Prospective derivation and validation of a NECROtizing Soft tissue InfectionS (NECROSIS) score: An EAST multicenter trial.

BACKGROUND: Although several risk indices have been developed to aid in the diagnosis of NSTIs, these instruments suffer from varying levels of reproducibility and failure to incorporate key clinical variables in model development. The objective of this study was to derive and validate a clinical risk index score - NECROSIS - for identifying NSTIs in emergency general surgery (EGS) patients being evaluated for severe skin and soft tissue infections. METHODS: We performed a prospective study across 16 sites in the US of adult EGS patients with suspected NSTIs over a 30-month period. Variables analyzed included demographics, admission vitals and labs, physical exam, radiographic, and operative findings. The main outcome measure was the presence of NSTI diagnosed clinically at the time of surgery. Multivariate analysis was performed to identify independent predictors for the presence of NSTI using the Hosmer-Lemeshow test and the Akaike information criteria. RESULTS: Of 362 patients, 297 (82%) were diagnosed with a NSTI. Overall mortality was 12.3%. Multivariate analysis identified 3 independent predictors for NSTI: systolic blood pressure ≤ 120 mmHg, violaceous skin, and WBC ≥15 (x103/uL). Multivariate modelling demonstrated Hosmer-Lemeshow goodness of fit (p = 0.9) with a c-statistic for the prediction curve of 0.75. Test characteristics of the NECROSIS score were similar between the derivation and validation cohorts. CONCLUSION: NECROSIS is a simple and potentially useful clinical index score for identifying at-risk EGS patients with NSTIs. Future validation studies are warranted. LEVEL OF EVIDENCE: Diagnostic Tests or Criteria, Level III.

A novel preoperative score to predict severe acute cholecystitis.

BACKGROUND: In a large multicenter trial, The Parkland Grading Scale (PGS) for acute cholecystitis outperformed other grading scales and has a positive correlation with complications but is limited in its inability to preoperatively predict high-grade cholecystitis. We sought to identify preoperative variables predictive of high-grade cholecystitis (PGS 4 or 5). METHODS: In a six-month period, patients undergoing cholecystectomy at a single institution with prospectively graded PGS were analyzed. Stepwise logistic regression models were constructed to predict high-grade cholecystitis. The relative weight of the variables was used to derive a novel score, the Severe Acute Cholecystitis Score (SACS). This score was compared with the Emergency Surgery Acuity Score(ESS), American Association for the Surgery of Trauma (AAST) preoperative score and Tokyo Guidelines (TG) for their ability to predict high-grade cholecystitis. Severe Acute Cholecystitis Score was then validated using the database from the AAST multicenter validation of the grading scale for acute cholecystitis. RESULTS: Of the 575 patients that underwent cholecystectomy, 172 (29.9%) were classified as high-grade. The stepwise logistic regression modeling identified seven independent predictors of high-grade cholecystitis. From these variables, the SACS was derived. Scores ranged from 0 to 9 points with a C statistic of 0.76, outperforming the ESS ( C statistic of 0.60), AAST (0.53), and TG (0.70) ( p < 0.001). Using a cutoff of 4 or more on the SACS correctly identifies 76.2% of cases with a specificity of 91.3% and a sensitivity of 40.7%. In the multicenter database, there were 464 patients with a prospectively collected PGS. The C statistic for SACS was 0.74. Using the same cutoff of 4, SACS correctly identifies 71.6% of cases with a specificity of 83.8% and a sensitivity of 52.2%. CONCLUSION: The Severe Acute Cholecystitis Score can preoperatively predict high-grade cholecystitis and may be useful for counseling patients and assisting in surgical decision making. LEVEL OF EVIDENCE: Diagnostic Test/Criteria; Level III.

Burn and Trauma Burden and Screening for Interpersonal Violence During the COVID-19 Pandemic.

