Caliper-Based Restricted Kinematic Alignment Total Knee Arthroplasty.

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Surgical Technology

Background:

• Restricted kinematic alignment total knee arthroplasty (rKA-TKA) aims to prevent implant failure associated with extreme alignments.
• Current rKA-TKA techniques often rely on computer-aided surgical (CAS) systems, increasing cost and complexity.
• There is a need for simpler methods to achieve restricted kinematic alignment in total knee arthroplasty.

Purpose of the Study:

• To describe a surgical technique for kinematic alignment total knee arthroplasty (KA-TKA) using conventional mechanical instruments.
• To demonstrate that rKA-TKA can be achieved without computer-aided devices (CAS).
• To provide specific measurements and adjustments for accurate osteotomies in mechanical KA-TKA.

Main Methods:

• Preoperative long leg radiographs or CT scans are used to measure lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA).
• Arithmetic hip-knee-ankle angle (aHKA) is calculated (MPTA - LDFA) and used with predefined boundaries (LDFA: 85°-93°, MPTA: 85°-90°, aHKA: 5° varus to 3° valgus) to determine osteotomy angles.
• Femoral osteotomy adjustments involve modifying distal femoral surface thickness or using a variable angle cutting guide. Tibial osteotomy is guided by an extramedullary rod, limiting medial tilt to within 5.5°.

Main Results:

• The described technique allows for precise execution of restricted kinematic alignment using standard mechanical instruments.
• CAS is not required for achieving the desired alignment parameters in KA-TKA.
• The method provides a reproducible approach to bone preparation for total knee arthroplasty.

Conclusions:

• Kinematic alignment total knee arthroplasty (KA-TKA) can be successfully performed using mechanical instruments, offering a cost-effective alternative to CAS-based methods.
• This technique facilitates restricted alignment, potentially reducing the risk of implant failure.
• The described surgical technique provides a practical approach for surgeons to implement KA-TKA without advanced technology.