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Sagittal malalignment related to decreased quality of life after cervical fusion
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AMSTERDAM — Positive sagittal malalignment increased the severity of disability after multilevel cervical fusion, as demonstrated by its negative effect on health-related quality of life as seen in a recently presented study.
Data from the past decade have shown that sagittal malalignment is related to disability and unfavorable health-related quality of life (HRQOL) scores in the thoracolumbar population, but little research has involved sagittal balance in the cervical spine,
“To date, no study has looked at, specifically, cervical-sagittal balance,” Ames said during his presentation at SpineWeek 2012. “There has been a multitude recently of prior studies that have looked at cervical segmental and cervical regional lordosis, but no study has looked at sagittal alignment and outcomes in cervical fusion surgery [to our knowledge].”
Multilevel cervical fusion for stenosis
Ames and his colleagues conducted a retrospective study of 113 patients who underwent multilevel cervical fusion for cervical stenosis, myelopathy and kyphosis from 2006 to 2010. Average postoperative follow-up was 187 days. Researchers chose an intermediate 6-month follow-up to isolate the sagittal plane from the perioperative recovery effects of surgery but before the 1-year time point when patients are at risk for pseudoarthritis, which Ames noted may impact outcome scores.
Researchers obtained radiographic measures from all patients, including C1-C2 lordosis; C2-C7 lordosis; C2-C7 sagittal vertical axis (SVA), which is the distance between the C2 plumb line and C7; the center of gravity of head SVA, which is the distance between the external auditory canal plumb line and C7; and C1-C7 SVA, the distance between the C1 plumb line and C7.
This patient has good sagittal alignment in which the C2-C7 sagittal vertical axis (SVA) was 25 mm. This patient also had a raw Neck Disability Index (NDI) score of 10 indicating mild disability.
Images: Ames CP
“All of our X-rays are done at my institution in the standing position,” Ames said. “As is critical in assessing thoracolumbar alignment, cervical-sagittal alignment must be assessed with the patient standing because of the effect of the spinal pelvic parameters on the cervical translational parameter.”
Health-related quality of life (HRQOL) measures included the Neck Disability Index (NDI), visual analog scale for pain and SF-36 physical component scores.
Statistically significant correlations
Ames and his colleagues found NDI scores improved or remained the same as the preoperative score for 80% of the patients, while 20% of patients deteriorated. SF-36 physical component scores improved by about 22%.
The researchers found statistically significant correlations between the C2 plumb line and both the NDI and SF-36 physical component scores, as well as the C1 plumb line. “Furthermore, it was interesting to note that the C2 plumb line correlated significantly with C1-C2 lordosis, so increasing cervical-sagittal balance seems to increase hyperlordosis at the occipital-cervical junction,” Ames said.
Through regression analysis, the researchers also predicted a C2-C7 SVA cutoff value of 40 mm, beyond which correlations were most significant between NDI scores and the C2-C7 SVA.
This radiographic image shows a patient with poor sagittal alignment in which the C2-C7 SVA was 71 mm. This patient also had a raw NDI score of 34 indicating severe disability.
“We propose a C2 plumb line measured on standing X-rays of about 40 mm for the C2-C7 offset,” Ames said. “Beyond that, we are seeing significant correlations to worsened HRQOL.” – by Tina DiMarcantonio
Disclosure: Ames is a consultant for Depuy, Stryker and Medtronic and recieves research support from Depuy, Medtronic and Stryker.