The medial patellofemoral complex, consisting of the medial patellofemoral ligament (MPFL) and the medial patellotibial ligament, is the main stabilizer of the patellofemoral joint. Since it has been shown that rupture of the MPFL is the main pathological consequence of patellar dislocation and biomechanical studies have demonstrated that the MPFL is the main passive restraint against patellofemoral instability (PFI) and lateral patellar displacement, reconstruction of the MPFL has become a widely accepted technique for restoration of patellofemoral stability. Therefore, numerous techniques for reconstruction of the medial patellofemoral complex have been described with promising clinical results. However, since it is known that a nonanatomic reconstruction of the MPFL can lead to nonphysiologic patellofemoral loads and kinematics, the goal of surgical intervention must be an anatomic reconstruction. There have been multiple studies to evaluate the femoral insertion of the MPFL. Based on these anatomic, biomechanical and radiologic findings, it is now possible to avoid the complications of increased patellofemoral pressure that is associated with nonanatomic (too anterior/proximal) fixation of the graft.

The Anatomic Double Bundle MPFL Reconstruction technique replicates the native shape of the MPFL and provides outstanding flexion and extension. The Double Bundle technique also effectively limits rotation throughout the range of motion, minimizing postoperative instability. The technique, if accomplished directly and anatomically, may also provide for more aggressive rehabilitation protocols and earlier return to activity. As mentioned above, an important determinant of a successful outcome of MPFL reconstruction is the proper position of the femoral fixation of the graft, and our technique incorporates the use of a femoral template to ensure proper placement of the graft in the femur. This position provides a static fixation point that equalizes the tension across the graft in flexion and extension, thus minimizing the stresses across the patellofemoral joint.

Pathomorphology of Patellofemoral instability (PFI) Overview

The pathomorphology of Patellofemoral instability (PFI) is dependent on different static and passive factors, such as alignment of the lower limb, dysplasia of the trochlea, and functionality of the MPFL. The patella is primarily stabilized by the medial patellofemoral complex from full extension to approximately 20° of flexion, and has no bony guidance, thus forcing the MPFL complex to bear the load of restraint against the lateralizing vector of the quadriceps muscle.
At about 20° of flexion the patella should engage into the trochlear groove, where the lateral trochlear facet is providing the static stabilization against patellar lateralization. The trochlea provides stability up to 60- 70° of flexion, where the patella begins engaging into the notch. In cases of trochlear dysplasia, the patella cannot be guided properly and dislocation of the patella can occur more easily. Very seldom, there are cases where the patella does not engage the notch in greater than 70° of flexion, and instability occurs. This can occur in cases of a valgus deformity or internal rotation of the distal femur, where the trochlear groove and the notch are positioned medially and the patella cannot engage. Chronic patellar dislocation is often seen in these cases with the patella tracking on the lateral condyle during the entire range of motion. In these cases, a realignment procedure should be considered