Quantification of cervical spinal stenosis by automated 3D MRI segmentation of spinal cord and cerebrospinal fluid space.

DESIGN: Prospective diagnostic study. OBJECTIVES: Anatomical evaluation and graduation of the severity of spinal stenosis is essential in degenerative cervical spine disease. In clinical practice, this is subjectively categorized on cervical MRI lacking an objective and reliable classification. We implemented a fully-automated quantification of spinal canal compromise through 3D T2-weighted MRI segmentation. SETTING: Medical Center - University of Freiburg, Germany. METHODS: Evaluation of 202 participants receiving 3D T2-weighted MRI of the cervical spine. Segments C2/3 to C6/7 were analyzed for spinal cord and cerebrospinal fluid space volume through a fully-automated segmentation based on a trained deep convolutional neural network. Spinal canal narrowing was characterized by relative values, across sever segments as adapted Maximal Canal Compromise (aMCC), and within the index segment as adapted Spinal Cord Occupation Ratio (aSCOR). Additionally, all segments were subjectively categorized by three observers as "no", "relative" or "absolute" stenosis. Computed scores were applied on the subjective categorization. RESULTS: 798 (79.0%) segments were subjectively categorized as "no" stenosis, 85 (8.4%) as "relative" stenosis, and 127 (12.6%) as "absolute" stenosis. The calculated scores revealed significant differences between each category (p ≤ 0.001). Youden's Index analysis of ROC curves revealed optimal cut-offs to distinguish between "no" and "relative" stenosis for aMCC = 1.18 and aSCOR = 36.9%, and between "relative" and "absolute" stenosis for aMCC = 1.54 and aSCOR = 49.3%. CONCLUSION: The presented fully-automated segmentation algorithm provides high diagnostic accuracy and objective classification of cervical spinal stenosis. The calculated cut-offs can be used for convenient radiological quantification of the severity of spinal canal compromise in clinical routine.

Minimally invasive resection of a prominent transverse process in neurogenic thoracic outlet syndrome: new application for a primarily spinal approach. Illustrative case.

BACKGROUND: The optimal surgical approach to treat neurogenic thoracic outlet syndrome (nTOS) depends on the individual patient's anatomy as well as the surgeon's experience. The authors present a minimally invasive posterior approach for the resection of a prominent transverse process to reduce local muscular trauma. OBSERVATIONS: A 19-year-old female presented with painful sensations in the right arm and severe fine-motor skill dysfunction in the right hand, each of which had been present for several years. Further examination confirmed affected C8 and T1 areas, and imaging showed an elongated C7 transverse process displacing the lower trunk of the brachial plexus. Decompression of the plexus structures by resection of the C7 transverse process was indicated, owing to persistent neurological effects. Surgery was performed using a minimally invasive posterior approach in which the nuchal soft tissue was bluntly dissected by dilatators and resection of the transverse process was done microscopically through a tubular retractor. The postoperative course showed a sufficient reduction of pain and paresthesia. LESSONS: The authors describe a minimally invasive posterior approach for the treatment of nTOS with the aim of providing indirect relief of strain on brachial plexus structures. The advantages of this technique include a small skin incision and minor soft tissue damage.

Free-Hand MIS TLIF without 3D Navigation-How to Achieve Low Radiation Exposure for Both Surgeon and Patient.

