Minimally invasive approaches for the correction of adult spinal deformity

The Lumbosacral Fractional Curve in Adult Degenerative Scoliosis

Spine surgeons are often faced with a profoundly difficult challenge in surgically treating adult degenerative scoliosis. Deformity correction surgery is complicated by the difficulty in offering extensive surgical corrections to the elderly, complication-prone population it commonly affects. As spine surgeons attempt to offer minimally invasive solutions to this disease process, the need for fusion of the fractional curve at L4, L5, and S1 may be discounted. A treatment strategy to identify, address, and treat the fractional curve with either open or minimally invasive techniques can lead to improved patient outcomes and decrease revision rates in this complicated pathologic process.

Supine and Dynamic Extension Radiographs as the Strongest Predictors of Post-operative Alignment in Minimally Invasive Lumbar Spine Surgery

STUDY DESIGN

Institutional review board-approved retrospective cohort study.

OBJECTIVES

Failure to achieve alignment goals may result in accelerated adjacent segment degeneration and poorer outcomes. In "open" spine surgery, intraoperative tools can fine tune alignment; minimally invasive spine surgery techniques may not allow for this type of intraoperative adjustment. The aim of this study was to identify pre-operative radiographic parameters that accurately predict post-operative alignment after minimally invasive lumbar spine surgery. We hypothesized that pre-operative supine and extension sagittal alignment would predict post-operative standing alignment.

METHODS

50 consecutive patients underwent lateral or anterior lumbar interbody fusion with or without percutaneous posterior instrumentation by a single-surgeon. Sagittal alignment parameters were evaluated on pre-operative standing scoliosis radiographs, dynamic radiographs, supine CT scout, and 6-week post-operative standing radiographs. Demographic and perioperative data were analyzed.

RESULTS

The mean age was 67.8 years. The mean BMI was 29.7. On average, 3 levels were instrumented (range, 2-6). Surgical time was 4.5 ± 1.8 hours. Following surgery, global lordosis increased from 44.7 ± 17° to 48.6 ± 16° (P = .001). However, there was no significant difference between the pre-operative supine (48.5 ± 15°), pre-operative extension (49.2 ± 18°), or 6-week post-operative standing radiographs (48.6 ± 16°). There were strong correlations between post-operative alignment and pre-operative supine (r = .825) and extension (r = .851) alignment.

CONCLUSIONS

Our results suggest that pre-operative supine and extension radiographs could be a gold standard for minimally invasive lumbar spine surgery alignment correction as they predict post-operative alignment. The extension alignment was the strongest predictor of post-operative alignment.

Management of severe adult spinal deformity with circumferential minimally invasive surgical strategies without posterior column osteotomies: a 13-year experience

OBJECTIVE

To evaluate the mid- to long-term clinical outcomes of circumferential minimally invasive surgery (CMIS) without posterior column osteotomies for severe adult spine deformity (ASD) correction.

METHODS

All patients with a minimum of 2-year follow-up undergoing staged CMIS correction of ASD from January 2007 to July 2018 were identified. All included patients had fusion of 3 or more interbody levels that spanned the L5-S1 junction. Only patients with severe deformity, Coronal Cobb > 50° or at least one SRS-Schwab ++ sagittal modifier (SVA > 95 mm, or PI-LL > 20, or PT > 30) were included. All complications were noted.

RESULT

136 patients met inclusion criteria; mean age of patients was 63.6 years (21-85, SD 13.7). The mean follow-up was 82.8 months (24-159, SD 36.6). The mean number of levels fused was 7 (3-16, SD 3). A total of 40 (29.4%) major complications were noted at final follow-ups: 2 (1.4%) intra-operative, 12 (8.9%) peri-operative (≤ 6 weeks from index), 26 (19.1%) post-operative (> 6 weeks from index). There was a total of 53 (40.0%) minor complications. Seven (5.1%) patients who developed radiographic proximal junctional kyphosis. Three patients (2.2%) developed proximal junctional failure. There were 8 (5.9%) cases of pseudarthrosis. Five of these occurred in patients undergoing AxiaLIF. All patients experienced improvements in patient-perceived outcomes (VAS, TIS, ODI, and SRS-22) and radiographic parameters at last follow-up when compared to pre-op (p < 0.05).

