The effect of polymethylmethacrylate augmentation on the primary stability of stand-alone implant construct versus posterior stabilization in oblique lumbar interbody fusion with osteoporotic bone quality- a finite element study.

BACKGROUND CONTEXT: Oblique lumbar interbody fusion (OLIF) can provide an ideal minimally invasive solution for achieving spinal fusion in an older, more frail population where decreased bone quality can be a limiting factor. Stabilization can be achieved with bilateral pedicle screws (BPS), which require additional incisions and longer operative time. Alternatively, a novel self-anchoring stand-alone lateral plate system (SSA) can be used, where no additional incisions are required. Based on the relevant literature, BPS constructs provide greater primary biomechanical stability compared to lateral plate constructs, including SSA. This difference is further increased by osteoporosis. Screw augmentation in spinal fusion surgeries is commonly used; however, in the case of OLIF, it is a fairly new concept, lacking a consensus-based guideline. PURPOSE: This comparative finite element (FE) study aimed to investigate the effect of PMMA screw augmentation on the primary stability of a stand-alone implant construct versus posterior stabilization in OLIF with osteoporotic bone quality. STUDY DESIGN: The biomechanical effect of screw augmentation was studied inside an in-silico environment using computer-aided FE analysis. METHODS: A previously validated and published L2-L4 FE model with normal and osteoporotic bone material properties was used. Geometries based on the OLIF implants (BPS, SSA) were created and placed inside the L3-L4 motion segment with increasing volumes (1-6 cm3) of PMMA augmentation. A follower load of 400 N and 10 Nm bending moment (in the three anatomical planes) were applied to the surgical FE models with different bone material properties. The operated L3-L4 segmental range of motion (ROM), the inserted cage's maximal caudal displacements, and L4 cranial bony endplate principal stress values were measured. RESULTS: The nonaugmented values for the BPS construct were generally lower compared to SSA, and the difference was increased by osteoporosis. In osteoporotic bone, PMMA augmentation gradually decreased the investigated parameters and the difference between the two constructs as well. Between 3 cm3 and 4 cm3 of injected PMMA volume per screw, the difference between augmented SSA and standard BPS became comparable. CONCLUSIONS: Based on this study, augmentation can enhance the primary stability of the constructs and decrease the difference between them. Considering leakage as a possible complication, between 3 cm3 and 4 cm3 of injected PMMA per screw can be an adequate amount for SSA augmentation. However, further in silico, and possibly in vitro and clinical testing is required to thoroughly understand the investigated biomechanical aspects. CLINICAL SIGNIFICANCE: This study sheds light on the possible biomechanical advantage offered by augmented OLIF implants and provides a theoretical augmentation amount for the SSA construct. Based on the findings, the concept of an SSA device with PMMA augmentation capability is desirable.

Complication Pattern of Sacral Primary Tumor Resection: A Study on the Risk Factors of Surgical Site Infection and Bowel or Bladder Dysfunction and Their Associations with Length of Hospital Stay.

STUDY DESIGN: Retrospective open cohort study. PURPOSE: The current study aimed to explore the pattern of complications after primary sacral tumor resection, to investigate the possible effect of several perioperative parameters on the development of complications, and to identify which complications are associated with the length of hospital stay (LOS). OVERVIEW OF LITERATURE: Primary sacral tumor (pST) resection is associated with a high complication rate. However, the number of studies on these complications and their effect on LOS is limited. METHODS: The clinical data of 140 patients with pST surgeries and 106 subsequent patients with local recurrence surgeries in four subgroups (index surgery, local recurrence surgery, malignant, and benign tumor) were prospectively collected and analyzed. The prognostic value of several perioperative factors on the development of surgical site infection (SSI), bowel and bladder dysfunction (BBD), and LOS was investigated using the logistic and linear regression models. RESULTS: The overall complication rates were 61.2% after index surgeries and 50.9% after local recurrence surgeries. The most frequent complications were SSI, vegetative dysfunction, urinary tract infections, and neurological deterioration. Age >55 years, malignant tumors, and red blood cell transfusion had a predictive effect on the development of SSI in the logistic model (p<0.01, R2=0.43). Bilateral S2 or S3 resection commonly caused postoperative BBD (chi-square test=62.5, degrees of freedom=4, p<0.001). In the multiple linear regression model, wound dehiscence, BBD, systemic and urinary tract infection, cerebrospinal fluid leak, and neurologic deterioration were associated with a significantly long LOS (p<0.01, R2=0.62). CONCLUSIONS: Surgical resection of pSTs has a high complication rate. Its common complications are SSI and BBD, both of which can have a significant influence on global therapeutic outcome. Malignant tumor diagnosis, old age, and red blood cell transfusion can remarkably increase the risk of SSI. Further, the development of BBD is significantly associated with the number of resected sacral nerve roots. By decreasing perioperative complications, LOS can decrease significantly.

