A New Technique for Intraoperative Reduction of Occipitocervical Instability

The Severity of Basilar Invagination and Atlantoaxial Dislocation Correlates With Sagittal Joint Inclination, Coronal Joint Inclination, and Craniocervical Tilt

“…Only during the past few years have we been able to fully grasp the utility of joint distraction and the value of specific intraoperative manipulations. 4,5,7,9,10,13,30 With the advent of such intraoperative joint-manipulation surgeries, it thus becomes necessary to study joint morphology and, if possible, to develop new indexes to objectively define their abnormalities. Understanding complete joint morphology in normal individuals and in patients with AAD and BI is important because it provides the surgeon with increased knowledge when performing joint distractions and deformity-correcting manipulations.…”

“…[4][5][6] Many authors have recently suggested that the atlantoaxial joint may be responsible for the development of this pathology but have not performed studies to substantiate their claims. [4][5][6][7][8][9][10] Although a number of craniobasal indexes (eg, the Wackenheim line, McRae line, and Ranawat line) have previously been described to objectively measure the severity of BI and AAD, 11,12 no study to date has defined any measurements to quantify abnormalities in the atlantoaxial or occipito-C1/C2 joints. The senior author (P.S.C.)…”

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“…It is also important to note that patient selection is critical to ensure successful application of this technique. The reduction maneuvers place a high degree of stress across the bone-screw interface, though much less than those described earlier, [16,17] due to the spacers also acting as a channel for significant weight transmission. However, it is imperative that the screws have adequate cortical purchase to prevent hardware failure.…”

“…Hsu et al [16] overcame this shortcoming by describing a novel technique in two cases of acquired (one infection and other in metastasis) occipito-cervical instability. Here, apart from intraoperative occipito-cervical distraction, they also provided an extension of neck by applying compression between the upper occipital screw and another screw tightened more superiorly on the rod, which resulted in correction of AAD.…”

“…To minimize this, it is important to provide distraction of not more than 5-6 mm, just enough to place in the spacers. Hsu et al [16] have described the use of intraoperative ultrasound to ensure adequate spinal cord decompression during the reduction maneuvers. We have only used fluoroscopic guidance during DCER.…”