CONCLUSION

Rates of complications with CMIS correction of severe ASD are lower than published rates of complications seen with open ASD correction. Specifically, the incidence of catastrophic complications is lower. Furthermore, CMIS is associated with significant improvements in clinical and functional outcomes, low rates of pseudarthrosis and proximal junctional kyphosis. Therefore, in the appropriately selected patient, CMIS may be an excellent alternative approach to addressing severe ASD.

Minimally invasive scoliosis surgery for adolescent idiopathic scoliosis using posterior mini-open technique

The purpose of this study aimed to analyze and evaluate the radiologic and clinical outcomes of minimally invasive scoliosis surgery (MISS) for correcting adolescent idiopathic scoliosis (AIS) using the mini-open technique. Thirty-four AIS patients who underwent MISS using the mini-open technique for deformity correction. Using two to four 3-centimeter-long skin incisions (mini-open) and tubular retractors, we performed screw fixations, rod assembly, rod derotation maneuver (RD), and bone graft. For thoracoplasty, four to six ribs were resected using the same incisions. Correction was attempted using rod translation and RD maneuvers. Radiological outcomes and clinical outcomes (SRS-22) were evaluated. Mean preoperative Cobb's angle was 61.3° and curve flexibility (major curve) was 26.1%. This angle was corrected to 21.6° with a correction rate of 65.2% (P < 0.001). The coronal balance was not changed significantly. Sagittal vertical axes were corrected from -3.5 mm to 8.6 mm (-22 to 36.3 mm) (P = 0.009). Thoracic kyphosis angles and lumbar lordosis angles were not changed significantly but the values were within normal range. Each score of self-image in the SRS-22 questionnaire as well as the total score were improved significantly (P < 0.001). In conclusion, the MISS for correcting AIS using the mini-open technique showed comparable radiologic and clinical outcomes with fewer complications in patients with non-rigid scoliosis with Cobb's angle between 50° and 80°. Long-term results of this novel MISS using the mini-open technique could further strengthen the rationale for adopting this technique for curve correction in selected cases of AIS.

Safety and effectiveness of minimally invasive scoliosis surgery for adolescent idiopathic scoliosis: a retrospective case series of 84 patients

PURPOSE

The aim of this study was to retrospectively evaluate a prospective series of patients with adolescent idiopathic scoliosis (AIS) who were treated with minimally invasive scoliosis surgery (MISS) technique with a minimum follow-up more than 1 year.

MATERIALS AND METHODS

We retrospectively analyzed the prospectively collected data of 84 patients with AIS treated with MIS technique using two or three coin hole size incisions and a muscle-splitting approach. The clinical and radiological data such as the correction of deformity, coronal and sagittal profile and record of the perioperative morbidity of the patients were analyzed.

RESULTS

The mean primary Cobb angle was corrected from 59.8° preoperatively to 18.6° postoperatively with a mean correction of 68.9% (p < 0.001). The mean kyphosis at T2 to T12 was maintained within normal range with an increase from 31.2° preoperatively to 35.3° postoperatively (p < 0.001). The 30-day perioperative complication rate was 7.14% with one deep infection and five cases of hemothorax. The mean operation time was 312.8 min; mean estimated blood loss was 846.6 ml (range 420-2800); and mean length of stay was 8.5 days (range 5 to 14). All data of postoperative SRS-22 questionnaire were significantly improved (p < 0.001).

CONCLUSION

MISS used for AIS provides adequate correction in both planes and acceptable rate of perioperative complications, with a low estimated blood loss and short length of stay. Considering all the positives, the application of MISS technique for AIS seems meaningful and can become a valid alternative to posterior approach in the routine use. These slides can be retrieved under Electronic Supplementary Material.

Indirect Decompression Failure After Lateral Lumbar Interbody Fusion-Reported Failures and Predictive Factors: Systematic Review

BACKGROUND

In patients with symptomatic lumbar stenosis undergoing lateral transpsoas approach for lumbar interbody fusion (LLIF) surgery, it is not always clear when indirect decompression is sufficient in order to achieve symptom resolution. Indirect decompression failure (IDF), defined as "postoperative persistent symptoms of nerve compression with or without a second direct decompression surgery to reach adequate symptom resolution," is not widely reported. This information, however, is critical to better understand the indications, the potential, and the limitations of indirect decompression.

OBJECTIVE

The purpose of this study was to systematically review the current literature on IDF after LLIF.

METHODS

A literature search was performed on PubMed. We included randomized controlled trials and prospective, retrospective, case-control studies, and case reports. Information on sample size, demographics, procedure, number and location of involved levels, follow-up time, and complications were extracted.

