Warm temperature-triggered developmental reprogramming requires VIL1-mediated, genome-wide H3K27me3 accumulation in Arabidopsis.

Changes in ambient temperature immensely affect developmental programs in many species. Plants adapt to high ambient growth temperature in part by vegetative and reproductive developmental reprogramming, known as thermo-morphogenesis. Thermo-morphogenesis is accompanied by massive changes in the transcriptome upon temperature change. Here, we show that transcriptome changes induced by warm ambient temperature require VERNALIZATION INSENSITIVE 3-LIKE 1 (VIL1), a facultative component of the Polycomb repressive complex PRC2, in Arabidopsis. Warm growth temperature elicits genome-wide accumulation of H3K27me3 and VIL1 is necessary for the warm temperature-mediated accumulation of H3K27me3. Consistent with its role as a mediator of thermo-morphogenesis, loss of function of VIL1 results in hypo-responsiveness to warm ambient temperature. Our results show that VIL1 is a major chromatin regulator in responses to high ambient temperature.

Cemented Hemiarthroplasty Results in Substantial Cost Savings Over Uncemented Hemiarthroplasty for the Treatment of Femoral Neck Fractures in Patients Over 60 Years Old: A Markov Analysis.

BACKGROUND: While there is growing scientific evidence supporting superior outcomes following cemented versus uncemented hip hemiarthroplasty (HHA) in elderly femoral neck fractures (FNFs), the relative cost-effectiveness of this in the United States is unknown. Thus, the purpose of this study was to compare the cost-effectiveness of cemented versus uncemented HHA for the treatment of FNFs in patients > 60 years old in the United States, accounting for postoperative outcomes including periprosthetic fractures. METHODS: A Markov model utilizing Monte Carlo microsimulation was developed to evaluate the outcomes and costs of patients at least 60 years of age (mean ± standard deviation, 84 ± 8 years) undergoing cemented versus uncemented HHA for the treatment of FNFs. Health utility values, transition probabilities, and upfront costs were derived from the published literature. Outcome measures included average total costs associated with each treatment (including those from patients who sustained a periprosthetic fracture), quality-adjusted life-years (QALYs), and the incremental cost-effectiveness ratio (ICER). RESULTS: Mean total costs resulting from cemented and uncemented HHA were $19,462 ± 3,581 and $21,997 ± 3,574, respectively (upfront costs from the published literature were $18,267 for cemented HHA and $16,803 for uncemented HHA). Average QALYs resulting from cemented and uncemented HHA were 4.0 ± 0.7 and 3.1 ± 0.6. The resulting ICER was -$2,688.9/QALY. Cemented HHA was found to be the most cost-effective treatment strategy in 89% of the patients in the Monte Carlo microsimulation model. CONCLUSION: Despite documented higher upfront costs for cemented HHA, the averaged total costs over a 10-year time horizon were $2,534 less for cemented HHA than for uncemented HHA. In addition, cemented HHA resulted in an additional 0.9 QALYs relative to uncemented HHA. The findings of this United States-based study replicate the financial and quality-of-life benefits of cemented HHA for elderly FNFs seen in other health systems.

Monitoring the interplay between transposable element families and DNA methylation in maize.

DNA methylation and epigenetic silencing play important roles in the regulation of transposable elements (TEs) in many eukaryotic genomes. A majority of the maize genome is derived from TEs that can be classified into different orders and families based on their mechanism of transposition and sequence similarity, respectively. TEs themselves are highly methylated and it can be tempting to view them as a single uniform group. However, the analysis of DNA methylation profiles in flanking regions provides evidence for distinct groups of chromatin properties at different TE families. These differences among TE families are reproducible in different tissues and different inbred lines. TE families with varying levels of DNA methylation in flanking regions also show distinct patterns of chromatin accessibility and modifications within the TEs. The differences in the patterns of DNA methylation flanking TE families arise from a combination of non-random insertion preferences of TE families, changes in DNA methylation triggered by the insertion of the TE and subsequent selection pressure. A set of nearly 70,000 TE polymorphisms among four assembled maize genomes were used to monitor the level of DNA methylation at haplotypes with and without the TE insertions. In many cases, TE families with high levels of DNA methylation in flanking sequence are enriched for insertions into highly methylated regions. The majority of the >2,500 TE insertions into unmethylated regions result in changes in DNA methylation in haplotypes with the TE, suggesting the widespread potential for TE insertions to condition altered methylation in conserved regions of the genome. This study highlights the interplay between TEs and the methylome of a major crop species.

