PCL Reconstruction-MRI

Teaching points by Dr MGK Murthy

Isolated PCL reconstruction is less common than ACL (combined  cruciates   is also more common). Two  basic types BTB (where patellar tendon is used)  and Hamstrings graft (gracilis and semitendinosis) are popular. MR techniques would benefit by Oblique sagittal and oblique coronal  additions. MR susceptible artifacts are more than in ACL reconstructions because of proximal location of tibial fixation (particularly in Tibial inlay reconstruction).

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MR  appearance depends on duration :

 (a) 3-4 months  post surgery  graft is avascular and shows low signal on all sequences.

(b) 4-8 months Remodelling, Resynovialization  (called Ligamentization) occurs with T2 bright signals  of edema  in inter bundles location (anterolateral vs Posteromedial) (NOT to be  mistaken  for tear ) (T2  bright signals  less than fluid  bright signals)

 (c)1-2 years post surgery resembles native PCL. Arthrofibrosis more than in ACL reconstruction, and in fact is somewhat desirable, as it holds the ligament in place by reducing movements (focal (at Hoffa’s pad level) more than Diffuse variety)

Tunnels delineation (scanty literature exists ) .

(a)  Femoral point (F1) desired to be  in Zone I of Blumensaats line 4 quadrants (I-IV).  F2 point is medal wall of intercondylar notch  

(b)  Tibial point (T1)= Draw Maximum tibial plateaus AP dimension lines (both medial and lateral)(axial images)  and perpendicular  from the intersecting point of those lines  .  Ideally, Tibial tunnel point should be minimally medial to this.

Rest of the findings to look for include  identification  of   Ganglion cyst formation & loosening of graft in  the tunnel (referred to as Windshield wiper effect ) associated  findings and  infections etc