[A clinical study of arthroscopic cystectomy on popliteal cysts associated with rheumatoid arthritis]

We performed a prospective study of arthroscopic cystectomy on popliteal cysts associated with rheumatoid arthritis.

We performed arthroscopic cystectomy on three patients, four knees, and an open excision of a cyst on one patient, one knee, who had pain and swelling in the popliteal region. Of these five rheumatoid knees, three were grade I on the Larsen radiographic scale, one was II, and one was III. OPERATIVE METHOD: First, we performed synovectomy on the posterior compartment using a multi-portal approach. Second, we confirmed a small communication hole between the posterior compartment and the Popliteal cyst after the synovectomy with an angled arthroscope through the anterior compartment. Third, we enlarged the communication hole and performed a cystectomy (the excision of the membranous septum and the contents of the cyst) from the inside by using a motorized shaver. Finally, we performed a synovectomy on the anterior compartment. The follow-up period ranged from 1 year 6 months to 3 years, 4 months (the mean was 2 years, 4 months).

We assessed the results using objective oriteria based on the evaluation of swelling, pain and subjective criteria based on the evaluation of the range of motion of the knee and confirmation of the disappearance of the cyst using MRI.

We had good results in this study. All the four knees on which the arthroscopic cystectomy was performed had a reduction of pain and swelling right after the operation. The absence of the cyst was verified using MRI. We had no patient whose ROM was aggravated. However, synovitis and popliteal cysts reoccurred in one knee after the open excision (this case had the vasculitis, larsen grade III radiographically, and severe rheumatism).

The recurrence rate of the popliteal cyst was very high (over 50%) when a cyst was performed open exision using a posterior approach. Open synovectomy of an anterior compartment needed the manipulation in several cases because of limited knee movement. We had a reduction in pain and a disappearance of the cyst right after operation. Further more, there was no restriction in ROM resulting from this operative method.

Arthroscopic cystectomy is a superior procedure for treating the popliteal cysts associated with rheumatoid arthritis.