Bone quality is a critical determinant of outcomes following spine fusion surgery. However, patients with skeletal deficits are often only identified intra-operatively when there are unexpected problems with hardware placement, or post-operatively, when bone-related complications occur. MRI is routinely performed for diagnosis and surgical planning, making a technique based on clinical MRI ideal to opportunistically evaluate bone health. Texture analysis of trabecular bone from MRI has recently emerged as a biomarker of bone quality. This prospective study related pre-operative MRI-based texture from standard clinical images and areal BMD (aBMD) by DXA to post-operative outcomes following spine fusion. T1-weighted MR images were acquired from patients undergoing instrumented lumbar spine fusion. The following texture features were derived within the L1-L5 vertebral bodies to characterize the local distribution and spatial organization of signal intensity: contrast (variability) and entropy (disorder) for which higher values reflect high heterogeneity; angular second moment (ASM; uniformity) and inverse difference moment (IDM; homogeneity) for which higher values reflect low heterogeneity. Of 72 patients enrolled, mean age was 63 years (54% female). Patients were followed for a median of 13 months after surgery. Skeletal complications occurred in 27 patients (38%); proximal junctional kyphosis and screw loosening were the most common. There was no association between new complications and aBMD at any site. In contrast, patients who developed post-operative complications had greater pre-operative MRI-texture heterogeneity than those who did not, specifically higher contrast (26%) and entropy (12%), lower ASM (-13%) and IDM (-25%, p < 0.01 for all). In summary, greater heterogeneity of pre-operative bone texture from clinical MRIs was associated with skeletal complications following spine fusion. These findings support this novel method as an opportunistic screening technique to foster earlier identification of high-risk patients who would benefit from interventions to improve surgical outcomes.

BACKGROUND CONTEXT Posterior spinal fusion (PSF) was traditionally performed freehand. Robotic-assisted navigation (RAN) allows for increased accuracy/precision of pedicle screw (PS) placement by robotically establishing/maintaining the trajectory for drilling pedicle tracts and placing screws. However, RAN presents a steep learning curve. PURPOSE This study aimed to compare the 3D accuracy/precision of PS placement between an attending surgeon with RAN experience and a 4th-year orthopaedic surgery resident who completed an adult and pediatric spine orthopedic rotation with an introduction to robotic surgery. STUDY DESIGN/SETTING Cadaveric study. PATIENT SAMPLE Two adult cadavers. OUTCOME MEASURES Systematic error, precision, and accuracy between training levels for angular deviation and translational deviation. METHODS Two cadavers were utilized, one each by attending and resident. Cadavers underwent subperiosteal exposure from T2-L5, and subsequently PS were placed using RAN from T2-L5. Preoperative CT scans were used to plan screws; plans were transposed to the robotic planning platform. A computer-vision algorithm compared the postoperative CT screw position to the preoperatively planned screw position. Laminectomies were performed to assess breach. Systematic error (signed mean error), precision (2SD), and accuracy (mean absolute error) were statistically compared between training levels for angular and translational deviation at the screw tip/tail/mid-pedicle positions in the medial-lateral (ML) and superior-inferior (SI) directions. RESULTS Fifty-seven PS were placed in two cadavers. Attending screws were more precise and accurate than the resident screws in the ML direction at the tail and mid-pedicle positions, and attending screws were more precise in the ML direction at the tip (P<0.021). Resident screws had better systematic error and accuracy than attending screws in the SI direction at the tip, tail, and mid-pedicle positions (P<0.024). There were no differences in angular deviation performance metrics. All breaches were <1mm (1 attending, 2 resident). CONCLUSIONS This cadaveric study identified that increased surgical experience may increase accuracy and precision when placing screws in the clinically important medial-lateral direction of the pedicle when using RAN. Although the fourth-year orthopedic surgery resident with a spine rotation as well as an introduction to robotic surgery rotation placed clinically safe pedicle screws using RAN without breach, this study demonstrates that 3D accuracy metrics paired with RAN can help identify specific opportunities for improvement in surgical technique for trainees. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs.

