Quantitative Assessment of the Anatomical Footprint of the C1 Pedicle Relative to the Lateral Mass: A Guide for C1 Lateral Mass Fixation.

STUDY DESIGN: Anatomic study. OBJECTIVES: To determine the relationship of the anatomical footprint of the C1 pedicle relative to the lateral mass (LM). METHODS: Anatomic measurements were made on fresh frozen human cadaveric C1 specimens: pedicle width/height, LM width/height (minimum/maximum), LM depth, distance between LM's medial aspect and pedicle's medial border, distance between LM's lateral aspect to pedicle's lateral border, distance between pedicle's inferior aspect and LM's inferior border, distance between arch's midline and pedicle's medial border. The percentage of LM medial to the pedicle and the distance from the center of the LM to the pedicle's medial wall were calculated. RESULTS: A total of 42 LM were analyzed. The C1 pedicle's lateral aspect was nearly confluent with the LM's lateral border. Average pedicle width was 9.0 ± 1.1 mm, and average pedicle height was 5.0 ± 1.1 mm. Average LM width and depth were 17.0 ± 1.6 and 17.2 ± 1.6 mm, respectively. There was 6.9 ± 1.5 mm of bone medial to the medial C1 pedicle, which constituted 41% ± 9% of the LM's width. The distance from C1 arch's midline to the medial pedicle was 13.5 ± 2.0 mm. The LM's center was 1.6 ± 1 mm lateral to the medial pedicle wall. There was on average 3.5 ± 0.6 mm of the LM inferior to the pedicle inferior border. CONCLUSIONS: The center of the lateral mass is 1.6 ± 1 mm lateral to the medial wall of the C1 pedicle and approximately 15 mm from the midline. There is 6.9 ± 1.5 mm of bone medial to the medial C1 pedicle. Thus, the medial aspect of C1 pedicle may be used as an anatomic reference for locating the center of the C1 LM for screw fixation.

Impact of Fatigue on Maintenance of Upright Posture: Dynamic Assessment of Sagittal Spinal Deformity Parameters After Walking 10 Minutes.

STUDY DESIGN: Retrospective analysis of prospectively collected data. OBJECTIVE: To assess global and regional spinal sagittal radiographic parameters in adults with loss of lumbar lordosis ("flatback") before and after walking 10 minutes. SUMMARY OF BACKGROUND DATA: While routine activities of daily living may exacerbate functional disability of spinal sagittal-plane deformity, there is limited understanding of how sagittal parameters and compensatory mechanisms are affected by activity. METHODS: Consecutive adults with "flatback" at a single institution who previously had full-length standing spinal radiographs before and after walking 10 minutes were reviewed. Changes in spinal deformity sagittal parameters before and after walking were evaluated for two groups: Compensated Sagittal Deformity ("Compensated": sagittal vertical axis [SVA] ≤4 cm and pelvic tilt [PT] >20°) and Decompensated Sagittal Deformity ("Decompensated": SVA>4 cm and PT>20°). Intra-group radiographic comparisons were performed with paired Student t tests. RESULTS: One hundred fifty-seven patients (143 females, 14 males; average age 67.9 ±â€Š5.9 yr) met inclusion criteria. Initial average SVA was 1.7 ±â€Š1.2 cm for "Compensated" and 11.5 ±â€Š6.4 cm for "Decompensated." After walking 10 minutes, significant deteriorations in average SVA were observed for all "Decompensated" patients and 84.6% of "Compensated" patients. For both groups, this was accompanied by significant decreases in PT and LL and increases in PI-LL (P <0.01). Thoracic kyphosis increased after walking for only "Decompensated" (P <0.01). For "Compensated," the change in SVA was determined by decreases in PT and LL, while changes in SVA for "Decompensated" were correlated to worsening of all sagittal parameters. CONCLUSION: After walking, compensatory mechanisms to maintain sagittal balance in adults with spinal deformity are less pronounced than when the patient initially presents. This results in significant sagittal decompensation, irrespective of the initial SVA. As we postulate that loss of compensatory mechanisms is due to fatigue on pelvic and spinal extensor muscles, sagittal parameters can be re-evaluated with radiographs obtained after patients walk 10 minutes to unmask a hidden sagittal imbalance in compensated deformities. LEVEL OF EVIDENCE: 3.

Costs and readmission rates for the resection of primary and metastatic spinal tumors: a comparative analysis of 181 patients.