BACKGROUND: Transforaminal lumbar interbody fusion (TLIF) is one of the most frequently performed spinal fusion techniques, and this minimally invasive (MIS) approach has advantages over the traditional open approach. A drawback is the higher radiation exposure for the surgeon when conventional fluoroscopy (2D-fluoroscopy) is used. While computer-assisted navigation (CAN) reduce the surgeon's radiation exposure, the patient's exposure is higher. When we investigated 2D-fluoroscopically guided and 3D-navigated MIS TLIF in a randomized controlled trial, we detected low radiation doses for both the surgeon and the patient in the 2D-fluoroscopy group. Therefore, we extended the dataset, and herein, we report the radiation-sparing surgical technique of 2D-fluoroscopy-guided MIS TLIF. METHODS: Monosegmental and bisegmental MIS TLIF was performed on 24 patients in adherence to advanced radiation protection principles and a radiation-sparing surgical protocol. Dedicated dosemeters recorded patient and surgeon radiation exposure. For safety assessment, pedicle screw accuracy was graded according to the Gertzbein-Robbins classification. RESULTS: In total, 99 of 102 (97.1%) pedicle screws were correctly positioned (Gertzbein grade A/B). No breach caused neurological symptoms or necessitated revision surgery. The effective radiation dose to the surgeon was 41 ± 12 µSv per segment. Fluoroscopy time was 64 ± 34 s and 75 ± 43 radiographic images per segment were performed. Patient radiation doses at the neck, chest, and umbilical area were 65 ± 40, 123 ± 116, and 823 ± 862 µSv per segment, respectively. CONCLUSIONS: Using a dedicated radiation-sparing free-hand technique, 2D-fluoroscopy-guided MIS TLIF is successfully achievable with low radiation exposure to both the surgeon and the patient. With this technique, the maximum annual radiation exposure to the surgeon will not be exceeded, even with workday use.

Automated signal intensity analysis of the spinal cord for detection of degenerative cervical myelopathy - a matched-pair MRI study.

PURPOSE: Detection of T2 hyperintensities in suspected degenerative cervical myelopathy (DCM) is done subjectively in clinical practice. To gain objective quantification for dedicated treatment, signal intensity analysis of the spinal cord is purposeful. We investigated fully automated quantification of the T2 signal intensity (T2-SI) of the spinal cord using a high-resolution MRI segmentation. METHODS: Matched-pair analysis of prospective acquired cervical 3D T2-weighted sequences of 114 symptomatic patients and 88 healthy volunteers. Cervical spinal cord was segmented automatically through a trained convolutional neuronal network with subsequent T2-SI registration slice-by-slice. Received T2-SI curves were subdivided for each cervical level from C2 to C7. Additionally, all levels were subjectively classified concerning a present T2 hyperintensity. For T2-positive levels, corresponding T2-SI curves were compared to curves of age-matched volunteers at the identical level. RESULTS: Forty-nine patients showed subjective T2 hyperintensities at any level. The corresponding T2-SI curves showed higher signal variabilities reflected by standard deviation (18.51 vs. 7.47 a.u.; p < 0.001) and range (56.09 vs. 24.34 a.u.; p < 0.001) compared to matched controls. Percentage of the range from the mean absolute T2-SI per cervical level, introduced as "T2 myelopathy index" (T2-MI), was correspondingly significantly higher in T2-positive segments (23.99% vs. 10.85%; p < 0.001). ROC analysis indicated excellent differentiation for all three parameters (AUC 0.865-0.920). CONCLUSION: This fully automated T2-SI quantification of the spinal cord revealed significantly increased signal variability for DCM patients compared to healthy volunteers. This innovative procedure and the applied parameters showed sufficient diagnostic accuracy, potentially diagnosing radiological DCM more objective to optimize treatment recommendation. TRIAL REGISTRATION: DRKS00012962 (17.01.2018) and DRKS00017351 (28.05.2019).

Does the Pathologic Fracture Predict Severe Paralysis in Patients with Metastatic Epidural Spinal Cord Compression (MESCC)?-A Retrospective, Single-Center Cohort Analysis.

Currently, there is uncertainty about the predictive factors for metastatic epidural spinal cord compression (MESCC) and consecutive symptomatology in tumor patients. Prognostic algorithms for identifying patients at risk for paralysis are missing. The influence of the pathologic fracture on the patient's symptoms is widely discussed in the literature and we hypothesize that pathologic fractures contribute to spinal cord compression and are therefore predictive of severe paralysis. We tested this hypothesis in 136 patients who underwent surgery for spinal metastases. The most common primary cancers were prostate (24.3%, n = 33), breast (11.0%, n = 15), lung (10.3%, n = 14), and cancer of unknown primary (10.3%, n = 14). MESCC primarily affected the thoracic (77.2%, n = 105), followed by the lumbar (13.2%, n = 18) and cervical (9.6%, n = 13) spine. Pathologic fractures occurred in 63.2% (n = 86) of patients, mainly in osteolytic metastases. On the American spinal injury association (ASIA) impairment scale (AIS), 63.2% (n = 86) of patients exhibited AIS grade D and 36.8% (n = 50) AIS grade C-A preoperatively. The presence of a pathologic fracture alone did not predict severe paralysis (AIS C-A, p = 0.583). However, the duration of sensorimotor impairments, patient age, spinal instability neoplastic score (SINS), and the epidural spinal cord compression (ESCC) grade together predicted severe paralysis (p = 0.006) as did the ESCC grade 3 alone (p = 0.028). This is in contrast to previous studies that stated no correlation between the degree of spinal cord compression and the severity of neurologic impairments. Furthermore, the high percentage of pathologic fractures found in this study is above previously reported incidences. The risk factors identified can help to predict the development of paralysis and assist in the improvement of follow-up algorithms and the timing of therapeutic interventions.

