Is stability of the proximal tibiofibular joint important in the multiligament-injured knee?

BACKGROUND: The incidence of proximal tibiofibular joint instability in the setting of the multiligament-injured knee has not been previously reported. The integrity of the proximal tibiofibular joint is required to perform a fibular-based, lateral-sided knee reconstruction. QUESTIONS/PURPOSES: We report (1) the frequency of proximal tibiofibular joint instability in patients presenting with multiligament knee injuries and evaluate (2) our ability to restore stability to this joint, (3) patient-reported outcome scores, and (4) complications in patients surgically treated for proximal tibiofibular joint instability at the time of treatment of multiligament knee instability. METHODS: From 2005 to 2013, 124 patients (129 knees) sustaining multiligament knee injuries with Grade 3 instability to at least two ligaments were treated at our institution. We defined proximal tibiofibular joint instability as a dislocated or dislocatable proximal tibiofibular joint at the time of surgery. These patients underwent surgery to restore proximal tibiofibular joint stability and ligament reconstruction or repair and were followed with routine clinical examination, radiographs, and subjective outcome measures, including Lysholm and IKDC scores. Minimum followup was 12 months (mean, 32 months; range, 12-61 months). RESULTS: Twelve knees (12 patients, 9% of 129 knees) showed proximal tibiofibular joint instability. Knee stability in 10 patients was restored to Grade 1 or less in all surgically treated ligaments. No proximal tibiofibular joint instability has recurred. No patients have complained of ankle stiffness or pain. In the ten patients with subjective scores, mean Lysholm score was 75 (range, 54-95) and mean IKDC score was 58 (range, 22-78). There were four complications: one failed posterolateral corner reconstruction, one proximal tibiofibular joint screw removal secondary to pain over the screw head, one deep infection treated with serial irrigation and débridements with graft retention, and one closed manipulation secondary to arthrofibrosis and loss of ROM. CONCLUSIONS: In the setting of multiligament-injured knees, our series demonstrated a 9% incidence of proximal tibiofibular joint instability. The technique we describe successfully restored stability to the proximal tibiofibular joint and resulted in satisfactory patient-reported outcomes with low complication rates. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Monte Carlo evaluation of hypothetical long axial field-of-view PET scanner using GE Discovery MI PET front-end architecture.

PURPOSE: The development of total-body PET scanners is of growing interest in the PET community. Investigation into the imaging properties of a hypothetical extended axial field-of-view (AFOV) GE Healthcare SiPM-based Discovery MI (DMI) system architecture has not yet been performed. In this work, we assessed its potential as a whole-body scanner using Monte Carlo simulations. The aim of this work was to (1) develop and validate a Monte Carlo model of a four-ring scanner and (2) extend its AFOV up to 2 m to evaluate performance gain through NEMA-based evaluation. METHODS: The DMI four-ring geometry and its pulse digitization scheme were modeled within the GATE Monte Carlo platform using published literature. The GATE scanner model was validated by comparing results against published NEMA performance measurements. Following the validation of the four-ring model, the model was extended to simulate 8-, 20-, 30-, and 40-ring systems. Spatial resolution, sensitivity, NECR, and scatter fraction were characterized with modified NEMA NU-2 2018 standards; however, the image quality measurements were not acquired due to computational limitations. Spatial resolutions were simulated for all scanner ring configurations using point sources to examine the effects of parallax errors. NEMA count rates were estimated using a standard 70 cm scatter phantom and an extended version of scatter phantom of length 200 cm with (1-800) MBq of 18 F for all scanners. Sensitivity was evaluated using NEMA methods with a 70 cm standard and a 200 cm long line source. RESULTS: The average FWHM of the radial/tangential/axial spatial resolution reconstructed with filtered back-projection at 1 and 10 cm from the scanner center were 3.94/4.10/4.41 mm and 5.29/4.89/5.90 mm for the four-ring scanner. Sensitivity was determined to be 14.86 cps/kBq at the center of the FOV for the four-ring scanner using a 70 cm line source. Sensitivity enhancement up to 21-fold and 60-fold were observed for 1 and 2 m AFOV scanners compared to four-ring scanner using a 200 cm long line source. Spatial resolution simulations in a 2 m AFOV scanner suggest a maximum degradation of ∼23.8% in the axial resolution compared to the four-ring scanner. However, the transverse resolution was found to be relatively constant when increasing the axial acceptance angle up to ±70°. The peak NECR was 212.92 kcps at 22.70 kBq/ml with a scatter fraction of 38.9% for a four-ring scanner with a 70 cm scatter phantom. Comparison of peak NECR using the 200 cm long scatter phantom relative to the four-ring scanner resulted in a NECR gain of 15 for the 20-ring and 28 for the 40-ring geometry. Spatial resolution, sensitivity, and scatter fraction showed an agreement within ∼7% compared with published measured values. CONCLUSIONS: The four-ring DMI scanner simulation was successfully validated against published NEMA measurements. Sensitivity and NECR performance of extended 1 and 2 m AFOV scanners based upon the DMI architecture were subsequently simulated. Increases in sensitivity and count-rate performance are consistent with prior simulation studies utilizing extensions of the Siemens mCT architecture and published NEMA measurements with the uEXPLORER system.

