Assessment of radiographic healing after tibial plateau leveling osteotomy in young and older dogs using the modified RUST scoring system.

Objective: To compare radiographic osteotomy healing scores after tibial plateau leveling osteotomy (TPLO) in young (2-5 years) and old (8-12 years) dogs using the modified Radiographic Union Score for Tibial fractures (mRUST) system, and to evaluate agreement between large language model-assisted interpretation (LLM), surgeon, and surgical resident scoring. Study design: Client-owned, 20-40 kg dogs treated with unilateral TPLO at ages 2-5 or 8-12 years between 2023 and 2025 were retrospectively identified. Dogs with endocrinopathy or atypical TPLO or recovery were excluded. Dogs were assigned to Group 1 (2-5 years) or Group 2 (8-12 years). 8-week postoperative radiographs were scored independently by an LLM, a surgeon, and a surgical resident using the 4-point mRUST system. Scores were compared between age groups using the Wilcoxon rank-sum test, and interrater agreement was assessed using an intraclass correlation coefficient (ICC). Results: Group 1 had 49 dogs; Group 2 had 51 dogs. Group 1 had a mean (SD) age of 3.82 (1.11) years, while Group 2 had a mean (SD) age of 9.24 (0.99) years. mRUST scores did not differ between age groups across LLM ( Conclusion: Chronological age was not associated with mRUST score following TPLO at the 8-week postoperative evaluation. The mRUST system demonstrated moderate agreement between human observers. LLM scoring showed promise; further refinement is needed for clinical application.