Static bending test after proximal femoral nail (PFN) removal – in vitro analysis

Abstract

ObjectiveTo evaluate, through biomechanical testing, the resistance to and energy required for the occurrence of proximal femoral fracture in synthetic bone after removal of a proximal femoral nail model (PFN), comparing the results obtained with a reinforcement technique using polymethylmethacrylate (PMMA).MethodsFifteen synthetic bones were used: five units for the control group (CG), five for the test group without reinforcement (TGNR), and five for the test group with reinforcement (TGR). The biomechanical analysis was performed simulating a fall on the trochanter using a servo-hydraulic machine. In the GC, the assay was performed with the PFN intact. In the TGNR and TGR groups, a model of PFN was introduced and the tests were performed in the TGNR, after simple removal of the synthesis material, and in the TGR, after removal of the same PFN model and filling of the cavity in the femoral neck with PMMA.ResultsAll groups presented a basicervical fracture. The CG presented a mean of 1427.39 Newtons (N) of maximum load and 10.14 Joules (J) of energy for the occurrence of the fracture. The TGNR and TGR presented 892.14 N and 1477.80 N of maximum load, and 6.71 J and 11.99 J of energy, respectively. According to the Kruskal–Wallis ANOVA, there was a significant difference in the maximum load (p = 0.009) and energy (p = 0.007) between these groups.ConclusionThe simple removal of a PFN in synthetic bone showed a significant reduction of the maximum load and energy for the occurrence of fracture, which were re-established with a reinforcement technique using PMMA.

Biomechanical Test Following Removal of a Dynamic Hip Screw: In Vitro Analysis

“…We compared our results to a similar work in which the authors used the same method and synthetic model but using a proximal femoral nail (PFN) instead of a DHS [9]. Paiva et al described statistically significant results comparing the groups with and without cement filling, a very intriguing result, since the PFN screw used in the study was 10.5 mm in diameter, smaller than the 12.0 mm of the DHS screw used in our research.…”

“…The proximity of the cement filling to the uppermost part of the femoral neck in the PFN group, as compared to our study with DHS, was on the fall over the trochanter. It is, therefore, possible that the closer to this region, the greater the resistance implemented by the reinforcement, leading us to believe that one of the main factors of the increased strength with PMMA in the proximal femoral extremity is not only about the volume of PMMA used but also its positioning, a fact already mentioned in other publications [9-12].…”

“…The choice of synthetic bones was to ensure comparable biomechanical properties between the groups and to eliminate variables found in cadaveric models (bone density, length, and diameter) [8]. As seen in the study by Paiva et al, we noticed that there was a large difference interval in the control group; therefore, we chose to increase the number of synthetic bones to 10 in the control group in order to improve this interval [9].…”

Ensaio biomecânico após retirada de parafusos canulados do fêmur proximal (análise in vitro)

“…In a similar work, in which the author uses the same methodology and the same synthetic model, but with HFP, the results were statistically significant 15 ; our study had a very intriguing result, because the HFP was filled in only one specific place: a 10.5-mm sliding screw tunnel, with a PMMA volume of 9 mL. We noticed that the main difference was the tension provided by the PMMA reinforcement, since two specimens from our study had diaphyseal fractures.…”

“…There is a concern about the volume used due to the local thermal reaction. 9 15 The volume used in our study is similar to that used in other works, showing little local thermal variation. 10 14…”