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## Complication rates associated with open versus percutaneous pedicle screw instrumentation among patients undergoing minimally invasive interbody fusion for adult spinal deformity

### OBJECTIVE

High-quality studies that compare outcomes of open and minimally invasively placed pedicle screws for adult spinal deformity are needed. Therefore, the authors compared differences in complications from a circumferential minimally invasive spine (MIS) surgery and those from a hybrid surgery.

### METHODS

A retrospective review of a multicenter database of patients with spinal deformity who were treated with an MIS surgery was performed. Database inclusion criteria included an age of ≥ 18 years and at least 1 of the following: a coronal Cobb angle of > 20°, a sagittal vertical axis of > 5 cm, a pelvic incidence–lumbar lordosis angle of > 10°, and/or a pelvic tilt of > 20°. Patients were propensity matched according to the levels instrumented.

### RESULTS

In this database, a complete data set was available for 165 patients, and after those who underwent 3-column osteotomy were excluded, 137 patients were available for analysis; 76 patients remained after propensity matching (MIS surgery group 38 patients, hybrid surgery group 38 patients). The authors found no difference in demographics, number of levels instrumented, or preoperative and postoperative radiographic results. At least 1 complication was suffered by 55.3% of patients in the hybrid surgery group and 44.7% of those in the MIS surgery group (p = 0.359). Patients in the MIS surgery group had significantly fewer neurological, operative, and minor complications than those in the hybrid surgery group. The reoperation rates in both groups were similar. The most common complication category for the MIS surgery group was radiographic and for the hybrid surgery group was neurological. Patients in both groups experienced postoperative improvement in their Oswestry Disability Index and visual analog scale (VAS) back and leg pain scores (all p < 0.05); however, MIS surgery provided a greater reduction in leg pain according to VAS scores.

### CONCLUSIONS

Overall complication rates in the MIS and hybrid surgery groups were similar. MIS surgery resulted in significantly fewer neurological, operative, and minor complications. Reoperation rates in the 2 groups were similar, and despite complications, the patients reported significant improvement in their pain and function.

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## Impact of case type, length of stay, institution type, and comorbidities on Medicare diagnosis-related group reimbursement for adult spinal deformity surgery

### OBJECTIVE

The aim of this study was to educate medical professionals about potential financial impacts of improper diagnosis-related group (DRG) coding in adult spinal deformity (ASD) surgery.

### METHODS

Medicare’s Inpatient Prospective Payment System PC Pricer database was used to collect 2015 reimbursement data for ASD procedures from 12 hospitals. Case type, hospital type/location, number of operative levels, proper coding, length of stay, and complications/comorbidities (CCs) were analyzed for effects on reimbursement. DRGs were used to categorize cases into 3 types: 1) anterior or posterior only fusion, 2) anterior fusion with posterior percutaneous fixation with no dorsal fusion, and 3) combined anterior and posterior fixation and fusion.

### RESULTS

Pooling institutions, cases were reimbursed the same for single-level and multilevel ASD surgery. Longer stay, from 3 to 8 days, resulted in an additional $1400 per stay. Posterior fusion was an additional$6588, while CCs increased reimbursement by approximately $13,000. Academic institutions received higher reimbursement than private institutions, i.e., approximately$14,000 (Case Types 1 and 2) and approximately $16,000 (Case Type 3). Urban institutions received higher reimbursement than suburban institutions, i.e., approximately$3000 (Case Types 1 and 2) and approximately $3500 (Case Type 3). Longer stay, from 3 to 8 days, increased reimbursement between$208 and $494 for private institutions and between$1397 and \$1879 for academic institutions per stay.

### CONCLUSIONS

Reimbursement is based on many factors not controlled by surgeons or hospitals, but proper DRG coding can significantly impact the financial health of hospitals and availability of quality patient care.

