High angular resolution diffusion imaging (HARDI) of porcine menisci: a comparison of diffusion tensor imaging and generalized q-sampling imaging.

Background: Diffusion magnetic resonance imaging (MRI) allows for the quantification of water diffusion properties in soft tissues. The goal of this study was to characterize the 3D collagen fiber network in the porcine meniscus using high angular resolution diffusion imaging (HARDI) acquisition with both diffusion tensor imaging (DTI) and generalized q-sampling imaging (GQI). Methods: Porcine menisci (n=7) were scanned ex vivo using a three-dimensional (3D) HARDI spin-echo pulse sequence with an isotropic resolution of 500 µm at 7.0 Tesla. Both DTI and GQI reconstruction techniques were used to quantify the collagen fiber alignment and visualize the complex collagen network of the meniscus. The MRI findings were validated with conventional histology. Results: DTI and GQI exhibited distinct fiber orientation maps in the meniscus using the same HARDI acquisition. We found that crossing fibers were only resolved with GQI, demonstrating the advantage of GQI over DTI to visualize the complex collagen fiber orientation in the meniscus. Furthermore, the MRI findings were consistent with conventional histology. Conclusions: HARDI acquisition with GQI reconstruction more accurately resolves the complex 3D collagen architecture of the meniscus compared to DTI reconstruction. In the future, these technologies have the potential to nondestructively assess both normal and abnormal meniscal structure.

Differential Diagnosis of Metatarsalgia.

Lesser (or central) metatarsalgia is defined as pain in the forefoot under or around the lesser metatarsals and their respective metatarsophalangeal joints. Two common causes of central metatarsalgia are Morton's neuroma (MN) and plantar plate (PP) injury. Because both clinical and imaging features overlap, establishing the correct differential diagnosis may be challenging. Imaging has a pivotal role in the detection and characterization of metatarsalgia. Different radiologic modalities are available to assess the common causes of forefoot pain, so the strengths and weakness of these imaging tools should be kept in mind. It is crucial to be aware of the pitfalls that can be encountered in daily clinical practice when dealing with these disorders. This review describes two main causes of lesser metatarsalgia, MN and PP injury, and their differential diagnoses.

Prospective Multireader Evaluation of Photon-counting CT for Multiple Myeloma Screening.

Purpose To determine whether photon-counting CT (PCCT) acquisition of whole-body CT images provides similar quantitative image quality and reader satisfaction for multiple myeloma screening at lower radiation doses than does standard energy-integrating detector (EID) CT. Materials and Methods Patients with monoclonal gammopathy of undetermined significance prospectively underwent clinical noncontrast whole-body CT with EID and same-day PCCT (August-December 2021). Five axial scan locations were evaluated by seven radiologists, with 11% (eight of 70) of images including osteolytic lesions. Images were shown in randomized order, and each reader rated the following: discernibility of the osseous cortex and osseous trabeculae, perceived image noise level, and diagnostic confidence. Presence of lytic osseous lesions was indicated. Contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were calculated. Comparisons were made using paired t tests and mixed linear effects models. Results Seven participants (four women) were included (mean age, 66 years ± 9 [SD]; body mass index, 30.1 kg/m2 ± 5.2). Mean cortical definition, trabecular definition, image noise, and image quality scores were 83, 67, 75, and 78 versus 84, 66, 74, and 76 for EID and PCCT, respectively (P = .65, .11, .26, and .11, respectively). PCCT helped identify more lesions (79% [22 of 28]) than did EID (64% [18 of 28]). CNRs and SNRs were similar between modalities. PCCT had lower radiation doses than EID (volume CT dose index: EID, 11.37 ± 2.8 vs PCCT, 1.8 ± 0.6 [P = .06]; dose-length product: EID, 1654.1 ± 409.6 vs PCCT, 253.4 ± 89.6 [P = .05]). Conclusion This pilot investigation suggests that PCCT affords similar quantitative and qualitative scores as EID at significantly lower radiation doses. Keywords: CT, CT-Spectral, Skeletal-Axial, Spine, Hematologic Diseases, Whole-Body Imaging, Comparative Studies Supplemental material is available for this article. © RSNA, 2022.

In Vivo Mechanical Function of the Distal Radial Ulnar Ligaments During Rotation of the Wrist.

