Background: Recent randomized controlled trials (RCTs) support using physiotherapeutic scoliosis-specific exercises (PSSE) for adolescents with idiopathic scoliosis (AIS). All RCTs reported statistically significant results favouring PSSE but none reported on clinical significance. The number needed to treat (NNT) helps determine if RCT results are clinically meaningful. The NNT is the number of patients that need to be treated to prevent one bad outcome in a given period. A low NNT suggests that a therapy has positive outcomes in most patients offered the therapy. The objective was to determine how many patients require Schroth PSSE added to standard care (observation or brace treatment) to prevent one progression (NNT) of the Largest Curve (LC) or Sum of Curves (SOC) beyond 5° and 10°, respectively over a 6-month interval.
Methods: This was a secondary analysis of a RCT. Fifty consecutive participants from a scoliosis clinic were randomized to the Schroth PSSE + standard of care group (n = 25) or the standard of care group (n = 25).We included males and females with AIS, age 10-18 years, all curve types, with curves 10°- 45°, with or without brace, and all maturity levels. We excluded patients awaiting surgery, having had surgery, having completed brace treatment and with other scoliosis diagnoses. The local ethics review board approved the study (Pro00011552).The Schroth intervention consisted of weekly 1-h supervised Schroth PSSE sessions and a daily home program delivered over six months in addition to the standard of care. A prescription algorithm was used to determine which exercises patients were to perform. Controls received only standard of care.Cobb angles were measured using a semi-automatic system from posterior-anterior standing radiographs at baseline and 6 months.We calculated absolute risk reduction (ARR) and relative risk reduction (RRR). The NTT was calculated as: NNT = 1/ARR. Patients with missing values (PSSE group; n = 2 and controls; n = 4) were assumed to have had curve progression (worst case scenario). The RRR is calculated as RRR = ARR/CER.
Results: For LC, NNT = 3.6 (95% CI 2.0-28.2), and for SOC, NNT = 3.1 (95% CI 1.9-14.2). The corresponding ARR was 28% for LC and 32% for the SOC. The RRR was 70% for LC and 73% for the SOC. Patients with complete follow-up attended 85% of prescribed visits and completed 82.5% of the home program. Assuming zero compliance after dropout, 76% of visits were attended and 73% of the prescribed home exercises were completed.
Conclusions: The short term of Schroth PSSE intervention added to standard care provided a large benefit as compared to standard care alone. Four (LC and SOC) patients require treatment for the additional benefit of a 6-month long Schroth intervention to be observed beyond the standard of care in at least one patient.
Trial registration: NCT01610908 April 2, 2012.
Keywords: Adolescents; Clinical significance; Cobb angle; Exercise; Number needed to treat; Physiotherapeutic scoliosis specific exercises; Radiography; Schroth; Scoliosis; Spinal curvatures.