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## Mini-open anterior lumbar interbody fusion

In deformity surgery, anterior lumbar interbody fusion provides excellent biomechanical support, creates a broad surface area for arthrodesis, and induces lordosis in the lower lumbar spine. Preoperative MRI, plain radiographs, and, when available, CT scan should be carefully assessed for sacral slope as it relates to pubic symphysis, position of the great vessels (especially at L4/5), disc space height, or contraindication to an anterior approach. This video demonstrates the steps in an anterior surgical procedure with minimal open exposure.

The video can be found here: https://youtu.be/r3bC4_vu1hQ.

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## Comparison of radiographic results after minimally invasive, hybrid, and open surgery for adult spinal deformity: a multicenter study of 184 patients

### Object

Various surgical approaches, including open, minimally invasive, and hybrid techniques, have gained momentum in the management of adult spinal deformity. However, few data exist on the radiographic outcomes of different surgical techniques. The objective of this study was to compare the radiographic and clinical outcomes of the surgical techniques used in the treatment of adult spinal deformity.

### Methods

The authors conducted a retrospective review of two adult spinal deformity patient databases, a prospective open surgery database and a retrospective minimally invasive surgery (MIS) and hybrid surgery database. The time frame of enrollment in this study was from 2007 to 2012. Spinal deformity patients were stratified into 3 surgery groups: MIS, hybrid surgery, and open surgery. The following pre- and postoperative radiographic parameters were assessed: lumbar major Cobb angle, lumbar lordosis, pelvic incidence minus lumbar lordosis (PI−LL), sagittal vertical axis, and pelvic tilt. Scores on the Oswestry Disability Index (ODI) and a visual analog scale (VAS) for both back and leg pain were also obtained from each patient.

### Results

Of the 234 patients with adult spinal deformity, 184 patients had pre- and postoperative radiographs and were thus included in the study (MIS, n = 42; hybrid, n = 33; open, n = 109). Patients were a mean of 61.7 years old and had a mean body mass index of 26.9 kg/m2. Regarding radiographic outcomes, the MIS group maintained a significantly smaller mean lumbar Cobb angle (13.1°) after surgery compared with the open group (20.4°, p = 0.002), while the hybrid group had a significantly larger lumbar curve correction (26.6°) compared with the MIS group (18.8°, p = 0.045). The mean change in the PI−LL was larger for the hybrid group (20.6°) compared with the open (10.2°, p = 0.023) and MIS groups (5.5°, p = 0.003). The mean sagittal vertical axis correction was greater for the open group (25 mm) compared with the MIS group (≤ 1 mm, p = 0.008). Patients in the open group had a significantly larger postoperative thoracic kyphosis (41.45°) compared with the MIS patients (33.5°, p = 0.005). There were no significant differences between groups in terms of pre- and postoperative mean ODI and VAS scores at the 1-year follow-up. However, patients in the MIS group had much lower estimated blood loss and transfusion rates compared with patients in the hybrid or open groups (p < 0.001). Operating room time was significantly longer with the hybrid group compared with the MIS and open groups (p < 0.001). Major complications occurred in 14% of patients in the MIS group, 14% in the hybrid group, and 45% in the open group (p = 0.032).

### Conclusions

This study provides valuable baseline characteristics of radiographic parameters among 3 different surgical techniques used in the treatment of adult spinal deformity. Each technique has advantages, but much like any surgical technique, the positive and negative elements must be considered when tailoring a treatment to a patient. Minimally invasive surgical techniques can result in clinical outcomes at 1 year comparable to those obtained from hybrid and open surgical techniques.

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## Complications in adult spinal deformity surgery: an analysis of minimally invasive, hybrid, and open surgical techniques

### Object

It is hypothesized that minimally invasive surgical techniques lead to fewer complications than open surgery for adult spinal deformity (ASD). The goal of this study was to analyze matched patient cohorts in an attempt to isolate the impact of approach on adverse events.

