Learning curve analyses in spine surgery: a systematic simulation-based critique of methodologies.

BACKGROUND CONTEXT: Various statistical approaches exist to delineate learning curves in spine surgery. Techniques range from dividing cases into intervals for metric comparison, to employing regression and cumulative summation (CUSUM) analyses. However, their inherent inconsistencies and methodological flaws limit their comparability and reliability. PURPOSE: To critically evaluate the methodologies used in existing literature for studying learning curves in spine surgery and to provide recommendations for future research. STUDY DESIGN: Systematic literature review. METHODS: A comprehensive literature search was conducted using PubMed, Embase, and Scopus databases, covering articles from January 2010 to September 2023. For inclusion, articles had to evaluate the change in a metric of performance during human spine surgery across time/a case series. Results had to be reported in sufficient detail to allow for evaluation of individual performance rather than group/institutional performance. Articles were excluded if they included cadaveric/nonhuman subjects, aggregated performance data or no way to infer change across a number of cases. Risk of bias was assessed using the Risk of Bias in Nonrandomized Studies of Interventions (ROBINS-I) tool. Surgical data were simulated using Python 3 and then examined via multiple commonly used analytic approaches including division into consecutive intervals, regression and CUSUM techniques. Results were qualitatively assessed to determine the effectiveness and limitations of each approach in depicting a learning curve. RESULTS: About 113 studies met inclusion criteria. The majority of the studies were retrospective and evaluated a single-surgeon's experience. Methods varied considerably, with 66 studies using a single proficiency metric and 47 using more than 1. Operating time was the most commonly used metric. Interval division was the simplest and most commonly used method yet inherent limitations prevent collective synthesis. Regression may accurately describe the learning curve but in practice is hampered by sample size and model choice. CUSUM analyses are of widely varying quality with some being fundamentally flawed and widely misinterpreted however, others provide a reliable view of the learning process. CONCLUSION: There is considerable variation in the quality of existing studies on learning curves in spine surgery. CUSUM analyses, when correctly applied, offer the most reliable estimates. To improve the validity and comparability of future studies, adherence to methodological guidelines is crucial. Multiple or composite performance metrics are necessary for a holistic understanding of the learning process.

Outcomes following spinal instrumented fusions in patients with parkinson's disease: a systematic review and meta-analysis.

BACKGROUND: Parkinson's Disease (PD) patients represent challenging spinal surgery candidates due to associated frailty and deformity. This study consolidates the literature concerning spinal surgery outcomes in PD versus non-PD patients, to evaluate if PD predisposes patients to worse post-operative outcomes, so that treatment protocols can be optimised. METHODS: A systematic review and meta-analysis was conducted of PubMed/Medline, Embase, and Google Scholar databases per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies of interest included comparative (PD versus non-PD) cohorts undergoing spinal instrumented fusions. Post-operative clinical outcomes were collated and compared for significance between cohorts. Further analysis was made on outcomes based on the different surgical procedures performed (Anterior Cervical Discectomy and Fusion (ACDF), Thoracolumbar or Lumbar fusions, Thoracolumbar or Lumbar fusions without Osteoporotic Vertebral Compression fracture (OVCF) patients). All statistical analysis was performed using The R Project for Statistical Computing (version 4.1.2), with a p-value of < 0.05 deemed statistically significant. RESULTS: In total, 2,323,650 patients were included across 16 studies. Of those, 2,308,949 (99.37%) were patients without PD (non-PD), while 14,701 (0.63%) patients had PD at time of surgery. The collective mean age was 68.23 years (PD: 70.14 years vs non-PD: 64.86 years). Comparatively, there were 844,641 males (PD: 4,574; non-PD: 840,067) and 959,908 females (PD: 3,213; non-PD: 956,695). Overall, there were more post-operative complications in the PD cohort. Specifically, PD patients experienced significantly more surgical site infections (p = 0.01), increased rates of revision surgeries (p = 0.04) and increased venous thromboembolic events (p = 0.02) versus the non-PD cohort. In thoracolumbar/lumbar spinal fusions without OVCF patients, the PD cohort had increased rates of revision surgeries (p < 0.01) in comparison to the non-PD cohort. However, when including OVCF patients in thoracolumbar/lumbar spinal fusions, the PD cohort had significantly higher amounts of postoperative complications (p = 0.01), pneumonia (p = 0.02), and revision surgeries (p < 0.01) when compared to the non-PD cohort. CONCLUSION: Although more robust prospective studies are needed, the results of this study highlight the need for advanced wound care management in the postoperative period, both in-hospital and in the community, in addition to comprehensive multidisciplinary care from allied health professionals, with potential for the use of Enhanced Recovery After Surgery (ERAS) protocols in PD patients undergoing spinal instrumented fusions.

