Psoas muscle cross sectional area relates to bone density and microarchitecture in candidates for spine fusion surgery.

Prior studies demonstrate that muscle and bone health are integrally related, and both independently impact orthopedic surgery outcomes. However, relationships between bone density, in vivo microarchitecture, and muscle area have not been previously investigated in orthopedic surgery patients. This study assessed associations between psoas cross sectional area (CSA), bone mineral density (BMD), and microstructure in a cohort undergoing spine fusion. Pre-operatively, bilateral psoas CSA was measured on axial lumbar spine CT in the L3-L4 disc space. To adjust for body size, Psoas Muscle Index (PMI) was calculated (CSA divided by the square of patient height). High resolution peripheral quantitative CT (HR-pQCT, XtremeCT2) assessed volumetric BMD (vBMD), cortical (Ct) and trabecular (Tb) microarchitecture at the distal radius and tibia. Areal BMD (aBMD) was measured by DXA at the lumbar spine (LS), total hip (TH), femoral neck (FN), and the 1/3 radius (1/3R). Pearson correlations related psoas CSA and bone imaging parameters before and after correcting for height and weight. Among 88 patients included, mean age was 63 ± 12 years, BMI was 28 ± 7 kg/m2, 47 (53 %) were female. Larger psoas CSA was associated with higher vBMD, greater Ct thickness and better Tb microarchitecture (higher Tb number and lower Tb separation) at the tibia and radius. Larger psoas CSA was also associated with greater aBMD at TH and FN bilaterally and 1/3R (r 0.33 to 0.61; p < 0.002 for all comparisons). Psoas CSA was not associated with aBMD at the LS. Similar results were observed when relating PMI, and adjusting for age, height and weight to HR-pQCT and DXA measurements. Investigation of subgroups by sex demonstrated that relationships were similar magnitude among women but not the men. Patients who underwent primary compared to revision spine surgery had similar associations. Our results demonstrate a link between psoas muscle size and peripheral bone microarchitecture among patients undergoing posterior lumbar spinal fusion. Given the importance of both muscle and skeletal integrity to the success of spine surgery, further study regarding the associations between measurements of psoas muscle, bone microarchitecture, and surgical outcomes is warranted.

Baseline-to-loaded changes in regional tibial cartilage thickness, T1ρ and T2: Utilization of an MRI compatible loading device.

The objective of the study was to evaluate tibial cartilage thickness (TCT), T1ρ and T2 values within both loaded and baseline configurations in a cadaveric knee model using a 3D bone based tibial coordinate system. Ten intact cadaveric knees were mounted into an magnetic resonance imaging (MRI) compatible loading device. Morphologic and quantitative MRI (qMRI) images were acquired with the knee in a baseline configuration and after application of 50% body weight. The morphologic images were evaluated for cartilage degeneration using a modified Noyes scoring system. A 3D bone-based tibial coordinate system was utilized to evaluate regional changes of tibial T1ρ, T2, and cartilage thickness values among regions covered and uncovered by the meniscus. Inter-regional differences in medial and lateral MRI outcomes were found between loaded and baseline configurations. Cartilage regions covered by the meniscus demonstrated disparate qMRI and TCT results as compared to cartilage regions not covered by the meniscus. The regions covered by meniscus experienced a ~3.5%, ~0.5%, and ~5.5% reduction of T1ρ (p < 0.05, medial and lateral compartments), T2 and TCT, respectively, in both compartments while regions not covered by the meniscus experienced larger reductions of ~10%, ~2%, and ~10.5% reduction of T1ρ (p < 0.05, medial and lateral compartments), T2 and TCT (p < 0.05, lateral compartment only), respectively, in both compartments. T1ρ and T2 decreases following application of 50% body weight load were substantially larger in the tibial regions with modified Noyes grade 3 (n = 2) compared to either healthy regions (n = 85, p < 0.0.003) or regions with modified Noyes grade 2 (n = 13, p < 0.004). Interregional differences in MRI outcomes reflect variations in structure and function, and largely followed a pattern in cartilage regions that were covered or not covered by the meniscus. Results of the current study suggest that ΔT1ρ and ΔT2 values may be sensitive to superficial fissuring, more than baseline or loaded T1ρ or T2 values, or TCT alone, however future studies with additional specimens, with greater variability in OA grade distribution, may further emphasize the current findings.