Patient Experience and Satisfaction with Telemedicine During Coronavirus Disease 2019: A Multi-Institution Experience.

Introduction: The coronavirus disease 2019 (COVID-19) heralded an unprecedented increase in telemedicine utilization. Our objective was to assess patient satisfaction with telemedicine during the COVID-19 era. Methods: Telemedicine visit data were gathered from Stanford Health Care (Stanford) and the Hospital for Special Surgery (HSS). Patient satisfaction data from HSS were captured from a Press-Ganey questionnaire between April 19, 2020, and December 12, 2020, whereas Stanford data were taken from a novel survey instrument that was distributed to all patients between June 22, 2020, and November 1, 2020. Participants: There were 60,550 telemedicine visits at Stanford, each linked with a postvisit survey. At HSS, there were 66,349 total telemedicine visits with 7,348 randomly linked with a postvisit survey. Main Outcomes and Measures: Two measures of patient satisfaction were used for this study: (1) a patient's "overall visit score" and (2) whether the patient indicated the highest possible "likelihood to recommend" (LTR) score (LTR top box score). Results: The LTR top box percentage at Stanford increased from 69.6% to 74.0% (p = 0.0002), and HSS showed no significant change (p = 0.7067). In the multivariable model, the use of a cell phone (adjusted odds ratio [aOR]: 1.18; 95% confidence interval [CI]: 1.12-1.23) and tablet (aOR: 1.15; 95% CI: 1.07-1.23) was associated with higher overall scores, whereas visits with interrupted connections (aOR: 0.49; 95% CI: 0.42-0.57) or help required to connect (aOR: 0.49; 95% CI: 0.42-0.56) predicted lower patient satisfaction. Conclusions: We present the largest published description of patient satisfaction with telemedicine, and we identify important telemedicine-specific factors that predict increased overall visit score. These include the use of cell phones or tablets, phone reminders, and connecting before the visit was scheduled to begin. Visits with poor connectivity, extended wait times, or difficulty being seen, examined, or understood by the provider were linked with reduced odds of high scores. Our results suggest that attention to connectivity and audio/visual definition will help optimize patient satisfaction with future telemedicine encounters.

The history of orthopaedic surgery in India: from antiquity to present.

Indian orthopedists have a legacy dating back more than 4000 years. Starting with the Harappan civilization, ancient orthopaedic surgeons reduced fractures and conducted therapeutic trepanations. Since then, Indian physicians have pioneered many of the orthopaedic techniques still used today - including the use of prosthetics, fracture tables, and rehabilitative physical therapy. Today, orthopaedic surgeons coexist with traditional Indian bonesetters. Although bonesetting practices can have complication rates as high as 40%, bonesetters still handle a majority of fractures in India and are often culturally preferred. Importantly though, bonesetters are often the only expedient option available in both rural and urban settings.

Operative Fixation of Hip Fractures in Nonagenarians: Is It Safe?

BACKGROUND: With the shift in hip fracture epidemiology toward older individuals as well as the shift in demographics toward nonagenarians, it is important to understand the outcomes of treatment for these patients. METHODS: Geriatric patients (≥65 years old) who underwent surgery for hip fracture were identified in the 2005-2017 National Surgical Quality Improvement Program database and stratified into 2 age groups: <90 and ≥90 years old (nonagenarians). Preoperative and procedural characteristics were compared. Multivariate regressions were used to compare risk for complications and 30-day readmissions. Risk factors for serious adverse events (SAEs) and 30-day mortality in nonagenarians were characterized. RESULTS: This study included 51,327 <90 year olds and 15,798 nonagenarians. Overall rate of SAEs in nonagenarians was 19.89% while in <90 year olds was 14.80%. Multivariate analysis revealed higher risk for blood transfusion (relative risk [RR] = 1.21), death (RR = 1.74), pneumonia (RR = 1.24), and cardiac complications (RR = 1.33) in nonagenarians (all P < .001). Risk factors for SAEs in nonagenarians include American Society of Anesthesiologists ≥3, dependent functional status, admitted from nursing home/chronic/intermediate care, preoperative hypoalbuminemia, and male gender (all P < .05), but not time to surgery (P > .05). In fact, increased time to surgery in nonagenarians was associated with lower risk of 30-day mortality (RR = 0.90, P = .048). CONCLUSION: Overall complication risk after hip fracture fixation in nonagenarians remains relatively low but higher than their younger counterparts. Interestingly, since time to surgery was not associated with adverse outcomes in nonagenarians, the commonly accepted 48-hour operative window may not be critical to this population. Additional time for preoperative medical optimization in this vulnerable population appears prudent.

