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Does kinematic alignment accurately restore anterior trochlear thickness in TKA?
Katsuhiro Ito1, Takafumi Hiranaka1, Abdulaziz A Basaqr1
1Department of Orthopaedic Surgery and Joint Surgery Centre, Takatsuki General Hospital, Takatsuki, Osaka, Japan.
Background:
Kinematic alignment (KA) aims to restore the distal and posterior joint surfaces by matching the resected bone to the implant thickness. However, whether KA also accurately reproduces the anterior femoral anatomy, including the trochlear groove, remains unclear. Therefore, this study aimed to answer the following questions: (1) Is the anterior femoral compartment (anterior flange and chamfer) anatomically restored when performing KA-TKA using the anterior flush technique? (2) Does the difference between bone resection and implant thickness vary according to implant size or preoperative alignment?
Hypothesis:
It was hypothesized that anterior femoral restoration in KA-TKA could be quantitatively assessed and that its variation might be associated with preoperative alignment or implant size.
Methods:
A retrospective analysis was conducted of 94 knees in 65 patients who underwent KA-TKA between November 2024 and April 2025 at a single institution. Intraoperative caliper measurements of bone resection at the anterior flange and chamfer were compared with implant thicknesses, and the difference (ΔT) was calculated. Associations between ΔT at each site and implant size or preoperative alignment were also analyzed.
Results:
The mean ΔT flange was 3.1 ± 1.5 mm (p < 0.001), and the mean ΔT chamfer was 3.9 ± 1.2 mm (p < 0.001), indicating consistent understuffing in both regions. The difference between ΔT chamfer and ΔT flange was -0.9 ± 1.4 mm (p < 0.001), suggesting greater understuffing in the chamfer region than in the flange region. No significant correlation was observed between ΔT values and either implant size or preoperative alignment.
Discussion:
This study demonstrated that KA-TKA using the anterior flush technique results in consistent anterior understuffing at both the flange and chamfer regions. These findings suggest that the technique may not fully restore native anterior trochlear thickness, which could potentially influence patellofemoral joint mechanics, although the clinical significance of the observed magnitude of understuffing (approximately 3-4 mm) remains unclear. Moreover, implant thickness varies not only between different models but also across sizes, and consideration of implant thickness may be important for anatomically restoring the trochlea.
Level Of Evidence:
IV; retrospective study without control group.
