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Yoon Ha, Keishi Maruo, Linda Racine, William W. Schairer, Serena S. Hu, Vedat Deviren, Shane Burch, Bobby Tay, Dean Chou, Praveen V. Mummaneni, Christopher P. Ames, and Sigurd H. Berven

Object

Proximal junctional kyphosis (PJK) is a common and significant complication after corrective spinal deformity surgery. The object of this study was to compare—based on clinical outcomes, postoperative proximal junctional kyphosis rates, and prevalence of revision surgery—proximal thoracic (PT) and distal thoracic (DT) upper instrumented vertebra (UIV) in adults who underwent spine fusion to the sacrum for the treatment of spinal deformity.

Methods

In this retrospective study the authors evaluated clinical and radiographic data from consecutive adults (age > 21 years) with a deformity treated using long instrumented posterior spinal fusion to the sacrum in the period from 2007 to 2009. The PT group included patients in whom the UIV was between T-2 and T-5, whereas the DT group included patients in whom the UIV level was between T-9 and L-1. Perioperative surgical data were compared between the PT and DT groups. Additionally, segmental, regional, and global spinal alignments, as well as the sagittal Cobb angle at the proximal junction, were analyzed on preoperative, early postoperative, and final standing 36-in. radiographs. Patient-reported outcome measurements (visual analog scale, Scoliosis Research Society Patient Questionnaire-22, Oswestry Disability Index, and the 36-Item Short-Form Health Survey) were compared.

Results

Eighty-nine patients, 22 males and 67 females, had a minimum follow-up of 2 years, and thus were eligible for participation in this study. Sixty-seven patients were in the DT group and 22 were in the PT group. Operative time (p = 0.387) and estimated blood loss (p < 0.05) were slightly higher in the PT group. The overall rate of revision surgery was 48.0% and 54.5% in the DT and PT groups, respectively (p = 0.629). The prevalence of PJK according to radiological criteria was 34% in the DT group and 27% in the PT group (p = 0.609). The percent of patients with PJK that required surgical correction (surgical PJK) was 11.9% (8 of 67) in the DT group and 9.1% (2 of 22) in the PT group (p = 1.0). The onset of surgical PJK was significantly earlier than radiological PJK in the DT group (p < 0.01). The types of PJK were different in the PT and DT groups. Compression fracture at the UIV was more prevalent in the DT group, whereas subluxation was more prevalent in the PT group. Postoperatively, the PT group had less thoracic kyphosis (p = 0.02), less sagittal imbalance (p < 0.01), and less pelvic tilt (p = 0.04). In the DT group, early postoperative radiographs demonstrated that the proximal junctional angle of patients with surgical PJK was greater than in those without PJK and those with radiological PJK (p < 0.01). Clinical outcomes were significantly improved in both groups, and there was no significant difference between the groups.

Conclusions

Both PT and DT UIVs improve segmental and global sagittal plane alignment as well as patient-reported quality of life in those treated for adult spinal deformity. The prevalence of PJK was not different in the PT and DT groups. However, compression fracture was the mechanism more frequently observed with DT PJK, and subluxation was the mechanism more frequently observed in PT PJK. Strategies to avoid PJK may include vertebral augmentation to prevent fracture at the DT spine and mechanical means to prevent vertebral subluxation at the PT spine.

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Charles G. Fisher, Tony Goldschlager, Stefano Boriani, Peter Paul Varga, Laurence D. Rhines, Michael G. Fehlings, Alessandro Luzzati, Mark B. Dekutoski, Jeremy J. Reynolds, Dean Chou, Sigurd H. Berven, Richard P. Williams, Nasir A. Quraishi, Chetan Bettegowda, and Ziya L. Gokaslan

Object

The National Institutes of Health recommends strategies to obtain evidence for the treatment of rare conditions such as primary tumors of the spine (PTSs). These tumors have a low incidence and are pathologically heterogeneous, and treatment approaches are diverse. Appropriate evidence-based care is imperative. Failure to follow validated oncological principles may lead to unnecessary mortality and profound morbidity. This paper outlines a scientific model that provides significant evidence guiding the treatment of PTSs.

