Nuclear scintigraphic retrospective study of the C6/7 articular facets of the equine cervical spine

Abstract

The objectives of this study were firstly, to determine an objective grading system of radiopharmaceutical uptake in the C6/7 articular facets of the cervical spine as a predictor of clinical signs in warmblood sporthorses; and secondly to establish an objective absorption coefficient (AC) value that could possibly differentiate between presence or absence of clinical signs in this region. 308 scintigraphic views of the cervical spine in 154 German warmblood horses were evaluated. Scintigrams were divided into clinically normal (60) and clinically abnormal (94) groups of horses. Horses were grouped according to performance type and age. Uptake coefficients using C3/4 as a reference point were established. Sensitivity and specificity for detection of neck pain and radiographic abnormalities were assessed. Receiver operating characteristic (ROC) analysis was used to determine a cutoff point for distinguishing between clinically normal and abnormal horses. An AC value of 1.243 at the C6/7 cervical vertebral facets separated clinically normal from clinically abnormal horses. Values decreased slightly with increasing age of the horses, and were highest in the middle age. There was a significant difference in AC values between clinically normal and abnormal horses in the dressage and show jumping groups. The best predictive values were established for horses in the show jumping category where scintigraphic findings correlated with clinical signs. An AC value of 1.235 at the C6/7 cervical vertebral facets reliably separates pathological from physiological uptake. However, age and performance type of the horses should be taken into account when interpreting these findings.

Equine skeletal scintigraphy: Comparing lesion detection ability of methylene diphosphonate and hydroxymethylene diphosphonate in the caudal cervical and proximal metacarpal/metatarsal regions

“…37 The current study confirmed a clinically 'significant' IRU in the articular processes of C6/C7 using the AC. 25 In the survey conducted by Gerlach et al, 25 the coefficient had the most significant value for sports horses aged between 11 and 15 years. Since 84% of the study population consisted of dressage or show jumping horses with a median age of 9 years, the AC was considered suitable to define areas of IRU, representing pathological and possibly clinically significant changes in the articular processes of C6/C7.…”

“…The scintigraphic appearance of cervical vertebrae is also reported to be highly variable in horses lacking clinical evidence of cervical dysfunction, depending on the age and use of the animal, the size of the articular processes and the thickness of the surrounding soft tissue layers. 17,25,36 Other authors consider an IRU at C6/C7 as an abnormal finding, regardless of clinical signs. 37 The current study confirmed a clinically 'significant' IRU in the articular processes of C6/C7 using the AC.…”

“…was determined by the first author (S.S.), as described below. A potentially clinically relevant IRU was considered to be present only with an AC value of 1.2 or more 25 . Horses showing significant IRU at other localisations were excluded.…”

“…A potentially clinically relevant IRU was considered to be present only with an AC value of 1.2 or more. 25 Horses showing significant IRU F I G U R E 1 Flowchart displaying information about the number of horses included in the study according to the inclusion criteria established for each group. Abbreviations: AAEP, American Association of Equine Practitioners; AC, absorption coefficient; CS, cervical spine; HMDP, hydroxymethylene diphosphonate; IRU, increased radiopharmaceutical uptake; MDP, methylene diphosphonate; n, sample size; NB, nerve block; pal., palmar; pl., plantar; PMR, proximal metacarpal/metatarsal region.…”

“…To achieve a more reliable distinction between potentially pathological and physiological uptake patterns at C6/C7, the AC was determined by the first author (S.S.). 25 Uptake coefficients were calculated using the articular process of the third (C3) and fourth (C4) cervical vertebrae as a reference point. Only horses with an AC of 1.2 or more were included in the study.…”