PURPOSE: The purpose of this study was to investigate changes in length of the volar and dorsal radioulnar ligaments (VRULs and DRULs), and the distal radioulnar joint (DRUJ) space during unweighted and weighted rotation of the wrist using magnetic resonance imaging and biplanar fluoroscopy. METHODS: Fourteen wrists in 7 normal adult volunteers were imaged to define the 3-dimensional geometry of the DRUJ and the insertion sites of the superficial and deep bundles of the VRULs and DRULs. Subjects were imaged at 10 positions of forearm rotation ranging from full pronation to full supination, with or without a 5-pound weight. Lengths of the superficial and deep VRUL and DRUL bundles and DRUJ space were measured (in millimeters) at each position to evaluate ligament function and DRUJ stability. RESULTS: In the unweighted and weighted trials, maximal elongation of both deep and superficial VRUL bundles occurred in supination and maximal lengths of the deep and superficial DRUL bundles occurred in pronation. Maximum DRUJ space occurred during pronation and a minimum occurred in 30° of supination. In weighted trials, there was a significant increase in deep and superficial VRUL bundle length at positions between 30° of pronation and 30° of supination; however, there was no effect of weight on DRULs length. In weighted trials, there was a significant increase in DRUJ space at positions between full pronation and 15° of supination. CONCLUSIONS: This study demonstrates elongation of the VRULs in supination and the DRULs in pronation. There was no evidence of reciprocal loading of superficial/deep ligament bundles on either the dorsal or the volar aspects of the DRUJ. The effect of loading the wrist during rotation was apparent primarily in the VRULs, but not the DRULs. The DRUJ space was lowest at approximately 30° of supination. CLINICAL RELEVANCE: These results add information to the literature regarding the complicated biomechanics of the triangular fibrocartilage complex and DRUJ. Future work should evaluate changes in biomechanics caused by triangular fibrocartilage complex tears to determine how tear severity and location relate to clinical symptoms.

Phase 2 clinical trial of TORC1 inhibition with everolimus in men with metastatic castration-resistant prostate cancer.

BACKGROUND: Activation of the PI3K-Akt-mTOR signaling pathway is common in advanced castration resistant prostate cancer (CRPC), typically through PTEN loss. Preclinical studies suggest that Akt-driven CaP cells are genetically susceptible to mammalian target of rapamycin (mTOR, or TORC1) inhibition. Everolimus is a Food and Drug Administration-approved inhibitor of TORC1. MATERIALS AND METHODS: We performed a phase II study of everolimus in patients with mCRPC, who were refractory to standard of care hormonal and chemotherapeutic agents. Patients received everolimus 10 mg daily until unacceptable adverse events or disease progression. The primary efficacy outcome was confirmed 50% or greater prostate-specific antigen (PSA) response, using a 2 stage design with futility rules. Paired biopsies were utilized to assess for treatment effect on downstream TORC1 targets as well as tumor cell proliferation and apoptosis. RESULTS: Out of 35 men enrolled with heavily pretreated mCRPC, 32 were evaluable for clinical efficacy. No PSA responses were observed, the median progression-free survival time was 3.6 months (95% confidence interval = 2.9-4.8) and the median overall survival time was 10.4 months (95% confidence interval = 5.8-15.8). Several patients had declines in serum PSA upon cessation of everolimus. Thus, the study was closed due to clinical futility. The most common toxicities were mucositis, fatigue, anorexia, hypertriglyceridemia, and thrombocytopenia and were largely low grade. Pathologic evaluation of paired metastatic biopsies demonstrated consistent inhibition of pS6, a downstream mTOR pharmacodynamics biomarker, but the tumor proliferation marker Ki-67 increased with therapy. CONCLUSIONS: Everolimus demonstrated predictable toxicity in advanced and heavily pretreated patients with mCRPC. No clinical or clear pathologic effects despite downstream TORC1 target inhibition, suggesting that single agent everolimus has no clinical utility in men with mCRPC.

In vivo attachment site to attachment site length and strain of the ACL and its bundles during the full gait cycle measured by MRI and high-speed biplanar radiography.

