Intra-operative Fluoroscopic Measurements to Determine Tibial Tunnel Placement in Anatomical Double Bundle ACL Reconstruction (SS-44)

Abstract

IntroductionAccurate tunnel placement to reproduce normal anatomy of the anterior cruciate ligament (ACL) is critical for successful anatomic ACL reconstruction. Incorrect placement of the tunnels can result in abnormal tension in the graft, loss of motion and recurrent instability. Intra-operative fluoroscopy is commonly used to evaluate tibial tunnel placement during single-bundle ACL reconstruction. However, few studies have evaluated the use of intra-operative fluoroscopy to assess tunnel placement during anatomic double-bundle ACL reconstruction. The purpose of this study is to define references for placement of the tibial tunnels during anatomic double-bundle ACL reconstruction.MethodsThe anteromedial (AM) bundle and posterolateral (PL) bundle insertion sites were marked with a thermal device and measured with a ruler in a consecutive cohort of 50 patients who sustained an acute injury of the ACL and underwent anatomical double bundle ACL reconstruction. Mean age of the patients was 25 years (SD 11.3) and 24 were female. A tip ACL-guide was placed in the center of the AM and PL tibial footprints and two guide pins were sequentially passed. Standardized lateral intra-operative fluoroscopic images were obtained with the pins in the center of the insertion sites. Reference lines for fluoroscopic measurements in the sagittal plane included the medial joint line which connects the anterior and posterior edges of the tibial articular surface and Amis & Jakobs line passing through the posterior corner of the tibial plateau and parallel to the medial joint line (Fig 1). The pin position, representing the center of the AM and PL tibial tunnels, was normalized by dividing the distance from the anterior edge of the tibia to pins by the length of the medial joint line or Amis & Jakobs line respectively and then multiplying by 100(with 0% being the most anterior point and 100% being most posterior point).ResultsThe center for the AM bundle was found to be at 31 % (SD:5.5; range 20 - 42 %) of the AP distance on the medial joint line and at 36 % (SD:3.9; range 22.7 - 42.4 %) of the AP distance on the Amis & Jakobs line. The center of the PL bundle was at 48 % (SD:5.8; range 34.6 - 59.3 %) of the AP distance on the medial joint line and 48.5 % (SD:4.6; range 38.7 - 57.7 %) of the AP distance on the Amis & Jakobs line.ConclusionsThe most common technical cause of graft failure in ACL reconstruction is non - anatomic placement of the bone tunnels. The purpose of our study was to utilize basic fluoroscopic data to more accurately describe the anatomic tibial insertion sites of the AM and PL bundles of the ACL. Ideally, this data can serve as a reference for the tibial insertion sites during anatomic double bundle ACL reconstruction. However, we have also realized that significant anatomic variation exists between patients, and decisions with respect to tunnel placement should be individualized. Measurements obtained from intra-operative fluoroscopic images can be a useful guideline, but should not serve as an absolute determinant of tunnel position. IntroductionAccurate tunnel placement to reproduce normal anatomy of the anterior cruciate ligament (ACL) is critical for successful anatomic ACL reconstruction. Incorrect placement of the tunnels can result in abnormal tension in the graft, loss of motion and recurrent instability. Intra-operative fluoroscopy is commonly used to evaluate tibial tunnel placement during single-bundle ACL reconstruction. However, few studies have evaluated the use of intra-operative fluoroscopy to assess tunnel placement during anatomic double-bundle ACL reconstruction. The purpose of this study is to define references for placement of the tibial tunnels during anatomic double-bundle ACL reconstruction. Accurate tunnel placement to reproduce normal anatomy of the anterior cruciate ligament (ACL) is critical for successful anatomic ACL reconstruction. Incorrect placement of the tunnels can result in abnormal tension in the graft, loss of motion and recurrent instability. Intra-operative fluoroscopy is commonly used to evaluate tibial tunnel placement during single-bundle ACL reconstruction. However, few studies have evaluated the use of intra-operative fluoroscopy to assess tunnel placement during anatomic double-bundle ACL reconstruction. The purpose of this study is to define references for placement of the tibial tunnels during anatomic double-bundle ACL reconstruction. MethodsThe anteromedial (AM) bundle and posterolateral (PL) bundle insertion sites