Dynamic Medial Patellofemoral Ligament Reconstruction in Patellar Instability: A Surgical Technique

Abstract

Background:

Patella instability with recurrent dislocations is a result of various pathologies, for example, patella alta, trochlea dysplasia or medial patellofemoral ligament (MPFL) rupture. The recurrent dislocation rate of conservatively treated chronic patellar instability is high; therefore, it is recommended to manage it surgically. This video presents a new operative approach to stabilize the patella in a dynamic MPFL reconstruction, which addresses the most common complications occurring in static reconstructions: malpositioning and overtensioning the graft.

Indications:

Surgical indications for the new dynamic procedure mirror the indications for static MPFL reconstruction. This is MPFL insufficiency (patella instability in the first 30° of knee flexion), which is most frequently seen in recurrent lateral patella dislocations. Moreover in very rare cases of first patella dislocation with a patellar instability severity score equal or higher than 4.

Technique Description:

The dynamic MPFL reconstruction consists of 3 steps: First, detaching and mobilizing the gracilis muscle at its anatomical insertion. Second, redirecting the freed gracilis muscle to its new patellar insertion. Third, reinserting the gracilis muscle at the patella.

Results:

The dynamic MPFL reconstruction has the advantage of lesser risk of overtensioning and malpositioning the graft. The insertion point of the MPFL surrogate is easier to locate, and the patella is dynamically stabilized through reflectory gracilis muscle contraction. Compared with the static reconstruction, only one instead of 3 holes have to be drilled and only 1 interference screw has to be placed, thus shortening the surgery time. From a theoretical biomechanical perspective, the dynamic tensioning is superior to the static procedure. The few accomplished studies published so far by Becher et al and Ostermeier et al show good or better functional results (Kujala, Lysholm, Tegner scores) with the dynamic MPFL reconstruction, yet higher evidence studies need to be performed.

Conclusion:

Dynamic MPFL reconstruction appears to be a simpler and more effective surgical technique for MPFL reconstruction. Because of its novelty, high evidence studies assessing long-term therapeutical outcomes are still lacking and need to be conducted in order to compare it conclusively with the static procedure.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

Hi, my name is Anna Bartsch, and I am an orthopedic surgeon at the University Hospital of Basel, Switzerland. I want to show you together with my colleagues Dr. Christian Egloff and Dr. Sebastian Müller the surgical technique of the dynamic medial patellofemoral ligament (MPFL) reconstruction.

We have no conflicts of interest to disclose. Before starting the practical demonstration, we will provide you with some general background information concerning the MPFL surgery. Starting at about minute 3:00, we are going to demonstrate to you the individual steps of the procedure, and we will conclude with some comments placing the dynamic MPFL reconstruction into context of current state of treatment of MPFL rupture.

Patella instability with recurrent dislocations is a result of various pathologies, for example patella alta, trochlea dysplasia or MPFL rupture. The recurrent dislocation rate of conservatively treated chronic patellar instability is high; therefore, it is recommended to manage it surgically. Varieties of surgical procedures were developed, addressing the underlying pathologies. Today, we are going to show you in particular the surgical treatment method of dynamic MPFL reconstruction using the gracilis tendon according to Becher et al.

This dynamic surgical technique addresses the most common complications occurring in static reconstruction, which are malpositioning and overtensioning of the graft. The major advantages are that the insertion point of the MPFL surrogate is easier to locate, and the patella is dynamically stabilized through reflectory gracilis muscle contraction. The retropatellar pressure is therefore adaptable to the gracilis muscle force.

Indications for the dynamic MPFL reconstruction correspond to the indications for static MPFL reconstruction, which is in selected cases of first patella dislocation, namely when the patellar instability severity score is equal or higher than 4. Main indication is recurrent lateral patella dislocation. Very often, we can find multiple pathologies combined in patients, resulting in patellar instability, and all have to be addressed. In this video however, we will only present the surgical technique of the dynamic MPFL reconstruction.

Contraindications mostly arise from the intraoperative use of the gracilis tendon and include its absence, for example due to prior harvest in anterior cruciate ligament (ACL) reconstruction, ischiocrural muscle deficiency, neurogenic instability, or joint infection. Prior to surgery, the standard medical history, clinical examination and radiograph images should be collected. To fulfill indication criteria and detect concomitant pathologies we generally conduct a x-ray and a magnetic resonance imaging (MRI) of the knee.

We can divide the surgery into 3 steps: detaching and mobilizing the gracilis muscle at its anatomical insertion, redirecting the freed gracilis muscle to its new patellar insertion, and reinserting it at the patella.

