In a paper we recently published, we observed that a non-anatomic femoral attachment in medial patellofemoral ligament reconstructive surgery does not always lead to a poor outcome. In fact, many patients with non-anatomic medial patellofemoral ligament reconstructions have an excellent clinical outcome not only at short-term, as some authors have shown, but also at long-term follow-up, as we have seen in our recently published study.
In this way, a member of our study group (Joan C. Monllau, MD) has analyzed a series of 36 medial patellofemoral ligament (MPFL) reconstructions (mean follow-up 37.6 months, range 27 months to 74.5 months) with gracilis tendon autograft using the adductor magnus tendon as a pulley for femoral fixation (non-anatomic reconstruction) and found good clinical results and without signs of patellofemoral osteoarthritis. In a previous cadaver study, we found the biomechanical behavior of the non-anatomic reconstruction using the adductor magnus as a pulley was similar to that of the anatomic reconstruction.
Failure vs excellent results after MPFL reconstruction
The relevant question we must ask is: Why will some non-anatomic MPFL reconstructions fail, whereas other non-anatomic reconstructions will have excellent results at long-term follow-up? This question has been answered in the paper we have just published. We have found it is the mechanical behavior of the graft that determines success or failure. The relevant fact is the graft is isometric between 0° and 30° (less than 5 mm of length difference between both knee flexion angles). Beyond 60° of knee flexion, the graft became progressively lax and isometry is lost.MPFL must function as a tether in early flexion without being tight at any point if the patella is centered in the groove, and this can be achieved through non-anatomic attachments. But in order to achieve this aim, we must do several proofs intraoperatively to evaluate the mechanical behavior of the graft, which is tedious and increases the surgical time.