Minimally invasive surgery for spinal cerebrospinal fluid leaks in spontaneous intracranial hypotension.

OBJECTIVE: Spinal CSF leaks cause spontaneous intracranial hypotension (SIH). Surgical closure of spinal CSF leaks is the treatment of choice for persisting leaks. Surgical approaches vary, and there are no studies in which minimally invasive techniques were used. In this study, the authors aimed to detail the safety and feasibility of minimally invasive microsurgical sealing of spinal CSF leaks using nonexpandable tubular retractors. METHODS: Consecutive patients with SIH and a confirmed spinal CSF leak treated at a single institution between April 2019 and December 2020 were included in the study. Surgery was performed via a dorsal 2.5-cm skin incision using nonexpandable tubular retractors and a tailored interlaminar fenestration and, if needed, a transdural approach. The primary outcome was successful sealing of the dura, and the secondary outcome was the occurrence of complications. RESULTS: Fifty-eight patients, 65.5% of whom were female (median age 46 years [IQR 36-55 years]), with 38 ventral leaks, 17 lateral leaks, and 2 CSF venous fistulas were included. In 56 (96.6%) patients, the leak could be closed, and in 2 (3.4%) patients the leak was missed because of misinterpretation of the imaging studies. One of these patients underwent successful reoperation, and the other patient decided to undergo surgery at another institution. Two other patients had to undergo reoperation because of insufficient closure and a persisting leak. The rate of permanent neurological deficit was 1.7%, the revision rate for a persisting or recurring leak was 3.4%, and the overall revision rate was 10.3%. The rate of successful sealing during the primary closure attempt was 96.6% and 3.4% patients needed a secondary attempt. Clinical short-term outcome at discharge was unchanged in 14 patients and improved in 25 patients, and 19 patients had signs of rebound intracranial hypertension. CONCLUSIONS: Minimally invasive surgery with tubular retractors and a tailored interlaminar fenestration and, if needed, a transdural approach is safe and effective for the treatment of spinal CSF leaks. The authors suggest performing a minimally invasive closure of spinal CSF leaks in specialized centers.

The Impact of Implementing a Radiation-Sparing Protocol for Percutaneous Kyphoplasty-A Prospective Dosemetric Study.

STUDY DESIGN: Prospective cohort study. OBJECTIVES: The purpose of this prospective study was to evaluate a protocol for radiation-sparing kyphoplasty by assessing dosemetrically recorded radiation exposures to both patient and surgeon. METHODS: This prospective clinical study examines the radiation exposure to patient and surgeon during single-level kyphoplasty in 32 thoracolumbar osteoporotic vertebral body fractures (12 OF 2, 9 OF 3, 11 OF 4 types) using a radiation aware surgical protocol between May 2017 and November 2019. The radiation exposure was measured at different locations using film, eye lens and ring dosemeters. Dose values are reported under consideration of lower detection limits of each dosemeter type. RESULTS: A high proportion of dosemeter readings was below the lower detection limits, especially for the surgeon (>90%). Radiation exposure to the surgeon was highest at the unprotected thyroid gland (0.053 ± 0.047 mSv), however only slightly above the lower detection limit of dosemeters (0.044 mSv). Radiation exposure to the patient was highest at the chest (0.349 ± 0.414 mSv) and the gonad (0.186 ± 0.262 mSv). Fluoroscopy time, dose area product and number of fluoroscopic images were 46.0 ± 17.9 sec, 124 ± 109 cGy×cm2, and 35 ± 13 per kyphoplasty, respectively. Back pain significantly improved from 6.8 ± 1.6 to 2.5 ± 1.7 on the numeric rating scale on the first postoperative day (P < 0.0001). CONCLUSIONS: The implementation of a strict intraoperative radiation protection protocol allows for safely performed kyphoplasty with ultra-low radiation exposure for the patient and surgeon without exceeding the annual occupational dose limits. TRIAL REGISTRATION: The study was registered in the German Clinical Trials Register (DRKS00011908, registration date 16/05/2017).

