Arthroscopic Synovectomy and Treatment of Synovial Disorders

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CHAPTER 21 Arthroscopic Synovectomy and Treatment of Synovial Disorders

Basic science

Synovial chondromatosis and synovial osteochondromatosis are the result of intrasynovial cartilage metaplasia, and it can cause the formation of multiple intra- and extra-articular loose bodies. These loose bodies may be primarily cartilaginous and associated with very little articular cartilage damage. With time, these loose bodies can ossify to variable degrees and result in progressive erosive changes near the hip joint proper. The cause and pathogenesis of PVNS remain unclear. The condition appears to be the result of a fibrohistiocytic chronic inflammatory or neoplastic response. It is associated with synovial proliferation (either diffuse or focal), joint effusion, and bony erosion with characteristic hemosiderin deposition within the synovial mass. Multiple loose bodies and PVNS of the hip are associated with more erosive and degenerative changes than those seen in the knee as a result of the more constrained nature of the hip joint proper. Rheumatoid arthritis is the most common inflammatory arthropathy that affects the hip joint. The initial pathology involves the inflammation of the synovium, which leads to the eventual destruction of the joint if left untreated. A septic hip results in microorganisms activating an inflammatory response that recruits polymorphonuclear cells. Bacteria, synovial cells, and polymorphonuclear cells release enzymes that facilitate the degradation of glycosaminoglycans and the subsequent loss of collagen; this ultimately results in the gross destruction of articular cartilage and the development of arthritis if untreated early during the course of its development.

History

The typical history is quite variable for patients who present with synovial disorders. Patients with synovial chondromatosis are more commonly males in the third to fifth decade of life. They will typically present with deep groin and deep lateral hip pain that is often mechanical in nature as a result of loose bodies. These patients will frequently report catching and locking that may be quite unpredictable and that can have variable asymptomatic periods. Over time, the symptoms may become more frequent, with associated rest pain that is not related to activity; this may be the result of progressive articular cartilage destruction caused by the mechanical effects of the loose bodies. Pigmented villonodular synovitis typically presents during the third and fourth decades of life, with no gender predilection. It is typically monoarticular with associated aching and rest pain and variable mechanical symptoms. A longer duration of symptoms is associated with progressive degenerative and erosive changes and with a presentation that is similar to that of degenerative arthritis at a relatively young age. Patients will note progressive stiffness and range-of-motion limitations. Septic arthritis of the hip has a similar presentation to septic arthritis elsewhere. There is usually no history of trauma, and there may be a preceding illness. Septic arthritis of the hip is more prevalent among immunocompromised hosts and patients with frequent bacteremic episodes. Patients will often present with fever, chills, rapidly progressive groin pain, and irritability with range of motion. Joint aspiration is usually diagnostic. Inflammatory arthropathies that affect the hip joint can lead to end-stage arthritis. Earlier during the course of the disease, however, patients will occasionally present with hip joint irritability as a result of synovitis that is unresponsive to oral or injectable medication. Occasionally, this may be the first presentation of a patient with an undiagnosed inflammatory arthritis.

Imaging and diagnostic studies

When evaluating a patient with symptoms that are consistent with hip joint pathology, plain radiographs should be obtained first. We typically obtain an anteroposterior radiograph of both hips with 2 cm to 4 cm between the pubic symphysis and the sacrococcygeal junction. A frog-leg lateral radiograph and a cross-table lateral radiograph with 15 degrees of internal rotation complete the initial series. Radiographic abnormalities may include arthritis, arthrosis, dysplasia, femoroacetabular impingement, and loose bodies. It has been reported that radiographs fail to diagnose loose bodies up to 50% of the time; this may be a result of the inconsistent calcification of these loose bodies and because they may be obscured by overlying structures. Large and multiple lucencies on plain radiographs are consistent with PVNS (Figure 21-1, A). Magnetic resonance arthrography (MRA) is the gold standard imaging technique for evaluating the hip joint proper. MRA has been shown to be very sensitive for labral tears and less accurate for chondral pathology. Filling defects can indicate loose bodies, as has been seen with synovial chondromatosis. As a result of hemosiderin deposition, pigmented villonodular synovitis is seen as a spotty or extensive low-signal area within proliferative synovial masses on T1 and T2 images; this condition is best seen on fast-field echo-sequence MRA images (see Figure 21-1, B). MRA imaging will typically reveal an effusion and variable degrees of synovitis in the setting of an acute septic hip; an aspiration can also be performed as part of this imaging. Chronic infection with associated osteomyelitis and adjacent abscesses should be ruled out in this setting before arthroscopic hip irrigation and synovial debridement are performed. MRA has important applications for imaging the rheumatoid joint. Bony erosions are visualized with MRA during the early stages of rheumatoid arthritis, and they are frequently detected before they appear on plain radiographs. MRA also detects bone marrow edema, which is another important feature that is associated with inflammatory joint disease and that may be a forerunner of erosion. Synovial membrane inflammation and hypertrophy are detected after contrast enhancement and also with the use of dynamic MRA techniques, which provide a noninvasive method for accurately measuring the inflammatory process.

Indications

Pigmented villonodular synovitis is best managed in its focal form. However, in diffuse PVNS it may not be possible to perform a complete synovectomy as the posterior and posterior inferior portions of the hip are difficult to access arthroscopically. In this situation we have performed a central compartment synovectomy (lunate fossa), followed by peripheral compartment (anteroinferior to posterosuperior) synovectomy (Figure 21-3). A T-capsulotomy and the addition of a postero-peritrochanteric portal allows for access to posterior capsular areas in some cases. A follow up MRI is obtained at 2 to 3 months and if residual disease is seen posteriorly, a limited open posterior approach to the hip can be performed to remove residual disease. Some nonarthroscopists would argue for open treatment primarily for diffuse PVNS.
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