Opportunistic screening for osteoporosis using images acquired for other purposes is a burgeoning area that may be of particular utility for the identification of surgical candidates with poor bone health. Texture analysis of clinical MRIs can be used to evaluate the heterogeneity of trabecular bone as a potential metric of bone quality. This cohort study investigated relationships between MRI-based vertebral trabecular bone texture and material properties by Fourier-transform infrared (FTIR) spectroscopy. We hypothesized that texture features from preoperative MRI images would reflect vertebral bone mineralization and collagen properties. In a cohort of 30 postmenopausal women (mean age 65) undergoing spine fusion surgery, T1-weighted MRI images were obtained using standard clinical sequences. A gray-level co-occurrence matrix was used to characterize the distribution and spatial organization of voxel intensities and derive texture features, including inverse difference moment, feature correlation, and contrast. Lumbar vertebral bone biopsies were obtained intraoperatively and analyzed with FTIR spectroscopy to assess composition, including metrics of mineral maturity (acid phosphate and carbonate:phosphate ratio). We found that vertebral trabecular bone texture by MRI was related to directly measured bone material properties: more heterogeneous texture was associated with less mature bone. Women with lower inverse difference moment had higher acid phosphate (r = -0.43, p < .02). Similarly, women with lower feature correlation had higher acid phosphate (r = -0.39, p < .04) and higher carbonate: phosphate (r = -0.47, p < .01). Women with higher contrast had higher acid phosphate (r = 0.381, p < .04). Our results suggest that preoperative MRI texture may predict intraoperative bone properties, specifically FTIR metrics of tissue age that may reflect local remodeling or microdamage repair processes. This finding supports the potential of MRI as a screening tool to identify individuals with abnormal bone quality.

Introduction: Anterior and posterior wall indices (AWI and PWI, respectively) have been traditionally utilized in the radiographic evaluation of acetabular wall contributions to femoral head coverage. This study aimed to determine if the radiographic correction obtained following periacetabular osteotomy (PAO) differed from that observed on computed tomography (CT) with respect to acetabular version (AV). Methods: Patients undergoing PAO by a single-surgeon in a mature hip preservation practice were retrospectively reviewed. Goals of fragment reorientation with respect to AV routinely included balanced anterior and posterior walls, with the posterior wall passing through the femoral head center. Patients with a post-PAO hip CT interpreted by a fellowship-trained musculoskeletal radiologist were included. AWI, PWI, and AV at 1:00, 2:00, 3:00 were among pre/post-operative radiographic (at 1-year) and CT measurements collected. Paired sample t-tests or Wilcoxon signed rank test were used to compare pre- to post-operative measurements, as needed. Pearson’s or Spearman’s correlations were utilized to determine associations between radiographic and CT version measurements. Results: 43 hips in 38 patients underwent analysis. Radiographic lateral and anterior center edge angles (LCEA, ACEA), PWI, Tonnis angle, and acetabular depth all significantly improved pre- to post-operatively (p<0.001 for all). Similarly, CT increases in AV were observed at 2:00 and 3:00 (15.0 ± 11.2 degrees versus 25.1 ± 10.0 and 18.8 ± 7.7 degrees versus 29.4 ± 8.2, respectively; p<0.001 for both). Pre- to post-operative changes in LCEA were weakly-to-moderately correlated to AV changes at 2:00 and 3:00 (r= 0.37 [p=0.01], r= 0.31 [p=0.04], respectively). No differences in AWI were observed following PAO (0.32 ± 0.13 versus 0.36 ± 0.11, p=0.24), and no correlation was present between post-operative AV at all levels and AWI (r= -.007 [p=0.96], r= -.090 [p=0.56], r= -.055 [p=0.72] at 1:00/2:00/3:00, respectively). Conclusions: Despite the appearance of a normalized radiograph following PAO and significant improvement in femoral head coverage with multiple radiographic indices, increased AV magnitude is observed post-operatively at 2:00 and 3:00 on CT. This, however, does not correlate with AWI. As lateral coverage increases with fragment reorientation, AV increases but not at the expense of AWI. Thus, AV visualized by CT is discordant with post-operative radiographic surrogates of femoral head coverage by the anterior and posterior walls.

