Purpose <p>Surgical stabilization of rib fractures is an internationally established method for treating traumatic chest wall injuries. Few studies have compared the various surgical methods used. The aim of this study was to examine how different surgical methods affect long-term outcomes.</p> Method <p>This is a study of prospectively included patients with flail chest undergoing muscle-sparing chest wall surgery (<i>n</i> = 40) who were compared to historical controls who underwent conventional surgery with non-muscle-sparing incisions and thoracotomy (<i>n</i> = 38). The cohorts differed regarding injury severity, smoking habits and number of ribs operated. This was adjusted for using multiple linear regression. The primary endpoint was lung function, secondary endpoints were respiratory muscle strength, respiratory movement, physical function, physical activity, and quality of life (QoL) after six and 12&#xa0;months.</p> Results <p>Seventy-eight patients (67.9% men and 32.1% women) with a mean age of 63.6 ± 14.0&#xa0;years were included. The predicted forced vital capacity (FVC) was 92.3 ± 14.3% vs. 85.0 ± 15.3% after 12&#xa0;months (<i>p</i> = 0.037) in the muscle-sparing and conventional surgery cohorts, respectively. Shoulder movement (Boström Index 59 vs. 56, <i>p</i> = 0.007) and lateral flexion (16.1 vs. 11.4&#xa0;cm, <i>p</i> = 0.004) were significantly better in the muscle-sparing surgery patients than the conventional surgery patients after one year. No significant differences were found in respiratory muscle strength, respiratory movement, physical activity, or QoL.</p> Conclusion <p>Patients who undergo muscle-sparing surgery for chest wall injury have better long-term lung function, shoulder movement, and thoracic movement than patients who undergo conventional surgery. No difference was found between the groups concerning self-reported outcome.</p> <p>Registered in <a href="http://www.clinicaltrials.gov">www.clinicaltrials.gov</a> at 2020–12-18 with the ID NCT04710602.</p>