Fully automated determination of robotic pedicle screw accuracy and precision utilizing computer vision algorithms.

Historically, pedicle screw accuracy measurements have relied on CT and expert visual assessment of the position of pedicle screws relative to preoperative plans. Proper pedicle screw placement is necessary to avoid complications, cost and morbidity of revision procedures. The aim of this study was to determine accuracy and precision of pedicle screw insertion via a novel computer vision algorithm using preoperative and postoperative computed tomography (CT) scans. Three cadaveric specimens were utilized. Screw placement planning on preoperative CT was performed according to standard clinical practice. Two experienced surgeons performed bilateral T2-L4 instrumentation using robotic-assisted navigation. Postoperative CT scans of the instrumented levels were obtained. Automated segmentation and computer vision techniques were employed to align each preoperative vertebra with its postoperative counterpart and then compare screw positions along all three axes. Registration accuracy was assessed by preoperatively embedding spherical markers (tantalum beads) to measure discrepancies in landmark alignment. Eighty-eight pedicle screws were placed in 3 cadavers' spines. Automated registrations between pre- and postoperative CT achieved sub-voxel accuracy. For the screw tip and tail, the mean three-dimensional errors were 1.67 mm and 1.78 mm, respectively. Mean angular deviation of screw axes from plan was 1.58°. For screw mid-pedicular accuracy, mean absolute error in the medial-lateral and superior-inferior directions were 0.75 mm and 0.60 mm, respectively. This study introduces automated algorithms for determining accuracy and precision of planned pedicle screws. Our accuracy outcomes are comparable or superior to recent robotic-assisted in vivo and cadaver studies. This computerized workflow establishes a standardized protocol for assessing pedicle screw placement accuracy and precision and provides detailed 3D translational and angular accuracy and precision for baseline comparison.

Morphology of the scaphotrapeziotrapezoid joint: A multi-domain statistical shape modeling approach.

The scaphotrapeziotrapezoid (STT) joint is involved in load transmission between the wrist and thumb. A quantitative description of baseline STT joint morphometrics is needed to capture the variation of normal anatomy as well as to guide staging of osteoarthritis. Statistical shape modeling (SSM) techniques quantify variations in three-dimensional shapes and relative positions. The objectives of this study are to describe the morphology of the STT joint using a multi-domain SSM. We asked: (1) What are the dominant modes of variation that impact bone and articulation morphology at the STT joint, and (2) what are the morphometrics of SSM-generated STT joints? Thirty adult participants were recruited to a computed tomography study of normal wrist imaging and biomechanics. Segmentations of the carpus were converted to three-dimensional triangular surface meshes. A multi-domain, particle-based entropy system SSM was used to quantify variation in carpal bone shape and position as well as articulation morphology. Articular surface areas and interosseous proximity distributions were calculated between mesh vertex pairs on adjacent bones within distance (2.0 mm) and surface-normal angular (35°) thresholds. In the SSM, the first five modes of variation captured 76.2% of shape variation and contributed to factors such as bone scale, articular geometries, and carpal tilt. Median interosseous proximities-a proxy for joint space-were 1.39 mm (scaphotrapezium), 1.42 mm (scaphotrapezoid), and 0.61 mm (trapeziotrapezoid). This study quantifies morphological and articular variations at the STT joint, presenting a range of normative anatomy. The range of estimated interosseous proximities may guide interpretation of imaging-derived STT joint space.

Detection of scapholunate interosseous ligament injury using dynamic computed tomography-derived arthrokinematics: A prospective clinical trial.

Scapholunate interosseous ligament injuries are a major cause of wrist instability and can be difficult to diagnose radiographically. To improve early diagnosis of scapholunate ligament injuries, we compared injury detection between bilateral routine clinical radiographs, static CT, and dynamic four-dimensional CT (4DCT) during wrist flexion-extension and radioulnar deviation. Participants with unilateral scapholunate ligament injuries were recruited to a prospective clinical trial investigating the diagnostic utility of 4DCT imaging for ligamentous wrist injury. Twenty-one participants underwent arthroscopic surgery to confirm scapholunate ligament injury. Arthrokinematics, defined as distributions of interosseous proximities across radioscaphoid and scapholunate articular surfaces at different positions within the motion cycle, were used as CT-derived biomarkers. Preoperative radiographs, static CT, and extrema of 4DCT were compared between uninjured and injured wrists using Wilcoxon signed rank or Kolmogorov-Smirnov tests. Median interosseous proximities at the scapholunate interval were significantly greater in the injured versus the uninjured wrists at static-neutral and maximum flexion, extension, radial deviation, and ulnar deviation. Mean cumulative distribution functions at the radioscaphoid joint were not significantly different between wrists but were significantly shifted at the scapholunate interval towards increased interosseous proximities in injured versus uninjured wrists in all positions. Median and cumulative distribution scapholunate proximities from static-neutral and 4DCT-derived extrema reflect injury status.

