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Objectives: To evaluate reliability of measurement techniques for syndesmosis position after operative fixation of distal tibia plafond fracture on weight-bearing computed tomography (WBCT), identify risk factors for syndesmosis malposition, and determine if syndesmosis malposition is associated with higher pain and lower physical function., Design: Prospective cohort study., Setting: Three Level 1 trauma centers., Participants: Twenty-six subjects who underwent open reduction and internal fixation of distal tibia plafond fractures with bilateral ankle WBCT 1 year or greater after injury were included in the study., Intervention: Operative fixation of distal tibia plafond fracture., Main Outcome Measurement: Fibula position in the tibia incisura, injury characteristics, and patient-reported outcomes were the main outcome measurements., Results: Interrater reliability for syndesmosis position measurements were excellent for the Phisitkul technique on both injured and healthy ankles (intraclass correlation coefficients [ICCs]: 0.93-0.98). The Nault technique demonstrated moderate-to-excellent interrater reliability (ICCs: 0.67-0.98), apart from the angle of rotation measurement (ICCs: 0.18-0.67). Sixteen of 26 subjects (62%) had syndesmosis malposition defined as >2 mm difference comparing the tibial-fibular relationship in injured and uninjured ankles using these 2 methods. Patients with syndesmosis malposition reported lower Foot and Ankle Ability Measure: Activities of Daily Living scores; other recorded patient-reported outcomes were not significantly different., Conclusions: Measurement techniques for syndesmosis position on WBCT were reliable after operative fixation of distal tibia plafond fracture. Syndesmosis malposition is common after these injuries and predicted impaired physical function., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: The authors report no conflict of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

This first of a 2-part series of articles recounts the key points presented in a collaborative symposium sponsored jointly by the Arthritis Foundation and the American Orthopaedic Foot & Ankle Society with the intent to survey the state of scientific knowledge related to incidence, diagnosis, pathologic mechanisms, and injection treatment options for osteoarthritis (OA) of the foot and ankle. A meeting was held virtually on December 3, 2021. A group of experts were invited to present brief synopses of the current state of knowledge and research in this area. Part 1 overviews areas of epidemiology and pathophysiology, current approaches in imaging, diagnostic and therapeutic injections, and genetics. Opportunities for future research are discussed. The OA scientific community, including funding agencies, academia, industry, and regulatory agencies, must recognize the needs of patients that suffer from arthritis of foot and ankle. The foot and ankle contain a myriad of interrelated joints and tissues that together provide a critical functionality. When this functionality is compromised by OA, significant disability results, yet the foot and ankle are generally understudied by the research community. Level of Evidence: Level V - Review Article/Expert Opinion., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online., (© The Author(s) 2022.)

This second of a 2-part series of articles recounts the key points presented in a collaborative symposium sponsored jointly by the Arthritis Foundation and the American Orthopaedic Foot & Ankle Society with the intent to survey current treatment options for osteoarthritis (OA) of the foot and ankle. A meeting was held virtually on December 10, 2021. A group of experts were invited to present brief synopses of the current state of knowledge and research in this area. Topics were chosen by meeting organizers, who then identified and invited the expert speakers. Part 2 overviews the current treatment options, including orthotics, non-joint destructive procedures, as well as arthroscopies and arthroplasties in ankles and feet. Opportunities for future research are also discussed, such as developments in surgical options for ankle and the first metatarsophalangeal joint. The OA scientific community, including funding agencies, academia, industry, and regulatory agencies, must recognize the importance to patients of addressing the foot and ankle with improved basic, translational, and clinical research., Level of Evidence: Level V, review article/expert opinion., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online., (© The Author(s) 2022.)

Background: The treatment of ankle osteoarthritis (OA) varies depending on the severity and distribution of the associated joint degeneration. Disease staging is typically based on subjective grading of appearance on conventional plain radiographs, with reported subpar reproducibility and reliability. The purpose of this study was to develop and describe computational methods to objectively quantify radiographic changes associated with ankle OA apparent on low-dose weightbearing CT (WBCT)., Methods: Two patients with ankle OA and 1 healthy control who had all undergone WBCT of the foot and ankle were analyzed. The severity of OA in the ankle of each patient was scored using the Kellgren-Lawrence (KL) classification using plain radiographs. For each ankle, a volume of interest (VOI) was centered on the tibiotalar joint. Initial computation analysis used WBCT image intensity (Hounsfield units [HU]) profiles along lines perpendicular to the subchondral bone/cartilage interface of the distal tibia extending across the entire VOI. Graphical plots of the HU distributions were generated and recorded for each line. These plots were then used to calculate the joint space width (JSW) and HU contrast., Results: The average JSW was 3.89 mm for the control ankle, 3.06 mm for mild arthritis (KL 2), and 1.57 mm for severe arthritis (KL 4). The average HU contrast was 72.31 for control, 62.69 for mild arthritis, and 33.98 for severe arthritis. The use of 4 projections at different locations throughout the joint allowed us to visualize specifically which quadrants have reduced joint space width and contrast., Conclusion: In this technique report, we describe a novel methodology for objective quantitative assessment of OA using JSW and HU contrast., Clinical Relevance: Objective, software-based measurements are generally more reliable than subjective qualitative evaluations. This method may offer a starting point for the development of a more robust OA classification system or deeper understanding of the pathogenesis and response to ankle OA treatment., Competing Interests: Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online., (© The Author(s) 2022.)