Purpose:To develop a Conditional Denoising Diffusion Probabilistic Model (Conditional DDPM) for super-resolution (SR) of normal resolution (NR) multi-detector CT images (~0.4 mm detail size) to a level consistent with the recently introduced ultra-high-resolution (UHR) CT (~0.2 mm detail size) and to evaluate the impact of SR on texture metrics of trabecular bone. Methods:Four human cadaver femurs were imaged using Canon Precision CT in an NR mode, with spatial resolution representative of the current conventional multi-detector CT (0.25 × 0.25 × 0.5 mm voxels), and in a novel UHR mode (0.125 × 0.125 × 0.25 mm voxels). For training the conditional DDPM, 7717 spatially-aligned patches (16 × 16 mm) were extracted from the NR and UHR images of two femurs; the NR patch was used as a condition, the UHR patch was the target. Model validation involved 5400 patches from the third femur. Testing was performed by slice-by-slice application of the trained SR on 190 cubic regions of interest (ROIs) from both ends of the fourth femur. The resulting SR images of trabecular bone were evaluated qualitatively and in terms of agreement of radiomic texture metrics with UHR data. Specifically, 24 Grey Level Co-occurrence Matrix (GLCM) features were extracted within 5 mm sphere masks in corresponding cancellous bone regions of the UHR, SR, and NR datasets. Concordance correlation coefficients (CCC) were calculated for NR vs. UHR and SR vs. UHR to assess UHR texture restoration using SR. Additionally, we investigated the overlap of NR vs. UHR and SR vs. UHR texture in a 2-dimensional space span by the first two principal components of ROI GLCM features. Results:Visually, SR using the conditional DDPM appeared to enhance the resolution of NR images (condition) to a level comparable to UHR CT. GLCM matrix visualization confirmed that the SR images resembled the GLCM matrix of UHR CT more closely than NR. Notably, the SR ROIs achieved significantly higher CCCs against UHR for 22 texture features, with an average improvement of 161.3% and a maximum increase of 465.5% for the Inverse Difference Moment. However, two metrics, Cluster Prominence and Cluster Shade, exhibited slightly lower CCCs for SR vs. UHR compared to NR vs. UHR, with reductions of 6.4% and 4.3%, respectively. PCA visualization further confirmed a greater trabecular bone texture feature overlap between SR and UHR compared to NR and UHR. Conclusions:The conditional DDPM successfully enhances NR CT images to UHR quality, enabling more accurate visualization and quantification of bone microarchitecture. Importantly for bone radiomic applications, SR trabecular image texture features agree well with UHR CT for the majority of examined features, which may enable application of SR to harmonize NR data with UHR for predictive model development.

OBJECTIVE:The scaphotrapeziotrapezoid (STT) joint transmits load between the wrist and thumb. Despite its clinical importance, it has received less diagnostic attention than adjacent wrist and thumb joints. CT-derived three-dimensional models offer the ability to improve measurement of articular space by evaluating subchondral articular surfaces, which can be quantified using articular morphometrics. The objectives of this study were to investigate whether articular surface areas, interosseous proximities, and carpal bone positions differ between sexes. MATERIALS AND METHODS:Thirty participants (50% female, median age 27.0 years) were prospectively recruited to a cohort study of normative wrist imaging and biomechanics. Carpal bones were meshed from CT-based segmentations using a marching cubes algorithm. Rigid body kinematic parameters of individual bones were calculated. Carpal bone postures were defined using projection angles between bone centroids. Articular surface areas and interosseous proximity distributions between adjacent bones were calculated. Morphometrics were compared between sexes using Wilcoxon rank sum or two-tailed Kolmogorov-Smirnov tests as appropriate. RESULTS:Median articular surface area was significantly smaller in females than in males at the trapeziotrapezoid but not scaphotrapezium or scaphotrapezoid joints. Interosseous proximity distributions were closer in females at all joints (scaphotrapezium, 1.19 versus 1.42 mm; scaphotrapezoid, 1.15 versus 1.43 mm; trapeziotrapezoid, 0.45 versus 0.65 mm). Distal bones were more dorsally translated in females. CONCLUSION:This study quantifies sex-stratified morphological variations at the STT joint. Interosseous proximity distributions may guide interpretation of imaging-derived STT joint space and can serve as reference ranges for studies of STT arthrokinematics.

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.

Opportunistic screening is essential to improve the identification of individuals with osteoporosis. Our group has utilized image texture features to assess bone quality using clinical MRIs. We have previously demonstrated that greater heterogeneity of MRI texture related to history of fragility fractures, lower bone density, and worse microarchitecture. The present study investigated relationships between MRI-based texture features and biomechanical properties of bone using CT-based finite element analyses (FEAs). We hypothesized that individuals with greater texture heterogeneity would have lower stiffness and failure load. Thirty individuals included in this prospective study had CT and MRI of L1 and L2 vertebrae. Using T1-weighted MR images, a gray-level co-occurrence matrix was generated to characterize the distribution and spatial organization of voxelar signal intensities to derive the following texture features: contrast (variability), entropy (disorder), angular second moment (ASM; uniformity), and inverse difference moment (IDM; homogeneity). Features were calculated in five directions relative to the image plane. Whole-bone stiffness and failure load were calculated from phantom-calibrated lumbar QCT. Mean age of subjects was 59 ± 11 yr (57% female). Individuals with lower vertebral stiffness had greater texture heterogeneity; specifically, higher contrast (r = -0.54, p < .01), higher entropy (r = -0.52, p < .01), lower IDM (r = 0.54, p < .01) and lower ASM (r = 0.51, p < .01). Lower vertebral failure load and lower vBMD were similarly associated with greater texture heterogeneity. Relationships were unchanged when using the average of texture in all directions or the vertical direction in isolation. In summary, individuals with more heterogeneous MRI-based trabecular texture had lower stiffness and failure load by FEA, and lower vBMD by central quantitative CT. These results-the first relating MRI-based texture features and biomechanical properties of bone-provide further support that MRI-based texture measurements can be used to opportunistically detect skeletal fragility.

