Repeatability and Intra‐ and Inter‐observer Agreement of Cervical Vertebral Sagittal Diameter Ratios in Horses with Neurological Disease

Abstract

BackgroundSagittal ratio values (SRVs) of cervical vertebrae are used for ante‐mortem diagnosis of cervical vertebral stenotic myelopathy, but intraobserver and interobserver variability in measurement may influence radiographic interpretation of vertebral stenosis in horses with neurological disease.ObjectivesTo determine intraobserver repeatability in SRVs, intra‐ and interobserver agreement in SRVs and whether or not agreement was influenced by animal age.AnimalsForty‐two horses (>1 year old) with neurological disease from which laterolateral computed radiographic images of C2–C7 were obtained.MethodsFour observers made measurements from C2 to C7 for each horse and interobserver agreement for intra‐ and intervertebral SRVs was determined using Bland–Altman analysis (acceptable agreement: limits of agreement [LOA] ≤ 0.05) on all horses and those ≤3 (n = 25) and >3 (n = 17) years old. Each observer also made repeated measurements for 10 horses and intraobserver repeatability and agreement were determined.ResultsAdequate intraobserver repeatability was achieved for 6 sites. Within observers, paired measurements had a median difference ≤5.7%, but a large range in differences often occurred, most frequently at intervertebral sites. For C5, C6, C7, and C3–4, LOA ≤ 0.05 were achieved by at least 1 observer. With the exception of C5 for 1 pair, LOA were >0.05 for interobserver agreement, regardless of animal age. LOA were largest at intervertebral sites.Conclusions and Clinical ImportanceWithin and between observers, measurement error may limit the diagnostic accuracy of SRVs and result in discrepancies of diagnosis and treatment and warrants consideration when used clinically in horses with neurological disease.

Prevalence of Anatomical Variation of the Sixth Cervical Vertebra and Association With Vertebral Canal Stenosis and Articular Process Osteoarthritis in the Horse

“…Interestingly, although horses with anomalous C6 were more likely to have an intravertebral sagittal ratio less than 0.5, they were less likely than horses with normal C6 to have neurologic deficits attributable to the cervical region. This highlights the lack of accuracy of the intravertebral sagittal ratio for diagnosis of cervical vertebral stenotic myelopathy . Initially the intravertebral sagittal ratio was reported to have sensitivity and specificity as high as 89% for identification of cervical stenotic myelopathy .…”

“…Both neurologic dysfunction and perceived cervical pain are subjective assessments that vary between individuals . A limitation of the radiographic assessment was the use of the intravertebral ratio, as this measurement has been reported to be unreliable with variation of 5–10% . The main reason for including this parameter in the study was as part of the morphometric study, to refer to parameters commonly used, and not as a diagnostic test.…”

Magnetic motor evoked potentials of cervical muscles in horses

“…Also in horses, many studies highlight the controversy, difficulties and limitations of cervical radiography, myeolography, computed tomography (CT), magnetic resonance imaging (MRI) and myeloscopy to diagnose spinal cord disease. Sensitivities (47–50%) and specificities (70–78%) of cervical radiographs and sagittal ratio calculations are too low for adequate diagnosis of spinal cord compression [ 5 , 6 ] and variation between observers is high [ 7 ]. Myelography also has a low sensitivity (43–85%) and additionally requires general anesthesia and intrathecal contrast injection [ 6 , 8 ].…”

Comparison of the clinical and radiographic appearance of the cervical vertebrae with histological and anatomical findings in an eight-month old warmblood stallion suffering from cervical vertebral stenotic myelopathy (CVSM)

“…Despite the fact that the value of the intravertebral ratio at the C4/C5 site was lower than 48.5%, and that the intervertebral ratio considered more specific was lower than at C3/C4, which, based on the cited study, could have high diagnostic value, was not confirmed in the measurements performed during the myelography [8, 9]. This may have been caused by differences in the assessment of the cervical radiographs [12]. However, myelography is considered an important intravital diagnostic tool that enables the qualification of patients for cervical vertebral stabilisation surgery, therefore our study focused on the C3/C4 analysis.…”