Reza Firoozabadi

Evidence that exposure of the telomere 3′ overhang sequence induces senescence

Normal human cells cease proliferation after a finite number of population doublings, a phenomenon termed replicative senescence. This process, first convincingly described by Hayflick and Moorhead [Hayflick, L. & Moorhead, P. S. (1961) Exp. Cell Res. 25, 595–621] for cultured human fibroblasts 40 years ago, is suggested to be a fundamental defense against cancer. Several events have been demonstrated to induce the senescent phenotype including telomere shortening, DNA damage, oxidative stress, and oncogenic stimulation. The molecular mechanisms underlying senescence are poorly understood. Here we report that a 1-week exposure to oligonucleotide homologous to the telomere 3′-overhang sequence TTAGGG (T-oligo) similarly specifically induces a senescent phenotype in cultured human fibroblasts, mimicking serial passage or ectopic expression of a dominant negative form of the telomeric repeat binding factor, TRF2DN. We propose that exposure of the 3′ overhang due to telomere loop disruption may occur with critical telomere shortening or extensive acute DNA damage and that the exposed TTAGGG tandem repeat sequence then triggers DNA-damage responses. We further demonstrate that these responses can be induced by treatment with oligonucleotides homologous to the overhang in the absence of telomere disruption, a phenomenon of potential therapeutic importance.

Induction of a p95/Nbs1-mediated S phase checkpoint by telomere 3′ overhang specific DNA

Telomere shortening induces a nonproliferative senescent phenotype, believed to reduce cancer risk, and telomeres are involved in a poorly understood manner in responses to DNA damage. Although telomere disruption induces p53 and triggers apoptosis or cell cycle arrest, the features of the disrupted telomere that trigger this response and the precise mechanism involved are poorly understood. Using human cells, we show that DNA oligonucleotides homologous to the telomere 3′ overhang sequence specifically induce and activate p53 and activate an S phase checkpoint by modifying the Nijmegen breakage syndrome protein, known to mediate the S phase checkpoint after DNA damage. These responses are mediated, at least in part, by the ATM kinase and are not attributable to disruption of cellular telomeres. Based on these and earlier data, we propose that these oligonucleotides mimic a physiological signal, exposure of the telomere 3′ overhang due to opening of the normal telomere loop structure, and hence evoke these protective anti‐proliferative responses in the absence of DNA damage or telomere disruption. Eller, M. S., Li, G.‐Z., Firoozabadi, R., Puri, N., Gilchrest, B. A. Induction of a P95/NBS1‐mediated S phase checkpoint by telomere 3′ overhang specific DNA. FASEB J. 17, 152–162 (2003)

Diastolic Blood Pressure in Patients With Tibia Fractures Under Anaesthesia : Implications for the Diagnosis of Compartment Syndrome

Objective: In the treatment of tibia fractures, is the intraoperative diastolic blood pressure (DBP) less than pre- and postoperative DBP, and how does this relate to the diagnosis of compartment syndrome using ΔP (diastolic blood pressure [DBP] - intracompartmental pressure)? Design, Setting, and Patients: This was a prospective cohort study in a level 1 trauma center, with a consecutive series of 242 patients with a tibia fracture. Intervention: Intramedullary nail fixation of tibia fractures under general anesthesia. Main Outcome Measures: Patient demographics, type and location of fracture, injury severity score, and blood pressures preoperatively, intraoperatively, and postoperatively. Results: There were 187 male and 55 female patients, whose ages ranged from 16 to 87 years (average, 39 years). There were 123 open and 119 closed tibia fractures. The average injury severity score was 14.7 (range: 9-41). Anesthetized patients had a significant decrease in their DBP and systolic blood pressure (SBP) compared with their preoperative, postanesthesia care unit and postoperative floor measurements. The mean DBP in the operating room was 18 ± 13 mm Hg lower than the preoperative measurement (P < 0.05), whereas the difference in the preoperative and postoperative mean DBP was only 2 ± 13 mm Hg. Conclusions: There is a predictable response of DBP in patients with tibia fractures treated with intramedullary (IM) nailing under general anesthesia. The preoperative DBP is a good indicator of the postoperative DBP, and the intraoperative DBP is significantly lower (average 18 mm Hg; P < 0.05). The surgeon should recognize that intraoperative ΔP may be lower than ΔP once the patient is awakened in deciding whether to perform a fasciotomy or awaken the patient and perform serial examinations and or compartment pressure measurements. Intraoperative ΔP may be spuriously low compared with that after the patient is awakened.

