Incidence

The incidence of scoliosis in CP varies greatly, from 6% to almost 100%; but the generally accepted incidence in the overall CP population is 20% to 25%. The rate varies depending on the particular study, the type of CP, the severity of neurologic involvement, and ambulatory status. The incidence is highest in patients with spastic CP (about 70%) and lowest in those with athetoid type (from 6%–50%). Madigan and Wallace, in their survey of institutionalized CP patients published in 1981, found that 64% of the 272 patients studied had scoliosis greater than 10 degrees on screening radiographs and that the incidence of scoliosis was related to severity of neurologic involvement. In support of this conclusion, they pointed to the inverse relationship of ambulatory status and scoliosis (44% of independent ambulators, 54% of dependent ambulators, 61% of independent sitters, and 75% of dependent sitters or bedridden residents). Patients with subluxated or dislocated hips (an indicator of disease severity) were also found to have a 75% to 77% incidence of scoliosis. Interestingly, there was no difference between patients with unilateral or bilaterally dislocated hips, underscoring the importance of severity of involvement rather than the balance of the pelvis. Kalen and colleagues found that none of their patients with curves greater than 45 degrees were ambulators, whereas 34% of those with curves less than 45 degrees were. The incidence of scoliosis is directly related to their gross motor function classification system (GMFCS) level.