INTRODUCTION: Nationwide shelter-in-place (SIP) orders during the pandemic have had long-lasting effects, including increased rates of domestic violence and interpersonal violence. Screening for violence varies by institution, which tool is used, and when. Given increases in burn and trauma admissions over the course of the pandemic, we sought to examine trends at our institution during this time period to better guide care and anticipate system-level effects. METHODS: We performed a retrospective cohort study of pediatric burn and adult burn and trauma patients at our level 1 trauma/burn center between March-May 2019 and March-May 2020. Home safety screening was performed by nursing staff using a 1-part screening questionnaire. Patients presenting before March 15, 2020, were defined as "pre-SIP; " between March 16-May 19, 2020, were "during SIP; " and those after May 19, 2020, were designated as "post-SIP." Descriptive and chi-square statistics were used. Demographic, injury patterns, and screening information were collected. RESULTS: Blunt trauma comprised 60% of injuries, followed by burns (30%) then penetrating injury (7%). Over the entire time period analyzed, 1822 patients had documented home safety screening; ∼2% of patients screened reported a safety concern pre-SIP, compared to 3% of patients during SIP. There were higher rates of burns and penetrating injury during SIP compared to other periods (P ≤ 0.0001). Home safety screening rates were 94%-95% pre- and during SIP, but dropped to 85% post-SIP (P < 0.0001). Home safety concerns were reported almost 2% of the time pre-SIP and 3% during SIP (P = 0.016). CONCLUSIONS: We noted an increase in trauma and burns during and after SIP orders, consistent with the experiences of other institutions. Implementation of a nurse-driven screening process demonstrated high compliance with appropriate referrals. The burden of burn and traumatic injury remains significant, highlighting a need for continued psychosocial screening and the provision of psychosocial support resources in the acute trauma setting.

Under the Lens: Team Perception of Trauma Video Review.

BACKGROUND: Video-based assessment and review are becoming increasingly common, and trauma video review (TVR) has been shown to be an effective educational, quality improvement, and research tool. Yet, trauma team perception of TVR remains incompletely understood. OBJECTIVE: We evaluated positive and negative perceptions of TVR across multiple team member groups. We hypothesized that members of the trauma team would find TVR educational and that anxiety would be low across all groups. METHODS: An anonymous electronic survey was provided to nurses, trainees, and faculty during weekly multidisciplinary trauma performance improvement conference following each TVR activity. Surveys assessed perception of performance improvement and anxiety or apprehension (Likert scale: 1 "strongly disagree" to 5 "strongly agree"). We report individual and normalized cumulative scores (average of responses for each positive [n = 6] and negative [n = 4] question stem). RESULTS: We analyzed 146 surveys over 8 months, with 100% completion rate. Respondents were trainees (58%), faculty (29%), and nurses (13%). Of the trainees, 73% were postgraduate year (PGY) 1-3 and 27% were PGY 4-9. Of all respondents, 84% had participated previously in a TVR conference. Respondents reported an improved perception of resuscitation education quality and personal leadership skills development. Participants found TVR to be more educational than punitive overall. Analysis of team member types showed lower scores for faculty for all positive stemmed questions. Trainees were more likely to agree with negative stemmed questions if they were a lower PGY, and nurses were least likely to agree with negative stemmed questions. CONCLUSIONS: TVR improves trauma resuscitation education in a conference setting, with trainees and nurses reporting the greatest benefit. Nurses were noted to be the least apprehensive about TVR.

Provider Perception of Time During Trauma Resuscitation: A Prospective Quantitative Trauma Video Review Analysis.

INTRODUCTION: Delays in transition to the next phase of care result in increased mortality. Prehospital literature suggests emergency medical service technicians underestimate transport times by as much as 20%. What remains unknown is clinician perception of time during the trauma resuscitation. We sought to determine if clinicians have an altered perception of time. We hypothesized that clinicians underestimate time, resulting in delay of care. METHODS: Clinicians at a large level 1 trauma center completed a post-trauma activation survey on the perceived elapsed time to complete three specific resuscitation endpoints. The primary study endpoint was the time to the next phase of care, defined as leaving the trauma bay to go to the operating room, interventional radiology, computerized tomography or time of death. The data from the surveys were linked and compared with recorded videos of the resuscitations. The difference in perceived versus actual time, along with confounding variables, was used to assess the impact of perception of time on the time to the next phase of care using a stepwise multivariate linear model. RESULTS: There were 284 complete surveys and videos, culminating in 543 time points. The median perceived versus actual time (minutes [interquartile range]) to the next phase of care was 20 [10-25] versus 26 [19-40] (P < 0.001). Overall, clinicians underestimated time by 28%, such that if the resuscitation lasted 20 min, the clinician's perception was that 14.4 min elapsed. Differences in the perceived versus actual time in the procedure group impacted time to the next phase of care (P = 0.01). CONCLUSIONS: Clinicians have significant gaps in the perception of time during trauma resuscitations. This misperception occurs during procedures and correlates with an increase in the length of time to the next phase of care.

