Adjusting 1.5 degree C climate change mitigation pathways in light of adverse new information.

Understanding how 1.5 °C pathways could adjust in light of new adverse information, such as a reduced 1.5 °C carbon budget, or slower-than-expected low-carbon technology deployment, is critical for planning resilient pathways. We use an integrated assessment model to explore potential pathway adjustments starting in 2025 and 2030, following the arrival of new information. The 1.5 °C target remains achievable in the model, in light of some adverse information, provided a broad portfolio of technologies and measures is still available. If multiple pieces of adverse information arrive simultaneously, average annual emissions reductions near 3 GtCO2/yr for the first five years following the pathway adjustment, compared to 2 GtCO2/yr in 2020 when the Covid-19 pandemic began. Moreover, in these scenarios of multiple simultaneous adverse information, by 2050 mitigation costs are 4-5 times as high as a no adverse information scenario, highlighting the criticality of developing a wide range of mitigation options, including energy demand reduction options.

High sensitivity of tropical precipitation to local sea surface temperature.

Precipitation and atmospheric circulation are the coupled processes through which tropical ocean surface temperatures drive global weather and climate1-5. Local sea surface warming tends to increase precipitation, but this local control is difficult to disentangle from remote effects of conditions elsewhere. As an example of such a remote effect, El Niño Southern Oscillation (ENSO) events in the equatorial Pacific Ocean alter precipitation across the tropics. Atmospheric circulations associated with tropical precipitation are predominantly deep, extending up to the tropopause. Shallow atmospheric circulations6-8 affecting the lower troposphere also occur, but the importance of their interaction with precipitation is unclear. Uncertainty in precipitation observations9,10 and limited observations of shallow circulations11 further obstruct our understanding of the ocean's influence on weather and climate. Despite decades of research, persistent biases remain in many numerical model simulations12-18, including excessively wide tropical rainbands14,18, the 'double-intertropical convergence zone problem'12,16,17 and too-weak responses to ENSO15. These biases demonstrate gaps in our understanding, reducing confidence in forecasts and projections. Here we use observations to show that seasonal tropical precipitation has a high sensitivity to local sea surface temperature. Our best observational estimate is an 80 per cent change in precipitation for every gram per kilogram change in the saturation specific humidity (itself a function of the sea surface temperature). This observed sensitivity is higher than in 43 of the 47 climate models studied, and is associated with strong shallow circulations. Models with more realistic (closer to 80%) sensitivity have smaller biases across a wide range of metrics. Our results apply to both temporal and spatial variation, over regions where climatological precipitation is about one millimetre per day or more. Our analyses of multiple independent observations, physical constraints and model data underpin these findings. The spread in model behaviour is further linked to differences in shallow convection, thus providing a focus for accelerated research to improve seasonal forecasts through multidecadal climate projections.

The Incidence of Venous Thromboembolism Following Pelvic and Lower Extremity Trauma Despite Adherence to Modern Prophylactic Protocols.

OBJECTIVES: Describe the incidence of venous thromboembolism (VTE) in patients with pelvic and lower extremity long bone trauma in the setting of modern prophylaxis. DESIGN: Retrospective health-system database study. SETTING: Multi-center health care system. PATIENTS: Database query from 2010 to 2017 identified 11,313 adult trauma patients who received open reduction internal fixation of pelvic, acetabular, femoral neck, or intertrochanteric fractures, or received intramedullary nailing (IMN) of the femoral or tibial shaft. Patients with incomplete prophylaxis, prior history of VTE, coagulopathy, or concomitant lower extremity fracture were excluded. INTERVENTION: Mechanical and chemical VTE prophylaxis following pelvic or lower extremity fracture fixation. MAIN OUTCOME MEASUREMENTS: VTE rates. RESULTS: The overall VTE rate was 0.82% [0.39% deep venous thromboses (DVT); 0.43% pulmonary emboli (PE)]. By procedure, pelvic open reduction and internal fixation (ORIF) and femoral IMN had the highest VTE rates 1.70% (0.98% DVT; 0.78% PE) and 1.33% (0.75% DVT; 0.58% PE), whereas tibial IMN had the lowest incidence of VTE 0.34% (0.17% DVT; 0.17% PE). Among hip fractures, femoral neck ORIF had a VTE rate of 0.98% (0.59% DVT; 0.39% PE), whereas intertrochanteric ORIF had lower rates of 0.59% (0.20% DVT; 0.39% PE). CONCLUSIONS: Despite adherence to modern VTEp protocols, nonpreventable VTE occur in 0.82% of pelvic and lower extremity orthopaedic trauma patients. Incidence ranged between 0.34% and 1.70% depending on injury/fixation method with the highest rate observed in pelvis ORIF followed by femoral IMN. In the era of pay for quality performance, it is important for health systems and auditing agencies to reconcile the difference between preventable and nonpreventable VTEs. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The impact of upright radiographs of midshaft clavicle fractures on treatment recommendations.

