NASS News: Is There an Optimal Cervical Fusion Length?

How low is too low?

That question formed the basis of a study that challenges the conventional positioning of long posterior cervical spinal fusion.

“Conventional wisdom says that if we fuse low enough on the cervical spine to the C7 vertebra level, then we should go even lower, to the upper thoracic spine, to reduce risk and prevent further degeneration and reoperation,” said Michael, D. Daubs, M.D., an orthopedic surgeon and North American Spine Society (NASS) Annual Meeting Program chair. “This study indicates that these are unfounded concerns and that we should adopt a ‘less is more’ approach.”

The study, “Can Long Posterior Cervical Fusions Be Safely Stopped at C7 Instead of the Upper Thoracic Spine?” was among 21 “Best Papers” selected by NASS from the record 1,180 scientific abstracts and session proposals submitted for this year’s 30th Annual Meeting, held Oct. 14-17 in Chicago, Ill.

In the single-center retrospective cohort study, 105 adult patients underwent posterior instrumented fusion of at least three cervical motion segments, including the C7 vertebra, the lowest cervical vertebra at the neck base. Seventy-six of those patients (72 percent) had a minimum one-year follow-up. Twenty-two patients (29 percent) underwent fusions with a lowest instrumented vertebra stopping at C7 (“C7-LIV cohort”) and 54 patients (71 percent) had fusions that crossed the cervicothoracic junction, with a lowest instrumented vertebra at the thoracic spine (“T-LIV cohort”). All charts and radiographs were reviewed to obtain preoperative and minimum one-year postoperative data. The mean age was 58.6 years and a mean follow-up was three years (range of one to eight years). There were no significant baseline differences between cohorts in gender, primary versus revision surgery, tobacco use or body mass index.

The study’s authors orginially hypothesized that stopping posterior fusion surgery at the C7 vertebra would cause a higher rate of C7-T1 degeneration requiring reoperation, as well as a greater loss of cervical lordosis (normal curvature) and sagittal alignment.

Actually, the reoperation rate was not significantly different between the two cohorts. Only two C7-LIV patients (9 percent) required distal extension of their fusions. In addition, blood loss was significantly greater for T-LIV patients versus C7-LIV patients (279 mL vs. 173 mL). Operative duration was greater for the T-LIV patients and approached significance (268 minutes vs. 234 minutes). The complication rate was greater in the T-LIV cohort (20 percent) than in the C7-LIV cohort, but was not significant.

The study’s authors concluded that stopping fusions at C7 did not increase the risk for subsequent reoperation compared with fusions crossing the cervicothoracic junction and led to less operative blood loss. A C7 stopping point did not predispose patients to loss of cervical lordosis (normal curvature) or cervical sagittal imbalance and patient-reported outcomes demonstrated equivalence.

The study authors are David B. Bumpass, M.D., and Jacob M. Buchowski, M.D., M.S., from Washington University in St. Louis, Mo.; and Lukas P. Zebala, M.D., Jacob A. Haynes, M.D., Mikhail Roubakha, B.S., and K. Daniel Riew, M.D., from Washington University School of Medicine in St. Louis.