The purpose of this study was to measure in vivo attachment site to attachment site lengths and strains of the anterior cruciate ligament (ACL) and its bundles throughout a full cycle of treadmill gait. To obtain these measurements, models of the femur, tibia, and associated ACL attachment sites were created from magnetic resonance (MR) images in 10 healthy subjects. ACL attachment sites were subdivided into anteromedial (AM) and posterolateral (PL) bundles. High-speed biplanar radiographs were obtained as subjects ambulated at 1 m/s. The bone models were registered to the radiographs, thereby reproducing the in vivo positions of the bones and ACL attachment sites throughout gait. The lengths of the ACL and both bundles were estimated as straight line distances between attachment sites for each knee position. Increased attachment to attachment ACL length and strain were observed during midstance (length = 28.5 ±â€¯2.6 mm, strain = 5 ±â€¯4%, mean ±â€¯standard deviation), and heel strike (length = 30.5 ±â€¯3.0 mm, strain = 12 ±â€¯5%) when the knee was positioned at low flexion angles. Significant inverse correlations were observed between mean attachment to attachment ACL lengths and flexion (rho = -0.87, p < 0.001), as well as both bundle lengths and flexion (rho = -0.86, p < 0.001 and rho = -0.82, p < 0.001, respectively). AM and PL bundle attachment to attachment lengths were highly correlated throughout treadmill gait (rho = 0.90, p < 0.001). These data can provide valuable information to inform design criteria for ACL grafts used in reconstructive surgery, and may be useful in the design of rehabilitation and injury prevention protocols.

Pharmacodynamic study of radium-223 in men with bone metastatic castration resistant prostate cancer.

BACKGROUND: Radium-223 is a targeted alpha-particle therapy that improves survival in men with metastatic castration resistant prostate cancer (mCRPC), particularly in men with elevated serum levels of bone alkaline phosphatase (B-ALP). We hypothesized that osteomimicry, a form of epithelial plasticity leading to an osteoblastic phenotype, may contribute to intralesional deposition of radium-223 and subsequent irradiation of the tumor microenvironment. METHODS: We conducted a pharmacodynamic study (NCT02204943) of radium-223 in men with bone mCRPC. Prior to and three and six months after radium-223 treatment initiation, we collected CTCs and metastatic biopsies for phenotypic characterization and CTC genomic analysis. The primary objective was to describe the impact of radium-223 on the prevalence of CTC B-ALP over time. We measured radium-223 decay products in tumor and surrounding normal bone during treatment. We validated genomic findings in a separate independent study of men with bone metastatic mCRPC (n = 45) and publicly accessible data of metastatic CRPC tissues. RESULTS: We enrolled 20 men with symptomatic bone predominant mCRPC and treated with radium-223. We observed greater radium-223 radioactivity levels in metastatic bone tumor containing biopsies compared with adjacent normal bone. We found evidence of persistent Cellsearch CTCs and B-ALP (+) CTCs in the majority of men over time during radium-223 therapy despite serum B-ALP normalization. We identified genomic gains in osteoblast mimicry genes including gains of ALPL, osteopontin, SPARC, OB-cadherin and loss of RUNX2, and validated genomic alterations or increased expression at the DNA and RNA level in an independent cohort of 45 men with bone-metastatic CRPC and in 150 metastatic biopsies from men with mCRPC. CONCLUSIONS: Osteomimicry may contribute in part to the uptake of radium-223 within bone metastases and may thereby enhance the therapeutic benefit of this bone targeting radiotherapy.

Obesity alters the in vivo mechanical response and biochemical properties of cartilage as measured by MRI.