The challenge of measuring spinopelvic parameters: inter-rater reliability before and after minimally invasive lumbar spondylodesis.

BACKGROUND: The common manual measurement technique of spinal sagittal alignment on X-rays is susceptible to rater-dependent variability, which has not been adequately considered in previous publications. This study investigates the effect of those variations in the characterization of patients receiving lumbar spondylodesis. METHODS: General alignment parameters on pre- and postoperative X-rays were evaluated by four raters in 43 prospectively sampled patients undergoing monolevel spondylodesis. The Intra-class Correlation Coefficient (ICC) for each rater pair and all raters together was calculated for inter-rater reliability. For the operation-induced change of the sagittal alignment in every patient the Wilcoxon test was applied to compare for each rater separately. RESULTS: The ICCs were "good" (>0.75) to "excellent" (>0.9) for all raters together and for 45 of the 48 single rater pairs (93.75%). All revealed a significant increase of the addressed segmental lordosis and disc height and no significant change for spinopelvic parameters and sagittal vertical axis from pre- to postoperative. The lumbar lordosis showed a significant increase through the operation of +2.5° (p = 0.014) and +3.7° (p = 0.015) in two raters and no difference for the other ones (+2.1°, p = 0.171; -2.2°, p = 0.522). CONCLUSIONS: The pre- to postoperative change of lumbar lordosis revealed different significance levels for different raters, although the ICCs were formally good. Accordingly, the evaluation by only one rater would lead to different conclusions. Due to this susceptibility of alignment measurements to rater-dependent variability, the exact evaluation process should be described in every publication and the consistency of significant results be validated through multiple raters. TRIALS REGISTRATION: The trial was approved by the local ethics committee and listed at the national clinical trials register ( DRKS00004514 , date of registration: 08/11/2012).

Implant in situ assembly for all-posterior lumbar vertebral column resection. Technical note.

BACKGROUND: All-posterior lumbar VCR may be less invasive compared to combined retroperitoneal plus dorsal approaches. Stable lumbar vertebral body replacement requires implants with a large footprint to prevent implant subsidence. The narrow corridor between the lumbar nerve roots and the dural tube, however, impedes insertion of such implants via an exclusively posterior approach.To overcome this problem, we performed implant in situ assembly, a new method that enables all-posterior lumbar vertebral column resection (VCR) using large endplates. METHODS: Four patients underwent all-posterior lumbar VCR and in situ assembly of the implant. RESULTS: All-posterior lumbar VCR and insertion of an implant with large endplates to support adjacent vertebrae was feasible in all cases. CONCLUSIONS: Implant in situ assembly enables all-posterior lumbar VCR using large endplates.

Diffusion tensor imaging in unclear intramedullary tumor-suspected lesions allows separating tumors from inflammation.