Methods

A four-stage approach was used: 1) planning: data from large-volume centers were reviewed to provide insight; 2) recruitment: centers were enrolled and provided the necessary infrastructure; 3) retrospective stage: existing medical records were reviewed and completed with survival data; and 4) prospective stage: prospective data collection has been implemented. The AOSpine Knowledge Forum Tumor designed six modules: demographic, clinical, diagnostic, therapeutic, local recurrence, survival, and perioperative morbidity data fields and provided funding.

Results

It took 18 months to implement Stages 1–3, while Stage 4 is ongoing. A total of 1495 tumor cases were captured and diagnosed as one of 18 PTS histotypes. In addition, a PTS biobank network has been created to link clinical data with tumor pathology and molecular analysis.

Conclusions

This scientific model has not only aggregated a large amount of PTS data, but has also established an international collaborative network of spine oncology centers. Access to large volumes of data will generate further research to guide and enhance PTS clinical management. This model could be applied to other rare neoplastic conditions. Clinical trial registration no.: NCT01643174 (ClinicalTrials.gov).

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Dominic Amara, Praveen V. Mummaneni, Christopher P. Ames, Bobby Tay, Vedat Deviren, Shane Burch, Sigurd H. Berven, and Dean Chou

OBJECTIVE

Many options exist for the surgical management of adult spinal deformity. Radiculopathy and lumbosacral pain from the fractional curve (FC), typically from L4 to S1, is frequently a reason for scoliosis patients to pursue surgical intervention. The purpose of this study was to evaluate the outcomes of limited fusion of the FC only versus treatment of the entire deformity with long fusions.

METHODS

All adult scoliosis patients treated at the authors’ institution in the period from 2006 to 2016 were retrospectively analyzed. Patients with FCs from L4 to S1 > 10° and radiculopathy ipsilateral to the concavity of the FC were eligible for study inclusion and had undergone three categories of surgery: 1) FC only (FC group), 2) lower thoracic to sacrum (LT group), or 3) upper thoracic to sacrum (UT group). Primary outcomes were the rates of revision surgery and complications. Secondary outcomes were estimated blood loss, length of hospital stay, and discharge destination. Spinopelvic parameters were measured, and patients were stratified accordingly.

RESULTS

Of the 99 patients eligible for inclusion in the study, 27 were in the FC group, 46 in the LT group, and 26 in the UT group. There were no significant preoperative differences in age, sex, smoking status, prior operation, FC magnitude, pelvic tilt (PT), sagittal vertical axis (SVA), coronal balance, pelvic incidence–lumbar lordosis (PI-LL) mismatch, or proportion of well-aligned spines (SVA < 5 cm, PI-LL mismatch < 10°, and PT < 20°) among the three treatment groups. Mean follow-up was 30 (range 12–112) months, with a minimum 1-year follow-up. The FC group had a lower medical complication rate (22% [FC] vs 57% [LT] vs 58% [UT], p = 0.009) but a higher rate of extension surgery (26% [FC] vs 13% [LT] vs 4% [UT], p = 0.068). The respective average estimated blood loss (592 vs 1950 vs 2634 ml, p < 0.001), length of hospital stay (5.5 vs 8.3 vs 8.3 days, p < 0.001), and rate of discharge to acute rehabilitation (30% vs 46% vs 85%, p < 0.001) were all lower for FC and highest for UT.

CONCLUSIONS

Treatment of the FC only is associated with a lower complication rate, shorter hospital stay, and less blood loss than complete scoliosis treatment. However, there is a higher associated rate of extension of the construct to the lower or upper thoracic levels, and patients should be counseled when considering their options.

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Michael M. Safaee, Alexander Tenorio, Joseph A. Osorio, Winward Choy, Dominic Amara, Lillian Lai, Annette M. Molinaro, Yalan Zhang, Serena S. Hu, Bobby Tay, Shane Burch, Sigurd H. Berven, Vedat Deviren, Sanjay S. Dhall, Dean Chou, Praveen V. Mummaneni, Charles M. Eichler, Christopher P. Ames, and Aaron J. Clark

OBJECTIVE

Anterior approaches to the lumbar spine provide wide exposure that facilitates placement of large grafts with high fusion rates. There are limited data on the effects of obesity on perioperative complications.

METHODS

Data from consecutive patients undergoing anterior lumbar interbody fusion (ALIF) from 2007 to 2016 at a single academic center were analyzed. The primary outcome was any perioperative complication. Complications were divided into those occurring intraoperatively and those occurring postoperatively. Multivariate logistic regression was used to assess the association of obesity and other variables with these complications. An estimation table was used to identify a body mass index (BMI) threshold associated with increased risk of postoperative complication.

