BackgroundThe minimally invasive plate osteosynthesis (MIPO) technique using periarticular locking plates may be a good option for the repair of displaced proximal humeral fractures. However, axillary nerve complications related to this technique may be underestimated. The purpose of this study is to evaluate the outcomes of the minimally invasive plating, focusing on the complications.MethodsThe records of 21 consecutive patients treated for proximal humerus fractures using the MIPO technique with locking plates were retrospectively reviewed. These patients were treated between March 2009 and March 2011 with a minimum one-year follow-up. The clinical function, complications, and radiological bony union were evaluated.ResultsAll of the patients, with one exception, showed at least 90 degrees of flexion and abduction at the shoulder joint six months postoperatively. The average Constant scores at three months, six months, and one year follow-ups were 74.0 (range, 62 to 90), 79.4 (range, 64 to 91), and 82.7 (range, 66 to 92), respectively. All of the patients achieved bony union within the average of 3.2 months (range, 2 to 6 months). There was one case of delayed union, one case of intra-articular screw penetration, and one case of axillary nerve paresis (incomplete injury), which did not completely recover during the one year of follow-up.ConclusionsThe MIPO technique using periarticular locking plates is a useful option for the treatment of selected cases of displaced proximal humeral fractures. However, nerve complications such as axillary nerve paresis should be considered along with implant-related complications when choosing patients for minimally invasive plating.