DESIGN: Prospective diagnostic study. OBJECTIVES: Primary imaging-based diagnosis of spinal cord tumor-suspected lesions is often challenging. The identification of the definite entity is crucial for dedicated treatment and therefore reduction of morbidity. The aim of this trial was to investigate specific quantitative signal patterns to differentiate unclear intramedullary tumor-suspected lesions based on diffusion tensor imaging (DTI). SETTING: Medical Center - University of Freiburg, Germany. METHODS: Forty patients with an unclear tumor-suspected lesion of the spinal cord prospectively underwent DTI. Primary diagnosis was determined by histological or clinical work-up or remained indeterminate with follow-up. DTI metrics (FA/ADC) were evaluated at the central lesion area, lesion margin, edema, and normal spinal cord and compared between different diagnostic groups (ependymomas, other spinal cord tumors, inflammations). RESULTS: Mean DTI metrics for all spinal cord tumors (n = 18) showed significantly reduced FA and increased ADC values compared to inflammatory lesions (n = 8) at the lesion margin (p < 0.001, p = 0.001) and reduced FA at the central lesion area (p < 0.001). There were no significant differences comparing the neoplastic subgroups of ependymomas (n = 10) and other spinal cord tumors (n = 8), but remaining differences for both compared to the inflammation subgroup. We found significant higher ADC (p = 0.040) and a trend to decreased FA (p = 0.081) for ependymomas compared to inflammations at the edema. CONCLUSION: Even if distinct differentiation of ependymomas from other spinal cord neoplasms was not possible based on quantitative DTI metrics, FA and ADC were feasible to separate inflammatory lesions. This may avoid unnecessary surgery in patients with unclear intramedullary tumor-suspected lesions.

Double tubular minimally invasive spine surgery: a novel technique expands the surgical visual field during resection of intradural pathologies.

OBJECTIVE: A major challenge of a minimally invasive spinal approach (MIS) is maintaining freedom of maneuverability through small operative corridors. Unfortunately, during tubular resection of intradural pathologies, the durotomy and its accompanying tenting sutures offer a smaller operating window than the maximum surface of the tube's base. The objective of this study was to evaluate if a novel double tubular technique could expand the surgical visual field during MIS resection of intradural pathologies. METHODS: A total of 25 MIS resections of intradural extramedullary pathologies were included. A posterior tubular interlaminar fenestration was performed in all surgeries. A durotomy covering the whole diameter of the tubular base was the standard in all cases. After placement of two tenting sutures on each side of the durotomy and application of tension, the resulting surface of the achieved dura fenestration was measured after optical analysis of the intraoperative video. In the next step, a second tube, 2 mm thinner than and the same length as the first, was inserted telescopically into the first tube, resulting an angulated fulcrum effect on the tenting sutures. RESULTS: Optical surface analysis of the dura fenestration before and after the second tubular insertion verified a significant widening of the visual field of 43.1% (mean 18.84 mm2, 95% CI 16.8-20.8, p value < 0.001). There were no ruptured tenting sutures through the increased tension. Postoperative MRIs verified complete resection of the pathologies. CONCLUSIONS: Inserting a second tube telescopically during posterior minimally invasive tubular spinal intradural surgery leads to an angulated fulcrum effect on the dura tenting sutures which consequently increases the surface of the dura fenestration and induces a meaningful widening of the visual field.

Laminectomy and fusion in multilevel degenerative cervical myelopathy - Correlation between objective and subjective postoperative restriction of cervical spine mobility.

For patients with multilevel degenerative cervical myelopathy (DCM), laminectomy and fusion is an established technique. A concomitant effect of multilevel fusion is a restriction of cervical spine mobility. This retrospective study on DCM-patients with at least 4 laminectomy and fusion levels, compares data between objective and subjective restriction of the postoperative cervical spine mobility. The patient-reported restriction of cervical spine mobility was acquired by a five-step score. Measurements of cervical range of motion were performed using the CROM device and were correlated with the subjective scores. Fusion was performed over 6 levels in most of the 36 patients. For the subjective cervical spine mobility, 52.8% reported none to medium, 38.9% severe and 8.3% complete restriction. Mean objective cervical range of motion was 45.0° for flexion-extension, 26.3° for total lateral flexion and 51.4° for total rotation and therefore evidently reduced compared to non-operated patient cohorts in literature. There was a significant medium, negative correlation between the objective measurements and the patient-reported general restriction of cervical spine mobility, and with the physical component summary of SF-8. The significant objective reduction of cervical range of motion after laminectomy and multilevel fusion correlates with the patient-reported assessment for general restriction.

Spinal Cord Motion in Degenerative Cervical Myelopathy: The Level of the Stenotic Segment and Gender Cause Altered Pathodynamics.

