Biomechanical and ergonomic risks associated with cervical musculoskeletal dysfunction amongst surgeons: A systematic review

INTRODUCTION

Surgeons are at high risk of developing musculoskeletal symptoms due to a range of factors including, maladaptive positioning and surgical ergonomics. Cervical muscle strain and biomechanical load is most prevalent due to repetitive motions and prolonged static neck positioning. This issue is apparent through reports of prevalence between 10 and 74.4% among surgeons. The aim of this systematic review is to provide an objective assessment of the clinical evidence available and a descriptive analysis of the effects of kinematics and surgical ergonomics on the prevalence of surgeons' cervical musculoskeletal pain.

METHODS

This is PRISMA-compliant systematic review of clinical studies assessing the prevalence of cervical musculoskeletal dysfunction in surgeons by searching PUBMED and Ovid EMBASE databases from inception to 19th October 2023. Study quality was graded according to the National Institutes of Health study quality assessment tools.

RESULTS

A total of 9 studies were included in the final qualitative analysis. The use of loupes, open surgery and excessive neck flexion (>30°) were associated with cervical dysfunction. Comparison of study outcomes was challenging due to heterogeneity within study methods and the paucity of methodological quality.

CONCLUSION

The current literature assessing ergonomic and biomechanical factors predisposing surgeons to cervical musculoskeletal dysfunction is insufficient to provide reliable guidance for clinicians. Although the literature identifies factors contributing to work-related cervical dysfunction, few attempt to evaluate interventions for improved surgical ergonomics. An objective assessment of interventions that prompt postural correction with the aim to improve neck pain in surgeon cohorts is warranted.

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 ​= ​0.31), length of operation (217.9mins vs 175.3mins; p ​= ​0.07), overall length-of-stay (12 days vs 21.9 days; p ​= ​0.16), patients requiring HDU (3/14 vs 5/15; p ​= ​0.09) or ICU (5/14 vs 9/15; p ​= ​0.10), postoperative neurological improvement (1/14 vs 1/15; p ​= ​0.48) or deterioration (1/14 vs 0/15; p ​= ​0.15), intraoperative complications (2/14 vs 3/15; p ​= ​0.34), postoperative complications 4/14 vs 4/15; p ​= ​0.46), revision surgeries (3/14 vs 1/15; p ​= ​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 correlation between altmetric score and traditional measures of article impact for studies pertaining to spine trauma

PURPOSE

It is becoming increasingly common for researchers to share scientific literature via social media. Traditional bibliometrics have long been utilized to measure a study's academic impact, but they fail to capture the impact generated through social media sharing. 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.

METHODS

We identified the five highest-rated spine-specific and five highest-rated general orthopedic journals by Scopus CiteScore 2020. We then identified all the spine trauma studies across a 5-year span (2016-2020) within these journals and compared AAS with traditional bibliometrics using Independent t-tests and Pearson's correlational analyses.

RESULTS

No statistically significant relationships were identified between AAS and traditional bibliometrics for articles pertaining to spine trauma: Level of Evidence (R = - 0.02, p = 0.34), H-Index Primary Author (R =  < - 0.01, p = 0.50), H-Index Senior Author (R = - 0.04, p = 0.24), and Number of Citations (R = 0.01, p = 0.40). The top five articles by AAS include those pertaining to motorcycle injuries (AAS = 687), orthosis in thoracolumbar fractures (AAS = 199), golfing injuries (AAS = 166), smartphone-based teleradiology (AAS = 41), and auto racing injuries (AAS = 39).

CONCLUSION

The lack of overlap between these types of metrics suggests that AAS or similar alternative metrics should be used to measure an article's social impact. The social impact of an article should likewise be a factor in determining an article's overall impact along with its academic impact as measured by bibliometrics.

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.

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.

Iliac crest bone graft versus cell-based grafts to augment spinal fusion: a systematic review and meta-analysis

INTRODUCTION

Despite successful fusion rates with iliac crest bone graft (ICBG), donor-site morbidity and increased operating time remain a considerable limitation and drive the search for alternatives. In this systematic review, grafts with additional cellular supplementation were compared with ICBG for spinal arthrodesis. We compared safety, efficacy and long-term outcomes, thus providing the current and relevant evidence for orthopaedic surgeons to make informed choices regarding this rapidly developing field.

METHODS

An electronic literature search was conducted according to the PRISMA guidelines by two independent reviewers for articles published up to 1st March 2023 using PubMed, EMBASE and the Cochrane Central Register of Controlled Trial. Cellular allografts were not included. The following data were extracted: Number of patients, type of graft, fusion assessment method, follow-up duration, fusion rates, clinical outcomes and complications. The methodological quality of evidence (MQOE) was assessed using the Risk of Bias 2 (RoB-2) tool and Risk of Bias In Non-Randomised Studies (ROBINS) tool developed by Cochrane for evaluating bias in randomised and non-randomised studies.

RESULTS

Ten studies fulfiled the inclusion criteria, including 465 patients. The mean number of patients per study was 43.8 (std dev. 28.81, range 12-100). Two studies demonstrated cell-based therapy to be significantly more successful in terms of fusion rates compared to ICBG. However, the remaining eight demonstrated equivocal results. No study found that cell-based therapy was inferior. No difference was seen between the two groups in three studies who focused on degenerative cohorts. No difference in functional outcome scores was seen between the groups. A number of different preparation techniques for cell-based grafts were used throughout the studies.

CONCLUSION

Cell-based therapy offers a promising alternative to ICBG in spinal fusion surgery, which could help reduce the associated morbidity to patients. This review found that cell-based therapy is non-inferior to iliac crest bone graft and may offer patients an alternative treatment option with fewer complications and reduced post-operative pain. However, the literature to date is limited by heterogeneity of the cell preparation and grafting process. Future research with a unified approach to the cell preparation process is required to fully delineate the potential advantages of this technology.

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.

