Time until union in absolute vs. relative stability MIPO plating in simple humeral shaft fractures.

Purpose: The objective of this study is to evaluate the effect of absolute stability (AS) versus relative stability (RS) performed through a minimally invasive plate osteosynthesis (MIPO) in AO/OTA 12A1 and 12A2 fractures on healing and the time to radiographic union.

Methods: This was a retrospective cohort study of all patients treated with plate fixation for AO/OTA type 12A1-A2 fractures at a single institution. Patients were grouped according to the type of stability used in their surgery. Time until radiographic union was estimated using the Kaplan-Meier method, which was compared by long-rank test between both types of surgical techniques.

Results: A total of 70 patients were included in this study with 35 patients in each group. The median follow-up was 9 (IQR 6-14) months. The median time to radiographic union was significantly lower in the AS group than in the RS group: 12 (interquartile range (IQR) 10-14) weeks versus 18 (IQR 16-19) weeks, respectively (p < 0.001). Non-union was seen in two cases (7%) in the relative stability group. Three patients in the RS group developed a post-operative radial nerve palsy.

Conclusion: The main finding of this study is that the median time to radiographic union was significantly shorter in the patients treated with AS compared to those with a RS technique. These findings support the recommendations of the AO foundation in that simple metaphyseal fractures (type A) that require surgical treatment should be treated with an AS construct. RS techniques should be reserved to multifragmentary fractures where fragment preservation of blood supply is paramount.