I'd like to thank the scientific committee for accepting our work and thank you all for signing up to listen to this virtual presentation. These are my co-authors and I have no disclosures. Increasingly adult patients are requesting surgery for deformity correction because it improves the quality of their lives. One of the challenges of correction of adult spinal deformity is achieving a solid fusion. Despite improvements in surgical technique as well as implants, pseudoarthrosis rates, particularly the lumbar sacral junction remains high. There are several strategies to mitigate these pseudoarthrosis rates and these include the use of anterior column support, which potentially decreases non-union rates as well as reinforces sacral pelvic fixation. There is consensus that the use of sacral pelvic fixation decreases pseudoarthrosis rates. However, no such consensus exists with regards to the anterior column support technique utilized. Mainly are there differences in pseudoarthrosis rates if A-lifts versus T-lifts are utilized. Two main techniques to reinforce the sacral pelvic fixation, the lumbar sacral junction, include the anterior lumbar interbody fusion as well as the transforaminal lumbar interbody fusion. The theoretical advantages of the A-lifts are that it facilitates good restoration of lumbar lumbosis. It facilitates a thorough disc preparation for placements of a very large graft with a good interference fit. The cons of this approach are the significant morbidity associated with the approach is often need for an access surgeon. It usually requires a staged operation with multiple anesthetic exposures. The T-lifts on the other hand, the pros are it's a single stage surgery for most of the time. Most surgeons are familiar with these approaches, with this approach, and there are few anesthetic exposures which become important when you start dealing with an elderly patient population. The cons of this approach, theoretically, inadequate restoration of lumbar lumbosis, graft extrusion can be an issue, nerve irritation because of retraction during surgery, and certainly incidental durotomies. The objective then of this study were twofold. The primary objective was to compare the rod fracture rates in patients undergoing corrective surgery for deformity who had either an A-lift or T-lift procedure performed at the collar level of the lung fusion constructs. The secondary aim was to compare the radiographic and patient reported outcomes changes from baseline through two years between both groups. This was a retrospective single institutional study. There were 198 consecutive patients with a diagnosis of adult spinal deformity involved in this study. All patients had greater than five level fusions to the sacrum with iliac fixation, either S2AI versus traditional iliac bolts. The study period was between January 1, 2006 and December 31, 2014. The primary reasons for surgery were progressive deformity, mechanical back pain, or neurogenic claudication. All patients had an A-lift or T-lift procedure at the collar level of the deformity constructs, and all patients had available baseline and two years full length standing radiographs as well as patient reported outcomes measures. We included patients with an SVO greater than 50 millimeters, with lumbar lordosis less than 30 degrees, thoracic kyphosis greater than 60 degrees, pelvic tilt greater than 25 degrees, and a mismatch of greater than 10 degrees. We excluded patients with surgery for either infection, tumor, or trauma, who had a three-column osteotomy, or who had more than two rods used because we thought that this could bias the results. Other variables collected for this study included age, ASA grade, gender, smoking, diabetes, and the prevalence of osteopenia and osteoporosis. Other variables included extent of deformity correction achieved, length of stay, length of follow-up in months, readmission rates, rod fracture rates, as well as duration of time from surgery to rod fracture. Radiographic parameters, as stated above, you can see there. The patient reported questionnaires utilized included the SRS-22 questionnaire, as well as the Oswester Disability Index. Additional analysis performed included the T-test, the Mann-Whitney U-test, where appropriate, the Chi-squared test, and we considered significance, any value less than a threshold of 0.05. Combined, there were 198 patients in the study, both groups, 133 in the T-LIF cohort and 65 in the ALIF cohort, both groups were balanced with respect to gender, BMI, the prevalence of diabetes, history of smoking, current rates of smoking, as well as osteopenia. There were statistically significant differences in the patient age, as well as prevalence of osteoporosis, both of which, between both groups, the patients were slightly older in the T-LIF cohort, 57 versus 52 years old. However, we don't think that was significant and clinically relevant to bias the results, and the prevalence of osteoporosis was 25% in the T-LIF cohort, compared to 9% in the ALIF cohort. At baseline, radiographic parameters were balanced between both groups, the extent of sagittal plane malalignment, which can be measured by the SVA, the pelvic tilt, and the sacral slope, appeared to be balanced between both groups. The mismatch, the pelvic incidence minus lumbar lordosis, also appeared to be balanced, and the osteoporosis was not statistically significantly different at baseline. Postoperatively, the mean length of follow-up was longer for the ALIF cohort, 77 months versus 54 months. However, the rod fracture rates were not statistically significant, 20% in the T-LIF cohort, compared to 17% in the ALIF cohort. When we break it down by unilateral and bilateral rod fracture rates, the unilateral rod fracture rates were 9.7% in the T-LIF cohort, versus 12% in the ALIF cohort, and this was not statistically significant. And the bilateral rod fracture rates were 10.5% in the T-LIF cohort, versus 4.6% in the ALIF cohort, and this was not statistically significant. The rate of revision surgery was 10.52% in the T-LIF cohort, and 6% in the ALIF cohort. Again, not statistically significant. The extent of deformity correction, which you can see here, measured by all of these radiographic parameters, did not appear to be statistically significant. However, the mean lumbar lordosis achieved at two years was slightly higher in the ALIF cohort, and the mean pelvic incidence minus lumbar lordosis mismatch was lower in the ALIF cohort as well, both of which were statistically significantly different. These graphs reinforce what the table demonstrated previously. The percentage of patients with unilateral rod fractures was not statistically significant with a p-value of 0.62, and the percentage of patients with bilateral rod fractures, which we considered more consequential, although higher in the T-LIF cohort. This was not a statistically significant finding. 10.52% versus 4.6 over the p-value of 0.11. The duration of time from surgery to rod fracture, in the T-LIF cohort, we tended to have about anywhere from 30% to 42% of rod fractures occurring within the first three years, lower rod fracture rates within three to five years, and the rest of the rod fractures occurring after five years. In the unilateral rod fracture cohort, however, when stratified, when we look at the bilateral rod fractures, we could see a stepwise decrease in the duration of time from surgery to rod fractures, with the greatest rod fractures occurring within three years, and subsequently decreasing over time. This study, this table just demonstrates the change from baseline to baseline. In conclusion, both ALIF and T-LIF procedures are the caudal level of long spinal deformity constructs were associated with low bilateral rod fracture rates, with no difference in the rate of revision surgery between both groups. The prevalence of rod fractures was not statistically significantly different between the ALIFs and the T-LIF groups, and the extent of functional improvement in pain and disability appeared to be similar between both groups. So this study hopefully suggests that you should do what's best in your hands when correcting deformity constructs, if you're interested in supplementing the sacral pelvic fixation with anterior column support. Thank you for your time.

surgical techniques

rod fracture rates

patient outcomes

functional improvement

surgeons