Medial patellofemoral ligament (MPFL) reconstruction
Medial patellofemoral ligament reconstruction is a surgical procedure indicated in patients with more severe patellar instability. Medial patellofemoral ligament is a band of tissue that extends from the femoral medial epicondyle to the superior aspect of the patella. Medial patellofemoral ligament is the major ligament which stabilizes the patella and helps in preventing patellar subluxation (partial dislocation) or dislocation. This ligament can rupture or get damaged when there is patellar lateral dislocation. Dislocation can be caused by direct blow to the knee, twisting injury to the lower leg, strong muscle contraction, or because of a congenital abnormality such as shallow or malformed joint surfaces.
Medial patellofemoral ligament reconstruction using tissue grafts is done by following the basic principles of ligament reconstruction such as:
- Graft Selection : Strong and stiff graft should be selected; the native ligament has a strength approaching 200 Newtons, and most grafts are many-fold stronger.
- Location : The graft should be located anatomically.
- Correct Tension : The tension set in the graft should be appropriate; this is critical, because a graft left too loose does not restore stability, but a graft fixed too tightly can cause patellofemoral pain and even accelerate chondral wear due to excessive pressure.
- Secure Fixation : Stable fixation of the graft should be achieved.
The surgical procedure of medial patellofemoral ligament reconstruction involves the following steps:
Graft Selection and Harvest: Your surgeon will make a skin incisions over your knee at the medial epicondyle and the medial aspect of the patella (knee cap). The underlying subcutaneous fat and fascia are cut apart to expose the anatomic landmarks of the native MPFL
Location of the femoral isometric point: The graft should be placed anatomically to prevent it from overstretching and causing failure during joint movements. The origin on the medial femur is referred to as Schottle’s point, named after the surgeon who best described the anatomy. The patellar insertion is broad, cover the proximal and middle thirds of the medial patella. Suture anchors and femoral socket are prepared.
Correct Tension : The tension is set in the graft tension should be appropriate enough to control lateral excursion while allowing physiologic translation of the patella side-to-side.
Secure Fixation : The tendon is sutured into the medial patella attachment with suture anchors, and fixed in the medial femoral socket with an interference screw.
A knee brace should be used, locked in extension, with non-weightbearing for the first 3 weeks, followed by weightbearing as tolerated with the brace locked in extension for the following 3 weeks. The brace is weaned at 6 weeks postop. If surgery is performed on the driving leg, no driving is recommended for the first 6 weeks postop. A rigorous physical therapy protocol is expected and includes twice weekly therapy with ‘homework’ exercises the remaining days of the week. A gradual incremental progression guided by the physical therapist is essential, as insufficient effort could result in a stiff, weak knee, and excessive activity or stress (weaning brace or crutches too soon) could compromise the graft at its most fragile state.
Frequently Asked Questions
- What is the best technique for MPFL reconstruction?
- More than most orthopedic procedures, there are numerous variations to MPFL reconstruction that produce effective results and restore patellar stability. Dr. Rice’s current technique includes an allograft semitendinosis tendon, which is substantially stronger than the native MPFL. This is secured at the upper and middle thirds of the medial patella with a pair of 1.8mm all-suture anchors. These anchors are tiny yet strong, with secure fixation yet minimizing the chance of a stress riser in the patella compared to larger anchors or tunnels, which in a worst-case scenario could lead to patella fracture. The other end of the double stranded graft is then docked into a socket on the medial femoral condyle anatomic origin (known as Schottle’s point) with a biocomposite interference screw. These implants are non-metallic and invisible on xray, and never require removal.
- How effective is MPFL reconstruction at restoring stability to the knee? What chance do I have of dislocating my patella again?
- MPFL reconstruction surgery is reliably effective. Chances of dislocating after surgery are typically 1-3%, meaning 97-99% of patients will never dislocate again after surgery.
- When can I return to sports after MPFL reconstruction?
- o Return to sport varies based on age, activity level, fitness level, compliance with therapy, effort, and an individual’s innate healing capacity, among other factors. Most athletes return to running/jumping/cutting sports approximately 6 months after surgery.
- Should I choose an autograft or allograft tendon for my MPFL reconstruction?
- Abundant research on MPFL reconstruction surgery has not revealed a meaningful difference between autograft and allograft tendon. Because there is some morbidity to harvesting a patient’s own hamstring tendon, and no clear benefit of autograft compared to allograft, Dr. Rice prefers allograft for this surgery. Across orthopedic sports medicine research, extraarticular reconstruction (rebuilding ligaments outside the joint capsule) often demonstrate comparable results between autograft and allograft. This is in contrast to intraarticular tendon reconstruction, with the classic example being ACL reconstruction, of which Dr. Rice is a strong proponent of autograft tissue.
- Do I need an osteotomy surgery (for example, tibial tubercle osteotomy) with my MPFL reconstruction surgery?
- Probably not. Most patients considering MPFL reconstruction do not need an osteotomy, but this is dependent on several variables that Dr. Rice carefully analyzes on an individual basis, including but not limited to the tibial tubercle-trochlear groove distance, or TT-TG distance. When the TT-TG is 20mm or greater, tibial tubercle osteotomy (TTO) will typically be added to medialize the tibial tubercle and decrease that distance to under 15mm, usually closer to 10mm. A native TT-TG under 15mm is reassuring that no osteotomy is indicated. 16-19mm is a ‘gray zone’ with other factors like trochlear dysplasia considered, but typically these patients are best served with isolated MPFL reconstruction. The rare patient that has failed an anatomic, properly performed isolated MPFL reconstruction would likely have a TTO added in a revision setting, for the sake of using all the procedural ‘tools’ available to restore stability.