Does kinematic alignment accurately restore anterior trochlear thickness in TKA?

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Anatomy

Background:

• Kinematic alignment (KA) in total knee arthroplasty (TKA) aims to restore joint surfaces.
• The accuracy of KA in reproducing the anterior femoral anatomy, particularly the trochlear groove, is not well-established.

Purpose of the Study:

• To assess if KA-TKA with the anterior flush technique anatomically restores the anterior femoral compartment.
• To determine if bone resection differences vary with implant size or preoperative alignment.

Main Methods:

• Retrospective analysis of 94 knees undergoing KA-TKA.
• Intraoperative caliper measurements of bone resection at anterior flange and chamfer compared to implant thickness.
• Analysis of associations between resection differences (ΔT) and implant size or preoperative alignment.

Main Results:

• Consistent anterior understuffing observed: mean ΔT flange of 3.1 mm and ΔT chamfer of 3.9 mm.
• Greater understuffing in the chamfer region compared to the flange region (mean difference -0.9 mm).
• No significant correlation found between ΔT values and implant size or preoperative alignment.

Conclusions:

• KA-TKA using the anterior flush technique leads to predictable anterior understuffing.
• This understuffing may impact patellofemoral joint mechanics due to incomplete restoration of native trochlear thickness.
• Consideration of implant thickness is crucial for accurate trochlear restoration in KA-TKA.