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Calcar

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Surena Namdari – 1st expert on this subject based on the ideXlab platform

  • failure to restore the Calcar and locking screw cross threading predicts varus collapse in proximal humerus fracture fixation
    Journal of Shoulder and Elbow Surgery, 2020
    Co-Authors: Eric M Padegimas, Gerard Chang, Kamran Namjouyan, Surena Namdari

    Abstract:

    Background Varus collapse is a common failure mode of proximal humerus fracture (PHF) fixation. The purpose of this study was to analyze predictors of varus collapse of PHF after open reduction, internal fixation (ORIF). Methods All patients who underwent ORIF of a PHF from January 2008 to July 2018 were identified. Known predictors of fixation failure were assessed, including Calcar distance, Calcar ratio, and Calcar restoration. Additionally, the presence of cross-threaded screws was determined. The primary outcome analyzed was varus collapse of the fracture defined as a change in neck shaft angulation to less than 120°. Results There were 112 patients identified who underwent ORIF of a PHF that met inclusion criteria. The population was 75.0% female (84/112), average age was 62.5 ± 10.4 years (range 40.0-87.9), and average body mass index was 28.0 ± 5.5 (17.5-46.4). There were 17 with varus collapse. In 11 of the 17 patients (64.7%), there was screw cross-threading (vs. 31/95 [32.6%] in those that did not collapse); P = .012. In addition, 8 of the 17 (47.1%) did not have restoration of the Calcar (vs. 16/95 [16.8%]; P = .005). Conclusion This study identifies 2 surgeon-controlled variables that can contribute to varus collapse after ORIF of PHFs. Cross-threading of locking screws and failure to restore the medial Calcar can be a function of implant design, surgeon technical skill, and/or bone quality.

  • Calcar screw position in proximal humerus fracture fixation don t miss high
    Injury-international Journal of The Care of The Injured, 2018
    Co-Authors: Samir Mehta, Surena Namdari, Matthew Chin, Jennifer Sanville, Michael W Hast

    Abstract:

    Abstract Introduction In locked plate fixation of proximal humerus fractures, the Calcar is an important anchor point for screws providing much-needed medial column support. Most locking plate implants utilize a fixed-trajectory locking screw to achieve this goal. Consequently, adjustments of plate location to account for patient-specific anatomy may result in a screw position outside of the Calcar. To date, little is known about the consequences of “missing” the Calcar during plate positioning. This study sought to characterize the biomechanics associated with proximal and distal placement of locking plates in a two-part fracture model. Materials and methods This experiment was performed twice, first with elderly cadaveric specimens and again with osteoporotic sawbones. Two-part fractures were simulated and specimens were divided to represent proximal, neutral, and distal plate placements. Non-destructive torsional and axial compression tests were performed prior to an axial fatigue test and a ramp to failure. Torsional stiffness, axial stiffness, humeral head displacement and stiffness during fatigue testing, and ultimate load were compared between groups. Results Cadavers: Proximal implant placement led to trends of decreased mechanical properties, but there were no significant differences found between groups. Sawbones: Distal placement increased torsional stiffness in both directions (p = 0.003, p = 0.034) and axial stiffness (p = 0.018) when compared to proximal placement. Distal placement also increased torsional stiffness in external rotation (p = 0.020), increased axial stiffness (p = 0.024), decreased humeral head displacement during fatigue testing, and increased stiffness during fatigue testing when compared to neutral placement. Discussion The distal and neutral groups had similar mechanical properties in many cadaveric comparisons while the proximal group trended towards decreased construct stiffness. Results from the Sawbones model were more definitive and provided further evidence that proximal Calcar screw placements are undesirable and distal implant placement may provide improved construct stability. Conclusion Successful proximal humerus fracture reconstruction is inherent upon anatomic fracture reduction coupled with medial column support. Results from this experiment suggest that missing the Calcar proximally is deleterious to fixation strength, while it is safe, and perhaps even desirable, to aim slightly distal to the intended target.