RESULTS

After applying the exclusion criteria, we included 9 of the 268 screened articles that reported failure. A total of 632 patients were screened in these articles and detailed information was provided. Average follow-up time was 21 months. Overall reported incidence of IDF was 9%.

CONCLUSION

Failures of decompression via LLIF are inconsistently reported and the incidence is approximately 9%. IDF failure in LLIF may be underreported or misinterpreted as a complication. We propose to include the term "IDF" as described in this article to differentiate them from complications for future studies. A better understanding of why IDF occurs will allow surgeons to better plan surgical intervention and will avoid revision surgery.

Correction of adult spinal deformity with a minimally invasive fusionless bipolar construct: Preliminary results

INTRODUCTION

Fusion in adult spinal deformity has a high rate of complications. Fusionless constructs in children and percutaneous fixation in adults are now being used routinely. The aim of this study was to evaluate the preliminary results of a minimally invasive fusionless surgical technique used to correct adult spinal deformity.

MATERIALS AND METHODS

Thirty-eight patients with an average age of 45 years (15-76) with major spinal deformity requiring extensive arthrodesis from the upper thoracic region to the pelvis were operated consecutively and followed prospectively. Two hooks were implanted at the top and two iliosacral screws at the bottom. Two large rods connected by dominos to two small rods joined the upper hooks to the lower screws. The surgical data (operative time and bleeding), the radiological findings (Cobb angle, sagittal parameters, C7-plumbline AP and lateral), the complication rate and the morbidity were evaluated at the last follow-up visit.

RESULTS

The primary curvature was reduced by 40% from a mean of 58.5° (26-146) to 35.2° (3-109) (p<0.001). A clear decrease in operating time (270min) and blood loss (50cc/level) were observed. The length of hospitalization averaged 18 days (6-66), including an 8-15 day long preoperative traction period for 11 patients. We found 7 infectious complications, 11 early mechanical complications and one case of paraplegia due to severe kyphoscoliosis.

CONCLUSION

The corrections obtained are comparable to those reported in the literature for standard constructs. Most patients had an uneventful postoperative course. The early complications observed led us to very carefully select the indications. Long-term follow-up is essential.

Clinical and Radiologic Fate of the Lumbosacral Junction After Anterior Lumbar Interbody Fusion Versus Axial Lumbar Interbody Fusion at the Bottom of a Long Construct in CMIS Treatment of Adult Spinal Deformity

Introduction:

Surgeons use numerous arthrodesis strategies for fusion of the lumbosacral junction including anterior lumbar interbody fusion (ALIF) and axial lumbar interbody fusion (AxiaLIF). The optimal L5-S1 fusion strategy remains inconclusive. The purpose of this study is to compare the fate of the lumbosacral junction in ALIF versus AxiaLIF patients in terms of clinical and radiographic outcomes.

Methods:

Adult spinal deformity patients, treated with CMIS techniques, with at least 2-year follow-up who underwent AxiaLIF or ALIF at the lumbosacral junction were included. Patients were separated into two groups: AxiaLIF (56 patients) and ALIF (38 patients). Outcome measures included segmental lordosis, sagittal vertical alignment, lumbar lordosis (LL), pelvic incidence–LL mismatch, and pseudarthrosis, major complication, and revision surgery rates.

Results:

The ALIF group achieved greater postoperative and delta segmental lordosis, higher delta sagittal vertical alignment, higher delta LL, and lower postoperative pelvic incidence–LL mismatch. The pseudarthrosis, major complication, and revision surgery rates were higher in the AxiaLIF group. Five cases of pseudarthrosis at L5-S1 were seen, all in the AxiaLIF group.

Discussion and Conclusion:

ALIF patients showed more favorable radiographic correction parameters and lower rates of pseudarthrosis, major complications, and revision surgeries. ALIF is the preferred strategy for L5-S1 arthrodesis at a bottom of a long construct.

Minimally Invasive Spinal Surgery for Adult Spinal Deformity

The purpose of this review is to present the current techniques and outcomes of adult spine deformity (ASD) surgery using the minimally invasive spine surgery (MISS) approach. We performed a systemic search of PubMed for literature published through January 2018 with the following terms: "minimally invasive spine surgery," "adult spinal deformity," and "degenerative scoliosis." Of the 138 items that were found through this search, 57 English-language articles were selected for full-text review. According to the severity of the deformity and the symptoms, various types of MISS have been utilized, such as MISS decompression, circumferential MISS, and hybrid surgery. With proper indications, the MISS approach achieved satisfactory clinical and radiological outcomes for ASD, with reduced complication rates. Future studies should aim to define clear indications for the application of various surgical options.

