A morphometric study of the tibial plateau slope and depth in a South African population

Abstract

Maintenance of lower limb alignment is important during surgeries involving the knee. For example, several studies have demonstrated that a higher posterior tibial plateau slope (PTPS) is a risk factor for anterior cruciate ligament (ACL) injuries. Furthermore, a PTPS ≥ 12° is a risk factor for failure of anterior cruciate ligament reconstruction. Population-specific and sex-specific differences have been reported on the PTPS in relation to different axes. Only a few studies have examined the potential risk factors associated with the geometry of the tibial plateau in relation to anterior and posterior cruciate ligament injuries. Knowledge of the PTPS, as well as the medial tibial plateau depth (MTPD), may benefit clinicians in identifying patients that may be at increased risk of graft failure following ACL reconstruction surgeries and in screening patients that may be at greater risk for cruciate ligament injuries.

As such, the PTPS in relation to the anterior tibial cortex axis (ATCA), proximal tibial anatomical axis (PTAA), and posterior tibial cortex axis (PTCA) were studied on radiographs. A sample of 480 lateral knee radiographs was examined to determine the PTPS slopes. Significant differences were only observed between weight bearing and non-weight bearing radiographs for White females (p = 0.035) when comparing the PTPS in relation to the ATCA (PTPS-ATCA) measurements. No sexual dimorphism or population differences were observed for the PTPS (p ≥ 0.05). Significant differences were observed between the PTPS -ATCA, PTPS in relation to the PTAA (PTPS-PTAA), and PTPS in relation to the PTCA (PTPS-PTCA) (p < 0.001). The age of an individual was insignificantly weakly correlated to the PTPS in relation to the ATCA (r = 0.074; p = 0.104), PTAA (r = 0.031; p = 0.499), and PTCA (r = -0.018; p = 0.686).

The MTPD was studied on an osteological sample consisting of the bilateral examination of the tibiae of 59 individuals. No bilateral asymmetry was observed in the MTPD (p ≥ 0.05). The MTPD was shown to be sexually dimorphic (p < 0.05) for both Black and White individuals. Population differences were observed when comparing males and females respectively for Black (p = 0.001) and White individuals (p < 0.001). The MTPD was found to be weakly correlated to the age (r = 0.066; p = 0.478), stature (m) (r = 0.204; p = 0.035), weight (kg) (r = 0.209; p = 0.031) and body mass index (BMI) (kg/m2) (r = 0.115; p = 0.242) of an individual. The correlations between the MTPD and the stature (m) and weight (kg) of an individual was significant (p < 0.05).

Fractures made up 73% of diagnoses made in the category of traumatic injuries of bone. Ligament and meniscus pathologies were observed in 59% of patients presenting with traumatic conditions of soft tissues. The largest proportion of patients diagnosed with degenerative conditions presented with osteophytosis (33%). A very small proportion of patients presented with dislocations and subluxations (n = 4). 63% of patients diagnosed with conditions related to the patella, patellofemoral joint and knee joint presented with knee joint narrowing. The largest proportion of surgical interventions consisted of knee replacements (51%). A small sample (n = 43) of observations was made regarding knee joint configuration.

The PTPS-ATCA, PTPS-PTAA, and PTPS-PTCA was shown to be highly variable in the South African population. A significant difference was observed between weight bearing and non-weight bearing radiographs in the White female sample (p = 0.035). This difference, however, was small and may not be clinically relevant. No populationspecific or sex-specific differences were observed in the PTPS-ATCA, PTPS-PTAA, or PTPS-PTCA. Significant differences were observed for the PTPS-ATCA, PTPS-PTAA, and PTPS-PTCA in the South African population (p < 0.001). Sexual dimorphism exists for the MTPD in the Black and White South African populations with a greater depth of concavity being observed in males than in females (p = 0.001 [Black population] and p < 0.001 [White population]). No population-specific differences were observed for the MTPD when White and Black populations were compared for females (p = 0.768) or males (p = 0.633).