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Posterior Cruciate Ligament: Tibial Tunnel


- Tibial Tunnel:
    - saftey measures:
          - surgeons who do not perform this operation frequently should use flouroscopy for this tunnel;
          - apply Jacobs chuck for a preset distance on the guidewire to make it less likely for the wire to pass beyond posterior cortex (and injury NV structures);
          - consider making an extracapsular posterior medial incision which will allow surgeon's finger to be positioned between posterior capsule and N/V structures;
    - usually, the tibial tunnel will be anchored first, the graft pretensioned, and then the femoral tunnel will be achored;
    - cortical entry site:
          - incision: 5 cm longitudinal incision made below and medial to tibial tubercle;
          - some authors make this tunnel distal and medial to the ACL tibial tunnel site (approx 2 cm distal) when ACL reconstruction is required;
                  - other surgeons, will place the tunnel lateral to the tibial tubercle when ACL  reconstruction is required;
          - tunnel should begin well below tibial tubercle and is directed posteriorly so that it penetrates the posterior cortical surface 5-10 mm below joint line;
          - a steep incline may risk blowing out the posterior tibial wall;
    - articular entry site:
          - prior to drilling the tibial tunnel, the tibial insertion of the posterior capsule should be freed with a curette (use
                  postero-medial portal or the central portal);
          - tunnel should lie in center of PCL insertion, just lateral to midline in a depression between two tibial plateau surfaces (distal to level
                  of the articular surface at the distal portion of the posterior tibial edge);
          - note that the posterior cruciate ligament attaches 1-2 cm below the joint line;
                  - hence avoid the tendency to place the tunnel too close to the surface of the tibial plateau;
                  - for the ligament to function properly the tunnel must not exit too anteriorly;
          - hazards: popliteal artery injury:
                  - increasing knee flexion reduces, but does not completely eliminate, the risk of arterial injury during arthroscopic PCL reconstruction;
                          - maximum mean distances were noted at 100° of flexion in both the axial (9.9 mm) and sagittal (9.3 mm) planes;
                  - Proximity of the posterior cruciate ligament insertion to the popliteal artery as a function of the knee flexion angle.  Implications for posterior cruciate ligament reconstruction.  
    - it is important to smooth out the sharp edges of the tibial tunnel to facilitate graft passage and to prevent fraying of the graft fibers;
    - cautions:
          - if a concomitant ACL reconstruction is required
    - reference:
          A simplified approach to the tibial attachment of the posterior cruciate ligament.

Reducing the "killer turn" in posterior cruciate ligament reconstruction by fixation level and smoothing the tibial aperture.