Cannulated Screw Prominence in Tension Band Wiring of Patella Fractures Increases Fracture Gapping: A Cadaver Study.

BACKGROUND: Transverse patella fractures are often treated with cannulated screws and a figure-of-eight anterior tension band. A common teaching regarding this construct is to recess the screws so that their distal ends do not protrude beyond the patella because doing so may improve biomechanical performance. However, there is a lack of biomechanical or clinical data to support this recommendation. QUESTION: In the treatment of transverse patella fractures, is there a difference between prominent and recessed cannulated screw constructs, supplemented by tension banding, in terms of gap formation from cyclic loading and ultimate load to failure? METHODS: Ten pairs of fresh-frozen cadaver legs (mean donor age, 72 years; range, 64-89 years) were randomized in a pairwise fashion to prominent or standard-length screws. In the prominent screw group, screw length was 15% longer than the measured trajectory, resulting in 4 to 6 mm of additional length. Each patella was transversely osteotomized at its midportion and fixed with screws and an anterior tension band. Gap formation was measured over 40 loaded flexion-extension cycles (90° to 5°). Ultimate load to failure was assessed with a final monotonic test after cyclic loading. Areal bone mineral density (BMD) of each patella was measured with dual energy x-ray absorptiometry (DEXA). There was no difference in BMD between the recessed (1.06 ± 0.262 g/cm) and prominent (1.03 ± 0.197 g/cm) screw groups (p = 0.846). Difference in gap formation was assessed with a Wilcoxon Rank Sum Test. Ultimate load to failure and BMD were assessed with a paired t-test. RESULTS: Patella fractures fixed with prominent cannulated screws demonstrated larger gap formation during cyclic loading. Median gap size at the end of cyclic loading was 0.13 mm (range, 0.00-2.92 mm) for the recessed screw group and 0.77 mm (range, 0.00-7.50 mm) for the prominent screw group (p = 0.039; 95% confidence interval [CI] difference of geometric means, 0.05-2.12 mm). There was no difference in ultimate failure load between the recessed screw (891 ± 258 N) and prominent screw (928 ± 268 N) groups (p = 0.751; 95% CI difference of means, -226 to 301 N). Ultimate failure load was correlated with areal BMD (r = 0.468; p = 0.046). CONCLUSIONS: In this cadaver study, when using cannulated screws and a figure-of-eight tension band to fix transverse patella fractures, prominent screws reduced the construct's ability to resist gap formation during cyclic loading testing. CLINICAL RELEVANCE: This biomechanical cadaver study found that the use of prominent cannulated screws for the fixation of transverse patella fractures increases the likelihood of interfragmentary gap formation, which may potentially increase the risk of fracture nonunion and implant failure. These findings suggest that proximally and distally recessed screws may increase construct stability, which may increase the potential for bony healing. The findings support further laboratory and clinical investigations comparing recessed screws supplemented by anterior tension banding with other repair methods that are in common use, such as transosseous suture repair.

Novel Augmentation Technique for Patellar Tendon Repair Improves Strength and Decreases Gap Formation: A Cadaveric Study.

BACKGROUND: Patellar tendon ruptures commonly are repaired using transosseous patellar drill tunnels with modified-Krackow sutures in the patellar tendon. This simple suture technique has been associated with failure rates and poor clinical outcomes in a modest proportion of patients. Failure of this repair technique can result from gap formation during loading or a single catastrophic event. Several augmentation techniques have been described to improve the integrity of the repair, but standardized biomechanical evaluation of repair strength among different techniques is lacking. QUESTIONS/PURPOSES: The purpose of this study was to describe a novel figure-of-eight suture technique to augment traditional fixation and evaluate its biomechanical performance. We hypothesized that the augmentation technique would (1) reduce gap formation during cyclic loading and (2) increase the maximum load to failure. METHODS: Ten pairs (two male, eight female) of fresh-frozen cadaveric knees free of overt disorders or patellar tendon damage were used (average donor age, 76 years; range, 65-87 years). For each pair, one specimen underwent the standard transosseous tunnel suture repair with a modified-Krackow suture technique and the second underwent the standard repair with our experimental augmentation method. Nine pairs were suitable for testing. Each specimen underwent cyclic loading while continuously measuring gap formation across the repair. At the completion of cyclic loading, load to failure testing was performed. RESULTS: A difference in gap formation and mean load to failure was seen in favor of the augmentation technique. At 250 cycles, a 68% increase in gap formation was seen for the control group (control: 5.96 ± 0.86 mm [95% CI, 5.30-6.62 mm]; augmentation: 3.55 ± 0.56 mm [95% CI, 3.12-3.98 mm]; p = 0.02). The mean load to failure was 13% greater in the augmentation group (control: 899.57 ± 96.94 N [95% CI, 825.06-974.09 N]; augmentation: 1030.70 ± 122.41 N [95% CI, 936.61-1124.79 N]; p = 0.01). CONCLUSIONS: This biomechanical study showed improved performance of a novel augmentation technique compared with the standard repair, in terms of reduced gap formation during cyclic loading and increased maximum load to failure. CLINICAL RELEVANCE: Decreased gap formation and higher load to failure may improve healing potential and minimize failure risk. This study shows a potential biomechanical advantage of the augmentation technique, providing support for future clinical investigations comparing this technique with other repair methods that are in common use such as transosseous suture repair.

