BACKGROUND Missed or delayed diagnosis of cervical spine instability after acute trauma can have catastrophic consequences for the patient,resulting in severe neurological impairment.Currently,however,there is no cons...BACKGROUND Missed or delayed diagnosis of cervical spine instability after acute trauma can have catastrophic consequences for the patient,resulting in severe neurological impairment.Currently,however,there is no consensus on the optimal strategy for diagnosing occult cervical spine instability.Thus,we present a case of occult cervical spine instability and provide a clinical algorithm to aid physicians in diagnosing occult instability of the cervical spine.CASE SUMMARY A 57-year-old man presented with cervical spine pain and inability to stand following a serious fall from a height of 2 m.No obvious vertebral fracture or dislocation was found at the time on standard lateral X-ray,computed tomography,and magnetic resonance imaging(MRI).Subsequently,the initial surgical plan was unilateral open-door laminoplasty(C3-7)with alternative levels of centerpiece mini-plate fixation(C3,5,and 7).However,the intraoperative C-arm fluoroscopic X-rays revealed significantly increased intervertebral space at C5-6,indicating instability at this level that was previously unrecognized on preoperative imaging.We finally performed lateral mass fixation and fusion at the C5-6 level.Looking back at the preoperative images,we found that the preoperative T2 MRI showed non-obvious high signal intensity at the C5-6 intervertebral disc and posterior interspinous ligament.CONCLUSION MRI of cervical spine trauma patients should be carefully reviewed to detect disco-ligamentous injury,which will lead to further cervical spine instability.In patients with highly suspected cervical spine instability indicated on MRI,lateral X-ray under traction or after anesthesia and muscle relaxation needs to be performed to avoid missed diagnoses of occult cervical instability.展开更多
Sample size re-estimation is essential in oncology studies. However, the use of blinded sample size reassessment for survival data has been rarely reported. Based on the density function of the exponential distributio...Sample size re-estimation is essential in oncology studies. However, the use of blinded sample size reassessment for survival data has been rarely reported. Based on the density function of the exponential distribution, an expectation-maximization（EM） algorithm of the hazard ratio was derived, and several simulation studies were used to verify its applications. The method had obvious variation in the hazard ratio estimates and overestimation for the relatively small hazard ratios. Our studies showed that the stability of the EM estimation results directly correlated with the sample size, the convergence of the EM algorithm was impacted by the initial values, and a balanced design produced the best estimates. No reliable blinded sample size re-estimation inference can be made in our studies, but the results provide useful information to steer the practitioners in this field from repeating the same endeavor.展开更多
基金Supported by grants from China Postdoctoral Science Foundation General Program No.2019M653417Sichuan Science and Technology Program,No.2020YJ0025,No.2017SZ0046,and No.2017SZDZX0021+1 种基金Post-Doctor Research Project,Sichuan University,No.2019SCU12043and International Postdoctoral Exchange Fellowship Program,No.PC2019060.
文摘BACKGROUND Missed or delayed diagnosis of cervical spine instability after acute trauma can have catastrophic consequences for the patient,resulting in severe neurological impairment.Currently,however,there is no consensus on the optimal strategy for diagnosing occult cervical spine instability.Thus,we present a case of occult cervical spine instability and provide a clinical algorithm to aid physicians in diagnosing occult instability of the cervical spine.CASE SUMMARY A 57-year-old man presented with cervical spine pain and inability to stand following a serious fall from a height of 2 m.No obvious vertebral fracture or dislocation was found at the time on standard lateral X-ray,computed tomography,and magnetic resonance imaging(MRI).Subsequently,the initial surgical plan was unilateral open-door laminoplasty(C3-7)with alternative levels of centerpiece mini-plate fixation(C3,5,and 7).However,the intraoperative C-arm fluoroscopic X-rays revealed significantly increased intervertebral space at C5-6,indicating instability at this level that was previously unrecognized on preoperative imaging.We finally performed lateral mass fixation and fusion at the C5-6 level.Looking back at the preoperative images,we found that the preoperative T2 MRI showed non-obvious high signal intensity at the C5-6 intervertebral disc and posterior interspinous ligament.CONCLUSION MRI of cervical spine trauma patients should be carefully reviewed to detect disco-ligamentous injury,which will lead to further cervical spine instability.In patients with highly suspected cervical spine instability indicated on MRI,lateral X-ray under traction or after anesthesia and muscle relaxation needs to be performed to avoid missed diagnoses of occult cervical instability.
基金supported by the National Natural Science Foundation of China(81273184)the National Natural Science Foundation of China Grant for Young Scientists (81302512)
文摘Sample size re-estimation is essential in oncology studies. However, the use of blinded sample size reassessment for survival data has been rarely reported. Based on the density function of the exponential distribution, an expectation-maximization（EM） algorithm of the hazard ratio was derived, and several simulation studies were used to verify its applications. The method had obvious variation in the hazard ratio estimates and overestimation for the relatively small hazard ratios. Our studies showed that the stability of the EM estimation results directly correlated with the sample size, the convergence of the EM algorithm was impacted by the initial values, and a balanced design produced the best estimates. No reliable blinded sample size re-estimation inference can be made in our studies, but the results provide useful information to steer the practitioners in this field from repeating the same endeavor.