A Posterior Oblique Approach to the Lumbar Disk Spaces, Vertebral Bodies, and Lumbar Plexus: A Cadaveric Feasibility Study

STUDY DESIGN

A laboratory cadaveric study.

OBJECTIVE

We aimed to demonstrate the feasibility of a posterior oblique approach, sharing the same advantages as the transpsoas technique while minimizing the risk of lumbar plexus or psoas muscle injuries.

SUMMARY OF BACKGROUND DATA

The transpsoas approach for interbody fusion and corpectomy offers advantages over posterior and anterior approaches. However, possible risks include traumatization of the psoas muscle or lumbar plexus.

METHODS

All lumbar disk spaces and vertebral bodies were exposed by a posterior oblique approach from left and right on a human cadaveric specimen. The exposure obtained and a step-by-step documentation of the procedure is outlined in detail.

RESULTS

We were able to achieve wide exposure of all lumbar disk spaces and vertebral bodies above the L5/S1 disk space. Only the psoas muscle was retracted, and the lumbar plexus nerves were easily visualized and gently retracted. Sharp dissection was only required around the tip of the transverse processes.

CONCLUSIONS

A posterior oblique approach seems to be less invasive than the transpsoas approach. Exposure of the anterior column structures above the iliac crest is comparable. The oblique approach offers direct access to the lumbar plexus and the extraforaminal segments of the nerve roots.

Application of Gelatin Sponge Impregnated with a Mixture of 3 Drugs to Intraoperative Nerve Root Block Combined with Robot-Assisted Minimally Invasive Transforaminal Lumbar Interbody Fusion Surgery in the Treatment of Adult Degenerative Scoliosis: A Clinical Observation Including 96 Patients

OBJECTIVE

Application of nerve root block is mainly for diagnosis with less application in intraoperative treatment. The aim of this study was to observe clinical and imaging outcomes of application of gelatin sponge impregnated with a mixture of 3 drugs to intraoperative nerve root block combined with robot-assisted minimally invasive transforaminal lumbar interbody fusion surgery in to treat adult degenerative lumbar scoliosis.

METHODS

From January 2012 to November 2014, 108 patients with adult degenerative lumbar scoliosis were treated with robot-assisted minimally invasive transforaminal lumbar interbody fusion surgery combined with intraoperative gelatin sponge impregnated with a mixture of 3 drugs. Visual analog scale and Oswestry Disability Index scores were used to evaluate postoperative improvement of back and leg pain, and clinical effects were assessed according to the 36-Item Short-Form Health Survey. Imaging was obtained preoperatively, 1 week and 3 months postoperatively, and at the last follow-up. Fusion status, complications, and other outcomes were assessed.

RESULTS

Follow-up was complete for 96 patients. Visual analog scale scores of leg and back pain on postoperative days 1-7 were decreased compared with preoperatively. At 1 week postoperatively, 3 months postoperatively, and last follow-up, visual analog scale score, Oswestry Disability Index score, coronal Cobb angle, and coronal and sagittal deviated distance decreased significantly (P = 0.000) and lumbar lordosis angle increased (P = 0.000) compared with preoperatively. Improvement rate of Oswestry Disability Index was 81.8% ± 7.4. Fusion rate between vertebral bodies was 92.7%.

CONCLUSIONS

Application of gelatin sponge impregnated with 3 drugs combined with robot-assisted minimally invasive transforaminal lumbar interbody fusion for treatment of adult degenerative lumbar scoliosis is safe and feasible with advantages of good short-term analgesia effect, minimal invasiveness, short length of stay, and good long-term clinical outcomes.

Correction of severe spinopelvic mismatch: decreased blood loss with lateral hyperlordotic interbody grafts as compared with pedicle subtraction osteotomy

OBJECTIVE

Pedicle subtraction osteotomy (PSO) provides extensive correction in patients with fixed sagittal plane imbalance but is associated with high estimated blood loss (EBL). Anterior column realignment (ACR) with lateral graft placement and sectioning of the anterior longitudinal ligament allows restoration of lumbar lordosis (LL). The authors compare peri- and postoperative measures in 2 groups of patients undergoing correction of a sagittal plane imbalance, either through PSO or the use of lateral lumbar fusion and ACR with hyperlordotic (20°–30°) interbody cages, with stabilization through standard posterior instrumentation in all cases.