OrthoFusion: A Super-Resolution Algorithm to Fuse Orthogonal CT Volumes.

OrthoFusion, an intuitive super-resolution algorithm, is presented in this study to enhance the spatial resolution of clinical CT volumes. The efficacy of OrthoFusion is evaluated, relative to high-resolution CT volumes (ground truth), by assessing image volume and derived bone morphological similarity, as well as its performance in specific applications in 2D-3D registration tasks. Results demonstrate that OrthoFusion significantly reduced segmentation time, while improving structural similarity of bone images and relative accuracy of derived bone model geometries. Moreover, it proved beneficial in the context of biplane videoradiography, enhancing the similarity of digitally reconstructed radiographs to radiographic images and improving the accuracy of relative bony kinematics. OrthoFusion's simplicity, ease of implementation, and generalizability make it a valuable tool for researchers and clinicians seeking high spatial resolution from existing clinical CT data. This study opens new avenues for retrospectively utilizing clinical images for research and advanced clinical purposes, while reducing the need for additional scans, mitigating associated costs and radiation exposure.

Assessing carpal kinematics following scapholunate interosseous ligament injury ex vivo using four-dimensional dynamic computed tomography.

BACKGROUND: Scapholunate interosseous ligament injuries are prevalent and often challenging to diagnose radiographically. Four-dimensional CT allows visualization of carpal bones during motion. We present a cadaveric model of sequential ligamentous sectionings ("injuries") to quantify their effects on interosseous proximities at the radioscaphoid joint and scapholunate interval. We hypothesized that injury, wrist position, and their interaction affect carpal arthrokinematics. METHODS: Eight cadaveric wrists were moved through flexion-extension and radioulnar deviation after injuries. Dynamic CT images of each motion were acquired in each injury condition using a second-generation dual-source CT scanner. Carpal osteokinematics were used to calculate arthrokinematic interosseous proximity distributions during motion. Median interosseous proximities were normalized and categorized by wrist position. Linear mixed-effects models and marginal means tests were used to compare distributions of median interosseous proximities. FINDINGS: The effect of wrist position was significant for both flexion-extension and radioulnar deviation at the radioscaphoid joint; the effect of injury was significant for flexion-extension at the scapholunate interval; and the effect of their interaction was significant for radioulnar deviation at the scapholunate interval. Across wrist positions, radioscaphoid median interosseous proximities were less able to distinguish injury conditions versus scapholunate proximities. Median interosseous proximities at the scapholunate interval are majoritively able to detect differences between less (Geissler I-III) versus more (Geissler IV) severe injuries when the wrist is flexed, extended, and ulnarly-deviated. INTERPRETATION: Dynamic CT enhances our understanding of carpal arthrokinematics in a cadaveric model of SLIL injury. Scapholunate median interosseous proximities in flexion, extension, and ulnar deviation best demonstrate ligamentous integrity.

Evaluation of Scapholunate Injury and Repair with Dynamic (4D) CT: A Preliminary Report of Two Cases.