Background: Zero echo time (ZTE) imaging is a relatively new magnetic resonance (MR) pulse sequence that provides bone-soft tissue contrast similar to that of computed tomography (CT). Purpose: We sought to (1) determine the accuracy of ZTE MRI for the diagnosis of common ankle fractures and (2) investigate whether ZTE imaging sequences are equivalent to the gold standard of CT for the characterization of fracture fragments. Methods: We conducted a prospective case series of 54 patients with acute ankle trauma, in whom ZTE MRI was performed, followed by surgical reduction. Fractures on the ZTE sequence were correlated with the operative report as the reference standard. Raw agreement (%) and correlation (κ) were calculated. Selected fracture fragments were measured in 2 dimensions (anterior-posterior and superior-inferior) on corresponding sagittal ZTE and CT images by 3 independent radiologists to determine reliability. Results: The ZTE sequence demonstrated 47 distal fibular, 17 medial malleolar, 24 posterior malleolar, 5 anterior talofibular ligament avulsion, and 4 distal tibial fractures on the 54 cases. Raw agreement with operative findings was 95% (range: 86%-100%) and correlation almost perfect (0.960 [0.926-0.995]). Fragment characterization was accurate and repeatable. Intraobserver and interobserver agreement was excellent. Conclusions: Our case series suggests that the use of the MRI ZTE sequence may provide images with CT-like contrast for characterizing acute ankle fractures.

The recently introduced Photon Counting CT (PCCT) offers major advances in spatial resolution and material discrimination compared to conventional multi-detector CT. We investigate whether these new capabilities may enable accurate in vivo quantification of the trabecular microstructure of human bone. Human femoral bone was imaged using reference HR-pQCT (isotropic 60 μm voxels) and PCCT operated in a High Resolution mode (HR, 80 μm in-plane voxel size. 200 μm slice thickness) and in a Calcium-selective mode (CA, isotropic 390 μm voxels). 468 spherical Regions-of-Interest (ROIs) of 5 mm diameter were placed at corresponding locations in the HR-pQCT and PCCT volumes. The bone voxels of HR-pQCT and CA PCCT ROIs were segmented (binarized) using global Otsu thresholding; local Bernsen segmentation was used for HR PCCT. Trabecular thickness (TbTh), spacing (TbSp), number (TbN), and bone volume fraction (BV/TV) were measured in the binarized ROIs. The performance of PCCT morphometrics was evaluated in terms of correlation coefficient and numerical agreement with HR-pQCT. For ROIs with mean TbTh⪆250 μm (approaching the nominal resolution of HR PCCT), the average trabecular measurements obtained from HR PCCT achieved excellent correlations with the reference HR-pQCT: 0.88 for BvTv, 0.89 for TbTh, 0.81 for TbSp and 0.78 for TbN. For ROIs with mean TbTh of 200 μm – 250 μm, the correlations were slightly worse, ranging from 0.61 for TbTh to 0.84 for BvTv. The spatial resolution of CA PCCT in its current implementation is insufficient for microarchitectural measurements, but the material discrimination capability appears to enable accurate estimation of BvTv (correlation of 0.89 to HR-pQCT). The results suggest that the introduction of PCCT may enable microstructural evaluation of the trabecular bone of the lumbar spine and hip, which are inaccessible to current in vivo high-resolution bone imaging technologies. The findings of this work will inform the development of clinical indications for PCCT trabecular bone assessment.

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.

