Faculty Bibliography

INTRODUCTION: Wound infections following spinal surgery place a high toll on both the patient and the healthcare system. Although several large series studies have examined the incidence and distribution of spinal wound infection, the applicability of these studies varies greatly since nearly every study is either retrospective and/or lacks standard inclusion criteria for defining surgical site infection. To address this void, we present results from prospectively gathered thoracolumbar spine surgery data for which the Centers for Disease Control (CDC) criteria were stringently applied to define a surgical site infection (SSI). METHODS: A prospective randomized trial of 314 patients who underwent multilevel thoracolumbar spinal surgery with instrumentation followed by postoperative drain placement was completed (Takemoto et al., 2015). The trial consisted of two antibiotic arms: one for 24-hours, and the other for the duration of the drain; no differences were found between the arms. All infections meeting CDC criteria for SSI were included. RESULTS: A total of 40 infections met CDC criteria for SSI, for an overall incidence of 12.7%. Of these, 20 (50%) were culture-positive. The most common organism was Staphylococcus aureus (4 total: methicillin-sensitive=2; methicillin-resistant=2), followed by coagulase-negative Staphylococcus (3 cases), Propionibacterium acnes and Escherichia coli (2 cases each). Six infections grew multiple organisms, most commonly involving coagulase-negative staphylococcus and enterococcus. CONCLUSIONS: Our findings indicate that thoracolumbar SSI occurs at the higher end of the range cited in the literature (2-13%), which is largely based on retrospective data not subjected to the inclusivity of SSI as defined by the CDC. The three most common organisms in our analysis (S. aureus, P. acnes, E. coli) are consistent with previous reports. Staphylococcus aureus continues to be the most common causative organism and continued vigilance and searching for preventive measures need to be a high priority. This study provides Level I evidence.

STUDY DESIGN: A multicenter, prospective, consecutive database of surgical patients with adult spinal deformity (ASD). OBJECTIVE: This study investigated the use of antifibrinolytic (AF) therapy in ASD surgery. SUMMARY OF BACKGROUND DATA: AF therapy has been shown to be effective in preventing blood loss in some settings. Its effect on major and minor perioperative complications, blood product utilization, vascular events, and postoperative fusion in patients undergoing ASD surgery remains unclear. METHODS: All patients with data on AF use were included. Parameters of blood utilization included transfusion rates and units of packed red blood cells and fresh frozen plasma transfused. Thromboembolic events included stroke, deep vein thrombosis, and pulmonary embolus. Multivariate regression was used, accounting for confounders. RESULTS: Four hundred three patients were included. One hundred thirty-seven patients received aminocaproic acid (EACA), 81 received tranexamic acid (TXA), and 185 received no AFs. The use of AF was associated with a decrease in transfusion (EACA: odds ratio [OR] = 0.38, P = 0.043; TXA: OR = 0.31, P = 0.047), a decrease in the number of units of packed red blood cells transfused (EACA: incidence risk ratio [IRR] = 0.45, P = 0.0005; TXA: IRR = 0.7, P = 0.0005), and a decrease in the number of fresh frozen plasma transfused (EACA: IRR = 0.65, P = 0.003; TXA: IRR = 0.67, P = 0.006). AF use was associated with an increase in minor intraoperative complications (EACA: IRR = 2.15, P = 0.008; TXA: IRR = 2.12, P = 0.011). TXA use (but not EACA) was associated with a decrease in the incidence of major perioperative complications compared with no AF (IRR = 0.37, P = 0.019). There was no difference in the incidence of thromboembolic events. CONCLUSION: TXA or EACA use was associated with increased minor intraoperative complications. TXA was associated with decreased major perioperative complications. AF was associated with decreased utilization of blood products without an increased rate of thromboembolic events. Given the nature of this study, transfusion threshold was not standardized. Future studies with rigid criteria for transfusion should be prospectively performed to better evaluate the impact of AF during ASD surgery. LEVEL OF EVIDENCE: 3.