In degenerative cervical myelopathy (DCM), focally increased spinal cord motion has been observed for C5/C6, but whether stenoses at other cervical segments lead to similar pathodynamics and how severity of stenosis, age, and gender affect them is still unclear. We report a prospective matched-pair controlled trial on 65 DCM patients. A high-resolution 3D T2 sampling perfection with application-optimized contrasts using different flip angle evolution (SPACE) and a phase-contrast magnetic resonance imaging (MRI) sequence were performed and automatically segmented. Anatomical and spinal cord motion data were assessed per segment from C2/C3 to C7/T1. Spinal cord motion was focally increased at a level of stenosis among patients with stenosis at C4/C5 (n = 14), C5/C6 (n = 33), and C6/C7 (n = 10) (p < 0.033). Patients with stenosis at C2/C3 (n = 2) and C3/C4 (n = 6) presented a similar pattern, not reaching significance. Gender was a significant predictor of higher spinal cord dynamics among men with stenosis at C5/C6 (p = 0.048) and C6/C7 (p = 0.033). Age and severity of stenosis did not relate to spinal cord motion. Thus, the data demonstrates focally increased spinal cord motion depending on the specific level of stenosis. Gender-related effects lead to dynamic alterations among men with stenosis at C5/C6 and C6/C7. The missing relation of motion to severity of stenosis underlines a possible additive diagnostic value of spinal cord motion analysis in DCM.

Does the postoperative cervical lordosis angle affect the cervical rotational range of motion after cervicothoracic multilevel fusion?

BACKGROUND: Laminectomy and multilevel fusion in patients with degenerative cervical myelopathy lead to severe restriction in cervical spine mobility. Since fusions from C2 to the thoracic spine result in a permanently stiff subaxial cervical spine, it seems obvious to restore physiological cervical lordosis, especially with regard to sagittal balance. However, there are reports that a fusion in a more lordotic position leads to a reduction of rotational cervical range of motion in the still mobile segments C0-C2. This study investigates the relationship between postoperative cervical lordosis and the objective rotational range of motion and subjective restriction. METHODS: In this single-center, retrospective cohort study, patients with degenerative cervical myelopathy operated via laminectomy and fusion from C2 to the thoracic spine were included. X-ray imaging was evaluated for common lordosis parameters. The patient-reported rotational restriction of cervical spine mobility was acquired by a five-step score. Objective rotational range of motion was measured. The radiological parameters for cervical lordosis (C2-C7 lordotic angle, C2-C7 Cobb angle) were correlated with the measurements and the patient-reported subjective scores. FINDINGS: We found a significant, medium negative correlation between the measurements for rotation and the C2-C7 lordotic angle and a significant, large negative correlation to the C2-C7 Cobb angle. For subjective restriction, no or only small correlation was observed. INTERPRETATION: We found significant negative correlations between radiological cervical lordosis and objective measurements for rotation. These results indicate that for this particular patient population, a stronger postoperative cervical lordosis does not seem favorable under the aspect of rotational range of motion.

Subjective and Objective Change in Cervical Spine Mobility After Single-level Anterior Cervical Decompression and Fusion.

STUDY DESIGN: Prospective, observational study. OBJECTIVE: The aim of this study was to collect objective and especially subjective data on changes in cervical spine mobility after single-level anterior cervical decompression and fusion (ACDF) and to investigate the impact on quality of life and activities of daily living (ADLs). SUMMARY OF BACKGROUND DATA: Although there are several studies dealing with the objective change in mobility after single-level ACDF, there are few data on how spondylodesis of a motion segment affects subjective restriction of cervical spine mobility. METHODS: Patients undergoing first-time, single-level ACDF for a symptomatic spondylotic process were eligible. Data were collected before surgery, at 3-month, and 1-year follow-up. Patients were assessed via clinical scores (pain intensity, Short-Form 8 [SF-8], among others) and asked for impairment in ADLs due to restriction of cervical spine mobility. The subjective restriction was acquired by a five-step patient-reported score. The range of motion was measured by the CROM device. RESULTS: Data of 97 patients could be evaluated. For pain scores and SF-8 there were significant improvements 3 months and 1 year after surgery (P < 0.001). The impairment for most ADLs improved 3 months after surgery and further after 1 year. The subjective restriction showed a significant improvement in general and for all single directions 1 year after surgery. In the objective measurements, a significantly higher total rotation could be found 1 year after surgery compared to preoperatively (101.6° ± 21.2 vs. 93.9° ± 23.4; P = 0.002). There were no significant differences in total flexion-extension and lateral flexion. Increasing age was a significant predictor for objective and subjective restriction. CONCLUSION: The concern of many patients of being severely restricted in their cervical spine mobility after single-level ACDF can be denied. Objectively, the rotation even showed a significant improvement. Regarding the subjective restriction, which is more important for the patients, we found a significant improvement in general and for all directions of movement after surgery.Level of Evidence: 3.

