There are 3 methods to identify the insertion of the MPFL into the patella. During the diagnostic arthroscopy, an 18-gauge needle can be used to mark the insertion of the MPFL as visualization of the ligament arthroscopically is often possible (Figure 3). Another useful technique is to follow the inferior aspect of the distal insertion of the vastus medialis oblique (VMO) into the patella. The typical insertion point of the MPFL is immediately distal to the insertion of the inferior aspect of the VMO (Figure 4). It is also helpful to note that the center point of the insertion of the MPFL is at the junction of the proximal one-third and distal two-thirds of the palpable osseous patella. The MPFL origin has been noted to be at the exact midpoint of the chondral surface of the patella or 5 mm proximal (41% of the length of the patella) to the midpoint of the osseous patella.30
Following arthroscopic examination and treatment, a linear incision is made at the superior two-thirds of the patella, 1-finger breadth medial to the patella (Figure 5). During the subcutaneous dissection, the goal is to visualize the fascia overlying the VMO. Once this is identified, the dissection, in this layer, is carried over to expose the anterior and central surface of the patella. Army/navy retractors are used to retract the skin, and the assistant will place manual pressure on the patella to stabilize it for preparation of the patellar surface.
A bovie cautery or a knife is used to mark the insertion of the MPFL, which is immediately distal to the inferior border of the VMO. An incision over the medial surface of the patella creates a T-incision with elevation of the subsequent flaps proximal and distal. This allows exposure of the superficial and medial surface of the patella. During medial exposure of the patella, care is taken to avoid an arthrotomy by leaving the synovial lining attachment. A rongeur is used to decorticate the medial patella and the superficial surface (Figure 6). If an MPFL avulsion is present, it is often embedded within the soft tissues adjacent to the medial patellar. The MPFL avulsion can be exposed and removed if small. During an MPFL reconstruction, a repair of the avulsion is typically not performed. A double-loaded suture anchor is inserted at the site identified as the insertion of the native MPFL (3.0 Biocomposite SutureTak, Arthrex). A single suture anchor is used instead of an interosseous tunnel or double tunnels to avoid creating a large defect that may increase the risk of fracture in a small, skeletally immature patella.31
A hemostat is used to identify the layer between the medial retinaculum and the synovium over the medial soft tissue of the knee. The MPFL is a well-defined thickening of the medial retinaculum, and the ideal placement of the reconstruction is immediately inferior to this layer. Once this layer has been identified, a blunt hemostat is inserted to mark the end of a blind pouch that is apparent in this layer. This blind pouch is marked on the surface of the skin as the origin of the MPFL.
Fluoroscopy is now used to identify the origin of the MPFL on the medial femoral condyle. A perfect lateral is obtained by lining up the posterior condyle. Often, existent trochlear dysplasia will modify the normal appearance of the anterior structures of the condyles. Schottle’s point17 is USED to locate the origin of the MPFL. This is defined by drawing a line from the posterior cortex distally through the condyles (Figure 7). Two perpendicular lines are drawn, one to the extension of the posterior cortex at the level of the posterior extent of Blumensaat’s line and a second at the metaphyseal flare. Schottle’s point is located just anterior to the posterior cortex and in between these perpendicular lines. In a skeletally immature patient, this point appears to be at the level of the physis, on the lateral projection.
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