***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Abstract Purpose Surgical options in the treatment of recurrent anterior shoulder instability are numerous . The Latarjet procedure is one of the most common procedures performed . It has been previously demonstrated that bone mineral density decreases with age . This reduction thus increases the risk of osteoporosis and osteoporosis-related iatrogenic , traumatic or pathological fractures . The objective of this study was to quantify the bone mineral density of the coracoid process in different age groups . The hypothesis was that mineral bone density of the coracoid process decreases with age . Methods Using the hospital ’s electronic data base , 60 patients who underwent a shoulder CT scan were r and omly selected retrospectively . Four groups of 15 were formed with mean ages of 20 , 30 , 40 and 50 years . Bone density , length , width and thickness of the coracoid process 10 mm from the tip were measured four times by two different evaluators . Bone density was expressed in Hounsfield units ( HU ) . Results The mean bone mineral density of the coracoid process significantly decreased with age ( p < 0.0001 ) . A lower but insignificant difference of bone mineral density was observed in females . A good inter- and intra-observer reliability was found for bone mineral density measurement of the coracoid process ( 0.67 and 0.7 , respectively ) . Conclusions The bone mineral density of the coracoid process diminishes with age , thus confirming our hypothesis . There is a good inter- and intra-observer reliability of our CT scan-based coracoid process bone mineral density measurement rendering it reproducible in daily clinical practice .Level of evidence IV Study Design . Retrospective case-control study . Objective . To determine the association of Hounsfield unit ( HU ) measurements with adjacent segment fractures after spinal fusion . Summary of Background Data . Adjacent segment fracture is a potentially devastating complication after spinal fusion surgery in osteoporotic patient . Recently , a technique for assessing bone mineral density using HU measurements from computed tomography was described and correlated with both dual-energy x-ray absorptiometry – assessed bone mineral density and compressive strength in an osseous model . Methods . Patients with adjacent segment fractures after spinal fusion were identified from a prospect ively collected patient data base and matched 1:1 with nonfracture controls on the basis of age , sex , and fusion construct . Minimum follow-up was 6 months . Patients with metabolic bone disease other than osteoporosis or those taking medications known to negatively alter bone strength were excluded .  HU assessment was done according to the previously published protocol using the preoperative computed tomography . Results . Twenty patients had complete imaging data and could be matched to nonfracture  controls  . The groups were well matched with respect to age , sex , body mass index , and number of levels fused . Following the index surgical procedure , the fracture group had more positive sagittal balance than the control group ( 10.7 cm vs. 9.1 cm ) . Analysis of HU values at the fracture level showed a significantly lower value in the fracture group than in the controls ( 145.6 vs. 199.4 , P = 0.006 ) . Similarly , global assessment of HU across the thoracic and lumbar spines was significantly lower in the fracture group ( 139.9 vs. 170.1 , P = 0.032 ) . Conclusion . HU was significantly lower both locally and globally in the fracture cohort . Because computed tomographic scans are frequently part of preoperative planning for spinal fusion , this information should be incorporated in preoperative planning . Studies to prospect ively vali date HU as a predictor of adjacent segment fracture risk and to assess the effect of increasing HU preoperatively with medications for osteoporosis are needed . Level of Evidence : Background Iliosacral screw fixation has become a common method for surgical stabilization of acute disruptions of the pelvic ring . Placement of iliosacral screws into the first sacral ( S1 ) body is the preferred method of fixation , but size limitations and sacral dysmorphism may preclude S1 fixation . In these clinical situations , fixation into the second sacral ( S2 ) body has been recommended . The objective of this study was to evaluate the bone quality of the S1 compared to S2 in the described “ safe zone ” of iliosacral screw fixation in trauma patients . Material s and methods The pelvic computed tomography scans of 25 consecutive trauma patients , ages 18–49 , at a level 1 trauma center were prospect ively analyzed . Hounsfield units , a st and ardized computed tomography attenuation coefficient , was utilized to measure regional cancellous bone mineral density