Pulmonary function improvement in patients with ankylosing spondylitis kyphosis after pedicle subtraction osteotomy

A prospective clinical study.

To observe postoperative change in pulmonary function in patients with ankylosing spondylitis (AS) kyphosis after pedicle subtraction osteotomy (PSO).

The preoperative pulmonary dysfunction in patients with AS has been reported in several literatures, whereas few research about postoperative changes in pulmonary function with AS kyphosis was published.

A total of 32 (27 males and 5 females) patients with AS were eligibly involved. Twenty-nine (25 males and 4 females) patients completed the follow-up and 3 (2 males and 1 females) patients were lost. Pulmonary function tests, breath-holding time (BHT), and full-length spine radiographs in natural standing position were followed postoperatively.

The global kyphosis significantly decreased from 63.0°± 20.3° preoperatively to 15.3°± 10.3° postoperatively and 17.1°± 10.9° at the 2-year follow-up. The BHT before surgery was 32.5 ± 10.1 s, whereas the postoperative BHT had increased to 43.1 ± 8.6 s (P < 0.05). Two patients with AS underwent normal pulmonary function test before operation, whereas there were 19 patients at 2-year follow-up. The clinical improvement rate was 85.2% (23/27). The percent-predicted vital capacity had increased from 68.4% ± 9.5% to 79.4% ± 6.1% at 2-year follow-up (P < 0.05). The percent-predicted forced vital capacity before PSO was 75.5% ± 6.4% and it was 81.0% ± 6.9% at 2-year follow-up (P < 0.05). The improved percent-predicted vital capacity and predicted forced vital capacity had a positive correlation with the correction of global kyphosis (r = 0.6328 and 0.8612, respectively).

The postoperative pulmonary function including pulmonary volume and ventilatory function in patients with AS with kyphosis had significantly improved at 2-year follow-up. And, the improved pulmonary function had a positive correlation with the kyphosis correction.

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