Background In predynamic or dynamic scapholunate (SL) instability, standard diagnostic imaging may not identify SL interosseous ligament (SLIL) injury, leading to delayed detection and intervention. This study describes the use of four-dimensional computed tomography (4DCT) in identifying early SLIL injury and following injured wrists to 1-year postoperatively. Description of Technique 4DCT acquires a series of three-dimensional volume data with high temporal resolution (66 ms). 4DCT-derived arthrokinematic data can be used as biomarkers of ligament integrity. Patients and Methods This study presents the use of 4DCT in a two-participant case series to assess changes in arthrokinematics following unilateral SLIL injury preoperatively and 1-year postoperatively. Patients were treated with volar ligament repair with volar capsulodesis and arthroscopic dorsal capsulodesis. Arthrokinematics were compared between uninjured, preoperative injured, and postoperative injured (repaired) wrists. Results 4DCT detected changes in interosseous distances during flexion-extension and radioulnar deviation. Generally, radioscaphoid joint distances were greatest in the uninjured wrist during flexion-extension and radioulnar deviation, and SL interval distances were smallest in the uninjured wrist during flexion-extension and radioulnar deviation. Conclusion 4DCT provides insight into carpal arthrokinematics during motion. Distances between the radioscaphoid joint and SL interval can be displayed as proximity maps or as simplified descriptive statistics to facilitate comparisons between wrists and time points. These data offer insight into areas of concern for decreased interosseous distance and increased intercarpal diastasis. This method may allow surgeons to assess whether (1) injury can be visualized during motion, (2) surgery repaired the injury, and (3) surgery restored normal carpal motion. Level of Evidence Level IV, Case series.

Assessment of Patellar Vascularity after Patellar Cartilage Restoration via Lateral Parapatellar Approach: Analysis Using Dynamic Contrast-Enhanced Magnetic Resonance Imaging.

OBJECTIVE: Patellofemoral cartilage restoration procedures, including osteochondral allograft, particulated juvenile cartilage, and matrix-induced autologous chondrocyte implantation, have been shown to be effective treatments for patellofemoral cartilage lesions. However, concerns exist regarding disruption of the patellar vascular supply and secondary stabilizers of the patellofemoral joint during medial parapatellar approaches, especially when combined with a lateral release. A lateral parapatellar approach affords the possibility of avoiding disruption of the medial blood supply to the patella, while also allowing laterally-based soft tissue stabilization procedures. The purpose of this study was to investigate in vivo changes in patellar vascularity following patellofemoral cartilage restoration procedures performed via a lateral parapatellar approach via use of dynamic contrast-enhanced magnetic resonance (MR) imaging. DESIGN: This study is a prospective case series of 5 adult patients undergoing patellofemoral cartilage restoration procedures via a lateral parapatellar approach with pre-operative and post-operative dynamic contrast-enhanced MR imaging to assess changes in patellar vascularity. Secondary outcomes included knee range of motion, need for revision surgery, and complications. RESULTS: There was no significant post-operative difference in patellar vascularity in patients undergoing patellofemoral cartilage restoration procedures via a lateral parapatellar approach, as evaluated by qualitative MR imaging. CONCLUSION: Our results suggest that a lateral parapatellar approach for cartilage restoration procedures may preserve patellar vascularity, while also allowing for lateral release to be performed through the same incision.

Opportunistic Evaluation of Trabecular Bone Texture by MRI Reflects Bone Mineral Density and Microarchitecture.

CONTEXT: Many individuals at high risk for fracture are never evaluated for osteoporosis and subsequently do not receive necessary treatment. Utilization of magnetic resonance imaging (MRI) is burgeoning, providing an ideal opportunity to use MRI to identify individuals with skeletal deficits. We previously reported that MRI-based bone texture was more heterogeneous in postmenopausal women with a history of fracture compared to controls. OBJECTIVE: The present study aimed to identify the microstructural characteristics that underlie trabecular texture features. METHODS: In a prospective cohort, we measured spine volumetric bone mineral density (vBMD) by quantitative computed tomography (QCT), peripheral vBMD and microarchitecture by high-resolution peripheral QCT (HRpQCT), and areal BMD (aBMD) by dual-energy x-ray absorptiometry. Vertebral trabecular bone texture was analyzed using T1-weighted MRIs. A gray level co-occurrence matrix was used to characterize the distribution and spatial organization of voxelar intensities and derive the following texture features: contrast (variability), entropy (disorder), angular second moment (ASM; uniformity), and inverse difference moment (IDM; local homogeneity). RESULTS: Among 46 patients (mean age 64, 54% women), lower peripheral vBMD and worse trabecular microarchitecture by HRpQCT were associated with greater texture heterogeneity by MRI-higher contrast and entropy (r ∼ -0.3 to 0.4, P < .05), lower ASM and IDM (r ∼ +0.3 to 0.4, P < .05). Lower spine vBMD by QCT was associated with higher contrast and entropy (r ∼ -0.5, P < .001), lower ASM and IDM (r ∼ +0.5, P < .001). Relationships with aBMD were less pronounced. CONCLUSION: MRI-based measurements of trabecular bone texture relate to vBMD and microarchitecture, suggesting that this method reflects underlying microstructural properties of trabecular bone. Further investigation is required to validate this methodology, which could greatly improve identification of patients with skeletal fragility.

