Radiographic landmarks for tunnel placement in reconstruction of the medial patellofemoral ligament

Abstract

Radiographic landmarks for the femoral attachment of the MPFL identified in this study are comparable with other recent work. This study describes new radiographic landmarks for the patellar attachment of the MPFL and highlights that it is essential to acquire true lateral radiographs if these radiographic landmarks are to be interpreted accurately.

Radiographic Reference Points Are Inaccurate With and Without a True Lateral Radiograph

“…Redfern et al 30 also reported a more posterior femoral attachment, located on average 0.5 mm anterior to the posterior femoral cortex line and 3 mm proximal to the apex where the posterior cortex line intersects Blumensaat line. In contrast, Barnett et al 5 reported the MPFL femoral attachment center to be located 2.5 mm more anterior than that reported by Schöttle et al, 32 as well as nearly 4 mm distal to the previously described location using the same radiographic lines. Wijdicks et al 50 also reported a more anterior position of the MPFL attachment, placing it 8.8 mm anterior to the posterior femoral cortex line, 7.5 mm more anterior than that reported by Schöttle et al 32 while nearly identical in location in the proximal-to-distal plane.…”

“…8 Studies have reported methods for radiographically localizing the MPFL femoral tunnel position on a true lateral knee radiograph. 5,30,32,45,50 However, obtaining a true lateral fluoroscopic radiograph intraoperatively, particularly with a mini C-arm, can be very challenging, rendering radiographic methods for tunnel placement potentially inaccurate. In addition, misplacing the femoral tunnel as little as 5 mm has been reported to significantly alter graft isometry, medial patellar tilt, and peak medial patellofemoral pressure.…”

Accuracy and Learning Curve of Femoral Tunnel Placement in Medial Patellofemoral Ligament Reconstruction

“…Rotation in any direction of less than 7 mm was considered acceptable. 27 To be included, the femoral tunnel had to be readily identified on the lateral radiograph. There were eight subjects whose imaging was available but was inadequate to determine femoral tunnel position.…”

“…24 In this study of eight cadaveric specimens, a radio-opaque marker placed in the femoral insertion of the MPFL fell into a 5-mm area that is now widely known as "Schöttle's point." Although Schöttle's work is widely quoted, studies published since have shown there may be more variability in the radiographic insertion point of the MPFL [25][26][27][28] (►Fig. 1).…”

Reconstruction of the Medial Patellofemoral Ligament With Arthroscopic Control of Patellofemoral Congruence Using Electrical Stimulation of the Quadriceps

“…First, the femoral anchoring site of the reconstructed MPFL is deviated slightly posteriorly, although still within the range of the reported area for the anchoring site, [13][14][15][16][17][18] to meet the demand of patients to sit squarely after surgery. When this point is used, the distance between the patellar and femoral attachment sites gradually shortens as the knee joint bends to more than 60 of flexion, regardless of the site of patellar attachment.…”