of the S1 and S2 . No change in the clinical protocol or treatment occurred as a consequence of inclusion in this study . Results A statically significant difference in bone quality was found when comparing the first and second sacral segment ( p = 0.0001 ) . Age , gender , or smoking status did not independently affect bone quality . Conclusion In relatively young , otherwise healthy trauma patients there is a statistically significant difference in the bone density of the first sacral segment compared to the second sacral segment . This study highlights the need for future biomechanical studies to investigate whether this difference is clinical ly relevant . Due to the relative osteopenia in the second sacral segment , which may impact the quality of fixation , we feel this technique should be used with caution .Level of evidence INTRODUCTION Patients with a fracture in the anterior pelvic ring often simultaneously demonstrate pain in the posterior pelvic ring . The aim of the present prospect i ve study was to assess the sensitivity of CT , MRI and clinical examination in the detection of fractures in the posterior pelvic ring in patients with fractures of the anterior pelvic ring diagnosed in conventional radiographs . METHODS Sixty patients with radiographic signs of an anterior pelvic ring injury were included in this prospect i ve analysis . Following a focused clinical examination of the posterior pelvis , all patients underwent both a CT and then a MRI scan of their pelvis . Two board certified radiologists evaluated the CT and MRI scans independently . To estimate the presence of osteoporosis the Hounsfield units of the vertebral body of L5 were measured in each case . RESULTS Fifty-three women and seven men , with a mean age of 74.7+/-15.6 years were included into the study . A fracture of the posterior pelvic ring was found in fourty-eight patients ( 80 % ) patients using MRI .  Fractures of the posterior pelvic ring would have been missed in eight cases ( 17 % ) , if only CT had been used . Eighty-five percent of the patients with a posterior fracture had an osteoporosis . The majority of the cases suffered from a low energy trauma . Thirty-eight patients ( 83 % ) with positive clinical signs at the posterior pelvic ring actually had a fracture of the posterior pelvic ring in the MRI . The clinical examination proved to be equally effective to CT in detecting posterior pelvic ring fractures . CONCLUSION The significance of both , clinical examination and CT was confirmed in the detection of fractures in the posterior pelvic ring .  MRI examination of the pelvis however , was found to be superior in detecting undislocated fractures in a cohort of patients with a high incidence of osteoporosis . Using MRI may be beneficial in select cases , especially when reduced bone density is suspected Abstract Objectives Further survival benefits may be gained from low-dose chest computed tomography ( CT ) by assessing vertebral fractures and bone density . We sought to assess the association between CT-measured vertebral fractures and bone density with all-cause mortality in lung cancer screening participants . Methods Following a case-cohort design , lung cancer screening trial participants ( N = 3,673 ) who died ( N = 196 ) during a median follow-up of 6 years ( inter-quartile range : 5.7–6.3 ) were identified and added to a r and om sample of N = 383 from the trial . We assessed vertebral fractures using Genant´s semiquantative method on sagittal reconstructions and measured bone density ( Hounsfield Units ( HU ) ) in vertebrae . Cox proportional hazards modelling was used to determine if vertebral fractures or bone density were independently predictive of mortality . Results The prevalence of vertebral fractures was 35 % ( 95 % confidence interval 30–40 % ) among survivors and 51 % ( 44–58 % ) amongst cases . After adjusting for age , gender , smoking status , pack years smoked , coronary and aortic calcium volume and pulmonary emphysema , the adjusted hazard ratio ( HR ) for vertebral fracture was 2.04 ( 1.43–2.92 ) . For each 10 HU decline in trabecular bone density , the adjusted HR was 1.08 ( 1.02–1.15 ) . Conclusions Vertebral fractures and bone density are independently associated with all-cause mortality . Key Points• Lung cancer screening chest computed tomography contains additional , potentially useful information . • Vertebral fractures and bone density are independently predictive of mortality . • This finding has implication s for screening and management decisions BACKGROUND CONTEXT The use of a novel lumbar pedicle cortical bone trajectory ( CBT ) screw has recently gained popularity , allowing for a minimally invasive approach and potentially improved screw purchase . However , to date , no studies have identified the ideal patient population to utilize