Publications by authors named "Andrew E Anderson"

74 Publications

Longitudinal study of knee load avoidant movement behavior after total knee arthroplasty with recommendations for future retraining interventions.

Knee 2021 Apr 16;30:90-99. Epub 2021 Apr 16.

University of Montana, School of Physical Therapy & Rehabilitation Science, Missoula, MT, United States. Electronic address:

Background: This study aimed to evaluate clinical and biomechanical changes in self-report survey, quadriceps strength and gait analysis over 3- and 6-months post-total knee arthroplasty (TKA) and confirm the immediate effects of two forms of kinetic biofeedback on improving inter-limb biomechanics during a physically demanding decline walking task.

Methods: Thirty patients with unilateral TKA underwent testing at 3- and 6-months following surgery. All underwent self-report survey, quadriceps strength and gait analysis testing. Patients were assigned to one of two types of biofeedback [vertical ground reaction force (vGRF), knee extensor moment (KEM)].

Results: No decrease in gait asymmetry was observed in non-biofeedback trials over time (p > 0.05), despite significant improvements in self-report physical function (p < 0.01, Cohen d = 0.44), pain interference (p = 0.01, Cohen d = 0.68), numeric knee pain (p = 0.01, Cohen d = 0.74) and quadriceps strength (p = 0.01, Cohen d = 0.49) outcomes. KEM biofeedback induced significant decrease in total support moment (p = 0.05, Cohen f = 0.14) and knee extensor moment (p = 0.05, Cohen f = 0.21) asymmetry compared to using vGRF biofeedback at 6-months. vGRF biofeedback demonstrated significant decrease in hip flexion kinematic asymmetry compared to KEM biofeedback (p = 0.05, Cohen f = 0.18) at 6-months.

Conclusion: Gait compensation remained similar from 3- to 6-months during a task requiring greater knee demand compared to overground walking post-TKA, despite improvements in self-report survey and quadriceps strength. Single session gait symmetry training at 6-month supports findings at 3-month testing that motor learning is possible. KEM biofeedback is more effective at immediately improving joint kinetic loading compared to vGRF biofeedback post-TKA.
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http://dx.doi.org/10.1016/j.knee.2021.03.014DOI Listing
April 2021

Statistical shape modeling of the talocrural joint using a hybrid multi-articulation joint approach.

Sci Rep 2021 Apr 1;11(1):7314. Epub 2021 Apr 1.

Department of Orthopaedics, University of Utah, Salt Lake City, 84108, USA.

Historically, conventional radiographs have been the primary tool to morphometrically evaluate the talocrural joint, which is comprised of the distal tibia, distal fibula, and proximal talus. More recently, high-resolution volumetric imaging, including computed tomography (CT), has enabled the generation of three-dimensional (3D) reconstructions of the talocrural joint. Weightbearing cone-beam CT (WBCT) technology provides additional benefit to assess 3D spatial relationships and joint congruency while the patient is load bearing. In this study we applied statistical shape modeling, a computational morphometrics technique, to objectively quantify anatomical variation, joint level coverage, joint space distance, and congruency at the talocrural joint. Shape models were developed from segmented WBCT images and included the distal tibia, distal fibula, and full talus. Key anatomical variation across subjects included the fibular notch on the tibia, talar trochlea sagittal plane rate of curvature, tibial plafond curvature with medial malleolus prominence, and changes in the fibular shaft diameter. The shape analysis also revealed a highly congruent talocrural joint with minimal inter-individual morphometric differences at the articular regions. These data are helpful to improve understanding of ankle joint pathologies and to guide refinement of operative treatments.
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http://dx.doi.org/10.1038/s41598-021-86567-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8016855PMC
April 2021

Combined Estimation of Shape and Pose for Statistical Analysis of Articulating Joints.

Shape Med Imaging (2020) 2020 Oct 3;12474:111-121. Epub 2020 Oct 3.

Scientific Computing and Imaging Institute, University of Utah.

Quantifying shape variations in articulated joints is of utmost interest to understand the underlying joint biomechanics and associated clinical symptoms. For joint comparisons and analysis, the relative positions of the bones can confound subsequent analysis. Clinicians design specific image acquisition protocols to neutralize the individual pose variations. However, recent studies have shown that even specific acquisition protocols fail to achieve consistent pose. The individual pose variations are largely attributed to the day-to-day functioning of the patient, such as gait during walk, as well as interactions between specific morphologies and joint alignment. This paper presents a novel two-step method to neutralize such patient-specific variations while simultaneously preserving the inherent relationship of the articulated joint. The resulting shape models are then used to discover clinically relevant shape variations in a population of hip joints.
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http://dx.doi.org/10.1007/978-3-030-61056-2_9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7962350PMC
October 2020

The modified Shriners Hospitals for Children Greenville (mSHCG) multi-segment foot model provides clinically acceptable measurements of ankle and midfoot angles: A dual fluoroscopy study.

Gait Posture 2021 Mar 13;85:258-265. Epub 2021 Feb 13.

Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT 84108, United States; Department of Biomedical Engineering, University of Utah, 72 Central Campus Dr, Salt Lake City, UT 84112, United States; Department of Physical Therapy and Athletic Training, University of Utah, 520 Wakara Way, Suite 240, Salt Lake City, UT 84108, United States; Scientific Computing and Imaging Institute, University of Utah, 72 Central Campus Dr, Salt Lake City, UT 84112, United States. Electronic address:

Background: Several multi-segment foot models have been developed to evaluate foot and ankle motion using skin-marker motion analysis. However, few multi-segment models have been evaluated against a reference standard to establish kinematic accuracy.

Research Question: How accurately do skin-markers estimate foot and ankle motion for the modified Shriners Hospitals for Children Greenville (mSHCG) multi-segment foot model when compared against the reference standard, dual fluoroscopy (DF), during gait, in asymptomatic participants?

Methods: Five participants walked overground as full-body skin-marker trajectory data and DF images of the foot and shank were simultaneously acquired. Using the mSHCG model, ankle and midfoot angles were calculated throughout stance for both motion analysis techniques. Statistical parametric mapping assessed differences in joint angles and marker positions between skin-marker and DF motion analysis techniques. Paired t tests, and linear regression models were used to compare joint angles and range of motion (ROM) calculated from the two techniques.

Results: In the coronal plane, the skin-marker model significantly overestimated ROM (p = 0.028). Further, the DF model midfoot ROM was significantly positively related to differences between DF and skin-marker midfoot angles (p = 0.035, adjusted R = 0.76). In the sagittal plane, skin-markers underestimated ankle angles by as much as 7.26°, while midfoot angles were overestimated by as much as 9.01°. However, DF and skin-marker joint angles were not significantly different over stance. Skin-markers on the tibia, calcaneus, and fifth metatarsal had significantly different positions than the DF markers along the direction of walking for isolated portions that were less than 10 % of stance. Euclidean distances between DF and skin-markers positions were less than 9.36 mm.

Significance: As the accuracy of the mSHCG model was formerly unknown, the results of this study provide ranges of confidence for key angles calculated by this model.
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http://dx.doi.org/10.1016/j.gaitpost.2021.02.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8085108PMC
March 2021

Age-related differences in humerothoracic, scapulothoracic, and glenohumeral kinematics during elevation and rotation motions.

J Biomech 2021 Mar 23;117:110266. Epub 2021 Jan 23.

