Measurement of the Posterior Tibial Slope Depends on Ethnicity, Sex, and Lower Limb Alignment: A Computed Tomography Analysis of 378 Healthy Participants

Abstract

Background: There is no general consensus on the normal and pathological values for the posterior tibial slope (PTS). Purpose/Hypothesis: The primary aim of this study was to determine standard values for the PTS in healthy participants using 3-dimensional (3D) computed tomography (CT). A secondary aim was to determine the effect of demographic factors and coronal-plane lower limb alignment on the PTS measurement. The hypothesis was that the PTS would be significantly influenced by demographic factors and coronal-plane lower limb alignment. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A CT-based modeling and analytics system was used to examine and measure lower limb alignment and the PTS in 378 patients (193 male and 185 female; mean age, 58.3 ± 16.4 years [range, 18-92 years]; mean body mass index, 25.0 ± 4.4 kg/m2). The lateral, medial, and global PTS were measured for each patient. All measurements were constructed using algorithm-calculated landmarks, resulting in reproducible and consistent constructs for each specimen. The results were then evaluated based on ethnicity, sex, and hip-knee-ankle (HKA) angle. Results: The study population comprised 219 white and 159 Asian participants. The mean global, medial, and lateral PTS were 6.3° (range, –5.5° to 14.7°; 1% with ≥12°), 6.2° (range, –4.1° to 17.2°; 3% with ≥12°), and 5.3° (range, –4.7° to 16.2°; 2% with ≥12°), respectively. The lateral (Δ = –1.0° [95% CI, 0.6°-1.6°]; P < .0001) and global (Δ = –0.5° [95% CI, 0.0°-0.8°]; P = .0332) PTS were smaller in the female subpopulation. The global PTS was greater (Δ = 1.9° [95% CI, 1.5°-2.3°]; P < .0001) in the Asian subpopulation. The mean HKA angle was 179.6° (range, 170°-190°). The HKA angle was significantly correlated with the medial and global PTS. Specimens with a genu varum knee exhibited a significantly greater global (Δ = 1.2° [95% CI, 0.8°-1.7°]; P < .0001) and medial (Δ = 1.9° [95% CI, 1.3°-2.5°]; P < .0001) PTS. Conclusion: The present study gives a benchmark for the physiological values of the PTS in a healthy population and highlights several factors influencing the PTS, such as ethnicity, sex, and alignment. Anatomic variants with a PTS ≥12° were very uncommon (≤3%) in our Asian and white groups and thus could be considered as pathological. The PTS is a crucial anatomic factor for anterior cruciate ligament injuries and reconstruction. A general consensus is lacking regarding the cutoff for abnormal values, thus guiding standard of care. This study investigated the dispersion of global, medial, and lateral posterior plateau tibial angles in a large population representing a range of demographic diversity.

Ramp lesions are six times more likely to be observed in the presence of a posterior medial tibial bone bruise in ACL-injured patients

“…In contrast, Kim et al found a higher mean medial PTS in patients with a ramp lesion compared to patients without a ramp lesion [19]. In agreement with Song et al, [19,33] It remains unclear why they have much higher PTS values and may be due to different characteristics in the studied population [28].…”

The effect of gender, age, and body mass index on the medial and lateral posterior tibial slopes: a magnetic resonance imaging study

“…Specifically, the medial PTS was 5.86 ± 3.03° and 6.61 ± 3.32° and the lateral PTS was 4.41 ± 3.35° and 4.63 ± 2.85° in men and women, respectively. Cinotti et al [ 20 ] and Han et al [ 22 ] also reported no gender difference in medial and lateral PTS angles in Italian and South Korean participants. This is consistent with several radiographic studies conducted in different ethnic groups [ 2 , 12 , 26 ].…”

“…In addition to the method used for the measurement of the PTS, ethnicity largely determines what is considered normal for the PTS. Several studies based on various modalities have reported differing normal values for the PTS according to ethnicity [ 19 , 20 ]. The findings of the present study demonstrated a mean physiological medial PTS of 5.86 ± 3.0° and 6.61 ± 3.32°, and lateral PTS of 4.41 ± 3.35° and 4.63 ± 2.85° in men and women, respectively.…”

Anatomical and Neuromuscular Factors Associated to Non-Contact Anterior Cruciate Ligament Injury

“…This choice was made so as to study factors easy to measure in clinical practice in order to propose a “predictive approach” of ACL injury without expensive medical means. In addition, MRI measurements have the limit of not performing the knee in support, which may explain some controversies [ 35 ]. However, radiological or posturometric examinations could be of greater value.…”

“…Dynamic knee valgus would be poorly controlled in women during a non-contact ACL rupture, due to an increase in hip varus, knee valgus and Hamstring strength deficit (or an imbalance of Hamstring/Quadriceps ratio) [ 11 , 27 , 28 , 29 , 30 , 31 , 32 ]. However, the links between dynamic knee valgus and static knee valgus (non-modifiable factor) are poorly known [ 33 , 34 , 35 ].…”