Predictive Modelling of Waist Reduction in the RibXcar Technique: Correlation Between Angularity of Monocortical Fracture and Aesthetic Result.

BACKGROUND

Aesthetic rib remodeling redefines the waistline through structural modification of the lower rib cage. Ultrasound-guided percutaneous RibXcar reduces rib angularity without skin incisions and contributes to waist narrowing. However, the relationship between rib angulation changes and long-term waist reduction remains insufficiently quantified.

OBJECTIVES

To evaluate the association between perioperative waist measurements, ultrasound-based rib angulation, and waist circumference at 12 months, and to develop a clinically applicable formula for expected waist reduction.

METHODS

This study included 257 patients who underwent RibXcar between January 2023 and January 2024. Waist circumference and rib angulation were measured at standardized time points during 12-month follow-up. A multiple linear regression model was developed using perioperative waist measurements and ultrasound-based rib angle variables. After initial model construction, collinearity diagnostics were performed using variance inflation factor and tolerance statistics, allowing refinement of the angular predictors included in the final equation. Model fit was evaluated using R2, adjusted R2, standard error, and regression ANOVA.

RESULTS

The revised model retained preoperative waist circumference, immediate postoperative waist circumference, preoperative R10 angulation, and immediate postoperative R11 and R12 angulations. It showed strong predictive performance for 12-month waist circumference (R = 0.910; R2 = 0.828; adjusted R2 = 0.825; standard error = 0.930 cm) and was statistically significant (p < 0.001). The equation was converted into a direct formula to estimate expected waist reduction.

CONCLUSIONS

Perioperative waist measurements combined with ultrasound-based rib angulation variables allow objective estimation of waist evolution after RibXcar. This model may support surgical planning and patient counseling, but requires external validation.