BACKGROUND: Obesity is a primary risk factor for the development of knee osteoarthritis (OA). However, there remains a lack of in vivo data on the influence of obesity on knee cartilage mechanics and composition. The purpose of this study was to determine the relationship between obesity and tibiofemoral cartilage properties. METHODS: Magnetic resonance images (3T) of cartilage geometry (double-echo steady-state) and T1rho relaxation of the knee were obtained in healthy subjects with a normal (n = 8) or high (n = 7) body mass index (BMI) before and immediately after treadmill walking. Subjects had no history of lower limb injury or surgery. Bone and cartilage surfaces were segmented and three-dimensional models were created to measure cartilage thickness and strain. T1rho relaxation times were measured before exercise in both the tibial and femoral cartilage in order to characterize biochemical composition. Body fat composition was also measured. RESULTS: Subjects with a high BMI exhibited significantly increased tibiofemoral cartilage strain and T1rho relaxation times (P <0.05). Tibial pre-exercise cartilage thickness was also affected by BMI (P <0.05). Correlational analyses revealed that pre-exercise tibial cartilage thickness decreased with increasing BMI (R2 = 0.43, P <0.01) and body fat percentage (R2 = 0.58, P <0.01). Tibial and femoral cartilage strain increased with increasing BMI (R2 = 0.45, P <0.01; R2 = 0.51, P <0.01, respectively) and increasing body fat percentage (R2 = 0.40, P <0.05; R2 = 0.38, P <0.05, respectively). Additionally, tibial T1rho was positively correlated with BMI (R2 = 0.39, P <0.05) and body fat percentage (R2 = 0.47, P <0.01). CONCLUSIONS: Strains and T1rho relaxation times in the tibiofemoral cartilage were increased in high BMI subjects compared with normal BMI subjects. Additionally, pre-exercise tibial cartilage thickness decreased with obesity. Reduced proteoglycan content may be indicative of pre-symptomatic osteoarthritic degeneration, resulting in reduced cartilage thickness and increased deformation of cartilage in response to loading.

Magnetic resonance imaging evaluation of meniscoid superior labrum: normal variant or superior labral tear / Avaliação por ressonância magnética do lábio superior da glenoide de aspecto meniscoide: variante da normalidade ou lesão do lábio superior

Abstract Objective: The objective of this study was to determine the incidence of a "meniscoid" superior labrum. Materials and Methods: This was a retrospective analysis of 582 magnetic resonance imaging examinations of shoulders. Of those 582 examinations, 110 were excluded, for a variety of reasons, and the final analysis therefore included 472 cases. Consensus readings were performed by three musculoskeletal radiologists using specific criteria to diagnose meniscoid labra. Results: A meniscoid superior labrum was identified in 48 (10.2%) of the 472 cases evaluated. Arthroscopic proof was available in 21 cases (43.8%). In 10 (47.6%) of those 21 cases, the operative report did not include the mention a superior labral tear, thus suggesting the presence of a meniscoid labrum. In only one of those cases were there specific comments about a mobile superior labrum (i.e., meniscoid labrum). In the remaining 11 (52.4%), surgical correlation demonstrated superior labral tears. Conclusion: A meniscoid superior labrum is not an infrequent finding. Depending upon assumptions and the requirement of surgical proof, the prevalence of a meniscoid superior labrum in this study was between 2.1% (surgically proven) and 4.8% (projected). However, superior labral tears are just as common and are often confused with meniscoid labra.

Resumo Objetivo: O objetivo deste estudo é determinar a incidência do lábio superior da glenoide com aspecto meniscoide. Materiais e Métodos: Foi feita análise retrospectiva de 582 exames de ressonância magnética do ombro. Foram excluídos 110 casos por motivos diversos, restando 472 casos para avaliação. A leitura foi feita em consenso por três médicos radiologistas musculoesqueléticos. Resultados: Lábio superior meniscoide foi encontrado em 48 casos (10,2%). Resultados de artroscopia estavam disponíveis em 21 casos (43,8%). Em 10 destes casos (47,6%) não havia informação de lesão labral superior, sugerindo a presença de lábio meniscoide. Em apenas um caso havia comentário sobre um lábio superior hipermóvel, indicando um lábio meniscoide. Nos 11 casos restantes (52,4%) a correlação cirúrgica demonstrou lesão do lábio superior. Conclusão: Lábio superior de aspecto meniscoide não é um achado infrequente. Dependendo das hipóteses assumidas e da necessidade de prova cirúrgica, a prevalência de um lábio superior meniscoide varia entre 2,1% (comprovação cirúrgica) e 4,8% (projeção) nesta série. Entretanto, as lesões labrais superiores têm uma prevalência parecida e podem ser confundidas com o aspecto de um lábio meniscoide.

Effect of normal gait on in vivo tibiofemoral cartilage strains.

