David B. Cohen

Incidence of surgical site infection following adult spinal deformity surgery: an analysis of patient risk

Surgical site infection (SSI) following spinal surgery is a frequent complication and results in higher morbidity, mortality and healthcare costs. Patients undergoing surgery for spinal deformity (scoliosis/kyphosis) have longer surgeries, involving more spinal levels and larger blood losses than typical spinal procedures. Previous research has identified risk factors for SSI in spinal surgery, but few studies have looked at adult deformity surgeries. We retrospectively performed a large case cohort analysis of all adult patients who underwent surgery for kyphosis or scoliosis, between June 1996 and December 2005, by our adult spine division in an academic institution to asses the incidence and identify risk factors for SSI. We reviewed the electronic patient records of 830 adult patients. SSI was classified as deep or superficial to the fascia. 46 (5.5%) patients were found to have a SSI with 29 patients (3.5%) having deep infections. Obesity was found to be an independent risk factor for all SSI and superficial SSI (Pxa0=xa00.014 and Pxa0=xa00.013). As well, a history of prior SSI was also found to be a risk factor for SSI (Pxa0=xa00.041). Patient obesity and history of prior SSI lead to increased risk of infection. Since obesity was related to an increased risk of both superficial and deep SSI, counseling and treatment for obesity should be considered before elective deformity surgery.

A methodological systematic review on surgical site infections following spinal surgery: part 1: risk factors.

Study Design. A methodological systematic review. Objective. To critically appraise the validity of risk factors for surgical site infection (SSI) after spinal surgery. Summary of Background Data. SSIs lead to higher morbidity, mortality, and increased health care costs. Understanding which factors lead to an increased risk of SSI is important for the development of prophylactic protocols to counter this risk. To date, however, no review appraising the methodological quality of studies evaluating risk factors for spinal SSIs has been published. Methods. Contemporary studies identifying risk factors for SSI after spinal surgery were searched through the Medline and EMBASE databases (January 2001 to December 2010). References were retrieved and bias-prone study features were abstracted individually and independently by 2 authors. Results. Twenty-four eligible studies were identified, including 9 (nested) case-control studies and 15 case series. Included studies covered wide variations of indications and surgical procedures. A total of 73 different types of factors were evaluated for the risk of an SSI of which 34 (47%) were reported to be significantly related to at least 1 study. Only the following risk factors—diabetes mellitus, obesity, and previous SSI—were confirmed more often (n = 11, 8, and 3, respectively) as a significant risk factor for an SSI than they were disproved (n = 7, 6, and 1, respectively). Various sources of heterogeneity were observed, including patient selection, selection and analysis of putative risk factors, and definitions of SSI outcomes. Conclusion. There is an abundance of conflicting data on risk factors for SSI after spinal surgery. Given various sources of heterogeneity observed in observational literature, there is a paucity of solid evidence for the proof of robust risk factors. The authors recommend the introduction, validation, and use of a standardized set of strongly justified eligibility criteria and well-defined candidate risk factors and spinal SSI outcomes.

Decreased Erythrocyte Deformability After Transfusion and the Effects of Erythrocyte Storage Duration

BACKGROUND:Erythrocyte cell membranes undergo morphologic changes during storage, but it is unclear whether these changes are reversible. We assessed erythrocyte cell membrane deformability in patients before and after transfusion to determine the effects of storage duration and whether changes in deformability are reversible after transfusion. METHODS:Sixteen patients undergoing posterior spinal fusion surgery were studied. Erythrocyte deformability was compared between those who required moderate transfusion (≥5 units erythrocytes) and those who received minimal transfusion (0–4 units erythrocytes). Deformability was measured in samples drawn directly from the blood storage bags before transfusion and in samples drawn from patients before and after transfusion (over 3 postoperative days). In samples taken from the blood storage bags, we compared deformability of erythrocytes stored for a long duration (≥21 days), those stored for a shorter duration (<21 days), and cell-salvaged erythrocytes. Deformability was assessed quantitatively using the elongation index (EI) measured by ektacytometry, a method that determines the ability for the cell to elongate when exposed to shear stress. RESULTS:Erythrocyte deformability was significantly decreased from the preoperative baseline in patients after moderate transfusion (EI decreased by 12% ± 4% to 20% ± 6%; P = 0.03) but not after minimal transfusion (EI decreased by 3% ± 1% to 4% ± 1%; P = 0.68). These changes did not reverse over 3 postoperative days. Deformability was significantly less in erythrocytes stored for ≥21 days (EI = 0.28 ± 0.02) than in those stored for <21 days (EI = 0.33 ± 0.02; P = 0.001) or those drawn from patients preoperatively (EI = 0.33 ± 0.02; P = 0.001). Cell-salvaged erythrocytes had intermediate deformability (EI = 0.30 ± 0.03) that was greater than that of erythrocytes stored ≥21 days (P = 0.047), but less than that of erythrocytes stored <21 days (P = 0.03). CONCLUSIONS:The findings demonstrate that increased duration of erythrocyte storage is associated with decreased cell membrane deformability and that these changes are not readily reversible after transfusion.