Clavicle fractures' treatment recommendations are based on displacement. The goal of this paper is to determine upright clavicle radiographs at initial presentation changes timing and method of treatment. Retrospective study in a level 1 trauma center. 356 patients with clavicle fractures were reviewed. Patients with only supine radiographs (Group 1, 285 patients) were compared to patients with supine and upright radiographs (Group 2, 71 patients). Higher proportion of fractures in the upright vs supine radiographs were displaced 100% or more of the clavicle width, (52.1% vs. 33.5%, p =0.004). Treatment assignment changed from nonoperative to operative treatment more commonly in the Group 2 compared to Group 1 (43.7% vs 21.9%, p =0.019). The most common reason for surgery in Group 1 was presence of continued pain or failure to develop radiographic evidence of callus on serial radiographs (17, 53.1%) as compared to Group 2 (2, 14.2%, p =0.014). In Group 2 the most common cause for treatment change was displacement (12, 85.7%) as compared to Group 1 (15, 46.9%, p =0.014). Patients with upright x-rays are more likely to have a change in treatment because of displacement while patients that had supine x-rays have more delayed/nonunion.

Surgery for Unilateral Sacral Fractures: Are the Indications Clear?

OBJECTIVES: To evaluate unilateral sacral fractures and compare those treated operatively versus nonoperatively to determine indications for surgery. DESIGN: Prospective, multicenter, observational study. SETTING: Sixteen trauma centers. PATIENTS/PARTICIPANTS: Skeletally mature patients with pelvic ring injury and unilateral zone 1 or 2 sacral fractures and without anteroposterior compression injuries. MAIN OUTCOME MEASUREMENTS: Injury plain anteroposterior, inlet, and outlet radiographs and computed tomography scans of the pelvis were evaluated for fracture displacement. RESULTS: Three hundred thirty-three patients with unilateral sacral fractures and a mean age of 41 years with a mean Injury Severity Score of 15 were included. Ninety-two percent sustained lateral compression injuries, and 63% of all fractures were in zone 1. Thirty-three percent of patients were treated operatively, including all without lateral compression patterns. Operative patients were more likely to have zone 2 fractures (54%) and to have posterior cortical displacement (29% vs. 6.2%), both with P < 0.001. Over 60% of all patients had no posterior displacement. Mean rotational displacements comparing the injured side versus the intact side were no different for patients treated operatively compared with those treated nonoperatively. CONCLUSIONS: Most unilateral sacral fractures are minimally or nondisplaced. Many patients with radiographically similar fractures were treated operatively and nonoperatively by different surgeons. This suggests an opportunity to develop consistent indications for treatment. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Does Operative Intervention Provide Early Pain Relief for Patients With Unilateral Sacral Fractures and Minimal or No Displacement?

