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Objective

To determine if currently used ground reaction force (GRF) normalization methods are accurate and precise enough to be used on a single-limb basis.

Study Design

Prospective clinical trial.

Animals

Clinically normal (n = 69) dogs and 40 dogs with unilateral ruptured cranial cruciate ligaments (CCL).

Methods

Pelvic limb GRFs of orthopedically normal dogs and those with unilateral ruptured CCL were collected. Normalization methods included none, body weight (BW), withers height (WH), WH and relative velocity (WH*F) and principal component 1 (PC1). Normalization methods were evaluated both by individual GRFs and additively. Binary logistic regression was performed for all normalization methods; sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) calculated. Stepwise backward logistic regression was used; significant values were retained in the final model. P < .05 was significant.

Results

Normalization of contact time (CT) by BW uniformly increased sensitivity, specificity, PPV, NPV, and accuracy. SI was the most accurate at both the walk and trot (accuracy 80–96%). Normalization by BW, WH, and WH*F all achieved similar results. When normalized GRFs were added, the accuracy increased only at the walk.

Clinical Significance

CT should be normalized to BW. SIs remain the gold standard, if SIs cannot be used, combining GRFs normalized to BW will result in high precision (80%) and high accuracy (89.5%) at the walk. At the trot, normalization by BW, WH and WH*F results in consistent results for the individual GRFs, though not all accuracies are >80%.