Qualitative and quantitative assessment of bone fragility and fracture healing using conventional radiography and advanced imaging technologies--focus on wrist fracture.

Fractures of the distal radius are one of the most common injuries presented to orthopaedic surgeons. A variety of treatment options are available for the vast array of fracture patterns. Research that explores bone fragility and fracture healing has led to new treatment modalities. As new products and methods are derived to aid in fracture healing it is essential to develop noninvasive and/or nondestructive techniques to assess structural information about bone. Quantitative assessment of macro-structural characteristics such as geometry, and microstructural features such as relative trabecular volume, trabecular spacing, and connectivity may improve our ability to estimate bone strength. Methods for quantitatively assessing macrostructure include (besides conventional radiographs) dual x-ray absorptiometry (DXA) and computed tomography (CT), particularly volumetric quantitative computed tomography (vQCT). Methods for assessing microstructure of trabecular bone include high resolution computed tomography (hrCT), micro computed tomography (μCT), high resolution magnetic resonance (hrMR), and micro magnetic resonance μMR. Volumetric QCT, hrCT and hrMR are generally applicable in vivo; μCT and μMR are principally applicable in vitro. Clinically, the challenges for bone imaging include balancing the advantages of simple bone densitometry versus the more complex architectural features of bone, or the deeper research requirements versus the broader clinical needs.

Risk Factors for the Development of Heterotopic Ossification After Acetabular Fracture Fixation

BackgroundHeterotopic ossification (HO) is a common complication of the operative treatment of acetabular fractures. Although the surgical approach has been shown to correlate with the development of ectopic bone, specific risk factors have not been elucidated.Questions/purposesThe purposes of this study were to determine specific risk factors associated with the development of severe HO and the frequency with which patients develop severe HO after acetabular fracture fixation through an isolated Kocher-Langenbeck approach.MethodsUsing an institutional orthopaedic trauma database at a regional Level I trauma center, patients undergoing open treatment of acetabular fractures during the study period (January 2000 to January 2010) were identified. A review of medical records and imaging studies was performed on 508 patients who were treated by the senior author (MR) through an isolated Kocher-Langenbeck approach. During the study period, the senior author used indomethacin for HO prophylaxis in patients who had ipsilateral femur fracture treated with antegrade reamed medullary nailing or severe local soft tissue injury; 49 (10%) of the patients he treated with the Kocher-Langenbeck approach received prophylaxis, and they were excluded from this study, leaving a total of 459 patients who met inclusion criteria. Of those, 147 (29%) were lost to followup or did not have radiographs both before and at a minimum of 6 weeks (median, 1 week; range, 0–3 weeks), leaving 312 (61% of the patients treated with the Kocher-Langenbeck approach during this time) available for this analysis. Demographic data as well as information related to cause of injury, associated periacetabular findings, other system injuries, and treatment were gathered. Final followup radiographs were assessed for the presence of ectopic bone by two of the authors (TJO, AS) using the modified Brooker classification. Logistic regression was performed to identify possible predictors of development of severe ectopic bone.ResultsThe only predictor we identified for the development of severe HO was the need for prolonged mechanical ventilation (odds ratio, 7.1; 95% confidence interval, 2.9–17.3; p = 0.001). Injury Severity Score, sex, presence of comminution, femoral head impaction, dislocation, degloving injury, debris in the joint, number of other fractures, and head and chest Abbreviated Injury Score > 2 did not correlate with severe HO. Severe HO (Brooker Class III or IV) developed in 38 of 312 patients (12%).ConclusionsPatients with prolonged mechanical ventilation might benefit from HO prophylaxis given the increased risk of developing severe HO in this patient population. However, future prospective studies need to be performed to verify this finding given the fact that a considerable number of patients were prophylactically treated in this study.Level of EvidenceLevel IV, prognosticstudy. See Guidelines for Authors for a complete description of levels of evidence.

