paraplegia (asia a), this applies to lesion heights between t12 and s5. in patients with incomplete paraplegia (asia b-d), orthoses are even suitable for lesion heights above t12. in both cases, however, a detailed muscle function test must be carried out to precisely plan the construction with an orthosis. prognosis holly koester incurred a spinal injury as a result of a motor vehicle collision and is now a wheelchair racer. spinal cord injuries generally result in at least some incurable impairment even with the best possible treatment. the best predictor of prognosis is the level and completeness of injury, as measured by the asia impairment scale. the neurological score at the initial evaluation done 72 hours after injury is the best predictor of how much function will return. most people with asia scores of a (complete injuries) do not have functional motor recovery, but improvement can occur. most patients with incomplete injuries recover at least some function. chances of recovering the ability to walk improve with each ais grade found at the initial examination; e.g. an asia d score confers a better chance of walking than a score of c. the symptoms of incomplete injuries can vary and it is difficult to make an accurate prediction of the outcome. a person with a mild, incomplete injury at the t5 vertebra will have a much better chance of using his or her legs than a person with a severe, complete injury at exactly the same place. of the incomplete sci syndromes, brown-séquard and central cord syndromes have the best prognosis for recovery and anterior cord syndrome has the worst. people with nontraumatic causes of sci have been found to be less likely to develop complete injuries and some complications such as pressure sores and deep vein thrombosis, and to have shorter hospital stays. their scores on functional tests were better than those of people with traumatic sci upon hospital admission, but when they were tested upon discharge, those with traumatic sci had improved such that both groups' results were the same. in addition to the completeness and level of the injury, age and concurrent health problems affect the extent to which a person with sci will be able to live independently and to walk. however, in general people with injuries to l3 or below will likely be able to walk functionally, t10 and below to walk around the house with bracing, and c7 and below to live independently. new therapies are beginning to provide hope for better outcomes in patients with sci, but most are in the experimental/translational stage. one important predictor of motor recovery in an area is presence of sensation there, particularly pain perception. most motor recovery occurs in the first year post-injury, but modest improvements can continue for years; sensory recovery is more limited. recovery is typically quickest during the first six months. spinal shock, in which reflexes are suppressed, occurs immediately after the injury and resolves largely within three months but continues resolving gradually for another 15. sexual dysfunction after spinal injury is common. problems that can occur include erectile dysfunction, loss of ability to ejaculate, insufficient lubrication of the vagina, and reduced sensation and impaired ability to orgasm. despite this, many people learn ways to adapt their sexual practices so they can lead satisfying sex lives. although life expectancy has improved with better care options, it is still not as good as the uninjured population. the higher the level of injury, and the more complete the injury, the greater the reduction in life expectancy. mortality is very elevated within a year of injury. epidemiology breakdown of age at time of injury in the us from 1995–1999. 0–15 (3.0%) 16–30 (42.1%) 31–45 (28.1%) 46–60 (15.1%) 61–75 (8.5%) 76+ (3.2%) worldwide, the number of new cases since 1995 of sci ranges from 10.4 to 83 people per million per year. this wide range of numbers is probably partly due to differences among regions in whether and how injuries are reported. in north america, about 39 people per every million incur sci traumatically each year, and in western europe, the incidence is 16 per million. in the united states, the incidence of spinal cord injury has been estimated to be about 40 cases per 1 million people per year or around 12,000 cases per year. in china, the incidence is approximately 60,000 per year. the estimated number of people living with sci in the world ranges from 236 to 4187 per million. estimates vary widely due to differences in how data are collected and what techniques are used to extrapolate the figures. little information is available from asia, and even less from africa and south america. in western europe the estimated prevalence is 300 per million people and in north america it is 853 per million. it is estimated at 440 per million in iran, 526 per million in iceland, and 681 per million in australia. in the united states there are between 225,000 and 296,000 individuals living with spinal cord injuries, and different studies have estimated prevalences from 525 to 906 per million. sci is present in about 2% of all cases of blunt force trauma. anyone who has undergone force sufficient to cause a thoracic spinal injury is at high risk for other injuries also. in 44% of sci cases, other serious injuries are sustained at the same time; 14% of sci patients also have head trauma or facial trauma. other commonly associated injuries include chest trauma, abdominal trauma, pelvic fractures, and long bone fractures. males account for four out of five traumatic spinal cord injuries. most of these injuries occur in men under 30 years of age. the average age at the time of injury has slowly increased from about 29 years in the 1970s to 41. in pakistan, spinal cord injury is more common in males (92.68%) as compared to females in the 20-30 years of age group with a median age of 40 years, although people from 12-70 years of age suffered from spinal cord injury rates of injury are at their lowest in children, at their highest in the late teens to early twenties, then get progressively lower in older age groups; however rates may rise in the elderly. in sweden between 50 and 70% of all cases of sci occur in people