Before starting the surgical procedure, make sure you have ready an arthroscopy set, the basic joint surgery set, guide wire, nitinol wire, a screwdriver with the interference screw, and a cannulated 5-mm drill. The patient is positioned supine on the operation table with the knee flexed 90° in an electric leg holder with a thigh tourniquet. First, we identify the landmarks and mark them with a pen. You can see the patella, the patellar tendon with the tuberosity, the medial joint space, and the pes anserine for the surgical incision. Here you can see the course of the gracilis and semitendinosus muscles to the pes anserine. Before you start with the MPFL reconstruction, we recommend to perform diagnostic arthroscopy to identify and address concomitant lesions, such as the here seen cartilage lesion of the patella surface.

The first step is to loosen and mobilize the gracilis muscle insertion at the pes anserine. Incise the skin in line with the gracilis tendon over the pes anserine. Then dissect the subcutaneous tissue down to the sartorius-fascia and identify the underlying pes anserine. Incise the Sartorius fascia along the fiber course to expose the tendons. Identify the gracilis, which we are arming temporarily. Underneath you can see here the semitendinosus tendon. Deattach the gracilis tendon with its periost by leveraging the tendon with a clamp. Now arm the tendon, so you can shuttle it afterwards safely. You can do that with a whip stich. When the gracilis tendon is armed, free it in the next step from the accessory strands to the medial gastrocnemius head. We do this to have enough tendon length to redirect and reinsert the gracilis tendon in the medial margin of the patella.

Second step is to shuttle the gracilis muscle to its new insertion. First, identify the medial boarder of the patella and make a sharp mediopatellar skin incision to access the patella margin. The first layer is the skin. One layer deeper is the quadriceps muscle faszia. And down here, you can see the joint capsule. We have to go between the faszia of the quadriceps muscle and the joint capsule. Be careful to stay outside of the joint capsule. Bluntly dissect this layer with a long clamp all the way down toward the pes anserine, where our armed gracilis tendon is. Grasp the arming sutures and pass the suture-armed gracilis tendon up to the patella and around the incised sartorius fascia. The sartorius fascia now acts as a pully for the tendon, which will become our new dynamic MPFL. Make sure to have tendon long enough to securely fixate it in the next step into the patella. If the tendon is too short, you might consider releasing more of the hamstrings or incising the sartorius fascia to shift the hypomochlion more proximally and posterior. In case of too extensive release of the sartorius fascia, one might try to place a suture to close the fasica and reestablish the hypomochlion for the gracilis tendon.

Third step is to fixate the gracilis muscle at its new insertion. For that find the mid third of the patella, and place a guide wire through this mid third from the medial to the lateral patellar margin. Make sure that the guide wire is horizontal or slightly ascending. Verify the correct extraarticular position of the guide wire by flouroscopy using the anteroposterior and lateral view. Let the guide wire pass the skin on the lateral side. We make a small skin incision to spare the skin. Overdrill the guide wire from medial for 2 cm by using a 5-mm drill bit. Now shuttle the armed wire of the gracilis tendon through the patellar hole. For this, place the wire loop through the predrilled hole. Grasp the gracilis wire and shuttle it this way through the patella. We want the end of the gracilis tendon to easily glide into the predrilled hole, therefore lift the gracilis tendon before pulling it in the patella on the medial side as high as possible, before pulling on the lateral side on both wires. When the gracilis tendon is fully engaged in its new patella insertion, adjust a clamp on skin level to hold it at this space. Now place a nitinol wire, and fix the tendon with a 5 mm x 12 mm interference screw. Before closing the cuts, verify the extraarticular placement of your graft with a final arthroscopic view. The gracilis tendon is now safely attached at the patella and further on stabilizes it from lateral dislocation.

The biomechanical concept behind this surgical technique is the idea that the transfer of the gracilis insertion to the medial margin of the patella will change muscle function from being a knee flexor to a patella stabilizer. The capability and efficacy of such muscle transfer procedures have been described, for example in rectus femoris transfer. The gracilis muscle reaches forces up to 300 N from 0 to 60° knee flexion, indicating that the gracilis muscle is adequate for patella stabilization. Whether the reported favorable clinical outcome is due to the muscle contraction or to the passive tendonesis effect remains to be evaluated in future studies of the particular biomechanical effects of this procedure.

For postoperative treatment, the patients are granted immediate full weight bearing as tolerated with free active and passive range of motion. The patients should undergo physiotherapy, and we recommend follow ups after 6 weeks and 3 months. After 6 weeks, the patient should have full active range of motion and be able to bear full weight. After 3 months, we approve gradual activity increase in noncontact sports and after 6 months, we permit re-entry into contact sports.

Some final comments: dynamic MPFL reconstruction has disadvantages, but they are similar to the static reconstruction technique. They include the loss of the original function of the gracilis muscle and the risk of potential opening of the intraarticular space. Yet, there are clear advantages: lesser risk of overtensioning and malpositioning the graft, drilling only one hole instead of 3 as with the static method, easier positioning of the tunnel, only one interference screw, shorter operation time and dynamic tensioning compared with the static procedure. The few accomplished studies published so far show good or better functional results with the dynamic MPFL reconstruction, and we are sure many more studies will follow in the future.