Medial patellofemoral ligament reconstruction for recurrent patellar dislocation. Surgical procedures review

Tears of the MPFL are often considered the essential lesion of recurrent lateral patella dislocation. Cadaveric sectioning studies have demonstrated that the MPFL provides 50% to 60% of the soft tissue restraint to lateral translation, and the medial patello-meniscal ligament contributes 24%. Pathological conditions such as patella alta, trochlear dysplasia and an increased quadriceps angle from various torsional deformities of both the femur and the tibia can be associated with recurrent patello-femoral dislocation. All these conditions need to be corrected to restore the physiological biomechanics of the patello-femoral joint. Lateral retinacular release, proximal realignment and distal realignment are the most common procedures performed for this purpose. In recurrent patellar dislocation without any predisposing factor, all these non-anatomical surgical procedures have been used. They alter the pre-morbid patellar mechanics, and several studies reported inconsistent outcomes, recurrent dislocations, patello-femoral pain and arthritis in up to 40% of patients. Several reconstruction procedures of the MPFL with semitendinosus, gracilis, quadriceps tendon, adductor magnus, iliotibial band and synthetic grafts have been described. Semitendinosus tendon autografts are the most commonly used reconstruction construct. The different techniques require the fixation of the graft to the patella through bone tunnels loop, anchors, endobutton or sutured to the periosteal and fibrous tissue overlying the patella. The medial fixation to the femur is performed through bone tunnel and interference screw, endobutton, washer or through an osteoperiosteal tunnel under the adductor magnus. Most of the pre-mentioned techniques have shown acceptable medium-term results in the mean of subjective symptomatic improvement and low rate of recurrence in 85% to 93% of the involved cases. At present, there is no clear consensus as to the best method to reconstruct the MPFL. Several questions need to be resolved and in particular: the right position of graft insertion on the patella; the best fixation methods; at which degree of knee flexion the graft must be tensionated and fixed to avoid overtightening and then increased loads on the patellofemoral joint, which in the long term may result in degenerative joint disease; the right position of graft insertion on the femur since several studies have shown that the femoral attachment of the MPFL is not clearly identifiable. Biomechanical data show significant increases in medial patellofemoral contact pressures when MPFL grafts is misplaced as little as 5 mm. Incorrect graft placement accompanied by a short graft increases medial patellofemoral contact pressures by over 50%. In the future, a well controlled and standardised comparison of different surgical techniques is indicated, to assess whether a specific graft or technique is superior to the others.