Mechanical analysis of femoral neck fracture fixation with dynamic condylar screw in synthetic bone.

Anderson Freitas,Marcelo De Almeida Ferrer,Renato De Almeida Lima,Rafael Almeida Maciel,Diogo Ranier De Macedo Souto

doi:10.1590/1413-78522014220500922

Abstract

Objective: To analyze statistically results in biomechanical testing of fixation of femoral neck Pauwels type III fractures, on synthetic bone, with dynamic condylar screw (DCS) and control group. Methods: Ten synthetic bones of a national brand were used. Test Group: fixation was performed after osteotomy at 70o tilt using DCS plate with four holes. We analyzed the resistance of this fixation with 5 mm displacement and rotational deviation (Step 1) and with10 mm (Step 2). Control group: the models were tested in their integrity until the femoral neck fracture occurred. Results: The values of the test group in Step 1 showed a mean of 974N and SD = 114N. In Stage 2, we obtained on average 1335N and SD = 98N. The values in the control group were: 1544N, 1110N, 1359N, 1194N, 1437N, respectively. Statistical analysis using the Mann-Whitney test for comparison of the maximum force (N) between the test group and the control, in Step 2, demonstrated that there is no significant difference between the DCS and control plates (p = 0.91). Conclusion: There is no significant difference between the DCS boards and the control group exposed to full resistance. Level of Evidence III, Case Control.

Highlights

With increasing life expectancy and the growing number of high-energy trauma, fractures of the femoral neck are becoming a surgical entity increasingly frequent.[1,2] These fractures have a bimodal characteristics: young patients, victims of high energy trauma, and the elderly, which accounts to most of the injuries
Fluoroscopic control was performed in AP and profile view during each step of the procedure. (Figure 1) Following the procedure, assemblies were subjected to X-ray for reduction evaluation and proper positioning of the synthesis. (Figure 2) The remaining five bones, identified as a control group were tested with their integrity intact until the fracture of the femoral neck occurred, simulating, in this way, the resistance maximum load previous to the intact synthetic bone femoral neck
In decreasing order of stability, resisting to greatest strength, are the fixed angle locked plate, the dynamic condylar screw (DCS), dynamic hip screw (DHS) and three cannulated screws. Another biomechanical study was performed by Sirkin et al.,[17] demonstrating a better fixation of femoral neck fractures oriented vertically in cadaver bones, using a cross-bolt at the calcar and two parallel cancellous screws or DCS compared to DHS or three parallel cannulated screws.[17]

Summary

Introduction

With increasing life expectancy and the growing number of high-energy trauma, fractures of the femoral neck are becoming a surgical entity increasingly frequent.[1,2] These fractures have a bimodal characteristics: young patients, victims of high energy trauma, and the elderly, which accounts to most of the injuries. Fractures type I show angle lower than 30 degree; Type II shows the fracture line between 30 and 50 degrees; Type III have an angle larger than 50 degrees.[5,6] Given the increase in the number of high-energy trauma in young patients, femoral neck fractures Pauwels type III, the injury pattern in this population, are becoming increasingly frequent, acquiring importance in the health context of our society.[1,7]

Methods

Results

Conclusion