Anterior Iliac Crest Bone Graft Harvest Using Acetabular Reamers.

VIDEO AVAILABLE AT: https://ota.org/education/ota-online-resources/video-library-procedures-techniques/anterior-iliac-crest-bone-0.

Dorsal Hook Plating of Patella Fractures With Immediate Range of Motion Results in Reliable Fixation, Low Implant Removal Rates, and Satisfactory Clinical Outcomes.

OBJECTIVES: To evaluate radiographic and clinical patient-reported outcomes following dorsal hook plating of displaced patella fractures with permittance of immediate postoperative active closed chain range of motion. DESIGN: Retrospective review of prospectively collected data. SETTING: Urban academic level 1 trauma center. PATIENT SELECTION CRITERIA: Adult patients with displaced patella fractures (OTA/AO 34C1-3) who underwent dorsal plating with immediate range of motion between 2018 and 2023. OUTCOME MEASURES AND COMPARISONS: Numerical Rating Scale for Pain, Knee Outcome Score (KOS-ADL), Tegner-Lysholm score, radiographic union, and wound complications were collected. RESULTS: Sixty-one patients were included (47 female) with an average age of 63 years (SD 14.7, range 22-86 years). The mean BMI was 24.2 (SD 3.6, range 16.6-33.3). There were 13 34-C2 and 48 34-C3 fractures. All but 2 patients (96.7%) achieved bony union after the index procedure. 89% (n = 54) of patients completed outcome surveys with at least 6-month follow-up. Six patients (9.8%) underwent removal of plate implant at a mean of 15.1 months postoperatively. The mean KOS-ADL score was 91.4, the mean Tegner-Lysholm score was 78.1, and the mean NRS was 2.7. CONCLUSIONS: Dorsal hook plating offers secure fixation to allow early range of motion, reliable fixation with low nonunion and implant failure rates, low implant removal rates, and satisfactory patient-reported outcomes. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Intraosseous Shelf Plate Fixation for Depressed Articular Fragments in Tibial Plateau Fractures: A Technical Trick and Case Series.

SUMMARY: Tibial plateau fractures with severely displaced articular injuries and significant deformity to the surrounding metaphyseal bone (including the hyperextension varus bicondylar pattern) can be challenging to stabilize due to resulting large bone voids uncontained by metaphyseal cortex. The purpose of this report was to describe a technique to support the plateau articular surface in these cases and report on outcomes of a small series. This technique uses a small or mini fragment plate, contoured to function as an intraosseous shelf plate, with the "shelf" portion inserted into the bone beneath the articular surface to support it. This technique provides fixed-angle support to the fragment. There are some advantages of this technique compared to structural allograft, large volume ceramic bone void filler, a spine cage, or other trabecular metal object, including the ability to remove the plate later, ability to tension the plate against the depressed articular surface, ability to place screws or other allograft near the implant, wide availability of the implant, and familiarity of orthopaedic trauma surgeons with placing plates and screws to hold reductions. The technique is particularly useful in patterns with uncontained articular depression and a large metaphyseal void.

Locked plate constructs are not necessarily stiffer than nonlocked constructs: A biomechanical investigation of locked versus nonlocked diaphyseal fixation in a human cadaveric model of nonosteoporotic and osteoporotic distal femoral fractures.