  • defining optimal Calcar screw positioning in proximal humerus fracture fixation
    Journal of Shoulder and Elbow Surgery, 2017
    Co-Authors: Eric M Padegimas, Benjamin Zmistowski, Cassandra Lawrence, Aaron Palmquist, Thema Nicholson, Surena Namdari

    Abstract:

    Background Anatomic reduction and placement of an inferior Calcar screw are strategies to prevent fixation failure in proximal humerus factures. Optimal position of the Calcar screw remains unknown. Methods There were 168 shoulders (68.5% female; average age, 63.6 ± 11.5 years) that underwent open reduction and internal fixation of a displaced proximal humerus fracture involving the surgical or anatomic neck. Univariate and multivariate analyses were performed on preoperative clinical, preoperative radiographic, and postoperative radiographic variables to determine association with fixation failure. A receiver operating characteristic curve was performed to determine a maximum distance from the inferior screw to the Calcar (“Calcar distance”) as well as a maximum ratio of this distance and the head diameter (“Calcar ratio”). Results There were 26 of 168 (15.5%) patients with radiographic failures (19 related to fixation failure). Univariate analysis and multivariate analyses found quality of reduction (P  Conclusions Quality of reduction, Calcar distance, and Calcar ratio independently correlated with fixation failure. This study provides optimal distances and ratios for Calcar screw placement that can be used clinically.

Maria Byrne – 2nd expert on this subject based on the ideXlab platform

  • noncalcifying larvae in a changing ocean warming not acidification hypercapnia is the dominant stressor on development of the sea star meridiastra Calcar
    Global Change Biology, 2012
    Co-Authors: Hong D Nguyen, Natalie A Soars, Maria Byrne

    Abstract:

    Climate change driven ocean warming and acidification is potentially detrimental to the sensitive planktonic life stages of benthic marine invertebrates. Research has focused on the effects of acidification on calcifying larvae with a paucity of data on species with alternate developmental strategies and on the interactive effects of warming and acidification. To determine the impact of climate change on a conspicuous component of the intertidal fauna of southeast Australia, the development of the noncalcifying lecithotrophic larvae of the sea star Meridiastra Calcar was investigated in the setting of predicted ocean warming (+2 to 4 °C) and acidification (−0.4 to 0.6 pH units) for 2100 and beyond in all combinations of stressors. Temperature and pH were monitored in the habitat of M. Calcar to place experiments in context with current environmental conditions. There was no effect of temperature or pH on cleavage stage embryos but later development (gastrula-larvae) was negatively effected by a +2 to 4 °C warming and there was a negative effect of −0.6 pH units on embryos reaching the hatched gastrula stage. Mortality and abnormal development in larvae increased significantly even with +2 °C warming and larval growth was impaired at +4 °C. For the range of temperature and pH conditions tested, there were no interactive effects of stressors across all stages monitored. For M. Calcar, warming not acidification was the dominant stressor. A regression model incorporating data from this study and projected increasing SST for the region suggests an increase in larval mortality to 70% for M. Calcar by 2100 in the absence of acclimation and adaptation. The broad distribution of this species in eastern Australia encompassing subtropical to cold temperate thermal regimes provides the possibility that local M. Calcar populations may be sustained in a warming world through poleward migration of thermotolerant propagules, facilitated by the strong southward flow of the East Australian Current.

  • Noncalcifying larvae in a changing ocean: warming, not acidification/hypercapnia, is the dominant stressor on development of the sea star Meridiastra Calcar
    Global Change Biology, 2012
    Co-Authors: Hong D Nguyen, Natalie A Soars, Maria Byrne

    Abstract:

