Posterior Minimally Invasive Plate Osteosynthesis of Humeral Shaft Fractures: An Anatomic Study of “Danger Zones”

The most utilized approach for minimally invasive plate osteosynthesis (MIPO) of humeral fractures has been an anterior percutaneous approach. Other approaches include posterior, which places the radial nerve at risk. We performed a cadaveric study to evaluate safe intervals for screw placement using a posterior approach. MIPO fixation of the humeral shaft was performed on 11 fresh frozen cadaveric specimens following a standard protocol using a 10-hole 4.5 locking compression plate (LCP) plate and cortical screws. After fixation, anatomic dissection of the radial nerve was performed and location of the nerve delineated with regards to radiographic landmarks and the fixation construct. A 10-hole LCP plate centered on the humerus will position a screw in the third hole from top of plate only 3.08 cm (±SD 1.05 cm) from the radial nerve. The distal screws in the LCP plate construct do not the place the radial nerve at risk. The literature reports rates of iatrogenic radial nerve injury during formal open reduction and internal fixation approaching 20%, and during MIPO between 0% and 5%. With a posterior MIPO approach the radial nerve is most at risk with screw placement in the fifth and sixth holes from the top of a 10-hole plate.