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Andrew K. Chan, Erica F. Bisson, Mohamad Bydon, Steven D. Glassman, Kevin T. Foley, Eric A. Potts, Christopher I. Shaffrey, Mark E. Shaffrey, Domagoj Coric, John J. Knightly, Paul Park, Michael Y. Wang, Kai-Ming Fu, Jonathan R. Slotkin, Anthony L. Asher, Michael S. Virk, Panagiotis Kerezoudis, Mohammed Ali Alvi, Jian Guan, Regis W. Haid and Praveen V. Mummaneni

OBJECTIVE

The optimal minimally invasive surgery (MIS) approach for grade 1 lumbar spondylolisthesis is not clearly elucidated. In this study, the authors compared the 24-month patient-reported outcomes (PROs) after MIS transforaminal lumbar interbody fusion (TLIF) and MIS decompression for degenerative lumbar spondylolisthesis.

METHODS

A total of 608 patients from 12 high-enrolling sites participating in the Quality Outcomes Database (QOD) lumbar spondylolisthesis module underwent single-level surgery for degenerative grade 1 lumbar spondylolisthesis, of whom 143 underwent MIS (72 MIS TLIF [50.3%] and 71 MIS decompression [49.7%]). Surgeries were classified as MIS if there was utilization of percutaneous screw fixation and placement of a Wiltse plane MIS intervertebral body graft (MIS TLIF) or if there was a tubular decompression (MIS decompression). Parameters obtained at baseline through at least 24 months of follow-up were collected. PROs included the Oswestry Disability Index (ODI), numeric rating scale (NRS) for back pain, NRS for leg pain, EuroQol-5D (EQ-5D) questionnaire, and North American Spine Society (NASS) satisfaction questionnaire. Multivariate models were constructed to adjust for patient characteristics, surgical variables, and baseline PRO values.

RESULTS

The mean age of the MIS cohort was 67.1 ± 11.3 years (MIS TLIF 62.1 years vs MIS decompression 72.3 years) and consisted of 79 (55.2%) women (MIS TLIF 55.6% vs MIS decompression 54.9%). The proportion in each cohort reaching the 24-month follow-up did not differ significantly between the cohorts (MIS TLIF 83.3% and MIS decompression 84.5%, p = 0.85). MIS TLIF was associated with greater blood loss (mean 108.8 vs 33.0 ml, p < 0.001), longer operative time (mean 228.2 vs 101.8 minutes, p < 0.001), and longer length of hospitalization (mean 2.9 vs 0.7 days, p < 0.001). MIS TLIF was associated with a significantly lower reoperation rate (14.1% vs 1.4%, p = 0.004). Both cohorts demonstrated significant improvements in ODI, NRS back pain, NRS leg pain, and EQ-5D at 24 months (p < 0.001, all comparisons relative to baseline). In multivariate analyses, MIS TLIF—as opposed to MIS decompression alone—was associated with superior ODI change (β = −7.59, 95% CI −14.96 to −0.23; p = 0.04), NRS back pain change (β = −1.54, 95% CI −2.78 to −0.30; p = 0.02), and NASS satisfaction (OR 0.32, 95% CI 0.12–0.82; p = 0.02).

CONCLUSIONS

For symptomatic, single-level degenerative spondylolisthesis, MIS TLIF was associated with a lower reoperation rate and superior outcomes for disability, back pain, and patient satisfaction compared with posterior MIS decompression alone. This finding may aid surgical decision-making when considering MIS for degenerative lumbar spondylolisthesis.