Global Treatment Outcome after Surgical Site Infection in Elective Degenerative Lumbar Spinal Operations.

Background: Surgical site infection (SSI) is a serious complication after routine lumbar spinal operations, and its effect on global treatment outcome (GTO) is less reported. The aim of the current study was to measure the impact of SSI on outcome, which was evaluated with patient reported outcome measures (PROMs) and patients' subjective judgment (GTO). Methods: A total of 910 patients underwent primary a single- or two-level lumbar decompression or instrumented fusion surgical procedure. Patients completed Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and Core Outcome Measurement Index (COMI) at baseline and at two-year follow-up. The rate of improvement in PROMs was measured for the total cohort and the group of patients with SSI. Patients evaluated GTO on a five-point Likert scale. This study was approved by the Scientific and Research Ethics Committee of the Medical Research Council (number: 29970-3/2015/EKU) and the Institutional Review Board. Results: Regardless of the presence of SSI, significant improvement was measured in all PROMs without any difference in the rate of change between the clinical subgroups (non-SSI vs. SSI, dODI: p = 0.370, dCOMI: p = 0.383, dVAS: p = 0.793). In the total cohort, 87.3% of patients reported good outcome (N% = 87.3%). After an SSI, however, more patients (25.7%) reported poor outcome compared with those without the complication (chi-square test: value = 5.66; df = 1; p = 0.017; odds ratio = 2.49). Conclusions: Patients with successfully treated SSI can expect as good objective clinical result as patients without SSI while the subjective treatment outcome can be worse. The GTO could also be improved in complicated cases, however, with more extensive peri-operative patient education and information considering the patients' expectations, too.

Risk factors for surgical site infection in elective routine degenerative lumbar surgeries.

BACKGROUND CONTEXT: Surgical site infection (SSI) is one of the most serious complications of spine surgery. Its predisposing factors, especially in routine surgeries, are less reported. However, a number of patient- and procedure-related risk factors could be avoided or at least determined preoperatively. Moreover, the patient-specific risk for SSI could be estimated before the elective surgery. PURPOSE: The aim of the present study was to analyze the preoperatively determinable risk factors for SSI in patients who require elective routine surgery related to lumbar disc degeneration and to build a multivariable model for the individual risk prediction. STUDY DESIGN: Analysis of prospectively collected standardized clinical data and the validation of the results on an independent prospective cohort were performed. PATIENT SAMPLE: One thousand thirty (N=1,030) patients were included in the study. All subjects underwent primary lumbar single- or two-level decompression, microdiscectomy, or instrumented fusion. OUTCOME MEASURES: Occurrence of an SSI defined according to the current Centers for Disease Control and Prevention guidelines that required surgical or nonsurgical therapy. METHODS: The effect of preoperative patient characteristics, comorbidities, disease history, and invasiveness of the elective surgery on the risk of SSI was determined in uni- and multivariate logistic regression models in the test cohort (N=723). The performance of the final multivariable regression model was assessed by measuring its discriminative ability (c-index) in receiver operating characteristic analysis. Performance of the multivariable risk estimation model was tested on the validation (N=307) cohort. RESULTS: The prevalence of SSI was 3.5% and 3.9% in the test and in the validation cohorts, respectively. The final multivariable regression model predictive (p=.003) for SSI contained the patient's age, body mass index (BMI), and the presence of 5 comorbidities, such as diabetes, ischemic heart disease, arrhythmia, chronic liver disease, and autoimmune disease as risk factors. The c-index of the model was 0.71, showing good discriminative ability, and it was confirmed by the data of the independent validation cohort (c=0.72). CONCLUSIONS: Predisposing factors for SSI were older age, higher BMI, and the presence of certain comorbidities in the present study. The cumulative number of risk factors significantly associated with the increasing risk for an SSI (p<.0001). Our model needs further validation but it may be used for individual risk assessment and reduction in the future.

