Purpose of the study: To audit the radiological position of the tunnels following reconstruction of the anterior cruciate ligament (ACL).

Methods: Postoperative radiographs were obtained on patients following ACL reconstruction in a single surgeon series. The positions of the tunnel in the femur and the tibia were measured and recorded. The tunnel positions were compared to the recommended positions as established by literature review. Lateral radiographs displaying greater than 2mm of imperfect projection in relation to the femoral condyles were noted.

Results: 108 radiographs were collected from 105 patients, 60 were right knees and 48 were left. There were 88 men and 17 women.

When measured along Blumensaats line from the anterior condylar surface, the femoral tunnel in the saggital plane should be found at 75% of the total anteroposterior distance, the recorded figure in this audit was 74%. Measured from the anterior edge in the saggital plane, the tibial tunnel should be found at 44% of the total tibial depth, our measurements averaged 40%. The tibial tunnel in the coronal plane should be found at 45% of the total width from the medial edge, our measurements averaged 46%.

57 (53%) of the radiographs demonstrated imperfect lateral projection of greater than 2mm.

Conclusion: The position of the tunnels analyzed in this audit compare favourably with the positions recommended in the available literature. Over 50% of the lateral radiographs displayed imperfect lateral projection greater than 2mm. Imperfect lateral film projection affects the apparent position of the tunnel. Any interpretation of position as it appears on a two-dimensional image must take into account possible errors in the image.