Amanda Bass and Nathan Dunkelberger
FIGURE 1. The Joint Motion Simulator
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Introduction
Many animals suffer injury and death for the sake of experimental research studies. According to the United States Department of Agriculture’s Animal and Plant Health Inspection Service, approximately 770,000 animals—including 61,000 dogs—were subjects of animal testing by research facilities in the 2015 fiscal year.1 At the Texas A&M Veterinary Medical Teaching Hospital alone, 1,200 studies were performed on dogs to develop orthopedic therapeutic interventions in 2014.2 Because those interventions are not fully developed, many dogs may be injured or, in extreme cases, die. Whereas testing orthopedic surgery techniques on dogs allows us to understand how procedures work on live animals, testing the same technique through our simulator allows us to safely and painlessly understand the procedure without unnecessary pain and death. Reducing the death and injury inflicted on animals is a widely accepted mission that the Department of Agriculture advanced into law through the Animal Welfare Act of 1966. That act outlines the guidance principle called the three Rs of animal ethics, which encourages researchers to develop alternative testing methods, improve animal welfare, and refine scientific practices when animal research is necessary. The three Rs are replacement, reduction, and refinement. The Biomechanical Environments Laboratory at Texas A&M University has developed a device, the Joint Motion Simulator (JMS) (Figure 1), to advance that mission of animal preservation by providing an alternative analysis method for the orthopedic canine joint model. Using the JMS as a research tool will decrease pain and deaths of canine test subjects by replacing them with a simulation, reducing the number needed in studies, and refining the surgical procedures applied to dogs across the nation. |
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Materials and Methods
The JMS controls the motion of a canine hip joint through two motor-driven rotations. One motor controls that joint’s forward and backward motion, and the other controls the inward and outward motion. Through a program developed in LabVIEW, the motion pattern for each motor can be selected as well as several other input options that control how the simulator behaves. That versatility allows the simulator to closely mimic the motion of a canine hip joint. The device’s adaptability and its ability to replicate canine joint motion makes the JMS a valuable tool to promote all three Rs of animal welfare. |
USING THE JMS AS A RESEARCH TOOL WILL DECREASE PAIN AND DEATHS OF CANINE TEST SUBJECTS... |
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Replacement
Replacement is a method to remove the need for dogs in orthopedic testing. When a dog needs a surgical procedure, one approach would be to assign the theorized best method without knowing the comparative advantages or disadvantages of other options. That process can cause the patient pain or injury while imposing additional logistical and monetary hindrances for the surgeon if the best option was not chosen. Our simulator allows surgeons to compare viable treatment options for different scenarios and helps them make the best choice of treatment without experimenting on live animals. The simulator will streamline orthopedic patient care, giving researchers access to a faster, higher-quality, and less-invasive alternative. |
Reduction
Reduction attempts to use fewer canine subjects in studies. One proposed use of the simulator is to act as a substitute test method for animal models in developing early-stage orthopedic prototypes. For standard animal testing cases, the researcher must pay for the subjects’ upkeep, including feed, housing, and medical bills, as well as comply with the complex animal legislation. Using animal s tudies is a necessary process when evaluating a concept’s safety and efficacy; however, if a different method can replace part of the animal testing, then time, money, and patient stress can be saved. By using the JMS as a research tool in early phases of device development, the researcher will have a faster, cheaper, more accessible, and more humane way to gather data. |
Refinement
Refinement seeks to minimize suffering by improving practices carried out on dogs. When orthopedic surgeons are in training, they first practice surgical procedures on artificial joint models and later progress to live animals. Researchers test the resulting treatments’ performance rudimentarily by hand, without technical feedback. Later, when surgeons move on to live animals, the skill level to perform those procedures may be lacking. Integrating the JMS into their curriculum will enable surgeons to get more useful performance feedback through the measurement and testing tools available, thus better equipping surgeons to operate on live animals. |
Validation Techniques
To ensure that the simulator could accurately represent the motion of a canine hip joint, we measured the accuracy and repeatability of the simulator while following a user-selected motion pattern. We did so on each motor independently and with both motors operating at the same time. Each test scenario was performed 10 times to measure how the simulator behaved over several trials. For each set of tests, the first motion pattern was a sinusoid—a smooth, repetitive oscillation—a standard of motion that allows results to be compared across studies. The second motion pattern was a constant speed of movement, with the start and end points determined
by the typical orientation of the canine hip. The third motion pattern represented a canine’s wal king motion. The canine hip joint normally holds roughly one-fourth
of a dog’s weight— approximately 25 pounds for a medium to large dog. We tested each motion pattern when the motors were not weighted and when the motors
were weighted with 25 pounds. Those motion patterns characterize the simulator’s motor capabilities under various conditions, accounting for most possible scenarios.
