Changes in lung function and exercise capacity in young people after posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS)

<bold>Background:</bold> We have previously reported that patients with greater spinal curvature have high levels of baseline fitness. This is postulated to be due to an auto-training effect of their spinal deformity. <bold>Hypothesis:</bold> We hypothesised that following spinal surgery, fitness may be impacted in one of two ways: a) Improved respiratory mechanics lead to better ‘trainability’ and improve exercise capacity b) Exercise capacity may fall after surgery due to reduced participation in activities <bold>Methods:</bold> Young people that underwent PSF for AIS were evaluated with detailed lung function and cardiopulmonary exercise testing. Statistical analyses (paired t-test) were undertaken to measure change before and after PSF. <bold>Results:</bold> 54 young people (16 male/38 female) were studied at mean (sd) age 14.7 (1.8) years pre-surgery, and with post-operative tests at a mean (range) of 3.2 (1.9 - 6.0) years later. <bold>TABLE 1</bold> Changes in lung function and exercise parameters after PSF for AIS <table-wrap><object-id>erj;64/suppl_68/PA1595/TB1</object-id><object-id>T1</object-id><object-id>TB1</object-id><table><colgroup><col></col><col></col><col></col><col></col></colgroup><tbody><tr><td></td><td><bold>Pre-Op</bold></td><td><bold>Post-Op</bold></td><td><bold>p-value</bold></td></tr><tr><td><bold>Degree of Curve</bold></td><td>62 (12)</td><td>19 (7)</td><td><0.001</td></tr><tr><td><bold>FEV₁ z score</bold></td><td>-2 (0.95)</td><td>-1.79 (0.96)</td><td>0.005</td></tr><tr><td><bold>RV/TLC Ratio z score</bold></td><td>0.61 (0.52)</td><td>0.27 (0.84)</td><td><0.001</td></tr><tr><td><bold>VO_2peak (ml.kg-1.min-1)</bold></td><td>37 (7)</td><td>32 (6)</td><td><0.001</td></tr><tr><td><bold>VO₂ at Anaerobic Threshold (AT) (%predicted VO_2max)</bold></td><td>51 (9)</td><td>45 (9)</td><td><0.001</td></tr><tr><td><bold>Breathing Reserve (%MVV)</bold></td><td>36 (16)</td><td>43 (12)</td><td>0.006</td></tr></tbody></table></table-wrap> <bold>Discussion:</bold> Despite improved ventilatory mechanics, young people demonstrated reduced exercise capacity after PSF. The earlier onset AT suggests this is likely due to physical deconditioning. Consideration should be given to measuring exercise capacity before spinal surgery and providing structured exercise programmes to facilitate optimal return to fitness for this patient group.