OBJECTIVE Sagittal malalignment requires higher energy expenditure to maintain an erect posture. Because the clinical impact of sagittal alignment is affected by both the severity of the deformity and recruitment of compensatory mechanisms, it is important to investigate new parameters that reflect both disability level and compensatory mechanisms for all patients. This study investigated the clinical relevance of the global sagittal axis (GSA), a novel measure to evaluate the standing axis of the human body. METHODS This is a retrospective review of patients who underwent full-body radiographs and completed health-related quality of life (HRQOL) questionnaires: Oswestry Disability Index (ODI), Scoliosis Research Society-22, EuroQol-5D (EQ-5D), and the visual analog scale for back and leg pain. The GSA was defined as the angle formed by a line from the midpoint of the femoral condyles to the center of C-7, and a line from the midpoint between the femoral condyles to the posterior superior corner of the S-1 sacral endplate. After evaluating the correlation of GSA/HRQOL with sagittal parameters, linear regression models were generated to investigate how ODI and GSA related to radiographic parameters (T-1 pelvic angle, pelvic retroversion, knee flexion, and pelvic posterior translation). RESULTS One hundred forty-three patients (mean age 44 years) were included. The GSA correlated significantly with all HRQOL (up to r = 0.6 with EQ-5D) and radiographic parameters (up to r = 0.962 with sagittal vertical axis). Regression between ODI and sagittal radiographic parameters identified the GSA as an independent predictor (r = 0.517, r2 = 0.267; p < 0.001). Analysis of standardized coefficients revealed that when controlling for deformity, the GSA increased with a concurrent decrease in pelvic retroversion (-0.837) and increases in knee flexion (+0.287) and pelvic posterior translation (+0.193). CONCLUSIONS The GSA is a simple, novel measure to assess the standing axis of the human body in the sagittal plane. The GSA correlated highly with spinopelvic and lower-extremities sagittal parameters and exhibited remarkable correlations with HRQOL, which exceeded other commonly used parameters.

STUDY DESIGN: Retrospective cohortObjective. To investigate the cervical alignment necessary for the maintenance of horizontal gaze depends on underlying thoracolumbar alignment SUMMARY OF BACKGROUND DATA.: Cervical curvature (CC) is affected by thoracic and global alignment. Recent studies suggest large variability in normative CC ranging from lordotic to kyphotic alignment. No previous studies have assessed the effect of global spinal alignment on CC in maintenance of horizontal gaze. METHODS: Patients without previous history of spinal surgery and were able to maintain their horizontal gaze while undergoing full body imaging were included. Patients were stratified based on thoracic kyphosis (TK) into (<30, 30-40, 40-50 and >50) then by SRS-Schwab sagittal vertical axis (SVA) modifier into (posterior alignment SVA<0, aligned 0-50 and malaligned >50 mm). Cervical alignment was assessed among SVA grade in TK groups. Stepwise linear regression analysis was applied on random selection of 60% of the population. A simplified formula was developed and validated on the remaining 40%. RESULTS: In each TK group (n = 118, 137, 125, 197), lower cervical curvature (C2-C7) was significantly more lordotic by increased Schwab SVA grade. T1 slope and cervical SVA significantly increased with increased thoracolumbar (C7-S1) SVA. Upper cervical curvature (C0-C2) and mismatch between T1 slope and cervical curvature (T1-CL) were similar. Regression analysis revealed LL minus TK (LL-TK) as an independent predictor (r = 0.640, r2 = 0.410) with formula: CC = 10 - (LL-TK)/2. Validation revealed that the absolute difference between the predicted CC and the actual CC was 8.5 degrees . Moreover, 64.2% of patients had their predicted C2-C7 values were within 10 degrees of the actual CC. CONCLUSIONS: Cervical kyphosis may represent normal alignment in a significant number of patients. However, in patients with SVA >50 and greater thoracic curvatures, cervical lordosis is needed to maintain the gaze. Cervical alignment can be predicted from underlying TK and lumbar lordosis, which may be clinically relevant when considering correction for thoracolumbar or cervical deformityLevel of Evidence: 3.