ObjectiveTo compare the effectiveness of anterior and lateral approaches of minimally invasive plate osteosynthesis (MIPO) in the treatment of humeral shaft fractures. MethodsThe clinical data were retrospectively analyzed and compared from 35 cases of humeral shaft fractures between January 2010 and December 2012. The patients underwent MIPO by anterior approach in 17 patients (group A) and by lateral approach in 18 patients (group B). There was no significant difference in gender, age, injury causes, type of fractures, and time from injury to operation between 2 groups (P>0.05). The operation time, fracture healing time, intra- or postoperative complications, and shoulder and elbow range of motion (ROM) values were recorded and analyzed. The functions of the affected shoulder and elbow were assessed with the University of California Los Angeles (UCLA) and Mayo elbow performance score system respectively. ResultsThe operation time was (91.35±8.00) minutes and (95.56±7.92) minutes in groups A and B respectively, showing no significant difference (t=-1.561, P=0.128). Incision healed by first intention in all patients of 2 groups. No iatrogenic radial nerve palsy occurred in group A, 2 cases had postoperative iatrogenic radial nerve palsy in group B, showing no significant difference (P=0.486). The patients were followed up 15.4 months on average (range, 11-24 months) in group A and 16.8 months on average (range, 10-23 months) in group B. The X-ray films showed bony healing in all patients. The fracture union time was (13.5±2.1) weeks in group A and (14.0±2.2) weeks in group B, showing no significant difference (t=-0.696, P=0.491). The UCLA scores were 33.4±1.9 in group A and 30.6±2.0 in group B, and the Mayo elbow performance scores were 100 in group A and 96.4±2.8 in group B; all showed significant differences (t=4.231, P=0.000; t=5.293, P=0.000). ConclusionGood clinical outcomes could be obtained when humeral shaft fractures are treated with MIPO either by anterior approach or by lateral apporach. However, anterior approach could offer better shoulder and elbow functional results.