Altered cartilage loading is believed to be associated with osteoarthritis development. However, there are limited data regarding the influence of normal gait, an essential daily loading activity, on cartilage strains. In this study, 8 healthy subjects with no history of knee surgery or injury underwent magnetic resonance imaging of a single knee prior to and following a 20-min walking activity at approximately 1.1m/s. Bone and cartilage surfaces were segmented from these images and compiled into 3-dimensional models of the tibia, femur, and associated cartilage. Thickness changes were measured across a grid of evenly spaced points spanning the models of the articular surfaces. Averaged compartmental strains and local strains were then calculated. Overall compartmental strains after the walking activity were found to be significantly different from zero in all four tibiofemoral compartments, with tibial cartilage strain being significantly larger than femoral cartilage strain. These results provide baseline data regarding the normal tibiofemoral cartilage strain response to gait. Additionally, the technique employed in this study has potential to be used as a "stress test" to understand how factors including age, weight, and injury influence tibiofemoral cartilage strain response, essential information in the development of potential treatment strategies for the prevention of osteoarthritis.

The effects of femoral graft placement on cartilage thickness after anterior cruciate ligament reconstruction.

Altered joint motion has been thought to be a contributing factor in the long-term development of osteoarthritis after ACL reconstruction. While many studies have quantified knee kinematics after ACL injury and reconstruction, there is limited in vivo data characterizing the effects of altered knee motion on cartilage thickness distributions. Thus, the objective of this study was to compare cartilage thickness distributions in two groups of patients with ACL reconstruction: one group in which subjects received a non-anatomic reconstruction that resulted in abnormal joint motion and another group in which subjects received an anatomically placed graft that more closely restored normal knee motion. Ten patients with anatomic graft placement (mean follow-up: 20 months) and 12 patients with non-anatomic graft placement (mean follow-up: 18 months) were scanned using high-resolution MR imaging. These images were used to generate 3D mesh models of both knees of each patient. The operative and contralateral knee models were registered to each other and a grid sampling system was used to make site-specific comparisons of cartilage thickness. Patients in the non-anatomic graft placement group demonstrated a significant decrease in cartilage thickness along the medial intercondylar notch in the operative knee relative to the intact knee (8%). In the anatomic graft placement group, no significant changes were observed. These findings suggest that restoring normal knee motion after ACL injury may help to slow the progression of degeneration. Therefore, graft placement may have important implications on the development of osteoarthritis after ACL reconstruction.

Bone marrow biopsy: RNA isolation with expression profiling in men with metastatic castration-resistant prostate cancer--factors affecting diagnostic success.

PURPOSE: To determine the rate at which computed tomographically guided pelvic percutaneous bone biopsy in men with metastatic castration-resistant prostate cancer (mCRPC) yields adequate tissue for genomic profiling and to identify issues likely to affect diagnostic yields. MATERIALS AND METHODS: This study was institutional review board approved, and written informed consent was obtained. In a phase II trial assessing response to everolimus, 31 men with mCRPC underwent 54 biopsy procedures (eight men before and 23 men both before and during treatment). Variables assessed were lesion location (iliac wing adjacent to sacroiliac joint, iliac wing anterior and/or superior to sacroiliac joint, sacrum, and remainder of pelvis), mean lesion attenuation, subjective lesion attenuation (purely sclerotic vs mixed), central versus peripheral lesion sampling, lesion size, core number, and use of zoledronic acid for more than 1 year. RESULTS: Of 54 biopsy procedures, 21 (39%) yielded adequate tissue for RNA isolation and genomic profiling. Three of four sacral biopsies were adequate. Biopsies of the ilium adjacent to the sacroiliac joints were more likely adequate than those from elsewhere in the ilium (48% vs 28%, respectively). All five biopsies performed in other pelvic locations yielded inadequate tissue for RNA isolation. Mean attenuation of lesions with inadequate tissue was 172 HU greater than those with adequate tissue (621.1 HU ± 166 vs 449 HU ± 221, respectively; P = .002). Use of zoledronic acid, peripheral sampling, core number, and lesion size affected yields, but the differences were not statistically significant. Histologic examination with hematoxylin-eosin staining showed that results of 36 (67%) biopsies were positive for cancer; only mean attenuation differences were significant (707 HU ± 144 vs 473 HU ± 191, negative vs positive, respectively; P < .001). CONCLUSION: In men with mCRPC, percutaneous sampling of osseous metastases for genomic profiling is possible, but use of zoledronic acid for more than 1 year may reduce the yield of adequate tissue for RNA isolation. Sampling large low-attenuating lesions at their periphery maximizes yield.