The Dorsal Ligament Complex: A Cadaveric, Histology, and Imaging Study.

PURPOSE: The distinction between the dorsal intercarpal (DIC) and dorsal scaphotriquetral (DST) ligaments is imprecise and unclear in the literature. The purpose of our cadaveric study was to define the origins, insertions, and anatomic relationships of the dorsal wrist ligaments and relate these anatomic findings to magnetic resonance imaging (MRI) scans and histology. METHODS: The study included 17 unmatched fresh-frozen cadaveric specimens (7 male and 10 female), with a mean age of 67.1 years (range, 48-86 years). Wrists with arthritis or carpal malalignment were excluded. Ligaments were dissected and insertion sites were recorded in the radioulnar (width) and proximodistal (length) dimensions, centered at the midpoints of the insertion. Three cadaveric specimens underwent a histologic analysis to demonstrate ligament composition and insertion sites. Three additional cadavers underwent MRI, from which 3-dimensional models were built to model ligament topography. RESULTS: The conjoined triquetral insertion of the DIC, DST, and dorsal radiocarpal (DRC) measured 88.5 ± 6.4 mm2. In each specimen, there were 2 distinct deep and superficial components of intercarpal fibers. The deep component inserted on the lunate with an area of 59.0 ± 5.0 mm2. The deep and superficial components diverged as they coursed radially. The superficial component proceeded to the scaphoid ridge, trapezium, and trapezoid, whereas the deep component inserted on the proximal row. The deep fibers blended distally from their lunate insertion with the DST, forming a robust, 2.9 ± 0.8-mm wide extension over the dorsal capitate. The DRC inserted on the lunate, proximal to the DIC and DST insertions, with an area of 23.9 ± 5.4 mm2. CONCLUSIONS: The dorsal ligament complex forms a firm link across the proximal carpal row and the DST provides extension of the proximal row over the capitate. CLINICAL RELEVANCE: This information can guide surgeons while performing a dorsal approach to the wrist and repairing traumatic ligament disruption.

Optimizing Web-Based Viewer of 4D CT Scans for Clinical Assessment of Injured Wrists.

Wrist injuries pose a unique challenge for patients and providers. Due to the complexity of the wrist, it is difficult to determine if a wrist injury is primarily a bone fracture or soft tissue damage. The scapholunate interosseous ligament (SLIL) is an important ligament in the function of the wrist, and it is also one of the most common soft tissue injuries in the wrist. Wrist arthroscopy is the gold standard for assessing injuries of the scapholunate joint; however, it is an invasive procedure. Recent advances in dynamic imaging with 4D Computed Tomography scans allow for the assessment of SLIL injuries non-invasively. Unfortunately, 4DCT scan data can be difficult to disseminate to clinical practitioners due to the large amount of data generated and the complexity in visualizing the data. A web-based application has been developed to interactively assess 4DCT scans of patients with suspected SLIL injury. Due to the magnitude of data and the diversity of hardware platforms used to visualize the data, the images are preprocessed with a rendering engine and presented in a pseudo-3D visualization paradigm where the user can interactively explore the 3D data without transmitting the entire dataset to the local computer. The technology has been used to assess 27 patients.

MRI-based Texture Analysis of Trabecular Bone for Opportunistic Screening of Skeletal Fragility.

