Experimental helium-beam radiography with a high-energy beam: Water-equivalent thickness calibration and first image-quality results

PURPOSE

A clinical implementation of ion-beam radiography (iRad) is envisaged to provide a method for on-couch verification of ion-beam treatment plans. The aim of this work is to introduce and evaluate a method for quantitative water-equivalent thickness (WET) measurements for a specific helium-ion imaging system for WETs that are relevant for imaging thicker body parts in the future.

METHODS

Helium-beam radiographs (αRads) are measured at the Heidelberg Ion-beam Therapy Center (HIT) with an initial beam energy of 239.5 MeV/ u. An imaging system based on three pairs of thin silicon pixel detectors is used for ion path reconstruction and measuring the energy deposition (dE) of each particle behind the object to be imaged. The dE behind homogeneous plastic blocks is related to their well-known WETs between 280.6mm and 312.6 mm with a calibration curve that is created by fitting the measured data points. The quality of the quantitative WET measurements is determined by the uncertainty of the measured WET of a single ion (single-ion WET precision) and the deviation of a measured WET value to the well-known WET (WET accuracy). Subsequently, the fitted calibration curve is applied to an energy deposition radiograph of a phantom with a complex geometry. The spatial resolution (modulation transfer function at 10% (MTF_10% )) and WET accuracy (mean absolute percentage difference (MAPD)) of the WET map, are determined.

RESULTS

In the optimal imaging WET-range from ∼  280 mm to 300 mm, the fitted calibration curve reached a mean single-ion WET precision of 1.55 ± 0.00%. Applying the calibration to an ion radiograph (iRad) of a more complex WET distribution, the spatial resolution was determined to be MTF_10% = 0.49 ± 0.03 lp/mm and the WET accuracy was assessed as MAPD to 0.21%.

CONCLUSIONS

Using a beam energy of 239.5MeV/ u and the proposed calibration procedure, quantitative αRads of WETs between ∼  280mm to 300 mm can be measured and show high potential for clinical use. The proposed approach with the resulting image qualities encourages further investigation towards the clinical application of helium-beam radiography. This article is protected by copyright. All rights reserved.

[Case report of an osseous (and lymphogenic) thymic carcinoma in an adult]

A Thymic carcinoma in adults is rare. We present the case of a 47-year-old man, who was treated conservatively for spondylolisthesis L5/S1 in our institution for several years. In the further course, the patient complained about pain exacerbation with acute lower back pain. Cross-sectional scanning showed a tumor of the lumbar vertebral body three. A biopsy of this mass revealed a metastatic thymic carcinoma of the squamous cells. After palliative therapy, the patient died 9 months after initial diagnosis.

Resuming Elective Orthopaedic Surgery During the COVID-19 Pandemic: Guidelines Developed by the International Consensus Group (ICM)

»As we resume elective surgical procedures, it is important to understand what practices and protocols should be altered or implemented in order to minimize the risk of pathogen transfer during the severe acute respiratory syndrome (SARS)-CoV-2 pandemic. »Each hospital and health system should consider their unique situation in terms of SARS-CoV-2 prevalence, staffing capabilities, personal protection equipment supply, and so on when determining how and when to implement these recommendations. »All patients should be screened for SARS-CoV-2 by means of a thorough history and physical examination, as well as reverse transcription-polymerase chain reaction (RT-PCR) testing whenever possible, prior to undergoing elective surgery. »Patients who are currently infected with coronavirus disease 2019 (COVID-19) should not undergo elective surgery. »These guidelines are based on the available scientific evidence, albeit scant. The recommendations have been reviewed and voted on by the expert delegates who produced this document.

[Recurrent infections of the upper aerodigestive tract in patients with primary immunodeficiency]

BACKGROUND

Primary immunodeficiency is a rare disease of humoral and cellular immune defense, which can lead to severe and recurrent infections of different organs. The diagnosis of this disease is often difficult, and its early identification is necessary for adequate treatment and control.

OBJECTIVE

This study aimed to analyze ear, nose, and throat (ENT) infections in adults and children with a primary immunodeficiency. We attempted to characterize possible warning signs that should trigger an immunologic diagnostic workup.

MATERIALS AND METHODS

The current study comprised a retrospective case series of patients with primary immunodeficiencies. The type of immunodeficiency and the number of ENT infections were recorded.