Department of Orthopaedics, University of Utah, Salt Lake City, UT, United States; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States. Electronic address:

Age affects gross shoulder range of motion (ROM), but biomechanical changes over a lifetime are typically only characterized for the humerothoracic joint. Suitable age-related baselines for the scapulothoracic and glenohumeral contributions to humerothoracic motion are needed to advance understanding of shoulder injuries and pathology. Notably, biomechanical comparisons between younger or older populations may obscure detected differences in underlying shoulder motion. Herein, biplane fluoroscopy and skin-marker motion analysis quantified humerothoracic, scapulothoracic, and glenohumeral motion during 3 static poses (resting neutral, internal rotation to L4-L5, and internal rotation to maximum reach) and 2 dynamic activities (scapular plane abduction and external rotation in adduction). Orientations during static poses and rotations during active ROM were compared between subjects <35 years and >45 years of age (N = 10 subjects per group). Numerous age-related kinematic differences were measured, ranging 5-22°, where variations in scapular orientation and motion were consistently observed. These disparities are on par with or exceed mean clinically important differences and standard error of measurement of clinical ROM, which indicates that high resolution techniques and appropriately matched controls are required to avoid confounding results of studies that investigate shoulder kinematics. Understanding these dissimilarities will help clinicians manage expectations and treatment protocols where indications and prevalence between age groups tend to differ. Where possible, it is advised to select age-matched control cohorts when studying the kinematics of shoulder injury, pathology, or surgical/physical therapy interventions to ensure clinically important differences are not overlooked.
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http://dx.doi.org/10.1016/j.jbiomech.2021.110266DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7924070PMC
March 2021

Inclusion of the Acetabular Labrum Reduces Simulated Range of Motion of the Hip Compared With Bone Contact Models.

Arthrosc Sports Med Rehabil 2020 Dec 6;2(6):e779-e787. Epub 2020 Oct 6.

Department of Orthopaedics, University of Utah, Salt Lake City, Utah, U.S.A.

Purpose: To determine whether inclusion of the acetabular labrum affects the maximum range of motion (ROM) during simulation of the flexion-adduction-internal rotation impingement examination.

Methods: Three-dimensional surface reconstructions of the femur, hemi-pelvis, and labrum from computed tomography arthrography images of 19 participants were used to simulate maximum ROM during the flexion-adduction-internal rotation examination. Simulations were conducted for positions between 70° and 110° flexion and 0° and 20° adduction at 10° increments to measure maximum internal rotation and the position of contact between the femur and acetabular rim (bone-to-bone) or the femur and labrum (bone-to-labrum). Internal rotation angles and clock-face position values were compared between the 2 contact scenarios for each position.

Results: The ROM in the bone-to-labrum contact model was significantly less than that of the bone-to-bone contact model for all evaluated positions ( ≤ .001, except at 110° flexion and 20° adduction,  = .114). The inclusion of the labrum reduced internal rotation by a median [interquartile range] of 18 [15, 25]° while altering the position of contact on the acetabular clock-face by -0:01 [-0:27, 0:16]. The variability in contact location for the bone-to-labrum contact scenario was nearly double that of the bone-to-bone contact scenario, as indicated by the interquartile range.

Conclusions: Inclusion of the anatomy of the acetabular labrum in collision models used to simulate impingement examinations reduced the internal rotation ROM by approximately 20° and increased variability in the location of contact relative to the acetabular rim.

Clinical Relevance: While standard bone-to-bone contact ROM simulations may be informative with respect to the relative change in ROM based on a surgical intervention (e.g., pre- and post-osteochondroplasty for cam-type femoroacetabular impingement), they may not accurately represent the clinical ROM of the joint or the kinematic position at which damage may occur due to shape mismatch between the femur and acetabulum.
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http://dx.doi.org/10.1016/j.asmr.2020.07.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7754612PMC
December 2020

Morphologic analysis of the subtalar joint using statistical shape modeling.

J Orthop Res 2020 12 7;38(12):2625-2633. Epub 2020 Sep 7.

Department of Orthopaedics, University of Utah, Salt Lake City, Utah.

Weightbearing computed tomography (WBCT) enables visualization of the foot and ankle as patients stand under load. Clinical measurements of WBCT images are generally limited to two-dimensions, which reduces the ability to quantify complex morphology of individual osseous structures as well as the alignment between two or more bones. The shape and orientation of the healthy/normal subtalar joint, in particular, is not well-understood, which makes it very difficult to diagnose subtalar pathoanatomy. Herein, we employed statistical shape modeling to evaluate three-dimensional (3D) shape variation, coverage, space, and congruency of the subtalar joint using WBCT data of 27 asymptomatic healthy individuals. The four most relevant findings were: (A) talar and calcaneal anatomical differences were found regarding the presence of (a) the talar posterior process, (b) calcaneal pitch, and (c) curvature of the calcaneal posterior facet; (B) the talar posterior facet articular surface area was significantly greater than the calcaneal posterior facet articular surface area; (C) the posterior facet varied in joint space distance, whereas the anteromedial facet was even; and (D) the posterior and anteromedial facet of the subtalar joint was consistently congruent. Despite considerable shape variation across the population, the posterior and anteromedial articular facets of the subtalar joint were consistently congruent. Results provide a detailed 3D analysis of the subtalar joint under a weightbearing condition in a healthy population which can be used for comparisons to pathological patient populations. The described SSM approach also shows promise for clinical evaluation of the subtalar joint from 3D surface reconstructions of WBCT images.
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http://dx.doi.org/10.1002/jor.24831DOI Listing
December 2020

Reliable interpretation of scapular kinematics depends on coordinate system definition.

Gait Posture 2020 09 25;81:183-190. Epub 2020 Jul 25.

Department of Orthopaedics, University of Utah, Salt Lake City, UT, United States; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, United States. Electronic address:

Background: Interpretation of shoulder motion across studies has been complicated due to the use of numerous scapular coordinate systems in the literature. Currently, there are no simple means by which to compare scapular kinematics between coordinate system definitions when data from only one coordinate system is known.

Research Question: How do scapular kinematics vary based on the choice of coordinate system and can average rotation matrices be used to accurately convert kinematics between scapular local coordinate systems?

Methods: Average rotation matrices derived from anatomic landmarks of 51 cadaver scapulae (29 M/22 F; 59 ± 13 yrs; 26R/25 L; 171 ± 11 cm; 70 ± 19 kg; 23.7 ± 5.5 kg/m) were generated between three common scapular coordinate systems. Absolute angle of rotation was used to determine if anatomical variability within the cadaver population influenced the matrices. To quantify the predictive capability to convert kinematics between the three coordinate systems, the average rotation matrices were applied to scapulothoracic motion data collected from 19 human subjects (10 M/9 F; 43 ± 17 yrs; 19R; 173 ± 9 cm; 71 ± 16 kg; 23.6 ± 4.5 kg/m) using biplane fluoroscopy. Root mean squared error (RMSE) was used to compare kinematics from an original coordinate system to the kinematics expressed in each alternative coordinate system.

Results: The choice of scapular coordinate system resulted in mean differences in scapulothoracic rotation of up to 23°, with overall different shapes and/or magnitudes of the curves. A single average rotation matrix between any two coordinate systems achieved accurate conversion of scapulothoracic kinematics to within 4° of RMSE of the known solution. The average rotation matrices were independent of sex, side, decomposition sequence, and motion.

Significance: Scapulothoracic kinematic representations vary in shape and magnitude based solely on the choice of local coordinate system. The results of this study enhance interpretability and reproducibility in expressing scapulothoracic motion data between laboratories by providing a simple means to convert data between common coordinate systems. This is necessitated by the variety of available motion analysis techniques and their respective scapular landmark definitions.
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http://dx.doi.org/10.1016/j.gaitpost.2020.07.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7484087PMC
September 2020

Soft tissue artifact causes underestimation of hip joint kinematics and kinetics in a rigid-body musculoskeletal model.