Background: Reverse shoulder arthroplasty (RSA) is associated with high rates of midterm complications including scapular notching, implant wear, and mechanical impingement. Scapulo-humeral rhythm (SHR), described by Codman in the 1920's, is defined as the ratio of glenohumeral motion to scapulothoracic motion. SHR is used as an indicator of shoulder dysfunction, as alterations in SHR can have profound implications on shoulder biomechanics. The determination of SHR can be hindered by soft-tissue motion artifacts and high radiation burdens associated with traditional surface marker or fluoroscopic analysis. EOS low dose stereoradiographic imaging analysis utilizing 3D model construction from a 2D X-ray series may offer an alternative modality for characterizing SHR following RSA., Methods: Patients (n=10) underwent an EOS imaging analysis to determine SHR at six and twelve months post-RSA. Leveraging 3D models of the implants, 2D/3D image registration methods were used to calculate relative glenohumeral and scapulothoracic positioning at 60, 90 and 120° of shoulder elevation. Subject-specific SHR curves were assessed and midterm changes in post-RSA SHR associated with follow-up time and motion phase were evaluated. Pearson correlations assessed associations between patient-specific factors and post-RSA SHR., Results: Mean post-RSA SHR was 0.81:1 across subjects during the entire midterm postoperative period. As a cohort, post-RSA SHR was more variable for 60-90° of shoulder motion. SHR for 90-120° of motion decreased (0.43:1) at twelve months post-RSA. Post-RSA SHR could be categorized using three relative motion curve patterns, and was not strongly associated with demographic factors such as BMI. 50% of subjects demonstrated a different SHR relative motion curve shape at twelve months post-RSA, and SHR during the 90120° of motion was found to generally decrease at twelve months., Conclusion: Midterm post-RSA SHR was successfully evaluated using EOS technology, revealing lower SHR values (i.e., greater scapulothoracic motion) compared to normal values reported in the literature. SHR continued to change for some subjects during the midterm post-RSA period, with the greatest change during 90-120° of shoulder motion. Study findings suggest that future post RSA rehabilitation efforts to address elevated scapulothoracic motion may benefit from being patient-specific in nature and targeting scapular stabilization during 90-120° of shoulder motion. Level of Evidence: IV ., (Copyright © The Iowa Orthopaedic Journal 2022.)

Skill assessment in orthopedics has traditionally relied on subjective impressions from a supervising surgeon. The feedback derived from these tools may be limited by bias and other practical issues. Objective analysis of intraoperative fluoroscopic images offers an inexpensive, repeatable, and precise assessment strategy without bias. Assessors generally refrain from using the scores of images obtained throughout the operation to evaluate skill for practical reasons. A new system was designed to facilitate rapid analysis of this fluoroscopy via minimally trained analysts. Four expert and four novice analysts independently measured one objective metric for skill using both a custom analysis software and a commercial alternative. Analysts were able to measure the objective metric three times faster when using the custom software, and without a practical difference in accuracy in comparison to the expert analysts using the commercial software. These results suggest that a well-designed fluoroscopy analysis system can facilitate inexpensive, reliable, and objective assessment of surgical skills., Competing Interests: Disclosure of Interest The authors report that there are no conflict of interests for this work.

