Positioning patients for spine surgery is pivotal for optimal operating conditions and operative-site exposure. During spine surgery, patients are placed in positions that are not physiologic and may lead to complicat...Positioning patients for spine surgery is pivotal for optimal operating conditions and operative-site exposure. During spine surgery, patients are placed in positions that are not physiologic and may lead to complications. Perioperative peripheral nerve injury(PPNI) and postoperative visual loss(POVL) are rare complications related to patient positioning during spine surgery that result in significant patient disability and functional loss. PPNI is usually due to stretch or compression of the peripheral nerve. PPNI may present as a brachial plexus injury or as an isolated injury of single nerve, most commonly the ulnar nerve. Understanding the etiology, mechanism and pattern of injury with each type of nerve injury is important for the prevention of PPNI. Intraoperative neuromonitoring has been used to detect peripheral nerve conduction abnormalities indicating peripheral nerve stress under general anesthesia and to guide modification of the upper extremity position to prevent PPNI. POVL usually results in permanent visual loss. Most cases are associated with prolonged spine procedures in the prone position under general anesthesia. The most common causes of POVL after spine surgery are ischemic optic neuropathy and central retinal artery occlusion. Posterior ischemic opticneuropathy is the most common cause of POVL after spine surgery. It is important for spine surgeons to be aware of POVL and to participate in safe, collaborative perioperative care of spine patients. Proper education of perioperative staff, combined with clear communication and collaboration while positioning patients in the operating room is the best and safest approach. The prevention of uncommon complications of spine surgery depends primarily on identifying high-risk patients, proper positioning and optimal intraoperative management of physiological parameters. Modification of risk factors extrinsic to the patient may help reduce the incidence of PPNI and POVL.展开更多
Flanks of end mills are prone to wear in a long machining process.Regrinding is widely used in workshops to restore the flank to an original-like state.However,the traditional method involves material waste by trial a...Flanks of end mills are prone to wear in a long machining process.Regrinding is widely used in workshops to restore the flank to an original-like state.However,the traditional method involves material waste by trial and error and dramatically decreases the potential regrinding.Moreover,over-cut would happen to the flutes of worn cutters in the regrinding processes because of improper wheel path.This study presented a new approach to planning the wheel path for regrinding worn end mills to minimize material loss and recover the over-cut.In planning,a scaling method was developed to determine the maximum size of the new cutter according to the similarity of cutter shapes before and after regrinding.Then,the wheel path is first generated by envelope theory to regrind the worn area with a four-axis computer numerical control grinder according to the new size of cutters.Moreover,a second regrinding strategy is applied to recover the flute shape over-cut in the first grinding.Finally,the proposed method is verified by an experiment.Results showed that the proposed approach could save 25%of cutter material compared with the traditional method and ensure at least three regrinding times.This work effectively provides a general regrinding solution for the worn flank with maximum material-saving and regrinding period.展开更多
文摘Positioning patients for spine surgery is pivotal for optimal operating conditions and operative-site exposure. During spine surgery, patients are placed in positions that are not physiologic and may lead to complications. Perioperative peripheral nerve injury(PPNI) and postoperative visual loss(POVL) are rare complications related to patient positioning during spine surgery that result in significant patient disability and functional loss. PPNI is usually due to stretch or compression of the peripheral nerve. PPNI may present as a brachial plexus injury or as an isolated injury of single nerve, most commonly the ulnar nerve. Understanding the etiology, mechanism and pattern of injury with each type of nerve injury is important for the prevention of PPNI. Intraoperative neuromonitoring has been used to detect peripheral nerve conduction abnormalities indicating peripheral nerve stress under general anesthesia and to guide modification of the upper extremity position to prevent PPNI. POVL usually results in permanent visual loss. Most cases are associated with prolonged spine procedures in the prone position under general anesthesia. The most common causes of POVL after spine surgery are ischemic optic neuropathy and central retinal artery occlusion. Posterior ischemic opticneuropathy is the most common cause of POVL after spine surgery. It is important for spine surgeons to be aware of POVL and to participate in safe, collaborative perioperative care of spine patients. Proper education of perioperative staff, combined with clear communication and collaboration while positioning patients in the operating room is the best and safest approach. The prevention of uncommon complications of spine surgery depends primarily on identifying high-risk patients, proper positioning and optimal intraoperative management of physiological parameters. Modification of risk factors extrinsic to the patient may help reduce the incidence of PPNI and POVL.
基金supported by the National Key R&D Program of China(Grant No.2020YFB1711603)the Key Technology R&D Program of Shandong Province,China(Grant No.2020CXGC010304)the National Natural Science Foundation of China(Grant No.52175473).
文摘Flanks of end mills are prone to wear in a long machining process.Regrinding is widely used in workshops to restore the flank to an original-like state.However,the traditional method involves material waste by trial and error and dramatically decreases the potential regrinding.Moreover,over-cut would happen to the flutes of worn cutters in the regrinding processes because of improper wheel path.This study presented a new approach to planning the wheel path for regrinding worn end mills to minimize material loss and recover the over-cut.In planning,a scaling method was developed to determine the maximum size of the new cutter according to the similarity of cutter shapes before and after regrinding.Then,the wheel path is first generated by envelope theory to regrind the worn area with a four-axis computer numerical control grinder according to the new size of cutters.Moreover,a second regrinding strategy is applied to recover the flute shape over-cut in the first grinding.Finally,the proposed method is verified by an experiment.Results showed that the proposed approach could save 25%of cutter material compared with the traditional method and ensure at least three regrinding times.This work effectively provides a general regrinding solution for the worn flank with maximum material-saving and regrinding period.