J Biomech 2020 07 13;108:109890. Epub 2020 Jun 13.

Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT 84108, USA; Department of Bioengineering, University of Utah, 36 S. Wasatch Drive, Room 3100, Salt Lake City, UT 84112, USA; Scientific Computing and Imaging Institute, University of Utah, 72 S. Central Campus Drive, Room 3750, Salt Lake City, UT 84112, USA. Electronic address:

Rigid body musculoskeletal models have been applied to study kinematics, moments, muscle forces, and joint reaction forces in the hip. Most often, models are driven with segment motions calculated through optical tracking of markers adhered to the skin. One limitation of optical tracking is soft tissue artifact (STA), which occurs due to motion of the skin surface relative to the underlying skeleton. The purpose of this study was to quantify differences in musculoskeletal model outputs when tracking body segment positions with skin markers as compared to bony landmarks measured by direct imaging of bone motion with dual fluoroscopy (DF). Eleven asymptomatic participants with normally developed hip anatomy were imaged with DF during level treadmill walking at a self-selected speed. Hip joint kinematics and kinetics were generated using inverse kinematics, inverse dynamics, static optimization and joint reaction force analysis. The effect of STA was assessed by comparing the difference in estimates from simulations based on skin marker positions (SM) versus virtual markers on bony landmarks from DF. While patterns were similar, STA caused underestimation of kinematics, range of motion (ROM), moments, and reaction forces at the hip, including flexion-extension ROM, maximum internal rotation joint moment and peak joint reaction force magnitude. Still, kinetic differences were relatively small, and thus they may not be relevant nor clinically meaningful.
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http://dx.doi.org/10.1016/j.jbiomech.2020.109890DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7405358PMC
July 2020

Methodology for Measurement of Tibiotalar Kinematics After Total Ankle Replacement Using Dual Fluoroscopy.

Front Bioeng Biotechnol 2020 5;8:375. Epub 2020 May 5.

Orthopaedic Research Laboratory, Department of Orthpaedics, University of Utah, Salt Lake City, UT, United States.

Biomechanical data could improve our clinical understanding of failures in total ankle replacement (TAR) patients, leading to better surgical approaches and implant designs. Kinematics of the prosthetic tibiotalar joint in TAR patients have yet to be measured using dual fluoroscopy. With dual fluoroscopy, computed tomography (CT) images are acquired to track bone motion. One challenge with this approach is dealing with metal artifact in the CT images that distorts implant visualization and the surrounding bone to implant interfaces. The aim of this study was to develop a methodology to measure TAR kinematics using inputs of computer-aided design (CAD) models, dual fluoroscopy and CT imaging with metal artifact reduction. To develop this methodology, we created a hybrid three-dimensional (3D) model that contained both: (1) the segmented bone; and (2) the CAD models of the TAR components. We evaluated a patient following total ankle replacement to demonstrate feasibility. The patient performed a self-selected overground walk during which dual fluoroscopy images were collected at 200 Hz. tracking verifications were performed during overground walking using a distance calculation between the implant articular surfaces to evaluate the model-based tracking 3D solution. Tracking verification indicated realistic alignment of the hybrid models with an evenly distributed distance map pattern during the trial. Articular surface distance calculations were reported as an average of 1.3 mm gap during the entirety of overground walking. The successful implementation of our new tracking methodology with a hybrid model presents a new approach to evaluate TAR kinematics. Measurements of kinematics could improve our clinical understanding of failures in TAR patients, leading to better long-term surgical outcomes.
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http://dx.doi.org/10.3389/fbioe.2020.00375DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7214754PMC
May 2020

A Combined Geometric Morphometric and Discrete Element Modeling Approach for Hip Cartilage Contact Mechanics.

Front Bioeng Biotechnol 2020 21;8:318. Epub 2020 Apr 21.

Department of Orthopaedics, University of Utah, Salt Lake City, UT, United States.

Finite element analysis (FEA) provides the current reference standard for numerical simulation of hip cartilage contact mechanics. Unfortunately, the development of subject-specific FEA models is a laborious process. Owed to its simplicity, Discrete Element Analysis (DEA) provides an attractive alternative to FEA. Advancements in computational morphometrics, specifically statistical shape modeling (SSM), provide the opportunity to predict cartilage anatomy without image segmentation, which could be integrated with DEA to provide an efficient platform to predict cartilage contact stresses in large populations. The objective of this study was, first, to validate linear and non-linear DEA against a previously validated FEA model and, second, to present and evaluate the applicability of a novel population-averaged cartilage geometry prediction method against previously used methods to estimate cartilage anatomy. The population-averaged method is based on average cartilage thickness maps and therefore allows for a more accurate and individualized cartilage geometry estimation when combined with SSM. The root mean squared error of the population-averaged cartilage geometry predicted by SSM as compared to the manually segmented cartilage geometry was 0.31 ± 0.08 mm. Identical boundary and loading conditions were applied to the DEA and FEA models. Predicted DEA stress distribution patterns and magnitude of peak stresses were in better agreement with FEA for the novel cartilage anatomy prediction method as compared to commonly used parametric methods based on the estimation of acetabular and femoral head radius. Still, contact stress was overestimated and contact area was underestimated for all cartilage anatomy prediction methods. Linear and non-linear DEA methods differed mainly in peak stress results with the non-linear definition being more sensitive to detection of high peak stresses. In conclusion, DEA in combination with the novel population-averaged cartilage anatomy prediction method provided accurate predictions while offering an efficient platform to conduct population-wide analyses of hip contact mechanics.
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http://dx.doi.org/10.3389/fbioe.2020.00318DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7186355PMC
April 2020

Can measurements from an anteroposterior radiograph predict pelvic sagittal inclination?

J Orthop Res 2020 07 30;38(7):1477-1485. Epub 2020 Apr 30.

Department of Orthopaedics, University of Utah, Salt Lake City, Utah.

Pelvic sagittal inclination (PSI) is often evaluated in patients with hip pathology using lateral radiographs. However, it would be useful if PSI could be predicted from an anteroposterior radiograph since this film is ubiquitous in the evaluation of hip pathology. Herein, computer-modeling was applied to predict PSI from radiographic measurements assessed in the anteroposterior plane. Three-dimensional surface models of the pelvis, femur, and sacrum were reconstructed from computed tomography images of 50 women with hip dysplasia. This study cohort was selected as changes in PSI alter femoral head coverage, which is relevant to the diagnosis and treatment of hip dysplasia, a known cause of hip osteoarthritis. Five radiographic parameters commonly used to independently estimate PSI were evaluated after bone surfaces were projected to an anteroposterior plane, including the symphysis to sacrococcygeal joint distance (S-S distance), the pelvic foramen aspect ratio (PF ratio), the distance between the symphysis and a line connecting the femoral head centers (S-H distance), the sacro-femoral-pubic angle (SFP angle), and the pelvic vertical ratio (PVR). Regression models determined the ability of these parameters to predict PSI from -20° to 20° at 1° increment. All five parameters showed a strong correlation with the PSI (all r > 0.9). From the regression models, PSI was estimated with a median (maximum) absolute error of 3.6° (18.4°), 3.8° (17.7°), 5.2° (17.9°), 5.8° (28.8°), and 3.2° (23.5°) for the S-S distance, PF ratio, S-H distance, SFP angle, and PVR, respectively. The regression model for S-S distance had a mean slope of 2.18 that ranged from 1.98 to 2.41 when the sacrococcygeal joint was located superior to the symphysis. Results indicated that substantial errors occur when estimating the actual value of PSI from an anteroposterior radiograph. However, the change in PSI could be estimated from the S-S distance, which may aid surgeons to successfully increase head coverage through periacetabular osteotomy and to locate the acetabular cup in a functional position for total hip arthroplasty.
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http://dx.doi.org/10.1002/jor.24701DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7335595PMC
July 2020

Compensatory Motion of the Subtalar Joint Following Tibiotalar Arthrodesis: An in Vivo Dual-Fluoroscopy Imaging Study.

