Infection with Spinal Instrumentation: A 20-Year, Single-Institution Experience with Review of Pathogenesis, Diagnosis, Prevention, and Management

Interleukin-6 as a critical inflammatory marker for early diagnosis of surgical site infection after spine surgery

PURPOSE

Early diagnosis of surgical site infections (SSIs) could prevent surgical revision. Inflammatory markers (IMs), such as procalcitonin (PCT), interleukin-6 (IL-6), and tumor necrosis factor α (TNF-α), seem more accurate in diagnosing SSI than C-reactive protein (CRP) and white blood cell (WBC) count. The aim was to compare the predictive values of CRP, WBC count, PCT, IL-6, and TNF-α in SSI detection.

METHODS

A total of 130 patients undergoing dorsal spondylodesis from 2019 to 2024 were enrolled in a prospective diagnostic study at a maximum care spine center. IMs were measured preoperatively and on the postoperative days (PODs) 1, 2, 3, 5, and 7. Patients with high suspicion of SSI underwent revision surgery. SSI was diagnosed when the microbiological evidence was positive. Patients were divided a posteriori into the non-infection and infection groups.

RESULTS

IMs of 118 patients (66.9 ± 13.0 years, 61.0% females) were measured. Fifteen of the 118 patients (12.7%) developed an SSI. The groups differed with respect to existing hypertension, number of instrumented segments, region of surgery, CRPPOD1,7, PCTPOD7, and IL-6POD3,5,7. Binary logistic regression for SSI detection including these parameters showed an area under the curve (AUC) of 0.88 (95% CI 0.79-0.98; P < 0.001). The main effect for SSI detection was maintained by IL-6POD7 (odds ratio = 1.13; 95% CI 1.05-1.23; P = 0.001), which itself showed an AUC of 0.86 (95% CI 0.75-0.97).

CONCLUSION

Compared to CRP, WBC count, PCT, and TNF-α, IL-6 seems to be the critical IM for the early detection of an SSI.

TRIAL REGISTRATION

drks.de: DRKS00033773, date of registration: 29.02.2024, retrospectively registered; Postoperative Markers of Inflammation in Spine Surgery (POMIS) Trial.

Prophylactic Muscle Flaps Decrease Wound Complication Rates in Patients with Oncologic Spine Disease

BACKGROUND

Patients with oncologic spine disease face a high systemic illness burden and often require surgical intervention to alleviate pain and maintain spine stability. Wound healing complications are the most common reason for reoperation in this population and are known to impact quality of life and initiation of adjuvant therapy. Prophylactic muscle flap (MF) closure is known to reduce wound healing complications in high-risk patients; however, the efficacy in oncologic spine patients is not well established.

METHODS

A collaboration at our institution presented an opportunity to study the outcomes of prophylactic MF closure. The authors performed a retrospective cohort study of patients who underwent MF closure versus a cohort who underwent non-MF closure in the preceding time. Demographic and baseline health data were collected, as were postoperative wound complication data.

RESULTS

A total of 166 patients were enrolled, including 83 patients in the MF cohort and 83 control patients. Patients in the MF group were more likely to smoke ( P = 0.005) and had a higher incidence of prior spine irradiation ( P = 0.002). Postoperatively, five patients (6%) in the MF group developed wound complications, compared with 14 patients (17%) in the control group ( P = 0.028). The most common overall complication was wound dehiscence requiring conservative therapy, which occurred in six control patients (7%) and one MF patient (1%) ( P = 0.053).

CONCLUSIONS

Prophylactic MF closure during oncologic spine surgery significantly reduces the wound complication rate. Future studies should examine the precise patient population that stands to benefit most from this intervention.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Microbial spectrum, patient-specific factors, and diagnostics in implant-related postoperative spondylodiscitis

Aims

Implant-related postoperative spondylodiscitis (IPOS) is a severe complication in spine surgery and is associated with high morbidity and mortality. With growing knowledge in the field of periprosthetic joint infection (PJI), equivalent investigations towards the management of implant-related infections of the spine are indispensable. To our knowledge, this study provides the largest description of cases of IPOS to date.