Resuscitative endovascular balloon occlusion of the aorta: simulation improves performance but may require interval training to prevent skill degradation.

PURPOSE: Surgical trainees are exposed to less procedures with increasing need for simulation. Resuscitative endovascular balloon occlusion of the aorta (REBOA) has become increasingly implemented for hemorrhage control, yet most courses are catered to faculty level with little data on trainees. We propose that routine training in this critical procedure will improve trainee performance over time. METHODS: This is a prospective, observational study at a level I trauma center involving a monthly trauma procedural program. Early in the month, trainees received hands-on REBOA training; at the end, trainees underwent standardized, class-based evaluation on a perfused trainer. Score percentages were recorded (0-100%). Endpoints included early, mid and late performance (2-12 months). Paired T-test and Pearson's coefficient were used to evaluate differences and strength of association between time between training and performance. RESULTS: 25 trainees participated with 5 and 11 repeat learners in the PGY-2 and PGY-3 classes, respectively. Median early performance score was 62.5% (IQR 56-81) for PGY-2s and 91.6% (IQR 75-100) in PGY-3s. Pearson's coefficient between time between and training and score demonstrated a weak correlation in the PGY-2s (r2 = - 0.13), but was more pronounced in the PGY-3s (r2 = - 0.44) with an inflection point at 5 months. CONCLUSIONS: Routine REBOA training in trainees is associated with improvement in performance within a short period of time. Skill degradation was most pronounced in trainees who did not receive training for more than 5 months. Trainees can be successfully trained in REBOA; however, this should be done at shorter intervals to prevent skill degradation.

Revision of the AAST grading scale for acute cholecystitis with comparison to physiologic measures of severity.

BACKGROUND: Grading systems for acute cholecystitis are essential to compare outcomes, improve quality, and advance research. The American Association for the Surgery of Trauma (AAST) grading system for acute cholecystitis was only moderately discriminant when predicting multiple outcomes and underperformed the Tokyo guidelines and Parkland grade. We hypothesized that through additional expert consensus, the predictive capacity of the AAST anatomic grading system could be improved. METHODS: A modified Delphi approach was used to revise the AAST grading system. Changes were made to improve distribution of patients across grades, and additional key clinical variables were introduced. The revised version was assessed using prospectively collected data from an AAST multicenter study. Patient distribution across grades was assessed, and the revised grading system was evaluated based on predictive capacity using area under receiver operating characteristic curves for conversion from laparoscopic to an open procedure, use of a surgical "bail-out" procedure, bile leak, major complications, and discharge home. A preoperative AAST grade was defined based on preoperative, clinical, and radiologic data, and the Parkland grade was also substituted for the operative component of the AAST grade. RESULTS: Using prospectively collected data on 861 patients with acute cholecystitis the revised version of the AAST grade has an improved distribution across all grades, both the overall grade and across each subscale. A higher AAST grade predicted each of the outcomes assessed (all p ≤ 0.01). The revised AAST grade outperformed the original AAST grade for predicting operative outcomes and discharge disposition. Despite this improvement, the AAST grade did not outperform the Parkland grade or the Emergency Surgery Score. CONCLUSION: The revised AAST grade and the preoperative AAST grade demonstrated improved discrimination; however, a purely anatomic grade based on chart review is unlikely to predict outcomes without addition of physiologic variables. Follow-up validation will be necessary. LEVEL OF EVIDENCE: Diagnostic Test or Criteria, Level IV.

Adoption of rescue colloid during burn resuscitation decreases fluid administered and restores end-organ perfusion.