METHODS

The authors performed a retrospective chart review of cases involving a lumbar PSO or lateral lumbar interbody fusion and ACR (LLIF-ACR) between 2010 and 2015 at the authors’ institution. Patients who had a PSO in the setting of a preexisting fusion that spanned more than 4 levels were excluded. Demographic characteristics, spinopelvic parameters, EBL, operative time, and LOS were analyzed and compared between patients treated with PSO and those treated with LLIF-ACR.

RESULTS

The PSO group included 14 patients and the LLIF-ACR group included 13 patients. The mean follow-up was 13 months in the LLIF-ACR group and 26 months in the PSO group. The mean EBL was significantly lower in the LLIF-ACR group, measuring approximately 50% of the mean EBL in the PSO group (1466 vs 2910 ml, p < 0.01). Total LL correction was equivalent between the 2 groups (35° in the PSO group, 31° in the LLIF-ACR group, p > 0.05), as was the preoperative PI-LL mismatch (33° in each group, p > 0.05) and the postoperative PI-LL mismatch (< 1° in each group, p = 0.05). The fusion rate as assessed by the need for reoperation due to pseudarthrosis was lower in the LLIF-ACR group but not significantly so (3 revisions in the PSO group due to pseudarthrosis vs 0 in the LLIF-ACR group, p > 0.5). The total operative time and LOS were not significantly different in the 2 groups.

CONCLUSIONS

This is the first direct comparison of the LLIF-ACR technique with the PSO in adult spinal deformity correction. The study demonstrates that the LLIF-ACR provides equivalent deformity correction with significantly reduced blood loss in patients with a previously unfused spine compared with the PSO. This technique provides a powerful means to avoid PSO in selected patients who require spinal deformity correction.

The Influence of Lordotic cages on creating Sagittal Balance in the CMIS treatment of Adult Spinal Deformity

BACKGROUND

CMIS techniques are heavily dependent on placement of lateral interbody cages. Cages with an increased lordotic angle are being advocated to improve segmental lordosis and SVA. We assessed the segmental lordosis achieved with the individual cages. We further studied three variables and the effect each had on segmental lordosis: the lordosis angle of the cage, the position of the cage in the intervertebral space, and the level that it has been placed.

METHODS

This is a retrospective study of 66 consecutive patients who underwent lateral interbody fusion using lordotic cages as part of CMIS correction of scoliosis from June 2012 to January 2016. Standing radiographs at pre op and 6-week follow-up were reviewed to identify the position of the cage in the intervertebral space and the amount of segmental lordosis achieved.

RESULTS

A total of 224 cages were placed. The 6°, 10°, 12°, and 20° cages achieved a mean segmental lordosis of 9.00°, 13.09°, 13.23°, and 18.32°, respectively (P < .05). Additionally, cages placed in the anterior, middle, and posterior 3rd of the disk space produced 13.02°, 11.47°, and 8.23° of lordosis, respectively (P < .05). Stratifying by level, cages placed at T12-L1, L1-2, L2-3, L3-4, and L4-5 translated to mean segmental lordotic values of 8.43°, 10.02°, 11.38°, 12.91°, and 14.58°, respectively (P < .05).

CONCLUSIONS

The angle of the cage had an impact on segmental lordosis. Achieved segmental lordosis was notably more when the cage was placed in lower lumbar levels. Additionally, cages placed in the posterior 3rd of the intervertebral space had significantly worse segmental lordosis compared to those placed in the anterior or middle 3rd. Our study shows that an average delta change of 8.03° can be achieved with 12° cages and this when done at each subsequent level results in a progressive harmonious creation of lordosis. IRB approval was obtained for this study.

Comparison of a Newer Versus Older Protocol for Circumferential Minimally Invasive Surgical (CMIS) Correction of Adult Spinal Deformity (ASD)-Evolution Over a 10-Year Experience

STUDY DESIGN

Retrospective.

OBJECTIVES

Compare circumferential minimally invasive surgical (CMIS) correction outcomes of patients treated for adult spinal deformity (ASD) with a newer versus older protocol SUMMARY OF BACKGROUND DATA: CMIS techniques have become increasingly popular. Increasing experience and learning curve may help improve outcomes.