Mechanical Vertebral Body Augmentation Versus Conventional Balloon Kyphoplasty for Osteoporotic Thoracolumbar Compression Fractures: A Systematic Review and Meta-Analysis of Outcomes.

STUDY DESIGN: Systematic review and meta-analysis. OBJECTIVE: Surgical management of osteoporotic vertebral compression fractures (OVCFs) has traditionally consisted of vertebroplasty or kyphoplasty procedures. Mechanical percutaneous vertebral body augmentation (MPVA) systems have recently been introduced as alternatives to traditional methods. However, the effectiveness of MPVA systems vs conventional augmentation techniques for OVCFs remains unclear. This serves as the premise for this study. METHODS: A systematic review and meta-analysis was conducted as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies of interest included randomized controlled trials (RCTs) which directly compared patient outcomes following kyphoplasty to patients treated with MPVA systems. Clinical and radiological findings were collated and compared for significance between cohorts. RESULTS: 6 RCTs were identified with 1024 patients total. The mean age of all patients was 73.5 years. 17% of the cohort were male, 83% were female. 515 patients underwent kyphoplasty and 509 underwent mechanical vertebral body augmentation using MPVA systems. MPVAs showed similar efficacy for restoration of vertebral body height (P = .18), total complications (P = .36), cement extravasation (P = .58) and device-related complications (P = .06). MPVAs also showed reduced rates of all new fractures (16.4% vs 22.2%; P = .17) and adjacent fractures (14.7% vs 18.9%; P = .23), with improved visual analogue scale (VAS) scores at 6-month (P = .13). CONCLUSION: The results of this meta-analysis highlight no significant improvement in clinical or radiological outcomes for MPVA systems when compared to balloon kyphoplasty for vertebral body augmentation. Further research is needed to establish a true benefit over traditional operative methods.

Comparative surgical outcomes of navigated vs non-navigated posterior spinal fusions in ankylosing spondylitis patients.

INTRODUCTION: Ankylosing Spondylitis (AS) patients with acute spinal fractures represent a challenge for practicing spine surgeons due to difficult operative anatomy and susceptibility to complications. RESEARCH QUESTION: Does intraoperative CT-navigation improve outcomes in patients with ankylosing spondylitis undergoing surgery? METHODS: A retrospective review was carried out at our centre from 05/2016-06/2021 to identify AS patients presenting with a traumatic spinal fracture, managed surgically with posterior spinal fusion (PSF). Cohorts were categorised and compared for outcomes based on those who underwent PSF with intraoperative CT-navigation versus those surgically managed with traditional intraoperative fluoroscopy. RESULTS: 37 AS patients were identified. 29/37 (78.4%) underwent PSF. Intraoperative navigation was used in 14 (48.3%) cases. Mean age of the entire cohort was 67.6 years. No difference existed between the navigated and non-navigated groups for mean levels fused (5.35 vs 5.07; p â€‹= â€‹0.31), length of operation (217.9mins vs 175.3mins; p â€‹= â€‹0.07), overall length-of-stay (12 days vs 21.9 days; p â€‹= â€‹0.16), patients requiring HDU (3/14 vs 5/15; p â€‹= â€‹0.09) or ICU (5/14 vs 9/15; p â€‹= â€‹0.10), postoperative neurological improvement (1/14 vs 1/15; p â€‹= â€‹0.48) or deterioration (1/14 vs 0/15; p â€‹= â€‹0.15), intraoperative complications (2/14 vs 3/15; p â€‹= â€‹0.34), postoperative complications 4/14 vs 4/15; p â€‹= â€‹0.46), revision surgeries (3/14 vs 1/15; p â€‹= â€‹0.16) and 30-day mortality (0/14 vs 0/15). CONCLUSION: This is the first study that compares surgical outcomes of navigated vs non-navigated PSFs for AS patients with an acute spinal fracture. Although limited by its retrospective design and sample size, this study highlights the non-inferiority of intraoperative navigation as a surgical aid in a challenging cohort.

