Young male with history of ACL reconstruction about 1 year back shows good positioning an ligamentization of the the graft, normal PCL and menisci with subtle free fluid with too anterior placement of tibial tunnel, post bioabsorbable screws. Case submitted by Dr MGK Murthy, Mr Hari Om, Mr Sahadev Gupta.
Healthy Graft on MRI should be:
-Low signals if intact unimpinged graft
- Posterior to but not in contact with intercondylar roof
- T1 shows the structure better than T2 because of inherent heterogeneity on T2
-Tibial tunnel should not be too anterior
-Posterior cruciate ligament signals should not be gray/ heterogeneous
(A) Technical factors evaluation
On X –ray
-fractures/screws integrity or position/union of bony portion/tunnel placement/size of screw tunnel
On MRI
-Tunnel positioning (common failure is far too anterior placement at tibia )
-Tunnel widening(harmless)
-Graft integrity(heterogeneous signals sign of tear) other soft tissues evaluation
-Femoral insertion should be at intersection of blumensaat line (intercondylar roof)and extended line from posterior femoral cortex
-Tibial tunnel should be posterior and parallel to tibial intersection of blumensaat line
(B) Biological factors
-failed ligamentization—not well seen on MRI
-infection
-Arthrofibosis—seen as low signal nodule surrounded by fluid , anterolateral to tibial tunnel called Cyclops lesion on MR (consists of debris of remnant ACL and graft )
-infrapatellar contracture syndrome
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