OBJECTIVES: To compare pain after operative versus nonoperative pelvic ring injuries with unilateral sacral fractures. DESIGN: Prospective, multicenter, observational. SETTING: Sixteen trauma centers. PATIENTS/PARTICIPANTS: Skeletally mature patients with pelvic ring injury and minimally displaced unilateral zone 1 or 2 sacral fractures and without anteroposterior compression injuries. MAIN OUTCOME MEASUREMENTS: Pelvic displacement was documented on injury plain radiographs and computed tomography scans; a 10 point Visual Analog Scale (VAS) was used to evaluate pain was obtained in the anterior and posterior pelvic ring during the time of union (12 weeks). RESULTS: One hundred ninety-four patients with unilateral sacral fractures displaced less than 5 mm, mean age of 38.7, and mean Injury Severity Score of 14.5 were included. Ninety-nine percent had lateral compression injuries, and 62% were in zone 1. Seventy-four percent were treated nonoperatively. Nonoperative patients had more zone 1 fractures (71%, P = 0.004). Nonoperative patients reported mean VAS 2.7 points higher in the posterior pelvis (P = 0.01) and 1.9 points higher anteriorly (P = 0.11) 24 hours after injury compared with patients treated operatively. After 3 months, nonoperative patients reported higher VAS scores than operative patients: 4.0 versus 2.9 posteriorly (P = 0.019) and 3.2 versus 2.3 anteriorly (P = 0.035). CONCLUSIONS: For sacrum fractures with minimal or no displacement, slight differences in the VAS were noted within 24 hours after injury or surgery, but limited differences were seen at 3 months for either operatively treated minimally or undisplaced sacrum fractures. It is unknown whether this represents clinical relevance. These differences were below the minimally important clinical difference for VAS scores for other orthopaedic conditions. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Improving Geriatric Care Processes on Two Medical-Surgical Acute Care Units: A Pilot Study.

The Acute Care for Elders (ACE) Unit model improves cognitive and functional outcomes for hospitalized elders but reaches a small proportion of patients. To disseminate ACE Unit principles, we piloted the "Virtual ACE Intervention" that standardizes care processes for cognition and function without daily geriatrician oversight on two non-ACE units. The Virtual ACE Intervention includes staff training on geriatric assessments for cognition and function and on nurse-driven care algorithms. Completion of the geriatric assessments by nursing staff in patients aged 65 years and older and measures of patient mobility and prevalence of an abnormal delirium screening score were compared preintervention and postintervention. Postintervention, the completion of the assessments for current functional status and delirium improved (62.5% vs. 88.5%, p < .001) and (4.2% vs. 96.5%, p < .001). In a subsample analysis, in the postintervention period, more patients were up to the chair in the past day (36.4% vs. 63.5%, p = .04) and the prevalence of an abnormal delirium screening score was lower (13.6% vs. 4.8%, p = .16). The Virtual ACE Intervention is a feasible model for disseminating ACE Unit principles to non-ACE Units and may lead to increased adherence to care processes and improved clinical outcomes.

Percutaneous Transiliac-Transsacral Screw Fixation of Sacral Fragility Fractures Improves Pain, Ambulation, and Rate of Disposition to Home.

OBJECTIVE: To determine whether percutaneous transiliac-transsacral screw fixation improves pain, ambulation, length of stay, and the rate of disposition to home in patients with sacral fragility fractures. DESIGN: Retrospective cohort study. SETTING: Single academic Level 1 trauma center. PATIENTS/PARTICIPANTS: Elderly patients who presented with an isolated sacral fragility fracture between August 2015 and August 2017. Of the 41 patients included in the study, 16 were treated operatively and 25 were treated nonoperatively. INTERVENTION: Percutaneous transiliac-transsacral screw fixation. MAIN OUTCOME MEASUREMENTS: Pain, ambulation, length of stay, complications, and disposition. RESULTS: Patients treated operatively reported a greater improvement in pain as measured by the visual analog scale (3.9 vs. 0.6 points, P < 0.001). At the time of discharge, 100% of surgically treated patients were able to ambulate compared with 72% in the nonoperative group (P = 0.03). Average distance ambulating at the time of discharge was higher in the operative group (95 vs. 35 ft, P < 0.01). Length of stay was similar between the 2 groups (3.6 days in operative group vs. 4.2 days in nonoperative group, P = 0.5). Of the patients treated operatively, 75% were discharged to home compared with only 20% in the nonoperative group (P < 0.001). There were no complications related to surgery. CONCLUSIONS: Percutaneous transiliac-transsacral screw fixation of sacral fragility fractures lessens pain, improves ambulation, and increases the rate of disposition to home. Further investigation is needed to determine if surgical fixation provides benefit regarding medium- and long-term outcome variables. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Advancing national climate change risk assessment to deliver national adaptation plans.