The efficacy of anchored stand-alone spacers in comparison to conventional cage and plate in anterior cervical discectomy and fusion surgery: A meta-analysis of randomised controlled trials for clinical and radiological outcomes.

Introduction: Anterior cervical discectomy and fusion (ACDF) is commonly performed with cage and plate constructs to stabilise diseased or injured cervical segments. Despite it being a commonly performed procedure, there are notable rates of associated morbidity reported in the literature. Stand-alone spacers represent a novel form of instrumentation to conventional cage and plate constructs. Research question: Do stand-alone spacers have improved operative characteristics and postoperative outcomes in ACDF cohorts when compared to cage and plate constructs? Methods: A systematic review and meta-analysis was conducted of PubMed/Medline, Embase and Google Scholar databases per the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes guidelines. Studies of interest included cage and plate instrumentation versus anchored stand-alone spacers for patients undergoing ACDF. Pre- and post-operative clinical and radiological outcomes were collated and compared for significance between cohorts. Results: 10 RCTs were identified and included with 779 patients total. Mean age of the entire cohort was 50.1 years. 62% (483/779) of the cohort were male. 384 patients underwent ACDF with stand-alone cage, while 395 had ACDF with conventional cage and plate. Stand-alone spacers significantly outperformed conventional instrumentation in terms of estimated blood loss (p < 0.01), total postoperative complications (p < 0.01), dysphagia rates (p = 0.04) and adjacent segment disease (p = 0.04). Non-inferiority was evident in both patient reported outcome measures and radiological outcomes. Conclusion: This meta-analysis highlights the efficacy of stand-alone spacers for the management of primarily cervical spondylitic disease for both single-level and multi-level pathology, and thus presents an attractive alternative to conventional instrumentation for patients undergoing ACDF surgery.

Accuracy of augmented reality-assisted pedicle screw placement: a systematic review.

OBJECTIVE: Conventional freehand methods of pedicle screw placement are associated with significant complications due to close proximity to neural and vascular structures. Recent advances in augmented reality surgical navigation (ARSN) have led to its adoption into spine surgery. However, little is known regarding its overall accuracy. The purpose of this study is to delineate the overall accuracy of ARSN pedicle screw placement across various models. METHODS: A systematic review was conducted of Medline/PubMed, Cochrane and Embase Library databases according to the PRISMA guidelines. Relevant data extracted included reports of pedicle screw placement accuracy and breaches, as defined by the Gertzbein-Robbins classification, in addition to deviation from pre-planned trajectory and entry point. Accuracy was defined as the summation of grade 0 and grade 1 events per the Gertzbein-Robbins classification. RESULTS: Twenty studies reported clinically accurate placed screws. The range of clinically accurate placed screws was 26.3-100%, with 2095 screws (93.1%) being deemed clinically accurate. Furthermore, 5.4% (112/2088) of screws were reported as grade two breaches, 1.6% (33/2088) grade 3 breaches, 3.1% (29/926) medial breaches and 2.3% (21/926) lateral breaches. Mean linear deviation ranged from 1.3 to 5.99 mm, while mean angular/trajectory deviation ranged 1.6°-5.88°. CONCLUSION: The results of this study highlight the overall accuracy of ARSN pedicle screw placement. However, further robust prospective studies are needed to accurately compare to conventional methods of pedicle screw placement.

