compared to non-rodded patients—while type iv patients with rodded tibiae experienced 0.93 tibia fractures per year, patients with natural tibiae experienced only 0.81. however, in patients with type iii, rodding surgery decreased the average number of tibia fractures per year from 0.84 to 0.57.: table v spinal spinal fusion can be performed either as a preventative measure or to correct existing scoliosis, although the inherent fragility of oi bone makes this operation more complex in oi patients than it does with patients who have adolescent idiopathic scoliosis, but normal bone density. despite the risks, however, three nemours–dupont orthopedic surgeons who specialize in surgical intervention for osteogenesis imperfecta recommend operating if the curve is greater than 50° after a child is past peak height velocity, as the spine's curve can continue to worsen even into adulthood.: 104 due to the risk involved, the same surgeons recommend that surgery for basilar impressions and basilar invaginations should only be carried out if the pressure being exerted on the spinal cord and brain stem is causing actual neurological symptoms.: 106–107 once basilar invagination has become symptomatic, only surgery can halt or reverse the progression of neurological deficits.: 345 physical therapy physical therapy is generally recommended, however individualized protocols are required due to the variability of oi.: 378 physical therapy is used to strengthen muscles, improve motility, improve flexibility, and help with weight maintenance, although it must be done in a gentle manner to minimize the risk of bone fracture.: 378 in people with oi, exercise often involves water aerobics, light resistance exercises, and walking, if the patient is able.: 378 however, even in patients with mild oi, contact sports, as well as activities likely to put unnecessary stress on the joints, such as jumping, are contraindicated due to the risks they pose.: 378 individuals with more limited mobility are encouraged to change positions regularly throughout the day; people who sit in a wheelchair most or all of the day are recommended to get out of it every two hours, as a form of exercise, to decrease stiffness, and to prevent pressure ulcers.: 378 individuals with moderate to severe oi, who require assistive mobility devices and adapted vehicles, face significant barriers to access wheelchair-accessible pools or gyms—they either may not have any in their area, nor the means to get there.: 378 obesity may be more likely to present among those with severe oi, (especially after the age of 20,) and can, in some, cause further declines in mobility.: 371, 373 tilt table whole body vibration may also be done to increase the mobility of long-term immobilized (bedridden) patients with oi; in at least two cases it helped bedridden children to be able to sit upright. teeth