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Praveen V. Mummaneni, Mohamad Bydon, Mohammed Ali Alvi, Andrew K. Chan, Steven D. Glassman, Kevin T. Foley, Eric A. Potts, Christopher I. Shaffrey, Mark E. Shaffrey, Domagoj Coric, John J. Knightly, Paul Park, Michael Y. Wang, Kai-Ming Fu, Jonathan R. Slotkin, Anthony L. Asher, Michael S. Virk, Panagiotis Kerezoudis, Jian Guan, Regis W. Haid and Erica F. Bisson

OBJECTIVE

Since the enactment of the Affordable Care Act in 2010, providers and hospitals have increasingly prioritized patient-centered outcomes such as patient satisfaction in an effort to adapt the “value”-based healthcare model. In the current study, the authors queried a prospectively maintained multiinstitutional spine registry to construct a predictive model for long-term patient satisfaction among patients undergoing surgery for Meyerding grade I lumbar spondylolisthesis.

METHODS

The authors queried the Quality Outcomes Database for patients undergoing surgery for grade I lumbar spondylolisthesis between July 1, 2014, and June 30, 2016. The primary outcome of interest for the current study was patient satisfaction as measured by the North American Spine Surgery patient satisfaction index, which is measured on a scale of 1–4, with 1 indicating most satisfied and 4 indicating least satisfied. In order to identify predictors of higher satisfaction, the authors fitted a multivariable proportional odds logistic regression model for ≥ 2 years of patient satisfaction after adjusting for an array of clinical and patient-specific factors. The absolute importance of each covariate in the model was computed using an importance metric defined as Wald chi-square penalized by the predictor degrees of freedom.

RESULTS

A total of 502 patients, out of a cohort of 608 patients (82.5%) with grade I lumbar spondylolisthesis, undergoing either 1- or 2-level decompression (22.5%, n = 113) or 1-level decompression and fusion (77.5%, n = 389), met the inclusion criteria; of these, 82.1% (n = 412) were satisfied after 2 years. On univariate analysis, satisfied patients were more likely to be employed and working (41.7%, n = 172, vs 24.4%, n = 22; overall p = 0.001), more likely to present with predominant leg pain (23.1%, n = 95, vs 11.1%, n = 10; overall p = 0.02) but more likely to present with lower Numeric Rating Scale score for leg pain (median and IQR score: 7 [5–9] vs 8 [6–9]; p = 0.05). Multivariable proportional odds logistic regression revealed that older age (OR 1.57, 95% CI 1.09–2.76; p = 0.009), preoperative active employment (OR 2.06, 95% CI 1.27–3.67; p = 0.015), and fusion surgery (OR 2.3, 95% CI 1.30–4.06; p = 0.002) were the most important predictors of achieving satisfaction with surgical outcome.

CONCLUSIONS

Current findings from a large multiinstitutional study indicate that most patients undergoing surgery for grade I lumbar spondylolisthesis achieved long-term satisfaction. Moreover, the authors found that older age, preoperative active employment, and fusion surgery are associated with higher odds of achieving satisfaction.

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Paul Park, Kai-Ming Fu, Robert K. Eastlack, Stacie Tran, Gregory M. Mundis Jr., Juan S. Uribe, Michael Y. Wang, Khoi D. Than, David O. Okonkwo, Adam S. Kanter, Pierce D. Nunley, Neel Anand, Richard G. Fessler, Dean Chou, Mark E. Oppenlander, Praveen V. Mummaneni and the International Spine Study Group

OBJECTIVE

It is now well accepted that spinopelvic parameters are correlated with clinical outcomes in adult spinal deformity (ASD). The purpose of this study was to determine whether obtaining optimal spinopelvic alignment was absolutely necessary to achieve a minimum clinically important difference (MCID) or substantial clinical benefit (SCB).

METHODS

A multicenter retrospective review of patients who underwent less-invasive surgery for ASD was conducted. Inclusion criteria were age ≥ 18 years and one of the following: coronal Cobb angle > 20°, sagittal vertical axis (SVA) > 5 cm, pelvic tilt (PT) > 20°, or pelvic incidence to lumbar lordosis (PI-LL) mismatch > 10°. A total of 223 patients who were treated with circumferential minimally invasive surgery or hybrid surgery and had a minimum 2-year follow-up were identified. Based on optimal spinopelvic parameters (PI-LL mismatch ± 10° and SVA < 5 cm), patients were divided into aligned (AL) or malaligned (MAL) groups. The primary clinical outcome studied was the Oswestry Disability Index (ODI) score.

