- Discusison:
- traditionally used for the inflow cannula;
- note that with modern pump equipment, the inflow canula is generally no necessary;
- technique:
- place this cannula under direct visualization so that the cannula will not be placed under a plicae or into a thick wad of synovium;
- note that repeated attempts to enter the joint will create additional openings into the joint which may allow extravasation of fluid;
- skin and capsular incision should be as small as possible so that fluid does not extravasate into the subQ tissues or out of the skin;
- traditionally this portal is placed several cm above the patella in line with the medial edge of the patella;
- deep palpation will reveal a nice soft spot and will ensure that the incision is medial to the quadriceps tendon;
- make the incision thru skin only skin the vastus medialis will readily separate as the blunt trocar is passed into the suprapatellar pouch;
- further, deep insertion of the knife often stirs up unnecessary bleeding, and creates a passage into the knee joint which may not always be followed by the trocar;
- insert trochar beneath the vastus medialis and aim it distally and laterally to a point just superior to and lateral to the femoral trochlea;
- a gentle twisting motion facilitates entry of the trocar into the pouch;
- diffulty w/ insertion may indicate that the trocar has not been inserted deep enough (below the vastus);
- disadvantage: patients will often have postoperative tenderness over the portal site;
- alternative site is located just below the vastus medialis obliqus with the knee flexed 90 deg;
- this ends up being just superior to the intersection of the superior and medial borders of the patella;
- this location allows the cannula to be placed either in the medial gutter or in the trochlea (which ever allows the best inflow);
- this portal site is associated w/ minimal postoperative tenderness and allows accelerated rehabilitation because the vastus medialis has been violated;
- maximizing inflow:
- once this portal has been established, determine whether hypertrophic synovium or the fat pad may interfere with inflow down into the medial and/or lateral compartments (as well as the notch);
- if this is the case, then shave away the obstructing soft tissue until visualization of the medial and lateral compartments is not difficult
Technical note: Proximal superomedial portal in arthroscopy of the knee.