J Bone Joint Surg Am 2020 Apr;102(7):600-608

Departments of Orthopaedics (A.L.L., J.A.N., K.E.R., A.B., C.L.S., and A.E.A.), Physical Therapy & Athletic Training (K.B.F. and A.E.A.), and Bioengineering and Biomedical Imaging (K.E.R. and A.E.A.), and the Scientific Computing & Imaging Institute (A.E.A.), University of Utah, Salt Lake City, Utah.

Background: Tibiotalar arthrodesis is a common treatment for end-stage tibiotalar osteoarthritis, and is associated with a long-term risk of concomitant subtalar osteoarthritis. It has been clinically hypothesized that subtalar osteoarthritis following tibiotalar arthrodesis is the product of compensatory subtalar joint hypermobility. However, in vivo measurements of subtalar joint motion following tibiotalar arthrodesis have not been quantified. Using dual-fluoroscopy motion capture, we tested the hypothesis that the subtalar joint of the limb with a tibiotalar arthrodesis would demonstrate differences in kinematics and increased range of motion compared with the subtalar joint of the contralateral, asymptomatic, untreated ankle.

Methods: Ten asymptomatic patients who had undergone unilateral tibiotalar arthrodesis at a mean (and standard deviation) of 4.0 ± 1.8 years previously were evaluated during overground walking and a double heel-rise task. The evaluation involved markerless tracking with use of dual fluoroscopy integrated with 3-dimensional computed tomography, which allowed for dynamic measurements of subtalar and tibiotalar dorsiflexion-plantar flexion, inversion-eversion, and internal-external rotation. Range of motion, stance time, swing time, step length, and step width were also measured.

Results: During the early stance phase of walking, the subtalar joint of the limb that had been treated with arthrodesis was plantar flexed (-4.7° ± 3.3°), whereas the subtalar joint of the untreated limb was dorsiflexed (4.6° ± 2.2°). Also, during the early stance phase of walking, eversion of the subtalar joint of the surgically treated limb (0.2° ± 2.3°) was less than that of the untreated limb (4.5° ± 3.2°). During double heel-rise, the treated limb exhibited increased peak subtalar plantar flexion (-7.1° ± 4.1°) compared with the untreated limb (0.2° ± 1.8°).

Conclusions: A significant increase in subtalar joint plantar flexion was found to be a primary compensation during overground walking and a double heel-rise activity following tibiotalar arthrodesis.

Clinical Relevance: Significant subtalar joint plantar flexion compensations appear to occur following tibiotalar arthrodesis. We found an increase in subtalar plantar flexion and considered the potential relationship of this finding with the increased rate of subtalar osteoarthritis that occurs following ankle arthrodesis.
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http://dx.doi.org/10.2106/JBJS.19.01132DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7289138PMC
April 2020

The effect of pelvic tilt on three-dimensional coverage of the femoral head: A computational simulation study using patient-specific anatomy.

Anat Rec (Hoboken) 2021 02 4;304(2):258-265. Epub 2019 Dec 4.

Department of Orthopaedics, University of Utah, Salt Lake City, Utah.

Improved understanding of how three-dimensional (3D) femoral head coverage changes as the pelvic sagittal inclination (PSI) is altered would advance clinical diagnosis of hip pathoanatomy. Herein, we applied computer modeling of 3D computed tomography reconstructions of the pelvis and proximal femur to quantify relationships between the PSI and regional 3D femoral head coverage. Eleven healthy, young adult participants with typically developed hip anatomy were analyzed. The orientation of the pelvis was altered to define a PSI of -30° to 30° at 1° increments. Hip adduction and rotation were fixed in a standing position, which was measured by direct in vivo imaging of the pelvis and femur bones using dual fluoroscopy. Femoral head coverage was quantified in the anterior, superior, posterior, and inferior regions for each PSI position. Change in coverage was largest in the anterior region (29.8%) and smallest in the superior region (6.5%). Coverage increased linearly in the anterior region as the PSI increased, while a linear decrease was found in the posterior region and the inferior region (all p < .001). The slopes of the regression line for these regions were 0.513, -0.316, and -0.255, respectively. For the superior region, coverage increased when the PSI was altered from -30° to 5° and decreased when the PSI was larger than 5°. Overall, a 1° increase in PSI resulted in an increase of 0.5% in anterior coverage and a decrease of 0.3% in posterior coverage. Our findings provide baseline data that improve understanding of the effect of PSI on femoral coverage.
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http://dx.doi.org/10.1002/ar.24320DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7311050PMC
February 2021

Assessment of Acetabular Morphology Using the Acetabular Anterior Center-Edge Angle on Modified False-Profile Radiographs.

Arthroscopy 2019 11;35(11):3060-3066

Department of Orthopaedics, University of Utah, Salt Lake City, Utah, U.S.A.. Electronic address:

Purpose: To compare radiographic parameters of acetabular morphology between standard and modified false-profile (FP) radiographs.

Methods: Standard and modified FP radiographs were obtained in 225 hips in 200 consecutive patients evaluated for hip pain and suspected femoroacetabular impingement. Radiographs were retrospectively reviewed by 2 readers to determine the anterior center-edge angle (ACEA), as assessed to the sourcil and to the bone edge. Inter-rater reliability of radiographic measurements was assessed using the intraclass correlation coefficient. Measurements were evaluated for normality with the Shapiro-Wilk test, averaged between the 2 readers, and compared between views using the paired Wilcoxon test.

Results: The intraclass correlation coefficient values for standard and modified FP views were 0.923 and 0.932, respectively, measuring to the sourcil and 0.867 and 0.896, respectively, measuring to the lateral bone edge. The median difference in ACEA measurements to the sourcil was 1° between the standard and modified FP view (45° vs 44°, P < .001). The median difference in ACEA measurements to the bone edge was 2° (34° vs 32°, P < .001).

Conclusions: Thirty-five degrees of femoral internal rotation for a modified FP hip radiographic view provides similar clinical information regarding acetabular morphology to that of the standard FP view. Given that the modified FP view also provides better visualization of the anterosuperior head-neck junction cam lesion, the modified FP view may be preferred over the standard FP view in evaluation of hip pain in the young patient.

Level Of Evidence: Level III, retrospective comparative study.
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http://dx.doi.org/10.1016/j.arthro.2019.05.048DOI Listing
November 2019

In Vivo Pelvic and Hip Joint Kinematics in Patients With Cam Femoroacetabular Impingement Syndrome: A Dual Fluoroscopy Study.

J Orthop Res 2020 04 14;38(4):823-833. Epub 2019 Nov 14.

Department of Bioengineering, University of Utah, Salt Lake City, Utah, 84112.