RESULTS

There were 74 patients in the AL group and 149 patients in the MAL group. Age and body mass index were similar between groups. Although the baseline SVA was similar, PI-LL mismatch (9.9° vs 17.7°, p = 0.002) and PT (19° vs 24.7°, p = 0.001) significantly differed between AL and MAL groups, respectively. As expected postoperatively, the AL and MAL groups differed significantly in PI-LL mismatch (−0.9° vs 13.1°, p < 0.001), PT (14° vs 25.5°, p = 0.001), and SVA (11.8 mm vs 48.3 mm, p < 0.001), respectively. Notably, there was no difference in the proportion of AL or MAL patients in whom an MCID (52.75% vs 61.1%, p > 0.05) or SCB (40.5% vs 46.3%, p > 0.05) was achieved for ODI score, respectively. Similarly, no differences in percentage of patients obtaining an MCID or SCB for visual analog scale back and leg pain score were observed. On multivariate analysis controlling for surgical and preoperative demographic differences, achieving optimal spinopelvic parameters was not associated with achieving an MCID (OR 0.645, 95% CI 0.31–1.33) or an SCB (OR 0.644, 95% CI 0.31–1.35) for ODI score.

CONCLUSIONS

Achieving optimal spinopelvic parameters was not a predictor for achieving an MCID or SCB. Since spinopelvic parameters are correlated with clinical outcomes, the authors’ findings suggest that the presently accepted optimal spinopelvic parameters may require modification. Other factors, such as improvement in neurological symptoms and/or segmental instability, also likely impacted the clinical outcomes.

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Andrew K. Chan, Erica F. Bisson, Mohamad Bydon, Steven D. Glassman, Kevin T. Foley, Eric A. Potts, Christopher I. Shaffrey, Mark E. Shaffrey, Domagoj Coric, John J. Knightly, Paul Park, Michael Y. Wang, Kai-Ming Fu, Jonathan R. Slotkin, Anthony L. Asher, Michael S. Virk, Panagiotis Kerezoudis, Silky Chotai, Anthony M. DiGiorgio, Regis W. Haid and Praveen V. Mummaneni

OBJECTIVE

The AANS launched the Quality Outcomes Database (QOD), a prospective longitudinal registry that includes demographic, clinical, and patient-reported outcome (PRO) data to measure the safety and quality of spine surgery. Registry data offer “real-world” insights into the utility of spinal fusion and decompression surgery for lumbar spondylolisthesis. Using the QOD, the authors compared the initial 12-month outcome data for patients undergoing fusion and those undergoing laminectomy alone for grade 1 degenerative lumbar spondylolisthesis.

METHODS

Data from 12 top enrolling sites were analyzed and 426 patients undergoing elective single-level spine surgery for degenerative grade 1 lumbar spondylolisthesis were found. Baseline, 3-month, and 12-month follow-up data were collected and compared, including baseline clinical characteristics, readmission rates, reoperation rates, and PROs. The PROs included Oswestry Disability Index (ODI), back and leg pain numeric rating scale (NRS) scores, and EuroQol–5 Dimensions health survey (EQ-5D) results.

RESULTS

A total of 342 (80.3%) patients underwent fusion, with the remaining 84 (19.7%) undergoing decompression alone. The fusion cohort was younger (60.7 vs 69.9 years, p < 0.001), had a higher mean body mass index (31.0 vs 28.4, p < 0.001), and had a greater proportion of patients with back pain as a major component of their initial presentation (88.0% vs 60.7%, p < 0.001). There were no differences in 12-month reoperation rate (4.4% vs 6.0%, p = 0.93) and 3-month readmission rates (3.5% vs 1.2%, p = 0.45). At 12 months, both cohorts improved significantly with regard to ODI, NRS back and leg pain, and EQ-5D (p < 0.001, all comparisons). In adjusted analysis, fusion procedures were associated with superior 12-month ODI (β −4.79, 95% CI −9.28 to −0.31; p = 0.04).