The correlation between altmetric score and traditional measures of article impact for studies published within the Surgeon Journal.

Alternative metrics, or altmetrics, have emerged as a promising tool for measuring the social impact of research, which is increasingly important in today's digital and social media-driven world. Altmetric Attention Score (AAS) is a weighted count of all the online attention garnered by a study, and it is currently unclear whether a relationship with traditional bibliometrics exists. The purpose of this article was to retrospectively review articles published in the Surgeon Journal from 2003 to 2020 to compare AAS with bibliometric parameters using an Independent t-test and Pearson's correlation analysis. There were statistically significant weakly positive relationships between AAS and sample size, number of reads, and number of citations. There was no statistically significant relationship between AAS and number of authors, H-index, or level of evidence. This study highlights the potential value of altmetrics by measuring the social impact of research as altmetrics can provide valuable information not captured by traditional metrics. It is currently unclear what the optimal balance of social and academic impact is in evaluating research impact and how altmetrics can be integrated into existing research frameworks.

Preclinical to clinical translation for intervertebral disc repair: Effects of species-specific scale, metabolism, and matrix synthesis rates on cell-based regeneration.

Background: A significant hurdle for potential cell-based therapies is the subsequent survival and regenerative capacity of implanted cells. While many exciting developments have demonstrated promise preclinically, cell-based therapies for intervertebral disc (IVD) degeneration fail to translate equivalent clinical efficacy. Aims: This work aims to ascertain the clinical relevance of both a small and large animal model by experimentally investigating and comparing these animal models to human from the perspective of anatomical scale and their cellular metabolic and regenerative potential. Materials and Methods: First, this work experimentally investigated species-specific geometrical scale, native cell density, nutrient metabolism, and matrix synthesis rates for rat, goat, and human disc cells in a 3D microspheroid configuration. Second, these parameters were employed in silico to elucidate species-specific nutrient microenvironments and predict differences in temporal regeneration between animal models. Results: This work presents in silico models which correlate favorably to preclinical literature in terms of the capabilities of animal regeneration and predict that compromised nutrition is not a significant challenge in small animal discs. On the contrary, it highlights a very fine clinical balance between an adequate cell dose for sufficient repair, through de novo matrix deposition, without exacerbating the human microenvironmental niche. Discussion: Overall, this work aims to provide a path towards understanding the effect of cell injection number on the nutrient microenvironment and the "time to regeneration" between preclinical animal models and the large human IVD. While these findings help to explain failed translation of promising preclinical data and the limited results emerging from clinical trials at present, they also enable the research field and clinicians to manage expectations on cell-based regeneration. Conclusion: Ultimately, this work provides a platform to inform the design of clinical trials, and as computing power and software capabilities increase in the future, it is conceivable that generation of patient-specific models could be used for patient assessment, as well as pre- and intraoperative planning.

Cauda equina syndrome.

Aims: Patients with cauda equina syndrome (CES) require emergency imaging and surgical decompression. The severity and type of symptoms may influence the timing of imaging and surgery, and help predict the patient's prognosis. Categories of CES attempt to group patients for management and prognostication purposes. We aimed in this study to assess the inter-rater reliability of dividing patients with CES into categories to assess whether they can be reliably applied in clinical practice and in research. Methods: A literature review was undertaken to identify published descriptions of categories of CES. A total of 100 real anonymized clinical vignettes of patients diagnosed with CES from the Understanding Cauda Equina Syndrome (UCES) study were reviewed by consultant spinal surgeons, neurosurgical registrars, and medical students. All were provided with published category definitions and asked to decide whether each patient had 'suspected CES'; 'early CES'; 'incomplete CES'; or 'CES with urinary retention'. Inter-rater agreement was assessed for all categories, for all raters, and for each group of raters using Fleiss's kappa. Results: Each of the 100 participants were rated by four medical students, five neurosurgical registrars, and four consultant spinal surgeons. No groups achieved reasonable inter-rater agreement for any of the categories. CES with retention versus all other categories had the highest inter-rater agreement (kappa 0.34 (95% confidence interval 0.27 to 0.31); minimal agreement). There was no improvement in inter-rater agreement with clinical experience. Across all categories, registrars agreed with each other most often (kappa 0.41), followed by medical students (kappa 0.39). Consultant spinal surgeons had the lowest inter-rater agreement (kappa 0.17). Conclusion: Inter-rater agreement for categorizing CES is low among clinicians who regularly manage these patients. CES categories should be used with caution in clinical practice and research studies, as groups may be heterogenous and not comparable.

