The Association Between Posterior-Inferior Tibial Slope and Anterior Cruciate Ligament Insufficiency

Purpose: The purpose of this study was to determine whether an increased posterior-inferior tibial slope (PITS) is associated with anterior cruciate ligament (ACL) rupture and whether an increased PITS results in worse pivot-shift grades in ACL-insufficient patients. This study also examined the difference in PITS between men and women. Methods: We radiographically measured the PITS angle of 100 ACL-insufficient patients and 100 patients with patellofemoral pain (control patients). The mean PITS of male and female cases and control patients was compared to determine whether sex had an influence on the mean PITS angle. The measured PITS was compared with the pivot-shift grade with patients under anesthesia in a subgroup of 87 isolated ACL-insufficient patients with no other knee injury. Results: Female ACL-insufficient patients had a significantly greater PITS (12.0° ± 3.5°) than their negative controls (8.6° ± 2.7°) ( P < .001). Male ACL-insufficient patients had a significantly greater PITS (10.8° ± 3.9°) than their negative controls (8.4° ± 3.4°) ( P < .001). In the isolated ACL-insufficient patients, the high-grade pivot-shift patient group had a statistically significantly greater PITS (11.10° ± 3.85°) than the low-grade pivot-shift patient group (9.19° ± 3.58°) ( P = .03). Conclusions: An increased PITS is associated with ACL rupture. A higher pivot-shift grade is associated with an increased degree of PITS. Female patients did not have a significantly greater mean PITS angle than male patients. Level of Evidence: Level III, prognostic case-control study.