    Climate change driven ocean warming and acidification is potentially detrimental to the sensitive planktonic life stages of benthic marine invertebrates. Research has focused on the effects of acidification on calcifying larvae with a paucity of data on species with alternate developmental strategies and on the interactive effects of warming and acidification. To determine the impact of climate change on a conspicuous component of the intertidal fauna of southeast Australia, the development of the noncalcifying lecithotrophic larvae of the sea star Meridiastra Calcar was investigated in the setting of predicted ocean warming (+2 to 4 °C) and acidification (−0.4 to 0.6 pH units) for 2100 and beyond in all combinations of stressors. Temperature and pH were monitored in the habitat of M. Calcar to place experiments in context with current environmental conditions. There was no effect of temperature or pH on cleavage stage embryos but later development (gastrula-larvae) was negatively effected by a +2 to 4 °C warming and there was a negative effect of −0.6 pH units on embryos reaching the hatched gastrula stage. Mortality and abnormal development in larvae increased significantly even with +2 °C warming and larval growth was impaired at +4 °C. For the range of temperature and pH conditions tested, there were no interactive effects of stressors across all stages monitored. For M. Calcar, warming not acidification was the dominant stressor. A regression model incorporating data from this study and projected increasing SST for the region suggests an increase in larval mortality to 70% for M. Calcar by 2100 in the absence of acclimation and adaptation. The broad distribution of this species in eastern Australia encompassing subtropical to cold temperate thermal regimes provides the possibility that local M. Calcar populations may be sustained in a warming world through poleward migration of thermotolerant propagules, facilitated by the strong southward flow of the East Australian Current.

  • development of the hyaline layer around the planktonic embryos and larvae of the asteroid patiriella Calcar and the presence of associated bacteria
    Invertebrate Reproduction & Development, 1997
    Co-Authors: Anna Cerra, Maria Byrne, Ove Hoeghguldberg

    Abstract:

    Summary The hyaline layer (HL) around the embryos and larvae of Patiriella Calcar is examined by transmission electron microscopy. P. Calcar hatches at the gastrula stage and develops through a lecithotrophic planktonic brachiolaria. The hyaline layer of unhatched P. Calcar is poorly developed and is comprised of wispy fibrils scattered among the epithelial microvilli. Fibrils are also occasionally seen associated with the inner surface of the fertilization envelope. By the hatched gastrula stage, the hyaline layer is organized into three strata: the intervillous layer, the supporting layer and the coarse outer meshwork layer. Seven-day-old brachiolaria also have a hyaline layer comprised of three strata. In these larvae the supporting layer elevates away from the epithelial surface due to the tuft-like organization of the underlying microvilli. This results in the formation of local outpockets giving the surface of the HL a lobed appearance. Bacteria are occassionally seen in the intervillous layer, part…

Junkyung Hwang – 3rd expert on this subject based on the ideXlab platform

  • cementless Calcar replacement hemiarthroplasty compared with intramedullary fixation of unstable intertrochanteric fractures a prospective randomized study
    Journal of Bone and Joint Surgery American Volume, 2005
    Co-Authors: Junkyung Hwang

    Abstract:

    Background: Unstable intertrochanteric fractures in elderly patients are associated with a high rate of complications. The purpose of this investigation was to compare the results of long-stem cementless Calcar-replacement hemiarthroplasty with those of treatment with a proximal femoral nail for unstable intertrochanteric fractures in elderly patients.

    Methods: Fifty-eight elderly patients with an AO/OTA type 31-A2 intertrochanteric fracture of the femur were randomized into two treatment groups and were followed for a minimum of two years. The twenty-nine patients in Group I were treated with a long-stem cementless Calcar-replacement prosthesis, and the twenty-nine patients in Group II were treated with a proximal femoral nail. The two treatment groups were comparable with regard to demographic and injury variables.

    Results: There were no significant differences between the groups in terms of functional outcomes, hospital stay, time to weight-bearing, or general complications. Patients treated with a proximal femoral nail had a shorter operative time, less blood loss, fewer units of blood transfused, a lower mortality rate, and lower hospital costs compared with those treated with the long-stem cementless Calcar-replacement prosthesis.

    Conclusions: In elderly patients with an unstable intertrochanteric femoral fracture, a proximal femoral nail provides superior clinical outcomes but no advantage with regard to functional outcome when compared with a long-stem cementless Calcar-replacement arthroplasty.

    Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.