Intercondylar synovial septum in two patients with nail-patella syndrome.

This case report describes the arthroscopic findings in two patients with nail-patella syndrome (NPS). In both cases, a midline synovial septum was encountered that completely subdivided the knee into medial and lateral compartments. One patient required two subsequent arthroscopic procedures, and the synovial septum was found to have recurred even after it had been resected at the initial surgery. The etiology and clinical significance of this anatomic anomaly are unknown, however, surgeons should be aware of its existence and the potential difficulties it may present during knee arthroscopy in patients with NPS.

The effect of modified Broström-Gould repair for lateral ankle instability on in vivo tibiotalar kinematics.

BACKGROUND: Lateral ankle instability leads to an increased risk of tibiotalar joint osteoarthritis. Previous studies have found abnormal tibiotalar joint motions with lateral ankle instability that may contribute to this increased incidence of osteoarthritis, including increased anterior translation and internal rotation of the talus under weightbearing loading. Surgical repairs for lateral ankle instability have shown good clinical results, but the effects of repair on in vivo ankle motion are not well understood. HYPOTHESIS: The modified Broström-Gould lateral ligament reconstruction decreases anterior translation and internal rotation of the talus under in vivo weightbearing loading conditions. STUDY DESIGN: Controlled laboratory study. METHODS: Seven patients underwent modified Broström-Gould repair for unilateral lateral ankle instability. Ankle joint kinematics as a function of increasing body weight was studied with magnetic resonance imaging and biplanar fluoroscopy. Tibiotalar kinematics was measured in unstable ankles preoperatively and postoperatively at a mean follow-up of 12 months as well as in the uninjured contralateral ankles of the same patients. RESULTS: Surgical repair resulted in statistically significant decreases (expressed as mean ± standard error of the mean) in anterior translation of the talus (0.9 ± 0.3 mm; P = .018) at 100% body weight and internal rotation of the talus at 75% (2.6° ± 0.8°; P = .019) and 100% (2.7° ± 0.8°; P = .013) body weight compared with ankle kinematics measured before repair. No statistically significant differences were detected between repaired ankles and contralateral normal ankles. CONCLUSION: The modified Broström-Gould repair improved the abnormal joint motion observed in patients with lateral ankle instability, decreasing anterior translation and internal rotation of the talus. CLINICAL RELEVANCE: Altered kinematics may contribute to the tibiotalar joint degeneration that occurs with chronic lateral ankle instability. The findings of the current study support the efficacy of this repair in improving the abnormal ankle motion observed in these patients.

The role of dynamic contrast-enhanced magnetic resonance imaging in the diagnosis and management of patients with vascular malformations.

OBJECTIVE: Vascular malformations are uncommon but may confer significant morbidity. Limitations in diagnosis and treatment result from inadequate classification schema and diagnostic algorithms. The crucial distinction is between high-flow and low-flow lesions because this informs prognosis and treatment. This study assessed the utility of dynamic contrast-enhanced magnetic resonance imaging (dceMRI) in distinguishing high-flow from low-flow lesions, a technique that has previously not been widely applied or evaluated in this patient population. METHODS: A prospective database of all patients referred to the multidisciplinary vascular malformation team at our institution was reviewed from January 2006 to June 2010. dceMRI was obtained on each patient to determine flow characteristics and lesion extent. Additional studies were used as indicated. Catheter-based arteriography was performed when high-flow lesions were identified with the intention of intervening or to distinguish between high-flow and low-flow lesions when MRI was indeterminate. A triage algorithm was used to stratify patients and formulate therapeutic goals. We analyzed the accuracy of dceMRI in identifying high-flow and low-flow lesions. RESULTS: The study included 122 patients (aged <1 to 70 years) comprising 52 males (42.6%) and 70 females (57.4%). Pain (72 patients; 59%) and swelling (88 patients; 72.1%) were the most common presenting symptoms. All patients underwent dceMRI. Of these, 68 had confirmatory imaging (n = 15) or intervention (n = 53). The dceMRI was able to definitively and correctly distinguish high-flow from low-flow lesions in 57 studies, for an accuracy rate of 83.8%. In the remaining 11 studies, dceMRI correctly queried flow status but not definitively, and confirmatory angiography was required. CONCLUSIONS: Using a diagnostic tool designed to identify key clinical characteristics, we were able to successfully distinguish between high-flow and low-flow vascular malformations using dceMRI alone in 83.8% of patients, minimizing the need for unnecessary invasive catheter-based procedures.