Cross-cultural adaptation and validation of the Hungarian version of the Core Outcome Measures Index for the back (COMI Back).

PURPOSE: The Core Outcome Measure Index (COMI) is a short, multidimensional outcome instrument developed for the evaluation of patients with spinal conditions. The aim of this study was to produce a cross-culturally adapted and validated Hungarian version of the COMI Back questionnaire. METHODS: A cross-cultural adaptation of the COMI into Hungarian was carried out using established guidelines. Low back pain patients completed a booklet of questionnaires containing the Hungarian versions of COMI, Oswestry Disability Index (ODI) and WHO Quality of Life-BREF assessment (WHOQOL-BREF). The validation of the COMI included assessment of its construct validity, reliability, and responsiveness. RESULTS: 145 patients participated in the assessment of reliability and 159 surgically treated patients were included in the responsiveness study. Excellent correlation was found between COMI and ODI scores (rho = 0.83, p < 0.01). The COMI showed a very good correlation with the physical subscale of WHOQOL-BREF (rho = -0.75, p < 0.01) and pain (rho = 0.68, p < 0.01). Test-retest analysis showed that Hungarian COMI is a reliable measurement tool (ICC = 0.92) with an acceptable standard error of measurement (SEM = 0.59) and minimum detectable change (MDC = 1.63). Internal responsiveness analysis indicated a large effect size (1.16) for the change in COMI score after lumbar surgery. The area under the ROC curve (AUC) for the COMI score compared with the global outcome of the surgery was 0.87. CONCLUSION: The translation and cross-cultural adaptation of the COMI into the Hungarian language was successful, resulting in a reliable and valid measurement tool with good clinimetric properties.

[MEASURING THE FUNCTIONAL IMPAIRMENT OF THE LUMBAR SPINE]. / AZ ÁGYÉKI GERINC FUNKCIÓCSÖKKENÉSÉNEK MÉRÉSE.

BACKGROUND AND PURPOSE: The purpose of our study was to outline the Hungarian validation process of the Oswestry Disability Index, the Quebec Back Pain Disability Scale, the Roland-Morris Disability Questionnaire and the Core Outcome Measurement Index, as well as to draw up recommendations regarding their future applications. METHODS: The Hungarian versions were created after a cultural and linguistic adaptation. Next to the above-mentioned questionnaires, the questionnaire booklet used for validation also contained the WHOQoL-BREF general quality of life questionnaire and a pain measuring Visual Analog Scale. The data of low-back pain patients were registered twice in two weeks. We determined the internal homogeneity (Cronbach alpha), reproducibility, standard error of measurement and the minimal detectable change of the questionnaires. Patients were assigned into different two subgroups (surgical / non-surgical, with/without affection of nerve roots) and differences between the subgroups were examined with the help of the questionnaires. We determined the physical subscale of the WHOQoL-BREF and the correlation between the pain and the studied questionnaires. RESULTS: The value of Cronbach alpha was between 0.85 and 0.95. All four questionnaires showed significant differences (p<0.001) between the subgroups. The correlation studies brought strong and significant results (p<0.001, r>0.5) in every case. The values of reproducibility were between 0.93-0.92. The results of standard measurement error: 4.8 (Oswestry), 5.2 (Quebec), 1.6 (Roland-Morris), 0.59 (Core Index). The minimal detectable change was 13; 14; 4, and 2 points, respectively. CONCLUSION: The Hungarian versions of all four questionnaires are valid. They can be applied with scientific certainty to measure low back pain patients. From the studied questionnaires, we especially recommend the wide-raging application of the Oswestry Disability Index and the Core Outcome Measurement Index based on their psychometric and application features.