IgE, IgE Receptors and Anti-IgE Biologics: Protein Structures and Mechanisms of Action

The evolution of IgE in mammals added an extra layer of immune protection at body surfaces to provide a rapid and local response against antigens from the environment. The IgE immune response employs potent expulsive and inflammatory forces against local antigen provocation, at the risk of damaging host tissues and causing allergic disease. Two well-known IgE receptors, the high-affinity FcεRI and low-affinity CD23, mediate the activities of IgE. Unlike other known antibody receptors, CD23 also regulates IgE expression, maintaining IgE homeostasis. This mechanism evolved by adapting the function of the complement receptor CD21. Recent insights into the dynamic character of IgE structure, its resultant capacity for allosteric modulation, and the potential for ligand-induced dissociation have revealed previously unappreciated mechanisms for regulation of IgE and IgE complexes. We describe recent research, highlighting structural studies of the IgE network of proteins to analyze the uniquely versatile activities of IgE and anti-IgE biologics.

Risk factors for distal junctional failure in long-construct instrumentation for adult spinal deformity

PURPOSE

The aim of this study is to identify risk factors associated with postoperative DJF in long constructs for ASD.

METHODS

A retrospective review was performed at a tertiary referral spine centre from 01/01/2007 to 31/12/2016. Demographic, clinical and radiographic parameters were collated for patients with DJF in the postoperative period and compared to those without DJF. Survival analyses were performed using univariate logistic regression to identify variables with a p value < 0.05 for inclusion in multivariate analysis. Spearman's correlations were performed where applicable.

RESULTS

One hundred two patients were identified. 41 (40.2%) suffered DJF in the postoperative period, with rod fracture being the most common sign of DJF (13/65; 20.0%). Mean time to failure was 32.4 months. On univariate analysis, pedicle subtraction osteotomy (p = 0.03), transforaminal lumbar interbody fusion (p < 0.001), pre-op LL (p < 0.01), pre-op SVA (p < 0.01), pre-op SS (p = 0.02), postop LL (p = 0.03), postop SVA (p = 0.01), postop PI/LL (p < 0.001), LL correction (p < 0.001), SVA correction (p < 0.001), PT correction (p = 0.03), PI/LL correction (p < 0.001), SS correction (p = 0.03) all proved significant. On multivariate analysis, pedicle subtraction osteotomy (OR 27.3; p = 0.03), postop SVA (p < 0.01) and LL correction (p = 0.02) remained statistically significant as independent risk factors for DJF.

CONCLUSION

Recently, DJF has received recognition as its own entity due to a notable postoperative incidence. Few studies to date have evaluated risk factors for DJF. The results of our study highlight that pedicle subtraction osteotomy, poor correction of lumbar lordosis, and sagittal vertical axis are significantly associated with postoperative occurrence of DJF.

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.

Preoperative Considerations for the Frail Patient

Frailty is a common geriatric syndrome, the relevance of which is becoming increasingly apparent in the clinical setting. It is often accompanied by varying degrees of sarcopenia and/or osteoporosis, leading to a decline in physical function, decreased levels of physical activity, and overall poorer health outcomes in older adults. Identifying this cohort of patients before stressor events such as spinal surgery can prove paramount to improving the postoperative outcomes of these patients. This review provides a pertinent descriptive analysis to aid identification of frailty in a clinical setting, in addition to outlining methods of preoperative intervention that may improve postoperative outcomes.

Pharmacogenetic profiling and individualised therapy in the treatment of degenerative spinal conditions

Patients presenting with degenerative spinal changes are often poor surgical candidates due to associated co-morbidities, frailty, or sarcopenia. Additionally, surgeries of a degenerative spine can prove difficult due to the distortion of normal surgical anatomy. Therefore, many patients are managed conservatively with a variety of modalities, including over-the-counter and prescription medications. Nevertheless, several patients do not experience adequate relief from pain with analgesic medications, precipitating multiple hospital visits, and usage of resources. As a result, back pain is regarded as a major economic burden, with total costs of associated treatment exceeding $100 billion annually. Pharmacogenetics is a relatively novel method of evaluating an individual's response to analgesic medications, through analysis of germline polymorphisms. It entails obtaining a genetic sample, often via buccal swab or peripheral blood sample, and genetic analysis achieved through either polymerase chain reaction +/- Sanger sequencing, microassays, restriction length fragment polymorphism analysis, or genetic library preparation and next generation sequencing. The potential efficacy of pharmacogenetic analysis has been highlighted across several specialities to date. However, a paucity of evidence exists regarding spine surgery populations. Nevertheless, regular prospective pharmacogenetic analysis may ultimately prove beneficial when concerning degenerative spinal cohorts due to aforementioned surgical and economic considerations. The purpose of this narrative review is to outline how metaboliser profile variants affect the pharmacokinetics of specific analgesia used to treat back pain, and to discuss the current potential and limitations of employing regular pharmacogenetic analysis for spine surgery populations with degenerative conditions.

The relationship between radiological paraspinal lumbar measures and clinical measures of sarcopenia in older patients with chronic lower back pain

Objectives

Sarcopenia is postulated to be an influential factor in chronic low back pain. The aim of this study is to evaluate the relationship between traditional clinical measures of sarcopenia and novel radiographic methods which evaluate overall muscle status, such as adjusted psoas cross-sectional area (APCSA) and degree of fat infiltration (%FI) in paraspinal muscles, in patients with chronic low back pain.

Methods

Prospective study performed at our institution from 01/01/19-01/04/19. Inclusion criteria were patients ≥65 years old not requiring surgical intervention presenting to a low back pain assessment clinic.

Results

25 patients were identified (mean age: 73 years, 62% male). On spearman's analyses, %FI shared a significant relationship with hand grip strength (r = -0.37; p=0.03), chair rise (r=0.38; p=0.03), SC (r=0.64; p<0.01), and visual analogue scale scores (r=-0.14; p=0.02). Comparably, a statistically significant correlation was evident between APCSA and %FI (r=-0.40; p=0.02) on analysis.

Conclusion

The results of our study demonstrate a statistically significant relationship between APCSA and %FI in the multifidus and erector spinae muscles. Further significant associations of relatability were depicted with traditional clinical measures of sarcopenia. Thus, %FI may be a supplemental indicator of the sarcopenic status of patients presenting with chronic low back pain.

A Systematic Review of Risk Factors Associated With Distal Junctional Failure in Adult Spinal Deformity Surgery

BACKGROUND

The surgical management of adult spinal deformity (ASD) is a major surgical undertaking associated with considerable perioperative risk and a substantial complication profile. Although the natural history and risk factors associated with proximal junctional kyphosis (PJK) and proximal junctional failure are widely reported, distal junctional failure (DJF) is less well understood.