were marked with a thermal device and measured with a ruler in a consecutive cohort of 50 patients who sustained an acute injury of the ACL and underwent anatomical double bundle ACL reconstruction. Mean age of the patients was 25 years (SD 11.3) and 24 were female. A tip ACL-guide was placed in the center of the AM and PL tibial footprints and two guide pins were sequentially passed. Standardized lateral intra-operative fluoroscopic images were obtained with the pins in the center of the insertion sites. Reference lines for fluoroscopic measurements in the sagittal plane included the medial joint line which connects the anterior and posterior edges of the tibial articular surface and Amis & Jakobs line passing through the posterior corner of the tibial plateau and parallel to the medial joint line (Fig 1). The pin position, representing the center of the AM and PL tibial tunnels, was normalized by dividing the distance from the anterior edge of the tibia to pins by the length of the medial joint line or Amis & Jakobs line respectively and then multiplying by 100(with 0% being the most anterior point and 100% being most posterior point). The anteromedial (AM) bundle and posterolateral (PL) bundle insertion sites were marked with a thermal device and measured with a ruler in a consecutive cohort of 50 patients who sustained an acute injury of the ACL and underwent anatomical double bundle ACL reconstruction. Mean age of the patients was 25 years (SD 11.3) and 24 were female. A tip ACL-guide was placed in the center of the AM and PL tibial footprints and two guide pins were sequentially passed. Standardized lateral intra-operative fluoroscopic images were obtained with the pins in the center of the insertion sites. Reference lines for fluoroscopic measurements in the sagittal plane included the medial joint line which connects the anterior and posterior edges of the tibial articular surface and Amis & Jakobs line passing through the posterior corner of the tibial plateau and parallel to the medial joint line (Fig 1). The pin position, representing the center of the AM and PL tibial tunnels, was normalized by dividing the distance from the anterior edge of the tibia to pins by the length of the medial joint line or Amis & Jakobs line respectively and then multiplying by 100(with 0% being the most anterior point and 100% being most posterior point). ResultsThe center for the AM bundle was found to be at 31 % (SD:5.5; range 20 - 42 %) of the AP distance on the medial joint line and at 36 % (SD:3.9; range 22.7 - 42.4 %) of the AP distance on the Amis & Jakobs line. The center of the PL bundle was at 48 % (SD:5.8; range 34.6 - 59.3 %) of the AP distance on the medial joint line and 48.5 % (SD:4.6; range 38.7 - 57.7 %) of the AP distance on the Amis & Jakobs line. The center for the AM bundle was found to be at 31 % (SD:5.5; range 20 - 42 %) of the AP distance on the medial joint line and at 36 % (SD:3.9; range 22.7 - 42.4 %) of the AP distance on the Amis & Jakobs line. The center of the PL bundle was at 48 % (SD:5.8; range 34.6 - 59.3 %) of the AP distance on the medial joint line and 48.5 % (SD:4.6; range 38.7 - 57.7 %) of the AP distance on the Amis & Jakobs line. ConclusionsThe most common technical cause of graft failure in ACL reconstruction is non - anatomic placement of the bone tunnels. The purpose of our study was to utilize basic fluoroscopic data to more accurately describe the anatomic tibial insertion sites of the AM and PL bundles of the ACL. Ideally, this data can serve as a reference for the tibial insertion sites during anatomic double bundle ACL reconstruction. However, we have also realized that significant anatomic variation exists between patients, and decisions with respect to tunnel placement should be individualized. Measurements obtained from intra-operative fluoroscopic images can be a useful guideline, but should not serve as an absolute determinant of tunnel position. The most common technical cause of graft failure in ACL reconstruction is non - anatomic placement of the bone tunnels. The purpose of our study was to utilize basic fluoroscopic data to more accurately describe the anatomic tibial insertion sites of the AM and PL bundles of the ACL. Ideally, this data can serve as a reference for the tibial insertion sites during anatomic double bundle ACL reconstruction. However, we have also realized that significant anatomic variation exists between patients, and decisions with respect to tunnel placement should be individualized. Measurements obtained from intra-operative fluoroscopic images can be a useful guideline, but should not serve as an absolute determinant of tunnel position.