The prone kneeling view of the intercondylar notch for radiographic assessment of the femoral tunnel position in anterior cruciate ligament reconstruction.

PURPOSE: The purpose of this study was to verify the relevance of a novel radiograph, named the prone kneeling (PK) view of the intercondylar notch, for the assessment of femoral tunnel position in anterior cruciate ligament reconstruction.
METHODS: The PK view is taken with the subject prone, kneeling on the film, with the hip and knee joint flexed 90 degrees . The beam projects 20 degrees to the longitudinal axis of the femur posteroanteriorly. We used 5 human cadaveric femora in the experiment. A radio-opaque marker was applied in the intercondylar notch from the 12- to 8-o'clock position, which represented the tunnel position during arthroscopy. Radiographs simulating the anteroposterior (AP), tunnel, and PK view were obtained, and the positional data in angles were compared with the designated positions in the notch during arthroscopy.
RESULTS: From 12:00 to 11:00, all 3 radiographs gave comparable values to the true angle. At 10:30 and 10:00, only the PK view provided a comparable value whereas the other 2 radiographs yielded significantly different values. From 9:30 to 8:00, even though all 3 radiographs showed significantly different values from the true angle, the PK view was closest to the true angle, followed by the tunnel view and AP view.
CONCLUSIONS: The PK view shows the intercondylar notch with the femoral tunnel angle more accurately than the AP or tunnel view. This most closely represents the true angle of the femoral tunnel and is very similar to the angle seen at arthroscopy. CLINICAL RELEVANCE: The position of the femoral tunnel seen on the postoperative plain AP radiograph might not appear identical to that determined during arthroscopy, probably because of the different knee position.