RESULTS

A total of 85 Patients were included in the study. 56 patients (66%) had an acute exacerbation of chronic rhinosinusitis (n = 28), cervical lymphadenitis (n = 16), acute tonsillitis (n = 14), and acute otitis media (n = 6). Reporting detailed information about the frequencies and dates of infections was not possible, due to the retrospective nature of the analysis.

CONCLUSION

The prevalence of ENT infections in patients with a primary immunodeficiency is increased compared to the normal population. For the ENT specialist, these findings underline the necessity of including primary immunodeficiency in the differential diagnosis and initiating targeted diagnostic methods where indicated. Interdisciplinary collaboration with rheumatologists and immunologists is highly recommended, particularly for pediatric patients.

Risk factors for children requiring adenotonsillectomy and their impact on postoperative complications: a retrospective analysis of 2000 patients

Adenotonsillectomies are commonly performed procedures and sleep-disordered breathing is becoming increasingly important as an indication for surgery. Because of the higher risks in patients with obstructive sleep apnoea, the required level of postoperative care for these patients is currently under discussion, and better identification of patients at risk may reduce unnecessary postoperative monitoring. To evaluate the influence of obstructive sleep apnoea, and other risk factors, on peri-operative complications in children requiring adenotonsillectomy, we performed a retrospective case-control study that included 1995 patients treated between January 2009 and June 2017. In our analysis, young age (OR 3.8, 95%CI 2.1-7.1), low body weight (OR 2.6, 95%CI 1.5-4.4), obstructive sleep apnoea (OR 2.4, 95%CI 1.5-3.8), pre-existing craniofacial or syndromal disorders (OR 2.3, 95%CI 1.4-3.8) and adenotonsillectomy, compared with adenoidectomy alone, (OR 7.9, 95%CI 4.7-13.1) were identified as risk factors for complications during or after surgery, p < 0.001. All 13 patients suffering from complications more than 3 h postoperatively had obstructive sleep apnoea plus at least one more of these risk factors. Patients at risk of postoperative complications can therefore be identified by several criteria pre-operatively, and should be monitored postoperatively using pulse oximetry overnight. For all other patients, postoperative observation on a surgical ward without extra monitoring is sufficient. Admission to paediatric intensive care should be reserved for patients suffering serious intra-operative complications.

A centrifuge tube reactor for the determination of bacterial methane oxidation enrichment factors without influence of diffusion related isotope fractionation

Biotransformation of methane at landfill sites can be estimated by applying compound specific stable isotope analysis of methane from the anaerobic and the cover layer surface zone. Next to these two input parameters, merely the knowledge of the carbon isotopic fractionation of the bacterial methane oxidation in terms of the enrichment factor (ε) is required. However, many factors and conditions have been described to affect ε. These include temperature, the applied landfill cover, the type of expressed methane monooxygenase (MMO), and cell density. In this work we investigated the microbial methane oxidation with respect to temperature and type of methanotrophic enrichment culture. A newly designed setup was used to overcome potential CH₄-substrate limitations such as diffusion that could affect the determined values of ε by improper and inhomogeneous mixing. The isotopic fractionation was determined based on the stable carbon isotope analysis of methane and carbon dioxide. The obtained value for isotopic fractionation was ε_22°C = -0.0136 ± 0.0036. Also for the first time, bulk stable isotope analysis of bacterial cell mass was performed by flow injection analysis isotope ratio mass spectrometry.

Diagnostic guidelines for the histological particle algorithm in the periprosthetic neo-synovial tissue

BACKGROUND

The identification of implant wear particles and non-implant related particles and the characterization of the inflammatory responses in the periprosthetic neo-synovial membrane, bone, and the synovial-like interface membrane (SLIM) play an important role for the evaluation of clinical outcome, correlation with radiological and implant retrieval studies, and understanding of the biological pathways contributing to implant failures in joint arthroplasty. The purpose of this study is to present a comprehensive histological particle algorithm (HPA) as a practical guide to particle identification at routine light microscopy examination.