Background: Repair of the subscapularis following reverse shoulder arthroplasty (RSA) remains a controversial topic among surgeons. Poor rotator cuff muscle quality is associated with increased musculotendinous stiffness, and the subsequent effect of compromised tissue repair on RSA functional outcomes remains unclear. The objective was to investigate the influence of subscapularis stiffness together with glenoid component lateralization on pre- and postimpingement joint mechanics during external rotation after RSA., Methods: A validated finite element model incorporating the Zimmer Trabecular Metal reverse system was used. The deltoid and subscapularis tendon were tensioned and wrapped around the joint prior to controlled shoulder external rotation. Baseline subscapularis stiffness, determined from cadaveric testing, was varied to 80%, 120% and 140% of baseline, to simulate a range of pliability associated with fatty infiltration and fibrosis. We evaluated the effects of varying subscapularis stiffness and the corresponding variation in joint tension with varying glenosphere lateralization (2, 4, and 10 mm) on the torque required to externally rotate the shoulder and the impingement/subluxation risk., Results: Prior to any impingement, the torques required to externally rotate the shoulder ranged from 22-47 Nm across the range of parameters studied, with the greatest torques required for the 10-mm glenosphere lateralization. The impact of increasing subscapularis stiffness on torque requirements was most pronounced at the 10-mm lateralization, as well. A 20% increase in subscapularis stiffness necessitated a 7%-14% increase in preimpingement torque, whereas a 40% stiffness increase was associated with a 12%-27% increase in torque. Torque was proportional to lateralization. When lateralization was increased from 2 to 4 mm, the preimpingement torque increased by 10%-13%, whereas a 10-mm lateralization necessitated a 35%-62% torque increase relative to 2 mm of lateralization. Increased subscapularis stiffness did not limit impingement-free range of motion or substantially decrease postimpingement subluxation in this model., Discussion: Mechanical gains achieved through lateralization may be hindered by increased torque demands, especially when a stiffer subscapularis is repaired. As lateralization increases subscapularis tension, greater torque is required to externally rotate the shoulder. The torque required for external rotation has been reported between 15-50 Nm. Subscapularis repair with the simulated increases in stiffness requires relative increases in torque that the reconstructed shoulder may not be able to physically produce to rotate the glenohumeral joint, particularly at 10-mm lateralization. These results suggest that subscapularis repair may not be indicated in cases where a lateralized glenoid component is used and the subscapularis is compromised., (Copyright © 2021 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Many orthopedic surgeries involve the challenging integration of fluoroscopic image interpretation with skillful tool manipulation to enable procedures to be performed through less invasive approaches. Simulation has proved beneficial for teaching and improving these skills for residents, but similar benefits have not yet been realized for practicing orthopedic surgeons. A vision is presented to elevate community orthopedic practice and improve patient safety by advancing the use of simulators for training and assessing surgical skills., Methods: Key elements of this vision that are established include 1) methods for the objective and rigorous assessment of the performance of practicing surgeons now exist, 2) simulators are sufficiently mature and sophisticated that practicing surgeons will use them, and 3) practicing surgeons can improve their performance with appropriate feedback and coaching., Results: Data presented indicate that surgical performance can be adequately and comparably measured using structured observations made by experts or non-expert crowds, with the crowdsourcing approach being more expedient and less expensive. Rigorous measures of the surgical result and intermediate objectives obtained semi-automatically from intra-operative fluoroscopic image sequences can distinguish performances of experts from novices. Experience suggests that practicing orthopedic surgeons are open to and can be constructively engaged by a family of mature simulators as a means to evaluate and improve their surgical skills., Conclusions: The results presented support our contention that new objective assessment measures are sufficient for evaluating the performance of working surgeons. The novel class of orthopedic surgical simulators available were tested and approved by practicing physicians. There exists a clear opportunity to combine purpose-designed simulator exercises with virtual coaching to help practicing physicians retain, retrain, and improve their technical skills. This will ultimately reduce cost, increase the quality of care, and decrease complication rates., Clinical Relevance: This vision articulates a means to boost the confidence of practitioners and ease their anxiety so that they perform impactful procedures more often in community hospitals, which promises to improve treatment and reduce the cost of care while keeping patients closer to their homes and families., Competing Interests: Disclosures: The authors report no potential conflicts of interest related to this study., (Copyright © The Iowa Orthopaedic Journal 2020.)

Limitations of plain radiographs may contribute to poor sensitivity in the detection of knee osteoarthritis and poor correlation with pain and physical function. 3D joint space width, measured from weight bearing CT images, may yield a more accurate correlation with patients' symptoms. We assessed the cross-sectional association between 3D joint space width and self-reported pain and physical function. 528 knees (57% women) were analyzed from Multicenter Osteoarthritis Study participants. An upright weight bearing CT scanner was used to acquire bilateral, weight-bearing fixed-flexion images of the knees. A 3D dataset was reconstructed from cone beam projections and joint space width was calculated across the joint surface. The percentages of the apposed medial tibiofemoral joint surface with joint space width <2.0mm and <2.5mm respectively were calculated. Pain and physical function were measured using Western Ontario and McMaster Universities Osteoarthritis Index. Participants who reported greater pain severity tended to have a greater joint area with joint space width <2.0mm (p=.07 for the highest vs. the lowest tertile). Participants who reported greater functional limitations had a greater joint area with joint space width <2.0mm (p=.02 for the highest vs. the lowest tertile). There appears to be an association between the medial tibiofemoral area with joint space width <2.0mm and pain and physical function. This article is protected by copyright. All rights reserved., (This article is protected by copyright. All rights reserved.)