The Presentation, Incidence, Etiology, and Treatment of Surgical Site Infections After Spinal Surgery

Study Design. Descriptive, retrospective cohort analysis. Objective. To evaluate the presentation, etiology, and treatment of surgical site infections (SSI) after spinal surgery. Summary of Background Data. SSI after spine surgery is frequently seen. Small case control studies have been published reporting the results of treatment options of SSI. We performed this study to indentify the most common clinical and laboratory presentation of a SSI, the most frequently seen infective organism, and evaluate the effectiveness of current treatment. Methods. All patients who underwent spinal surgery at our institution for diagnosis other than infection between June 1996 and December 2005 (N = 3174) were reviewed. All cases of SSI were identified. Patient and operative characteristics were reviewed. Infection type (deep or superficial), treatment course, laboratory and culture results were abstracted. Results. A total of 132 cases of SSI (84 deep and 48 superficial) were identified. About 72.7% of the SSI were detected as outpatients an average 28.7 days (deep, 29.9; superficial, 25.2) after the index procedure. Wound drainage was the most common complaint (68.2%). C-reactive protein level was elevated in 98.0%, erythrocyte sedimentation rate was elevated in 94.4%, but only 48.6% had elevated white blood cell count. Staphylococcus aureus was isolated in 72.6% of deep and 85.7% of superficial positive cultures. Seventy-six percent of deep SSI could be treated with a single debridement to clear the SSI. Instrumentation was retained or primarily exchanged if loose in all cases. Around 72.9% of superficial SSI were treated without formal debridement in the operating room. Antibiotic treatment was longer in deep SSI (40.8 vs. 19.6 days). Conclusion. Deep SSI following spinal surgery was effectively treated with single stage debridement and intravenous antibiotics. Superficial SSI could be treated effectively with local wound care and oral antibiotic therapy.

Impact of nonoperative treatment, vertebroplasty, and kyphoplasty on survival and morbidity after vertebral compression fracture in the medicare population.

BACKGROUNDnThe treatment of vertebral compression fractures with vertebral augmentation procedures is associated with acute pain relief and improved mobility, but direct comparisons of treatments are limited. Our goal was to compare the survival rates, complications, lengths of hospital stay, hospital charges, discharge locations, readmissions, and repeat procedures for Medicare patients with new vertebral compression fractures that had been acutely treated with vertebroplasty, kyphoplasty, or nonoperative modalities.nnnMETHODSnThe 2006 Medicare Provider Analysis and Review File database was used to identify 72,693 patients with a vertebral compression fracture. Patients with a previous vertebral compression fracture, those who had had a vertebral augmentation procedure in the previous year, those with a diagnosis of malignant neoplasm, and those who had died were excluded, leaving 68,752 patients. The patients were stratified into nonoperative treatment (55.6%), vertebroplasty (11.2%), and kyphoplasty (33.2%) cohorts. Survival rates were compared with use of Kaplan-Meier analysis and Cox regression. Results were adjusted for potential confounding variables. Secondary parameters of interest were analyzed with the chi-square test (categorical variables) and one-way analysis of variance (continuous variables), with the level of significance set at p < 0.05.nnnRESULTSnThe estimated three-year survival rates were 42.3%, 49.7%, and 59.9% for the nonoperative treatment, vertebroplasty, and kyphoplasty groups, respectively. The adjusted risk of death was 20.0% lower for the kyphoplasty group than for the vertebroplasty group (hazard ratio = 0.80, 95% confidence interval, 0.77 to 0.84). Patients in the kyphoplasty group had the shortest hospital stay and the highest hospital charges and were the least likely to have had pneumonia and decubitus ulcers during the index hospitalization and at six months postoperatively. However, kyphoplasty was more likely to result in a subsequent augmentation procedure than was vertebroplasty (9.41% compared with 7.89%; p < 0.001).nnnCONCLUSIONSnVertebral augmentation procedures appear to be associated with longer patient survival than nonoperative treatment does. Kyphoplasty tends to have a more striking association with survival than vertebroplasty does, but it is costly and may have a higher rate of subsequent vertebral compression fracture. These provocative findings may reflect selection bias and should be addressed in a prospective, direct comparison of methods to treat vertebral compression fractures.nnnLEVEL OF EVIDENCEnTherapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Influence of perioperative resuscitation status on postoperative spine surgery complications.