SIR-Spheres Activity Measurements Reveal Systematic Miscalibration.

The purpose of this work was to perform an independent and National Institute of Standards and Technology-traceable activity measurement of 90Y SIR-Spheres (Sirtex). γ-spectroscopic measurements of the 90Y internal pair production decay mode were made using a high-purity germanium detector. Methods: Measured annihilation radiation detection rates were corrected for radioactive decay during acquisition, dead time, source attenuation, and source geometry effects. Detection efficiency was determined by 2 independent and National Institute of Standards and Technology-traceable methods. Results: Measured SIR-Spheres vials (n = 5) contained more activity than specified by the manufacturer calibration; on average, the ratio of measured activity to calibrated was 1.233 ± 0.030. Activity measurements made using 2 distinct efficiency calibration methods agreed within 1%. Conclusion: The primary SIR-Spheres activity calibration appears to be a significant underestimate of true activity.

Imaging and dosimetric characteristics of 67 Cu.

In recent years the use of beta-emitting radiopharmaceuticals for cancer therapy has expanded rapidly following development of therapeutics for neuroendocrine tumors, prostate cancer, and other oncologic malignancies. One emerging beta-emitting radioisotope of interest for therapy is 67Cu (t1/2: 2.6 d) due to its chemical equivalency with the widely-established positron-emitting isotope 64Cu (t1/2: 12.7 h). In this work we evaluate both the imaging and dosimetric characteristics of 67Cu, as well as producing the first report of SPECT/CT imaging using 67Cu. To this end, 67Cu was produced by photon-induced reactions on isotopically-enriched 68Zn at the Low-Energy Accelerator Facility (LEAF) of Argonne National Laboratory, followed by bulk separation of metallic 68Zn by sublimation and radiochemical purification by column chromatography. Gamma spectrometry was performed by efficiency-calibrated high-purity germanium (HPGe) analysis to verify absolute activity calibration and establish radionuclidic purity. Absolute activity measurements corroborated manufacturer-recommended dose-calibrator settings and no radionuclidic impurities were observed. Using the Clinical Trials Network anthropomorphic chest phantom, SPECT/CT images were acquired. Medium energy (ME) SPECT collimation was found to provide the best image quality from the primary 185 keV gamma emission of 67Cu. Reconstructed images of 67Cu were similar in quality to images acquired using 177Lu. Recovery coefficients were calculated and compared against quantitative images of 99mTc, 177Lu, and 64Cu within the same anthropomorphic chest phantom. Production and clinical imaging of 67Cu appears feasible, and future studies investigating the therapeutic efficacy of 67Cu-based radiopharmaceuticals are warranted.

In vitro radiotherapy and chemotherapy alter migration of brain cancer cells before cell death.

Although radiotherapy and most cancer drugs target the proliferation of cancer cells, it is metastasis, the complex process by which cancer cells spread from the primary tumor to other tissues and organs of the body where they form new tumors, that leads to over 90% of all cancer deaths. Thus, there is an urgent need for anti-metastasis strategies alongside chemotherapy and radiotherapy. An important step in the metastatic cascade is migration. It is the first step in metastasis via local invasion. Here we address the question whether ionizing radiation and/or chemotherapy might inadvertently promote metastasis and/or invasiveness by enhancing cell migration. We used a standard laboratory irradiator, Faxitron CellRad, to irradiate both non-cancer (HCN2 neurons) and cancer cells (T98G glioblastoma) with 2 Gy, 10 Gy and 20 Gy of X-rays. Paclitaxel (5 µM) was used for chemotherapy. We then measured the attachment and migration of the cells using an electric cell substrate impedance sensing device. Both the irradiated HCN2 cells and T98G cells showed significantly (p < 0.01) enhanced migration compared to non-irradiated cells, within the first 20-40 h following irradiation with 20 Gy. Our results suggest that cell migration should be a therapeutic target in anti-metastasis/anti-invasion strategies for improved radiotherapy and chemotherapy outcomes.

