CURRENT CONCEPT REVIEW Natural history of adolescent idiopathic scoliosis: a tool for guidance in decision of surgery of curves above 50° Aina J. Danielsson Received: 8 May 2012 / Accepted: 8 May 2012 / Published online: 21 December 2012 Ó EPOS 2012 Abstract The purpose of this lecture was to give an overview of the natural history of adolescent idiopathic scoliosis (AIS), in order to serve as guidance in the deci- sion of performing surgery or not for the specific patient with AIS. A literature review was performed. Studies concerning long-term outcome in patients with adolescent idiopathic scoliosis that had received no treatment were used. Outcome in terms of curve size, pulmonary function, back function and quality or life/social life was compared. The literature review showed that single thoracic curves of 50°–75° progress 0.73°/year over a 40-year period. AIS do not result in increased mortality, but pulmonary symptoms may be associated with larger curves. Back pain is more frequent among patients with AIS. No study using modern quality of life questionnaires exists, but for social function, childbearing, and marriage no apparent disadvantageous effects were reported compared to the healthy population. The conclusion is that most individuals with AIS and moderate curve size around maturity function well and lead an acceptable life in terms of work and family. Some patients with larger curves have pulmonary problems, but not to the extent that this affects the life span. This needs to be taken into account when discussing surgery with the individual patient. Keywords Adolescent idiopathic scoliosis Á Natural history Á Untreated Introduction Most surgeons indicate surgery for curves above 50° in patients with adolescent idiopathic scoliosis (AIS). How- ever, a curve size of 50–80° can be considered more of a grey zone for the decision on performing surgery. The indications used are sometimes hazy and are not always clearly expressed, and concerns include future pulmonary problems and impairment of back function, as well as cosmetic concerns. The reason for treatment of the individual patient needs to be clarified in each individual patient. The patient also needs correct information in order to be able to make a well-supported decision. A number of reasons for surgery are regularly men- tioned. The deformity itself might progress and cause an increased cosmetic problem for some patients. The major threat, though, is how the pulmonary function is affected over time. Pulmonary function is considered to be at its peak around the age of 20 years or just after, and a slow deterioration begins thereafter as part of the aging process. The gradual decline of pulmonary function from this age might give an extra burden to those who already in ado- lescence or at maturity have a reduced pulmonary function. An increase of the curve size further adds to the reduction of the pulmonary function. The impact on the patient’s general function, i.e., in the social life as well as in the working life and quality of life, is of great importance to many patients. More specific activities of the patient, i.e., those related to use of the back and affected by back pain, also affect the patient’s general well-being. Therefore, the base for decision-making is complex and multifaceted. The knowledge on what happens to the patient without treatment, i.e., natural history, is needed to support the decision whether to operate or not. The aim of any A. J. Danielsson (&) Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy at the University of Gothenburg, SE-413 45 Gothenburg, Sweden e-mail: danielsson.aina@telia.com 123 J Child Orthop (2013) 7:37–41 DOI 10.1007/s11832-012-0462-7