CONCLUSIONS

Surgery for grade 1 lumbar spondylolisthesis—regardless of treatment strategy—was associated with significant improvements in disability, back and leg pain, and quality of life at 12 months. When adjusting for covariates, fusion surgery was associated with superior ODI at 12 months. Although fusion procedures were associated with a lower rate of reoperation, there was no statistically significant difference at 12 months. Further study must be undertaken to assess the durability of either surgical strategy in longer-term follow-up.

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Paul Park, Kai-Ming Fu, Praveen V. Mummaneni, Juan S. Uribe, Michael Y. Wang, Stacie Tran, Adam S. Kanter, Pierce D. Nunley, David O. Okonkwo, Christopher I. Shaffrey, Gregory M. Mundis Jr., Dean Chou, Robert Eastlack, Neel Anand, Khoi D. Than, Joseph M. Zavatsky, Richard G. Fessler and the International Spine Study Group

OBJECTIVE

Achieving appropriate spinopelvic alignment in deformity surgery has been correlated with improvement in pain and disability. Minimally invasive surgery (MIS) techniques have been used to treat adult spinal deformity (ASD); however, there is concern for inadequate sagittal plane correction. Because age can influence the degree of sagittal correction required, the purpose of this study was to analyze whether obtaining optimal spinopelvic alignment is required in the elderly to obtain clinical improvement.

METHODS

A multicenter database of ASD patients was queried. Inclusion criteria were age ≥ 18 years; an MIS component as part of the index procedure; at least one of the following: pelvic tilt (PT) > 20°, sagittal vertical axis (SVA) > 50 mm, pelvic incidence to lumbar lordosis (PI-LL) mismatch > 10°, or coronal curve > 20°; and minimum follow-up of 2 years. Patients were stratified into younger (< 65 years) and older (≥ 65 years) cohorts. Within each cohort, patients were categorized into aligned (AL) or mal-aligned (MAL) subgroups based on postoperative radiographic measurements. Mal-alignment was defined as a PI-LL > 10° or SVA > 50 mm. Pre- and postoperative radiographic and clinical outcomes were compared.

RESULTS

Of the 185 patients, 107 were in the younger cohort and 78 in the older cohort. Based on postoperative radiographs, 36 (33.6%) of the younger patients were in the AL subgroup and 71 (66.4%) were in the MAL subgroup. The older patients were divided into 2 subgroups based on alignment; there were 26 (33.3%) patients in the AL and 52 (66.7%) in the MAL subgroups. Overall, patients within both younger and older cohorts significantly improved with regard to postoperative visual analog scale (VAS) scores for back and leg pain and Oswestry Disability Index (ODI) scores. In the younger cohort, there were no significant differences in postoperative VAS back and leg pain scores between the AL and MAL subgroups. However, the postoperative ODI score of 37.9 in the MAL subgroup was significantly worse than the ODI score of 28.5 in the AL subgroup (p = 0.019). In the older cohort, there were no significant differences in postoperative VAS back and leg pain score or ODI between the AL and MAL subgroups.

CONCLUSIONS

MIS techniques did not achieve optimal spinopelvic alignment in most cases. However, age appears to impact the degree of sagittal correction required. In older patients, optimal spinopelvic alignment thresholds did not need to be achieved to obtain similar symptomatic improvement. Conversely, in younger patients stricter adherence to optimal spinopelvic alignment thresholds may be needed.

https://thejns.org/doi/abs/10.3171/2018.4.SPINE171153

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Catherine A. Miller, Kai-Ming Fu and Praveen V. Mummaneni