Femoroacetabular impingement syndrome (FAIS) may alter the kinematic function of the hip, resulting in pain and tissue damage. Previous motion analysis studies of FAIS have employed skin markers, which are prone to soft tissue artifact and inaccurate calculation of the hip joint center. This may explain why the evidence linking FAIS with deleterious kinematics is contradictory. The purpose of this study was to employ dual fluoroscopy (DF) to quantify in vivo kinematics of patients with cam FAIS relative to asymptomatic, morphologically normal control participants during various activities. Eleven asymptomatic, morphologically normal controls and seven patients with cam FAIS were imaged with DF during standing, level walking, incline walking, and functional range of motion activities. Model-based tracking calculated the kinematic position of the hip by registering projections of three-dimensional computed tomography models with DF images. Patients with FAIS stood with their hip extended (mean [95% confidence interval], -2.2 [-7.4, 3.1]°, flexion positive), whereas controls were flexed (5.3 [2.6, 8.0]°; p = 0.013). Male patients with cam FAIS had less peak internal rotation than the male control participants during self-selected speed level-walking (-0.2 [-6.5, 6.1]° vs. -9.8 [-12.2, -7.3]°; p = 0.007) and less anterior pelvic tilt at heel-strike of incline (5°) walking (3.4 [-1.0, -7.9]° vs. 9.8 [6.4, 13.2]°; p = 0.032). Even during submaximal range of motion activities, such as incline walking, patients may alter pelvic motion to avoid positions that approximate the cam lesion and the acetabular labrum. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:823-833, 2020.
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http://dx.doi.org/10.1002/jor.24509DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7301904PMC
April 2020

The effect of using different coordinate systems on in-vivo hip angles can be estimated from computed tomography images.

J Biomech 2019 Oct 19;95:109318. Epub 2019 Aug 19.

Department of Orthopaedics, University of Utah, Salt Lake City, UT 84108, USA; Department of Bioengineering, University of Utah, Salt Lake City, UT 84112, USA; Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112, USA; Department of Physical Therapy, University of Utah, Salt Lake City, UT 84108, USA. Electronic address:

Measurements of hip kinematics inherently depend on the coordinate system in which they are derived, yet the effect of the coordinate system definition on calculations of hip angles is not well-understood. Herein, hip angles calculated during dynamic activities were compared using coordinate systems described in the literature. In-vivo kinematic data of 24 participants (13 males) were analyzed during gait and the anterior impingement test using dual fluoroscopy and model-based tracking. Two coordinate systems for the pelvis (anterior pelvic plane, International Society of Biomechanics [ISB]) and three coordinate systems for the femur (table top plane with two definitions of the superior-inferior axis, ISB) were evaluated. Bony landmarks visible on computed tomography (CT) images were identified to establish each coordinate system and used as the basis to calculate differences in hip angles between coordinate system pairs. In the analysis during gait, the maximum differences derived from various coordinate system definitions were 6.7° ± 5.5° for flexion, 7.7° ± 2.1° for rotation, and 5.5° ± 0.7° for adduction. For the anterior impingement test, the differences were 8.1° ± 5.9°, 7.1° ± 1.2°, and 5.3° ± 0.7°, respectively. Landmark-based analysis using CT images could estimate these dynamic differences with errors less than 1.0°. Our results indicate that hip angles can be accurately transformed to angles calculated in different coordinate systems by accounting for the inherent bony anatomy. This information may aid in the interpretation of results across biomechanical studies of the hip.
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http://dx.doi.org/10.1016/j.jbiomech.2019.109318DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6800649PMC
October 2019

Do Your Routine Radiographs to Diagnose Cam Femoroacetabular Impingement Visualize the Region of the Femoral Head-Neck Junction You Intended?

Arthroscopy 2019 06 6;35(6):1796-1806. Epub 2019 May 6.

Department of Orthopaedics, University of Utah, Salt Lake City, Utah, U.S.A.. Electronic address:

Purpose: To use computer models and image analysis to identify the position on the head-neck junction visualized in 10 radiographic views used to quantify cam morphology.

Methods: We generated 97 surface models of the proximal femur from computed tomography scans of 59 control femurs and 38 femurs with cam morphology-a flattening or convexity at the femoral head-neck junction. Each model was transformed to a position that represents the anteroposterior, Meyer lateral, 45° Dunn, modified false-profile, Espié frog-leg, modified 45° Dunn, frog-leg lateral, cross-table, 90° Dunn, and false-profile views. The position on the head-neck junction visualized from each view was identified on the surfaces. This position was then quantified by a clock face generated on the plane of the head-neck junction, in which the 12-o'clock position indicated the superior head-neck junction and the 3-o'clock position indicated the anterior head-neck junction. The mean visualized clock-face position was calculated for all subjects. Analysis was repeated to account for variability in femoral version. A general linear model with repeated measures was used to compare each radiographic view and anteversion angle.

Results: Each radiographic view provided visualization of the mean clock-face position as follows: anteroposterior view, 12:01; Meyer lateral view, 1:08; 45° Dunn view, 1:40; modified false-profile view, 2:01; Espié frog-leg view, 2:14; modified 45° Dunn view, 2:35; frog-leg lateral view, 2:45; cross-table view, 3:00; 90° Dunn view, 3:13; and false-profile view, 3:44. Each view visualized a different position on the clock face (all P < .001). Increasing simulated femoral anteversion by 10° changed the visualized position of the head-neck junction to a more clockwise position (range, 0:07 to 0:29; all P < .001), whereas decreasing anteversion by 10° visualized a more counterclockwise position (range, -0:23 to -0:08; all P < .001).

Conclusions: Ten common radiographic views used to identify cam morphology visualized different clock-face positions of the head-neck junction. Our data will help clinicians to understand the position of the head-neck junction visualized for each radiographic view and make educated decisions in the selection of radiographs acquired in the clinic.

Clinical Relevance: Our findings will aid clinicians in choosing a set of radiographs to capture cam morphology in the assessment of patients with hip pain.
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http://dx.doi.org/10.1016/j.arthro.2018.12.031DOI Listing
June 2019

CORR Insights®: Patient Age and Hip Morphology Alter Joint Mechanics in Computational Models of Patients with Hip Dysplasia.

Clin Orthop Relat Res 2019 05;477(5):1246-1248

A. E. Anderson, University of Utah Orthopaedics, Salt Lake City, UT, USA.

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http://dx.doi.org/10.1097/CORR.0000000000000715DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6494311PMC
May 2019

Ankle strength, muscle size, and adipose content following unilateral tibiotalar arthrodesis.

J Orthop Res 2019 05 28;37(5):1143-1152. Epub 2019 Mar 28.

Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City 84108, Utah.

Tibiotalar arthrodesis is commonly used to treat end-stage ankle osteoarthritis. Post-operative impairments are often attributed to limited ankle motion. However, whether muscular deficits also exist, thereby potentially contributing to impairments, is unknown. This study aimed to identify post-operative deficits in ankle musculature by examining range of motion, strength (maximum isometric ankle joint torque), and leg composition (cross-sectional area of individual tissue types: bone, subcutaneous adipose, intramuscular adipose, muscle). Ten individuals with unilateral tibiotalar arthrodesis participated. Paired t-tests (p < 0.05) identified differences between the fused and contralateral, control limb. The results indicate that individuals with tibiotalar arthrodesis have profound losses of range of motion and strength. Across participants, range of motion in the fused limb was 53.5 ± 11.7%, 66.8 ± 6.3%, 38.2 ± 18.7%, 37.8 ± 13.6% less than the control for dorsiflexion, plantarflexion, inversion, and eversion, respectively. The largest strength deficit was in dorsiflexion, with the fused limb producing 47.2 ± 9.4% less torque than the control. The quantity and quality of muscle tissue was also negatively affected in individuals following tibiotalar arthrodesis. The total cross-sectional area of the fused limb was 11.4 ± 5.4% smaller than the control limb. This change was primarily due to the 16.1 ± 6.7% decrease in muscle cross-sectional area. However, intramuscular adipose was significantly increased. Although the posterior compartment demonstrated a significant decrease in cross-sectional area, when accounting for differences in total cross-sectional area, the relative sizes of the four muscle compartments were consistent between limbs. This cross-sectional study motivates longitudinal research examining muscular deficits and whether these deficits are reversible with exercise and rehabilitation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
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http://dx.doi.org/10.1002/jor.24282DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6557278PMC
May 2019

Musculoskeletal models with generic and subject-specific geometry estimate different joint biomechanics in dysplastic hips.

