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Numerical Simulation of an Intramedullary Elastic Nail: Expansion Phase and Load-Bearing Behavior.

ABSTRACT: The Marchetti-Vicenzi's nail is an intramedullary device where six curved nails are kept straight by a closing ring in order to allow their insertion into the medullary canal of a long bone; in a following step, these nails stabilize the fracture due to the ring withdrawal and to the consequent elastic expansion of the nails. Pre-clinical testing of this sort of device is strongly advocated in order to be able to foresee their stability inside the medullary canal and to quantify their stiffening action on a broken bone. In this numerical work, an MB (Multi Body) model of the device has been developed, with the dual purpose of evaluating forces between the bone and the system components during its progressive opening and verifying the behavior of the stabilized bone when it undergoes external loading. Different solutions, for flexible body modeling (discretization with lumped parameters, "flexible body," "FE Part"), have been analyzed and compared in terms of accuracy of results and required computational resources. Contact parameters have been identified and criteria to simplify geometries and therefore to reduce simulation times have been given. Results have allowed to demonstrate how a moderate lateral force is able to dislocate the fracture and how the final position of the retention nut can be optimized. On the whole, a tool for the pre-clinical testing of elastic intramedullary nails has been given.

SUBMITTER: Pascoletti G

PROVIDER: S-EPMC6258715 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Numerical Simulation of an Intramedullary Elastic Nail: Expansion Phase and Load-Bearing Behavior.

Pascoletti Giulia G Cianetti Filippo F Putame Giovanni G Terzini Mara M Zanetti Elisabetta M EM

Frontiers in bioengineering and biotechnology 20181121

The Marchetti-Vicenzi's nail is an intramedullary device where six curved nails are kept straight by a closing ring in order to allow their insertion into the medullary canal of a long bone; in a following step, these nails stabilize the fracture due to the ring withdrawal and to the consequent elastic expansion of the nails. Pre-clinical testing of this sort of device is strongly advocated in order to be able to foresee their stability inside the medullary canal and to quantify their stiffening ...[more]

PMID: 30525034

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Project description:Elastic stable intramedullary nailing (ESIN) is the standard treatment for displaced diaphyseal femoral fractures in children. However, high complication rates (10-50%) are reported in complex fractures. This biomechanical study compares the stiffness with a 3rd nail implanted to that in the classical 2C-shaped configuration and presents the application into clinical practice.For each of the 3 configurations of ESIN-osteosynthesis with titanium nails eight composite femoral grafts (Sawbones®) with an identical spiral fracture were used: 2C configuration (2C-shaped nails, 2 × 3.5 mm), 3CM configuration (3rd nail from medial) and 3CL configuration (3rd nail from lateral). Each group underwent biomechanical testing in 4-point bending, internal/external rotation and axial compression.2C and 3CM configurations showed no significant differences in this spiroid type fracture model. 3CL had a significantly higher stiffness during anterior-posterior bending, internal rotation and 9° compression than 2C, and was stiffer in the lateral-medial direction than 3CM. The 3CL was less stable during p-a bending and external rotation than both the others. As biomechanical testing showed a higher stability for the 3CL configuration in two (a-p corresponding to recurvation and 9° compression to shortening) of three directions associated with the most important clinical problems, we added a 3rd nail in ESIN-osteosynthesis for femoral fractures. 11 boys and 6 girls (2.5-15 years) were treated with modified ESIN of whom 12 were '3CL'; due to the individual character of the fractures 4 patients were treated with '3CM' (third nail from medial) and as an exception 1 adolescent with 4 nails and one boy with plate osteosynthesis. No additional stabilizations or re-operations were necessary. All patients achieved full points in the Harris-Score at follow-up; no limb length discrepancy occurred.The 3CL configuration provided a significantly higher stiffness than 2C and 3CM configurations in this biomechanical model. These results were successfully transmitted into clinical practice. All children, treated by 3CL or 3CM according to the individual character of each fracture, needed no additional stabilization and had no Re-Do operations. As a consequence, at our hospital all children with femoral diaphyseal fractures with open physis are treated with this modified ESIN-technique.

Project description:BackgroundThis study aimed to compare the radiological results between closed nailing without bone graft (BG) and open nailing with BG for aseptic subtrochanteric nonunion and to determine when an open procedure with BG should be considered.MethodsIn this retrospective study, we investigated patients who underwent surgical intervention for subtrochanteric nonunion between January 2008 and March 2018 in two institutions. Patients with infection, large bone defect, pathologic fracture, open fracture, previous surgery using plate, and follow-up of less than 1 year were excluded. We compared the demographic details and radiological results between patients who underwent the open procedure with BG (BG group) and the closed procedure without BG (non-BG group) as a historical control, and risk factors for the failure of revision surgery were evaluated.ResultsThirty-seven patients met the criteria and were divided into the following two groups: the BG group (n=19) who underwent open nailing with BG and the non-BG group (n=18) who underwent closed reamed nailing without BG. The mean degrees of correction of varus and flexion deformity were significantly different (p=0.001, respectively), 6.2° and 2.9° in the BG group and 4.1° and 0.6° in the non-BG group, respectively. Bony union was observed in 17 cases (89.5%) in an average of 7.4 months in the BG group and in 16 cases (88.9%) in 7.6 months in the non-BG group, with no significant differences. The factors that were significantly associated with failure of revision were atypical fracture, two or more previous surgeries, and varus and sagittal anterior angulation.ConclusionsThe radiological results of closed reamed nailing without BG for subtrochanteric nonunion were satisfactory. In the effort of percutaneous realignment, gap reduction, and intramedullary reaming, the radiological results of closed nailing without BG were not different from those of open nailing with BG; therefore, closed procedure without BG may be an acceptable option in appropriately selected patients.

Dataset Information

Numerical Simulation of an Intramedullary Elastic Nail: Expansion Phase and Load-Bearing Behavior.

Publications

Numerical Simulation of an Intramedullary Elastic Nail: Expansion Phase and Load-Bearing Behavior.

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