Objectives: To quantify fracture severity for a series of displaced intra-articular calcaneal fractures (DIACFs) and to correlate it with Sanders classification, post-traumatic osteoarthritis (PTOA), and patient outcomes., Design: Retrospective review and fracture severity analysis., Setting: Level 1 trauma center affiliated with the University of Iowa in Iowa City, IA., Patients/participants: Thirty-six patients with 48 DIACFs were selected from 153 patients previously treated. All patients 18 years of age and older who had available electronic preop and postop computed tomography (CT) scans, good-quality postop and follow-up radiographs, and a follow-up ≥18 months were selected for study., Intervention: Fractures were treated with percutaneous reduction, using multiple small stab incisions and fluoroscopy to guide manipulation of articular fragments using cork screws or Steinmann pins, with subsequent fixation using 3.5- and 4.0-mm screws., Main Outcome Measurements: Preop CT scans were used to grade fractures according to the Sanders classification and to quantify fracture severity. Fracture severity was objectively quantified using a CT-based measure of fracture energy. PTOA was assessed on follow-up radiographs using the Kellgren-Lawrence scale. Patient outcomes were assessed using the Short Form 36 (SF-36) questionnaire and a visual analog scale pain score., Results: Fracture energies for the 48 DIACFs ranged from 14.1 to 26.2 J (19.3 ± 3.1 J) and correlated with Sanders classification (rho = 0.53, P = 0.0001); type I (16.3 ± 0.9 J); type II (18.0 ± 2.7 J); type III (20.8 ± 2.8 J); and type IV (22.0 ± 0.7 J). Fracture energy was higher for fractures in which the subtalar joint developed PTOA (19.5 ± 2.7 J) than for those that did not (18.9 ± 3.3 J), but the difference did not reach statistical significance. The Sanders classification predicted PTOA risk [odds ratio (OR) = 4.04, 95% confidence interval = 1.43-11.39, P = 0.0084]. No relationship was observed between fracture energy and visual analog scale pain scores. Higher fracture energy correlated with lower SF-36 scores., Conclusions: Fracture energy positively correlates with Sanders classification for DIACFs, which can be used to identify more severe fractures at greater risk of progressing to PTOA., Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background: Women are at greater risk for knee osteoarthritis and numerous other lower limb musculoskeletal disorders. Arch drop during pregnancy and the resultant excessive pronation of the feet may alter loading patterns and contribute to the greater prevalence of knee osteoarthritis in women., Objective: To determine the effect of arch drop on tibial rotation and tibiofemoral contact stress., Design: Interventional study with internal control., Setting: Biomechanics laboratory., Participants: Eleven postpartum women (age 33.4 ± 5.3 years, body mass 76.1 ± 13.5 kg) who had lost arch height with pregnancy in a previous study., Methods: Subjects underwent standing computed tomography (SCT) with their knees in a 20° fixed-flexed position with and without semirigid arch supports to reconstitute prepregnancy arch height. Magnetic resonance imaging of the knee was acquired at a flexion angle equivalent to that of SCT. Bone and cartilage were manually segmented on the magnetic resonance images and segmented surfaces were registered to the 3-dimensional SCT image sets for the arch-supported and -unsupported conditions. These models were used to measure changes in tibial rotation, as well as to estimate contact stress in the medial and lateral tibiofemoral compartments, using computational methods., Main Outcome Measures: Change in tibial rotation and tibiofemoral contact stress with arch drop., Results: Arch drop resulted in a mean tibial internal rotation of 0.75 ± 1.33° (P = .02). Changes in mean or peak contact stress were not detected., Conclusions: Arch drop causes internal tibial rotation, resulting in a shift in the tibiofemoral articulation. An associated increase in contact stress was not detected. Internal rotation of the tibia increases stress on the anterior cruciate ligament and menisci, potentially explaining the greater prevalence of knee disorders in postpartum women., Level of Evidence: NA., (Copyright © 2018 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.)