Comput Methods Biomech Biomed Engin 2019 Feb 20;22(3):259-270. Epub 2019 Jan 20.

a Department of Mechanical Engineering and Materials Science , Washington University in St Louis , St Louis , MO , USA.

Optimizing the geometric complexity of musculoskeletal models is important for reliable yet feasible estimation of joint biomechanics. This study investigated the effects of subject-specific model geometry on hip joint reaction forces (JRFs) and muscle forces in patients with developmental dysplasia of the hip (DDH) and healthy controls. For nine DDH and nine control subjects, three models were created with increasingly subject-specific pelvis geometry, hip joint center locations and muscle attachments. Hip JRFs and muscle forces during a gait cycle were compared among the models. For DDH subjects, resultant JRFs from highly specific models including subject-specific pelvis geometry, joint locations and muscle attachments were not significantly different compared to models using generic geometry in early stance, but were significantly higher in late stance (p = 0.03). Estimates from moderately specific models using CT-informed scaling of generic pelvis geometry were not significantly different from low specificity models using generic geometry scaled with skin markers. For controls, resultant JRFs in early stance from highly specific models were significantly lower than moderate and low specificity models (p ≤ 0.02) with no significant differences in late stance. Inter-model JRF differences were larger for DDH subjects than controls. Inter-model differences for JRF components and muscle forces were similar to resultant JRFs. Incorporating subject-specific pelvis geometry significantly affects JRF and muscle force estimates in both DDH and control groups, which may be especially important for reliable estimation of pathomechanics in dysplastic hips.
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http://dx.doi.org/10.1080/10255842.2018.1550577DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6478547PMC
February 2019

Imaging of the subtalar joint: A novel approach to an old problem.

J Orthop Res 2019 04 12;37(4):921-926. Epub 2019 Feb 12.

Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, Utah, 84108.

Evaluation of the subtalar joint using conventional radiographs is difficult. The purpose of this study was to assess how the posterior facet of the subtalar joint is projected on eight standard radiographic views of the foot and ankle. Weightbearing computed tomography (CT) scans of 27 volunteers without ankle pathology were performed. Eight standard views of the foot and ankle (antero-posterior [AP] view, mortise view, subtalar view, four different Broden views) were reconstructed using digitally reconstructed radiographs (DRRs). The appearance of the posterior facet of the subtalar joint was assessed for each view. In addition, the position of the joint line was projected onto three-dimensional (3-D) models of the calcaneus. We found (i) on the AP view of the ankle joint, the posterior part of the posterior facet is visualized and appears convex (calcaneal side); (ii) on the mortise view of the ankle joint, a slightly more anterior part (compared to the AP view) is visualized and appears either convex or flat; (iii) on the subtalar view, the anterior part of the posterior facet is visualized and appears either convex, flat or concave; and (iv) using the Broden views, the posterior and anterior part of the posterior facet can be visualized. This study clarifies which parts of the posterior facet of the subtalar joint are visualized on eight standard views of the foot and ankle. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
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http://dx.doi.org/10.1002/jor.24220DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7311051PMC
April 2019

Novel model for the induction of postnatal murine hip deformity.

J Orthop Res 2019 01 19;37(1):151-160. Epub 2018 Nov 19.

Department of Orthopaedic Surgery, Washington University School of Medicine, 425 S. Euclid Avenue, Saint Louis, Missouri, 63110.

Acetabular dysplasia is a common, multi-etiological, pre-osteoarthritic (OA) feature that can lead to pain and instability of the young adult hip. Despite the clinical significance of acetabular dysplasia, there is a paucity of small animal models to investigate structural and functional changes that mediate morphology of the dysplastic hip and drive the subsequent OA cascade. Utilizing a novel murine model developed in our laboratory, this study investigated the role of surgically induced unilateral instability of the postnatal hip on the initiation and progression of acetabular dysplasia and impingement up to 8-weeks post-injury. C57BL6 mice were used to develop titrated levels of hip instability (i.e., mild, moderate, and severe instabillity or femoral head resection) at weaning. Joint shape, acetabular coverage, histomorphology, and statistical shape modeling were used to assess quality of the hip following 8 weeks of destabilization. Acetabular coverage was reduced following severe, but not moderate, instability. Moderate instability induced lateralization of the femur without dislocation, whereas severe instability led to complete dislocation and pseudoacetabulae formation. Mild instability did not result in morphological changes to the hip. Removal of the femoral head led to reduced hip joint space volume. These data support the notion that hip instability, driven by mechanical loss-of-function of soft connective tissue, can induce morphometric changes in the growing mouse hip. This work developed a new mouse model to study hip health in the murine adolescent hip and is a useful tool for investigating the mechanical and structural adaptations to hip instability during growth. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
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http://dx.doi.org/10.1002/jor.24146DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6393179PMC
January 2019

Which Two-dimensional Radiographic Measurements of Cam Femoroacetabular Impingement Best Describe the Three-dimensional Shape of the Proximal Femur?

Clin Orthop Relat Res 2019 01;477(1):242-253

P. R. Atkins, J. A. Weiss, S. K. Aoki, C. L. Peters, A. E. Anderson, Department of Orthopaedics, University of Utah, Salt Lake City, UT, USA P. R. Atkins, Y. Shin, R. T. Whitaker, J. A. Weiss, C. L. Peters, A. E. Anderson, Department of Bioengineering, University of Utah, Salt Lake City, UT, USA P. Agrawal, S. Y. Elhabian, R. T. Whitaker, J. A. Weiss, A. E. Anderson, Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT, USA P. Agrawal, S. Y. Elhabian, R. T. Whitaker, J. A. Weiss, School of Computing, University of Utah, Salt Lake City, UT, USA.

Background: Many two-dimensional (2-D) radiographic views are used to help diagnose cam femoroacetabular impingement (FAI), but there is little consensus as to which view or combination of views is most effective at visualizing the magnitude and extent of the cam lesion (ie, severity). Previous studies have used a single image from a sequence of CT or MR images to serve as a reference standard with which to evaluate the ability of 2-D radiographic views and associated measurements to describe the severity of the cam lesion. However, single images from CT or MRI data may fail to capture the apex of the cam lesion. Thus, it may be more appropriate to use measurements of three-dimensional (3-D) surface reconstructions from CT or MRI data to serve as an anatomic reference standard when evaluating radiographic views and associated measurements used in the diagnosis of cam FAI.

Questions/purposes: The purpose of this study was to use digitally reconstructed radiographs and 3-D statistical shape modeling to (1) determine the correlation between 2-D radiographic measurements of cam FAI and 3-D metrics of proximal femoral shape; and 2) identify the combination of radiographic measurements from plain film projections that were most effective at predicting the 3-D shape of the proximal femur.