METHODS

A prospectively collected database was queried for all patients who underwent CMIS correction of ASD (Cobb angle >20° or sagittal vertical axis [SVA] >50 mm or pelvic incidence-lumbar lordosis mismatch >10) at 3+ levels. Those without a full-length radiograph or 2-year follow-up were excluded. Patients were compared based on treatment using our original or newer protocol.

RESULTS

The original protocol had 76 patients with an average age of 66.99 years (range 46-81, standard deviation [SD] 9.03), and the new protocol had 53 patients with average age of 65.85 years (range 48-85, SD 8.08). Preoperative and latest visual analog scale (VAS) scores in the original were 6.85 and 3.45 (p = .001) and in the new were 6.19 and 2.27 (p = .004). Delta-VAS scores were 3.27 and 4.27. The Oswestry disability index (ODI) reduced from 45.84 to 32.91 (p = .041) in the original and from 44.21 to 25.39 (p = .017) in the new. Average delta-ODIs were 22.25 and 24.01. Preoperative, latest, and delta-SF physical component scores for the original were 35.38, 42.42, and 10.06 and for the new, 30.89, 39.49, and 11.93. SF mental component scores were 50.96, 55.19, and 12.84 and 50.12, 52.99, and 8.85. The original and new protocols had latest Cobb angles of 11.54° and 11.12° (p = .789), delta-Cobb angles of 14.51° and 20.03° (p < .05), latest SVAs of 42.85 and 30.58 mm (p < .05) and latest PI-LL mismatch of 15.49 and 9.00 mm (p < .05). In the original and the new, the average preoperative SVAs that reliably achieved a postoperative SVA of 50 mm or less were 84 and 119 mm, respectively, and the maximum delta-SVAs were 89 and 120 mm. The new protocol had fewer surgical complications (p < .05).

CONCLUSION

Improvements in radiographic scores, functional outcomes, and limits of SVA correction and lower complication rates suggest that the new protocol may help improve outcomes. These findings may be a reflection of our 10-year experience and advances in the learning curve.

LEVEL OF EVIDENCE

Level IV.

Adult Degenerative Scoliosis

The treatment of adult degenerative scoliosis begins in the outpatient setting when evaluating a patient both radiographically. Assessing the flexibility of the deformity is essential in determining what techniques will be required to achieve the goals of correction. Ultimately the surgeon's comfort and experience and the patient's medical risk stratification determine the strategy needed to address either a focal pathology or ultimate deformity correction.

Thirty-Day Reoperation and Readmission Rates After Correction of Adult Spinal Deformity via Circumferential Minimally Invasive Surgery-Analysis of a 7-Year Experience

STUDY DESIGN

Single-center retrospective analysis of consecutive patients who have undergone circumferential minimally invasive surgery (cMIS) for correction of adult spinal deformity (ASD).

OBJECTIVES

To study the rates of reoperations and readmissions within the first 30 days following cMIS for correction of ASD.

BACKGROUND

Hospital readmission and reoperation rates have been emphasized as an important measure of quality and cost-effectiveness of care. However, there is little information about the readmission rates following cMIS correction of ASD.

METHODS

This is a retrospective cohort study of 214 consecutive patients with ASD who underwent correction using cMIS involving at least 2 levels. Major complications encountered during surgery or within 30 days following the index procedure that needed reoperation or readmission were recorded. The primary outcomes measured were early readmission, and early reoperation.

RESULTS

An average of 4 levels were fused. Nineteen complications were noted in the 30-day period following the index surgery, giving an early complication rate of 8.9%. Twelve of those complications occurred during the initial hospitalization and 7 complications occurred after the patient had been discharged home. Forty-seven percent of the complications occurred within the first 3 years of our experience, 37% in the next 2 years, and only 16% in the following 3 years. The 30-day readmission rate was 3.3%, which showed no statistically significant difference based on the number of levels fused.

CONCLUSIONS

Our study delivers significant evidence that efforts to reduce hospital readmissions for ASD patients should begin by concentrating on the postoperative complications. Although minimally invasive approaches will not eliminate all complications, they may have an effect on reducing the rate of major complications, most notably the rate of postoperative infection. This in turn can lead to a substantially lower readmission and reoperation rate as is reported in our study.

LEVEL OF EVIDENCE

Level IV, case series.

The Mini-Open Pedicle Subtraction Osteotomy for Flat-Back Syndrome and Kyphosis Correction: Operative Technique

Supplemental Digital Content is Available in the Text.