Background: A previously validated finite element modeling approach was used to determine how changes in glenoid component version and polyethylene liner rotation within the humeral component affect the arm abduction angle at which impingement between the inferior glenoid and the polyethylene liner occurs as well as the amount of subluxation generated by that impingement., Materials and Methods: Five glenoid component versions (5° anteversion; neutral; 5°, 10°, and 20° retroversion) and 7 polyethylene liner rotations (20° and 10° anterior; neutral; 10°, 20°, 30°, and 40° posterior) were considered, resulting in 35 different clinically representative models. The humerus was internally and externally rotated and extended and flexed, and the resulting impingement and subluxation were measured. To further analyze more global trends and to identify implantations least prone to subluxation, polyethylene liner rotation was additionally varied in coarser 30° increments across the entire 360° range., Results: All subluxation caused by impingement occurred during external rotation and extension, and external rotation produced nearly 10-fold more subluxation than extension. Neutral glenoid component version was associated with the least amount of subluxation for all polyethylene liner rotations. Posteriorly rotated polyethylene liners, which place the thick inferior region of the component away from the scapula, produced the least amount of subluxation. The 90° and 120° posterior liner rotations produced no subluxation, whereas the 30° and 60° anterior liner rotations produced the greatest amount of subluxation., Conclusion: These results indicate that rotating modern radially asymmetric humeral polyethylene liners posteriorly can reduce the risk of subluxation leading to dislocation and increase external rotation range of motion., (Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Two categories of joint overloading cause post-traumatic osteoarthritis (PTOA): single acute traumatic loads/impactions and repetitive overloading due to incongruity/instability. We developed and refined three classes of complementary models to define relationships between joint overloading and progressive cartilage loss across the spectrum of acute injuries and chronic joint abnormalities: explant and whole joint models that allow probing of cellular responses to mechanical injury and contact stresses, animal models that enable study of PTOA pathways in living joints and pre-clinical testing of treatments, and patient-specific computational models that define the overloading that causes OA in humans. We coordinated methodologies across models so that results from each informed the others, maximizing the benefit of this complementary approach. We are incorporating results from these investigations into biomathematical models to provide predictions of PTOA risk and guide treatment. Each approach has limitations, but each provides opportunities to elucidate PTOA pathogenesis. Taken together, they help define levels of joint overloading that cause cartilage destruction, show that both forms of overloading can act through the same biologic pathways, and create a framework for initiating clinical interventions that decrease PTOA risk. Considered collectively, studies extending from explants to humans show that thresholds of joint overloading that cause cartilage loss can be defined, that to at least some extent both forms of joint overloading act through the same biologic pathways, and interventions that interrupt these pathways prevent cartilage damage. These observations suggest that treatments that decrease the risk of all forms of OA progression can be discovered. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:515-523, 2017., (© 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

Objective: To determine the test-retest reliability of knee joint space width (JSW) measurements made using standing CT (SCT) imaging., Subjects and Methods: This prospective two-visit study included 50 knees from 30 subjects (66% female; mean ± SD age 58.2 ± 11.3 years; BMI 29.1 ± 5.6 kg/m 2 ; 38% KL grade 0-1). Tibiofemoral geometry was obtained from bilateral, approximately 20° fixed-flexed SCT images acquired at visits 2 weeks apart. For each compartment, the total joint area was defined as the area with a JSW <10 mm. The summary measurements of interest were the percentage of the total joint area with a JSW less than 0.5-mm thresholds between 2.0 and 5.0 mm in each tibiofemoral compartment. Test-retest reliability of the summary JSW measurements was assessed by intraclass correlation coefficients (ICC 2,1) for the percentage area engaged at each threshold of JSW and root-mean-square errors (RMSE) were calculated to assess reproducibility., Results: The ICCs were excellent for each threshold assessed, ranging from 0.95 to 0.97 for the lateral and 0.90 to 0.97 for the medial compartment. RMSE ranged from 1.1 to 7.2% for the lateral and from 3.1 to 9.1% for the medial compartment, with better reproducibility at smaller JSW thresholds., Conclusion: The knee joint positioning protocol used demonstrated high day-to-day reliability for SCT 3D tibiofemoral JSW summary measurements repeated 2 weeks apart. Low-dose SCT provides a great deal of information about the joint while maintaining high reliability, making it a suitable alternative to plain radiographs for evaluating JSW in people with knee OA., Competing Interests: The corresponding author is named as an inventor on a patent application for the positioning frame used in this study, but has neither intellectual property rights nor financial rights to that patent and has not been employed or received honoraria, stock options, or other sources of financial support in relation to this work. The other authors report no conflicts of interest.

Objectives: Determine the agreement between subjective assessments of fracture severity and an objective computed tomography (CT)-based metric of fracture energy in tibial plateau fractures., Methods: Six fellowship-trained orthopaedic trauma surgeons independently rank-ordered 20 tibial plateau fractures in terms of severity based on anteroposterior and lateral knee radiographs. A CT-based image analysis methodology was used to quantify the fracture energy, and agreement between the surgeons' severity rankings and the fracture energy metric was tested by computing their concordance, a statistical measure that estimates the probability that any 2 cases would be ranked with the same ordering by 2 different raters or methods., Results: Concordance between the 6 orthopaedic surgeons ranged from 82% to 93%, and concordance between surgeon severity rankings and the computed fracture energy ranged from 73% to 78%., Conclusions: There is a high level of agreement between experienced surgeons in their assessments of tibial plateau fracture severity, and a slightly lower agreement between the surgeon assessments and an objective CT-based metric of fracture energy. Taken together, these results suggest that experienced surgeons share a similar understanding of what makes a tibial plateau fracture more or less severe, and an objective CT-based metric of fracture energy captures much but not all of that information. Further research is ongoing to characterize the relationship between surgeon assessments of severity, fracture energy, and the eventual clinical outcomes for patients with fractures of the tibial plateau., Competing Interests: Thomas Higgins is a member of the Board of Directors of the OTA, has stock ownership in Orthogrid and Summit Med Ventures, and is a paid consultant for DePuy Synthes. Todd McKinley is a paid consultant for Bioventus. The remaining authors have no declared conflicts.

