gms | German Medical Science

Objectives: The lower limbs stand as a critical interface between the ground and the body center of mass (BCOM), influencing the transmission of gravitational and ground reaction forces (GRFs) through the feet. The advent of whole body weight-bearing CT-scan (WBCT) will revolutionize the assessment of the 3D alignment of the body, yet neglecting dynamic forces.

Defining static and dynamic lower limb measurements in the context of whole body alignment is pivotal in the field of orthopedics and biomechanics. We therefore performed a review to emphasize current limiting factors preventing advancements in 3D lower limb alignment measurement.

Methods: We searched four databases (PubMed, Scopus, Web of Science, and Google Scholar), for articles addressing definitions of joint center (JC) of the hip, knee, and ankle, BCOM, center of pressure (COP), GRFs, and bone segmentation of the lower limb. We selected and narratively reviewed studies focusing on different imaging and functional methods. We addressed disagreements in landmark positioning, emphasizing comparisons between the mainly static orthopedic/radiologic domain and the dynamic biomechanical domain.

Results and conclusion: Measurement methods for defining JCs, BCOM, GRF, and overall 3D lower limb alignment are currently tailored to specific domains and research objectives. Ankle and knee JCs exhibit variations in static and dynamic measurements based on joint motion, weight-bearing status, and prosthetic design. The hip JC, modeled reliably as a sphere, displays less variation. Current lower limb landmarking protocols lack standardization especially regarding limb deformities and artifacts, complicating advancements in automatic segmentation. Both static and dynamic approaches present limitations in defining BCOM, GRF, and COP, fundamental to understand whole body alignment and postural control.

This review emphasizes the need for a unified approach to 3D lower limb alignment measurement. Challenges in static versus dynamic measurements, CT-scan image processing, and landmark standardization must be addressed before moving forward to define 3D whole body alignment.