The evolution of image-guided lumbosacral spine surgery

Techniques and approaches of spinal fusion have considerably evolved since their first description in the early 1900s. The incorporation of pedicle screw constructs into lumbosacral spine surgery is among the most significant advances in the field, offering immediate stability and decreased rates of pseudarthrosis compared to previously described methods. However, early studies describing pedicle screw fixation and numerous studies thereafter have demonstrated clinically significant sequelae of inaccurate surgical fusion hardware placement. A number of image guidance systems have been developed to reduce morbidity from hardware malposition in increasingly complex spine surgeries. Advanced image guidance systems such as intraoperative stereotaxis improve the accuracy of pedicle screw placement using a variety of surgical approaches, however their clinical indications and clinical impact remain debated. Beginning with intraoperative fluoroscopy, this article describes the evolution of image guided lumbosacral spinal fusion, emphasizing two-dimensional (2D) and three-dimensional (3D) navigational methods.

Does minimally invasive transsacral fixation provide anterior column support in adult scoliosis?

BACKGROUND

Spinal fusion to the sacrum, especially in the setting of deformity and long constructs, is associated with high complication and pseudarthrosis rates. Transsacral discectomy, fusion, and fixation is a minimally invasive spine surgery technique that provides very rigid fixation. To date, this has been minimally studied in the setting of spinal deformity correction.

QUESTIONS/PURPOSES

We determined (1) the fusion rate of long-segment arthrodeses, (2) heath-related quality-of-life (HRQOL) outcomes (VAS pain score, Oswestry Disability Index [ODI], SF-36), and (3) the common complications and their frequency in adult patients with scoliosis undergoing transsacral fixation without supplemental pelvic fixation.

METHODS

Between April 2007 and May 2011, 92 patients had fusion of three or more segments extending to the sacrum for spinal deformity. Transsacral L5-S1 fusion without supplemental pelvic fixation was performed in 56 patients. Of these, 46 with complete data points and a minimum of 2 years of followup (mean, 48 months; range, 24-72 months; 18% of patients lost to followup) were included in this study. Nineteen of the 46 (41%) had fusions extending above the thoracolumbar junction, with one patient having fusion into the proximal thoracic spine (T3-S1). General indications for the use of transsacral fixation were situations where the fusion needed to be extended to the sacrum, such as spondylolisthesis, prior laminectomy, stenosis, oblique take-off, and disc degeneration at L5-S1. Contraindications included anatomic variations in the sacrum, vascular anomalies, prior intrapelvic surgery, and rectal fistulas or abscesses. Fusion rates were assessed by full-length radiographs and CT scanning. HRQOL data, including VAS pain score, ODI, and SF-36 scores, were assessed at all pre- and postoperative visits. Intraoperative and postoperative complications were noted.

RESULTS

Forty-one of 46 patients (89%) developed a solid fusion at L5-S1. There were significant improvements in all HRQOL parameters. Eight patients had complications related to the transsacral fusion, including five pseudarthroses and three superficial wound dehiscences. Three patients underwent revision surgery with iliac fixation. There were no bowel injuries, sacral hematomas, or sacral fractures.

CONCLUSIONS

Transsacral fixation/fusion may allow for safe lumbosacral fusion without iliac fixation in the setting of long-segment constructs in carefully selected patients. This study was retrospective and suffered from some loss to followup; future prospective trials are called for to compare this technique to other, more established approaches.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

The technological development of minimally invasive spine surgery

Minimally invasive spine surgery has its roots in the mid-twentieth century with a few surgeons and a few techniques, but it has now developed into a large field of progressive spinal surgery. A wide range of techniques are now called "minimally invasive," and case reports are submitted constantly with new "minimally invasive" approaches to spinal pathology. As minimally invasive spine surgery has become more mainstream over the past ten years, in this paper we discuss its history and development.

Limitations and ceiling effects with circumferential minimally invasive correction techniques for adult scoliosis: analysis of radiological outcomes over a 7-year experience

Object

Minimally invasive correction of adult scoliosis is a surgical method increasing in popularity. Limited data exist, however, as to how effective these methodologies are in achieving coronal plane and sagittal plane correction in addition to improving spinopelvic parameters. This study serves to quantify how much correction is possible with present circumferential minimally invasive surgical (cMIS) methods.

