Inter‐ and intra‐observer agreement for grading radiographs of thoracolumbar spinous processes in healthy horses during a pre‐purchase examination

Abstract

Background There is wide variability in radiographic grading systems in thoracolumbar spinous processes in horses. The aim of this study was to determine the agreement of grading different parameters, and combinations of those, in radiographs of the spinous processes of the equine thoracolumbar spine in the scope of a pre‐purchase examination. We hypothesized that agreement is variable and interpretation of these radiographs is difficult. Methods Radiographs of the thoracolumbar spine of healthy horses (N = 100) were assessed by three observers. Spinous processes were separately graded for interspinous space width, modelling, radiopacities, radiolucencies and isolated opacities dorsally. Inter‐ and intra‐observer agreement was assessed for individual and combinations of parameters. Results Agreement (inter‐ and intra‐observer) was good for the following parameters: interspinous space width, isolated opacities dorsally, beak‐shaped formations craniodorsally and modelling cranioventrally. The agreement increased slightly for a sum of specific parameters such as radiopacities, modelling, dorsal abnormalities and related abnormalities involving increased opacity, modelling and osseous cyst‐like lesions. Agreement for the total radiographic abnormalities per back was moderate. Conclusions Grading of thoracolumbar radiographs in horses without back pain showed good inter‐ and intra‐observer agreement for specific parameters and these should be used in future grading of spinous processes. Limitations should be considered in pre‐purchase examinations.

Should radiographs of the thoracolumbar spine remain part of the pre‐purchase examination?

“…Regardless of the system and machine used, there are several other elements described which may also contribute to the difficulty of image interpretation of the SP (Looijen et al., 2022). The impossibility of orthogonal views, scatter radiation and magnification due to increased film‐patient distance may result in variable quality of radiographs (Looijen et al., 2022).…”

“…Regardless of the system and machine used, there are several other elements described which may also contribute to the difficulty of image interpretation of the SP (Looijen et al., 2022). The impossibility of orthogonal views, scatter radiation and magnification due to increased film‐patient distance may result in variable quality of radiographs (Looijen et al., 2022). Measuring the interspinous spaces of the equine thoracolumbar spine on computed tomographic images in comparison to radiographs resulted in inconsistencies in those measurements, most likely due to geometric distortion because of x‐ray beam angulation (Djernæs et al., 2017).…”

“…Very common radiographic abnormalities associated with the thoracolumbar spine are those associated with the SP. They can show huge variability in their size, shape and margin but also in radiopacity and interspinous space width (Figures 4 and 5) (Looijen et al., 2022; Zimmerman et al., 2012). The main location of narrow interspinous spaces is the caudal saddle region and the cranial lumbar spine (T14–L2), which is reported consistently in the literature (Butler et al., 2017; Haussler et al., 1999; Henson & Kidd, 2009; Jeffcott, 1979, 1980; Townsend et al., 1986).…”

“…A limited number of studies described a grading system originating from a sum of grades per SP rather than a generalised summary of abnormalities (Erichsen et al., 2004; Zimmerman et al., 2011). Only recently has it been described that inter‐ and intraobserver agreement on the severity of radiographic abnormalities offers only selective reliability when grading SP (Looijen et al., 2022). Most of all, a general consensus on its clinical relevance has never been established (Looijen et al., 2022).…”

The Value of Thoracolumbar Radiography for the Judgment of Horse Soundness and the Pre-purchase Requirement

“…Table 1: Criteria of the thoracolumbar segment radiographic assessment (Looijen et al, 2021). Interspinous space width (ISW)…”