular fovea.

Figure 14.7. Chondromalacia of the femoral head secondary to loose bodies.

Figure 14.7. Chondromalacia of the femoral head secondary to loose bodies.

dromalacia of the femoral head or corresponding acetabulum was present in the majority of patients. (Figure 14.7.) Grade I changes were seen in two patients (20%), and grade II changes were seen in six patients (60%). No patient demonstrated grade III chondromalacia. Mild anterior labral fraying was seen in two patients. The patients have been followed for an average of 34 months, at which time interval seven were asymtomatic, two had occasional mild pain, and one patient had symptomatic and radiographic recurrence of the disease at 2 years.

Although there are no long-term studies comparing the results of open synovectomy versus arthroscopic removal of loose bodies and partial synovectomy for synovial chondro-matosis of the hip, the experience of Mason et al favorably supports initial arthroscopic management of this condition.46 Ar-throscopy of the hip avoids the considerable surgical exposure and prolonged rehabilitation associated with open hip arthro-tomy and synovectomy. The arthroscopic procedure also does not obscure or preclude future surgical procedures, including repeat arthroscopic intervention. Because the arthroscopic syn-ovectomy is not complete, close clinical and radiologic follow-up is recommended for patients who undergo treatment by this method. If symptoms of recurrent disease occur and are secondary to intra-articular chondral or osteochondral loose bodies, repeat arthroscopy or formal open synovectomy can be selected for management. The surgical procedure chosen to treat recurrence should be individualized, taking into consideration information documented during the initial arthros-copy, the amount of visualization, percentage of synovium involved, arthritic changes, and also the time to recurrence.

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