RESULTS

A total of 938 patients were identified, and the mean age was 57 years; 511 were females (54.5%). The mean BMI was 28.7 kg/m2, with 354 (37.7%) patients classified as obese (BMI ≥ 30 kg/m2). Forty patients (4.3%) underwent a lateral transthoracic approach, while the remaining 898 (95.7%) underwent a transabdominal retroperitoneal approach. Among patients undergoing transabdominal retroperitoneal ALIF, complication rates were higher for obese patients than for nonobese patients (37.0% vs 28.7%, p = 0.010), a difference that was driven primarily by postoperative complications (36.1% vs 26.0%, p = 0.001) rather than intraoperative complications (3.2% vs 4.3%, p = 0.416). Obese patients had higher rates of ileus (11.7% vs 7.2%, p = 0.020), wound complications (11.4% vs 3.4%, p < 0.001), and urinary tract infections (UTI) (5.0% vs 2.5%, p = 0.049). In a multivariate model, age, obesity, and number of ALIF levels fused were associated with an increased risk of postoperative complication. An estimation table including 19 candidate cut-points, odds ratios, and adjusted p values found a BMI ≥ 31 kg/m2 to have the highest association with postoperative complication (p = 0.012).

CONCLUSIONS

Obesity is associated with increased postoperative complications in ALIF, including ileus, wound complications, and UTI. ALIF is a safe and effective procedure. However, patients with a BMI ≥ 31 kg/m2 should be counseled on their increased risks and warrant careful preoperative medical optimization and close monitoring in the postoperative setting.

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Ping-Guo Duan, Praveen V. Mummaneni, Joshua Rivera, Jeremy M. V. Guinn, Minghao Wang, Zhuo Xi, Bo Li, Hao-Hua Wu, Christopher P. Ames, Shane Burch, Sigurd H. Berven, and Dean Chou

OBJECTIVE

Patients undergoing long-segment fusions from the lower thoracic (LT) spine to the sacrum for adult spinal deformity (ASD) correction are at risk for proximal junctional kyphosis (PJK). One mechanism of PJK is fracture of the upper instrumented vertebra (UIV) or higher (UIV+1), which may be related to bone mineral density (BMD). Because Hounsfield units (HUs) on CT correlate with BMD, the authors evaluated whether HU values were correlated with PJK after long fusions for ASD.

METHODS

The authors performed a retrospective study of patients older than 50 years who had undergone ASD correction from the LT spine to the sacrum in the period from October 2007 to January 2018 and had a minimum 2-year follow-up. Demographic and spinopelvic parameters were measured. HU values were measured on preoperative CT at the UIV, UIV+1, and UIV+2 (2 levels above the UIV) levels and were assessed for correlations with PJK.

RESULTS

The records of 127 patients were reviewed. Fifty-four patients (19 males and 35 females) with a mean age of 64.91 years and mean follow-up of 3.19 years met the study inclusion criteria; there were 29 patients with PJK and 25 patients without. There was no statistically significant difference in demographics or follow-up between these two groups. Neither was there a difference between the groups with regard to postoperative pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), PI minus LL (PI-LL), thoracic kyphosis (TK), or sagittal vertical axis (SVA; all p > 0.05). Postoperative pelvic tilt (p = 0.003) and T1 pelvic angle (p = 0.014) were significantly higher in patients with PJK than in those without. Preoperative HUs at UIV, UIV+1, and UIV+2 were 120.41, 124.52, and 129.28 in the patients with PJK, respectively, and 152.80, 155.96, and 160.00 in the patients without PJK, respectively (p = 0.011, 0.02, and 0.018). Three receiver operating characteristic (ROC) curves for preoperative HU values at the UIV, UIV+1, and UIV+2 as a predictor for PJK were established, with areas under the ROC curve of 0.710 (95% CI 0.574–0.847), 0.679 (95% CI 0.536–0.821), and 0.681 (95% CI 0.539–0.824), respectively. The optimal HU value by Youden index was 104 HU at the UIV (sensitivity 0.840, specificity 0.517), 113 HU at the UIV+1 (sensitivity 0.720, specificity 0.517), and 110 HU at the UIV+2 (sensitivity 0.880, specificity 0.448).