STUDY DESIGN

A systematic review was carried out.

OBJECTIVES

The primary objective is to identify the risk factors associated with DJF. The secondary objective is to delineate the incidence rate and causative factors associated with DJF.

METHODS

A systematic review of articles in Medline/PubMed and The Cochrane Library databases was performed according to preferred reporting items for systematic reviews and meta-analyses guidelines. Data was collated to determine the prevalence of DJF and overall revision rates, and identify potential risk factors for development of DJF.

RESULTS

Twelve studies were included for systematic review. There were 81/2261 (3.6%) cases of DJF. Overall, DJF represented 27.3% of all revision surgeries. Anterior-posterior surgery had a reduced incidence of postoperative DJF [5.0% vs. 8.7%; P=0.08; relative risk (RR)=1.73], as did patients below 60 years of age at the time of surgery (2.9% vs. 3.9%; P=0.09; RR=1.34). There was a higher incidence of DJF among those patients who received interbody fusion (9.9% vs. 5.1%; P=0.06; RR=1.93) compared with those who did not. However, none of these findings reached statistical significance. There were significantly more rates of DJF for fusions ending on L5 compared with constructs fused to the sacrum (11.7% vs. 3.6%; P=0.02; RR=3.28).

CONCLUSIONS

Cohorts 60 years and above of age at the time of surgery and patients managed with posterior-only fusion or interbody fusion have increased incidences of DJF. Fusion to L5 instead of the sacrum significantly influences DJF rates. However, the quality of available evidence is low and further high-quality studies are required to more robustly analyze the clinical, radiographic, and surgical risk factors associated with the development of DJF after ASD surgery.

A meta-analysis of the diagnostic accuracy of Hounsfield units on computed topography relative to dual-energy X-ray absorptiometry for the diagnosis of osteoporosis in the spine surgery population

BACKGROUND

The preoperative identification of osteoporosis in the spine surgery population is of crucial importance. Limitations associated with dual-energy x-ray absorptiometry, such as access and reliability, have prompted the search for alternative methods to diagnose osteoporosis. The Hounsfield Unit(HU), a readily available measure on computed tomography, has garnered considerable attention in recent years as a potential diagnostic tool for reduced bone mineral density. However, the optimal threshold settings for diagnosing osteoporosis have yet to be determined.

METHODS

We selected studies that included comparison of the HU(index test) with dual-energy x-ray absorptiometry evaluation(reference test). Data quality was assessed using the standardised QUADAS-2 criteria. Studies were characterised into 3 categories, based on the threshold of the index test used with the goal of obtaining a high sensitivity, high specificity or balanced sensitivity-specificity test.

RESULTS

9 studies were eligible for meta-analysis. In the high specificity group, the pooled sensitivity was 0.652 (95% CI 0.526 - 0.760), specificity 0.795 (95% CI 0.711 - 0.859) and diagnostic odds ratio was 6.652 (95% CI 4.367 - 10.133). In the high sensitivity group, the overall pooled sensitivity was 0.912 (95% CI 0.718 - 0.977), specificity was 0.67 (0.57 - 0.75) and diagnostic odds ratio was 19.424 (5.446 - 69.275). In the balanced sensitivity-specificity group, the overall pooled sensitivity was 0.625 (95% CI 0.504 - 0.732), specificity was 0.914 (0.823 - 0.960) and diagnostic odds ratio was 14.880 (7.521 - 29.440). Considerable heterogeneity existed throughout the analysis.

CONCLUSION

In conclusion, the HU is a clinically useful tool to aide in the diagnosis of osteoporosis. However, the heterogeneity seen in this study warrants caution in the interpretation of results. We have demonstrated the impact of differing HU threshold values on the diagnostic ability of this test. We would propose a threshold of 135 HU to diagnose OP. Future work would investigate the optimal HU cut-off to differentiate normal from low bone mineral density.

Changing Demographic Trends in spine trauma: The presentation and outcome of Major Spine Trauma in the elderly

INTRODUCTION

Major trauma has seen a demographic shift in recent years and it is expected that the elderly population will comprise a greater burden on the major trauma service in the near future. However, whether a similar trend exists in those undergoing operative intervention for spinal trauma remains to be elucidated.

AIMS

To compare the presentation and outcomes of patients ≥65 years of age sustaining spine trauma to those <65 years at a national tertiary referral spine centre.

METHODS

The local Trauma Audit Research Network (TARN) database was analysed to identify spinal patients referred to our institution, a national tertiary referral centre, between 01/2016 and 05/2019. Patients were divided into a young cohort (16-64 years old) and an elderly cohort (> 64 years old). No explicit distinction was made between major and minor spine trauma cases. Variables analysed included patient demographics, injury severity, mortality, interventions, mechanism of injury and length of hospital stay.

RESULTS

A total of 669 patients were admitted of which 480 patients underwent operative intervention for spinal trauma. Within the elderly cohort, this represented 75.3% of cases. Among the younger population, road traffic collisions were the most common mechanism of injury (37.1%), while low falls (<2 m) (57.4%) were the most common mechanism among the older population. Patients ≥65 years old had significantly longer length of stay (21 days [1-194] v 14 days [1-183]) and suffered higher 30-day mortality rates (4.6% [0-12] v 0.97% [0-4]).

CONCLUSION

Orthopaedic spinal trauma in older people is associated with a significantly higher mortality rate as well as a longer duration of hospitalization. Even though severity of injury is similar for both young and old patients, the mechanism of injury for the older population is of typically much lower energy compared to the high energy trauma affecting younger patients.

