Effect of tibial slope on the stability of the anterior cruciate ligament–deficient knee

Abstract Purpose We aimed to quantify the effect of changes in tibial slope on the magnitude of anterior tibial translation (ATT) in the anterior cruciate ligament (ACL)‐deficient knee during the Lachman and mechanized pivot shift tests. We hypothesized that increased posterior tibial slope would increase the amount of ATT of an ACL‐deficient knee, while leveling the slope of the tibial plateau would decrease the amount of ATT. Methods Lachman and mechanized pivot shift tests were performed on hip‐to‐toe cadaveric specimens, and ATT of the lateral and the medial compartments was measured using navigation ( n = 11). The ACL was then sectioned. Stability testing was repeated, and ATT was recorded. A proximal tibial osteotomy in the sagittal plane was then performed achieving either +5 or −5° of tibial slope variation after which stability testing was repeated ( n = 10). Results Sectioning the ACL resulted in a significant increase in ATT in both the Lachman and mechanized pivot shift tests ( P < 0.05). Increasing or decreasing the slope of the tibial plateau had no effect on ATT during the Lachman test (n.s.). During the mechanized pivot shift tests, a 5° increase in posterior slope resulted in a significant increase in ATT compared to the native knee ( P < 0.05), while a 5° decrease in slope reduced ATT to a level similar to that of the intact knee. Conclusions Tibial slope changes did not affect the magnitude of translation during a Lachman test. However, large changes in tibial slope variation affected the magnitude of the pivot shift.