METHODS

The cases used for particle analysis were selected retrospectively from the archives of two institutions and were representative of the implant wear and non-implant related particle spectrum. All particle categories were described according to their size, shape, colour and properties observed at light microscopy, under polarized light, and after histochemical stains when necessary. A unified range of particle size, defined as a measure of length only, is proposed for the wear particles with five classes for polyethylene (PE) particles and four classes for conventional and corrosion metallic particles and ceramic particles.

RESULTS

All implant wear and non-implant related particles were described and illustrated in detail by category. A particle scoring system for the periprosthetic tissue/SLIM is proposed as follows: 1) Wear particle identification at light microscopy with a two-step analysis at low (× 25, × 40, and × 100) and high magnification (× 200 and × 400); 2) Identification of the predominant wear particle type with size determination; 3) The presence of non-implant related endogenous and/or foreign particles. A guide for a comprehensive pathology report is also provided with sections for macroscopic and microscopic description, and diagnosis.

CONCLUSIONS

The HPA should be considered a standard for the histological analysis of periprosthetic neo-synovial membrane, bone, and SLIM. It provides a basic, standardized tool for the identification of implant wear and non-implant related particles at routine light microscopy examination and aims at reducing intra-observer and inter-observer variability to provide a common platform for multicentric implant retrieval/radiological/histological studies and valuable data for the risk assessment of implant performance for regional and national implant registries and government agencies.

Helium ion beam imaging for image guided ion radiotherapy

BACKGROUND

Ion beam radiotherapy provides potential for increased dose conformation to the target volume. To translate it into a clinical advantage, it is necessary to guarantee a precise alignment of the actual internal patient geometry with the treatment beam. This is in particular challenging for inter- and intrafractional variations, including movement. Ion beams have the potential for a high sensitivity imaging of the patient geometry. However, the research on suitable imaging methods is not conclusive yet. Here we summarize the research activities within the "Clinical research group heavy ion therapy" funded by the DFG (KFO214). Our aim was to develop a method for the visualization of a 1 mm thickness difference with a spatial resolution of about 1 mm at clinically applicable doses.

METHODS

We designed and built a dedicated system prototype for ion radiography using exclusively the pixelated semiconductor technology Timepix developed at CERN. Helium ions were chosen as imaging radiation due to their decreased scattering in comparison to protons, and lower damaging potential compared to carbon ions. The data acquisition procedure and a dedicated information processing algorithm were established. The performance of the method was evaluated at the ion beam therapy facility HIT in Germany with geometrical phantoms. The quality of the images was quantified by contrast-to-noise ratio (CNR) and spatial resolution (SR) considering the imaging dose.

RESULTS

Using the unique method for single ion identification, degradation of the images due to the inherent contamination of the outgoing beam with light secondary fragments (hydrogen) was avoided. We demonstrated experimentally that the developed data processing increases the CNR by 350%. Consideration of the measured ion track directions improved the SR by 150%. Compared to proton radiographs at the same dose, helium radiographs exhibited 50% higher SR (0.56 ± 0.04lp/mm vs. 0.37 ± 0.02lp/mm) at a comparable CNR in the middle of the phantom. The clear visualization of the aimed inhomogeneity at a diagnostic dose level demonstrates a resolution of 0.1 g/cm2 or 0.6% in terms of water-equivalent thickness.

CONCLUSIONS

We developed a dedicated method for helium ion radiography, based exclusively on pixelated semiconductor detectors. The achievement of a clinically desired image quality in simple phantoms at diagnostic dose levels was demonstrated experimentally.

Prevention of periprosthetic joint infection: new guidelines

The World Health Organization (WHO) and the Centre for Disease Control and Prevention (CDC) recently published guidelines for the prevention of surgical site infection. The WHO guidelines, if implemented worldwide, could have an immense impact on our practices and those of the CDC have implications for healthcare policy in the United States. Our aim was to review the strategies for prevention of periprosthetic joint infection in light of these and other recent guidelines. Cite this article: Bone Joint J 2017;99-B(4 Supple B):3-10.

Clinically insignificant trunnionosis in large-diameter metal-on-polyethylene total hip arthroplasty

Objectives

Mechanical wear and corrosion at the head-stem junction of total hip arthroplasties (THAs) (trunnionosis) have been implicated in their early revision, most commonly in metal-on-metal (MOM) hips. We can isolate the role of the head-stem junction as the predominant source of metal release by investigating non-MOM hips; this can help to identify clinically significant volumes of material loss and corrosion from these surfaces.

