Neutral Mechanical Alignment and Prevalence of Constitutional Varus Knees Among the Saudi Population at King Saud University Medical City.

Background Various studies have described the restoration of the neutral mechanical alignment of the lower limb in total knee replacement (TKR) as a key factor of knee implant durability. Mechanical alignment of the knee requires that the tibial and femoral cuts are perpendicular to the mechanical axis of each bone in the coronal plane. Objectives The aim of this study is to investigate mechanical knee alignment and the prevalence of constitutional varus knee among the Saudi population at a single tertiary center with no history of musculoskeletal abnormalities. Methodology This is a retrospective cross-sectional study involving patients with no musculoskeletal abnormality who had their lower limb X-ray Centigram using the universal viewer zero footprint system made between 2015 and 2021. The study took place at King Saud University Medical City. The X-rays were obtained from patients' electronic medical records retrospectively. A total of 728 knees of 370 males and 358 females were included in this study. Results The results showed that 165 male knees (44.4%) and 218 female knees (60%) had constitutional varus alignment with the hip-knee-ankle (HKA) angle of ≤3° or less. The average HKA angle was smaller in males than in females: -3.69° versus -1.98°, respectively. Conclusion We have identified variables and factors that can help surgeons detect the constitutional varus on a full leg radiograph preoperatively at the time of TKA, regardless of the osteoarthritic changes of the knee. We encourage the scientific community to look for causes and risk factors for developing constitutional varus.