Comparison of Humeral Intramedullary Nail Internal Locking System and Standard External Locking System

Introduction: This study aimed to compare the 'Freehand Distal Locking (FHDL)" method, which is a standard in the distal locking stage of the humerus intramedullary nails, and the "Inside-to-Out Distal Locking (IODL)" Method, which was developed as a new nailing model. Methods: A total of 51 patients who underwent intramedullary nailing surgery due to humeral shaft fractures in our clinic were included in the study. Trigen Humeral nail (Smith and Nephew, Memphis, USA) with FHDL was used in 24 patients, and InSafeLock Humeral nail (TST, Istanbul, Turkey) with IODL in 27 patients. The effects of these two different nailing and locking techniques used in humeral shaft fractures in terms of surgical duration, radiation exposure duration, and functional/ radiological results were evaluated. Results: The mean follow-up period of the 51 patients (28 males and 23 females; mean age: 41.8 years) was 34.6 months (range: 9-76). According to the AO classification, 24 fractures were evaluated as type A, 17 were type B, and 10 were type C. The general evaluation of all cases revealed positive correlations between the surgical and radiation exposure durations (r=0.855; p<0.01). As the surgery duration prolonged, the ionizing radiation exposure increased. The comparison of the two groups determined a decreased surgical duration by 24.9 minute (81.6 min vs 106.5 min) and a decreased radiation exposure duration by 28.8 sec (17.7 sec vs 41.5 sec) in the IODL case group compared to the FHDL case group (p<0.05). The functional result evaluation revealed constant scorings that were satisfactory and close to each other in both groups (94.3 vs 93.3) (p>0.05). The full union was obtained in all patients except one case in the FHDL group. Symptomatic biceps tendinopathy findings were detected in four cases in the IODL group and five in the FHDL group. Local pain and sensitivity were detected in two cases in the IODL group in the form of impingement in the triceps olecranon insertion, where the distal end of the endopin is located. Conclusion: Distal locking is the most problematic stage of humerus nailing surgeries. Adjustable external guides solve the proximal locking problem; however, they are insufficient in distal locking. Therefore, the FHDL method is more preferred in distal locking, which causes problems like prolonged surgical durations and excessive ionizing radiation exposure. The surgical duration shortened and ionizing radiation exposure decreased at significant levels in the IODL humerus nailing with endopin. In addition, the lack of additional incisions for distal locking will avoid possible neurovascular injuries and incision-related wound complications.