A wide range of climate vulnerability and risk assessments have been implemented using different approaches at different scales, some with a broad multi-sectoral scope and others focused on single risks or sectors. This paper describes the novel approach to vulnerability and risk assessment which was designed and put into practice in the United Kingdom's Second Climate Change Risk Assessment (CCRA2) so as to build upon its earlier assessment (CCRA1). First, we summarize and critique the CCRA1 approach, and second describe the steps taken in the CCRA2 approach in detail, providing examples of how each was applied in practice. Novel elements of the approach include assessment of both present day and future vulnerability, a focus on the urgency of adaptation action, and a structure focused around systems of receptors rather than conventional sectors. Both stakeholders and reviewers generally regarded the approach as successful in providing advice on current risks and future opportunities to the UK from climate change, and the fulfilment of statutory duty. The need for a well-supported and open suite of impact indicators going forward is highlighted.This article is part of the theme issue 'Advances in risk assessment for climate change adaptation policy'.

The impact of Earth system feedbacks on carbon budgets and climate response.

A number of studies have examined the size of the allowable global cumulative carbon budget compatible with limiting twenty-first century global average temperature rise to below 2°C and below 1.5°C relative to pre-industrial levels. These estimates of cumulative emissions have a number of uncertainties including those associated with the climate sensitivity and the global carbon cycle. Although the IPCC fifth assessment report contained information on a range of Earth system feedbacks, such as carbon released by thawing of permafrost or methane production by wetlands as a result of climate change, the impact of many of these Earth system processes on the allowable carbon budgets remains to be quantified. Here, we make initial estimates to show that the combined impact from typically unrepresented Earth system processes may be important for the achievability of limiting warming to 1.5°C or 2°C above pre-industrial levels. The size of the effects range up to around a 350 GtCO2 budget reduction for a 1.5°C warming limit and around a 500 GtCO2 reduction for achieving a warming limit of 2°C. Median estimates for the extra Earth system forcing lead to around 100 GtCO2 and 150 GtCO2, respectively, for the two warming limits. Our estimates are equivalent to several years of anthropogenic carbon dioxide emissions at present rates. In addition to the likely reduction of the allowable global carbon budgets, the extra feedbacks also bring forward the date at which a given warming threshold is likely to be exceeded for a particular emission pathway.This article is part of the theme issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.

Ten-Year Incidence of High-Energy Geriatric Trauma at a Level 1 Trauma Center.

OBJECTIVES: To examine the characteristics of high-energy geriatric trauma over time. DESIGN: Retrospective chart review. SETTING: Level 1 trauma center. PATIENTS: Demographic, injury, and clinical characteristics were compared between 34,017 patients with geriatric and nongeriatric high-energy trauma from 2005 to 2014 using t test, χ analysis, and negative binomial regression for annual trend in injuries. RESULTS: Geriatric high-energy trauma composed 11.2% of all trauma activations. Patients with geriatric high-energy trauma nearly doubled from the study period of 2005-2014 to previous 10 years (P = 0.0004). Compared with patients with nongeriatric trauma, geriatric high-energy traumas were twice as likely to be due to a fall from height (P < 0.0001), had higher Injury Severity Scores (P < 0.0001), fewer abdominal injuries (P = 0.0011), and have head trauma (P < 0.0001). Fracture patterns were similar between groups. Mortality was higher for all geriatric patients (odds ratio [OR], 4.76; 95% confidence interval [CI], 4.00-5.67), and high-energy mechanisms (OR, 4.71; 95% CI, 3.90-5.68) compared with low-energy mechanisms (OR, 3.00; 95% CI, 2.48-3.62). CONCLUSION: The number of geriatric high-energy traumas has doubled over 10 years. Patients with geriatric trauma are sicker on presentation, based on the Injury Severity Score, and high-energy geriatrics have a 4-fold increase in mortality. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Intraoperative Topical Antibiotics for Infection Prophylaxis in Pelvic and Acetabular Surgery.

