Ultrasound-Based Statistical Shape Modeling for Quantifying Femoral Trochlear Bone Shape Post-ACLR.

OBJECTIVE

Traditional assessments of femoral bone shape are inaccessible and do not adequately describe the full complexity of concave bone shape. We aimed to develop and validate an ultrasound-based statistical shape model (SSM) and derived bone shape score (B-Score) to quantify femoral trochlear bone shape morphology associated with anterior cruciate ligament reconstruction (ACLR).

DESIGN

Cross-sectional investigation involving 20 individuals with and 28 individuals without a history of ACLR. Bilateral ultrasound images of the femoral trochlear groove were acquired and analyzed. Both the SSM and B-Score were validated using 5-fold cross-validation, assessing reconstruction and classification accuracy, respectively.

RESULTS

In held out test data, the SSM captured over 99% of the bone shape variance with minimal reconstruction error (RMSE = 0.027 ± 0.004 mm). On test data, the B-Score accurately quantified bone shape associated with ACLR, demonstrating high accuracy (92.42%), sensitivity (97.37%), specificity (85.71%), and AUROC (0.95). A B-Score threshold of 1.41 standard deviations from the mean healthy bone shape was identified for classifying ACLR history.

CONCLUSIONS

The ultrasound-based SSM and derived B-Score provide a valid and accessible method for quantifying femoral trochlear bone shape changes post-ACLR. This approach offers potential for early detection of bone shape changes associated with disease and injury, improving long-term outcomes for ACLR patients. Future research should focus on enhancing model generalizability and assessment of bone shape changes longitudinally.