The diagnostic and prognostic value of artificial intelligence and artificial neural networks in spinal surgery : a narrative review

In recent years, machine learning (ML) and artificial neural networks (ANNs), a particular subset of ML, have been adopted by various areas of healthcare. A number of diagnostic and prognostic algorithms have been designed and implemented across a range of orthopaedic sub-specialties to date, with many positive results. However, the methodology of many of these studies is flawed, and few compare the use of ML with the current approach in clinical practice. Spinal surgery has advanced rapidly over the past three decades, particularly in the areas of implant technology, advanced surgical techniques, biologics, and enhanced recovery protocols. It is therefore regarded an innovative field. Inevitably, spinal surgeons will wish to incorporate ML into their practice should models prove effective in diagnostic or prognostic terms. The purpose of this article is to review published studies that describe the application of neural networks to spinal surgery and which actively compare ANN models to contemporary clinical standards allowing evaluation of their efficacy, accuracy, and relatability. It also explores some of the limitations of the technology, which act to constrain the widespread adoption of neural networks for diagnostic and prognostic use in spinal care. Finally, it describes the necessary considerations should institutions wish to incorporate ANNs into their practices. In doing so, the aim of this review is to provide a practical approach for spinal surgeons to understand the relevant aspects of neural networks. Cite this article: Bone Joint J 2021;103-B(9):1442-1448.

Methods to Mitigate Industry Influence in Industry Sponsored Research

Medical and surgical research has always had a long-standing relationship with industry-based funding from sources, such as drug and device companies. Concerns exist surrounding the association between funding sources, outcome from studies and publication bias. Studies demonstrating increased odds ratios associated with positive results in industry sponsored studies across medicine have stimulated Cochrane reviews, literature reviews and other articles to examine this relationship further. In spine surgery in particular, studies with positive results have an odds ratio of 3.3 of being published. This article discusses the biases associated with industry sponsorship, possible ways to reduce such biases and ways to improve transparency in research relationships. This article explores the types of bias that can be encountered at different stages of research including previous trials in spine surgery. The means of improving transparency including the Physician Payment Sunshine Act of 2010 and International Committee of Medical Journal Editors (ICJME) accreditation are discussed. We recognize that physicians undertaking industry sponsored research should be protected and not be liable to perverse incentives. We conclude that mitigating bias in industry sponsored research is a multistep process and needs a multifaceted approach. The main beneficiary of research should be patients and as such a collective effort from medical professionals, health care institutions, journals and industry should approach research, and publications with that in mind.

Two-stage anterior and posterior fusion versus one-stage posterior fusion in patients with Scheuermann's kyphosis

AIMS

Whether a combined anteroposterior fusion or a posterior-only fusion is more effective in the management of patients with Scheuermann's kyphosis remains controversial. The aim of this study was to compare the radiological and clinical outcomes of these surgical approaches, and to evaluate the postoperative complications with the hypothesis that proximal junctional kyphosis would be more common in one-stage posterior-only fusion.

METHODS

A retrospective review of patients treated surgically for Scheuermann's kyphosis between 2006 and 2014 was performed. A total of 62 patients were identified, with 31 in each group. Parameters were compared to evaluate postoperative outcomes using chi-squared tests, independent-samples t-tests, and z-tests of proportions analyses where applicable.

RESULTS

There were six postoperative infections in the two-stage anteroposterior group compared with three in the one-stage posterior-only group. A total of four patients in the anteroposterior group required revision surgery, compared with six in the posterior-only group. There was a significantly higher incidence of junctional failure associated with the one-stage posterior-only approach (12.9% vs 0%, p = 0.036). Proximal junction kyphosis (anteroposterior fusion (74.2%) vs posterior-only fusion (77.4%); p = 0.382) and distal junctional kyphosis (anteroposterior fusion (25.8%) vs posterior-only fusion (19.3%), p = 0.271) are common postoperative complications following both surgical approaches.

CONCLUSION

A two-stage anteroposterior fusion was associated with a significantly greater correction of the kyphosis compared with a one-stage posterior-only fusion, with a reduced incidence of junctional failure (0 vs 3). There was a notably greater incidence of infection with two-stage anteroposterior fusion; however, all were medically managed. More patients in the posterior-only group required revision surgery. Cite this article: Bone Joint J 2020;102-B(10):1368-1374.

Validating the GTP-cyclohydrolase 1-feedback regulatory complex as a therapeutic target using biophysical and in vivo approaches

BACKGROUND AND PURPOSE

6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4 ) is an essential cofactor for nitric oxide biosynthesis. Substantial clinical evidence indicates that intravenous BH4 restores vascular function in patients. Unfortunately, oral BH4 has limited efficacy. Therefore, orally bioavailable pharmacological activators of endogenous BH4 biosynthesis hold significant therapeutic potential. GTP-cyclohydrolase 1 (GCH1), the rate limiting enzyme in BH4 synthesis, forms a protein complex with GCH1 feedback regulatory protein (GFRP). This complex is subject to allosteric feed-forward activation by L-phenylalanine (L-phe). We investigated the effects of L-phe on the biophysical interactions of GCH1 and GFRP and its potential to alter BH4 levels in vivo.

EXPERIMENTAL APPROACH

Detailed characterization of GCH1-GFRP protein-protein interactions were performed using surface plasmon resonance (SPR) with or without L-phe. Effects on systemic and vascular BH4 biosynthesis in vivo were investigated following L-phe treatment (100 mg·kg(-1) , p.o.).

KEY RESULTS

GCH1 and GFRP proteins interacted in the absence of known ligands or substrate but the presence of L-phe doubled maximal binding and enhanced binding affinity eightfold. Furthermore, the complex displayed very slow association and dissociation rates. In vivo, L-phe challenge induced a sustained elevation of aortic BH4 , an effect absent in GCH1(fl/fl)-Tie2Cre mice.

CONCLUSIONS AND IMPLICATIONS

Biophysical data indicate that GCH1 and GFRP are constitutively bound. In vivo, data demonstrated that L-phe elevated vascular BH4 in an endothelial GCH1 dependent manner. Pharmacological agents which mimic the allosteric effects of L-phe on the GCH1-GFRP complex have the potential to elevate endothelial BH4 biosynthesis for numerous cardiovascular disorders.

Surface plasmon resonance: towards an understanding of the mechanisms of biological molecular recognition

With the introduction of new instruments and improved sensor chip chemistries, surface plasmon resonance (SPR) is finding new applications for molecular interaction studies. Easy access to high-quality kinetic and thermodynamic data for macromolecular binding events is providing insights into the fundamental mechanisms of molecular recognition. Progress is being made to allow larger-scale interaction studies. In addition, combining SPR with other analytical methods is enabling SPR-based analysis of interaction proteomics.

