2025 ISAKOS Biennial Congress ePoster
Knees With Anteromedial Osteoarthritis Show A Substantial Variability In Coronal Plane Alignment Of The Knee (Cpak) Phenotypes: Prevalence And Phenotypic Changes Following Medial Unicompartmental Knee Arthroplasty
Gaby Victoria Ten Noever De Brauw, Bsc, Amsterdam NETHERLANDS
Tarik Bayoumi, MD, Amsterdam NETHERLANDS
Lindsey Ruderman, BA, New York UNITED STATES
Gino M. M. J. Kerkhoffs, MD, PhD, Prof., Amsterdam NETHERLANDS
Andrew D. Pearle, MD, New York, NY UNITED STATES
Hendrik Aernout Zuiderbaan, MD PhD, Velsen NETHERLANDS
Hospital for Special Surgery, New York , UNITED STATES
FDA Status Not Applicable
Summary
There is a substantial variation in CPAK phenotypes among knees with anteromedial OA, as well as following treatment with medial UKA. This variability challenges the assumption of uniform characteristics among knees with an identical wear pattern associated with anteromedial OA and emphasizes the complexity and variability of this specific form of OA.
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Abstract
Aim
The primary aim of this study was to evaluate the phenotypic variation in the Coronal Plane Alignment of the Knee (CPAK) classification among 1000 knees of patients with anteromedial osteoarthritis (OA) by comparing preoperative radiographic parameters with radiographic outcomes at six-weeks following medial unicompartmental knee arthroplasty (UKA). The secondary aim of this study was to investigate whether knees maintained their preoperative CPAK phenotype and to evaluate the phenotypic alterations in the coronal plane that occur following medial UKA.
Methods
The CPAK classification was used to analyze 1000 knees that underwent medial UKA as treatment for anteromedial OA. Knees were categorized into nine distinct CPAK phenotypes based on their arithmetic hip-knee-ankle angle (aHKA), which estimates the pre-arthritic alignment, and joint line obliquity (JLO), both pre- and postoperatively. Phenotypic variation was analyzed by sex and age, and the phenotypic alterations following medial UKA were evaluated by phenotype.
Results
Preoperatively, CPAK phenotype I had the highest prevalence (45%). Among males, the preoperative prevalence of CPAK phenotype I was significantly higher compared to females (53% vs. 35%, respectively; p = <.001), whereas females exhibited a significantly higher occurrence of CPAK phenotype V compared to males (10% vs. 4%, respectively; p = <.015). Following medial UKA, CPAK phenotype II had the highest prevalence (53%). Overall, 45% of knees maintained their preoperative CPAK phenotype following medial UKA, which was most frequently observed among CPAK phenotype II (68%) and III (66%).
Conclusions
There is a substantial variation in CPAK phenotypes among knees with anteromedial OA, as well as following treatment with medial UKA. This variability challenges the assumption of uniform characteristics among knees with an identical wear pattern associated with anteromedial OA and emphasizes the complexity and variability of this specific form of OA. Following medial UKA, 45% of knees maintained their preoperative CPAK phenotype. Therefore, when aiming for pre-arthritic alignment or phenotype restoration through individualized approaches, it may be of significance to recognize the inherent phenotypic variations when performing medial UKA.