Analysis on the mechanical resistance of fixation of femoral neck fractures in synthetic bone, using the dynamic hip system and an anti-rotation screw

Abstract

ObjectiveTo statistically analyze the results obtained from biomechanical tests on fixation of femoral neck fractures of Pauwels III type, in synthetic bone, using the dynamic hip system with an anti-rotation screw, versus a control group.MethodsTen synthetic bones from a Brazilian manufacturer (model C1010) were used and divided into two groups: test and control. In the test group, fixation of an osteotomy was performed with 70° of inclination at the level of the femoral neck, using DHS with an anti-rotation screw. The resistance of this fixation was evaluated, along with its rotational deviation at 5 mm of displacement (phase 1) and at 10 mm of displacement (phase 2), which was considered to be failure of synthesis. In the control group, the models were tested in their entirety until femoral neck fracturing occurred.ResultsThe test values in the test group (samples 1–5) in phase 1 were: 1512 N, 1439 N, 1205 N, 1251 N and 1273 N, respectively (mean = 1336 N; standard deviation [SD] = 132 N). The rotational deviations were: 4.90°, 3.27°, 2.62°, 0.66° and 0.66°, respectively (mean = 2.42°; SD = 1.81°). In phase 2, we obtained: 2064 N, 1895 N, 1682 N, 1713 N and 1354 N, respectively (mean = 1742 N; SD = 265 N). The failure loading values in the control group were: 1544 N, 1110 N, 1359 N, 1194 N and 1437 N, respectively (mean = 1329 N; SD = 177 N). The statistical analysis using the Mann–Whitney test showed that the test group presented maximum loading at a displacement of 10 mm, i.e. significantly greater than the failure loading of the control group (p = 0.047).ConclusionThe mechanical resistance of the test group was significantly greater than that of the control group.

Biomechanical Analysis of Femoral Neck Fracture Fixation in Synthetic Bone

“…Femoral neck fractures are frequently seen in clinical practice, representing 40-50% of proximal femur fractures. 1 , 2 The average age of patients with these fractures is 75-80 years for women, and slightly lower in men. They commonly occur in patients with multiple comorbidities, and represent high costs for treatment and management.…”

“…As the fracture becomes more oblique instability also increases, and complications related to fixation and consolidation worsen. 1 , 5 - 7…”

“…However, unstable fractures are generally treated with total or partial arthroplasty of the hip. 1 , 2 , 4 - 6 . 8 …”

“…In most patients with fractures that are not diverted from the femoral neck, internal fixation is the treatment of choice. 1 These surgeries that preserve the femoral head cause less damage to the delicate vascularization of this structure. Consequently, a frequent doubt is whether the use of two cannulated screws instead of three is sufficient to provide stability and consolidate the fracture.…”

“…Pseudoarthrosis is more common and occurs in 6% of cases on average, accounting for 60% of the complications in this type of fracture. 1 , 5 , 7 , 11 …”