Recurrent patellar dislocation after medial patellofemoral ligament reconstruction.

We report on three cases of recurrent lateral patellar dislocation following a medial patellofemoral ligament (MPFL) reconstruction for patellar instability. In all three cases, an isolated MPFL reconstruction was performed with a double autogenous gracilis graft. The patellar fixation was done through bone tunnels. All three patients presented with a definite moderate to severe traumatic episode resulting in a recurrent patella dislocation and a transverse avulsion fracture at the medial rim of the patella. All three were treated by an open reduction and internal fixation with good results. No complication or recurrent dislocations occurred. We suggest that this complication is caused by the original underlying pathology such as dysplastic trochlea, abnormal TT-TG, patella alta and hyperlaxity, resulting a greater reliance upon the reconstructed MPFL for patellar stability. When subjected to a severe stress, the graft, which is stronger and stiffer than the original MPFL, will cause a fracture through the medial edge of the patella. This weak area results from the previous drill holes, which act as stress risers.