Presentation, management, and outcomes of cauda equina syndrome up to one year after surgery, using clinician and participant reporting: A multi-centre prospective cohort study.

Background: Cauda equina syndrome (CES) results from nerve root compression in the lumbosacral spine, usually due to a prolapsed intervertebral disc. Evidence for management of CES is limited by its infrequent occurrence and lack of standardised clinical definitions and outcome measures. Methods: This is a prospective multi-centre observational cohort study of adults with CES in the UK. We assessed presentation, investigation, management, and all Core Outcome Set domains up to one year post-operatively using clinician and participant reporting. Univariable and multivariable associations with the Oswestry Disability Index (ODI) and urinary outcomes were investigated. Findings: In 621 participants with CES, catheterisation for urinary retention was required pre-operatively in 31% (191/615). At discharge, only 13% (78/616) required a catheter. Median time to surgery from symptom onset was 3 days (IQR:1-8) with 32% (175/545) undergoing surgery within 48 h. Earlier surgery was associated with catheterisation (OR:2.2, 95%CI:1.5-3.3) but not with admission ODI or radiological compression. In multivariable analyses catheter requirement at discharge was associated with pre-operative catheterisation (OR:10.6, 95%CI:5.8-20.4) and one-year ODI was associated with presentation ODI (r = 0.3, 95%CI:0.2-0.4), but neither outcome was associated with time to surgery or radiological compression. Additional healthcare services were required by 65% (320/490) during one year follow up. Interpretation: Post-operative functional improvement occurred even in those presenting with urinary retention. There was no association between outcomes and time to surgery in this observational study. Significant healthcare needs remained post-operatively. Funding: DCN Endowment Fund funded study administration. Castor EDC provided database use. No other study funding was received.

Morbidity and mortality of traumatic cervical spinal cord injuries in a geriatric cohort.

BACKGROUND: Traumatic injuries are among the leading causes of death and disability worldwide. Major trauma presentations have seen a demographic shift recently from the young to the elderly, with significant associated neurological deficit. AIMS: To review the presentation and outcome of elderly patients presenting with cervical spinal injuries and associated neurological deficit that underwent surgical intervention in order to optimise treatment strategies. METHODS: A retrospective review was conducted at a national tertiary referral centre to analyse admission trends from June 2016 to July 2020 for outcomes of elderly patients (≥ 65) presenting with traumatic cervical spine injuries associated with spinal cord injuries (SCI). Demographic, clinical, and radiological characteristics were collected and analysed. RESULTS: Forty-two patients met the inclusion criteria. The most common mechanisms of injury (MOIs) were falls from standing (38.1%) and falls from height (≥ 2 m) (33.3%). Complete SCIs had increased mean LOS (57.6 vs 21.6 days; p = 0.013), postoperative complications (100% vs 60.6%; p = 0.022), life-threatening complications (57.1% vs 9.1%; p = 0.001), and 90-day mortality (37.5% vs 5.9%; p = 0.007) compared to incomplete SCIs. CONCLUSION: Elderly patients with complete SCIs have poorer outcomes and mortality than those with less extensive SCIs. They require more resources, have greater risk of complications, and have higher mortality than those with incomplete SCIs, with subsequent implications on optimal treatment strategies. More robust studies are needed to derive improved risk stratification tools for geriatric patients with spinal injuries.