BACKGROUND CONTEXTnRestrictive transfusion criteria have led to decreased morbidity and mortality in critically ill patients. Their use has been extended to other patient groups. In adult spine surgery, ongoing postoperative blood losses and soft-tissue trauma may make these patients not appropriate for restrictive transfusion practices.nnnPURPOSEnThe purpose of this study was to assess the influence of postoperative hemoglobin (HGB) level and use of packed red blood cells (pRBC) or fresh frozen plasma on postoperative patient morbidity, mortality, and hospital length of stay (LOS).nnnSTUDY DESIGN/SETTINGnThis was a retrospective study in a high-volume tertiary hospital.nnnPATIENT SAMPLEnThe sample comprised 300 consecutive patients who underwent spinal surgeries with blood losses of more than 2 L.nnnOUTCOME MEASURESnThe outcome measures were postoperative patient morbidity, mortality, and LOS.nnnMETHODSnThe records of patients who underwent adult spinal surgeries with blood loss of 2 or more L (N=300) were abstracted for patient characteristics, operative characteristics, transfusion, and HGB level over time. Intensive care unit and hospital LOS, discharge location, death, pulmonary embolism, stroke, seizures, surgical site infections (SSI), and myocardial infarctions were noted. Logistic regression analyses (SAS software version 9.2) were used.nnnRESULTSnTwelve (3%) patients had a postoperative HGB level of less than 8 g/dL, 126 (41.3%) had 8 g/dL or more but less than 10 g/dL, and 167 (54.8%) had 10 g/dL or more. There was no significant difference in morbidity or mortality between the two groups with higher HGB levels. Multiple regression analysis revealed that patients with initial postoperative HGB level of less than 8 g/dL were six times more likely to develop SSI (odds ratio 6.37, 95% confidence interval 1.15-35.28). Deep SSI rates were increased with greater postoperative pRBC use (p=.002). Fresh frozen plasma use in the operation room was lower in cases that developed SSI (1.50 vs. 2.69, p=.042). Intensive care unit and ward LOS were longer with increased postoperative blood product use.nnnCONCLUSIONnPatients with high blood loss (more than 2 L) during spine surgery who are under-resuscitated (HGB level less than 8 g/dL) have a significant increased risk of SSI.

Surgical site infection after osteotomy of the adult spine: does type of osteotomy matter?

BACKGROUND CONTEXTnSurgical site infection after spinal surgery is frequently seen. It occurs between 0.7% and 12% of patients, leading to higher morbidity, mortality, and health-care costs. Osteotomy procedures are known to have increased blood losses and surgical times when compared with other spinal surgeries. Both of these factors have previously been identified as significant risk factors for SSI. We performed a cohort study of this high-risk population to identify risk factors and rates of SSI after spinal osteotomy surgery and identify difference in risk between different types of osteotomies.nnnPURPOSEnThe objective of the study was to assess the incidence and identify significant risk factors for surgical site infection (SSI) after spinal osteotomy.nnnSTUDY DESIGNnRetrospective review of all adult patients who underwent spinal osteotomy surgery for deformity by an orthopedic surgeon in our university.nnnMETHODSnAll electronic records of adult orthopedic patients whom underwent a spinal osteotomy procedure at our department between January 1998 and December 2005 (n=363) were abstracted. During surgery, a pedicle subtraction osteotomy (transpedicular wedge resection), anterior spine osteotomy (resection of anterior and middle columns), posterior Smith-Petersen osteotomy (resection of a portion of the superior and inferior lamina, ligamentum flavum, and the inferior and superior articular processed), or a combined anterior and posterior osteotomy (vertebral column resection [VCR]) (circumferential resection of the vertebrae via either a combined anterior/posterior or posterior-only approach) was performed. Primary outcome measurement was SSI. Subanalysis to deep and superficial SSI was performed.nnnRESULTSnTwenty patients (5.5%) were found to have an SSI, with nine (2.5%) having deep SSI. Analysis showed that patients undergoing VCR (p=.042) had a significant increased risk for deep SSI (11.1%). Obese patients had a significant increased risk (p=.045) for superficial SSI.nnnCONCLUSIONSnVertebral column resection has a significant increased risk for SSI (11.1%) compared with other types of osteotomies (4.1%). When possible, osteotomy techniques that involve less extensive exposures and soft-tissue dissection should be chosen to minimize deep SSI risk. Obese patients should be counseled on weight loss to try minimizing superficial SSI risk.