INTRODUCTION: Traditionally, lactated Ringer's solution (LR) has been utilized for the resuscitation of thermally injured patients via the Parkland or Brooke formulas. Both of these formulas include colloid supplementation after 24 h of resuscitation. Recently, the addition of albumin within the initial resuscitation has been reported to decrease fluid creep and hourly fluids given. Our institution has previously advocated for a crystalloid-driven resuscitation. Given reports of improved outcomes with albumin, we pragmatically adjusted these practices and present our findings for doing so. METHODS: Our burn registry, consisting of prospectively collected patient data, was queried for those at least 18 years of age who, between July 2017 and December 2018, sustained a thermal injury and completed a formal resuscitation (24 h). At the attending physician's discretion, rescue colloid was administered using 25% albumin for those failing to respond to traditional resuscitation (patients with sustained urine output of <0.5 mL/kg over 2-3 h, or unstable vital signs and ongoing fluid administration). We compared the total volume of the crystalloid-only and rescue colloid resuscitation fluids given to patients. We also examined the in/out fluid balances during resuscitation. Statistical analysis was performed using Stata software. RESULTS: A total of 91 patients with thermal injuries were included: the median age was 40 (IQR 31-57), 73% were male, and 30 patients received rescue albumin. The percentage of total body surface area burned (%TBSA) was greater in those who received rescue albumin (40.3% vs. 34%; p = 0.047). Despite a higher %TBSA in the albumin group, the total LR given during resuscitation was not significantly different between groups (15,914.43 mL vs. 11,828.71 mL; p = 0.129) even when normalized for TBSA and weight (ml LR/kg/%TBSA: 4.31 vs. 3.66; p = 0.129. The average in/out fluid ratio for the rescue group was higher than for the crystalloid group (0.83 ± 0.05 vs. 0.59 ± 0.11; p = 0.06) and returned to normal after colloid administration. CONCLUSION: Rescue albumin administration decreases the amount of fluid administered per %TBSA during resuscitation, and also increases end organ function as evidenced by increased urinary output. These effects occurred in patients who sustained larger burns and failed to respond to traditional crystalloid resuscitation. Our findings led us to modify our current protocol and a related prospective study of clinical outcomes.

Using telemedicine on an acute care surgery service: improving clinic efficiency and access to care.

BACKGROUND: Telemedicine has been shown to improve patient access to medical care while potentially improving overall healthcare efficiency. It has not been consistently explored on an acute care surgery service as a method of increasing clinic availability and efficiency within a safety-net hospital system. Socioeconomic hardships associated with an in-person clinic visit can deter patients with limited resources. A virtual clinic for post-operative laparoscopic cholecystectomy patients was developed. We hypothesized that a virtual follow-up increases clinic efficiency and availability for new patients without compromising patient safety. METHODS: A retrospective review of patient and clinic outcomes before and after implementing virtual post-op visits for uncomplicated laparoscopic cholecystectomy patients on an acute care surgery service was performed. Providers called post-operative patients using a standardized questionnaire. Data included outpatient clinic composition (new vs. post-operative patients), elective operations scheduled, emergency department visits, and loss to follow-up rates. RESULTS: February to March 2017 was the baseline pre-intervention period, while February to March 2019 was post-intervention. Pre-intervention clinics consisted of 17% new and 50% post-op visits, in comparison to 31% new and 27% post-op visits in the post-intervention group (p < 0.01). Elective operations scheduled increased slightly from 8.4 to 11.5 per 100 patient visits, but was not statistically significant (p = 0.09). There was no change in the number of post-operative patients returning to the emergency department (p = 0.91) or loss to follow-up (p = 0.30) rates. CONCLUSIONS: Through the implementation of virtual post-operative visits for laparoscopic cholecystectomy patients, clinic efficiency improved by increasing new patient encounters, decreasing post-operative volume, and trending towards increased operations scheduled. This change did not compromise patient safety. Further implementation of telemedicine on an acute care surgery service is a promising method to expand services offered to an at-risk population and increase efficiency in a resource-limited environment.

Multicenter validation of the American Association for the Surgery of Trauma grading scale for acute cholecystitis.

BACKGROUND: The American Association for the Surgery of Trauma (AAST) patient assessment committee has created grading systems for emergency general surgery diseases to assist with clinical decision making and risk adjustment during research. Single-institution studies have validated the cholecystitis grading system as associated with patient outcomes. Our aim was to validate the grading system in a multi-institutional fashion and compare it with the Parkland grade and Tokyo Guidelines for acute cholecystitis. METHODS: Patients presenting with acute cholecystitis to 1 of 8 institutions were enrolled. Discrete data to assign the AAST grade were collected. The Parkland grade was collected prospectively from the operative surgeon from four institutions. Parkland grade, Tokyo Guidelines, AAST grade, and the AAST preoperative grade (clinical and imaging subscales) were compared using linear and logistic regression to the need for surgical "bailout" (subtotal or fenestrated cholecystectomy, or cholecystostomy), conversion to open, surgical complications (bile leak, surgical site infection, bile duct injury), all complications, and operative time. RESULTS: Of 861 patients, 781 underwent cholecystectomy. Mean (SD) age was 51.1 (18.6), and 62.7% were female. There were six deaths. Median AAST grade was 2 (interquartile range [IQR], 1-2), and median Parkland grade was 3 (interquartile range [IQR], 2-4). Median AAST clinical and imaging grades were 2 (IQR, 2-2) and 1 (IQR, 0-1), respectively. Higher grades were associated with longer operative times, and worse outcomes although few were significant. The Parkland grade outperformed the AAST grade based on area under the receiver operating characteristic curve. CONCLUSION: The AAST cholecystitis grading schema has modest discriminatory power similar to the Tokyo Guidelines, but generally lower than the Parkland grade, and should be modified before widespread use. LEVEL OF EVIDENCE: Diagnostic study, level IV.

