Surgeons met sagittal alignment goals in one-third of patients with adult spinal deformity
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CHICAGO — Results presented at the North American Spine Society Annual Meeting showed surgeons met preoperative sagittal alignment goals in about one-third of patients with adult spinal deformities.
“Despite the ability for surgeons to preoperatively generate alignment goals and a specific surgical strategy, it remains unclear whether preoperative alignment goals are consistently translated and achieved in the operative room,” Justin S. Smith, MD, PhD, vice chair and chief of spine division and Harrison Distinguished Professor in the department of neurosurgery at the University of Virginia, told Healio/Orthopedics Today. “The primary objective of our study was to prospectively assess how often the operating surgeon’s preoperative goals for sagittal alignment following complex [adult spinal deformity] surgery were achieved.”
Goal achievement
Smith and colleagues, through the International Spine Study Group, used standardized forms to collect data among 266 patients with adult spinal deformities. Researchers required the operative surgeon to document sagittal alignment goals, including sagittal vertical axis (SVA), pelvic incidence to lumbar lordosis (PI-LL) mismatch and thoracic kyphosis (TK), prior to each surgery.
“We compared the goal alignment parameters from the respective surgeons with the achieved alignment goals on follow-up X-rays,” Smith said at the meeting.
About 66% of patients achieved the goals for each of the sagittal alignment measures (SVA, PI-LL mismatch and TK) and about one-third (37%) of patients achieved all three goals following surgery, he said, adding that surgeons tended to undercorrect SVA and PI-LL and increase TK.
Factors associated with failure
Factors associated with failure to achieve the SVA goal included a greater body mass index, worse deformity at baseline, lower TK and N-type Scoliosis Research Society-Schwab curve, according to Smith.
“For PI-LL mismatch, the factors that were associated with failure to achieve the goal included younger age of the patient, greater maximum coronal Cobb angle at baseline, lower pelvic tilt and lack of pelvic instrumentation,” he said.
Factors associated with failure to achieve the TK goal included older patient age, greater SVA at baseline, the specific surgeon, use of surgical planning software, use of age-adjusted alignment criteria and early proximal junctional kyphosis, Smith said.
He said 38% of surgeons used commercially available planning software, while the remaining surgeons used a simple workstation to plan their surgeries. Smith said 38% of surgeons employed age-adjusted alignment goals and 62% performed an individualized patient assessment of what the surgeon’s goals would be for alignment.
“For the multivariate factors — so these are independent factors associated with failure to achieve these alignment goals — for SVA, [it] was greater preoperative SVA and lower preoperative thoracic kyphosis,” Smith said.
Independent factors associated with failure to achieve PI-LL mismatch goals included primary cases, three-column osteotomy, lack of iliac instrumentation and use of surgical planning software, according to Smith. Adjusted alignment criteria and early proximal junctional kyphosis were independent factors associated with failure to achieve TK goals, he said.
“Lastly, for all three parameters, the independent factors associated with failure to achieve all three goals was use of surgical planning software and greater global malalignment in the sagittal and coronal planes,” Smith said.
“Importantly,” according to Smith, “our findings do not suggest that surgeons shouldn’t use planning software or age-adjusted alignment criteria. It may be that the goals defined by using these approaches produce better but more rigorous goals that are more challenging to achieve.”
- Reference:
- Smith JS, et al. Paper 51. Presented at: North American Spine Society Annual Meeting; Oct. 12-15, 2022; Chicago.
- For more information:
- Justin S. Smith, MD, PhD, can be reached at Spine Care Fontaine, 3rd Fl., 415 Ray C. Hunt Dr., Charlottesville, VA 22903; email: jss7f@virginia.edu.
Perspective
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The study by Smith and colleagues is interesting, particularly because I was surprised by the low percentage of surgeons who are meeting the acceptable outcome from an alignment standpoint. These are the best deformity surgeons in the world who are still only “getting it right,” so to speak, 25% of the time. It just proves that we still have a lot to learn about what we’re doing from an intraoperative corrections standpoint and how that translates into postoperative alignment.
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