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

PURPOSE

To verify the findings of previous studies in confirming radiographic landmarks for the femoral attachment of the medial patellofemoral ligament (MPFL), but also to define radiographic landmarks for the patellar attachment. Assess the effect of limb rotation upon these radiographic landmarks.

METHODS

The medial patellofemoral ligament was identified in ten fresh-frozen human cadaveric knees. A headed pin was used to mark the centre of the femoral and patellar attachments. True lateral radiographs were performed followed by lateral radiographs in 10° and 20° of internal and external rotation. Posterior-anterior and proximal-distal position of the headed pin was evaluated.

RESULTS

The femoral attachment averaged 3.8 ± 5.0 mm anterior to the posterior femoral cortical line and 0.9 ± 2.4 mm distal to the perpendicular line intersecting the posterior aspect of Blumensaat's line. The patellar attachment averaged 7.4 ± 3.5 mm anterior to the posterior patellar cortical line, 5.4 ± 2.6 mm distal to the perpendicular line intersecting the proximal margin of the patellar articular surface. There was a significant relationship between limb rotation and distance of femoral and patellar attachment from the posterior cortical line (P < 0.0001 and P < 0.0002 respectively).

CONCLUSION

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.