ARTHROSCOPIC VISUAL-FIELD MAPPING AT THE PERIPHERY OF THE MEDIAL MENISCUS - A COMPARISON OF DIFFERENT PORTAL APPROACHES

The posteromedial compartment, particularly the posterior horn of the medial meniscus, has been shown by many investigators to be a common s ource of diagnostic errors in knee arthroscopy when access is limited to anterior portals. To better understand the anatomical basis of this apparent technical limitation, we quantified the visible versus the ' 'blind'' zones of the posteromedial meniscal periphery present when us ing the following arthroscopic approaches in six fresh knee specimens: (a) direct anteromedial frontal view with a 30-degrees arthroscope (A M-30-degrees); (b) anterolateral portal, 30-degrees arthroscope, trans notch view (AL-30-degrees); (c) anterolateral portal, 70-degrees arthr oscope, transnotch view (AL-70-degrees); (d) central portal, 70-degree s arthroscope, transnotch view (C-70-degrees); and (e) posteromedial p ortal, 30-degrees arthroscope, direct rear view (PM-30-degrees). The A M-30-degrees approach visualized only the anterior 50% or less of the total superior meniscosynovial junction length, in all knees. The AL-3 0-degrees, C-70-degrees, AL-70-degrees, and PM-30-degrees portal appro aches visualized the posterior most 16.4%, 24.2%, 31.6%, and 54.9% of the upper meniscal rim, respectively. In conjunction with the AM-30-de grees visual field, the PM-30-degrees approach provided the most compl ete overall visualization of the superior meniscosynovial junction, le aving a mean blind zone of only 8.4% (12 mm) between the anterior and posterior visual fields. The AL-30-degrees, C-70-degrees, and AL-70-de grees approaches left significantly greater portions (means of 47%, 39 .1%, and 31.7%, respectively) of the meniscal rim unvisualized.