Long-term stability of angle-stable versus conventional locked intramedullary nails in distal tibia fractures

Abstract

BackgroundIn the last years intramedullary nailing has become the treatment of choice for most displaced diaphyseal tibia fractures. In contrast intramedullary nailing of distal tibia fractures is accompanied by problems like decreased biomechanical stability. Nevertheless the indications for intramedullary nailing have been extended to include even more distal fractures. The purpose of this study was to compare long-term mechanical characteristics of angle-stable versus conventional locked intramedullary nails in the treatment of unstable distal tibia fractures. Therefore, the effect of time on the mechanical properties of biodegradable sleeves was assessed.Methods8 pairs of fresh, frozen porcine tibiae were used. The expert tibial nail (Synthes) was equipped with either three conventional locking screws (CL) or the angle-stable locking system (AS), consisting of a special ASLS screw and a biodegradable sleeve. Biomechanical testing included torsional and axial loading at different time-points over 12 weeks.ResultsThe AS group showed a significantly higher torsional stiffness at all time-points (at least 60%) compared to the CL group (p < 0.001). The neutral zone was at least 5 times higher in the CL group (p < 0.001). The mean axial stiffness was maximum 10% higher (week 6) in the angle-stable locked group compared to the conventional group. There was no significant change of the torsional mechanical characteristics over the 12 weeks in both groups (p > 0.05). For axial stiffness and range of motion significant differences were found in the AS group.ConclusionsThe angle-stable locking system (ASLS) with the biodegradable sleeve provides significantly higher long-term stability. Especially the differences determined under torsional loading in this study may have clinical relevance. The ASLS permits the potential to decrease complications like secondary loss of reduction and mal-/non-union.

Disadvantages of interfragmentary shear on fracture healing—mechanical insights through numerical simulation

“…Torsional rotation occurs under intramedullary nailing, because of torsional instability of the nail itself, and of flexibility and play of the locking screws. This instability can be reduced by using angle‐stable locking screws . Studies suggest angle‐stable interlocking to improve healing compared to conventional locking, which is in agreement with our findings regarding the negative influence of torsional loading.…”

A new angle stable nailing concept for the treatment of distal tibia fractures

“…Biomechanical studies have demonstrated the advantages for the angular-stable locked nails with regard to a significantly higher axial and torsional stiffness, significantly less fracture gap movement and a significant reduction of the neutral zone in bending [6][7][8][9]. Biomechanically, two ASLS locking screws provide equal stability to three standard locking screws [10].…”

Intramedullary nailing of humeral shaft fractures: failure analysis of a single centre series

“…Newer implants have multiple, multidirectional points of fixation both proximally and distally to provide angular stability [15]. Here the introduction of the ASLS screws improved the stability of different nail constructs as confirmed by biomechanical studies [35,36]. The improvement in interlocking options has expanded nail indications for more proximal and distal shaft fractures.…”