Synchronous relaxation algorithm for parallel kinetic Monte Carlo simulations of thin film growth.

We present an optimistic synchronous relaxation algorithm for parallel kinetic Monte Carlo (KMC) simulations of thin film growth. This algorithm is based on spatial decomposition of the KMC lattice and it employs two measures aimed at improving the parallel efficiency: dynamic global updating and domain boundary shifting. We utilize this algorithm to simulate two different growth models, which represent the growth of Ag on Ag(111) and the heteroepitaxial growth of Ag on Pt(111). We show that these simulations can achieve good efficiency-especially for large domain sizes with a moderate number of processors. We find that domain boundary shifting can improve efficiency-especially for simulations of growth in the AgPt(111) system, where the potential-energy surface topology creates areas of rapid, localized motion. We analyze the origins of parallel efficiency in these simulations.

Acute epidural lipedema: a novel entity and potential complication of bone morphogenetic protein use in lumbar spine fusion.

BACKGROUND CONTEXT: Bone morphogenetic proteins (BMPs) induce osteogenesis, making them useful for decreasing time to union and increasing union rates. Although the advantages of BMP-2 as a substitute for iliac crest graft have been elucidated, less is known about the safety profile and adverse events linked to their use in spinal fusion. An accumulation of reactive edema in the epidural fat may lead to neural compression and significant morbidity after lumbar spinal fusion. Bone morphogenetic protein has never been implicated as a cause of spinal epidural lipedema. PURPOSE: We report on a case of rapid accumulation of edematous adipose tissue in the epidural space after lumbar spine decompression and fusion with bone morphogenic protein. STUDY DESIGN: Case report. METHODS: The patient was a 45-year-old woman with chronic back pain, worsening bilateral L5 radiculopathy, and degenerative disc disease. Surgery consisting of a one-level transpedicular decompression, transforaminal lumbar interbody fusion, and posterolateral fusion was performed using BMP-2 as an adjunct for arthrodesis. RESULTS: Two days postoperatively, the patient developed progressive cauda equina syndrome. Lumbar magnetic resonance imaging revealed edematous epidural fat extending above the initial laminectomy, compromising the spinal canal, and compressing the thecal sac. Emergent laminectomies at L3, L4, and L5 were performed, and intraoperative pathology revealed edematous epidural adipose tissue. The patient's cauda equina syndrome resolved after spinal decompression and the removal of epidural fat. Final cultures were negative for infection, and histology report yielded an accumulation of edematous fibroadipose tissue. CONCLUSIONS: We present a case of rapid accumulation of edematous adipose tissue causing cauda equina syndrome after a lumbar decompression and fusion surgery. The acute nature and extensive development of the lipedema presented in this case indicate an intense inflammatory reaction. We hypothesize that there may be a link between the use of BMP-2 and the accumulation of this edematous tissue. A thorough understanding of the mechanisms of BMP-2 and specific guidelines for their role in spinal surgery may improve functional outcomes and reduce the number of preventable complications. To the best of our knowledge and after a thorough literature search, this is the only reported case of epidural lipedema causing cauda equina syndrome.

Cervical spinal cord injury after thoracic spinal instrumentation: a case series.

STUDY DESIGN: Retrospective case report of 2 cases. OBJECTIVE: To describe 2 cases of cervical spinal cord injury/vascular insult after posterior instrumentation of thoracic/thoracolumbar scoliosis. SUMMARY OF BACKGROUND DATA: Spinal cord injury is an uncommon but well-documented complication associated with spinal deformity surgery. The midthoracic spinal cord is most vulnerable to these presumed vascular insults. Injuries above the level of instrumentation are rare. METHODS: In this report, we review the clinical histories of 2 adolescent females undergoing posterior spinal fusion with subsequent cervical spinal cord injuries. RESULTS: In both cases, intraoperative cervical alignment appeared neutral and all hardware appeared appropriately positioned. Spinal cord monitoring demonstrated changes in 1 patient but not in the other. With time, both patients improved clinically. CONCLUSION: Cervical spinal cord injuries may occur after distal deformity correction.