Autologous platelet-rich fibrin (PRF) augmentation as an add-on therapy in deep surgical site infections (dSSIs) after instrumented spinal surgery: preliminary results of a single institution case series.

BACKGROUND: Deep surgical site infections (dSSIs) after instrumented spinal surgery pose major therapeutic challenges. Standard treatment involves surgical debridement, wound drainage, and long-term antibiotic administration. Autologous platelet-rich fibrin (PRF) constitutes a biomaterial obtained from patients' own blood that contains leukocytes, chemokines and growth factors boosting cicatrization. Due to favorable results reported from other surgical disciplines such as dentistry, orthopedics, maxillofacial and plastic surgery using PRF, the authors hypothesized that PRF augmentation will promote wound healing in dSSIs. OBJECTIVE: To report our preliminary results on the safety and efficacy of autologous-PRF as an add-on therapy on a pilot case series of persistent dSSI after instrumented spinal surgery. METHODS: Among the 293 patients who underwent dorsal decompression and stabilization of the cervical, thoracic, and lumbar spine due to degenerative diseases in our department, 12 patients (4%) presented persisting dSSI after standard wound debridement and antibiotic treatment. PRF augmentation was used during a second surgical revision as an add-on therapy to standard debridement. In all cases, the wound was primarily closed without drains. RESULTS: Wound healing was completed between 14 and 21 days after the second surgical revision in all patients. At a median follow-up of 8 months (range: 6 to 18 months), no recurrence of dSSI nor complications were encountered in any case. CONCLUSIONS: Our preliminary results suggest that PRF augmentation in persistent dSSI after instrumented spinal surgery appears to be a safe and effective strategy to promote wound healing. Prospective controlled studies are required to define the efficiency of PRF more clearly in both treating and preventing dSSI.

Can UVA-light-activated riboflavin-induced collagen crosslinking be transferred from ophthalmology to spine surgery? A feasibility study on bovine intervertebral disc.

BACKGROUND: Collagen cross-links contribute to the mechanical resilience of the intervertebral disc (IVD). UVA-light-activated riboflavin-induced collagen crosslinking (UVA-CXL) is a well-established and effective ophthalmological intervention that increases the mechanical rigidity of the collagen-rich corneal matrix in Keratoconus. This study explores the feasibility, safety and efficacy of translating this intervention in reinforcing the IVD. METHODS: Annulus fibrosus (AF) cells were isolated from bovine IVDs and treated with different combinations of riboflavin (RF) concentrations (0.05-8 mM) and UVA light intensities (0.3-4 mW/cm2). Metabolic activity (resazurin assay), cell viability (TUNEL assay), and gene expression of apoptosis regulators C-FOS and PT5 were assessed immediately and 24 hours after treatment. Biomechanical effects of UVA-CXL on IVDs were measured by indentation analysis of changes in the instantaneous modulus and by peel-force delamination strength analysis of the AF prior and after treatment. RESULTS: Different intensities of UVA did not impair the metabolic activity of AF cells. However, RF affected metabolic activity (p < 0.001). PT53 expression was similar in all RF conditions tested while C-FOS expression decreased 24 hours after treatment. Twenty-four hours after treatment, no apoptotic cells were observed in any condition tested. Biomechanical characterizations showed a significant increase in the annular peel strength of the UVA-CXL group, when compared to controls of UVA and RF alone (p < 0.05). UVA-CXL treated IVDs showed up to 152% higher (p < 0.001) instantaneous modulus values compared to the untreated control. CONCLUSION: This is the first study on UVA-CXL treatment of IVD. It induced significantly increased delamination strength and instantaneous modulus indentation values in intact IVD samples in a structure-function relationship. RF concentrations and UVA intensities utilized in ophthalmological clinical protocols were well tolerated by the AF cells. Our findings suggest that UVA-CXL may be a promising tool to reinforce the IVD matrix.

