n Feature Article abstract Distal Locking Screws for Intramedullary Nailing of Tibial Fractures FILON AGATHANGELIDIS, MD; GEORGIOS PETSATODIS, MD, PHD; JOHN KIRKOS, MD, PHD; PERICLES PAPADOPOULOS, MD, PHD; DIMITRIOS KARATAGLIS, MD, PHD; ANASTASIOS CHRISTODOULOU, MD, PHD I ntramedullary (IM) nailing continues to be the gold standard of treatment for long bone fractures. For the tibia in particular, excellent healing rates have been reported with minimal procedure- related complications. 1 Lately, IM nailing has been used for the stabilization of more proximal and more distal fracture patterns. 1 However, the ability to maintain a stable reduction is compromised by the expan- sion of the tibial canal diameter distally, predisposing the fixation to an increased risk of malalignment and failure. Hahn et al 2 described 5 cases of fractures within 7 cm from the ankle joint treated with a nail and 1 distal locking screw. However, at a mean of 7 months postoperatively, all nails failed. A solution to this problem was the use of a shortened nail, which al- lowed 2 distal screws and thus a stronger fixation. This concept was then tested by both clinical and biomechanical studies, 3-5 and the positive results obtained led to the introduction of newly designed nails with multiple locking options both distally and proximally, such as the Expert tibial nail (Synthes, Oberdorf, Switzerland), which allows for 4 distal locking screws. Despite this evolution in nail design, currently there are no evidence-based guidelines regarding the optimal number and configuration of distal screws that should be used. Recently introduced tibial intramedullary nails allow a number of distal screws to be used to reduce the incidence of malalignment and loss of fixation of distal metaphyseal fractures. However, the number of screws and the type of screw configuration to be used remains obscure. This biomechanical study was performed to address this question. Thirty-six Expert tibial nails (Synthes, Ober- dorf, Switzerland) were introduced in composite bone models. The models were divided into 4 groups with different distal locking configurations ranging from 2 to 4 screws. A 7-mm gap osteotomy was performed 72 mm from the tibial plafond to simulate a 42-C3 unstable distal tibial fracture. Each group was divided in 3 subgroups and underwent nondestructive biomechanical test- ing in axial compression, coronal bending, and axial torsion. The passive con- struct stiffness was measured and statistically analyzed with one-way analysis of variance. Although some differences were noted between the stiffness of each group, these were not statistically significant in compression (P=.105), bending (P=.801), external rotation (P=.246), and internal rotation (P=.370). This in vitro study showed that, when using the Expert tibial nail for unstable distal tibial fractures, the classic configuration of 2 parallel distal screws could provide the necessary stability under partial weight-bearing conditions. [Or- thopedics. 2016; 39(2):e253-e258.] The authors are from the 1st Department of Or- thopaedics (FA, GP, PP, AC), Aristotle University of Thessaloniki, G. Papanikolaou General Hospi- tal, and the 3rd Department of Orthopaedics (JK), Aristotle University of Thessaloniki, Papageorgiou General Hospital, Thessaloniki; and Euromedica Blue Cross Clinic (DK), Thessaloniki, Greece. The authors have no relevant financial relation- ships to disclose. The authors thank Dr Evangelos Magnissalis of BioHexagon Ltd for his expert input during the biomechanical testing and Nikolaos Theodorou, orthopaedic implant technician, for his help and enthusiasm. Correspondence should be addressed to: Filon Agathangelidis, MD, 39a Str Sarafi St, Ka- lamaria 55132, Greece (fagath@gmail.com). Received: March 18, 2015; Accepted: July 6, 2015. doi: 10.3928/01477447-20160129-02 MARCH/APRIL 2016 |฀Volume฀39฀•฀Number฀2 e253