340 - The Normal Heights of Disc and Facet Joint Space in Cervical Spine. Ra...

#340 The Normal Heights of Disc and Facet Joint Space in Cervical Spine. Radiographic Parameters Based on Plain X-ray and CT in the Korean Population

Cervical Therapies and Outcomes

Poster Presented by: D. Lee

Author(s):

D.-H. Lee (1)
H.S. Lee (1)
H. Noh (1)
J.J. Yang (2)
C. Hwang (1)

(1) Asan Medical Center, University of Ulsan, Orthopedic Surgery, Seoul, Korea, Republic of
(2) Dongguk University Ilsan Hospital, Orthopedic Surgery, Ilsan, Korea, Republic of

Abstract

Introduction: A few scoring systems for cervical disc and facet joint, using radiograph or CT scan, have been developed. However the definitions of abnormal disc height and abnormal joint space are not clear in the previous papers. To our knowledge there is no study describing the radiologic normal value of the cervical disc height and the facet joint space. So we measured the cervical disc height and facet joint space of the Korean population to see the average value of it and investigate whether the disc height or the facet joint space are correlated to the demographic data of the person.

Methods: We performed a retrospective review of all the patients who underwent artificial disc replacement(ADR) at the cervical spine in our department from May 2006 to September 2011. All the patients obtained C-spine lateral X-Ray, CT scan, and MRI, preoperatively. We collected the demographic data - age, height, weight, BMI - of the patients and measured the disc heights and facet joint spaces from C2-3 to C6-7 using lateral X-ray and CT scan. Written instructions including figures were given to two orthopedic surgeons.(Figure1) They independently measured the disc heights and joint spaces twice. Average of the middle two valueswas calculated.Two radiologist reviewed the radiologic data(X-Ray, CT, MRI) and checked if there were any degenerative changes at the discs and the facet joints. The disc or the facet joint with any degenerative changes was excluded.We calculated the ratio of C2-3 height to the height of the other segments and named it the height ratio. For example, if the disc height of C2-3 is 5mm and C3-4 is 4mm, the C3-4 height ratio is 0.8(4/5).Average, standard deviation, 95% confidenceinterval of the disc height, height ratio and facet joint space were calculated.Correlations between the disc height and the demographic data, the facet joint space and the demographic data were analyzed.

Results: 37 patients(M:F=19:18) were evaluated in this study.The average age was 44.3 years (Range 33-56). The average height was 164.8cm(Range 146.6-183.5) and the average weight was 66.9kg(Range 41-119.6). 170 intervertebral discs and 356 posterior facet jointswere evaluated. The lower end of the 95% confidence interval of the disc space were at least bigger than 5.0mm when it was measured by X-Ray and at least bigger than 4.5mm when it was measured by CT scan. The lower end of the 95% confidence interval of the height ratio measured by X-Ray and CT scan was at least bigger than 0.9. The lower end of the 95% confidence interval of the joint space was at least bigger than 1.4mm when it was measured by X-Ray and was at least bigger than 1.2mm when it was measured by CT scan. There were positive correlations between height and disc height, and, height and facet joint space.

Conclusion: The radiologic normal value given above may be used as a reference in clinical situations and further studies.