Minimally Invasive Plate Osteosynthesis (MIPO) Through the Posterior Approach for the Humerus: A Cadaveric Study

Background Minimally invasive plate osteosynthesis (MIPO) has been effectively used in femur and tibia fractures. MIPO in the humerus is conducted by anterior (most commonly used), lateral, and posterior approaches. However, in the anterior approach, in distal humeral diaphyseal fractures, there is a lack of adequate room for screw placement in the distal fragment for good stability. In such cases, the posterior approach for MIPO may be a propitious treatment method. However, the literature on MIPO using the posterior approach for humeral diaphyseal fractures is limited. This study aimed to evaluate the feasibility of MIPO through the posterior approach and study the association of radial nerve injury with MIPO through the posterior approach for the humerus. Methodology This experimental study was conducted in the Department of Orthopedics, Himalayan Institute of Medical Sciences, Dehradun, Uttarakhand, India, and 20 cadaveric arms (10 right and 10 left) of 11 embalmed (formalin) cadavers were included (seven males and four females). Cadavers were placed prone on the dissection table. The posterolateral tip of the acromion and lateral epicondyle of the humerus were used as bony landmarks that were marked under C-Arm (Ziehm Imaging, Orlando, FL, USA) using K wires (Kirschner wires, Surgical Holdings, Essex, UK). Two incisions on the posterior part of the arm were made, and the radial nerve was identified at the proximal incision. After creating a submuscular tunnel, a 3.5 mm extraarticular distal humeral locking compression plate (LCP) was introduced over the posterior surface of the humerus and fixed to the humerus distally with one screw and then adjusted proximally and fixed to the humerus with another screw in the proximal window, followed by placement of couple more screws under C-Arm. After plate fixation, the dissection was completed to meticulously explore the radial nerve. The radial nerve was examined thoroughly for any injury sustained after completion of dissection, from the triangular interval to the lateral intermuscular septum where the nerve enters the anterior chamber. The position of the radial nerve with respect to plate holes was noted. The distance from the posterolateral tip of the acromion to the lateral epicondyle was measured as humeral length. The medial and lateral points where radial nerve passed over the posterior surface of the humerus were measured from the posterolateral tip of the acromion and compared with the humeral length. Results In this study, the radial nerve was lying over the posterior surface of the humerus for a mean distance of 52.161 ± 5.16 mm. The mean distance at which the radial nerve crossed the medial and lateral borders of the posterior surface of the humerus, measured from the posterolateral tip of the acromion, was 118.34 ± 10.86 mm (40.07% of humeral length) and 170 ± 12.30 mm (57.57% of humeral length), respectively, and the mean humeral length in this study was 295.27 ± 17.94 mm. The radial nerve and its branches were found to be intact in all cases. The radial nerve was related to the fifth, sixth, and seventh holes, with the nerve lying most commonly over the sixth hole (3.5 mm extraarticular distal humerus locking plate). Conclusions The posterior approach of MIPO in humeral fractures is a safe and reliable treatment modality with minimal risk of radial nerve injury. The radial nerve can be safely identified at the spiral groove using the bony landmarks described in our study.