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Vertico-horizontal atlantoaxial index (VHAI): A new craniovertebral radiographic index
Jiajie Xia1, Rami Darwazeh2, Cheng Cheng3
1Department of Neurosurgery, Shaoxing Central Hospital, Shaoxing, China.
Objective:
The purpose of this study was to develop a new index that can reliably quantify the reduction of basilar invagination with atlantoaxial dislocation.
Patients And Methods:
Between May 2012 and September 2017, 40 patients with congenital basilar invagination and atlantoaxial dislocation as well as 100 sex-and age-matched control subjects were recruited for this study. All patients underwent direct posterior reduction and fixation. Mid-sagittal computerized tomography scan films were obtained before and after surgery as well as the vertico-horizontal atlantoaxial index (VHAI) was measured in all patients -before and after surgery- and controls. Additionally, the pre-and postoperative Japanese Orthopedic Association (JOA) scores, Nurick grading, European Myelopathy Score (EMS) and Prolo Scale score were used to evaluate the cervical myelopathy.
Results:
The mean follow-up was 24.75 months with a range of 6-60 months. The mean value of VHAI in the control group was 87.86 ± 24.98 mm2, while the mean values of VHAI before and after surgery were 209.45 ± 96.80 mm2 and 95.08 ± 66.95 mm2, respectively. Additionally, in the patient group, a negative correlation was observed between JOA, EMS, Prolo Scale scores and VHAI. On the other hand, a positive correlation was found between the Nurick grading and VHAI.
Conclusion:
The VHAI can be an excellent measurement tool to evaluate the reduction of basilar invagination with atlantoaxial dislocation. There was a negative correlation between VHAI and JOA, EMS and Prolo Scale scores, and a positive correlation with Nurick grading; which indicates the effectiveness of this index.
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