The knee cap or patella is a marvelous and complex structure. Held over the knee joint by soft tissue structures, it moves or “tracks” up and down with knee motion. Anatomists are still exploring and learning how the patellar tracking mechanism really works. Understanding normal patellar anatomy and kinematics (movement) will help surgeons repair and restore this part of the knee when injury leads to chronic, painful patellar dislocations like you have.
Studies have now shown that this soft tissue structure blends with a portion of the medial patellofemoral ligament (MPFL). The two structures work together to keep the patella in the center of the knee as it starts tracking during knee flexion. Right now, there is no agreement or consensus on the best way to reconstruct a torn medial patellofemoral ligament (MPFL) in order to restore patellar stability.
The use of suture anchors, bone graft material, and making tunnels through the bone to attach soft tissue grafts are currently under close investigation. In fact, a new surgical technique for the problem of recurrent patellar dislocation has recently been developed and reported on.
The new Y-graft technique is designed to help restore the knee to as close to normal anatomy after recurrent dislocations. Early results show that it has the strength needed to hold the kneecap in place during movement requiring patellar tracking up and down over the knee. The Y-graft outperformed the more commonly used C-graft technique.
The basic difference is in the shape of the graft tissue and the fixation sequence. Fixation sequence refers to how and when the two ends of each graft are attached. For example, the C-graft procedure attaches both ends to the femur (lower leg bone) at the same time. Tension on the two ends of the graft is set at the same time.
The Y-graft technique allows the surgeon to apply tension to the separate ends one at a time with the knee in zero degrees of flexion (i.e., straight) and then at 30 degrees of flexion. This separate graft tensioning helps mimic the more normal anatomy (alignment) and kinematics (movement). A special table summarizing the differences between these two fixation methods is also provided to help surgeons understand how the two techniques compare.
Results comparing two patient groups with chronic, painful patellar dislocations (one group had the Y-graft, the second group had the C-graft) were measured using clinical tests and CT scans. Knee function, patellar stability, and patellar angles were the main outcome measures. With regular follow-up for two years, they found that the Y-graft did provide better knee function compared with the C-graft. And the Y-graft (double-bundle technique) restored normal patellar tracking much better than the C-graft (single-bundle technique).
Further follow-up is needed now because recurrent patellar dislocations tend to develop more as time goes by. We don’t know if this was one of the ways your surgeon suggested for you. But knowing a little bit about each method can help you better understand what your surgeons are recommending and what might work best for you.