Methods

In this study we examined a series of 94 retrieved metal-on-polyethylene (MOP) hips for evidence of corrosion and material loss at the taper junction using a well published visual grading method and an established roundness-measuring machine protocol. Hips were retrieved from 74 male and 20 female patients with a median age of 57 years (30 to 76) and a median time to revision of 215 months (2 to 324). The reasons for revision were loosening of both the acetabular component and the stem (n = 29), loosening of the acetabular component (n = 58) and infection (n = 7). No adverse tissue reactions were reported by the revision surgeons.

Results

Evidence of corrosion was observed in 55% of hips. The median Goldberg taper corrosion score was 2 (1 to 4) and the annual rate of material loss at the taper was 0.084 mm³/year (0 to 0.239). The median trunnion corrosion score was 1 (1 to 3).

Conclusions

We have reported a level of trunnionosis for MOP hips with large-diameter heads that were revised for reasons other than trunnionosis, and therefore may be clinically insignificant.

Cite this article: H. S. Hothi, D. Kendoff, C. Lausmann, J. Henckel, T. Gehrke, J. Skinner, A. Hart. Clinically insignificant trunnionosis in large-diameter metal-on-polyethylene total hip arthroplasty. Bone Joint Res 2017;6:52–56. DOI: 10.1302/2046-3758.61.BJR-2016-0150.R2.

Effective prevention of recurrent dislocation following primary cemented Endo-MarkIII/SP2 total hip arthroplasty using a posterior lip augmentation device

PURPOSE

This retrospective study was performed to determine the effectiveness of preventing recurrent dislocation following primary cemented Endo-MarkIII/SP2 total hip replacement using a posterior lip augmentation device (PLAD).

METHODS

Between January 2003 and Dezember 2006, 27 PLADs were used in the treatment of recurrent hip dislocation in 27 patients who had received a cemented primary total hip arthroplasty using Endo-MarkIII/SP2 (Waldemar LINK, Hamburg, Germany) components. The mean number of dislocations prior to stabilization with this specific device was 2.6 (range 2-4, SD ± 0.4) with a mean time to revision surgery of 10 months (IQR 13). The mean age of the patients at time of revision surgery was 81.5 years (range 70-94, SD ± 6.9). The control group evaluating the clinical outcome using the Harris Hip Score (HHS) also received a cemented primary total hip arthroplasty using the same implants. A retrospective clinical and radiological review was carried out at a mean follow-up of 68.5 months (range 30-103, SD ± 17.7).

RESULTS

Of the 27 patients, 6 had died at the time of the latest review, with the posterior lip augmentation device still in situ and without reported further dislocation after PLAD application. In 2 of the remaining 21 patients recurrent dislocation occurred, thus a subsequent revision of respective implants had to be performed to achieve persistent joint stability. At latest follow-up no deep infection or implant loosening occurred.

CONCLUSION

Surgical treatment of recurrent dislocation following primary cemented Endo-MarkIII/SP2 total hip replacement using a posterior lip augmentation device is a safe and effective procedure which can lead to a secondary stabilization of the total hip arthroplasty in about 90 % of the patients.

The management of an infected total knee arthroplasty

Periprosthetic joint infection (PJI) is one of the most feared and challenging complications following total knee arthroplasty. We provide a detailed description of our current understanding regarding the management of PJI of the knee, including diagnostic aids, pre-operative planning, surgical treatment, and outcome.

Septic single-stage knee arthrodesis after failed total knee arthroplasty using a cemented coupled nail

Knee arthrodesis is a potential salvage procedure for limb preservation after failure of total knee arthroplasty (TKA) due to infection. In this study, we evaluated the outcome of single-stage knee arthrodesis using an intramedullary cemented coupled nail without bone-on-bone fusion after failed and infected TKA with extensor mechanism deficiency. Between 2002 and 2012, 27 patients (ten female, 17 male; mean age 68.8 years; 52 to 87) were treated with septic single-stage exchange. Mean follow-up duration was 67.1months (24 to 143, n = 27) (minimum follow-up 24 months) and for patients with a minimum follow-up of five years 104.9 (65 to 143,; n = 13). A subjective patient evaluation (Short Form (SF)-36) was obtained, in addition to the Visual Analogue Scale (VAS). The mean VAS score was 1.44 (SD 1.48). At final follow-up, four patients had recurrent infections after arthrodesis (14.8%). Of these, three patients were treated with a one-stage arthrodesis nail exchange; one of the three patients had an aseptic loosening with a third single-stage exchange, and one patient underwent knee amputation for uncontrolled sepsis at 108 months. All patients, including the amputee, indicated that they would choose arthrodesis again. Data indicate that a single-stage knee arthrodesis offers an acceptable salvage procedure after failed and infected TKA.