Objectives: The objective of this study was to compare the biomechanical properties of locked and nonlocked diaphyseal fixation in a model of distal femur fractures using osteoporotic and nonosteoporotic human cadaveric bone. Methods: A supracondylar osteotomy was created to mimic a fracture (OTA/AO 33A3) in osteoporotic (n = 4) and nonosteoporotic (n = 5) cadaveric distal femurs. The left and right femurs of each pair were instrumented with a distal femoral locking plate and randomly assigned to have diaphyseal fixation with either locked or nonlocked screws. The construct was cyclically axially loaded, and construct stiffness and load to failure were evaluated. Results: In osteoporotic bone, locked constructs were more stiff than nonlocked constructs (mean 143 vs. 98 N/mm when all time points combined, P < 0.001). However, in nonosteoporotic bone, locked constructs were less stiff than nonlocked constructs (mean 155 N/mm vs. 185 N/mm when all time points combined, P < 0.001). In osteoporotic bone, the average load to failure was greater in the locked group than in the nonlocked group (mean 1159 vs. 991 N, P = 0.01). In nonosteoporotic bone, the average load to failure was greater for the nonlocked group (mean 1348 N vs. 1214 N, P = 0.02). Bone mineral density was highly correlated with maximal load to failure (R2 = 0.92, P = 0.001) and stiffness (R2 = 0.78, P = 0.002) in nonlocked constructs but not in locked constructs. Conclusions: Contrary to popular belief, locked plating constructs are not necessarily stiffer than nonlocked constructs. In healthy nonosteoporotic bone, locked diaphyseal fixation does not provide a stiffer construct than nonlocked fixation. Bone quality has a profound influence on the stiffness of nonlocked (but not locked) constructs in distal femur fractures.

Hip Fracture Repair by the Post-Call Surgeon: A Multicenter Retrospective Review.

INTRODUCTION: The purpose of this study was to evaluate surgeons' ability to perform or supervise a standard operation with agreed-upon radiologic parameters after being on call. METHODS: We reviewed a consecutive series of patients with intertrochanteric hip fractures treated with a fixed angle device at 9 centers and compared corrected tip-apex distance and reduction quality for post-call surgeons versus those who were not. Subgroup analyses included surgeons who operated the night before versus not and attending-only versus resident involved cases. Secondary outcomes included union and perioperative complications. RESULTS: One thousand seven hundred fourteen patients were of average age 77 years. Post-call surgeons treated 823 patients and control surgeons treated 891. Surgical corrected tip-apex distance did not differ between groups: on-call 18 mm versus control 18 mm (P = 0.59). The Garden indices were 160° on the AP and 179° on the lateral in both groups. In 66 cases performed by surgeons who operated the night before, the TAD was 17 mm. No difference was noted in corrected tip-apex distance with and without resident involvement (P = 0.101). No difference was observed in pooled fracture-related complications (P = 0.23). CONCLUSION: Post-call surgeons demonstrated no difference in quality and no increase in complications when performing hip fracture repair the next day compared with surgeons who were not on call.

Long non-coding RNA Malat1 fine-tunes bone homeostasis and repair by orchestrating cellular crosstalk and the ß-catenin-OPG/Jagged1 pathway.

The IncRNA Malat1 was initially believed to be dispensable for physiology due to the lack of observable phenotypes in Malat1 knockout (KO) mice. However, our study challenges this conclusion. We found that both Malat1 KO and conditional KO mice in the osteoblast lineage exhibit significant osteoporosis. Mechanistically, Malat1 acts as an intrinsic regulator in osteoblasts to promote osteogenesis. Interestingly, Malat1 does not directly affect osteoclastogenesis but inhibits osteoclastogenesis in a non-autonomous manner in vivo via integrating crosstalk between multiple cell types, including osteoblasts, osteoclasts and chondrocytes. Our findings substantiate the existence of a novel remodeling network in which Malat1 serves as a central regulator by binding to ß-catenin and functioning through the ß-catenin-OPG/Jagged1 pathway in osteoblasts and chondrocytes. In pathological conditions, Malat1 significantly promotes bone regeneration in fracture healing. Bone homeostasis and regeneration are crucial to well-being. Our discoveries establish a previous unrecognized paradigm model of Malat1 function in the skeletal system, providing novel mechanistic insights into how a lncRNA integrates cellular crosstalk and molecular networks to fine tune tissue homeostasis, remodeling and repair.

Classification and treatment of periprosthetic supracondylar femur fractures.