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Anthony L. Asher, Panagiotis Kerezoudis, Praveen V. Mummaneni, Erica F. Bisson, Steven D. Glassman, Kevin T. Foley, Jonathan R. Slotkin, Eric A. Potts, Mark E. Shaffrey, Christopher I. Shaffrey, Domagoj Coric, John J. Knightly, Paul Park, Kai-Ming Fu, Clinton J. Devin, Kristin R. Archer, Silky Chotai, Andrew K. Chan, Michael S. Virk and Mohamad Bydon

OBJECTIVE

Patient-reported outcomes (PROs) play a pivotal role in defining the value of surgical interventions for spinal disease. The concept of minimum clinically important difference (MCID) is considered the new standard for determining the effectiveness of a given treatment and describing patient satisfaction in response to that treatment. The purpose of this study was to determine the MCID associated with surgical treatment for degenerative lumbar spondylolisthesis.

METHODS

The authors queried the Quality Outcomes Database registry from July 2014 through December 2015 for patients who underwent posterior lumbar surgery for grade I degenerative spondylolisthesis. Recorded PROs included scores on the Oswestry Disability Index (ODI), EQ-5D, and numeric rating scale (NRS) for leg pain (NRS-LP) and back pain (NRS-BP). Anchor-based (using the North American Spine Society satisfaction scale) and distribution-based (half a standard deviation, small Cohen’s effect size, standard error of measurement, and minimum detectable change [MDC]) methods were used to calculate the MCID for each PRO.

RESULTS

A total of 441 patients (80 who underwent laminectomies alone and 361 who underwent fusion procedures) from 11 participating sites were included in the analysis. The changes in functional outcome scores between baseline and the 1-year postoperative evaluation were as follows: 23.5 ± 17.4 points for ODI, 0.24 ± 0.23 for EQ-5D, 4.1 ± 3.5 for NRS-LP, and 3.7 ± 3.2 for NRS-BP. The different calculation methods generated a range of MCID values for each PRO: 3.3–26.5 points for ODI, 0.04–0.3 points for EQ-5D, 0.6–4.5 points for NRS-LP, and 0.5–4.2 points for NRS-BP. The MDC approach appeared to be the most appropriate for calculating MCID because it provided a threshold greater than the measurement error and was closest to the average change difference between the satisfied and not-satisfied patients. On subgroup analysis, the MCID thresholds for laminectomy-alone patients were comparable to those for the patients who underwent arthrodesis as well as for the entire cohort.

CONCLUSIONS

The MCID for PROs was highly variable depending on the calculation technique. The MDC seems to be a statistically and clinically sound method for defining the appropriate MCID value for patients with grade I degenerative lumbar spondylolisthesis. Based on this method, the MCID values are 14.3 points for ODI, 0.2 points for EQ-5D, 1.7 points for NRS-LP, and 1.6 points for NRS-BP.

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Andrew K. Chan, Erica F. Bisson, Mohamad Bydon, Steven D. Glassman, Kevin T. Foley, Eric A. Potts, Christopher I. Shaffrey, Mark E. Shaffrey, Domagoj Coric, John J. Knightly, Paul Park, Kai-Ming Fu, Jonathan R. Slotkin, Anthony L. Asher, Michael S. Virk, Panagiotis Kerezoudis, Silky Chotai, Anthony M. DiGiorgio, Alvin Y. Chan, Regis W. Haid and Praveen V. Mummaneni

OBJECTIVE

The American Association of Neurological Surgeons launched the Quality Outcomes Database (QOD), a prospective longitudinal registry that includes demographic, clinical, and patient-reported outcome (PRO) data, to measure the safety and quality of neurosurgical procedures, including spinal surgery. Differing results from recent randomized controlled trials have established a need to clarify the groups that would most benefit from surgery for degenerative lumbar spondylolisthesis. In the present study, the authors compared patients who were the most and the least satisfied following surgery for degenerative lumbar spondylolisthesis.