CONTEXT: Many individuals at high risk for osteoporosis and fragility fracture are never screened by traditional methods. Opportunistic use of imaging obtained for other clinical purposes is required to foster identification of these patients. OBJECTIVE: The aim of this pilot study was to evaluate texture features as a measure of bone fragility, by comparing clinically acquired magnetic resonance imaging (MRI) scans from individuals with and without a history of fragility fracture. METHODS: This study retrospectively investigated 100 subjects who had lumbar spine MRI performed at our institution. Cases (n = 50) were postmenopausal women with osteoporosis and a confirmed history of fragility fracture. Controls (n = 50) were age- and race-matched postmenopausal women with no known fracture history. Trabecular bone from the lumbar vertebrae was segmented to create regions of interest within which a gray level co-occurrence matrix was used to quantify the distribution and spatial organization of voxel intensity. Heterogeneity in the trabecular bone texture was assessed by several features, including contrast (variability), entropy (disorder), and angular second moment (homogeneity). RESULTS: Texture analysis revealed that trabecular bone was more heterogeneous in fracture patients. Specifically, fracture patients had greater texture variability (+76% contrast; P = 0.005), greater disorder (+10% entropy; P = 0.005), and less homogeneity (-50% angular second moment; P = 0.005) compared with controls. CONCLUSIONS: MRI-based textural analysis of trabecular bone discriminated between patients with known osteoporotic fractures and controls. Further investigation is required to validate this promising methodology, which could greatly expand the number of patients screened for skeletal fragility.

Differences in the magnetic resonance imaging parameter T2* may be identified during the course of canine patellar tendon healing: a pilot study.

BACKGROUND: Previous studies have utilized ultrashort echo (UTE) magnetic resonance imaging (MRI), and derived T2* maps, to evaluate structures with highly ordered collagen structures such as tendon. T2* maps may provide a noninvasive means to assess tendon damage and healing. This pilot study evaluated the longitudinal relationship of an induced mechanical strain on the patellar tendon with corresponding UTE T2* metrics, histologic and biomechanical evaluation at two post-operative time points. METHODS: A total of 27 patellar tendons in male Beagles were surgically subjected to stretching by a small diameter (SmD) or a large diameter (LgD) diameter rod to induce damage due to strain, and evaluated at 4- and 8-week intervals using quantitative MRI (qMRI), biomechanical testing, and histology. A separate set of 16 limbs were used as controls. RESULTS: The tendons experienced a 67% and 17% prolongation of short T2* values as compared to controls at 4 and 8 weeks post-operatively, respectively. Histologic analysis displayed a trend of increased collagen disruption at 4 weeks followed by presence of greater organization at 8 weeks. Biomechanical evaluation found a reduction of tendon modulus and failure strain at both time points, and an increase in cross-sectional area at 4 weeks as compared to controls. CONCLUSIONS: These findings display tendon healing in response to an imposed strain and present the utility of qMRI to evaluate longitudinal differences of patellar tendon T2* values in a model of induced subclinical tendon damage. The qMRI technique of UTE provides a means to non-invasively evaluate the healing process of a mechanically damaged tendon.

Evaluation of Osseous Morphology of the Hip Using Zero Echo Time Magnetic Resonance Imaging.

BACKGROUND: Femoroacetabular impingement syndrome (FAIS) is a common disorder of the hip resulting in groin pain and ultimately osteoarthritis. Radiologic assessment of FAI morphologies, which may present with overlapping radiologic features of hip dysplasia, often requires the use of computed tomography (CT) for evaluation of osseous abnormality, owing to the difficulty of direct visualization of cortical and subchondral bone with conventional magnetic resonance imaging (MRI). The use of a zero echo time (ZTE) MRI pulse sequence may obviate the need for CT by rendering bone directly from MRI. PURPOSE/HYPOTHESIS: The purpose was to explore the application of ZTE MRI to the assessment of osseous FAI and dysplasia morphologies of the hip. It was hypothesized that angular measurements from ZTE images would show significant agreement with measurements obtained from CT images. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: Thirty-eight hips from 23 patients were imaged with ZTE MRI and CT. Clinically relevant angular measurements of hip morphology were made in both modalities and compared to assess agreement. Measurements included coronal and sagittal center-edge angles, femoral neck-shaft angle, acetabular version (at 1-, 2-, and 3-o'clock positions), Tönnis angle, alpha angle, and modified-beta angle. Interrater agreement was assessed for a subset of 10 hips by 2 raters. Intermodal agreement was assessed on the complete cohort and a single rater. RESULTS: Interrater agreement was demonstrated in both CT and ZTE, with intraclass correlation coefficient values ranging from 0.636 to 0.990 for ZTE and 0.747 to 0.983 for CT, indicating "good" to "excellent" agreement. Intermodal agreement was also shown to be significant, with intraclass correlation coefficients ranging from 0.618 to 0.904. CONCLUSION: Significant agreement of angular measurements for hip morphology exists between ZTE MRI and CT imaging. ZTE MRI may be an effective method to quantitatively evaluate osseous hip morphology.