The structure of the IgE Cepsilon2 domain and its role in stabilizing the complex with its high-affinity receptor FcepsilonRIalpha

The stability of the complex between IgE and its high-affinity receptor, FcepsilonRI, on mast cells is a critical factor in the allergic response. The long half-life of the complex of IgE bound to this receptor in situ ( approximately 2 weeks, compared with only hours for the comparable IgG complex) contributes to the permanent sensitization of these cells and, hence, to the immediate response to allergens. Here we show that the second constant domain of IgE, Cepsilon2, which takes the place of the flexible hinge in IgG, contributes to this long half-life. When the Cepsilon2 domain is deleted from the IgE Fc fragment, leaving only the Cepsilon3 and Cepsilon4 domains (Cepsilon3-4 fragment), the rate of dissociation from the receptor is increased by greater than 1 order of magnitude. We report the structure of the Cepsilon2 domain by heteronuclear NMR spectroscopy and show by chemical shift perturbation that it interacts with FcepsilonRIalpha. By sedimentation equilibrium we show that the Cepsilon2 domain binds to the Cepsilon3-4 fragment of IgE. These interactions of Cepsilon2 with both FcepsilonRIalpha and Cepsilon3-4 provide a structural explanation for the exceptionally slow dissociation of the IgE-FcepsilonRIalpha complex.

Specificity and binding kinetics of murine lupus anti-DNA monoclonal antibodies implicate different stimuli for their production

The origin and relative biological importance of the many different DNA-reactive antibodies that appear in systemic lupus erythematosus are not well understood. A detailed analysis of their fine specificity and binding characteristics with DNA is a necessary step in understanding their biology. We have examined here two monoclonal antibodies (mAb) IV-228 and V-88 that are, respectively, characteristic of antibodies, which bind exclusively to single-stranded (ss) DNA and to both double-stranded (ds) DNA and ssDNA. By surface plasmon resonance (SPR) on BIAcore, we characterized the kinetics of binding of each antibody to synthetic ss and ds oligonucleotides. Antibody V-88 and IV-228 showed different patterns of reactivity for both ss and ds oligonucleotides, characterized by distinctly different kinetic parameters. Analysis of their binding kinetics indicates the importance of base composition in defining DNA epitopes, and shows that some epitopes, such as that recognized by mAb V-88, are expressed on dsDNA and ssDNA, whereas others, as recognized by IV-228, are not. The base preferences of V-88 for ds GC-rich structures over AT-rich, and of IV-228 for ss T-rich structures, also reveal distinct differences between these antibodies. We conclude that the different binding properties of the antibodies will relate to their biological activities. The base preferences of the antibodies suggest that they might be induced by different immunological stimuli, such as those that could be provided by the various DNA fragments and structures released during programmed cell death.

Conformation of the isolated cepsilon3 domain of IgE and its complex with the high-affinity receptor, FcepsilonRI

Immunoglobulin E (IgE) exhibits a uniquely high affinity for its receptor, FcepsilonRI, on the surface of mast cells and basophils. Previous work has implicated the third domain of the constant region of the epsilon-heavy chain (Cepsilon3) in binding to FcepsilonRI, but the smallest fragment of IgE that is known to bind with full affinity is a covalent dimer of the Cepsilon3 and Cepsilon4 domains. We have expressed the isolated Cepsilon3 in Escherichia coli, measured its affinity for FcepsilonRI, and examined its conformation alone and in the complex with FcepsilonRI. Sedimentation equilibrium in the analytical centrifuge reveals that this product is a monomer. The kinetics of binding to an immobilized fragment of the FcepsilonRI alpha-chain, measured by surface plasmon resonance, yields an affinity constant K(a) = 5 x 10(6) M(-)(1), as compared with 4 x 10(9) M(-)(1) for IgE. The circular dichroism spectrum and measurements of fluorescence as a function of the concentration of a denaturant do not reveal any recognizable secondary structure or hydrophobic core. On binding to the FcepsilonRI alpha-chain fragment, there is no change in the circular dichroism spectrum, indicating that the conformation of Cepsilon3 is unchanged in the complex. Thus the isolated Cepsilon3 domain is sufficient for binding to FcepsilonRI, but with lower affinity than IgE. This may be due to the loss of its native immunoglobulin domain structure or to the requirement for two Cepsilon3 domains to constitute the complete binding site for FcepsilonRI or to a combination of these factors.

Cross-reactivity of antiidiotypic antibodies with DNA in systemic lupus erythematosus

OBJECTIVE

To assess the functional relationship between antibodies reactive with DNA and antibodies reactive with the idiotypes (idiopeptides) of anti-DNA antibodies that are associated with systemic lupus erythematosus (SLE) in mice.

METHODS

Antiidiotypic antibodies that appeared spontaneously in lupus mice, and others that were induced by immunization of normal, non-lupus mice, were analyzed for their reactivity by a range of direct binding, competition enzyme-linked immunosorbent assay (ELISA), and surface plasmon resonance (SPR) methods. Their reactions were assessed against synthetic peptides representing sequences of the V(H) region of anti-DNA monoclonal antibody (mAb) V-88, against the native mAb itself, and against mammalian DNA.

RESULTS

In lupus mice, only sera with the highest reactivity against double-stranded DNA (dsDNA) also reacted with idiopeptides in ELISA, and this showed a strong statistical correlation. However, there was no significant relationship between antiidiotypic antibodies and anti-single-stranded DNA antibodies. Immunization of (BALB/c x NZW)F1 mice with idiopeptides p64 (V(H) residues 64-80) or p92 (V(H) residues 92-105) induced antibodies that reacted not only against the respective peptides, but also against the native parent anti-DNA mAb V-88. Furthermore, the immune antiidiopeptide antibodies cross-reacted with dsDNA. Competition SPR experiments with the BIAcore system supported this observation. The binding reaction of V(H) peptide p64 (representing the CDR-H2/FR-H3 region of V-88) with antiidiopeptide antibodies was inhibited by dsDNA.

CONCLUSION

This study identified a unique set of autoantibodies in SLE. They react with both autoantibody idiotopes and with dsDNA, thus having a dual specificity for 2 autoantigens. Because these antiidiotope antibodies arise naturally during the development of lupus disease, and because they bind also to dsDNA, this provides a mechanism whereby the production of anti-dsDNA antibodies is stimulated. These idiotopes on autoantibodies in lupus act as natural mimotopes for inducing anti-dsDNA antibodies, which, due to their dual specificity, may significantly contribute to the pathology of nephritis in SLE.