Fast track pathway provides safe, value based care on busy acute care surgery service.

BACKGROUND: Fast track (FT) pathways have been adopted across a multitude of elective surgeries but have been slow to be adopted into the acute care surgery realm. We hypothesized that an FT pathway for acute cholecystitis patients would decrease patient length of stay and resource utilization. METHODS: All patients at two hospitals, one with an FT pathway and one with a traditional pathway, who underwent an urgent laparoscopic cholecystectomy for acute cholecystitis between May 1, 2019, and October 31, 2019, were queried using CPT codes. Exclusion criteria were conversion to open or partial cholecystectomy. Retrospective chart review was used to gather demographics, operative, hospital course, and outcomes. Time to operating room, hospital length of stay, and resource utilization were the primary outcomes. RESULTS: There was a total of 479 urgent laparoscopic cholecystectomies performed, 430 (89.8%) were performed under the FT pathway. The median (interquartile range [IQR]) time to the operating room was not different: 14.1 hours (IQR, 8.3-29.0 hours) for FT and 18.5 hours (IQR, 11.9-25.9 hours) for traditional (p = 0.316). However, the median length of stay was shorter by 15.9 hours in the FT cohort (22.6 hours; IQR, 14.2-40.4 hours vs. 38.5 hours; IQR, 28.3-56.3 hours; p < 0.001). Under the FT pathway, 33.0% of patients were admitted to the hospital and 75.6% were discharged from the postanesthesia care unit, compared with 91.8% and 12.2% on the traditional pathway (both p < 0.001). There were 59.6% of the FT patients that received a phone call follow up, as opposed to 100% of the traditional patients having clinic follow up (p < 0.001). The emergency department bounce back rate, readmission rates, and complication rates were similar (p > 0.2 for all). On multivariate analysis, having a FT pathway was an independent predictor of discharge within 24 hours of surgical consultation (odds ratio, 7.65; 95% confidence interval< 2.90-20.15; p < 0.001). CONCLUSION: Use of a FT program for patients with acute cholecystitis has a significant positive impact on resource utilization without compromise of clinical outcomes. LEVEL OF EVIDENCE: Therapeutic/care management, level IV.

Association of the Risk of a Venous Thromboembolic Event in Emergency vs Elective General Surgery.

Importance: Trauma patients have an increased risk of venous thromboembolism (VTE), partly because of greater inflammation. However, it is unknown if this association is present in patients who undergo emergency general surgery (EGS). Objectives: To investigate whether emergency case status is independently associated with VTE compared with elective case status and to test the hypothesis that emergency cases would have a higher risk of VTE. Design, Setting, and Participants: This retrospective cohort study used the American College of Surgeons National Surgical Quality Improvement Program database from January 1, 2005, to December 31, 2016, for all cholecystectomies, ventral hernia repairs (VHRs), and partial colectomies (PCs) to obtain a sample of commonly encountered emergency procedures that have elective counterparts. Emergency surgeries were then compared with elective surgeries. The dates of analysis were January 1 to 31, 2019. Main Outcomes and Measures: The primary outcome was VTE at 30 days. A multivariable analysis controlling for age, sex, body mass index, bleeding disorder, disseminated cancer, laparoscopy approach, and surgery type was performed. Results: There were 604 537 adults undergoing surgical procedures over 12 years (mean [SD] age, 55.3 [16.6] years; 61.4% women), including 285 847 cholecystectomies, 158 500 VHRs, and 160 190 PCs. The rate of VTE within 30 days was 1.9% for EGS and 0.8% for elective surgery, a statistically significant difference. Overall, 4607 patients (0.8%) had deep vein thrombosis, and 2648 patients (0.4%) had pulmonary embolism. A total of 6624 VTEs (1.1%) occurred in the cohort. As expected, when VTE risk was examined by surgery type, the risk increased with invasiveness (0.5% for cholecystectomy, 0.8% for VHR, and 2.4% for PC; P < .001). On multivariable analysis, EGS was independently associated with VTE (odds ratio [OR], 1.70; 95% CI, 1.61-1.79). Also associated with VTE were open surgery (OR, 3.38; 95% CI, 3.15-3.63) and PC (OR, 1.86; 95% CI, 1.73-1.99). Conclusions and Relevance: In this cohort study, emergency surgery and increased invasiveness appeared to be independently associated with VTE compared with elective surgery. Further study on methods to improve VTE chemoprophylaxis is highly recommended for emergency and more extensive operations to reduce the risk of potentially lethal VTE.