Focal cervical spinal stenosis causes mechanical strain on the entire cervical spinal cord tissue - A prospective controlled, matched-pair analysis based on phase-contrast MRI.

BACKGROUND: Focally increased spinal cord motion at the level of cervical spinal stenosis has been revealed by phase-contrast MRI (PC-MRI). OBJECTIVE: To investigate spinal cord motion among patients suffering of degenerative cervical myelopathy (DCM) across the entire cervical spine applying automated segmentation and standardized PC-MRI post-processing protocols. METHODS: Prospective, matched-pair controlled trial on 29 patients with stenosis at C5/C6. MRI-protocol covering all cervical segments: 3D T2-SPACE, prospectively ECG-triggered sagittal PC-MRI. Segmentation by trained 3D hierarchical deep convolutional neural network and data processing were conducted via in-house software pipeline. Parameters per segment: maximum velocity, peak-to-peak (PTP)-amplitude, total displacement, PTP-amplitudeHB (PTP-amplitude per duration of heartbeat), and, for characterization of intraindividual alterations, the PTP-amplitude index between the cervical segments C3/C4-C7/T1 and C2/C3. RESULTS: Spinal cord motion was increased at C4/C5, C5/C6 and C6/C7 among patients (all parameters, p < 0.001-0.025). The PTP-amplitude index revealed an increase from C3/C4 to C4/C5 (p = 0.002), C4/C5 to C5/C6 (p = 0.037) and a decrease from C5/C6 to C6/C7 and C6/C7 to C7/T1 (p < 0.001, each). This implied an up-building stretch on spinal cord tissue cranial and a mechanical compression caudal of the stenotic level. Furthermore, significant far range effects across the entire cervical spinal cord were observed (e.g. PTP-amplitude C2/C3 vs. C6/C7, p = 0.026) in contrast to controls (p = 1.00). CONCLUSION: This study revealed the nature and extends of mechanical stress on the entire cervical spinal cord tissue due to focal stenosis. These pathophysiological alterations of spinal cord motion can be expected to be clinically relevant.

Long-Term Results after Multilevel Fusion of the Cervical Spine and the Cervicothoracic Junction: To Bridge or Not To Bridge?

OBJECTIVE: For patients with multilevel degenerative cervical myelopathy, laminectomy and fusion are widely accepted techniques for ameliorating the disorder. However, the idea of whether one should bridge the cervicothoracic junction to prevent instrument failure or adjacent segment disease has been a subject of controversial discussion. In the present study, we compared the incidence of these complications and the revision rates in multilevel fusions extending to C7 or T1-T3. METHODS: In the present single-center, retrospective cohort study, patients with multilevel degenerative cervical myelopathy treated with laminectomy and fusion to C7 or T1-T3 from 2004 to 2016 were included for evaluation. The primary outcome measure was radiologically proven complications at the most caudal level or the adjacent spinal fusion level. RESULTS: Laminectomy and multilevel fusion were performed in 84 patients. After applying the exclusion criteria, 20 patients with fusion to C7 (treated from 2004 to 2012; follow-up, 124.6 ± 10.6 months) and 38 patients with fusion to T1-T3 (treated from 2008 to 2016; follow-up, 58.2 ± 15.7 months) were evaluated. The incidence of complications at the most caudal or adjacent level of fusion was twice as high (P = 0.087; NS) in the C7 group (11 of 20; 55.0%) compared with the T1-T3 group (11 of 38; 28.9%). In the C7 group, 9 of the 20 patients (45.0%) had required revision surgery compared with 2 of 38 patients (5.3%) in the T1-T3 group (P = 0.001). CONCLUSIONS: We found that fewer revisions were necessary if the fusion had extended to the thoracic spine. Thus, we recommend bridging the cervicothoracic junction when fusion starts at C0-C3.