Methods: This study leveraged previously acquired CT images of the femur from a convenience sample of 37 patients (34 males; mean age, 27 years, range, 16-47 years; mean body mass index [BMI], 24.6 kg/m, range, 19.0-30.2 kg/m) diagnosed with cam FAI imaged between February 2005 and January 2016. Patients were diagnosed with cam FAI based on a culmination of clinical examinations, history of hip pain, and imaging findings. The control group consisted of 59 morphologically normal control participants (36 males; mean age, 29 years, range, 15-55 years; mean BMI, 24.4 kg/m, range, 16.3-38.6 kg/m) imaged between April 2008 and September 2014. Of these controls, 30 were cadaveric femurs and 29 were living participants. All controls were screened for evidence of femoral deformities using radiographs. In addition, living control participants had no history of hip pain or previous surgery to the hip or lower limbs. CT images were acquired for each participant and the surface of the proximal femur was segmented and reconstructed. Surfaces were input to our statistical shape modeling pipeline, which objectively calculated 3-D shape scores that described the overall shape of the entire proximal femur and of the region of the femur where the cam lesion is typically located. Digital reconstructions for eight plain film views (AP, Meyer lateral, 45° Dunn, modified 45° Dunn, frog-leg lateral, Espié frog-leg, 90° Dunn, and cross-table lateral) were generated from CT data. For each view, measurements of the α angle and head-neck offset were obtained by two researchers (intraobserver correlation coefficients of 0.80-0.94 for the α angle and 0.42-0.80 for the head-neck offset measurements). The relationships between radiographic measurements from each view and the 3-D shape scores (for the entire proximal femur and for the region specific to the cam lesion) were assessed with linear correlation. Additionally, partial least squares regression was used to determine which combination of views and measurements was the most effective at predicting 3-D shape scores.

Results: Three-dimensional shape scores were most strongly correlated with α angle on the cross-table view when considering the entire proximal femur (r = -0.568; p < 0.001) and on the Meyer lateral view when considering the region of the cam lesion (r = -0.669; p < 0.001). Partial least squares regression demonstrated that measurements from the Meyer lateral and 90° Dunn radiographs produced the optimized regression model for predicting shape scores for the proximal femur (R = 0.405, root mean squared error of prediction [RMSEP] = 1.549) and the region of the cam lesion (R = 0.525, RMSEP = 1.150). Interestingly, views with larger differences in the α angle and head-neck offset between control and cam FAI groups did not have the strongest correlations with 3-D shape.

Conclusions: Considered together, radiographic measurements from the Meyer lateral and 90° Dunn views provided the most effective predictions of 3-D shape of the proximal femur and the region of the cam lesion as determined using shape modeling metrics.

Clinical Relevance: Our results suggest that clinicians should consider using the Meyer lateral and 90° Dunn views to evaluate patients in whom cam FAI is suspected. However, the α angle and head-neck offset measurements from these and other plain film views could describe no more than half of the overall variation in the shape of the proximal femur and cam lesion. Thus, caution should be exercised when evaluating femoral head anatomy using the α angle and head-neck offset measurements from plain film radiographs. Given these findings, we believe there is merit in pursuing research that aims to develop the framework necessary to integrate statistical shape modeling into clinical evaluation, because this could aid in the diagnosis of cam FAI.
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http://dx.doi.org/10.1097/CORR.0000000000000462DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6345307PMC
January 2019

Three-dimensional femoral head coverage in the standing position represents that measured in vivo during gait.

Clin Anat 2018 Nov 31;31(8):1177-1183. Epub 2018 Oct 31.

Department of Orthopaedics, Harold K. Dunn Orthopaedic Research Laboratory, University of Utah, 590 Wakara Way, Salt Lake City, Utah, 84108, USA.

Individuals with over- or under-covered hips may develop hip osteoarthritis. Femoral head coverage is typically evaluated using radiographs, and/or computed tomography (CT) or magnetic resonance images obtained supine. Yet, these static assessments of coverage may not provide accurate information regarding the dynamic, three-dimensional (3-D) relationship between the femoral head and acetabulum. The objectives of this study were to: (1) quantify total and regional 3-D femoral head coverage in a standing position and during gait, and (2) quantify the relationship between 3-D femoral head coverage in standing to that measured during gait. The kinematic position of the hip during standing and gait was measured in vivo for 11 asymptomatic morphologically normal subjects using dual fluoroscopy and model-based tracking of 3-D CT models. Percent coverage in the standing position and during gait was measured overall and on a regional basis (anterior, superior, posterior, inferior). Coverage in standing was correlated with that measured during gait. For total coverage, very little change in coverage occurred during gait (range: 35.0-36.7%; mean: 36.2%). Coverage at each time point of gait strongly correlated with coverage during standing (r = 0.929-0.989). The regions thought to play an important role in weight bearing (i.e. anterior, superior, posterior) were significantly correlated with coverage in standing during the stance phase. Our results suggest that coverage measured in a standing position is a good surrogate for coverage measured during gait. Clin. Anat. 31:1177-1183, 2018. © 2018 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ca.23262DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599490PMC
November 2018

Hip rotation during standing and dynamic activities and the compensatory effect of femoral anteversion: An in-vivo analysis of asymptomatic young adults using three-dimensional computed tomography models and dual fluoroscopy.

Gait Posture 2018 03 31;61:276-281. Epub 2018 Jan 31.

Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT, 84108, USA; Department of Bioengineering, University of Utah, James LeVoy Sorenson Molecular Biotechnology Building, 36 S. Wasatch Drive, Rm. 3100, Salt Lake City, UT 84112 USA; Department of Physical Therapy, University of Utah, 520 Wakara Way, Suite 240, Salt Lake City, UT 84108, USA; Scientific Computing and Imaging Institute, 72 S Central Campus Drive, Room 3750, Salt Lake City, UT 84112, USA. Electronic address:

Background: Individuals are thought to compensate for femoral anteversion by altering hip rotation. However, the relationship between hip rotation in a neutral position (i.e. static rotation) and dynamic hip rotation is poorly understood, as is the relationship between anteversion and hip rotation.

Research Objective: Herein, anteversion and in-vivo hip rotation during standing, walking, and pivoting were measured in eleven asymptomatic, morphologically normal, young adults using three-dimensional computed tomography models and dual fluoroscopy.

Methods: Using correlation analyses, we: 1) determined the relationship between hip rotation in the static position to that measured during dynamic activities, and 2) evaluated the association between femoral anteversion and hip rotation during dynamic activities. Hip rotation was calculated while standing (static-rotation), throughout gait, as a mean during gait (mean gait rotation), and as a mean (mid-pivot rotation), maximum (max-rotation) and minimum (min-rotation) during pivoting.

Results: Static-rotation (mean ± standard deviation; 11.3° ± 7.3°) and mean gait rotation (7.8° ± 4.7°) were positively correlated (r = 0.679, p = 0.022). Likewise, static-rotation was strongly correlated with mid-pivot rotation (r = 0.837, p = 0.001), max-rotation (r = 0.754, p = 0.007), and min-rotation (r = 0.835, p = 0.001). Strong positive correlations were found between anteversion and hip internal rotation during all of the stance phase (0-60% gait) and during mid- and terminal-swing (86-100% gait) (all r > 0.607, p < 0.05).

Conclusions: Our results suggest that the static position may be used cautiously to express the neutral rotational position of the femur for dynamic movements. Further, our results indicate that femoral anteversion is compensated for by altering hip rotation. As such, both anteversion and hip rotation may be important to consider when diagnosing hip pathology and planning for surgical procedures.
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http://dx.doi.org/10.1016/j.gaitpost.2018.01.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599491PMC
March 2018

Modified False-Profile Radiograph of the Hip Provides Better Visualization of the Anterosuperior Femoral Head-Neck Junction.