this technology . PURPOSE This study reports the bone mineral density ( BMD ) using Hounsfield units ( HUs ) along a CBT screw pathway . Patients with a greater difference in density of bone in the lumbar vertebrae between the fixation points of the CBT and traditional pedicle screw may be optimal c and i date s to realize the advantages of this technique . STUDY DESIGN / SETTING A cross-sectional observational anatomic study was carried out . PATIENT SAMPLE The sample comprised 180 r and omly selected patients with lumbar computed tomography imaging from L1 to L5 spinal levels . OUTCOME MEASURES This study used computed tomography image-derived HUs as a metric for BMD . METHODS A total of 180 patients without previous lumbar surgery with computed tomography imaging of the lumbar spine met the inclusion criteria . Patients were chosen r and omly from an institutional data base based on age ( evenly distributed by decade of life ) and gender .  Hounsfield units were measured at the expected end fixation point for both a cortical ( superior/posterior portion of the vertebral body ) and traditional pedicle trajectory ( mid-vertebral body ) . RESULTS Hounsfield unit values measured at the end fixation point for the CBT screw were significantly greater than that of the traditional pedicle screw in all age groups . The relative difference in HU values significantly increased with each decade of age ( p<.001 ) and caudal lumbar level ( p<.001 ) . In the osteoporotic group , as determined by well-established HU values , there was a significantly greater difference in the BMD of the CBT  fixation point compared with the traditional trajectory ( p=.048-<.001 ) . CONCLUSIONS Bone mineral density as measured by HU values for the fixation point of the CBT screw is significantly greater than that of the traditional pedicle screw . This difference is even more pronounced when comparing osteoporotic and elderly patients to the general population . The data in this study suggest that the potential advantages from the CBT screw such as screw purchase may increase linearly with age and in osteoporotic patients Background :  Double-bundle anterior cruciate ligament ( ACL ) reconstruction  is a technically dem and ing procedure ; it requires drilling 2 tibial and 2 femoral tunnels . Tunnel communication , whether intraoperative or postoperative , is a serious complication : It jeopardizes knee stability and graft function . Hypothesis : During double-bundle ACL reconstruction , special aim ers would be helpful to avoid intraoperative bone bridge fracture . The bone bridge between the bone tunnels would maintain its structural integrity , and no tunnel communication would be observed postoperatively because of tunnel widening . Study design : Case series ; Level of evidence , 4 . Methods : This prospect i ve study included 32 patients undergoing double-bundle ACL reconstruction .  A multidetector computed tomography study was performed at a mean of 17 months postoperatively . The thickness of the bone bridge between the bone tunnels was measured in the femoral and tibial sides on an axial and sagittal plane , respectively , at 3 locations : the level of the joint line , the midportion of the bone bridge , and the base of the bone bridge . The bone density of the bone bridge was measured in Hounsfield units in the same locations . Bone density of the anterior tibial cortex and lateral femoral condyle was measured for comparisons . Results : Tunnel communication occurred intraoperatively in 1 patient on the tibial side at the level of the joint line . In the rest of the patients , a well-defined triangular bone bridge was present between the 2 tunnels in the femoral and tibial sides . The thickness at the apex of the bone bridge was 2.0 and 2.2 mm for the femur and tibia , respectively . In addition , the density of the bone bridge at its apex was similar to that of cortical bone . Conclusion : This study demonstrated that double-bundle ACL reconstruction , as used with anatomic aim ers , produces a low rate of tunnel convergence . The bone bridge remains intact postoperatively , although it is thin at the level of the joint line BACKGROUND CONTEXT Spinous process fracture is a recognized complication associated with  interspinous process spacer ( IPS ) surgery .  Although occasionally identified by plain radiographs , computed tomography ( CT ) appears to identify a higher rate of such fractures . Although osteoporotic insufficiency fracture is considered a contraindication for IPS surgery , a formal risk factor analysis for this complication has not previously been reported . PUR 
    Output:
    
Conclusions : Direct HU measurement from diagnostic CT scans has the potential to be used opportunistically for osteoporosis screening , but in its current state it is not ready for clinical implementation .