No Difference in Limb Alignment Between Kinematic and Mechanical Alignment Robotic-Assisted Total Knee Arthroplasty

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical device technology

Background:

• Individualized alignment techniques are increasingly explored to enhance patient satisfaction after total knee arthroplasty (TKA).
• Comparing kinematic alignment (KA) and mechanical alignment (MA) is crucial for understanding postoperative limb alignment outcomes.
• Assessing KA's deviation from neutral alignment principles is key for clinical adoption.

Purpose of the Study:

• To compare the postoperative limb alignment between robotic-assisted TKA using kinematic alignment (KA) and mechanical alignment (MA).
• To evaluate if KA significantly deviates from the goal of achieving neutral limb alignment.
• To assess changes in coronal plane alignment classification from pre- to postoperative between KA and MA.

Main Methods:

• A comparative study involving 234 patients undergoing robotic-assisted TKA (145 KA, 89 MA).
• Measurement of lateral distal femoral angle, medial proximal tibia angle, and arithmetic hip-knee-ankle angle (aHKA).
• Primary outcome: frequency of aHKA within ±4° of neutral (0°) on radiographs at 6 weeks postoperatively.

Main Results:

• No significant difference in the proportion of cases achieving neutral alignment (aHKA ±4°) between KA (91.7%) and MA (96.6%).
• Kinematic alignment group showed 97.2% of cases within ±5° of neutral alignment.
• Mechanical alignment was associated with a significantly higher rate of change in coronal plane alignment classification from pre- to postoperative (P < .001).

Conclusions:

• Kinematic alignment yields postoperative limb alignment comparable to mechanical alignment.
• KA does not significantly deviate from the principle of achieving neutral limb alignment.
• Surgeons can be confident in introducing individualized kinematic alignment techniques, with most cases falling within 5° of neutral alignment.