OBJECTIVES: To determine if topical vancomycin and tobramycin powder reduces the incidence of surgical site infection after pelvic ring and acetabulum fracture surgery. DESIGN: Retrospective cohort study. SETTING: University of Alabama at Birmingham, Academic Level I Trauma Center. PATIENTS/PARTICIPANTS: Two hundred nineteen patients (140 meeting inclusion criteria) with pelvic and acetabular fractures who underwent open reduction and internal fixation from March 2012 to November 2013. INTERVENTION: One gram vancomycin and 1.2 g tobramycin powder applied deep in the surgical wound of the treatment group. MAIN OUTCOME MEASUREMENTS: Postoperative infection rate. RESULTS: One hundred forty patients were included. Control group (n = 69) and treatment group (n = 71) were similar for sex, age, ethnicity, and body mass index. There was no difference between groups with regards to renal function postoperative day 2 (P = 0.24). The risk of infection was 14.5% and 4.2% (P = 0.04) for the control and treatment groups, respectively. No significant effect of antibiotic treatment was observed overall after adjusting for EBL (odds ratio 0.20, 95% confidence interval, 0.02-1.06). Of note, a nonsignificant 71% increase was observed among those with ≥1 L EBL (odds ratio 1.71, 95% confidence interval, 0.02-147.02). CONCLUSIONS: Topical antibiotics possibly reduce the incidence of surgical site infection after open pelvic and acetabulum fixation without increasing risk of renal impairment. The protective effect of topical antibiotics may be limited to patients with minimal intraoperative blood loss. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Simple mathematical model of sacroiliac screws safe-zone-Easy to implement by pelvic inlet and outlet views.

Percutaneous sacral screw fixation is the mainstay of posterior pelvic ring fixation. This study quantifies the accuracy of fluoroscopic screw placement using post-operative CT scans and redefines the fluoroscopic safe zone using a mathematical calculation obtained from Inlet and outlet images. The authors hypothesized that a mathematical calculation of screw placement within the ala will improve accuracy of screw placement. A retrospective review of consecutive patients admitted to a level 1 trauma center with pelvic fractures fixed with iliosacral screws from January 2011 to December 2014 was performed. Accuracy of screw placement was determined by comparing fluoroscopy to post-operative CT scans. A mathematical calculation of screw position within the sacral ala was applied to determine assess screw position and compared to CT findings. Ninety-four patients with 156 screws met inclusion criteria, of which 50 (32.0%) had a cortical breech on CT. The sensitivity and specificity of the inlet-outlet safe zone using mathematical calculation were 97.1% and 84.0%, respectively. The positive and negative predictive values were 92.7% and 93.3%, respectively. Overall accuracies of the radiographic inlet-outlet and lateral safe zones were 92.9% and 70.0%, respectively (p-value = 0.004). Sacral dysmorphism was not found to be associated with sacral cortical breech. A Simple mathematical calculation (screw position relative to percentage of bone width) on the inlet-outlet provides an accurate way to predict the accuracy of sacroiliac screws. The method is easy to implement, part of the surgery work-flow, and provides higher accuracy than relying on subjective interpretation of inlet, outlet, and lateral images. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1478-1484, 2017.

Large differences in regional precipitation change between a first and second 2 K of global warming.