Methods

Patients treated for IPOS from January 2006 to December 2020 were included. Patient demographics, parameters upon admission and discharge, radiological imaging, and microbiological results were retrieved from medical records. CT and MRI were analyzed for epidural, paravertebral, and intervertebral abscess formation, vertebral destruction, and endplate involvement. Pathogens were identified by CT-guided or intraoperative biopsy, intraoperative tissue sampling, or implant sonication.

Results

A total of 32 cases of IPOS with a mean patient age of 68.7 years (37.6 to 84.1) were included. Diabetes, age > 60 years, and history of infection were identified as risk factors. Patient presentation upon admission included a mean body temperature of 36.7°C (36.1 to 38.0), back pain at rest (mean visual analogue scale (VAS) mean 5/10) and when mobile (mean VAS 6/10), as well as elevated levels of CRP (mean 76.8 mg/l (0.4 to 202.9)) and white blood cell count (mean 9.2 units/nl (2.6 to 32.8)). Pathogens were identified by CT-guided or conventional biopsy, intraoperative tissue sampling, or sonication, and Gram-positive cocci presented as the most common among them. Antibiotic therapy was established in all cases with pathogen-specific treatment in 23 (71.9%) subjects. Overall 27 (84.4%) patients received treatment by debridement, decompression, and fusion of the affected segment.

Conclusion

Cases of IPOS are rare and share similarities with spontaneous spondylodiscitis. While procedures such as CT-guided biopsy and sonication are valuable tools in the diagnosis of IPOS, MRI and intraoperative tissue sampling remain the gold standard. Research on known principles of PJI such as implant retention versus implant exchange need to be expanded to the field of spine surgery.

Surgical Site Infection After Posterior Stabilization of the Spine - When do we Have to Remove the Implants?

STUDY DESIGN

Retrospective data analysis.

OBJECTION

The primary objective of this investigation was to analyze if treatment of Postoperative surgical site infections (PSSI) after posterior stabilization of the spine (PS) without radiological signs of screw loosening (RSL) shows a sufficient success rate without implant removal and if there was any difference between early and late PSSI.

SUMMARY OF BACKGROUND DATA

PSSI after PS are usually treated by implant removal and reinstrumentation if loosening of one of more screws is detected. There is presently no conclusive data that shows the success rate of the treatment of PSSI after PS without implant removal if no RSL are perceived.

MATERIALS AND METHODS

All patients who were treated for a PSSI after PS without RSL in a single spine center from 12/2009 to 03/2020 were enrolled in a retrospective analysis. Patients were treated by revision surgery with debridement and irrigation and subsequent antibiotic therapy. Implant removal was performed if the initial treatment did not lead to an improvement in wound healing and normalization of laboratory values. Statistical analysis was performed by Statistical Package for the Social Sciences 25. Descriptive data are given as mean and standard error of mean, a χ 2 test was performed.

RESULTS

Of the 32 enrolled patients, 17 had an early PSSI, 15 a late PSSI. In 71.9% (23/32), the PSSI was treated without implant removal: 12/17 in early PSSI, 11/15 in late PSSI. The difference was not significant ( P >0.05). One patient died, all other patients were discharged from the hospital with no remaining laboratory signs of the infection and with closed soft tissues.

CONCLUSIONS

In our group of patients, the success rate of irrigation and debridement without implant removal was 71.9%. In the light of this data, performing at least two irrigations and debridement before implant removal seems to be a valid treatment option in PSSI after PS if there are no RSL in early and late PSSI.