Methods

Ninety patients were selected from a database of 187 patients who underwent cMIS scoliosis correction. All patients had a Cobb angle greater than 15°, 3 or more levels fused, and availability of preoperative and postoperative 36-inch standing radiographs. The mean duration of follow-up was 37 months. Preoperative and postoperative Cobb angle, sagittal vertical axis (SVA), coronal balance, lumbar lordosis (LL), and pelvic incidence (PI) were measured. Scatter plots were performed comparing the pre- and postoperative radiological parameters to calculate ceiling effects for SVA correction, Cobb angle correction, and PI-LL mismatch correction.

Results

The mean preoperative SVA value was 60 mm (range 11.5–151 mm); the mean postoperative value was 31 mm (range 0–84 mm). The maximum SVA correction achieved with cMIS techniques in any of the cases was 89 mm. In terms of coronal Cobb angle, a mean correction of 61% was noted, with a mean preoperative value of 35.8° (range 15°–74.7°) and a mean postoperative value of 13.9° (range 0°–32.5°). A ceiling effect for Cobb angle correction was noted at 42°. The ability to correct the PI-LL mismatch to 10° was limited to cases in which the preoperative PI-LL mismatch was 38° or less.

Conclusions

Circumferential MIS techniques as currently used for the treatment of adult scoliosis have limitations in terms of their ability to achieve SVA correction and lumbar lordosis. When the preoperative SVA is greater than 100 mm and a substantial amount of lumbar lordosis is needed, as determined by spinopelvic parameter calculations, surgeons should consider osteotomies or other techniques that may achieve more lordosis.

Biomechanical analysis and design of a dynamic spinal fixator using topology optimization: a finite element analysis

Surgeons often use spinal fixators to manage spinal instability. Dynesys (DY) is a type of dynamic fixator that is designed to restore spinal stability and to provide flexibility. The aim of this study was to design a new spinal fixator using topology optimization [the topology design (TD) system]. Here, we constructed finite element (FE) models of degenerative disc disease, DY, and the TD system. A hybrid-controlled analysis was applied to each of the three FE models. The rod structure of the topology optimization was modelled at a 39 % reduced volume compared with the rigid rod. The TD system was similar to the DY system in terms of stiffness. In contrast, the TD system reduced the cranial adjacent disc stress and facet contact force at the adjacent level. The TD system also reduced pedicle screw stresses in flexion, extension, and lateral bending.

2013 Young Investigator Award winner: how safe is lateral lumbar interbody fusion for the surgeon? A prospective in vivo radiation exposure study

STUDY DESIGN

Prospective in vivo radiation exposure study.

OBJECTIVE

To assess surgeon exposure to ionizing radiation in the setting of lateral lumbar interbody fusion (LLIF).

SUMMARY OF BACKGROUND DATA

Minimally invasive spine surgery relies heavily on image guidance. Rapid popularization of minimally invasive spine surgery procedures, such as LLIF, is appropriately accompanied by concern regarding occupational radiation exposure related to intraoperative fluoroscopy.

METHODS

Optically stimulated luminescence technology dosimeters were used to record radiation exposure prospectively at 5 anatomic locations during 18 LLIF procedures: (1) eye, (2) thyroid, (3) chest, (4) axilla, and (5) gluteal region. Additionally, a ring dosimeter was worn during 13 of the LLIF cases.

RESULTS

Average fluoroscopy time was 88.7 ± 36.8 seconds and skin dose to the patient was 25.2 ± 21.1 mGy. The chest dosimeter protected by lead recorded the lowest readings per procedure (0.44 ± 0.49 mrem). The gluteal dosimeter recorded an average exposure of 2.31 ± 4.50 mrem and the dosimeter at the axilla recorded an average of 4.20 ± 7.76 mrem per procedure. Exposure to the thyroid and eye were 2.19 ± 2.07 mrem and 2.64 ± 2.76 mrem, respectively. With the exception of the gluteal region, dosimeter readings from all unprotected areas were significantly higher than those from the chest dosimeter (P < 0.0125). In the course of 13 procedures, 190 mrem of exposure to the hand was recorded by the ring dosimeters. More than 2700 LLIF procedures may be performed annually before occupational limits are exceeded.

CONCLUSION

Prolonged exposure to "low-level" radiation as an occupational risk remains a concern for medical personnel. Radiation exposures to unprotected, radiosensitive locations, such as the axilla or eye, are worrisome. However, following radiation safety guidelines, 2700 LLIF procedures can be performed per year before exceeding occupational dose limits. Adherence to radiation safety guidelines is necessary to avoid sequelae related to an invisible but potentially deadly risk of minimally invasive spine surgery procedures.