For adaptation and mitigation planning, stakeholders need reliable information about regional precipitation changes under different emissions scenarios and for different time periods. A significant amount of current planning effort assumes that each K of global warming produces roughly the same regional climate change. Here using 25 climate models, we compare precipitation responses with three 2 K intervals of global ensemble mean warming: a fast and a slower route to a first 2 K above pre-industrial levels, and the end-of-century difference between high-emission and mitigation scenarios. We show that, although the two routes to a first 2 K give very similar precipitation changes, a second 2 K produces quite a different response. In particular, the balance of physical mechanisms responsible for climate model uncertainty is different for a first and a second 2 K of warming. The results are consistent with a significant influence from nonlinear physical mechanisms, but aerosol and land-use effects may be important regionally.

Risk factors for infection after operative fixation of Tibial plateau fractures.

INTRODUCTION: Tibial plateau fractures are challenging to treat due to the high incidence of postoperative infections. Treating physicians should be aware of risk factors for postoperative infection in patients who undergo operative fixation. PATIENTS AND METHODS: A retrospective review was undertaken to identify all patients with tibial plateau fractures over a 10 year period (2003-2012) who underwent open reduction internal fixation. A total of 532 patients were identified who met the inclusion criteria. Several patient and clinical characteristics were recorded, and those variables with a significant association (p<0.05) with postoperative infection after a univariate analysis were further analyzed using a multivariate analysis. RESULTS: Fifty-nine (11.1%) of the 532 patients developed a deep infection. The average length of follow-up for patients was 19.5 months. Methicillin-resistant Staphylococcus aureus was the most common species, and it was isolated in 26 (44.1%) patients. Open fractures, the presence of compartment syndrome, and a Schatzker type IV-VI were found to be independent risk factors for deep infection. CONCLUSIONS: The rate of deep infection remains high after operative fixation of tibial plateau fractures. Patients with risk factors for infection should be counseled on the possibility of reoperation, and surgeons should consider MRSA prophylaxis in those patients who are at higher risk.

Zone 2 sacral fractures managed with partially-threaded screws result in low risk of neurologic injury.

BACKGROUND: Zone 2 sacral fractures account for 34% of sacral fractures with reported neurological deficit in 21-28% of patients. The purpose of this study was to examine the risk factors for neurological injury in zone 2 sacral fractures. The authors hypothesized that partially thread iliosacral screws did not increase incidence of neurologic injury. METHODS: A retrospective review of consecutive patients admitted to a level 1 trauma center with zone 2 sacral fractures requiring surgery from September 2010 to September 2014 was performed. Patients were excluded if no neurologic exam was available after surgery. Fractures were classified according to Denis and presence/absence of comminution through the neural foramen was noted. Fixation schema was recorded (sacral screws or open reduction and internal fixation with posterior tension plate). Any change in post-operative neurological exam was documented as well as exam at last clinic encounter. RESULTS: 90 patients met inclusion criteria, with zone 2 fractures and post-operative neurological exam. No patient with an intact pre-operative neurologic exam had a neurological deficit after surgery. 86 patients (95.6%) were neurologically intact at their last follow-up examination. Four patients (4.4%) had a neurological deficit at final follow-up, all of them had neurological deficit prior to surgery. 81 patients were treated with partially threaded screws of which 1 (1.2%) had neurological deficit at final follow-up. Fifty-seven fractures (63.3%) were simple fractures and 33 fractures (36.7%) were comminuted. All four patients with neurological deficit had comminuted fractures. The association between neurologic deficit in zone 2 sacral fracture and fracture comminution was found to be statistically significant (p-value=0.016). No nonunion was observed in this cohort. CONCLUSIONS: The use of partially threaded screws for zone 2 sacral fractures is associated with low risk for neurologic injury, suggesting that compression through the fracture does not cause iatrogenic nerve damage. The low rate of sacral nonunion can be attributed to compression induced by the use of partially threaded compression screws. There is a strong association between zone 2 comminution and neurologic injury.

Effect of Retrograde Reaming for Tibiotalocalcaneal Arthrodesis on Subtalar Joint Destruction: A Cadaveric Study.

