Yearling laryngeal function in Thoroughbreds that underwent a laryngoplasty differs from controls

Background Yearling laryngeal function (YLF) is frequently assessed at the time of sale and the outcomes of these assessments can have significant economic implications. The YLF of horses that subsequently underwent a prosthetic laryngoplasty (PL) is unknown. Objectives We hypothesised horses with YLF ≥grade II.2 would be at increased risk of requiring PL, compared with YLF <grade II.2. Study design Case–control. Methods There were 150 PL cases from 2019 to 2021 with an available yearling post‐sale videoendoscopic examination and 600 controls. Two observers unaware of the outcome graded YLF using the Havemeyer system. The risk of PL for each YLF grade was calculated using multivariable conditional logistic regression. Results The proportions of each YLF grade in the control group and PL group, respectively, were grade I: 25.8% and 13.3%, grade II.1: 54.3% and 35.3%, grade II.2: 16.7% and 26%, grade III.1: 3% and 20.7%, grade III.2: 0.2% and 3.3%, grade III.3: 0% and 0.7%, grade IV: 0% and 0.7%. The odds ratio (OR, 95% confidence interval) of requiring PL compared with the referent grade I were: grade II.1: 1.2 (0.7, 2.2, p = 0.5), grade II.2: 3.4 (1.8, 6.1, p < 0.001), grade III.1: 13.8 (6.0, 31.6, p < 0.001), grade III.2: 55.5 (10.3, 299.2, p < 0.001), grade III.3: 2930,000 (398173.7, 21 600,000, p < 0.001), grade IV: 26300,000 (3 420 000, 202 000 000, p < 0.001). Yearling LF ≥grade II.2 had an OR of 4.61 (3.0, 7.1, p < 0.001) compared with <grade II.2; YLF ≥grade III.1 had an OR of 10.7 (5.6, 20.4, p < 0.001) compared with <grade III.1. Main limitations Lack of performance data to compare the PL and control groups. The control group was not ‘disease‐free’ and may have developed disease and been retired or undergone surgery elsewhere. Conclusions Three‐quarters of the PL group had ≤grade II.2 YLF, demonstrating deterioration in LF post‐sale was common. The risk of requiring PL increased from YLF grade II.2 upwards.