CONCLUSIONS

In patients undergoing long-segment fusions from the LT spine to the sacrum for ASD, PJK was associated with lower HU values on CT at the UIV, UIV+1, and UIV+2. The measurement of HU values on preoperative CTs may be a useful adjunct for ASD surgery planning.

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Zhuo Xi, Praveen V. Mummaneni, Minghao Wang, Huibing Ruan, Shane Burch, Vedat Deviren, Aaron J. Clark, Sigurd H. Berven, and Dean Chou

OBJECTIVE

One vexing problem after lateral lumbar interbody fusion (LLIF) surgery is cage subsidence. Low bone mineral density (BMD) may contribute to subsidence, and BMD is correlated with Hounsfield units (HUs) on CT. The authors investigated if lower HU values correlated with subsidence after LLIF.

METHODS

A retrospective study of patients undergoing single-level LLIF with pedicle screw fixation for degenerative conditions at the University of California, San Francisco, by 6 spine surgeons was performed. Data on demographics, cage parameters, preoperative HUs on CT, and postoperative subsidence were collected. Thirty-six–inch standing radiographs were used to measure segmental lordosis, disc space height, and subsidence; data were collected immediately postoperatively and at 1 year. Subsidence was graded using a published grade of disc height loss: grade 0, 0%–24%; grade I, 25%–49%; grade II, 50%–74%; and grade III, 75%–100%. HU values were measured on preoperative CT from L1 to L5, and each lumbar vertebral body HU was measured 4 separate times.

RESULTS

After identifying 138 patients who underwent LLIF, 68 met the study inclusion criteria. All patients had single-level LLIF with pedicle screw fixation. The mean follow-up duration was 25.3 ± 10.4 months. There were 40 patients who had grade 0 subsidence, 15 grade I, 9 grade II, and 4 grade III. There were no significant differences in age, sex, BMI, or smoking. There were no significant differences in cage sizes, cage lordosis, and preoperative disc height. The mean segmental HU (the average HU value of the two vertebrae above and below the LLIF) was 169.5 ± 45 for grade 0, 130.3 ± 56.2 for grade I, 100.7 ± 30.2 for grade II, and 119.9 ± 52.9 for grade III (p < 0.001). After using a receiver operating characteristic curve to establish separation criteria between mild and severe subsidence, the most appropriate threshold of HU value was 135.02 between mild and severe subsidence (sensitivity 60%, specificity 92.3%). After univariate and multivariate analysis, preoperative segmental HU value was an independent risk factor for severe cage subsidence (p = 0.017, OR 15.694, 95% CI 1.621–151.961).

CONCLUSIONS

Lower HU values on preoperative CT are associated with cage subsidence after LLIF. Measurement of preoperative HU values on CT may be useful when planning LLIF surgery.

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John F. Burke, Andrew K. Chan, Rory R. Mayer, Joseph H. Garcia, Brenton Pennicooke, Michael Mann, Sigurd H. Berven, Dean Chou, and Praveen V. Mummaneni

The clamshell thoracotomy is often used to access both hemithoraxes and the mediastinum simultaneously for cardiothoracic pathology, but this technique is rarely used for the excision of spinal tumors. We describe the use of a clamshell thoracotomy for en bloc excision of a 3-level upper thoracic chordoma in a 20-year-old patient. The lesion involved T2, T3, and T4, and it invaded both chest cavities and indented the mediastinum. After 2 biopsies to confirm the diagnosis, the patient underwent a posterior spinal fusion followed by bilateral clamshell thoracotomy for 3-level en bloc resection with simultaneous access to both chest cavities and the mediastinum. To demonstrate how the clamshell thoracotomy was used to facilitate the tumor resection, an operative video and illustrations are provided, which show in detail how the clamshell thoracotomy can be used to access both hemithoraxes and the mediastinum.

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Michael M. Safaee, Alexander Tenorio, Joseph A. Osorio, Winward Choy, Dominic Amara, Lillian Lai, Serena S. Hu, Bobby Tay, Shane Burch, Sigurd H. Berven, Vedat Deviren, Sanjay S. Dhall, Dean Chou, Praveen V. Mummaneni, Charles M. Eichler, Christopher P. Ames, and Aaron J. Clark

OBJECTIVE

Anterior lumbar interbody fusion (ALIF) is a powerful technique that provides wide access to the disc space and allows for large lordotic grafts. When used with posterior spinal fusion (PSF), the procedures are often staged within the same hospital admission. There are limited data on the perioperative risk profile of ALIF-first versus PSF-first circumferential fusions performed within the same hospital admission. In an effort to understand whether these procedures are associated with different perioperative complication profiles, the authors performed a retrospective review of their institutional experience in adult patients who had undergone circumferential lumbar fusions.