Locked plating and retrograde nailing are two accepted methods for treatment of periprosthetic distal femur fractures. Each has relative benefits and potential pitfalls. Appropriate patient selection and knowledge of the specific femoral component geometry are required to optimally choose between these two methods. Locked plating may be applied to most periprosthetic distal femur fractures. The fracture pattern, simple or comminuted, will dictate the specific plating technique, compression plating or bridge plating. Nailing requires an open intercondylar box and a distal fragment of enough size to allow interlocking. With proper patient selection and proper techniques, good results can be obtained with either method.

Stability of Intertrochanteric Femur Fractures.

SUMMARY: The stability of intertrochanteric fractures depends upon multiple factors including the fracture displacement, location and pattern, the type of fixation used for stabilization, and the loading that the fracture undergoes postfixation. Traditional classification systems are of limited utility because they typically stratify intertrochanteric fractures as stable or unstable based purely on the fracture pattern without consideration of the stability after fixation. Biomechanical studies evaluating the stability of various fixation constructs should include physiologic loading, including rotation around the axis of the femoral neck, and reproduce clinical failure modes to be clinically relevant. A growing body of evidence indicates that the type of fixation substantially affects postoperative stability of intertrochanteric fractures.

Updated Blocking Techniques for Lower Extremity Medullary Nailing: Beyond the Concavity of Deformity.

Modern blocking techniques are useful to achieve anatomic alignment and stable fixation during end-segment nailing. Whether with screws or drill bits, blocking implants can correct both angular and translational deformities. Understanding the biomechanics of blocking implants allows the surgeon to properly plan their placement based on principles rather than dogma. We use case examples to highlight updates in blocking techniques during acute surgical fixation and chronic deformity correction.

Great debates in trauma biomechanics.

At the 2021 annual meeting of the Orthopaedic Trauma Association, the Basic Science Focus Forum hosted its first ever debate-style symposium focused on biomechanics and fracture repair. The 3 subjects of debate were "Mechanics versus Biology-Which is 'More Important' to Consider?" "Locked Plate versus Forward Dynamization versus Reverse Dynamization-Which Way Should I Go?" and "Sawbones versus Cadaver Models-What Should I Believe Most?" These debates were held because fracture healing is a highly organized synergistic response between biological factors and the local mechanical environment. Multiple studies have demonstrated that both factors play roles in governing bone healing responses, and the causal relationships between the 2 remain unclear. The lack of clarity in this space has led to a spectrum of research with the common goal of helping surgeons make good decisions. Before reading further, the reader should understand that the questions posed in the debate titles are unanswerable and might represent a false choice. Instead, the reader should appreciate that the debates were held to gain a more thorough understanding of these topics based on the current state of the art of experimental and clinical studies, by using an engaging and thought-provoking format.

Apex posterior angulation of the humerus: A characterization of normal sagittal plane anatomy with implications for surgical fixation.

INTRODUCTION: An understanding of the sagittal plane morphology of the humerus is relevant during surgical fixation of humeral fractures but is not well described in the literature. The purpose of this study was to better characterize the native sagittal plane morphology of the humerus. MATERIALS AND METHODS: 170 patients with uninjured full length lateral humerus radiographs were retrospectively evaluated. The angle between the proximal humeral diaphyseal axis and the distal humeral diaphyseal axis was identified and measured. The proximal axis was defined by two points equidistant from the anterior and posterior cortex 10 mm and 100 mm distal to the metaphyseal flare, and the distal axis by two points at 10 mm and 50 mm proximal to the capitellum/trochlea. The relative location of the center of rotation of angulation (CORA) was calculated as a percentage of humeral length. RESULTS: 114 radiographs were included in the analysis (66 right humeri, 48 left humeri). The average apex posterior angulation was 6.5 +/- 2.9°. The CORA occurred at an average of 80% (SD+/-13%) of the length of the humerus (proximal to distal). Total humeral length and absolute distance to CORA were greater in males compared to females (364 ± 50 mm versus 326 ± 30 mm; p<0.001; 290 ± 68 mm versus 260 ± 48 mm; p=0.003), but there were no significant sex differences with respect to magnitude of the apex posterior angulation (p=0.077) or location of CORA as a percentage of total humeral length (p=0.916). There were no statistically significant associations between age and total humeral length (p=0.056), distance to CORA (p=0.130), location of CORA as percentage of total humeral length (p=0.753), or magnitude of angulation (p=0.075). CONCLUSION: An apex posterior bow consistently exists in the distal one-quarter of the humerus that is consistent across ages and between sexes. This normal anatomic bow is important to recognize to avoid an extension malreduction and has implications for implant fit and contouring.