Site-Specific Intraoperative Efficacy of Arthroscopic Knee Joint Synovectomy in Rheumatoid Arthritis

Purpose: To assess the intraoperative reduction of inflammatory infiltrates achieved by arthroscopic knee joint synovectomy in patients with rheumatoid arthritis (RA) with special regard to the removal site, using preoperative and postoperative synovial tissue (ST) samples. Type of Study: A histologic and immunohistochemical study. Methods: Eleven patients with treatment-refractory RA knee synovitis underwent arthroscopic synovectomy. In each patient, ST specimens were obtained immediately before and after synovectomy from 9 defined sites covering the whole joint. The samples were graded using an acute synovitis score (ASS; presence of polymorphonuclear neutrophilic leukocytes [PMN] and fibrin) and a chronic synovitis score (CSS; e.g., lining cell hyperplasia, presence of diffuse and lymphoid aggregates). Immunohistologic analyses were performed using 7 monoclonal antibodies directed against PMN, macrophages, and T-cell subsets (total of 1,584 preparations). Knee function was assessed after an average follow-up of 28 months by Lysholm score (modified by Klein and Jensen), Insall functional and knee scores, and Lequesne score. Results: Arthroscopic synovectomy led to an overall significant (P between .005 and .05) reduction of the acute inflammatory infiltrates (ASS) by 82.1%, but to a significant reduction of chronic inflammatory infiltrates (CSS) by only 62.5%. Accordingly, the density of PMN was reduced by 81.8%, whereas that of macrophages and different T-cell subsets was only decreased by ≤61.6%. With respect to the anatomic regions, a significantly (P ≤ .05) less marked reduction of inflammatory infiltrates was observed in the upper lateral and central recess, at the medial and lateral capsule, as well as at the femoral insertion of the anterior cruciate ligament. All knee joint scores showed a significant (P ≤ .01) improvement over preoperative values at follow-up. Conclusions: Arthroscopic synovectomy effectively reduces acute and chronic inflammatory infiltrates in patients with RA who have refractory synovitis of the knee joint (immediately after synovectomy) and improves knee function (28-month follow-up). However, the reduction of inflammatory infiltrates appears to depend on the anatomic region of the joint. Level of Evidence: Level III.