The SoftHand Pro: Functional evaluation of a novel, flexible, and robust myoelectric prosthesis.

Roughly one quarter of active upper limb prosthetic technology is rejected by the user, and user surveys have identified key areas requiring improvement: function, comfort, cost, durability, and appearance. Here we present the first systematic, clinical assessment of a novel prosthetic hand, the SoftHand Pro (SHP), in participants with transradial amputation and age-matched, limb-intact participants. The SHP is a robust and functional prosthetic hand that minimizes cost and weight using an underactuated design with a single motor. Participants with limb loss were evaluated on functional clinical measures before and after a 6-8 hour training period with the SHP as well as with their own prosthesis; limb-intact participants were tested only before and after SHP training. Participants with limb loss also evaluated their own prosthesis and the SHP (following training) using subjective questionnaires. Both objective and subjective results were positive and illuminated the strengths and weaknesses of the SHP. In particular, results pre-training show the SHP is easy to use, and significant improvement in the Activities Measure for Upper Limb Amputees in both groups following a 6-8 hour training highlights the ease of learning the unique features of the SHP (median improvement: 4.71 and 3.26 and p = 0.009 and 0.036 for limb loss and limb-intact groups, respectively). Further, we found no difference in performance compared to participant's own commercial devices in several clinical measures and found performance surpassing these devices on two functional tasks, buttoning a shirt and using a cell phone, suggesting a functional prosthetic design. Finally, improvements are needed in the SHP design and/or training in light of poor results in small object manipulation. Taken together, these results show the promise of the SHP, a flexible and adaptive prosthetic hand, and pave a path forward to ensuring higher functionality in future.

Quantitative Magnetic Resonance Imaging and Histological Comparison of Normal Canine Menisci.

OBJECTIVE: The purpose of this observational study was to establish normative data for the canine menisci using magnetic resonance imaging (MRI). METHODS: Ten fresh stifles from five normal male Beagles were obtained from animals with no known lameness. Conventional MRI and ultrashort echo time (UTE) imaging were performed and T2* values calculated. Five stifles were assessed histologically. RESULTS: The caudal horn of the medial meniscus had significantly prolonged T2* values (4.6 ± 1.27 ms; p = 0.002) as compared with the cranial horn of the medial meniscus (3.25 ± 0.86 ms), and the cranial (3.06 ± 0.54 ms) and caudal (3.64 ± 0.72 ms) horns of the lateral meniscus. Histology demonstrated normal tibial, femoral, interior and peripheral meniscal margins, and normal cellularity. The medial meniscus was noted to be obliquely oriented to the scan plane compared with the relatively perpendicular orientation of the lateral meniscus as compared with the bore of the magnet in a limb-extended orientation. CLINICAL SIGNIFICANCE: Variability of MRI UTE T2* is seen in the normal canine meniscus, with prolongation of the caudal horn, medial meniscus. Prolongation may be due to magic angle effects, as the medial meniscus of the Beagle is not perpendicular to the axis of the main magnetic field. Canine meniscal injury is a common sequela to cruciate tear, and detecting meniscal damage is important for directing patient care. The non-invasive quantitative MRI technique of UTE imaging can be used for the evaluation of collagen orientation, while acknowledging inherent regions of prolongation.

The effect of glenohumeral plane of elevation on supraspinatus subacromial proximity.

Shoulder pain is a common clinical problem affecting most individuals in their lifetime. Despite the high prevalence of rotator cuff pathology in these individuals, the pathogenesis of rotator cuff disease remains unclear. Position and motion related mechanisms of rotator cuff disease are often proposed, but poorly understood. The purpose of this study was to determine the impact of systematically altering glenohumeral plane on subacromial proximities across arm elevation as measures of tendon compression risk. Three-dimensional models of the humerus, scapula, coracoacromial ligament, and supraspinatus were reconstructed from MRIs in 20 subjects. Glenohumeral elevation was imposed on the humeral and supraspinatus tendon models for three glenohumeral planes, which were chosen to represent flexion, scapular plane abduction, and abduction based on average values from a previous study of asymptomatic individuals. Subacromial proximity was quantified as the minimum distance between the supraspinatus tendon and coracoacromial arch (acromion and coracoacromial ligament), the surface area of the supraspinatus tendon within 2 mm proximity to the coracoacromial arch, and the volume of intersection between the supraspinatus tendon and coracoacromial arch. The lowest modeled subacromial supraspinatus compression measures occurred during flexion at lower angles of elevation. This finding was consistent across all three measures of subacromial proximity. Knowledge of this range of reduced risk may be useful to inform future studies related to patient education and ergonomic design to prevent the development of shoulder pain and dysfunction.

