Does yearling laryngeal function in thoroughbreds that underwent a prosthetic laryngoplasty differ from horses of unknown outcome?
Hardwick JL*1, Ahern BJ*2, Crawford KL2, Allen KJ3, Franklin SH4
1Murdoch University, Perth, Australia, 2University of Queensland, Queensland, Australia, 3University of Bristol, Bristol, United Kingdom, 4University of Adelaide, Adelaide, Australia.
Objectives:
The yearling laryngeal function (YLF) of horses that subsequently underwent a prosthetic laryngoplasty (PL) is unknown. We hypothesised horses with YLF ≥grade II.2 would be at increased risk of requiring PL, compared to YLF <grade II.2.
Methods:
A 1:4 case-control study, including PL cases from 2019-2021 with an available yearling post-sale videoendoscopic examination and matched controls. Two blinded observers graded YLF using the Havemeyer system. The risk of PL for each YLF grade was calculated using multivariable conditional logistic regression.
Results:
There were 150 PL cases and 600 controls. The proportions of each YLF grade in the PL group and control group respectively were grade I: 13.3% and 25.8%, grade II.1: 35.3% and 54.3%, grade II.2: 26% and 16.7%, grade III.1: 20.7% and 3%, grade III.2: 3.3% and 1.7%, grade III.3: 0.7% and 0%, grade IV: 0.7% and 0%. The odds ratio (OR, 95% confidence interval) of requiring PL compared to the referent grade I were: grade II.1: 1.2 (0.7, 2.2, p=0.48), grade II.2: 3.38 (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: 2930000 (398173.7, 21600000, p<0.001), grade IV: 26300000 (3420000, 202000000, p<0.001). Yearling LF ≥grade II.2 had an OR of 4.61 (3.0, 7.1, p<0.001) compared to <grade II.2; YLF ≥grade III.1 had an OR of 10.7 (5.6, 20.4, p<0.001) compared to <grade III.1.
Conclusions:
Three-quarters of the PL group had ≤grade II.2 YLF and deterioration in LF post-sale was common. The risk of requiring PL increased from YLF grade II.2 upwards.