The effect of femoral tunnel placement on ACL graft orientation and length during in vivo knee flexion.

Anatomically placed grafts are believed to more closely restore the function of the ACL. This study measured the effect of femoral tunnel placement on graft orientation and length during weight-bearing flexion. Both knees of twelve patients where the graft was placed near the anteroproximal border of the ACL and ten where the graft was placed near the center of the ACL were imaged using MR. These images were used to create 3D models of the reconstructed and intact contralateral knees, including the attachment sites of the native ACL and graft. Next, patients were imaged using biplanar fluoroscopy while performing a quasi-static lunge. The models were registered to the fluoroscopic images to reproduce in vivo knee motion. From the relative motion of the attachment sites on the models, the length and orientation of the graft and native ACL were measured. Grafts placed anteroproximally on the femur were longer and more vertical than the native ACL in both the sagittal and coronal planes, while anatomically placed grafts more closely mimicked ACL motion. In full extension, the grafts placed anteroproximally were 12.3±5.2° (mean and 95%CI) more vertical than the native ACL in the sagittal plane, whereas the grafts placed anatomically were 2.9±3.7° less vertical. Grafts placed anteroproximally were up to 6±2 mm longer than the native ACL, while the anatomically placed grafts were a maximum of 2±2 mm longer. In conclusion, grafts placed anatomically more closely restored native ACL length and orientation. As a result, anatomic grafts are more likely to restore intact knee kinematics.

Progress in MR imaging of the venous system.

This article reviews the utility of magnetic resonance imaging (MRI)/magnetic resonance venography (MRV) in the assessment of common venous problems. There is a brief synopsis of current MRI/MRV techniques used for such purposes. This is followed by a review of application of these techniques to specific diagnoses. In short, MRV is quite useful for assessing venous pathology.

Computer-assisted tibia preparation for total ankle arthroplasty: a cadaveric study.

BACKGROUND: Most surgeons performing total ankle arthroplasty (TAA) suggest that accurate tibial preparation perpendicular to the tibial shaft axis improves outcomes. Recent studies demonstrate that computerized surgical navigation significantly improves the accuracy of tibial preparation in total knee arthroplasty (TKA). METHODS: We performed the tibial preparation for TAA in seven matched pairs of cadaver lower extremities. One set of matched pairs was prepared using the conventional external tibial alignment guide/cutting block from the Scandanavian Total Ankle Replacement system (STAR, Waldemar Link GmbH & Co., Hamburg, Germany) under fluoroscopic guidance. The second set of matched pairs was prepared using the VectorVision((R)) navigation system (BrainLAB, Munich, Germany), with currently available computed tomography (CT)-based TKA software. Pre-operative CT data were used to assess the tibial mechanical axis. In both groups, accuracy of the tibial plafond preparation relative to the tibial shaft axis in both the coronal and sagittal planes was determined by fluoroscopic, radiographic and CT analysis. RESULTS: Mean values of the tibial cut for the set of matched-pair tibiae prepared by the conventional surgical method ranged across the three imaging assessment techniques in the ranges 89.3-89.6 degrees (coronal plane, anteroposterior) and 90.3-90.4 degrees (sagittal plane, lateral). For the computer-navigated set, the values were 89.7-89.9 degrees (coronal) and 89.1-89.4 degrees (sagittal). Comparison between the conventional and computer-navigated tibial measurements were not different at the 95% confidence interval (CI) for CT, fluoroscopy or radiographic assessments. CONCLUSIONS: Our results demonstrate that accuracy of TAA tibial preparation using computer-navigation equals that of the conventional technique performed by a foot and ankle surgeon experienced in TAA. We anticipate that this investigation will encourage the development of computer-navigation applications specific to TAA, with the potential of improving accuracy over conventional methods.