Medial Patellofemoral Ligament Reconstruction
The kneecap (patella) sits in a groove in front of the knee formed by the lower end of the thigh bone. The patella attaches the thigh-muscle tendon to the front of the shin bone. The kneecap moves to form the joint with the thigh bone, resulting in smooth bending and straightening of the knee.
During the motion of the kneecap, medial patellofemoral ligament aids to keep the kneecap in place acting as a leash. Traumatic injuries and athletic activities may result in patellar dislocation which is usually towards the outer side. The medial patellofemoral ligament is usually torn in the process.
Besides traumatic injuries or athletic injuries, some patients may be prone to kneecap dislocation owing to the increased laxity in their joints and ligaments, or due to tight structures (patellar retinaculum) on the outer side of the knee joint.
The torn ligament may heal naturally but usually heals in a slack manner causing instability of the kneecap. This may result in recurrent instability further aggravating the condition. Further, over time, the cartilage forming the patellofemoral joint may wear out leading to arthritis and degenerative changes.
The physician may diagnose the torn MPFL after eliciting a history of the pattern of injury, prior history of dislocations, and a thorough physical examination. The physical examination may include provocative tests to look for patellar mal-tracking and instability.
The physician may request radiological studies in the form of X-rays, CT scans to look for instability and malalignment of the extremity. Using an MRI the physician is able to clearly discern the various soft tissues including the MPFL of the knee joint.
Patients with two or more kneecap dislocations may be offered surgical management. Surgical management may also be offered to patients with a single episode of kneecap dislocation who may need surgery for other knee disorders. The MPFL reconstruction surgery may be safely offered in children and adults alike.
General or regional anesthesia in the form of spinal anesthesia may be used in MPFL reconstruction surgery. In general anesthesia, the patient sleeps during the surgery with the relaxation of all the muscles of the body. In spinal anesthesia, only the lower extremities are numb and relaxed, the patient is usually awake but maybe sedated to help the patient sleep.
The MPFL reconstruction surgery involves the use of a tendon graft to reconstruct the MPFL. The surgery is performed with the help of an arthroscope. Arthroscopic surgery involves the use of tiny (<1cm) incisions. Through the incisions, a tiny camera with a light source is inserted that displays live images on an external monitor.
Tiny minuscule instruments are inserted through another small incision and the surgeon uses the instruments to complete the surgery. The surgeon first uses the instruments to cut and release the tight patellar retinaculum on the outer side of the knee.
A tendon graft (semitendinosus) is harvested from one of the hamstring muscles. The tendon graft is then shaped to insert one end at the inner side of the kneecap. The other end is inserted at the inner side of the femoral condyle. The ends are secured using screws at both ends.
In patients with patellar maltracking due to mal-alignment of the bones, a tibial tuberosity osteotomy may be done. The osteotomy involves the placement of the tuberosity towards the inner side of the knee. The MPFL reconstruction surgery may also be performed in patients who have had prior surgeries in the form of debridement, or release of the retinaculum for kneecap instability.
The patient’s knee is placed in a brace after the surgery. The brace helps to keep the knee straight while walking and activities of daily living. Some pain and swelling are normal after the surgery and the patient may be prescribed pain medications. The patients are also advised regular icing and leg elevation to reduce postoperative swelling.
Patients are encouraged to do physical therapy for a quick return to the activities they enjoy. Usually 4-5 months post-op the patients are able to participate in sports activities.
Complications are rare but as with any surgery, there may be complications in the form of infection, bleeding, blood clot, failure of the graft, etc. MPFL reconstruction is a novel procedure to help patients with kneecap instability and MPFL tears.