Coronal plane alignment of the knee (CPAK) phenotypes and their relationship with gap patterns in robotic-assisted total knee arthroplasty: a clinical trial.
Filippo Migliorini, Luise Schäfer, Jens Schneider et al.
✦ AI-curated · Sources linked
In 30 seconds
This prospective clinical trial series examined whether coronal plane alignment of the knee (CPAK) phenotypes were associated with intraoperative gap patterns in 285 patients undergoing robotic-assisted total knee arthroplasty. Medial and lateral gaps were recorded in extension and flexion and classified as balanced, varus, or valgus. Compared with CPAK IV, CPAK I and II were associated with greater odds of varus gaps in both positions; for example, extension odds ratios were 5.41 and 3.38, respectively. CPAK VII was associated with lower odds of varus gaps in extension (OR 0.23).
Key findings
- Compared with CPAK IV, CPAK I and II had higher odds of varus gaps in extension (OR 5.41 and 3.38, respectively).
- CPAK I and II also had higher odds of varus gaps in flexion (OR 1.58 and 2.20, respectively).
- CPAK VII was associated with lower odds of varus gaps in extension (OR 0.23).
- Even valgus-aligned phenotypes showed varus-dominant gap behavior in flexion.
Why it matters
The findings suggest that intraoperative gap patterns are related to constitutional knee alignment phenotype, not solely to surgical alignment. Recognising this relationship may help clinicians interpret measured gaps in context and understand why similar alignment targets can be accompanied by different soft-tissue balance patterns.
What to keep in mind
The study reports associations in a prospective series; it does not establish that CPAK-guided planning improves clinical outcomes.