Building a clinical research network in trauma orthopaedics: The major extremity trauma research consortium (METRC)

Objectives: Lessons learned from battle have been fundamental to advancing the care of injuries that occur in civilian life. Equally important is the need to further refine these advances in civilian practice, so they are available during future conflicts. The Major Extremity Trauma Research Consortium (METRC) was established to address these needs. Methods: METRC is a network of 22 core level I civilian trauma centers and 4 core military treatment centers—with the ability to expand patient recruitment to more than 30 additional satellite trauma centers for the purpose of conducting multicenter research studies relevant to the treatment and outcomes of orthopaedic trauma sustained in the military. Early measures of success of the Consortium pertain to building of an infrastructure to support the network, managing the regulatory process, and enrolling and following patients in multiple studies. Results: METRC has been successful in maintaining the engagement of several leading, high volume, level I trauma centers that form the core of METRC; together they operatively manage 15,432 major fractures annually. METRC is currently funded to conduct 18 prospective studies that address 6 priority areas. The design and implementation of these studies are managed through a single coordinating center. As of December 1, 2015, a total of 4560 participants have been enrolled. Conclusions: Success of METRC to date confirms the potential for civilian and military trauma centers to collaborate on critical research issues and leverage the strength that comes from engaging patients and providers from across multiple centers.

Dynamizations and Exchanges: Success Rates and Indications.

Objective: To characterize the timing, indications, and “success rates of secondary interventions, dynamization and exchange nailing, in a large series of tibial nonunions” (dynamization and exchange nailing are types of secondary interventions). Setting: Retrospective multicenter analysis from level 1 trauma hospitals. Patients: A total of 194 tibia fractures that underwent dynamization or exchange nailing for delayed/nonunion. Intervention: Records and radiographs to characterize demographic data, fracture type, and cortical contact after tibial nailing were gathered. The radiographic union score for tibias (RUST) and the timing of intervention and time to union were calculated. Main Outcome Measures: The primary outcome was success of either intervention, defined as achieving union, with the need for further intervention defining failure. Other outcomes included RUST scores at intervention and union, and timing to intervention and union for both techniques. Two-tailed t tests and Fisher exact with P set at <0.05 for significance were used as indicated. Results: A total of 194 tibia fractures underwent dynamization (97) or exchange nailing (97). No statistical differences were found between groups with demographic characteristics. The presence of a fracture gap (P = 0.01) and comminuted fractures (P = 0.002) was more common in the exchange group. The success rates of the interventions and RUST scores were not different when performed before versus after 6 months; therefore, data were pooled. The RUST scores at the time of intervention were not different for successful or failed dynamizations (7.13 vs. 7.07, P = 0.83) or exchanges (6.8 vs. 7.3, P = 0.37). Likewise, the time to successful versus failed dynamization (165 vs. 158 days, P = 0.91) or exchange nailing (224 vs. 201 days, P = 0.48) was not different. No cortical contact or a gap was a statistically negative factor for both exchange nails (P = 0.09) and dynamizations (P = 0.06). When combined, the success in the face of a gap was 78% versus 92% when no gap was present (P = 0.02). Conclusions: Previous literature has few reports of the success rates of secondary interventions for tibial nonunions. The indications for dynamization and exchange were similar. Comminuted fractures, and fractures with no cortical contact or “gap” present after intramedullary nailing, favored having an exchange nail performed over dynamization. Fracture gap was also found to be a negative prognostic factor for both procedures. Overall, this study demonstrates high rates of union for both interventions, making them both viable options. Level of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Cell Saver Use in Acetabular Surgery: Does Approach Matter?