Ideal Starting Point and Trajectory of a Screw for the Dorsal Approach to Scaphoid Fractures.

PURPOSE: To determine the screw starting point and trajectory for the dorsal approach to scaphoid fractures that provides a combination of length and compression at the fracture site. METHODS: Computed tomography scans were obtained of 10 scaphoid fractures for 3 common fracture types. A computerized model was generated for each scaphoid. Screw starting point, length, and angle to the fracture plane were analyzed for starting points and trajectories within a safe zone that protected against cortical penetration. A novel analysis was developed to assess a combination of screw length and angle to fracture plane, termed "effective compression length" (ECL). ECL assessed the screw working distance perpendicular to the fracture. Results were analyzed to determine optimal screw starting point and trajectory. RESULTS: For proximal pole fractures, a screw perpendicular to the fracture was 9.7 mm from the longitudinal axis starting point (LASP). The screw with the largest ECL was 6.8 mm from the LASP, crossing the fracture at a 67° obliquity. For waist fractures, a perpendicular screw was 7.8 mm from the LASP. The screw with the largest ECL was 6.0 mm away, crossing the fracture at 74°. For distal oblique fractures, a perpendicular screw was 10.2 mm from the LASP. The screw with the largest ECL was 6.4 mm away, crossing the fracture at 70°. A screw with the classic starting point and trajectory crossed the fracture at obliquities of 48°, 51°, and 45° for proximal, waist, and distal fractures, respectively. CONCLUSIONS: Scaphoid screws placed with the classic starting point and trajectory cross the fracture at an obliquity. By altering the screw starting point and trajectory, screws with adequate length will be more perpendicular to the fracture plane. CLINICAL RELEVANCE: Screw starting point and trajectory for scaphoid fractures may be altered based on fracture type to obtain a long screw that is closer to perpendicular to the fracture.

Technical Developments: Zero Echo Time Imaging of the Shoulder: Enhanced Osseous Detail by Using MR Imaging.

Purpose To determine the intermodality agreement of morphologic grading and clinically relevant quantitative measurements between computed tomography (CT) and zero echo time (ZTE) magnetic resonance (MR) imaging of the shoulder. The primary objective was to demonstrate the clinical applicability of ZTE in osseous shoulder imaging. Materials and Methods Thirty-four patients undergoing standard-of-care (SOC) MR imaging with concomitant CT were enrolled in this institutional review board-approved study. ZTE images were acquired after SOC MR imaging. Glenoid morphology (version, vault depth, erosion), injury or disease (osteoarthritis, Bankart and Hill-Sachs lesions, subchondral cysts), and evidence of prior surgery were graded or measured. κ Values, intraclass correlation coefficients (ICCs), and Bland-Altman limits of agreement were used to establish agreement. Qualitative comparison of osseous findings was performed between ZTE and SOC MR imaging. Results Binary classification and nominal/ordinal grades showed substantial or better agreement between raters and modalities (κ or ICC > 0.6). Continuous measurements exhibited strong correlation between raters and modalities, although not universally. Bankart ICCs were not significant, owing to low prevalence. ZTE exhibited greater conspicuity of enthesopathic cysts and marrow edema. In 21 of 34 cases, ZTE imaging of osseous features exceeded SOC MR imaging. Conclusion ZTE MR imaging provides "CT-like" contrast for bone. The results of this study demonstrate strong intermodality agreement between measurements and grades from CT and ZTE images in a cohort of patients undergoing imaging with both modalities. A majority of ZTE image sets provided superior visualization of osseous features when compared with SOC MR image sets. This superiority coupled with strong quantitative agreement with CT suggests that ZTE may be used clinically in lieu of CT in some cases. © RSNA, 2017 Online supplemental material is available for this article.