Recent published data have suggested successful union of subtalar and tibiotalar joints without formal debridement during tibiotalocalcaneal (TTC) fusion procedures. Although previous studies have reported on the importance of the proper guidewire starting point and trajectory to obtain appropriate hindfoot alignment for successful fusion, to our knowledge, no studies have quantified the amount of articular damage to the subtalar joint with retrograde reaming. We hypothesized that reaming would destroy >50% of the posterior facet of the subtalar joint. The bilateral lower extremities of 5 cadavers were obtained and the subtalar joints exposed. Retrograde TTC nail guidewires were inserted, and a 12-mm reamer was passed through the subtalar and ankle joints. Pre- and postreaming images of the subtalar joint were obtained to compare the amount of joint destruction after reaming. We found an average of 5.89% articular destruction of the talar posterior facet and an average of 4.01% articular destruction of the posterior facet of the calcaneus. No damage to the middle facets of the subtalar joint was observed. TTC nailing is a successful procedure for ankle and subtalar joint fusion. Published studies have reported successful subtalar union using TTC nailing without formal open debridement of the subtalar joint, preserving the soft tissue envelope. TTC nail insertion using a 12-mm reamer will destroy 5.89% and 4.01% of the respective talar and calcaneal posterior facets of the subtalar joint.

Predicting Reduction in Torsional Strength by Concentric/Eccentric RIA Reaming Normal and Osteoporotic Long Bones (Femurs).

OBJECTIVES: Reamer-irrigator-aspirator (RIA) bone graft harvesting human femurs have resulted in spiral fractures. Recommendations/studies on safe RIA diameter are noncomprehensive/inconclusive. Our purpose was to develop an analytical model to predict % reduction in torsional strength after intramedullary oversize reaming (concentric or eccentric) and to test cadaveric femurs with normal-to-osteoporotic bone mineral density to investigate its relationship to femur cross-sectional properties, bone material strength, and torsional strength reduction. METHODS: An eccentric circular cross-sectional model was developed. Twenty matched cadaveric femurs (8-normal, 6-osteopenic, and 6-osteoporotic) were tested. Left femur was reamed 1.5 mm larger than isthmic endosteal diameter measured from radiographs. Right (control) and left (reamed) femurs were torsionally loaded to failure. Periosteal-endosteal circles were fit tangent to the thinnest wall on computer tomography cross-sectional image at level of spiral fracture to determine periosteal-endosteal circle diameters (dp, de) and their eccentricity (e), and to calculate cross section's size-eccentricity factor. These and torque failure were substituted into the model to calculate bone material's effective tensile strength. RESULTS: Osteoporotic compared with normal femurs had higher de/dp ratio (0.71 vs. 0.47), lower cross-sectional size-eccentricity factor (-41%), bone material strength (-57%), and torsional strength (-73%). Predicted % reduction in torsional strength by either concentric over reaming or canal eccentricity exponentially increases with increase in de/dp (notably beyond 0.47 of normal bone mineral density). CONCLUSIONS: Manufacturer's recommended 1.5 mm oversize RIA is conservative (<10% reduction) if concentric in femurs with isthmus de/dp < 0.60 mm and dp > 18.3 mm. An eccentric canal can significantly compromise a long bone's torsional strength, more than if reamed concentric to larger diameter having same minimum wall thickness. Other "safe/unsafe" oversize-eccentricity conditions are in quick clinical reference tables.

Injury to neurovascular structures with insertion of traction pins around the knee.

OBJECTIVE: Identify risk to neurovascular structures around the knee with placement of skeletal traction pins. METHODS: Kirchner wires were inserted into cadaveric limbs followed by layer dissecting of each leg. Correlations between weight, height, BMI, and distance were determined after calculating the average distance with deviation between each anatomic structure and the Kirschner wire. CONCLUSION: Insertion of traction pins around the knee did not result in injury to neurovascular structures. Both weight and BMI positively correlated with distance between implants and neurovascular structure. Data collected suggests similar trends for all other anatomic structures.