Anatomic variations should be considered in total knee arthroplasty.

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Total knee arthroplasty (TKA) aims to restore knee function but can be complicated by patient-specific anatomic variations.
• Medial osteoarthritis (OA) presents unique challenges in TKA due to characteristic knee deformities.
• Accurate component alignment is critical for TKA success and longevity.

Purpose of the Study:

• To assess the influence of specific anatomic variations on operative techniques in total knee arthroplasty (TKA).
• To identify key radiographic parameters indicative of variations affecting femoral and tibial component positioning.
• To provide guidance on adjusting TKA surgical techniques based on individual patient anatomy.

Main Methods:

• Analysis of anteroposterior radiographs of 133 Japanese patients with medial osteoarthritis (OA).
• Measurement of six key parameters including femoral shaft bowing, proximal tibia vara, and tibial shaft lateral offset.
• Evaluation of the angle between the mechanical axis and distal femoral condyles for femoral component rotation.

Main Results:

• Identified common variations: femoral shaft bowing, proximal tibia vara, and lateral tibial shaft offset.
• Determined that 20% of patients exhibited an angle requiring >3 degrees of external femoral component rotation.
• Highlighted that the tibial plateau's center is medial to the tibial shaft's midline in medial OA, complicating tibial component alignment.

Conclusions:

• Preoperative evaluation of anatomic variations is essential before performing TKA.
• Specific adjustments in femoral component external rotation and tibial component alignment are necessary for certain patient anatomies.
• Understanding these variations can improve TKA outcomes and reduce complications like component impingement.