The use of medial support screw was associated with axillary nerve injury after plate fixation of proximal humeral fracture using minimal invasive deltoid-splitting approach

Abstract

BackgroundThe purpose of this study was to evaluate the incidence and risk factors for axillary nerve injury after plate fixation of humeral fractures using minimal invasive deltoid-splitting approach. We hypothesized that the use of medial support screw (MSS) would be associated with the outcome of axillary nerve injury. MethodsThis study retrospectively evaluated consecutive 32 patients who underwent surgical treatments for proximal or midshaft humeral fractures. Of them, we included 26 patients who were examined by electromyography/nerve conduction (EMG/NCV) study at 3–4 weeks postoperatively. We excluded 6 patients because two of them were not compliant to EMG/NCV and the remaining two died due to unrelated medical illness. Outcome assessments included pain, functional scores, range of motion, and radiographic results. ResultsThere were 8 male and 18 female patients with mean age of 67 ± 15 years. Mean duration of follow-up period was 31 ± 11 months. The mean time to EMG/NCS after surgery was 3.5 ± 0.6 weeks. EMG/NCS examinations revealed incomplete axillary nerve injury in 8 patients (31%) without complete nerve injury. Active forward elevation at 3 months postoperatively was significantly lower in patients with axillary nerve injury than in those without it (99° ± 12 and 123° ± 37, respectively, p = 0.047), although final clinical outcomes were not different. At surgery, MSS was used in 17 patients (65%), and 8 of them were associated with nerve injury. The use of MSS was only correlated with the outcome of axillary nerve injury, because the axillary nerve injury developed only in MSS group (p = 0.047). The MMT grade 4 in abduction strength was more common in patients with axillary nerve injury than in those without (p = 0.037). ConclusionsAxillary nerve injury was a concern after plate fixation of proximal humeral fracture using minimal invasive deltoid-splitting approach. The use of medial support screw to improve the stability could increase a risk of axillary nerve injury when used with this approach.