Long-term results of surgical treatment of femoral neck fractures using dynamic derotational osteosynthesis

BACKGROUND: Femoral neck fractures are among the most common injuries of the human skeleton. If in 2004 in Russia the incidence of fractures of the proximal femur in patients over 50 years of age was 105.9 per 100,000 of the population (and in women this figure was almost twice as high as in men), it is expected that by 2025 the number of victims worldwide will have doubled, and by 2050 it will be almost 4.5 million. Existing osteosynthesis techniques do not take into account the peculiarities of the uneven distribution of bone density in the femoral head, which can lead to the placement of fixators in a deliberately weakened area, reduced strength of osteosynthesis, migration of fixators and, as a result, non-union of the fracture.

AIM: To compare the long-term results of dynamic derotation osteosynthesis with the results of femoral neck fracture osteosynthesis with cannulated screws, dynamic hip screws, and V-wires.

MATERIALS AND METHODS: The study was based on the analysis of the results of surgical treatment of 259 patients with femoral neck fractures. In the treatment of 114 (44%) patients (study group), the titanium dynamic derotational fixator Targon FN manufactured by Aesculap B. Braun (Germany) was used. The comparison group included 145 (56%) patients who underwent osteosynthesis using a dynamic femoral screw (40 patients), tensioned V-wires (60 patients) or 3 AO screws (40 patients). There were no significant differences in the distribution of patients by age in the groups considered, which was confirmed by pairwise tests using Holm's multiple comparison correction method.

RESULTS: In Garden III femoral neck fractures, 59.6% of the study group achieved consolidation compared to 34.5% with dynamic hip screw implantation, 22.7% with V-wires and 28.0% with cannulated screws. In Garden IV fractures, consolidation did not occur in any of the observations. The incidence of avascular necrosis of the femoral head is highest in Garden III fractures: 39.2% with dynamic femoral screw implantation, 30.1% with V-wires, 34.2% with cannulated screws and 21.8% with dynamic derotational osteosynthesis. When evaluating the long-term results in patients with consolidated fractures, claudication of the operated limb was observed (in Garden III type fractures in 64% of cases — when using a dynamic derotational fixator, 65% — when using a derotational femoral screw, 100% - when using cannulated screws and V-wires). The maximum femoral neck offset shortening of more than 15% was observed in 7 patients (39%) with dynamic derotational osteosynthesis, in 6 patients (67%) with dynamic femoral screw implantation, in 5 patients (60%) with cannulated screws and in 8 patients (80%) with V-wires.

CONCLUSION: Garden I fractures of the femoral neck do not lead to avascular necrosis of the femoral head. As the angle of the fracture plane increases and the blood supply to the femoral head decreases, the incidence of avascular necrosis increases. The development of claudication in the patients was caused by the reduction in femoral offset length due to osteolysis, which occurred as a result of both the localisation of the fracture plane (fracture factor) and the dynamic function of the implant (fixator factor). Lameness was therefore considered to be the 'payback' for the consolidation of the fracture.