Closing Wedge and Opening Wedge High Tibial Osteotomy in the ACL Deficient Knee: A Comparison of Stability and Alignment

OBJECTIVES: Opening and closing wedge high tibial osteotomies for the treatment of medial compartment arthritis can lead to secondary intended and unintended changes in posterior tibial slope. The effect of slope neutralization using high tibial osteotomies in ACL deficient knees has not been fully defined. The purpose of this study was to quantify the changes in anterior tibial translation and rotational stability in the ACL deficient knee following mulitplanar high tibial osteotomies comparing opening wedge to closing wedge techniques. METHODS: Anterior drawer, Lachman, and Pivot-shift tests were performed on hip-to-toe cadaveric specimens (n=16) and translation of the lateral and medial compartments was measured using Praxim navigation system. The ACL was then sectioned and stability testing repeated and compartment translation recorded. Half of the knees then underwent a closing wedge (LCW) high tibial osteotomy using a lateral titanium Tomofix plate and screws (n=8). The contralateral knees underwent an opening wedge (MOW) high tibial osteotomy using a medial titanium Tomofix plate and screws (n=8). The goal of both procedures was for an 8-10mm correction with maximal sagittal slope neutralization. Following this procedure, stability testing and translation measurements were once again performed. Pre and post-operative CT scans were performed to assess initial posterior tibial slope and slope correction, as well as coronal plane correction. RESULTS: Sectioning the ACL resulted in a significant increase in anterior tibial translation (ATT) during Anterior drawer, Lachman, and Pivot shift testing (P < 0.05). In the ACL deficient knee the tibia translated on average an additional 2.1mm (±1.2) during Anterior drawer and 4.1mm (±2.1) during Lachman testing. Performing a LCW osteotomy demonstrated a significant decrease in ATT during Lachman testing that approached the native knee kinematics (P< 0.05), however, this decrease was not found during Anterior Drawer testing. ATT did not significantly improve following MOW osteotomy in the ACL deficient knee during any of the three tests. In fact, absolute translation values were unchanged following this procedure. The pivot shift was not significantly changed following either MOW or LCW. The mean Tibial Coronal alignment correction in the MOW group was 7.2º(±0.95) compared to 5.9º(±1.8) in the LCW group. Although the coronal correction was improved in the MOW, this difference did not reach significance (P = 0.08). The mean tibial slope neutralization achieved with a LCW was 7.1º(±1.8), which was significantly higher than 5.1 º(±0.9) found using MOW (P< 0.05). CONCLUSION: LCW HTO shows more reproducible slope neutralization than MOW and this benefits anterior translation during Lachman stability testing. When considering the use of an HTO in the setting of ACL deficiency, LCW should be considered given its favorable post-operative knee kinematics.