Postoperative Bildgebung der Wirbelsäule

Die Bildgebung der postoperativen Wirbelsäule hat im Wesentlichen zwei Aufgaben: Sie dient der Kontrolle des operativen Erfolgs und der Identifikation von Komplikationen. Dafür stehen die konventionelle Röntgenaufnahme, Computertomographie (CT), Myelographie und Magnetresonanztomographie (MRT) zur Verfügung. Unter Berücksichtigung der präoperativen Situation, der durchgeführten Operation und der postoperativen Beschwerdekonstellation ist es Aufgabe der Radiologinnen und Radiologen, die passende Modalität für eine suffiziente Diagnostik zu wählen. Insbesondere der Zustand nach Implantation von Fremdmaterial bedeutet eine technische Herausforderung im Rahmen der Bildakquisition. In der Befundung sehen sich die Radiologinnen und Radiologen mit der Aufgabe konfrontiert, zwischen natürlichen, zu erwartenden postoperativen Veränderungen und relevanten Komplikationen zu differenzieren. Ein reger Austausch mit Patientinnen und Patienten und zuweisenden Klinikerinnen und Klinikern ist dabei unerlässlich. Insbesondere klinische Hinweise auf einen Infekt, neue oder deutliche progrediente neurologische Ausfallserscheinungen und das Konus-Kauda-Syndrom erfordern eine zeitnahe Diagnosestellung, um eine rasche Therapieeinleitung zu gewährleisten.

A case of late-onset spondylodiscitis within the longest duration: 9 years after posterior instrumentation

Background

Spondylodiscitis is infections of the intervertebral disc and adjacent vertebral body with insidious onset. These infections are primarily haematogenous in origin. Early spinal infections after posterior spinal instrumentation usually occur within 3 months after surgery, whereas late infections may occur up to 8 years after surgery but are rare with an incidence of 1.9%.

Case presentation

We describe the case of a 66-year-old woman who complained of febrile back pain and developed late-onset spondylodiscitis 9 years after pedicle screw fixation, which is the longest-onset case. She was treated with surgical instrument removal and thorough debridement of the infected tissue with long-term antimicrobial treatment, with excellent results.

Conclusions

If there is radiculopathy and fever associated with spinal surgery in the history, it should be remembered that evaluation of lumbar spine MRI and acute phase reactions is crucial, and spondylodiscitis should also be considered in the preliminary diagnosis even after 9 years.

Late spinal infections are more common after pediatric than after adult spinal deformity surgery

PURPOSE

To compare the incidence, timing, and microbiologic factors associated with late spinal infection (onset ≥ 6 months after index operation) in pediatric versus adult spinal deformity patients who underwent instrumented posterior spinal fusion (PSF).

METHODS

We retrospectively queried our institutional database for pediatric (aged ≤ 21 years) and adult patients who underwent instrumented PSF from 2000 to 2015. Inclusion criteria were > 12-month follow-up, spinal arthrodesis spanning 4 or more levels, and idiopathic or degenerative spinal deformity. We included 1260 patients (755 pediatric, 505 adult). Incidence, timing, and microbiologic and operative parameters of late spinal infections were compared using chi-squared and Fisher exact tests. Alpha = 0.05.

RESULTS

Late spinal infection occurred in 28 (3.7%) pediatric and 2 (0.39%) adult patients (p = 0.009). Mean onset of infection was 4.2 years (range 0.7-12) in pediatric patients and 4.0 years (range 0.7-7.3) in adults (p = 0.93). Pediatric patients underwent arthrodesis spanning more levels (mean ± standard deviation, 10 ± 2.0) compared with adults (8.4 ± 3.3) (p < 0.001). Adults experienced greater intraoperative blood loss (2085 ± 1491 mL) compared with pediatric patients (796 ± 452 mL) (p < 0.001). Culture samples yielded positive growth in 11 pediatric and 2 adult cases. Propionibacterium and coagulase-negative staphylococci were the most commonly detected microorganisms in both cohorts.

CONCLUSION

Late spinal infections were significantly more common in pediatric patients than in adults after instrumented PSF for spinal deformity. Skin and indolent microorganisms were the primary identifiable causative bacteria in both cohorts.

LEVEL OF EVIDENCE

III.

Muscle Flap Closures in Spine Surgery: Predictors of Usage Patterns and Factors Associated With Postoperative Complications From the NSQIP Database

STUDY DESIGN

Retrospective cohort study using the National Surgical Quality Improvement Program.

OBJECTIVE

The objective of this study was to identify preoperative factors that impact the decision to perform prophylactic muscle flap closure and assess risk factors for wound healing complications in patients undergoing spinal procedures with and without muscle flap closure.