Objective: There are no widely accepted, objective, and reliable tools for measuring surgical skill in the operating room (OR). Ubiquitous video and imaging technology provide opportunities to develop metrics that meet this need. Hip fracture surgery is a promising area in which to develop these measures because hip fractures are common, the surgery is used as a milestone for residents, and it demands technical skill. The study objective is to develop meaningful, objective measures of wire navigation performance in the OR., Design: Resident surgeons wore a head-mounted video camera while performing surgical open reduction and internal fixation using a dynamic hip screw. Data collected from video included: duration of wire navigation, number of fluoroscopic images, and the degree of intervention by the surgeon׳s supervisor. To determine reliability of these measurements, 4 independent raters performed them for 2 cases. Raters independently measured the tip-apex distance (TAD), which reflects the accuracy of the surgical placement of the wire, on all the 7 cases., Setting: University of Iowa Hospitals and Clinics in Iowa City, IA-a public tertiary academic center., Participants: In total 7 surgeries were performed by 7 different orthopedic residents. All 10 raters were biomedical engineering graduate students., Results: The standard deviations for anteroposterior, lateral, and combined TAD measurements of the 10 raters were 2.7, 1.9, and 3.7mm, respectively, and interrater reliability produced a Cronbach α of 0.97. The interrater reliability analysis for all 9 video-based measures produced a Cronbach α of 0.99., Conclusions: Several video-based metrics were consistent across the 4 video reviewers and are likely to be useful for performance assessment. The TAD measurement was less reliable than previous reports have suggested, but remains a valuable metric of performance. Nonexperts can reliably measure these values and they offer an objective assessment of OR performance., (Copyright © 2016. Published by Elsevier Inc.)

Background: Post-traumatic osteoarthritis (PTOA) is common after intra-articular fractures of the tibial plafond. An objective CT-based measure of fracture severity was previously found to reliably predict whether PTOA developed following surgical treatment of such fractures. However, the extended time required obtaining the fracture energy metric and its reliance upon an intact contralateral limb CT limited its clinical applicability. The objective of this study was to establish an expedited fracture severity metric that provided comparable PTOA predictive ability without the prior limitations., Methods: An expedited fracture severity metric was computed from the CT scans of 30 tibial plafond fractures using textural analysis to quantify disorder in CT images. The expedited method utilized an intact surrogate model to enable severity assessment without requiring a contralateral limb CT. Agreement between the expedited fracture severity metric and the Kellgren-Lawrence (KL) radiographic OA score at two-year follow-up was assessed using concordance. The ability of the metric to differentiate between patients that did or did not develop PTOA was assessed using the Wilcoxon Ranked Sum test., Results: The expedited severity metric agreed well (75.2% concordance) with the KL scores. The initial fracture severity of cases that developed PTOA differed significantly (p = 0.004) from those that did not. Receiver operating characteristic analysis showed that the expedited severity metric could accurately predict PTOA outcome in 80% of the cases. The time required to obtain the expedited severity metric averaged 14.9 minutes/ case, and the metric was obtained without using an intact contralateral CT., Conclusion: The expedited CT-based methods for fracture severity assessment present a solution to issues limiting the utility of prior methods. In a relatively short amount of time, the expedited methodology provided a severity score capable of predicting PTOA risk, without needing to have the intact contralateral limb included in the CT scan. The described methods provide surgeons an objective, quantitative representation of the severity of a fracture. Obtained prior to the surgery, it provides a reasonable alternative to current subjective classification systems. The expedited severity metric offers surgeons an objective means for factoring severity of joint insult into treatment decision-making.

