Cyclops and cyclopoid formation after anterior cruciate ligament reconstruction: clinical and histomorphological differences

Abstract

Prospectively, 119 patients were pursued clinically and by follow-up-arthroscopy for the occurrence of a "cyclops syndrome" after ACL reconstruction with a patellar tendon autograft, augmented by LAD. Twenty-one patients showed nodular formations. Ten of these (group 1) developed early clinical evidence of a "cyclops syndrome" with a mean extension deficit of 19 degrees before follow-up-arthroscopy, on average 5.9 months after the index operation. The nodular formations found and excised during débridement had a hard consistency. Histomorphological undecalcified microtome section evaluation of six specimens revealed fibrocartilagineous tissue with active bone formation in the center. The other 11 patients showed no clinical symptoms (group 2). A similar but soft nodulous scar formation was detected at follow-up-arthroscopy, on average 9.5 months after the index operation. Histomorphologically these so-called "cyclopoid" formations were only built-up fibrocartilagineous islands surrounded by granulation tissue. Neither remnants of tendon graft fibers nor old bone particles were found in specimens of either group. It can be concluded that both the hard cyclops and the soft "cyclopoid" are de novo scar formations.

Cyclops lesions detected by MRI are frequent findings after ACL surgical reconstruction but do not impact clinical outcome over 2 years

“…They found that in 2% of the patients a second surgery was needed in order to treat cyclops lesions, however, the prevalence of cyclops lesions in patients without severe loss of knee extension was not assessed. Previous studies based on second-look arthroscopy found an incidence of cyclops lesions between 14% and 21.5% [10, 15, 29]. Nevertheless, in these studies follow-up was only performed once, with inhomogeneous follow-up time points ranging from 8 and 36 months [10] and 14 to 70 months [29] after the ACL reconstruction.…”

“…The reason why cyclops lesions can cause loss of extension needs further investigation: a wide variety of tissue may contribute to the formation of cyclops lesions, including fibrous tissue, fibrocartilage, bone and fat. One possible explanation may be that “harder” variants of lesions could represent a mechanical obstacle at the end of the knee extension, whereas “softer” variants, such as cyclopoid scars, do not affect the range of motion, as shown by Muellner et al [15]. However, other studies did not find any cartilage or bone tissue in cyclops lesions causing limited knee extension [10, 14].…”

“…Although the origin of the fibrous tissue is uncertain, it has been suggested that the formation of the cyclops lesion is stimulated by debris from the drilling and preparation of the tibial tunnel [8, 11]. Even though this lesion was previously defined as localized arthrofibrosis [6, 12, 13], histologically the cyclops lesion is composed of disorganized fibrous connective tissue with a central region of granulation tissue and newly formed vessels [8, 10, 14, 15]. Repeated microtrauma may expose the graft collagen fibres, which can lead to productive inflammatory processes and to the formation of a cyclops nodule [14].…”

MR Imaging of Complications of Anterior Cruciate Ligament Graft Reconstruction

“…Cyclops lesions typically are small, with average sizes ranging from 10 to 15 mm (19). Two histologic types have been identified: true "hard" cyclops nodules and "soft" cyclopoid scars (20). True cyclops nodules contain osseous or cartilaginous tissue and are more prone to entrapment (cyclops syndrome).…”

Komplikationen und Probleme der VKB-Ersatzplastikoperation mit Patellarsehnendrittel in arthroskopischer Press-Fit-Technik - Analyse von 1043 Fällen

“…Ein Abwarten bis zum Zeitpunkt der Metallentfernung ein halbes Jahr nach Rekonstruktion ist nicht sinnvoll. Für endgradige leichte Bewegungseinschränkungen waren vor allem die schon in der Literatur bekannten Zyklopstumoren, Notchimpingement und Verwachsungen verantwortlich[9,18]. Interessant ist hier, dass bei 9 Patienten keine Ursache für das endgradige Bewegungsdefizit im Rahmen der Kontrollarthroskopie gefunden werden konnte.…”