SUMMARY OF BACKGROUND DATA

Prior studies suggest that muscle flap closure following complex spine surgery results in a lower risk of wound healing complications. However, these studies have been limited to single institutions and/or surgeons.

METHODS

The National Surgical Quality Improvement Program database was queried for all patients undergoing spine surgery between 2005 and 2017 with and without concomitant muscle flaps. Preoperative and perioperative variables were extracted. Univariate and multivariate analyses were performed to assess risk factors influencing surgical site infection (SSI) and wound disruption, as well as to delineate which preoperative factors increased the likelihood of patients receiving flap closures a priori.

RESULTS

Concomitant muscle flaps were performed on 758 patients; 301,670 patients did not receive a flap. Overall 29 (3.83%) patients in the flap group experienced SSI compared to 5154 (1.71%) in the nonflap group (P<0.0001). Preoperative steroid use [odds ratio (OR) 0.5; P<0.0001], wound infection (OR 0.24; P<0.0001), elevated white blood cell count (OR 1.034; P<0.0001), low hematocrit (OR 0.94; P<0.0001), preoperative transfusion (OR 0.22; P=0.0068) were significantly associated with utilization of muscle flaps. Perioperative factors including a contaminated wound (OR 4.72; P<0.0001), the American Society of Anesthesiologists classification of severe disease (OR 1.92; P=0.024), and longer operative time (OR 1.001; P=0.0024) were significantly associated with postoperative wound disruption. In addition, after propensity score matching for these factors that increase risk of wound complications, there was no difference in the rates of SSI between the flap and nonflap group.

CONCLUSION

Our results suggest that patients with a higher burden of illness preoperatively are more likely to receive prophylactic paraspinal flaps which can reduce the rates of wound-related complications.

Multidisciplinary Approach to Multiple Multiresistant Agent Infection of Instrumented Spine Surgery: A Case Report

CASE

We report the case of a patient with consecutive infections with several multidrug-resistant agents-including carbapenem-resistant strains of Klebsiella pneumoniae among others-from a surgical wound infection after lumbar spine fusion, only successfully treated after the resort to novel antibiotics (ceftazidime-avibactam) in combination therapy.

CONCLUSIONS

Multidrug resistance has become a major challenge in today's medicine. Care should be taken to avoid their emergence, but when present, a multidisciplinary approach is mandatory to ensure clinically up-to-date treatment choices. Multimodal antibiotic schemes tend to show the most promising results, with which successful infection resolution can still be achieved.

Imaging Assessment of the Postoperative Spine: An Updated Pictorial Review of Selected Complications

Imaging of the postoperative spine requires the identification of several critical points by the radiologist to be written in the medical report: condition of the underlying cortical and cancellous bone, intervertebral disc, and musculoskeletal tissues; location and integrity of surgical implants; evaluation of the success of decompression procedures; delineation of fusion status; and identification of complications. This article presents a pictorial narrative review of the most common findings observed in noninstrumented and instrumented postoperative spines. Complications in the noninstrumented spine were grouped in early (hematomas, pseudomeningocele, and postoperative spine infection) and late findings (arachnoiditis, radiculitis, recurrent disc herniation, spinal stenosis, and textiloma). Complications in the instrumented spine were also sorted in early (hardware fractures) and late findings (adjacent segment disease, hardware loosening, and implant migration). This review also includes a short description of the most used diagnostic techniques in postoperative spine imaging: plain radiography, ultrasound (US), computed tomography (CT), magnetic resonance (MR), and nuclear medicine. Imaging of the postoperative spine remained a challenging task in the early identification of complications and abnormal healing process. It is crucial to consider the advantages and disadvantages of the imaging modalities to choose those that provide more accurate spinal status information during the follow-up. Our review is directed to all health professionals dealing with the assessment and care of the postoperative spine.

C-reactive protein in spinal surgery: more predictive than prehistoric

PURPOSE

In spinal surgery, surgical site infections (SSI) after dorsal spondylodesis lead to severe short- and long-term complications. Despite various clinical and serological evidence, the detection of a postoperative SSI remains crucial. In this retrospective cohort study, we determined the prognostic value of C-reactive protein (CRP) kinetics after open reduction and dorsal spondylodesis in the development of a SSI.

