Spinal mobility, muscle strength and function in patients with idiopathic scoliosis. Different aspects on long term outcome

Introduction: The long-term physical function outcome in patients treated for idiopathic scoliosis (IS) during childhood and adolescence has not been fully explored. In addition, there is a lack of studies where different methods to measure pulmonary function are validated in patients with early onset scoliosis. The aims of this thesis were to evaluate the outcome in terms of spinal mobility, trunk muscle endurance, back pain and function, thoracic mobility and its relation to pulmonary function and ribcage deformity in patients with IS in a long term perspective and also to evaluate the criterion validity of different methods for measuring pulmonary function in middle-aged patients with early onset idiopathic scoliosis (EOS) and to establish if any of those methods could be a valid, easy to perform and inexpensive tool to use in clinical practice. Patients and methods: In study I, 237 patients with adolescent idiopathic scoliosis (AIS), either brace treated (BT) (n=102) or surgically treated (ST) (n=135) attended a follow-up. Their spinal mobility and trunk muscle endurance were evaluated and questionnaires covering their general and disease specific quality of life, as well as present back function and pain were used. An ageand sex-matched control group without scoliosis (n=100) was randomly selected. In study II, 106 patients with EOS (BT n=57, ST n=49) treated during childhood and adolescence. Their thoracic mobility (range of motion of the thoracic spine, thorax expansion and breathing movements) and its relation to pulmonary function and ribcage deformity (curve size and trunk deformity) was evaluated and their results compared to reference values. In a subgroup of 33 patients respiratory muscle strength was evaluated. In study III, 116 EOS patients (BT n=63, ST n=53), were evaluated in terms of spinal mobility and trunk muscle endurance. They were compared to 40 patients with untreated AIS, and to the AIS patients from study I. In study IV, the validity of five methods measuring pulmonary function was evaluated in 33 EOS patients. Main results: Study I, lumbar spinal mobility and trunk muscle endurance were reduced in both BT and ST patients with AIS. For the ST patients a greater lumbar spinal mobility as well as better trunk muscle endurance were found to correlate with better measures of physical function. For the BT patients a reduced lumbar spine range of motion (ROM) was found to correlate with higher pain intensity, and larger extension of both lumbar and all over the body pain. Study II, thorax expansion and breathing movements were significantly reduced in both BT and ST patients with EOS. The respiratory muscle strength was significantly lower only in the ST patients when compared to reference values. The results of a multivariate analysis revealed that the strongest factors explaining total lung capacity (TLC) % of predicted were gender, brace model and smoking habits. Study III, spinal mobility and trunk muscle endurance were similar in BT patients with EOS and untreated patients with AIS. The BT patients with EOS were significantly more mobile and had longer trunk muscle endurance than the BT patients with AIS. The ST patients with EOS were neither weaker nor stiffer than the ST patients with AIS. The degree of total lumbar ROM was found to affect back function in the ST group with EOS. Study IV, there were strong correlations between the vital capacity (VC) measurements by plethysmography and the measurements by handheld spirometer, CT scan and thorax expansion for middle-aged patients with EOS. Conclusions: For braced as well as operated patients with AIS, lumbar spinal mobility and muscle endurance were reduced more than 20 years after completed treatment. The self-reported physical function was however, not severely restricted. In patients with EOS, BT as well as ST, thorax expansion and breathing movements were reduced more than 20 years after completed treatment. TLC values as a measurement of pulmonary function was influenced by gender, brace model, smoking habits, thorax expansion and curve size at start of treatment. Patients with scoliosis should therefore be strongly advised not to smoke. For braced EOS patients, at mean 26.5 years after completed treatment, both spinal range of motion and trunk muscle endurance were similar to that of untreated AIS patients. The EOS patients, despite a significantly longer bracing period, were more mobile and had longer muscle endurance than the braced AIS patients. The operated EOS patients were neither weaker nor stiffer than the operated AIS patients, despite somewhat longer fusions in the EOS group. There were strong correlations between VC measured by spirometry by plethysmography and measurements by a handheld spirometer, CT scan, and thorax expansion for middle-aged patients with EOS. Therefore, thorax expansion and handheld spirometer, both cheaper and less time-consuming, can be useful tools for early detection of reduction of pulmonary function during daily clinical practice.