Restricted Kinematic Alignment, the Fundamentals, and Clinical Applications

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Medical Device Technology

Background:

• Kinematic Alignment (KA) aims to restore pre-arthritic lower limb alignment in total knee arthroplasty (TKA).
• Atypical knee anatomies can negatively impact TKA biomechanics and implant longevity.
• The restricted kinematic alignment (rKA) protocol was developed to manage anatomical variations within KA.

Purpose of the Study:

• To introduce and describe the restricted kinematic alignment (rKA) protocol for total knee arthroplasty.
• To establish principles for managing patient-specific knee anatomy during TKA.
• To evaluate the clinical and biomechanical outcomes of the rKA technique.

Main Methods:

• The rKA protocol is based on five principles, including coronal alignment, joint line orientation, soft tissue preservation, femoral anatomy preservation, and pivot selection.
• An algorithm guides decision-making for anatomical adjustments.
• Patient-specific instrumentation, computer navigation, or robotic assistance are recommended for rKA implementation.

Main Results:

• The rKA protocol produced excellent mid-term clinical results for cemented and cementless TKA.
• Gait analysis revealed rKA TKA patients exhibited gait patterns closely resembling a non-operated control group.
• rKA TKA demonstrated significantly better patient-reported outcomes compared to Mechanical Alignment (MA) TKA.

Conclusions:

• The rKA protocol provides a viable compromise for TKA, effectively recreating patient anatomy while avoiding extreme corrections.
• rKA enhances TKA biomechanics and patient outcomes by respecting individual anatomy.
• This technique offers an improvement over MA TKA, particularly for patients with non-standard knee anatomy.