Control of Bone Anabolism in Response to Mechanical Loading and PTH by Distinct Mechanisms Downstream of the PTH Receptor.

Osteocytes integrate the responses of bone to mechanical and hormonal stimuli by poorly understood mechanisms. We report here that mice with conditional deletion of the parathyroid hormone (PTH) receptor 1 (Pth1r) in dentin matrix protein 1 (DMP1)-8kb-expressing cells (cKO) exhibit a modest decrease in bone resorption leading to a mild increase in cancellous bone without changes in cortical bone. However, bone resorption in response to endogenous chronic elevation of PTH in growing or adult cKO mice induced by a low calcium diet remained intact, because the increased bone remodeling and bone loss was indistinguishable from that exhibited by control littermates. In contrast, the bone gain and increased bone formation in cancellous and cortical bone induced by daily injections of PTH and the periosteal bone apposition induced by axial ulna loading were markedly reduced in cKO mice compared to controls. Remarkably, however, wild-type (WT) control littermates and transgenic mice overexpressing SOST injected daily with PTH exhibit similar activation of Wnt/ß-catenin signaling, increased bone formation, and cancellous and cortical bone gain. Taken together, these findings demonstrate that Pth1r in DMP1-8kb-expressing cells is required to maintain basal levels of bone resorption but is dispensable for the catabolic action of chronic PTH elevation; and it is essential for the anabolic actions of daily PTH injections and mechanical loading. However, downregulation of Sost/sclerostin, previously shown to be required for bone anabolism induced by mechanical loading, is not required for PTH-induced bone gain, showing that other mechanisms downstream of the Pth1r in DMP1-8kb-expressing cells are responsible for the hormonal effect. © 2016 American Society for Bone and Mineral Research.

Parathyroid hormone receptor signaling induces bone resorption in the adult skeleton by directly regulating the RANKL gene in osteocytes.

PTH upregulates the expression of the receptor activator of nuclear factor κB ligand (Rankl) in cells of the osteoblastic lineage, but the precise differentiation stage of the PTH target cell responsible for RANKL-mediated stimulation of bone resorption remains undefined. We report that constitutive activation of PTH receptor signaling only in osteocytes in transgenic mice (DMP1-caPTHR1) was sufficient to increase Rankl expression and bone resorption. Resorption in DMP1-caPTHR1 mice crossed with mice lacking the distal control region regulated by PTH in the Rankl gene (DCR(-/-)) was similar to DMP1-caPTHR1 mice at 1 month of age, but progressively declined to reach values undistinguishable from wild-type (WT) mice at 5 months of age. Moreover, DMP1-caPTHR1 mice exhibited low tissue material density and increased serum alkaline phosphatase activity at 5 month of age, and these indices of high remodeling were partially and totally corrected in compound DMP1-caPTHR1;DCR(-/-) male mice, and less affected in female mice. Rankl expression in bones from DMP1-caPTHR1 mice was elevated at both 1 and 5 months of age, whereas it was high, similar to DMP1-caPTHR1 mice at 1 month, but low, similar to WT levels at 5 months in compound mice. Moreover, PTH increased Rankl and decreased Sost and Opg expression in ex vivo bone organ cultures established from WT mice, but only regulated Sost and Opg expression in cultures from DCR(-/-) mice. PTH also increased RANKL expression in osteocyte-containing primary cultures of calvarial cells, in isolated murine osteocytes, and in WT but not in DCR(-/-) osteocyte-enriched bones. Thus, PTH upregulates Rankl expression in osteocytes in vitro, ex vivo and in vivo, and resorption induced by PTH receptor signaling in the adult skeleton requires direct regulation of the Rankl gene in osteocytes.