METHODS

This was a retrospective analysis of a prospective, national longitudinal registry including patients who had undergone surgery for grade 1 degenerative lumbar spondylolisthesis. The most and least satisfied patients were identified based on an answer of “1” and “4,” respectively, on the North American Spine Society (NASS) Satisfaction Questionnaire 12 months postoperatively. Baseline demographics, clinical variables, surgical parameters, and outcomes were collected. Patient-reported outcome measures, including the Numeric Rating Scale (NRS) for back pain, NRS for leg pain, Oswestry Disability Index (ODI), and EQ-5D (the EuroQol health survey), were administered at baseline and 3 and 12 months after treatment.

RESULTS

Four hundred seventy-seven patients underwent surgery for grade 1 degenerative lumbar spondylolisthesis in the period from July 2014 through December 2015. Two hundred fifty-five patients (53.5%) were the most satisfied and 26 (5.5%) were the least satisfied. Compared with the most satisfied patients, the least satisfied ones more often had coronary artery disease (CAD; 26.9% vs 12.2%, p = 0.04) and had higher body mass indices (32.9 ± 6.5 vs 30.0 ± 6.0 kg/m2, p = 0.02). In the multivariate analysis, female sex (OR 2.9, p = 0.02) was associated with the most satisfaction. Notably, the American Society of Anesthesiologists (ASA) class, smoking, psychiatric comorbidity, and employment status were not significantly associated with satisfaction. Although there were no significant differences at baseline, the most satisfied patients had significantly lower NRS back and leg pain and ODI scores and a greater EQ-5D score at 3 and 12 months postoperatively (p < 0.001 for all).

CONCLUSIONS

This study revealed that some patient factors differ between those who report the most and those who report the least satisfaction after surgery for degenerative lumbar spondylolisthesis. Patients reporting the least satisfaction tended to have CAD or were obese. Female sex was associated with the most satisfaction when adjusting for potential covariates. These findings highlight several key factors that could aid in setting expectations for outcomes following surgery for degenerative lumbar spondylolisthesis.

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Praveen V. Mummaneni, Erica F. Bisson, Panagiotis Kerezoudis, Steven Glassman, Kevin Foley, Jonathan R. Slotkin, Eric Potts, Mark Shaffrey, Christopher I. Shaffrey, Domagoj Coric, John Knightly, Paul Park, Kai-Ming Fu, Clinton J. Devin, Silky Chotai, Andrew K. Chan, Michael Virk, Anthony L. Asher and Mohamad Bydon

OBJECTIVE

Lumbar spondylolisthesis is a degenerative condition that can be surgically treated with either open or minimally invasive decompression and instrumented fusion. Minimally invasive surgery (MIS) approaches may shorten recovery, reduce blood loss, and minimize soft-tissue damage with resultant reduced postoperative pain and disability.

METHODS

The authors queried the national, multicenter Quality Outcomes Database (QOD) registry for patients undergoing posterior lumbar fusion between July 2014 and December 2015 for Grade I degenerative spondylolisthesis. The authors recorded baseline and 12-month patient-reported outcomes (PROs), including Oswestry Disability Index (ODI), EQ-5D, numeric rating scale (NRS)–back pain (NRS-BP), NRS–leg pain (NRS-LP), and satisfaction (North American Spine Society satisfaction questionnaire). Multivariable regression models were fitted for hospital length of stay (LOS), 12-month PROs, and 90-day return to work, after adjusting for an array of preoperative and surgical variables.