Validation of the Hungarian version of the Roland-Morris disability questionnaire.

PURPOSE: To create a cross-culturally adapted and clinically valid Hungarian version of the Roland-Morris Disability Questionnaire (RMQ). METHODS: After the translation and cross-cultural adaptation process, a total of 133 patients were included into the quality measurement study. Validity and reliability domains of the Hungarian RMQ were tested following the COSMIN guideline. Differences between clinically different patient groups were measured. Correlations of the RMQ with the Oswestry Disability Index (ODI), the World Health Organization Quality of Life-BREF assessment (WHOQoL) and pain were also calculated. To assess the reliability dimension, internal consistency (Cronbach's α) was determined and the test-retest method was used to calculate the interclass correlation coefficient (ICC), the standard error of measurement (SEM) and the minimal detectable change (MDC). RESULTS: Patients indicated for surgery or having neurological deficit had significantly higher RMQ scores. RMQ strongly correlated with pain (r = 0.61), ODI (r = 0.81) and physical subscale of WHOQoL (r = -0.7). Reliability of the Hungarian RMQ was expressed with a Cronbach's α of 0.87, ICC of 0.91 (p < 0.001) and SEM and MDC as 1.71 and 4.74 points, respectively. CONCLUSIONS: Translation and cross-cultural adaptation process of the RMQ into Hungarian language was successful resulting in a reliable and valid measurement tool with good psychometric properties. Implications for Rehabilitation Low back pain (LBP) related disability is a big health, social and economical problem in industrial countries. Correct evaluation of spine related disability can be performed using valid and reliable national versions of condition specific patient reported questionnaires such as the Roland-Morris Disability Questionnaire (RMQ). After the cross-cultural adaptation and validation of the Hungarian RMQ, it can be reliably used for the evaluation of LBP patients and for their follow-up during a rehabilitation process.

Primary Spinal Tumor Mortality Score (PSTMS): a novel scoring system for predicting poor survival.

BACKGROUND CONTEXT: Although the surgical and oncological therapies of primary spinal tumors (PSTs) have changed significantly over the last few decades, the prognosis of this rare disease is still poor. The decision-making process in the multidisciplinary management is handicapped by the lack of large-scale population-based prognostic studies. PURPOSE: The objective of the present study was to investigate preoperative factors associated with PST mortality and to develop a predictive scoring system of poor survival. STUDY DESIGN: This is a large-scale ambispective cohort study. PATIENT SAMPLE: The study included 323 consecutive patients with PSTs, treated surgically over an 18-year period at a tertiary care spine referral center for a population of 10 million. OUTCOME MEASURE: Survival was the outcome measure. METHODS: Patients were randomly divided into a training cohort (n=273) and a validation cohort (n=50). In the training cohort, 12 preoperative factors were investigated using Cox proportional hazard models. Based on the mortality-related variables, a simple scoring system of mortality was created, and three groups of patients were identified. Kaplan-Meier and log-rank analyses were used to compare the survival in the three groups. The model performance was assessed by measuring the discriminative ability (c-index) of the model and by applying a pseudo-R(2) goodness-of-fit test (Nagelkerke R(2), RN(2)). Internal validation was performed using bootstrapping in the training cohort and assessing the discrimination and explained variation of the model in the validation cohort. RESULTS: Patient age, spinal region, tumor grade, spinal pain, motor deficit, and myelopathy/cauda equina syndrome were significantly associated with poor survival in the multivariate analysis (p<.001, RN(2)=0.799). Based on these variables, we developed the Primary Spinal Tumor Mortality Score (PSTMS), where an eight-point scale was divided into three categories (low, medium, and high mortality). The three PSTMS categories were significantly associated with the overall survival (p<.001, RN(2)=0.811, c=0.82). The model performance remained similarly high in the validation cohort (RN(2)=0.831, c=0.81). CONCLUSIONS: The present study identifies six predictive variables for mortality in PSTs. Using these six variables, an easy-to-use scoring system was developed that can be applied to the estimation of postoperative survival in all types of PST patients.