METHODS

The electronic medicals records of patients who had undergone ALIF and PSF on separate days within the same hospital admission at a single academic center were retrospectively analyzed. Patients carrying a diagnosis of tumor, infection, or traumatic fracture were excluded. Demographics, surgical characteristics, and perioperative complications were collected and assessed.

RESULTS

A total of 373 patients, 217 of them women (58.2%), met the inclusion criteria. The mean age of the study cohort was 60 years. Surgical indications were as follows: degenerative disease or spondylolisthesis, 171 (45.8%); adult deformity, 168 (45.0%); and pseudarthrosis, 34 (9.1%). The majority of patients underwent ALIF first (321 [86.1%]) with a mean time of 2.5 days between stages. The mean number of levels fused was 2.1 for ALIF and 6.8 for PSF. In a comparison of ALIF-first to PSF-first cases, there were no major differences in demographics or surgical characteristics. Rates of intraoperative complications including venous injury were not significantly different between the two groups. The rates of postoperative ileus (11.8% vs 5.8%, p = 0.194) and ALIF-related wound complications (9.0% vs 3.8%, p = 0.283) were slightly higher in the ALIF-first group, although the differences did not reach statistical significance. Rates of other perioperative complications were no different.

CONCLUSIONS

In patients undergoing staged circumferential fusion with ALIF and PSF, there was no statistically significant difference in the rate of perioperative complications when comparing ALIF-first to PSF-first surgeries.

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Ping-Guo Duan, Praveen V. Mummaneni, Minghao Wang, Andrew K. Chan, Bo Li, Rory Mayer, Sigurd H. Berven, and Dean Chou

OBJECTIVE

In this study, the authors’ aim was to investigate whether obesity affects surgery rates for adjacent-segment degeneration (ASD) after transforaminal lumbar interbody fusion (TLIF) for spondylolisthesis.

METHODS

Patients who underwent single-level TLIF for spondylolisthesis at the University of California, San Francisco, from 2006 to 2016 were retrospectively analyzed. Inclusion criteria were a minimum 2-year follow-up, single-level TLIF, and degenerative lumbar spondylolisthesis. Exclusion criteria were trauma, tumor, infection, multilevel fusions, non-TLIF fusions, or less than a 2-year follow-up. Patient demographic data were collected, and an analysis of spinopelvic parameters was performed. The patients were divided into two groups: mismatched, or pelvic incidence (PI) minus lumbar lordosis (LL) ≥ 10°; and balanced, or PI-LL < 10°. Within the two groups, the patients were further classified by BMI (< 30 and ≥ 30 kg/m2). Patients were then evaluated for surgery for ASD, matched by BMI and PI-LL parameters.

RESULTS

A total of 190 patients met inclusion criteria (72 males and 118 females, mean age 59.57 ± 12.39 years). The average follow-up was 40.21 ± 20.42 months (range 24–135 months). In total, 24 patients (12.63% of 190) underwent surgery for ASD. Within the entire cohort, 82 patients were in the mismatched group, and 108 patients were in the balanced group. Within the mismatched group, adjacent-segment surgeries occurred at the following rates: BMI < 30 kg/m2, 2.1% (1/48); and BMI ≥ 30 kg/m2, 17.6% (6/34). Significant differences were seen between patients with BMI ≥ 30 and BMI < 30 (p = 0.018). A receiver operating characteristic curve for BMI as a predictor for ASD was established, with an AUC of 0.69 (95% CI 0.49–0.90). The optimal BMI cutoff value determined by the Youden index is 29.95 (sensitivity 0.857; specificity 0.627). However, in the balanced PI-LL group (108/190 patients), there was no difference in surgery rates for ASD among the patients with different BMIs (p > 0.05).

CONCLUSIONS

In patients who have a PI-LL mismatch, obesity may be associated with an increased risk of surgery for ASD after TLIF, but in obese patients without PI-LL mismatch, this association was not observed.