Danger zones for the placement of locking screws in humeral diaphysis fracture osteosynthesis with Minimally Invasive Technique (MIPO)

Abstract

Several recent articles have described the technique of minimally invasive plate osteosynthesis (MIPO) in the treatment of humeral shaft fractures using the anterior approach. Objective: to identify the danger zone for the placement of locking screws to avoid injury to the musculocutaneous nerve in the anterior compartment and injury to the radial nerve in the posterior compartment of the humerus in relation to humeral length.

Ten cadaveric arms were fixed with locking compression plate (LCP)  with MIPO technique. Two locking screws were fixed at each end using the open technique; the remaining six screws inserted percutaneously. Both anterior and posterior were dissected to identify lesions of the musculocutaneous nerve and the radial nerve. Humeral length with a single palpable bony landmark was measured from the posterior tip of the acromion process to the lateral epicondyle. Damage or direct contact of the locking screws with the musculocutaneous or radial nerve was recorded, and the distance between the screws and the radial nerve was also measured.

The mean humeral length was 29.71 cm (99% confidence interval (CI): 28.54-30.86). The area of ​​fixation of the first to the tenth locking screw was 5.46 and 21.06 cm, respectively, measured from the lateral epicondyle. On the anterior aspect, the fixation zone causing musculocutaneous nerve injury averaged between 5.46-12.68 cm from the lateral epicondyle. The first 4 screws were the most risky and had direct contact with the musculocutaneous nerve. On the posterior face, the fixation zone that caused radial nerve injury averaged between 10.8-17.59 cm from the lateral epicondyle and most of the dangerous screws that penetrated or touched the radial nerve were in the sixth and third holes. seventh, which are at 14.03-15.8 cm. The distances between the screws and radial ribs.

The danger zone for the musculocutaneous and radial nerves could be determined. Since the area of ​​radial nerve injury shows great variation, this procedure should only be performed by experienced surgeons.