Evaluation of unloaded-to-loaded changes within cartilage revealed that tibial cartilage thickness, T1ρ, and T2 metrics all decreased/shortened following application of 50% BW axial load. Shortening of loaded qMRI values is likely attributed to water loss from the cartilage matrix due to PG/matrix damage and attendant loss of cartilage FCD within this cadaveric model. As both the static and dynamic responses of cartilage to load are impacted by degeneration, quantification of unloaded-to-loaded T1ρ and T2 values may provide additional insight into cartilage health. Future work will evaluate unloaded-to-loaded cartilage T2* metrics to better elucidate movements of free and bound water pools.

The measurements of bone macro- and microstructures provide major insight into bone health and risk fracture. The accuracy of these measurements is limited when Conventional CT is used. However, CT technology has advanced with the introduction of photon-counting detectors that offer significant improvements in spatial resolution. This advancement offers potential improvements in resolving trabecular microstructures, and the quantification of bone through current or emerging biomarkers. Additionally, the spectral separation available in photon-counting CT (PCCT) may further aid in quantification. The purpose of this study was to objectively investigate PCCT capabilities in accurate quantification of bone macro- and micro-structures. To do so, 5 human bone specimens were scanned using a PCCT scanner (NAEOTOM Alpha, Siemens) and an energy-integrating CT (EICT) (FORCE, Siemens). Each specimen was imaged at a CTDIvol of 4 and 8mGy, and then reconstructed with 2 matrix sizes and at least 2 kernels. For PCCT, a 70 keV virtual mono-energetic image series was acquired to evaluate the potential benefits of spectral maps. The same specimens were also scanned using a high-resolution peripheral quantitative CT to provide a ground truth for the bone metrics. Each image series was analyzed in terms of bone mineral density (BMD) and trabecular bone volume to total bone volume. PCCT demonstrated major improvements (5.5% compared to 17% error for EICT) in quantifying bone microstructures (BV/TV). However, the BMD measurements remained similar across imaging conditions and scanners, and did not significantly change by the PCCT spatial resolution enhancement. For BV/TV measurements, PCCT T3D was the most accurate when the sharpest kernel available and 1024-matrix size for (error: 5.53% +/- 4.72%) were used. Similarly, EICT images were the most accurate for BV/TV measurements (error: 16.70% +/- 10.55%) when a medium-sharpness kernel and 1024-matrix size were used. The overall results suggest that PCCT technology can further improve trabecular bone measurements and thus enhance the clinical decision making for patients with bone disease.

BACKGROUND CONTEXT Historically, pedicle screw accuracy measurements have relied on computed tomography (CT) and expert visual assessment of the position of pedicle screws relative to preoperative plans. Proper pedicle screw placement is necessary to avoid additional complications and cost of revision procedures. PURPOSE To determine accuracy and precision of pedicle screw insertion via a novel computer vision algorithm utilizing preoperative and postoperative CT scans. STUDY DESIGN/SETTING Cadaveric controlled lab study. PATIENT SAMPLE Three adult cadaveric specimens. OUTCOME MEASURES The difference in tip, tail, and mid-pedicle screw distance (in millimeters), mean error, variance, and mean absolute error between preoperative plan and postoperative CT. METHODS Screw placement was planned in generic planning and segmentation software using standard criteria for screw planning. Two surgeons experienced in robotic workflow performed bilateral T2-L4 instrumentation using robotic-assisted navigation. Postoperative CT scans of the entire vertebral column were obtained. Automated segmentation and computer vision techniques were employed to align each postoperative vertebra with its preoperative counterpart and then compare positions along all three axes in an automated fashion. The mid-pedicle position in the anterior-posterior plane was not reported as it is not a measurable parameter. Mean error (ME), mean absolute error (MAE), and variance were calculated. Systematic error, precision, and accuracy were defined as ME, 2 standard deviations, and MAE, respectively. RESULTS Eighty-eight pedicle screws were placed. The computer algorithm showed that robotic-assisted pedicle screw placement was both accurate and precise. This study demonstrates robotic assisted pedicle screws can be placed with submillimeter accuracy in the coronal plane. Furthermore, the tip measurements showed greater precision than the tail measurements. Figure 1 shows both the numerical values and a visual representation of accuracy and precision. CONCLUSIONS This study introduces automated algorithms for determining accuracy and precision of planned pedicle screws. Our accuracy outcomes are comparable or superior to recent data from robotic-assisted in vivo studies in adult patients, as well as prior cadaver studies. This algorithmic computerized workflow establishes a standardized protocol for assessment of pedicle screw placement accuracy and precision, and provides baseline accuracy and precision for both cadaveric and in vivo comparison. FDA Device/Drug Status Medtronic Mazor X Stealth (Approved for this indication)

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.

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.

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.

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.