Hereditary Anatomical Risk Factors for Anterior Cruciate Ligament Injuries

Abstract

Introduction: Genetic and anatomical factors have been reported as risk factors for anterior cruciate ligament (ACL) injuries. This study aimed to investigate anatomical characteristics in family members sustaining ACL injuries, compared with age- and sex-matched patients with simple meniscus injuries.

Materials and methods: Medical records of 1548 patients who underwent ACL reconstruction were reviewed. Cases of ACL injury occurring in first-degree relatives were selected. Forty-one patients from 20 families were included in the study (F-ACL group). Fifty patients with meniscus injuries were included as controls. Anatomical factors comprising posterior-inferior tibial slope (PITS), notch width index (NWI), notch angle (NA), and intercondylar notch roof inclination angle (RA) were compared between groups. The correlation of these anatomical factors between parent and child or siblings was also investigated.

Results: The 41 patients (20 families) consisted of 12 parent-child pairs and 29 siblings (13 pairs and one trio). Injuries occurred during playing the same sport in 11 families (55%). PITS was significantly steeper in the F-ACL group (9.9 vs. 7.8 degrees). NWI and NA were significantly smaller in the F-ACL group (0.262 vs. 0.278 and 50.5 vs. 58.8 degrees). RA was significantly greater in the F-ACL group (130 vs. 126.9 degrees). A positive correlation in NA (r = 0.677) and a weak correlation in NWI and RA were observed between family members.

Conclusions: Common anatomical risk factors of ACL injury exist within families, including intercondylar notch stenosis and steep posterior tibial slope. The findings suggest the potential for developing effective ACL injury prevention programs targeting these risk factors.

Keywords: acl injuries; anatomical characteristics; family members; intercondylar notch; risk factors.

Figure 1. Anatomical factors

The posterior-inferior tibial slope (PITS) angle is defined as 90°minus the angle made by the intersection of the line along the longitudinal axis of the tibia and the slope of the medial tibial plateau, as described by Kostogiannis et al. [24] The notch width index (NWI) is the ratio of the intercondylar notch width to the bicondylar width of the distal femur at the level of the popliteus groove in coronal view. The notch angle (NA) is measured at the level of the popliteus groove, tracing the opening of the intercondylar notch in coronal view. Intercondylar roof inclination angle (RA) is the obtuse angle formed by the intersection of a line over the Blumensaat line and a line parallel to the long axis of the knee in the midsagittal view. MWI, NA, and RA measurements are as described by Tuca et al. [18].

Figure 2. Comparing the anatomical factors (PITS, NWI)

Comparisons between F-ACL group (n = 41) and control group (n = 50) in posterior-inferior tibial slope (PIST) and notch width index (NWI). Horizontal bar indicates mean value. Data expressed in mean ± standard deviation is shown next to each dot plot. *p＜0.05, statistically significant difference.

Figure 3. Comparing the anatomical factors (NA, RA)

Comparisons between F-ACL group (n = 41) and control group (n = 50) in notch angle (NA), and roof inclination angle (RA). Horizontal bar indicates mean value. Data expressed in mean ± standard deviation is shown next to each dot plot. *p＜0.05, statistically significant difference.

Figure 4. Correlation between family members for each anatomical factor (PTIS, NWI)

Posterior-inferior tibial slope (PITS) or notch width index (NWI) was plotted with values for the parent or older brother or older sister on the horizontal axis, and the values for the child or younger sister or younger brother on the vertical axis. r = correlation coefficient.

Figure 5. Correlation between family members for each anatomical factor (NA, RA)

Notch angle (NA), or intercondylar roof inclination angle (RA) was plotted with values for the parent or older brother or older sister on the horizontal axis, and the values for the child or younger sister or younger brother on the vertical axis. r = correlation coefficient.