Background: Scapular notching in reverse shoulder arthroplasty occurs in up to 97% of patients. Notching is associated with decreased strength and reduced motion and may lead to long-term failure due to polyethylene wear. Many implant systems lateralize the glenosphere to address scapular notching, but the mechanical tradeoffs of lateralization have not been rigorously evaluated. We hypothesized that lateralization would decrease bony impingement but also decrease the mechanical advantage of the deltoid., Methods: Finite element models were created using the same implants with different amounts of glenoid lateralization: 5 mm of medialization to replicate glenoid erosion, as well as 2.5, 5, 7.5, and 10 mm of lateralization. Tests were performed with static and dynamic scapulae for motion in either the coronal or scapular plane. The angle of impingement between the scapula and the humeral polyethylene was recorded, as was the deltoid force required to elevate the arm., Results: Increasing lateralization decreased impingement while increasing the deltoid force required to elevate the arm. Differences were found between the static and dynamic scapulae, with the dynamic scapula model having increased humeral adduction before impinging. The impingement angle was also substantially affected by the bony prominences on the inferior scapula, showing how individual bony anatomy can affect impingement., Conclusion: Lateralization is effective in increasing impingement-free range of motion but also increases the deltoid force required to perform identical tasks. In addition, impingement is determined by scapular motion, which should be included in all shoulder models., (Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Acute injury severity, altered joint kinematics, and joint incongruity are three important mechanical factors linked to post-traumatic osteoarthritis (PTOA). Finite element analysis (FEA) was previously used to assess the influence of increased contact stress due to joint incongruity on PTOA development. While promising agreement with PTOA development was seen, the inherent complexities of contact FEA limited the numbers of subjects that could be analyzed. Discrete element analysis (DEA) is a simplified methodology for contact stress computation, which idealizes contact surfaces as a bed of independent linear springs. In this study, DEA was explored as an expedited alternative to FEA contact stress exposure computation. DEA was compared to FEA using results from a previously completed validation study of two cadaveric human ankles, as well as a previous study of post-operative contact stress exposure in 11 patients with tibial plafond fracture. DEA-computed maximum contact stresses were within 19% of those experimentally measured, with 90% of the contact area having computed contact stress values within 1MPa of those measured. In the 11 fractured ankles, maximum contact stress and contact area differences between DEA and FEA were 0.85 ± 0.64 MPa and 22.5 ± 11.5mm(2). As a predictive measure for PTOA development, both DEA and FEA had 100% concordance with presence of OA (KL grade ≥ 2) and >95% concordance with KL grade at 2 years. These results support DEA as a reasonable alternative to FEA for computing contact stress exposures following surgical reduction of a tibial plafond fracture., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Animal cells strictly control the distribution of cholesterol in their organelle membranes. This regulation requires an efficient machinery to transport insoluble cholesterol between organelles. In the present study, we generate an (125)I-labeled mutant version of Perfringolysin O (PFO), a cholesterol-binding protein, and use it to measure cholesterol in the plasma membrane of intact cells. We also purify plasma membranes from the same cells, which allows us to directly relate cholesterol concentration to (125)I-PFO binding. We show that cholesterol is organized in the plasma membrane in a manner that makes it inaccessible to PFO until its concentration exceeds a threshold of 35 mol% of total lipids. This 35% threshold is in striking contrast to the 5% threshold previously found for PFO binding to endoplasmic reticulum membranes. The (125)I-PFO probe also proved useful in monitoring the movement of LDL-derived cholesterol from lysosomes to plasma membranes. Using three different mutant cell lines, we show that this transport requires receptor-mediated uptake of LDL, hydrolysis of LDL-cholesteryl esters in lysosomes, and transfer of the liberated cholesterol to the plasma membrane.

The de novo and salvage dTTP pathways are essential for maintaining cellular dTTP pools to ensure the faithful replication of both mitochondrial and nuclear DNA. Disregulation of dTTP pools results in mitochondrial dysfunction and nuclear genome instability due to an increase in uracil misincorporation. In this study, we identified a de novo dTMP synthesis pathway in mammalian mitochondria. Mitochondria purified from wild-type Chinese hamster ovary (CHO) cells and HepG2 cells converted dUMP to dTMP in the presence of NADPH and serine, through the activities of mitochondrial serine hydroxymethyltransferase (SHMT2), thymidylate synthase (TYMS), and a novel human mitochondrial dihydrofolate reductase (DHFR) previously thought to be a pseudogene known as dihydrofolate reductase-like protein 1 (DHFRL1). Human DHFRL1, SHMT2, and TYMS were localized to mitochondrial matrix and inner membrane, confirming the presence of this pathway in mitochondria. Knockdown of DHFRL1 using siRNA eliminated DHFR activity in mitochondria. DHFRL1 expression in CHO glyC, a previously uncharacterized mutant glycine auxotrophic cell line, rescued the glycine auxotrophy. De novo thymidylate synthesis activity was diminished in mitochondria isolated from glyA CHO cells that lack SHMT2 activity, as well as mitochondria isolated from wild-type CHO cells treated with methotrexate, a DHFR inhibitor. De novo thymidylate synthesis in mitochondria prevents uracil accumulation in mitochondrial DNA (mtDNA), as uracil levels in mtDNA isolated from glyA CHO cells was 40% higher than observed in mtDNA isolated from wild-type CHO cells. These data indicate that unlike other nucleotides, de novo dTMP synthesis occurs within mitochondria and is essential for mtDNA integrity.

