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The Spine Blog

Friday, May 15, 2020

When is it safe to stop at the thoracolumbar junction?

When treating adult spinal deformity, there is a substantial minority of patients in whom stopping the fusion at L1 or T12 would be appealing other than concerns related to failure at the thoracolumbar junction (TLJ). For patients who require fusion above the L2 level, surgeons tend to reflexively extend the fusion to T10 in order to prevent proximal junctional failure (PJF). In order to define a subgroup of patients for whom stopping at the TLJ is acceptable, Dr. Park and colleagues from Seoul retrospectively reviewed a case series of 63 adult deformity patients over age 50 who underwent fusion from T11, T12 or L1 to the sacrum or pelvis. About 75% had pelvic fixation, and 71% had L1 as the upper instrumented vertebra (UIV). They defined PJF as a proximal junctional kyphosis greater then 20 degrees, UIV or UIV+1 fracture, or screw pullout. The average follow-up was over four years. Ninety percent of patients were female, and the average age was 67. They found that 37% of patients developed PJF at a mean of 9 months after surgery, and one third of these patients had revision surgery with fusion to T3 or T4. Univariate analysis revealed that increasing age, osteoporosis, increased pre-operative pelvic tilt, and baseline kyphosis at the junctional level were significantly associated with PJF. There were trends suggesting that a greater correction of pelvic tilt and lumbar lordosis  were also associated with PJF. In multivariate analysis, increasing age, osteoporosis, and baseline kyphosis at the junctional level were all independent predictors of PJF. The PJF patients had significantly worse ODI scores (49 vs. 31) and SRS-22 scores at final follow-up. The authors suggested that stopping at the TLJ should be avoided in patients over 70, osteoporotic patients, and those with baseline kyphosis at the junctional level as 56% of patients with just one of these risk factors experienced PJF. Conversely, none of the patients without these risk factors had PJF.

The authors have done a nice analysis of their case series of adult spinal deformity patients with the UIV at T11, T12, and L1. Over one third of these patients developed PJF, indicating that avoiding stopping at the TLJ is generally a good idea. Their analysis of risk factors for PJF helps to define the group of patients for whom stopping  at the TLJ is reasonable, namely younger patients with good bone quality and no baseline kyphosis at the junctional level. Similar to prior studies, they identified more aggressive correction as a risk factor for PJF, though this did not reach statistical significance. This study was limited by relatively small numbers, and the PJF group included only 23 patients. Such a small group limits the power of risk factor analysis, so some PJF risk factors may have been missed due to Type II error. Additionally, the study did not include a comparison group in whom fusion was performed to T10 or above. It is possible that extending the fusion to T10 in the PJF patients may not have prevented the complication. While performing an RCT to answer this question would be difficult, the authors likely had a large cohort of patients fused to T10, and this could have been used as a comparison group to help answer the question. This paper does suggest that stopping at the TLJ is a reasonable option for a subgroup of adult deformity patients who are younger, have good bone, no baseline kyphosis at the junctional level, and who do not need a major correction of sagittal deformity.

Please read Dr. Park's article on this topic. Does this change your opinion of stopping a fusion at the TLJ?

Adam Pearson, MD, MS

Associate Web Editor