While double-bundle anterior cruciate ligament (ACL) reconstruction attempts to recreate the two-bundle anatomy of the native ACL, recent research also indicates that double-bundle reconstruction more closely reproduces the biomechanical properties of the ACL and restores the rotatory and sagittal stability to the level of the intact knee that was not attainable with anatomic single-bundle reconstruction. Though double-bundle reconstruction provides these potential biomechanical benefits, it poses a significant challenge to the surgeon who must attempt to accurately place twice as many tunnels while avoiding tunnel convergence compared to single-bundle reconstruction. In addition, previous work has shown that tunnel malpositioning may cause grafts that fail to reproduce the native biomechanics of the ACL, increase graft tension in deep knee flexion, increase anterior tibial translation, and produce lower IKDC (International Knee Documentation Committee) scores.

We hypothesise that experienced surgeons without the use of computer-assisted navigation will place tunnels on the tibial plateau and lateral femoral condyle that more closely emulate the locations of the native anteromedial (AM) and posterolateral (PL) ACL bundles than inexperienced surgeons with the use of computer-assisted navigation.

A novice surgeon group comprised of three medical students each performed double-bundle ACL reconstruction using passive computer-assisted navigation on a total of eleven cadaver knees. Their individual results were compared to three experienced orthopaedic surgeons each performing the identical procedure without the use of computer-assisted navigation on a total of nine cadaver knees.

There were no significant differences in placement of either the AM or PL tunnels on the tibial plateau between novice surgeons using computer-assisted navigation and experienced surgeons without the use of computer navigation. On the lateral femoral condyle, novice surgeons placed the AM and PL tunnels significantly more anterior along Blumensaat's line on average compared to experienced surgeons. Both groups placed femoral AM and PL tunnels anterior to previously described AM and PL bundle positions.

Novice surgeons utilizing computer-assisted navigation and experienced surgeons without computer assistance place the AM and PL tunnels on the tibial side with no significant difference. On the lateral femoral condyle, novice surgeons utilising computer-assisted navigation place tunnels significantly anterior along Blumensaat's line compared to experienced surgeons without the use of computer navigation.

Variations in the pivot shift test have been proposed by many authors, though, a test comprised of rotatory and valgus tibial forces with accompanied knee range of motion is frequently utilised. Differences in applied forces between practitioners and patient guarding have been observed as potentially decreasing the reproducibility and reliability of the pivot shift test.

We hypothesise that a low-profile pivot shift test (LPPST) consisting of practitioner induced internal rotatory and anterior directed tibial forces with accompanied knee range of motion can elicit significant differences in internal tibial rotation and anterior tibial translation between the anterior cruciate ligament (ACL) deficient and ACL sufficient knee.

Fresh, frozen cadaver knees were used for this study. Four practitioners performed the LPPST on each ACL sufficient knee. The ACL of each knee was subsequently resected and each practitioner performed the LPPST on each ACL deficient knee. Our quantitative assessment utilised computer assisted navigation to sample (10Hz) the anterior translation and internal rotation of the tibia as the LPPST force vectors were applied. We subsequently pooled and averaged data from all four practitioners and analysed the entrance pivot (tibial reduction with knee range of motion from extension into flexion) and the exit pivot (tibial subluxation with knee range of motion from flexion into extension).

We observed a significant difference in anterior tibial translation and internal tibial rotation in the ACL deficient vs. ACL sufficient knees during both the entrance and exit pivot phases of the LPPST. The entrance pivot (n=140) was found to have an average maximum anterior tibial translation of 7.83 mm in the ACL deficient knee specimens compared to 1.23 mm in the ACL sufficient knee specimens (p<0.01). We found the ACL deficient knees to exhibit an average maximum internal tibial rotation of 12.38 degrees compared to 11.24 degrees in the ACL sufficient specimens during the entrance pivot (p=0.04). The exit pivot (n=120) was found to have an average maximum anterior tibial translation of 7.82 mm in the ACL deficient knee specimens compared to 1.44 mm in the ACL sufficient knee specimens (p<0.01). The ACL deficient knees exhibited an average maximum internal tibial rotation of 12.44 degrees compared to 11.13 degrees in the ACL sufficient knee specimens during the exit pivot (p=0.02).

Our results introduce a physical exam maneuver (LPPST) consisting of practitioner induced internal rotatory and anterior directed forces, with notable absence of valgus force, on the tibia while applying knee range of motion. Our results demonstrate that the LPPST can elicit significant anterior translation and internal rotary differences in an effort to differentiate between the ACL deficient and ACL sufficient knee. Our work will next seek to explore the clinical reproducibility of this physical exam maneuver.