[The use of tantalum cones for reconstruction of bone defects in revision total knee arthroplasty]

OBJECTIVE

Revision arthroplasty of the knee is often associated with substantial femoral and/or tibial bone loss. Tantalum cones are used to reconstruct these defects and to improve initial stability. This requires an implantation in the "press-fit" technique with maximum contact to the host bone.

INDICATIONS

Tantalum cones may be used in grade 2-3 femoral and/or tibial defects according to the AORI (Anderson Orthopedic Research Institute) classification system.

CONTRAINDICATIONS

There are no contraindications described.

SURGICAL TECHNIQUE

After removal of the implant and cement remnants, bone defects have to be evaluated. A tantalum cone which adequately fills the bone defect is implanted using the "press-fit" technique. If necessary, saving resection of surplus bone to fit the cone properly. Gaps between the cone and the host bone are filled with cancellous bone in "impaction-bone-grafting" technique to increase the area of contact. Fitting the revision knee prosthesis and fixing with the use of bone cement.

POSTOPERATIVE MANAGEMENT

Postoperative physiotherapy is adjusted to the result of the reconstruction. In most cases with stable reconstruction, mobilization with full weight-bearing and the use of two crutches can be performed. Additional bone grafting may require a partial weight-bearing regimen for postoperative mobilization. Physiotherapy to improve range of motion is performed starting on postoperative day 1.

RESULTS

Several studies reported promising midterm results (observation period about 36 months) after implantation of tantalum cones in revision knee arthroplasty. There is consistent evidence for stable osteointegration of the cones. The main intraoperative complication is fracture of the host bone during impaction of the cones.

Synovial C-reactive protein as a marker for chronic periprosthetic infection in total hip arthroplasty

The aim of this study was to assess the role of synovial C-reactive protein (CRP) in the diagnosis of chronic periprosthetic hip infection. We prospectively collected synovial fluid from 89 patients undergoing revision hip arthroplasty and measured synovial CRP, serum CRP, erythrocyte sedimentation rate (ESR), synovial white blood cell (WBC) count and synovial percentages of polymorphonuclear neutrophils (PMN). Patients were classified as septic or aseptic by means of clinical, microbiological, serum and synovial fluid findings. The high viscosity of the synovial fluid precluded the analyses in nine patients permitting the results in 80 patients to be studied. There was a significant difference in synovial CRP levels between the septic (n = 21) and the aseptic (n = 59) cohort. According to the receiver operating characteristic curve, a synovial CRP threshold of 2.5 mg/l had a sensitivity of 95.5% and specificity of 93.3%. The area under the curve was 0.96. Compared with serum CRP and ESR, synovial CRP showed a high diagnostic value. According to these preliminary results, synovial CRP may be a useful parameter in diagnosing chronic periprosthetic hip infection.

Cite this article: Bone Joint J 2015; 97-B:173–6.

The role of hinges in primary total knee replacement

The use of hinged implants in primary total knee replacement (TKR) should be restricted to selected indications and mainly for elderly patients. Potential indications for a rotating hinge or pure hinge implant in primary TKR include: collateral ligament insufficiency, severe varus or valgus deformity (>20°) with necessary relevant soft-tissue release, relevant bone loss including insertions of collateral ligaments, gross flexion-extension gap imbalance, ankylosis, or hyperlaxity. Although data reported in the literature are inconsistent, clinical results depend on implant design, proper technical use, and adequate indications. We present our experience with a specific implant type that we have used for over 30 years and which has given our elderly patients good mid-term results. Because revision of implants with long cemented stems can be very challenging, an effort should be made in the future to use shorter stems in modular versions of hinged implants.