Light and scan electron microscopic analysis of cyclops syndrome: etiopathogenic hypothesis and technical solutions

The loss of range of motion after anterior cruciate ligament (ACL) reconstruction is one of the most common and most challenging complications of this kind of surgery. Recently, an intercondylar notch fibrous proliferation, called cyclops syndrome because of its arthroscopic appearance, has been identified as one of the specific causes of loss of extension. The incidence of cyclops syndrome is 2%-4% [17, 18], but there is still no understanding of its etiology. We speculate on the etiology and suggest some technical solutions to reduce this complication. In 180 patients submitted to arthroscopic ACL reconstruction with patellar tendon, we observed in 4 cases a fibrous nodule adherent to the neoligament that caused a loss of extension between 12 degrees and 17 degrees. In all cases, arthroscopic removal of this nodule solved completely the loss of articular motion. The nodules were subjected to light and scanning electron microscope evaluation. We observed numerous, newly formed vessels in all 4 nodules. These vessels were made up of hyperplastic and hypertrophic cells and were surrounded by bundles of disorganized fibrous tissue. No inflammatory cells or bone or cartilaginous tissue was observed. We hypothesize a microtraumatic genesis for cyclops syndrome. Repeated microtraumas expose the graft collagen fibers, which can lead to productive inflammatory process and thence to the formation of the cyclops nodule. We suggest some technical solutions to avoid graft impingement with the notch and with the tibial bone tunnel.