We supposed difference of rotation alignment of postoperative humeral shaft fracutres between open reduction and internal fixation (ORIF) and intramedullay nailing (IMN) could be identified and the difference might influence the involved shoulder. This study evaluated and compared the extent of malrotation and shoulder function after humeral shaft fractures treated operatively with IMN or ORIF.

Fifty humeral shaft fractures were randomly allocated into 2 groups. Group I underwent antegrade IMN and group II underwent ORIF. Malrotation was measured postoperatively by computed tomography scan (CT). Fracture union and functional outcomes were recorded at 12 months.

The final analysis comprised 45 patients. Group I had lower functional scores than group II (P < .05). Internal malrotation of 20° or more (humeral head internally rotated) was found in 27.2% of group I patients, but there was no malrotation in group II. The internal and external range of motion of the involved shoulder was significantly correlated with the degree of malrotation (P < .01).

This study comprehensively evaluated the degree of malrotation using CT scanning for every patient. These data bring to light some unexpected results about poor shoulder function and degeneration after humeral shaft fracture. The study can provide baseline data for larger series and longer follow-up periods.

Patients who underwent IMN had lower functional scores and a decreased range of motion postoperatively and also had a greater degree of malrotation than the ORIF group, which had none. The degree of malrotation correlated with a decreased range of motion and may possibly be a reason for degenerative arthritis at long-term follow-up.