Medial Patellofemoral Ligament Reconstruction (MPFL)
Patellar instability is a very debilitating condition. The instability can be acute, such as after a traumatic dislocation, or it can be more chronic and related to how your bones formed. Some people have an anatomic propensity to dislocate their patella, either from being knock kneed, having a shallow trochlea (groove where the patella sits), having a tibial tubercle (the place where the kneecap tendon attaches on the shin bone) that is too far to one side, or a combination of everything.
A one-time patellar dislocation without cartilage damage or a fracture can typically be treated without surgery. Surgery is needed for instability that has been recurrent and/or that has failed a course of physical therapy with bracing, taping, and muscle strengthening. Often times, we also focus on getting your gluteal (butt muscles) stronger, which helps with your gait pattern. You may also have flat feet, which can predispose you patellar issues. In this case we may also recommend a set of orthotics.
X-rays are typically taken in the office to look at your bony anatomy. The x-rays are very specialized views taken at certain knee angles. In addition, we also obtain an MRI or CT scan to look at your cartilage and to take special measurements of your bones. One of these measurements is called the Tibial Tubercle Trochlear Groove (TTTG) measurement. This helps us to decide whether we need to do surgery near the patellar tendon attachment on the tibial tubercle (the attachment on the shin bone) or closer to the side of the patella. This article talks about the surgery done to the inside of the kneecap, called a Medial Patellofemoral Ligament (MPFL) reconstruction. There is another article on surgery closer to the tibial tubercle called an AMZ or Fulkerson osteotomy. Occasionally we do both of the procedures together.
The surgery for a MPFL reconstruction is typically either an outpatient or a 23 hour stay (i.e. overnight) procedure. You will receive a general anesthetic, in addition to a nerve block to your operative side. The nerve block is placed by the anesthesia service and allows you to wake up relatively pain-free. The block lasts for approximately 12-18 hours, after which you can start easing into your pain medication.
You are positioned flat on the operating room table, with all of your extremities carefully padded. We use a tourniquet during the procedure to help with the bleeding and with visualization. After performing a “time out”, where we verify the operative site, your leg is cleaned and sterilely draped. We typically perform an arthroscopy of the knee to visualize the kneecap and get an idea of how it is tracking and where it is dislocating/subluxating. There can also be other cartilage issues in the knee that are addressed during the arthroscopic portion of the procedure. Once this portion is completed, the rest of the operation is done open.
For the open part of the procedure, we make an incision at the inner side of the kneecap. We dissect down through the muscle layers until we get to the level where the MPFL ligament should be. We assess whether any portion of the ligament is still intact. If this is a very chronic problem, the ligament may be so stretched that it is not able to be used. Occasionally, we can find the ligament and reattach it back to the kneecap with sutures.
If the full ligament reconstruction needs to be done, we make a secondary incision down by the inside portion of the knee. Using fluoroscopy (x-ray), we find the exact location where the ligament previously inserted on the femur. We use a tendon graft, either your own tendon or typically a donated tendon graft as the new MPFL. There are various configurations of tendon grafts, but most of the time we make the tendon into a Y-shape. The bottom part of the Y-shaped tendon is fixed to the femur bone with a screw. The graft is then tunneled underneath the skin up to the patella, and with the kneecap in a reduced position, the graft is fixed to the kneecap with wither suture anchors or through another set of bone tunnels.
The motion of the knee is checked and we also confirm that the patella is stable. Once the incisions are closed, the leg is placed in a knee immobilizer, which you will use for support for the first 6 weeks after the surgery. It is very important that you stay in the immobilizer except for the specific knee motions you are taught.
Sometimes we move the knee very quickly after the procedure, but other times we keep you in the immobilizer for a couple of weeks prior to even moving the knee. This will be explained to you after the procedure and very specific instructions will be given to you and your therapist.
Once your pain is under control, you are eating and keeping food down, and you are medically stable, you can be discharged home. You will get a full set of instructions of Do’s and Don’ts. Basically make sure to keep your incision clean and dry. No showering until your postoperative visit. If you have any questions on what you should be doing or not doing to your shoulder, make sure to ask your surgeon or the nurses/residents. You will be seen in the office for a check up and to remove any staples or sutures in 7 – 10 days after surgery. You will also be given a pain medication prescription. Please take the pain medication as directed. Eat a healthy diet and get plenty of rest. Also remember that ICE is a form of pain relief and you should ice the knee regularly.
Typically you are in the immobilizer for 6 weeks after surgery but are coming out of the sling for very prescribed movements that you will be taught. Most of the movements can be done without a therapist, and formal physical therapy starts at approximately the six week mark. We want your leg to be straight when not doing any exercise, which includes at night. In order to help with getting the leg out straight, we do not want any pillows under the knee, only under the calf and ankle. In this way, when you elevate the leg, gravity helps to pull the leg out straight.
Once or twice a day, we want you coming out of your brace to bend the knee. The knee bending will only be to 60 degrees of motion. The first couple of times you attempt to bend the knee, it will be stiff. Take your time and take things in “baby steps”. If you can only get a couple of degrees of knee motion, do what you can and come back at a later time to get a little bit more. If you do it in a step-wise fashion, you will see that your knee motion will come back nicely.
You will be seen in the office for regular visits to monitor your progress. Full healing from this type of surgery is approximately 5 – 6 months. We hope this provides a bit more insight into your surgical procedure for an MPFL reconstruction. As always, if you have any questions, please contact our office at 248-988-8085.