Objective: To determine if intraoperative autologous transfusion using a Cell Saver (CS) was routinely indicated for open reduction internal fixation (ORIF) of acetabular fractures, and if so, was there a difference between differing surgical approaches. Design: Retrospective single-center cohort study. Setting: University Level 1 trauma center. Patients/Participants: One hundred forty-five consecutive acetabular fractures using intraoperative autologous transfusion, either treated with an anterior ilioinguinal or a posterior-based Kocher–Langenbeck approach, were compared. Intervention: Use of CS in ORIF acetabular cases. Main Outcome Measurements: CS utilization and CS blood return for acetabular ORIF. Mean intraoperative blood loss between the 2 approaches. Results: CS blood was returned in 29 of the 145 total cases [23/65 anterior (ilioinguinal approach) and 6/80 posterior approach (Kocher–Langenbeck)]. Mean intraoperative blood loss was 786 mL for the anterior approach and 485 mL for the posterior approach. Subgroup analysis identified anterior approach as the only risk factor for elevated blood loss and CS blood return. Conclusions: CS is not indicated for routine use when performing ORIF of the acetabulum. Use of the CS may be warranted with anterior approaches if large amounts of blood loss are anticipated. Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Immediate Weight-Bearing after Ankle Fracture Fixation

We believe that a certain subset of surgical ankle fracture patients can be made weight-bearing as tolerated immediately following surgery. Immediate weight-bearing as tolerated (IWBAT) allows patients to return to ambulation and activities of daily living faster and may facilitate rehabilitation. A prospectively gathered orthopaedic trauma database at a Level 1 trauma center was reviewed retrospectively to identify patients who had ORIF after unstable ankle injuries treated by the senior author. Patients were excluded if they were not IWBAT based on specific criteria or if they did meet followup requirement. Only 1/26 patients was noted to have loss of fixation. This was found at the 6-week followup and was attributed to a missed syndesmotic injury. At 2-week followup, 2 patients had peri-incisional erythema that resolved with a short course of oral antibiotics. At 6-week followup, 20 patients were wearing normal shoes and 6 patients continued to wear the CAM Boot for comfort. To conclude, IWBAT in a certain subset of patients with stable osteosynthesis following an ankle fracture could potentially be a safe alternative to a period of protected weight-bearing.

Entrapped Posteromedial Structures in Pilon Fractures

Objectives: To analyze a patient cohort who sustained a tibial pilon fracture and report the incidence of interposed posteromedial soft tissue structures. Design: Retrospective cohort review. Setting: Regional Level 1 Trauma Center. Patients/Participants: About 394 patients with 420 pilon fractures treated between January 2005 and November 2011. Intervention: Each patients preoperative radiographs and computed tomography (CT) images were reviewed. The axial and reconstructed images were used in bone and soft tissue windows to identify any posteromedial soft tissue structures incarcerated within the fracture. Main Outcome Measurements: Medical charts reviewed for the presence of preoperative neurologic deficit, separate posteromedial incision, and whether attending radiology CT interpretation noted the interposed structure. Results: 40 patients with 40 fractures (9.5%) had an entrapped posteromedial structure. The tibialis posterior tendon was interposed in 38/40 fractures (95%) and the posterior tibial neurovascular bundle in 4/40 fractures (10%). Preoperative neurologic deficit occurred in 5/40 patients (12%). A posteromedial incision was used in 11/40 fractures (27%). The attending radiology CT interpretation noted the interposed structure in 8/40 fractures (20%). Conclusions: In addition to the osseous injuries, CT imaging can demonstrate the posteromedial soft tissue structures. In our series, the tibialis posterior tendon was commonly incarcerated. In some cases, removal of the entrapped structure(s) may not be possible through the more commonly used anterolateral and anteromedial surgical approaches, and a separate posteromedial exposure may be required. Failure to recognize the presence of an interposed structure could lead to malreduction, impaired tendon function, neurovascular insult, and the need for further surgery. Level of Evidence: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.