Connections between radial and ulnar nerve at high humeral level in cadavers: incidence, topography, and literature review

The risk of iatrogenic radial nerve and/or profunda brachii artery injury in anterolateral humeral plating using a 4.5 mm narrow DCP: A cadaveric study

INTRODUCTION

Fixation of humeral shaft fractures with a plate and screws can endanger the neurovascular structure if proper care is not taken. No studies to our knowledge have studied the risk of iatrogenic radial nerve and/or profunda brachii artery (RNPBA) injury from each screw hole of a 4.5 mm narrow dynamic compression plate (narrow DCP). The purpose of this study is to evaluate the risk of RNPBA injury in anterolateral humeral plating with a 4.5 mm narrow DCP.

MATERIAL AND METHODS

18 humeri of 9 fresh-frozen cadavers in the supine position were exposed via the anterolateral approach with 45 degrees of arm abduction. A hypothetical fracture line was marked at the midpoint of each humerus. A precontoured ten-hole 4.5mm narrow DCP was applied to the anterolateral surface of the humerus using the fracture line to position the center of the plate. All screw holes were drilled and screws inserted. The cadaver was then turned over to the prone position with 45 degrees of arm abduction, and the RNPBA exposed. The holes through in which 100% of the screw had contact with or penetrated the RNPBA were identified as dangerous screw holes, while lesser percentages of contact were defined as risky.

RESULTS

The relative distance ratios of the entire humeral length from the lateral epicondyle of the humerus to the 4th, 3rd, 2nd and 1st proximal holes were 0.64, 0.60, 0.56 and 0.52, respectively. The most dangerous screw hole was the 2nd proximal, in which all 18 screws had contacted or penetrated the nerve, followed by the risky 1st (12/18), 3rd (8/18) and 4th (2/18) holes.

CONCLUSION

In humeral shaft plating with the 4.5mm narrow DCP using the anterolateral approach, the 2nd proximal screw hole carries the highest risk of iatrogenic radial nerve and/or profunda brachii artery injury.

Application of custom anatomy-based nerve conduits on rabbit sciatic nerve defects: in vitro and in vivo evaluations

The intermingling of regenerated nerve fibers inside nerve grafts is the main reason for mismatched nerve fibers. This is one of the key factors affecting limb function recovery after nerve injury. Previous research has shown that the accuracy of axon regeneration can be improved by a bionic structural implant. To this aim, iodine and freeze-drying high-resolution micro-computed tomography was performed to visualize the 3D topography of the New Zealand rabbit sciatic nerve (25 mm). A series of 1-, 2-, 3-, and 4-custom anatomy-based nerve conduits (CANCs) were fabricated based on the anatomical structure of the nerve fascicle. The match index, luminal surface, and mechanical properties of CANCs were evaluated before implanting in a 10-mm gap of the sciatic nerve. Recovery was evaluated by histomorphometric analyses, electrophysiological study, gastrocnemius muscle weight recovery ratio, and behavioral assessments at 12 and 24 weeks postoperatively. The accuracy of nerve regeneration was determined by changes in fluorescence-labeled profile number during simultaneous retrograde tracing. Our results showed that the optimal preprocessing condition for high-resolution micro-computed tomography visualization was treatment of the sciatic nerve with 40% Lugol's solution for 3 days followed by lyophilization for 2 days. In vitro experiments demonstrated that the match index was highest in the 3-CANC group, followed by the 2-, 1-, and 4-CANC groups. The luminal surface was lowest in the 1-CANC group. Mechanical properties (transverse compressive and bending properties) were higher in the 3- and 4-CANC groups than in the 1-CANC group. In vivo experiments demonstrated that the recovery (morphology of regenerated fibers, compound muscle action potential, gastrocnemius muscle weight recovery ratio, pain-related autotomy behaviors, and range of motion) in the 3-CANC group was superior to the other CANC groups, and achieved the same therapeutic effect as the autograft. The simultaneous retrograde tracing results showed that the percentages of double-labeled profiles of the 2-, 3-, and 4-CANC groups were comparatively lower than that of the 1-CANC group, which indicates that regenerated nerve fascicles were less intermingled in the 2-, 3-, and 4-CANC groups. These findings demonstrate that the visualization of the rabbit sciatic nerve can be achieved by iodine and freeze-drying high-resolution micro-computed tomography, and that this method can be used to design CANCs with different channels that are based on the anatomical structure of the nerve. Compared with the 1-CANC, 3-CANC had a higher match index and luminal surface, and improved the accuracy of nerve regeneration by limiting the intermingling of the regenerated fascicles. All procedures were approved by the Animal Care and Use Committee, Xinjiang Medical University, China on April 4, 2017 (ethics approval No. IACUC20170315-02).