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Procedure for Testing the Stability of Distal Third Tibia Fracture Fixtures on an MTS machine

Tabitha Cacheris

BME 4965: Capstone Project

Guidance from Dr. Gary Bledsoe

Introduction

Distal Third Tibia Fracture: What is it?

Complex injury in the lower third of the tibia
High complication rate
Complications include infections, cutaneous problems, nonunion
Typical fixture types:

Interlock Nailing
Minimally invasive plate osteosynthesis with locking plates
External fixation spanning ankle joint

MTS Machine: What is it? How is it involved in project?

Material Testing System for analytic properties
Operated by a hydraulic power unit
Used to measure tension, compression, flexure, shear strength, fatigue, and fracture
Specimens are loaded into the MTS and tested to axial failure
An MTS procedure was constructed to test an intact tibia and a designed tibia fixture on a distal third fracture
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Methods and Procedure

Results

Conclusion

The designed (fractured) bone has a greater stiffness than the intact bone. This is beneficial because:

The distal portion of the tibia will take on more stress because it is closer to the ankle.
Since the bone is broken and weak, more stiffness may provide additional stability which may provide a clinical benefit , i.e., less likely to refracture, decreased healing time, etc.
When fixating a fracture with plates and screws, these will compensate for the overall weakened structure by taking on more of the stress on the tibia. This additional stiffness to the tibia will help ensure that it does not easily fracture again.

Overall, the procedure was well-designed and effective, and it helped produce accurate data.

Future Work

Future plans are to expand this procedure to 3D printed bones, to different fixtures on the distal third tibia, or to different fixtures on different broken bone sites.

References

Gawali, S. R., Kukale, S. B., Nirvane, P. V., & Toshniwal, R. O. (n.d.). Management of Fractures of Distal third Tibia by Interlock Nailing. JFAS(AP). Retrieved April 23, 2023, from https://www.jfasap.com/doi/JFASAP/pdf/10.5005/jp-journals-10040-1043
Joveniaux, P., Ohl, X., Harisboure, A., Berrichi, A., Labatut, L., Simon, P., Mainard, D., Vix, N., & Dehoux, E. (2010, April). Distal tibia fractures: Management and complications of 101 cases. International orthopaedics. Retrieved April 23, 2023, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2903136/
Materials tensile test applications. MTS. (n.d.). Retrieved April 23, 2023, from https://www.mts.com/en/applications/materials/test-type/tension

Figure 5.

Figure 2: A. Normal Intact tibia bone is loaded into the MTS machine following the procedure guidelines. The test completed is for the conditioning of instrumented samples. B. Command set up for the intact bone. Type of testing is cyclic, and the control mode is force. This yields the standard force, displacement, and stress for the intact bone.

Figure 3: A. Designed (fractured) bone with intramedullary nailing with reduction plating is loaded into the MTS machine following the procedure guidelines. The test completed is for the stiffness measurement. B. Command set up for the designed bone. Type of testing is monotonic. This yields the experimental displacement of force applied and stress for the designed bone.

Figure 4: Graph yields an average stiffness of 717 N/mm with a standard deviation of 37 N/mm of the 3 trials for the intact bone.

Figure 5: Graph yields an average stiffness of 1239 N/mm with a standard deviation of 32 N/mm of the 3 trials for the designed (fractured) bone.

Figure 4.

Three trials were completed for each bone. Figure 4 is the data from trial 1,2 and 3 of the intact bone. Figure 5 is the data from trial 1,2, and 3 of the designed (fractured) bone. The overall stiffness of the tibia is increased by nearly 75% when fixed with intramedullary nailing and reduction plating.

Figure 1.

Figure 1: Shows a distal third tibia fracture