RESULTS

A total of 345 patients (open surgery, n = 254; MIS, n = 91) from 11 participating sites were identified in the QOD. The follow-up rate at 12 months was 84% (83.5% [open surgery]; 85% [MIS]). Overall, baseline patient demographics, comorbidities, and clinical characteristics were similarly distributed between the cohorts. Two hundred fifty seven patients underwent 1-level fusion (open surgery, n = 181; MIS, n = 76), and 88 patients underwent 2-level fusion (open surgery, n = 73; MIS, n = 15). Patients in both groups reported significant improvement in all primary outcomes (all p < 0.001). MIS was associated with a significantly lower mean intraoperative estimated blood loss and slightly longer operative times in both 1- and 2-level fusion subgroups. Although the LOS was shorter for MIS 1-level cases, this was not significantly different. No difference was detected with regard to the 12-month PROs between the 1-level MIS versus the 1-level open surgical groups. However, change in functional outcome scores for patients undergoing 2-level fusion was notably larger in the MIS cohort for ODI (−27 vs −16, p = 0.1), EQ-5D (0.27 vs 0.15, p = 0.08), and NRS-BP (−3.5 vs −2.7, p = 0.41); statistical significance was shown only for changes in NRS-LP scores (−4.9 vs −2.8, p = 0.02). On risk-adjusted analysis for 1-level fusion, open versus minimally invasive approach was not significant for 12-month PROs, LOS, and 90-day return to work.

CONCLUSIONS

Significant improvement was found in terms of all functional outcomes in patients undergoing open or MIS fusion for lumbar spondylolisthesis. No difference was detected between the 2 techniques for 1-level fusion in terms of patient-reported outcomes, LOS, and 90-day return to work. However, patients undergoing 2-level MIS fusion reported significantly better improvement in NRS-LP at 12 months than patients undergoing 2-level open surgery. Longer follow-up is needed to provide further insight into the comparative effectiveness of the 2 procedures.

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Khoi D. Than, Paul Park, Kai-Ming Fu, Stacie Nguyen, Michael Y. Wang, Dean Chou, Pierce D. Nunley, Neel Anand, Richard G. Fessler, Christopher I. Shaffrey, Shay Bess, Behrooz A. Akbarnia, Vedat Deviren, Juan S. Uribe, Frank La Marca, Adam S. Kanter, David O. Okonkwo, Gregory M. Mundis Jr., Praveen V. Mummaneni and the International Spine Study Group

OBJECTIVE

Minimally invasive surgery (MIS) techniques are increasingly used to treat adult spinal deformity. However, standard minimally invasive spinal deformity techniques have a more limited ability to restore sagittal balance and match the pelvic incidence–lumbar lordosis (PI-LL) than traditional open surgery. This study sought to compare “best” versus “worst” outcomes of MIS to identify variables that may predispose patients to postoperative success.

METHODS

A retrospective review of minimally invasive spinal deformity surgery cases was performed to identify parameters in the 20% of patients who had the greatest improvement in Oswestry Disability Index (ODI) scores versus those in the 20% of patients who had the least improvement in ODI scores at 2 years' follow-up.

RESULTS

One hundred four patients met the inclusion criteria, and the top 20% of patients in terms of ODI improvement at 2 years (best group, 22 patients) were compared with the bottom 20% (worst group, 21 patients). There were no statistically significant differences in age, body mass index, pre- and postoperative Cobb angles, pelvic tilt, pelvic incidence, levels fused, operating room time, and blood loss between the best and worst groups. However, the mean preoperative ODI score was significantly higher (worse disability) at baseline in the group that had the greatest improvement in ODI score (58.2 vs 39.7, p < 0.001). There was no difference in preoperative PI-LL mismatch (12.8° best vs 19.5° worst, p = 0.298). The best group had significantly less postoperative sagittal vertical axis (SVA; 3.4 vs 6.9 cm, p = 0.043) and postoperative PI-LL mismatch (10.4° vs 19.4°, p = 0.027) than the worst group. The best group also had better postoperative visual analog scale back and leg pain scores (p = 0.001 and p = 0.046, respectively).

CONCLUSIONS

The authors recommend that spinal deformity surgeons using MIS techniques focus on correcting a patient's PI-LL mismatch to within 10° and restoring SVA to < 5 cm. Restoration of these parameters seems to impact which patients will attain the greatest degree of improvement in ODI outcomes, while the spines of patients who do the worst are not appropriately corrected and may be fused into a fixed sagittal plane deformity.