Many intra-articular fracture patients eventually experience significant functional deficits, pain, and stiffness from post-traumatic osteoarthritis (PTOA). Over the last several decades, continued refinement of surgical reconstruction techniques has failed to markedly improve patient outcomes. New treatment paradigms are needed - ideally, bio/pharmaceutical. Progress in that direction has been impeded because the pathomechanical etiology of PTOA development is poorly understood. In particular, the relative roles and pathomechanisms of acute joint injury (from the initial trauma) versus chronic contact stress elevation (from residual incongruity) are unknown, primarily because there have been no objective methods for reliably quantifying either of these insult entities. Over the past decade, novel enabling technologies have been developed that provide objective biomechanical indices of injury severity and of chronic contact stress challenge to fractured joint surfaces. The severity of the initial joint injury is indexed primarily on the basis of the energy released in fracture, obtained from validated digital image analysis of CT scans. Chronic contact stress elevations are indexed by patient-specific finite element stress analysis, using models derived from post-reduction CT scans. These new measures, conceived in the laboratory, have been taken through the stage of validation, and then have been applied in studies of intra-articular fracture patients, to relate these biomechanical indices of cartilage insult to the incidence and severity of PTOA This body of work has provided a novel framework for developing and testing new approaches to forestall PTOA following intra-articular fractures.

The pathophysiology of post-traumatic osteoarthritis (PTOA) after intra-articular fractures is poorly understood. Pursuit of a better understanding of this disease is complicated by inability to accurately monitor its onset, progression and severity. Common radiographic methods used to assess PTOA do not provide sufficient image quality for precise cartilage measurements. Double-contrast MDCT is an alternative method that may be useful, since it produces high-quality images in normal ankles. The purpose of this study was to assess this technique's performance in assessing cartilage maintenance in ankles with an intra-articular fracture. Thirty-six tibial plafond fractures were followed over two years, with thirty-one MDCTs being obtained four months after injury, and twenty-two MDCTs after two years. Unfortunately, clinical results with this technique were unreliable due to pathology (presumed arthrofibrosis) and technical problems (pooling of contrast). The arthrofibrosis that developed in many patients inhibited proper joint access and contrast infiltration, although high-quality images were obtained in eleven patients. In this patient subset, in which focal regions of cartilage degeneration could be visualized, thickness could be measured with a high degree of fidelity. While thus useful in selected instances, double-contrast MDCT was too unreliable to be recommended to assess these particular types of injuries.

The reliable assessment of fracture severity plays a critical part in treatment, providing essential information to guide clinical decision-making. However, current classification schemes such as the AO/OTA are constrained by limitations intrinsic to subjective categorical systems. A recently developed objective CT-based assessment methodology quantifies fracture severity by calculating the mechanical energy expended during bony fragmentation. Specifically, fracture energy is determined by comparing the bone free surface area in the fractured limb to that in the intact contralateral limb. Unfortunately, the contralateral limb is not routinely scanned in the course of fracture assessment. Consequently, fracture energy can not be obtained, since there is no datum against which to compare the fractured limb. To facilitate the application of this novel technique to large multi-center and retrospective studies where the intact contralateral CT scan is unavailable, this study aimed to establish a normative, anthropometrically scaled intact bone model to be used as a substitute datum. A mathematical model that estimated free bone surface area along the intact contralateral limb was regressed from a study group of 22 tibial plafond fracture patients. The regressed tibia model provided suitably accurate estimates of the directly measured intact surfaces areas (average error of 15%). The differences between regressed and actual bone surface areas did not ultimately affect the stratification of fracture severity, as fracture energy measures using the regressed model maintained a 0.90 concordance with the original analysis. The results from this study suggest that normative bone surface area can be incorporated into the novel CT-based objective fracture severity assessment technique.

Displaced intra-articular distal radius fractures are difficult to treat, with numerous associated complications. The potential onset of post-traumatic osteoarthritis (OA) is a major concern. The relationship between malreduced intra-articular fracture of the distal radius and subsequent early onset of radiocarpal OA is clinically important, yet poorly understood. To better understand this presumed mechanical relationship, detailed information regarding joint loading, kinematics and associated stress distributions must be obtained. Toward this end, a three-dimensional finite element (3D FE) contact model of the radiocarpal joint has been developed, including the radius, lunate, scaphoid, articulations between these bones and selected soft tissues near the joint. FE model geometry was derived from cryomicrotome sections of a cadaver wrist. Radiocarpal contact stress distributions in the intact and simulated malreduced fracture conditions, previously collected using a cadaveric intra-articular fracture model, are used to establish validity of the computational model. Finally, a section of the distal radius constituting the entire lunate fossa was displaced 1,2 and 3 mm to represent a depressed lunate die-punch fracture.