Arthroscopy 2018 04 27;34(4):1236-1243. Epub 2017 Dec 27.

Department of Orthopaedics, University of Utah, Salt Lake City, Utah, U.S.A.. Electronic address:

Purpose: The purpose of this study was to quantify the amount of internal femur rotation required to visualize the 12 to 3 o'clock positions of the femoral head-neck junction as seen on the false-profile radiograph.

Methods: Computed tomography (CT) images of the femur were retrospectively reviewed from control subjects and cam femoroacetabular impingement (FAI) patients. Using an automatically determined clockface, the positions between 12 and 3 o'clock were determined. The optimal femoral rotation angle to visualize each clockface position on the femoral head-neck junction was calculated based on the CT surface data.

Results: Fifty-nine control subjects and 38 cam FAI patients were evaluated for this study. The mean (95% confidence interval) internal femur rotation needed to optimally visualize the clockface positions of the femoral head-neck junction on the modified false-profile radiograph were 0.9° (0.8°-1.0°) for 3:00, 10.3° (10.0°-10.6°) for 2:30, 21.6° (21.0°-22.1°) for 2:00, 34.3° (33.6°-35.1°) for 1:30, 49.6° (48.6°-50.4°) for 1:00, 68.4° (67.7°-69.0°) for 12:30, and 90.1° (89.9°-90.4°) for 12:00.

Conclusions: Internal femur rotation of 35° during the false-profile radiograph may better visualize the femoral head-neck junction in the anterosuperior (1 to 2 o'clock) region commonly associated with the cam lesion. From this view, rotation angles between 0° and 90° can be used to visualize other regions of the anterosuperior femoral head-neck junction.

Clinical Relevance: The internal rotation of the affected femur for a modified false-profile radiograph may provide a new radiographic view that can be used to quantify anterosuperior femoral head-neck morphology.
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http://dx.doi.org/10.1016/j.arthro.2017.10.026DOI Listing
April 2018

Application of High-Speed Dual Fluoroscopy to Study In Vivo Tibiotalar and Subtalar Kinematics in Patients With Chronic Ankle Instability and Asymptomatic Control Subjects During Dynamic Activities.

Foot Ankle Int 2017 Nov 11;38(11):1236-1248. Epub 2017 Aug 11.

1 Department of Orthopaedics, University of Utah, Salt Lake City, UT, USA.

Background: Abnormal angular and translational (ie, kinematic) motion at the tibiotalar and subtalar joints is believed to cause osteoarthritis in patients with chronic ankle instability (CAI).

Methods: In this preliminary study the investigators quantified and compared in vivo tibiotalar and subtalar kinematics in 4 patients with CAI (3 women) and 10 control subjects (5 men) using dual fluoroscopy during a balanced, single-leg heel-rise and treadmill walking at 0.5 and 1.0 m/s.

Results: During balanced heel-rise, 69%, 54%, and 66% of mean CAI tibiotalar internal rotation/external rotation (IR/ER), subtalar inversion/eversion, and subtalar IR/ER angles, respectively, were outside the 95% confidence intervals of control subjects. During 0.5-m/s gait, 50% and 60% of mean CAI tibiotalar dorsi/plantarflexion and subtalar IR/ER angles, respectively, were outside the 95% confidence intervals of control subjects. During 1.0-m/s gait, 62%, 65%, and 73% of mean CAI subtalar dorsi/plantarflexion, inversion/eversion, and IR/ER, respectively, were outside the 95% confidence intervals of control subjects. Patients with CAI exhibited less tibiotalar and subtalar translational motion during gait; no clear differences in translations were noted during balanced heel-rise.

Conclusion: Overall, the balanced heel-rise activity exposed more tibiotalar and subtalar kinematic variation between patients with CAI and control subjects. Therefore, weight-bearing activities involving large range of motion, balance, and stability may be best for studying kinematic adaptations in patients with CAI.

Clinical Relevance: These preliminary results suggest that patients with CAI require more tibiotalar external rotation, subtalar eversion, and subtalar external rotation during weight-bearing stability exercises, all with less overall joint translation.
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http://dx.doi.org/10.1177/1071100717723128DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5914166PMC
November 2017

In Vivo Measurements of the Ischiofemoral Space in Recreationally Active Participants During Dynamic Activities: A High-Speed Dual Fluoroscopy Study.

Am J Sports Med 2017 Oct 6;45(12):2901-2910. Epub 2017 Jul 6.

Department of Orthopaedics, University of Utah School of Medicine, Salt Lake City, Utah, USA.

Background: Ischiofemoral impingement (IFI) is a dynamic process, but its diagnosis is often based on static, supine images.

Purpose: To couple 3-dimensional (3D) computed tomography (CT) models with dual fluoroscopy (DF) images to quantify in vivo hip motion and the ischiofemoral space (IFS) in asymptomatic participants during weightbearing activities and evaluate the relationship of dynamic measurements with sex, hip kinematics, and the IFS measured from axial magnetic resonance imaging (MRI).

Study Design: Cross-sectional study; Level of evidence, 3.

Methods: Eleven young, asymptomatic adults (5 female) were recruited. 3D reconstructions of the femur and pelvis were generated from MRI and CT. The axial and 3D IFS were measured from supine MRI. In vivo hip motion during weightbearing activities was quantified using DF. The bone-to-bone distance between the lesser trochanter and ischium was measured dynamically. The minimum and maximum IFS were determined and evaluated against hip joint angles using a linear mixed-effects model.

Results: The minimum IFS occurred during external rotation for 10 of 11 participants. The IFS measured from axial MRI (mean, 23.7 mm [95% CI, 19.9-27.9]) was significantly greater than the minimum IFS observed during external rotation (mean, 10.8 mm [95% CI, 8.3-13.7]; P < .001), level walking (mean, 15.5 mm [95% CI, 11.4-19.7]; P = .007), and incline walking (mean, 15.8 mm [95% CI, 11.6-20.1]; P = .004) but not for standing. The IFS was reduced with extension (β = 0.66), adduction (β = 0.22), and external rotation (β = 0.21) ( P < .001 for all) during the dynamic activities observed. The IFS was smaller in female than male participants for standing (mean, 20.9 mm [95% CI, 19.3-22.3] vs 30.4 mm [95% CI, 27.2-33.8], respectively; P = .034), level walking (mean, 8.8 mm [95% CI, 7.5-9.9] vs 21.1 mm [95% CI, 18.7-23.6], respectively; P = .001), and incline walking (mean, 9.1 mm [95% CI, 7.4-10.8] vs 21.3 mm [95% CI, 18.8-24.1], respectively; P = .003). Joint angles between the sexes were not significantly different for any of the dynamic positions of interest.

Conclusion: The minimum IFS during dynamic activities was smaller than axial MRI measurements. Compared with male participants, the IFS in female participants was reduced during standing and walking, despite a lack of kinematic differences between the sexes. The relationship between the IFS and hip joint angles suggests that the hip should be placed into greater extension, adduction, and external rotation in clinical examinations and imaging, as the IFS measured from static images, especially in a neutral orientation, may not accurately represent the minimum IFS during dynamic motion. Nevertheless, this statement must be interpreted with caution, as only asymptomatic participants were analyzed herein.
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http://dx.doi.org/10.1177/0363546517712990DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6599761PMC
October 2017