Summary

Pivot-shift represents the most clinically relevant biomechanical outcome for ACL reconstruction. This manuscript demonstrates kinematic changes in a hip-to-toe cadaver without associated lesions to amplify knee instability. The anatomic reconstruction in the center of ACL footprint group exhibited a greater restriction of internal rotation than did ACL reconstruction in AM bundle tunnel position.

Abstract

Background

The knee kinematics of a pivot-shift maneuver may represent the most clinically relevant biomechanical outcome when comparing surgical techniques for ACL reconstruction, and the pivot-shift phenomenon is a focus of basic and clinical research. The optimal femoral and tibial tunnel locations for grafting in anterior cruciate ligament (ACL) reconstruction are within the original ACL footprint. However, even with anatomic reconstructions, some patients still report giving way.

Purpose

This study aimed to compare knee stability in two different anatomic footprint ACL reconstruction positions.
Study Design: Controlled Laboratory Study

Methods

Thirty anatomic reconstructions were performed on fifteen fresh cadaveric hip-to-toe specimens. No associated lesions were created to intensify knee instability. The protocol was conducted in four states: (1) intact ACL; (2) complete-isolated ACL deficiency; (3) anatomic femoral and tibial anteromedial ACL reconstruction (AM REC); and (4) anatomic femoral and tibial central ACL reconstruction (Central REC). The reconstructions were randomly assigned. The Lachman test (68-N) and a mechanized pivot-shift test were recorded with a tracking system. Statistics: Internal rotation (°) and anterior displacement (mm) were analyzed in both tests with two- and one-way RM-ANOVA, respectively (a < 0.05).

Results

The Central REC group showed a smaller degree of internal rotation in the pivot-shift (0.6° ± 0.3° vs. 1.8° ± 0.3°, respectively, P < 0.05) and Lachman (2.9° ± 0.4° vs. 3.9° ± 0.4°, respectively, P < 0.05) tests and no difference in anterior translation in either the pivot-shift (4.7 mm ± 0.4 mm vs. 4.5 mm ± 0.4 mm, respectively, P > 0.05) or Lachman (1.2 mm ± 0.2 mm vs. 1.1 mm ± 0.2 mm, respectively, P > 0.05) tests compared to the AM REC group. The Central REC and AM REC groups showed no differences in anterior translation and internal rotation compared to the ACL-intact group (P > 0.05) in the Lachman test but did show significant differences in the pivot-shift test compared to the ACL-intact group (P < 0.05).

Conclusions

This manuscript adds new knowledge, as it is the first study to demonstrate knee kinematic changes in a hip-to-toe cadaver model without associated lesions to amplify knee instability. The Central REC group exhibited a greater restriction of internal rotation than did the AM REC group based on mechanized pivot-shift in a cadaveric model.
Clinical relevance: This manuscript is part of multiple studies with similar biomechanical findings related to anatomic ACL reconstruction that may contribute to orthopedic surgeon decision on tunnel positioning.