Computed tomography-based classification of axis vertebra: choice of screw placement

Purpose The purpose of the study was to: (1) introduce a new CT-based parameter: free facet area and provide its normative data; (2) standardize the method of measuring isthmus width and height of the axis vertebra; (3) propose a new grading system to predict the difficulty in inserting transarticul...

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Bibliographic Details
Published in:European spine journal 2014-05, Vol.23 (5), p.1084-1091
Main Authors: Pruthi, Nupur, Dawn, Rose, Ravindranath, Yogitha, Maiti, Tanmoy Kumar, Ravindranath, Roopa, Philip, Mariamma
Format: Article
Language:English
Subjects:
Adult
Axis, Cervical Vertebra - anatomy & histology
Axis, Cervical Vertebra - diagnostic imaging
Female
Humans
Intervertebral Disc Displacement - diagnostic imaging
Intervertebral Disc Displacement - surgery
Male
Medicine
Medicine & Public Health
Neurosurgery
Original Article
Pedicle Screws
Surgical Orthopedics
Tomography, Spiral Computed
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Summary:Purpose The purpose of the study was to: (1) introduce a new CT-based parameter: free facet area and provide its normative data; (2) standardize the method of measuring isthmus width and height of the axis vertebra; (3) propose a new grading system to predict the difficulty in inserting transarticular and C2 pedicle screws. Methods Spiral CT scans of 47 adult dry axis vertebrae were studied. The methods of measuring isthmus width, isthmus height and free facet area are described. Results The mean isthmus width was 5.04 mm on the right side and 5.42 mm on the left side. The mean isthmus height was 5.21 mm on the right side and 5.45 mm on the left side. Mean free facet area was 61.23 % on the right side and 70.18 % on the left side. A novel grading system is proposed on the basis of these three parameters. As per this grading system, 40.4 % of the sides were found to be difficult for transarticular and 24.5 % sides for C2 pedicle screw insertion (total score 2, 3, 4). A Management protocol is suggested on the basis of the grading system. Conclusion Inserting a transarticular screw was more frequently difficult as compared to pedicle screw. A new CT-based parameter (free facet area) and an efficient grading have been proposed to help surgeons choose the appropriate screw options, appreciate the complex anatomy of this region and compare data across various studies.
ISSN:0940-6719
1432-0932
DOI:10.1007/s00586-014-3240-z