Solution structure of the proapoptotic molecule BID: a structural basis for apoptotic agonists and antagonists

Members of the BCL2 family of proteins are key regulators of programmed cell death, acting either as apoptotic agonists or antagonists. Here we describe the solution structure of BID, presenting the structure of a proapoptotic BCL2 family member. An analysis of sequence/structure of BCL2 family members allows us to define a structural superfamily, which has implications for general mechanisms for regulating proapoptotic activity. It appears two criteria must be met for proapoptotic function within the BCL2 family: targeting of molecules to intracellular membranes, and exposure of the BH3 death domain. BID's activity is regulated by a Caspase 8-mediated cleavage event, exposing the BH3 domain and significantly changing the surface charge and hydrophobicity, resulting in a change of cellular localization.

Solution structure and dynamics of the bioactive retroviral M domain from Rous sarcoma virus

A biologically active construct of the retroviral M domain from the avian Rous sarcoma virus is defined and its solution structure described. This M domain is fully active in budding and infectivity without myristylation. In spite of a sequence homology level that suggests no relationship among M domains and the family of matrix proteins in mammalian retroviruses, the conserved structural elements of a central core allow an M domain sequence motif to be described for all retroviruses. The surface of the M domain has a highly clustered positive patch comprised of sequentially distant residues. An analysis of the backbone dynamics, incorporating rotational anisotropy, is used to estimate the thermodynamics of proposed domain oligomerization.

Identification of contact residues in the IgE binding site of human FcepsilonRIalpha

The high-affinity receptor for immunoglobulin E (IgE), FcepsilonRI, is an alphabetagamma2 tetramer found on mast cells, basophils, and several other types of immune effector cells. The interaction of IgE with the alpha-subunit of FcepsilonRI is central to the pathogenesis of allergy. Detailed knowledge of the mode of interaction of FcepsilonRI with IgE may facilitate the development of inhibitors for general use in the treatment of allergic disease. To this end we have performed site-directed mutagenesis on a soluble form of the FcepsilonRI alpha-chain (sFcepsilonRIalpha). The effects of four mutations in the second immunoglobulin-like domain of sFcepsilonRIalpha upon the kinetics of binding to IgE and fragments of IgE have been analyzed using surface plasmon resonance. As described in the preceding paper of this issue [Henry, A. J., et al. (1997) Biochemistry 36, 15568-15578], biphasic binding kinetics was observed. Two of the mutations had significant effects on binding: K117D reduced the affinity of sFcepsilonRIalpha for IgE by a factor of 30, while D159K increased the affinity for IgE by a factor of 7, both principally through changes in the rates of dissociation of the slower phase of the interaction. Circular dichroism spectra of sFcepsilonRIalpha incorporating either of these mutations were indistinguishable from those of wild-type sFcepsilonRIalpha, demonstrating that the native conformation had not been disrupted. Our results, together with those from site-directed mutagenesis on fragments of IgE presented in the accompanying paper, define the contact surfaces in the IgE:sFcepsilonRIalpha complex.

Participation of the N-terminal region of Cepsilon3 in the binding of human IgE to its high-affinity receptor FcepsilonRI

The binding of immunoglobulin E (IgE) to its high-affinity receptor (FcepsilonRI) expressed on mast cells and basophils is central to the development of an allergic reaction. Previous studies have implicated the third constant domain of IgE-Fc (Cepsilon3) as the site of the interaction with FcepsilonRI. We have prepared a series of site-directed mutants of human IgE-Fc, particularly focusing on the N-terminal "linker" region and AB loop of Cepsilon3. The kinetics of binding IgE and its Fc fragments to the immobilized receptor were determined by surface plasmon resonance (SPR), and two phases of binding were observed. We identified one mutation in the N-terminal linker region, R334S, that has a dramatic effect on binding. R334S lowers the affinity of IgE-Fc for FcepsilonRI by 120-fold, principally through an increase in the dissociation rate of the slower phase of the interaction. This mutation has a similar effect in Fcepsilon3-4, a truncated form of IgE-Fc which lacks the Cepsilon2 domain pair, and thus it does not exert its effect through altering the quaternary structure of IgE-Fc, firmly implicating Arg334 as a contact residue in the complex. However R334S has no effect on the binding of FcepsilonRII (CD23), the low-affinity receptor for IgE, demonstrating the structural integrity of the mutated IgE-Fc. Circular dichroism spectroscopy and thermal stability studies further indicate that the R334S mutation does not disorder or destabilize the structure of IgE-Fc or Fcepsilon3-4. These results demonstrate the importance of the N-terminal linker region of Cepsilon3 in the interaction of IgE with FcepsilonRI.

Peptide analogs that inhibit IgE-Fc epsilon RI alpha interactions ameliorate the development of lethal graft-versus-host disease

Significant increases in serum levels of IgE have often been observed in allogeneic bone marrow transplantation patients and have generally been thought to be diagnostic of graft-versus-host disease (GVHD), rather than an agent involved in the pathogenesis of the disease. Experimental murine GVHD models have also indicated associations of hyper-IgE activity, yet the role of IgE in GVHD pathogenesis has never been tested directly. In the current study, we have tried to address this issue by using recently developed peptide analog antagonists for the interaction of IgE with the Fc epsilon RI receptor, which is necessary for triggering mast cells and other cell types when cross-linked by antigens. A synthetic cyclized 13-amino acid peptide was previously designed from the modeled C-C' loop region of the Fc epsilon RI alpha-chain and was found to act as a competitive inhibitor of IgE-Fc epsilon RI alpha binding. The peptide was generated in two forms, a cyclic L-(L-IgEtide) and retro D-amino acid composition (rDIgEtide), the latter to increase resistance to protease degradation for in vivo applications. These two inhibitor peptides were then used to test the hypothesis that IgE could be involved in the pathogenesis of acute GVHD, in the B10.D2-->DBA/2 (900 cGy) strain combination, with GVHD directed to minor histocompatibility antigens. Both peptides demonstrated significant inhibition of the development of lethal GVHD, supporting the involvement of IgE at some level of disease pathogenesis.