### Methods

Two multicenter databases queried for patients with ASD treated via surgery and at least 1 year of follow-up revealed 280 patients who had undergone minimally invasive surgery (MIS) or a hybrid procedure (HYB; n = 85) or open surgery (OPEN; n = 195). These patients were divided into 3 separate groups based on the approach performed and were propensity matched for age, preoperative sagittal vertebral axis (SVA), number of levels fused posteriorly, and lumbar coronal Cobb angle (CCA) in an attempt to neutralize these patient variables and to make conclusions based on approach only. Inclusion criteria for both databases were similar, and inclusion criteria specific to this study consisted of an age > 45 years, CCA > 20°, 3 or more levels of fusion, and minimum of 1 year of follow-up. Patients in the OPEN group with a thoracic CCA > 75° were excluded to further ensure a more homogeneous patient population.

### Results

In all, 60 matched patients were available for analysis (MIS = 20, HYB = 20, OPEN = 20). Blood loss was less in the MIS group than in the HYB and OPEN groups, but a significant difference was only found between the MIS and the OPEN group (669 vs 2322 ml, p = 0.001). The MIS and HYB groups had more fused interbody levels (4.5 and 4.1, respectively) than the OPEN group (1.6, p < 0.001). The OPEN group had less operative time than either the MIS or HYB group, but it was only statistically different from the HYB group (367 vs 665 minutes, p < 0.001). There was no significant difference in the duration of hospital stay among the groups. In patients with complete data, the overall complication rate was 45.5% (25 of 55). There was no significant difference in the total complication rate among the MIS, HYB, and OPEN groups (30%, 47%, and 63%, respectively; p = 0.147). No intraoperative complications were reported for the MIS group, 5.3% for the HYB group, and 25% for the OPEN group (p < 0.03). At least one postoperative complication occurred in 30%, 47%, and 50% (p = 0.40) of the MIS, HYB, and OPEN groups, respectively. One major complication occurred in 30%, 47%, and 63% (p = 0.147) of the MIS, HYB, and OPEN groups, respectively. All patients had significant improvement in both the Oswestry Disability Index (ODI) and visual analog scale scores after surgery (p < 0.001), although the MIS group did not have significant improvement in leg pain. The occurrence of complications had no impact on the ODI.

### Conclusions

Results in this study suggest that the surgical approach may impact complications. The MIS group had significantly fewer intraoperative complications than did either the HYB or OPEN groups. If the goals of ASD surgery can be achieved, consideration should be given to less invasive techniques.

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## Less invasive surgery for treating adult spinal deformities: ceiling effects for deformity correction with 3 different techniques

### Object

Minimally invasive surgery (MIS) options for the treatment of adult spinal deformity (ASD) have advanced significantly over the past decade. However, a wide array of options have been described as being MIS or less invasive. In this study the authors investigated a multiinstitutional cohort of patients with ASD who were treated with less invasive methods to determine the extent of deformity correction achieved.

### Methods

This study was a retrospective review of multicenter prospectively collected data in 85 consecutive patients with ASD undergoing MIS surgery. Inclusion criteria were as follows: age older than 45 years; minimum 20° coronal lumbar Cobb angle; and 1 year of follow-up. Procedures were classified as follows: 1) stand-alone (n = 7); 2) circumferential MIS (n = 43); or 3) hybrid (n = 35).

### Results

An average of 4.2 discs (range 3–7) were fused, with a mean follow-up duration of 26.1 months in this study. For the stand-alone group the preoperative Cobb range was 22°–51°, with 57% greater than 30° and 28.6% greater than 50°. The mean Cobb angle improved from 35.7° to 30°. A ceiling effect of 23° for curve correction was observed, regardless of preoperative curve severity. For the circumferential MIS group the preoperative Cobb range was 19°–62°, with 44% greater than 30° and 5% greater than 50°. The mean Cobb angle improved from 32° to 12°. A ceiling effect of 34° for curve correction was observed. For the hybrid group the preoperative Cobb range was 23°–82°, with 74% greater than 30° and 23% greater than 50°. The mean Cobb angle improved from 43° to 15°. A ceiling effect of 55° for curve correction was observed.

### Conclusions

Specific procedures for treating ASD have particular limitations for scoliotic curve correction. Less invasive techniques were associated with a reduced ability to straighten the spine, particularly with advanced curves. These data can guide preoperative technique selection when treating patients with ASD.