A methodological systematic review on surgical site infections following spinal surgery: part 2: prophylactic treatments.

Study Design. A methodological systematic review. Objective. To critically appraise the validity of preventive effects attributed to prophylactic treatments for surgical site infection (SSI) after spinal surgery. Summary of Background Data. As a result of a rapidly increasing number of spinal procedures, health care expenditure is expected to increase substantially in the foreseeable future. Administration of effective prophylactic treatments may prevent occurrence of SSIs and may thus result in lower costs. To date, however, no review appraising the methodological quality of studies evaluating prophylactic treatments for spinal SSIs has been published. Methods. Contemporary studies evaluating the preventive effect of prophylactic interventions on the rate of SSI after spinal surgery were searched through the Medline and EMBASE databases (January 2001 to December 2010). References were retrieved and bias-prone study features were abstracted individually and independently by 2 authors. Results. Eighteen eligible studies were identified, including 6 randomized controlled trials and 12 comparative cohort studies. Most often, antibiotic prophylaxis administration was investigated (n = 7). Included studies covered a wide variation of indications and surgical procedures. Except for 5 studies (28%), applied definitions of SSI outcomes were ambiguous. Although several important methodological aspects, including blinding of outcome assessors and attrition, were poorly reported in randomized controlled trials, these studies were far less susceptible to bias and confounding as observed in nonrandomized studies. None of the 12 cohort studies adjusted for confounding by matching, stratification, or multivariate regression techniques. Conclusion. Given the plethora of previously hypothesized confounding risk factors for a spinal SSI, conduct of nonrandomized comparative therapeutic studies is strongly discouraged. On the other hand, methodological safeguards, including use of standardized definitions of putative confounders and outcomes, should be considered in more detail during the design phase of a randomized trial.

Delirium After Spine Surgery in Older Adults: Incidence, Risk Factors, and Outcomes

To characterize the incidence, risk factors, and consequences of delirium in older adults undergoing spine surgery.

The timing of surgical staging has a significant impact on the complications and functional outcomes of adult spinal deformity surgery

BACKGROUND CONTEXTnTo our knowledge, the effect of the staging regimen on the surgical outcome in patients undergoing combined anterior/posterior surgery for the treatment of spinal deformity has not been previously studied.nnnPURPOSEnTo compare outcomes of anterior/posterior surgery for adult spinal deformity staged less than 21 days apart versus those 21 or more days apart.nnnSTUDY DESIGNnA retrospective comparison study.nnnPATIENT SAMPLEnPatients aged 40 years or older who underwent combined anterior/posterior fusions for spinal deformities.nnnOUTCOME MEASURESnSelf-reported measures, physiological measures, and functional measures.nnnMETHODSnWe retrospectively reviewed prospectively collected data for 63 consecutive patients (50 females and 13 males) older than 40 years who underwent combined anterior/posterior fusions for spinal deformities and who had a minimum of 2-year follow-up. We divided them into those who had surgery staged less than 21 days apart (Group 1, N=29) and those who had surgery staged 21 or more days apart (Group 2, N=34). The groups were not statistically different in age; preoperative American Society of Anesthesiologists, Scoliosis Research Society-22 (SRS-22) patient questionnaire, and Oswestry Disability Index (ODI) scores; number of previous surgeries; number of levels fused; or total operative time. Hotelling t square test and the chi-squared test were used to compare clinical and radiographic parameters, complications, and functional outcomes between groups (significance, p<.05).nnnRESULTSnCompared with Group 1 patients, Group 2 (staged) patients had a lower total estimated blood loss (average, 4.5 L [range, 1.90-8.75 L] vs. 4 L [range, 1.8-10.1 L], respectively), fewer combined hospital days (average, 14 days [range, 7-70 days] vs. 12 days [range, 6-44 days], respectively), and fewer major complications (total, 10 [35%] vs. 6 [18%], respectively). Preoperative SRS-22 and ODI scores were significantly better in Group 2 than in Group 1 at 6 weeks (p<.001) and at final follow-up (p<.001), respectively.nnnCONCLUSIONnFor patients who require both anterior and posterior surgery for spinal deformity correction, staging the two procedures 21 or more days apart decreases total perioperative transfusion requirements although significantly improving functional outcomes.