The Incidence, Characteristics and Outcomes of Vertebral Artery Injury Associated with Cervical Spine Trauma: A Systematic Review.

STUDY DESIGN: Systematic Review. OBJECTIVES: Vertebral Artery Injury (VAI) is a potentially serious complication of cervical spine fractures. As many patients can be asymptomatic at the time of injury, the identification and diagnosis of VAI can often prove difficult. Due to the high rates of morbidity and mortality associated with VAI, high clinical suspicion is paramount. The purpose of this review is to elucidate incidence, diagnosis, treatment and outcomes of VAI associated with cervical spine injuries. METHODS: A systematic search of electronic databases was performed using 'PUBMED', 'EMBASE','Medline (OVID)', and 'Web of Science, for articles pertaining to traumatic cervical fractures with associated VAI. RESULTS: 24 studies were included in this systematic review. Data was included from 48 744 patients. In regards to the demographics of the focus groups that highlighted information on VAI, the mean average age was 46.6 (32.1-62.6). 75.1% (169/225) were male and 24.9% (56/225) were female. Overall incidence of VAI was 596/11 479 (5.19%). 190/420 (45.2%) of patients with VAI had fractures involving the transverse foramina. The right vertebral artery was the most commonly injured 114/234 (48.7%). V3 was the most common section injured (16/36 (44.4%)). Grade I was the most common (103/218 (47.2%)) injury noted. Collective acute hospital mortality rate was 32/226 (14.2%), ranging from 0-26.2% across studies. CONCLUSION: VAI secondary to cervical spine trauma has a notable incidence and high associated mortality rates. The current available literature is limited by a low quality of evidence. In order to optimise diagnostic protocols and treatment strategies, in addition to reducing mortality rates associated with VAI, robust quantitative and qualitative studies are needed.

Demographics of Cauda Equina Syndrome: A Population-Based Incidence Study.

INTRODUCTION: Cauda equina syndrome (CES) has significant medical, social, and legal consequences. Understanding the number of people presenting with CES and their demographic features is essential for planning healthcare services to ensure timely and appropriate management. We aimed to establish the incidence of CES in a single country and stratify incidence by age, gender, and socioeconomic status. As no consensus clinical definition of CES exists, we compared incidence using different diagnostic criteria. METHODS: All patients presenting with radiological compression of the cauda equina due to degenerative disc disease and clinical CES requiring emergency surgical decompression during a 1-year period were identified at all centres performing emergency spinal surgery across Scotland. Initial patient identification occurred during the emergency hospital admission, and case ascertainment was checked using ICD-10 diagnostic coding. Clinical information was reviewed, and incidence rates for all demographic and clinical groups were calculated. RESULTS: We identified 149 patients with CES in 1 year from a total population of 5.4 million, giving a crude incidence of 2.7 (95% CI: 2.3-3.2) per 100,000 per year. CES occurred more commonly in females and in the 30-49 years age range, with an incidence per year of 7.2 (95% CI: 4.7-10.6) per 100,000 females age 30-39. There was no association between CES and socioeconomic status. CES requiring catheterization had an incidence of 1.1 (95% CI: 0.8-1.5) per 100,000 adults per year. The use of ICD-10 codes alone to identify cases gave much higher incidence rates, but was inaccurate, with 55% (117/211) of patients with a new ICD-10 code for CES found not to have CES on clinical notes review. CONCLUSION: CES occurred more commonly in females and in those between 30 and 49 years and had no association with socioeconomic status. The incidence of CES in Scotland is at least four times higher than previous European estimates of 0.3-0.6 per 100,000 population per year. Incidence varies with clinical diagnostic criteria. To enable comparison of rates of CES across populations, we recommend using standardized clinical and radiological criteria and standardization for population structure.