METHODS

We retrospectively analyzed 192 patients from 2016 to 2018 undergoing open reduction and dorsal spondylodesis with and without SSI for 20 days at a level-I trauma center and assessed their serological and clinical characteristics.

RESULTS

On day 7 and 8 after surgery, patients who developed a SSI displayed significantly higher CRP levels. A second peak after the initial maximum of CRP and a restricted failure to decline as well as a maximum CRP of more than 225 mg/l predict an infectious complication with a sensitivity of 92.9%, and a specificity of 78.2%. A binary logistic regression leads to 85.7% and 69.7%, respectively. A one-phase decay exponential regression can predict 75.6% of the variance after the initial peak of CRP.

CONCLUSION

Our study demonstrates a high value of postoperative CRP kinetics in SSI detection after dorsal spondylodesis. Moreover, we observed typical CRP levels with a specific course as indicative predictors that may facilitate an early SSI detection in clinical practice.

Surgical revision strategies for postoperative spinal implant infections (PSII)

Over the last years the number of spine surgeries with instrumentation has grown to an indispensable column in the treatment for different pathologies of the spine. A further increase in the incidence of instrumented spinal surgery is expected throughout the next years. Although the implementation and development of new techniques offer faster and more minimal invasive procedures, shortening surgery time, reducing soft tissue injury and revision due to hardware misplacement, the incidence of postoperative spinal implant infections (PSII) remains high. PSII related complications and revision procedures pose an enormous socioeconomic burden. Therefore, standardized strategies and protocols for treatment of PSII are urgently needed. While in former times hardware exchange or hardware removal was common practise in the field of spine surgery this approach has changed over the last years. Although the evidence from clinical studies in the field of PSII is of limited evidence, critical variables for revision strategies of PSII have been identified. Further, to quickly advance in the field of PSII it is certainly important to extrapolate and learn using data regarding the management from other fields of prosthetic joint infections. This should include clinical as well as experimental work in particular in the context of the biofilm, sonication as well as microbiological concepts. Over the last years, at our institution standardized procedures for diagnostic, surgical as well as antimicrobial treatment have been developed, based on the latest recommendations in peer-reviewed literature and our own data. Here we give an overview about surgical revision strategies for PSII and discuss the key points of our standardized protocol.

Future directions of postoperative spinal implant infections

This article outlines some promising future concepts against postoperative spinal implant infections on the basis of today available literature. The ever-adapting bacteria causing this common complication compel a corresponding continuous research about best effective treatment. The aim is to give a perspective on several future attack-points: surgical infection prevention strategies such as technical optimization of implants and surgical technique; faster diagnostic tools to detect infection, especially in the context of late infections with low-virulent germs and with regard to decision-making in the course of the surgical workflow; and combined surgical and medical treatment options against implant infections. The surgical treatment section will also state open issues concerning implant removal, and the medical treatment section will give an outlook to promising medical alternatives in a post-antibiotic era. To keep up in this field will be important to retain spine surgery in the future as the state-of-the-art treatment option for mandatory spinal interventions in the presence of tumor or trauma and even more so as an attractive option for patients with degenerative spinal disorder for improvement of their life quality.

Expandable Titanium Cages in the Emergent Treatment of Severe Spinal Deformity Secondary to Osteomyelitis: A Series of Three Complex Cases

The literature lacks robust evidence on the benefits versus risks of instrumenting and fusing the spinal column in the setting of active osteomyelitis. We report three patients with vertebral osteomyelitis and subsequent severe and complex kyphotic deformities. Patients 1 and 2 had previous instrumentation that required revision because of hardware failure in the thoracic and thoracolumbar regions, respectively. Patient 3 developed a severe cervical kyphotic deformity at 2 months after being diagnosed and treated with antibiotics for osteomyelitis, necessitating emergent instrumentation and fusion. All the three patients are doing very well so far. Spinal instrumentation and fusion for correction of kyphotic deformity is sometimes necessary in the context of active osteomyelitis and should be done emergently and without hesitation when spinal cord injury from spinal instability is of concern.