under 30, and 25% occur in those over 50. while sci rates are highest among people age 15–20, fewer than 3% of scis occur in people under 15. neonatal sci occurs in one in 60,000 births, e.g. from breech births or injuries by forceps. the difference in rates between the sexes diminishes in injuries at age 3 and younger; the same number of girls are injured as boys, or possibly more. another cause of pediatric injury is child abuse such as shaken baby syndrome. for children, the most common cause of sci (56%) is vehicle crashes. high numbers of adolescent injuries are attributable in a large part to traffic accidents and sports injuries. for people over 65, falls are the most common cause of traumatic sci. the elderly and people with severe arthritis are at high risk for sci because of defects in the spinal column. in nontraumatic sci, the gender difference is smaller, the average age of occurrence is greater, and incomplete lesions are more common. history the ancient egyptian edwin smith papyrus is the earliest known description of sci. sci has been known to be devastating for millennia; the ancient egyptian edwin smith papyrus from 2500 bc, the first known description of the injury, says it is "not to be treated". hindu texts dating back to 1800 bc also mention sci and describe traction techniques to straighten the spine. the greek physician hippocrates, born in the fifth century bc, described sci in his hippocratic corpus and invented traction devices to straighten dislocated vertebrae. but it was not until aulus cornelius celsus, born 30 bc, noted that a cervical injury resulted in rapid death that the spinal cord itself was implicated in the condition. in the second century ad the greek physician galen experimented on monkeys and reported that a horizontal cut through the spinal cord caused them to lose all sensation and motion below the level of the cut. the seventh-century greek physician paul of aegina described surgical techniques for treatment of broken vertebrae by removing bone fragments, as well as surgery to relieve pressure on the spine. little medical progress was made during the middle ages in europe; it was not until the renaissance that the spine and nerves were accurately depicted in human anatomy drawings by leonardo da vinci and andreas vesalius. in 1762 a surgeon named andre louis removed a bullet from the lumbar spine of a patient, who regained motion in the legs. in 1829 the surgeon gilpin smith performed a successful laminectomy that improved the patient's sensation. however, the idea that sci was untreatable remained predominant until the early 20th century. in 1934, the mortality rate in the first two years after injury was over 80%, mostly due to infections of the urinary tract and pressure sores, the latter of which were believed to be intrinsic to sci rather than a result of continuous bedrest. it was not until the second half of the century that breakthroughs in imaging, surgery, medical care, and rehabilitation medicine contributed to a substantial improvement in sci care. the relative incidence of incomplete compared to complete injuries has improved since the mid-20th century, due mainly to the emphasis on faster and better initial care and stabilization of spinal cord injury patients. the creation of emergency medical services to professionally transport people to the hospital is given partial credit for an improvement in outcomes since the 1970s. improvements in care have been accompanied by increased life expectancy of people with sci; survival times have improved by about 2000% since 1940. in 2015/2016 23% of people in nine spinal injury centres in england had their discharge delayed because of disputes about who should pay for the equipment they needed. research directions main article: spinal cord injury research scientists are investigating various avenues for treatment of spinal cord injury. therapeutic research is focused on two main areas: neuroprotection and neuroregeneration. the former seeks to prevent the harm that occurs from secondary injury in the minutes to weeks following the insult, and the latter aims to reconnect the broken circuits in the spinal cord to allow function to return. neuroprotective drugs target secondary injury effects including inflammation, damage by free radicals, excitotoxicity (neuronal damage by excessive glutamate signaling), and apoptosis (cell suicide). several potentially neuroprotective agents that target pathways like these are under investigation in human clinical trials. human bone marrow derived mesenchymal stem cells seen under phase contrast microscope (63 x magnification) stem cell transplantation is an important avenue for sci research: the goal is to replace lost spinal cord cells, allow reconnection in broken neural circuits by regrowing axons, and to create an environment in the tissues that is favorable to growth. a key avenue of sci research is research on stem cells, which can differentiate into other types of cells—including those lost after sci. types of cells being researched for use in sci include embryonic stem cells, neural stem cells, mesenchymal stem cells, olfactory ensheathing cells, schwann cells, activated macrophages, and induced pluripotent stem cells. hundreds of stem cell studies have been done in humans, with promising but inconclusive results. an ongoing phase 2 trial in 2016 presented data showing that after 90 days, 2 out of 4 subjects had already improved two motor levels and had thus already achieved its endpoint of 2/5 patients improving two levels within 6–12 months. six-month data is expected in january 2017. another type of approach is tissue engineering, using biomaterials to help scaffold and rebuild damaged tissues. biomaterials being investigated include natural substances such as collagen or agarose and synthetic ones like polymers and nitrocellulose. they fall into two categories: hydrogels and nanofibers. these materials can also be used as a vehicle for delivering gene therapy to tissues. one avenue being explored to allow paralyzed people to walk and to aid in rehabilitation of those with some walking ability is the use of wearable powered robotic exoskeletons. the devices, which have motorized joints, are put on over the legs and