Sagittal malalignment related to decreased quality of life after cervical fusion

Issue: October 2012

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, Christopher P. Ames, MD, director of spine tumor and spinal deformity surgery, co-director of spinal surgery and the spine center and director of the Spinal Biomechanics Laboratory at the University of California San Francisco, said. 

“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. 

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.

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. 

“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 

Reference: 

Ames CP. The impact of positive regional sagittal alignment on outcomes in posterior cervical fusion surgery. Presented at SpineWeek 2012. May 28-June 1. Amsterdam. 

For more information:

Christopher P. Ames, MD, can be reached at the Department of Neurological Surgery, University of California San Francisco, 505 Parnassus Ave., Rm. M779, San Francisco, CA 94143; email: amesc@neurosurg.ucsf.edu.  

Disclosure: Ames is a consultant for Depuy, Stryker and Medtronic and recieves research support from Depuy, Medtronic and Stryker. 