Manual restricted kinematic alignment technique restores postoperative limb alignment in severe knee deformities

Abstract Restricted kinematically aligned total knee arthroplasty (rKA-TKA) for severe deformity in the preoperative hip–knee–ankle angle (HKAA) has gained considerable interest. However, the widespread adoption of rKA-TKA has been limited by its requirement for expensive equipment such as navigatio...

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Bibliographic Details
Main Authors: Masahiro Ishikawa, Masaaki Ishikawa, Hideaki Nagashima, Takafumi Hiranaka
Format: Article
Language:English
Published: Nature Portfolio 2025-07-01
Series:Scientific Reports
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Online Access:https://doi.org/10.1038/s41598-025-13195-w
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Summary:Abstract Restricted kinematically aligned total knee arthroplasty (rKA-TKA) for severe deformity in the preoperative hip–knee–ankle angle (HKAA) has gained considerable interest. However, the widespread adoption of rKA-TKA has been limited by its requirement for expensive equipment such as navigation and robotic surgery systems. In this study, we developed manual rKA-TKA with modified soft tissue-respecting technique and investigated its surgical effects on postoperative HKAA. To achieve this, we examined factors affecting postoperative HKAA. Subsequently, the safe zone-related cut-off values of preoperative HKAA were calculated using the receiver operating characteristic curve, and postoperative HKAA was predicted using a linear regression model (LRM) and generalized additive model (GAM). Preoperative HKAA was identified as a factor influencing postoperative HKAA. The cut-off values of preoperative HKAA were −14 and −15° when the safe zones were defined as ± 1–3 and ± 4–5°, respectively. The GAM was more accurate in predicting the postoperative HKAA than the LRM. Additionally, the GAM showed a potential of falling within ± 5° of the postoperative HKAA, even in patients with preoperative HKAA ≤ − 19°. These findings suggest that manual rKA-TKA can be effective even for patients with severe deformities, providing an accessible alternative to conventional TKA for surgeons at resource-limited institutions.
ISSN:2045-2322