OBJECTIVE Because the surgical strategies for primary and metastatic spinal tumors are different, the respective associated costs and morbidities associated with those treatments likely vary. This study compares the direct costs and 90-day readmission rates between the resection of extradural metastatic and primary spinal tumors. The factors associated with cost and readmission are identified. METHODS Adults (age 18 years or older) who underwent the resection of spinal tumors between 2008 and 2013 were included in the study. Patients with intradural tumors were excluded. The direct costs of index hospitalization and 90-day readmission hospitalization were evaluated. The direct costs were compared between patients who were treated surgically for primary and metastatic spinal tumors. The independent factors associated with costs and readmissions were identified using multivariate analysis. RESULTS A total of 181 patients with spinal tumors were included (63 primary and 118 metastatic tumors). Overall, the mean index hospital admission cost for the surgical management of spinal tumors was $52,083. There was no significant difference in the cost of hospitalization between primary ($55,801) and metastatic ($50,098) tumors (p = 0.426). The independent factors associated with higher cost were male sex (p = 0.032), preoperative inability to ambulate (p = 0.002), having more than 3 comorbidities (p = 0.037), undergoing corpectomy (p = 0.021), instrumentation greater than 7 levels (p < 0.001), combined anterior-posterior approach (p < 0.001), presence of a perioperative complication (p < 0.001), and longer hospital stay (p < 0.001). The perioperative complication rate was 21.0%. Of this cohort, 11.6% of patients were readmitted within 90 days, and the mean hospitalization cost of that readmission was $20,078. Readmission rates after surgical treatment for primary and metastatic tumors were similar (11.1% vs 11.9%, respectively) (p = 0.880). Prior hospital stay greater than 15 days (OR 6.62, p = 0.016) and diagnosis of lung metastasis (OR 52.99, p = 0.007) were independent predictors of readmission. CONCLUSIONS Primary and metastatic spinal tumors are comparable with regard to the direct costs of the index surgical hospitalization and readmission rate within 90 days. The factors independently associated with costs are related to preoperative health status, type and complexity of surgery, and postoperative course.

Economic Impact of Revision Surgery for Proximal Junctional Failure After Adult Spinal Deformity Surgery: A Cost Analysis of 57 Operations in a 10-year Experience at a Major Deformity Center.

STUDY DESIGN: Retrospective cohort analysis. OBJECTIVE: To evaluate the economic impact of revision surgery for proximal junctional failures (PJF) after thoracolumbar fusions for adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA: PJF after fusions for ASD is a major cause of disability. Although clinical sequelae are described, PJF-revision operation costs are incompletely defined. METHODS: Consecutive adults who underwent thoracolumbar fusions for ASD (August, 2003 to January, 2013) were evaluated. Inclusion criteria include construct from pelvis to L2 or above and minimum 6 months follow-up after the index ASD operation. Direct costs (surgical supplies/implants, room/care, pharmacy, services) were identified from medical billing data and calculated for index ASD operations and subsequent surgeries for PJF. Not included in direct cost data were indirect costs, charges, surgeon fees, or revision operations for indications other than PJF (i.e., pseudarthrosis). Patients were compared based on the construct's upper-instrumented vertebra: upper thoracic (UT: T1-6) versus thoracolumbar junction (TLjxn: T9-L2). RESULTS: Of 501 patients, 382 met inclusion criteria. Fifty-one patients [UT:14; TLjxn: 40 at index; average follow-up 32.6 months (6-92 months)] had revisions for PJF, which summed to $3.2 million total direct cost. Average direct cost of index operations for the cohort ($68,294) was significantly greater than PJF-revisions ($55,547). Compared with TLjxn, UT had a significantly higher average cost for index operations ($79,860 vs. $65,868). However, PJF-revision cases were similar in average cost (UT:$60,103; TLjxn:$53,920; P = 0.09). Costs of PJF amounted to an additional 12.1% of the total index surgical cost in 382 patients. CONCLUSION: Revision operations for PJF after long thoracolumbar fusions for ASD are associated with an average direct cost of $55,547 per case. Revision costs for PJF are similar based on the index procedure's upper-instrumented vertebra level. At a major tertiary center over a 10-year period, PJF came at a very significant economic expense amounting to $3.2 million for 57 cases. LEVEL OF EVIDENCE: 3.

Local intrawound vancomycin powder decreases the risk of surgical site infections in complex adult deformity reconstruction: a cost analysis.

STUDY DESIGN: Retrospective cohort analysis. OBJECTIVE: To evaluate the rate of surgical site infections (SSIs) and cost-effectiveness of the use of intraoperative vancomycin powder in thoracolumbar adult deformity procedures. SUMMARY OF BACKGROUND DATA: The rates of SSI remain unacceptably high in adult spinal deformity surgery despite routine intravenous antibiotics. Vancomycin powder applied directly to the wound intraoperatively has shown promise for decreasing SSI in spine surgery. METHODS: Adults who underwent adult deformity reconstruction by 2 surgeons between 2008 and 2012 with a minimum of 3 months of clinical follow-up were retrospectively reviewed. The patients were subdivided into those who had received only routine perioperative intravenous antibiotics (control) and those who received intravenous antibiotics and 2 g of vancomycin powder applied into the surgical wound. The primary outcome was SSI within 90 days. Secondary outcomes included surgical/clinical parameters and SSI-related medical costs based on hospital billing records. RESULTS: Two hundred fifteen patients were evaluated-controls (n=64) and vancomycin powder group (n=151). The average number of levels fused was 10 (5-17, control) and 12 (5-19, vancomycin). The mean follow-up was 34 months (3-68 mo, control) and 18 months (3-35 mo, vancomycin) (P<0.05). There were significantly fewer hospital readmissions within 90 days for SSI in patients who received vancomycin powder (2.6%; 4/151) compared with controls (10.9%; 7/64) (P=0.01). There were no reported adverse events related to the intrawound vancomycin use. The average cost per patient of treating a postoperative SSI was higher in the control group ($34,388) than in the study group ($28,169). With the use of vancomycin powder, there was a cost saving of $244,402 per 100 complex spinal procedures. CONCLUSION: Local application of vancomycin powder significantly decreased SSI for adults undergoing spinal reconstructive surgery. This resulted in cost savings of $244,402 per 100 thoracolumbar adult deformity procedures. LEVEL OF EVIDENCE: 3.