Die Hydrojet-Synovektomie am Kniegelenk. In-vitro-Studie zur Machbarkeit eines neuen Synovektomieverfahrens

The selectivity of a water jet (WJ) is already used with clinical advantage in the surgery of liver, brain, kidney and herniated lumbar discs. The aim of the present study was to determine whether a WJ can be used for synovectomy without damaging the joint capsule. 60 human cadaver knee specimens (67 ± 14 years) were dissected into synovial samples. They were randomly assessed to four pressure groups (pw = 3; 6; 9; 12 MPa) and three jet surface angles (ß = 30; 60; 90°) The nozzle diameter was do = 0.12 mm, the stand off distance of the jet was s = 10 mm with a feed rate of vv = 2 mm/s. The acquired parameters were depth of the cuts, histological layer, and change of the samples thickness. There was a correlation of the cutting depth and the pressure (pw), whereas the jet-surface angle (3) showed no correlation. The synovial layer of the cut likewise correlated with the pressure. At pw = 6 MPa the stratum subsynoviale could be cut selectively without damaging the fibrous capsule. The increase of the samples thickness was caused by an interstitial oedema. The different mechanical properties of the joint capsule and the stratum subsynoviale lead to the selective cutting of the water jet. Since the joint capsule was not damaged, the feasibility of WJ synovectomy has been proven. The device can be used for synovectomy in parts of the joint that are not visible as well as in very small joints.