Structure based design and characterization of peptides that inhibit IgE binding to its high-affinity receptor

We have designed synthetic peptide inhibitors of the interaction between IgE and its high affinity receptor, Fc epsilon RI. The structure of the second domain of CD2 was used as a modelling template for the second alpha-chain domain of Fc epsilon RI, the C-C' loop of which has been implicated in the interaction with IgE. An L-amino acid peptide and a retro-enantiomeric D-amino acid peptide were designed to mimic the conformation of the C-C' region. Both peptides were cyclized by disulphide bond formation between terminal cysteine residues, and show mirror image symmetry by circular dichroism analysis. The C-C' peptide mimics act as competitive inhibitors of IgE binding. The cyclic L- and retro D-peptides exhibited KDs of approximately 3 microM and 11 microM, respectively, for IgE. Further, the peptides inhibit IgE-mediated mast cell degranulation, an in vitro model of an allergic response.

Calreticulin binding affinity for glycosylated laminin

Several lines of evidence indicate that calreticulin has lectin-like properties. As a molecular chaperone, calreticulin binds preferentially to nascent glycoproteins via their immature carbohydrates; this property closely resembles that seen for calnexin, a chaperone with extensive molecular identity to calreticulin. A cell surface form of calreticulin also exhibits lectin-like properties, binding specific oligomannosides including those covalently linked to laminin. In the present study we examined the interaction between calreticulin and laminin by means of surface plasmon resonance. The results show that calreticulin specifically binds to glycosylated laminin but fails to specifically bind tunicamycin-derived unglycosylated laminin or bovine serum albumin. Calreticulin binding to glycosylated laminin requires calcium and is abolished in the presence of EDTA. Scatchard analysis of binding yields an apparent association constant, Ka, of 2.1 +/- 0.9 x 10(6) m-1 while kinetic analysis yields an estimate of the association on rate, (Kassoc), as 2 x 10(5) m-1 s-1. The composite results support calreticulin's lectin-like properties as well as its proposed role in laminin recognition, both in the cell interior and on the cell surface.

Histopathologic changes following irradiation for uveal tract melanoma

Histopathologic studies were performed on 38 eyes in patients with uveal melanoma who had enucleation. Of the 38 eyes examined, enucleation was required in 11 (29%) following episcleral radioactive plaque therapy (RPT), which was performed in 83 patients. The reasons for enucleation in the 11 patients who had RPT were progressive tumor in 5 and treatment complications in 6 eyes. The histologic findings in these 11 patients were compared to those seen in 7 patients (18%) who received a planned course of preoperative external beam radiotherapy (RT) prior to enucleation and with 20 uveal melanoma patients (53%) who were treated with enucleation alone. Tumor necrosis was found in the eyes of patients from all three groups examined. It was, however, seen more frequently and to a greater extent in the 11 RPT patients as compared to the 7 preoperative RT and 20 enucleation alone patients, p = .01. There was no difference in the incidence or extent of tumor necrosis in the 7 preoperative RT patients as compared to the 20 primary enucleation patients, p = .18. In all 3 study groups, no correlation was found between tumor size and necrosis. In the 11 RPT patients, necrosis was independent of cell type and the radiation dose. As expected, the RPT patients had a greater incidence of neovascularization on the iris and scleral necrosis than those of the other two study groups (70 vs. 12.5% and 33 vs 0%, respectively), p = .004. A major effort needs to be made to optimize episcleral RPT in order to reduce treatment complications and increase the incidence of primary tumor control.

A rationally designed CD4 analogue inhibits experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is an acute inflammatory autoimmune disease of the central nervous system that can be elicited in rodents and is the major animal model for the study of multiple sclerosis (MS). The pathogenesis of both EAE and MS directly involves the CD4+ helper T-cell subset. Anti-CD4 monoclonal antibodies inhibit the development of EAE in rodents, and are currently being used in human clinical trials for MS. We report here that similar therapeutic effects can be achieved in mice using a small (rationally designed) synthetic analogue of the CD4 protein surface. It greatly inhibits both clinical incidence and severity of EAE with a single injection, but does so without depletion of the CD4+ subset and without the inherent immunogenicity of antibody. Furthermore, this analogue is capable of exerting its effects on disease even after the onset of symptoms.

Keratitis as a complication of bilateral, simultaneous radial keratotomy

During a one-month period, we examined four patients referred for evaluation of probable microbial keratitis after bilateral, simultaneous radial keratotomy. Each patient had midstromal infiltrates compatible with microbial keratitis that involved one or more of the radial incisions. In two patients the keratitis was bilateral. All patients had been treated empirically with antibiotic agents; superficial cultures with cotton-tipped applicators and corneal scraping by inserting a platinum spatula into the radial incisions were negative. Corneal biopsy of one patient disclosed gram-positive rods and culture of the biopsy specimen grew diphtheroids. The infiltrates gradually resolved over a period of several months with intensive antibiotic therapy. Sight-threatening infectious keratitis can occur after radial keratotomy, and we believe that simultaneous bilateral ocular surgery of any kind should be discouraged.

Keratocyte loss after corneal deepithelialization in primates and rabbits

PURPOSE

To evaluate the response of stromal keratocytes to central corneal deepithelialization.

METHODS

Rabbits and monkeys underwent unilateral mechanical deepithelialization with a blunt instrument and were killed at intervals ranging from 15 minutes to 24 hours after surgery. Two rabbits underwent unilateral deepithelialization under a fluid bath containing corneal preservation medium. Two rabbits were treated unilaterally with corneal preservation medium topically applied every 15 minutes for 16 hours after epithelial removal. Four rabbits underwent linear keratotomy immediately after deepithelialization of the cornea or on normal unoperated corneas and were killed 1 day (two animals) and 14 days (two animals) after surgery.

RESULTS

Deepithelialization resulted in severe ultrastructural changes in keratocytes within 30 minutes after surgery. After 24 hours, the number of keratocytes in the anterior stroma underneath the deepithelialized area had decreased significantly in rabbits (P = .0001) and in monkeys (P = .0007) compared with controls. The wound healing was altered and delayed when the epithelium was not present after keratotomy. The use of storage media during and after deepithelialization minimized the early keratocyte changes and appeared to stimulate reepithelialization.

CONCLUSIONS

Removal of corneal epithelium causes loss of superficial stromal keratocytes in rabbits and monkeys. Keratocyte death may results from osmotic changes that alter the corneal wound healing response.

Holmium laser thermokeratoplasty

PURPOSE

Corneal curvature can be altered by shrinking stromal collagen with a pulsed solid-state holmium: YAG laser in a procedure termed laser thermokeratoplasty.

METHODS

The authors performed laser thermokeratoplasty in 40 human cadaver eyes using a ring pattern of 32 spots, each spot having a diameter of 300 microns.

RESULTS

The amount of induced corneal steepening decreased as ring diameter was increased in 1 mm increments, with 22.2 +/- 3.3 and 3.7 +/- 2.0 diopters (D) of central steepening with diameters of 3 and 7 mm, respectively. Results of histologic examination showed a cone-shaped zone of increased stromal hematoxylin uptake extending posteriorly for 90% of stromal thickness. Energy levels greater than those needed to induce topographic changes produced limited endothelial injury in rabbit corneas and, in some cases, intraocular inflammation. A computerized, finite element model of the globe demonstrated central corneal steepening as a result of heat-induced stromal contraction to a depth of 75% corneal thickness.

CONCLUSIONS

These data support previous studies indicating that central corneal topography can be modified by heating corneal stroma in a controlled fashion with the mid-infrared holmium:YAG laser.

Direct involvement of the CDR3-like domain of CD4 in T helper cell activation

The CD4 glycoprotein, a member of the Ig super-family, has long been known to play an important role in the immunologic activation of Th cells. The precise manner in which CD4 participates in this activation process is not yet understood. In an attempt to further define its role in Th cell activation, we modeled the D1 domain of the murine CD4 protein (L3T4) based on the experimentally determined high resolution structure of the human CD4 protein. Because the D1 domain of CD4 strongly resembles the V kappa chain of an antibody, we addressed the question of whether the CDR-like regions of CD4 are also involved in mediating protein-protein interactions. Consequently, we used the modeled L3T4 structure as a template in the design of conformational mimics of the CDR3-like region (residues 86-94). Only the analog designed to mimic both the sequence and conformation of this region exhibited highly specific inhibition of CD4-dependent responses. Because the inhibitory activity could be localized to the Th cell itself, it appears that this analog acts by uncoupling a CD4 association (independent of an APC) critical to generating a proliferative response.

Direct involvement of the CDR3-like domain of CD4 in T helper cell activation

The CD4 glycoprotein, a member of the Ig super-family, has long been known to play an important role in the immunologic activation of Th cells. The precise manner in which CD4 participates in this activation process is not yet understood. In an attempt to further define its role in Th cell activation, we modeled the D1 domain of the murine CD4 protein (L3T4) based on the experimentally determined high resolution structure of the human CD4 protein. Because the D1 domain of CD4 strongly resembles the V kappa chain of an antibody, we addressed the question of whether the CDR-like regions of CD4 are also involved in mediating protein-protein interactions. Consequently, we used the modeled L3T4 structure as a template in the design of conformational mimics of the CDR3-like region (residues 86-94). Only the analog designed to mimic both the sequence and conformation of this region exhibited highly specific inhibition of CD4-dependent responses. Because the inhibitory activity could be localized to the Th cell itself, it appears that this analog acts by uncoupling a CD4 association (independent of an APC) critical to generating a proliferative response.

Infectious crystalline keratopathy with ring opacity

A 41-year-old physician was treated for 3 months with antiviral medications, antibiotics, and steroids for presumed herpetic keratitis. When seen by us, an annular infiltrate was observed, along with crystalline-like opacities in the superficial one third of the stroma. Cultures of scrapings and of subsequent biopsies were positive for Streptococcus mitis of the viridans group; histopathology demonstrated large aggregates of cocci between the stroma lamellae. Tapering of topical corticosteroids and treatment with topical penicillin resulted in resolution of the infiltrates. The clinical appearance and findings in this patient suggest that infectious crystalline keratitis can produce an annular infiltrate. Injection of the organism into rabbit corneas produced a crystalline infiltrate, but no annular opacity was observed. Corticosteroids altered the clinical and histopathologic appearance of the lesions in rabbits.

Unsuccessful excimer laser phototherapeutic keratectomy. Clinicopathologic correlation

A 46-year-old man underwent phototherapeutic keratectomy with a 193-nm excimer laser in an attempt to remove a superficial corneal scar that had been present for 36 years. The scar proved to be resistant to ablation with the laser, while relatively normal stroma was easily ablated. Histopathologic examination of the corneal button removed 3 months after excimer laser surgery revealed absence of Bowman's membrane in the area of ablation, superficial stromal disorganization and scarring, raised nodules of collagenous tissue extending into the epithelium, and no calcification within the lesion. Ultrastructural examination was remarkable for irregularly oriented collagen fibers within the scar. The resistance of this lesion to excimer laser ablation appears to have been the consequence of marked differences in rates of ablation between normal stroma and the very long-standing scar.

Human papillomavirus DNA in tissues and ocular surface swabs of patients with conjunctival epithelial neoplasia

DNA from human papillomavirus (HPV) type 16 has been recently identified in conjunctival epithelial dysplasia and carcinoma. In other body sites, HPV 16 is thought to play a role in the development of dysplastic lesions. To further explore the relationship between HPV and conjunctival neoplasia, we examined paraffin-embedded tissue samples from 42 biopsies or excisions from 38 patients whose lesions ranged from mild dysplasia to infiltrating squamous carcinoma of the conjunctiva. We also examined limbal swabs from six patients with dysplasia or carcinoma, five of whom also had tissue samples available for study. HPV 16 DNA was present in 37 (88.1%) tissue samples, including duplicate samples from four patients. Five (83.3%) of six patients who had conjunctival swabs had HPV 16 DNA present in the swabs, including two patients whose lesions had been excised one and eight years before swabs were done. We conclude there is a high prevalence of HPV 16 DNA in conjunctival epithelial neoplasia, suggesting that the development of neoplasia is related somehow to the presence of this virus. However, based on its presence in clinically uninvolved eyes and on the persistence of infection many years after successful eradication of the lesions, HPV apparently does not act alone in the development of conjunctival epithelial neoplasia.