The JMS was designed to reproduce joint motion, so the next logical step after validating its movement was to determine its suitability for orthopedic studies.
Therefore, a study comparing surgical procedures for canines was performed, using the simulator to test the system under experimental conditions. Toggle suture constructs—three types of surgical devices for the canine hip—were comparatively tested with the simulator to see which type would work best for a canine joint model. A toggle suture keeps the pelvic bone and the femur in their correct positions after a joint dislocation. The device is considered to have failed when the top of the femur is moved halfway out of the pelvic socket.
When evaluating how the sutures perform, researchers need to test them under normal canine conditions. If the simulator’s performance in experimental conditions deviates from the intended behavior, it could not meaningfully predict the performance in a living system. A veterinarian attached six sutures of each type to the hip
joint of a medium-sized cadaver, and the system was placed into the JMS for testing. The three suture types were the Tightrope, Ethibond, and Securos. The trials were split into three variable range-of-motion phases with different loads and speeds. During each phase, the load applied and repetitions changed to mimic the environments that the canine joint would normally experience. For the study, the motion patterns used were smooth, fluctuating waves for both motors representing a simplification of the types of motions the canine hip joint would experience daily. The JMS can test those motion patterns with variable ranges of motion, under different load amounts, and at different speeds. The combination of the simulator’s capabilities of the simulator and the surgical technique analysis allows for comprehensive results that account for factors that other simulations commonly ignore. The main measurement, derived from the allowances of the surgical procedure throughout the simulation, was of the distance the femoral head moved out from the pelvic socket. That measurement, along with the number of repetitions until failure, was used to measure how well the sutures performed.
To ensure that the simulator could accurately represent the motion of a canine hip joint, we measured the accuracy and repeatability of the simulator while following a user-selected motion pattern. We did so on each motor independently and with both motors operating at the same time. Each test scenario was performed 10 times to measure how the simulator behaved over several trials. For each set of tests, the first motion pattern was a sinusoid—a smooth, repetitive oscillation—a standard of motion that allows results to be compared across studies. The second motion pattern was a constant speed of movement, with the start and end points determined
by the typical orientation of the canine hip. The third motion pattern represented a canine’s wal king motion. The canine hip joint normally holds roughly one-fourth
of a dog’s weight— approximately 25 pounds for a medium to large dog. We tested each motion pattern when the motors were not weighted and when the motors
were weighted with 25 pounds. Those motion patterns characterize the simulator’s motor capabilities under various conditions, accounting for most possible scenarios.
The JMS was designed to reproduce joint motion, so the next logical step after validating its movement was to determine its suitability for orthopedic studies.
Therefore, a study comparing surgical procedures for canines was performed, using the simulator to test the system under experimental conditions. Toggle suture constructs—three types of surgical devices for the canine hip—were comparatively tested with the simulator to see which type would work best for a canine joint model. A toggle suture keeps the pelvic bone and the femur in their correct positions after a joint dislocation. The device is considered to have failed when the top of the femur is moved halfway out of the pelvic socket.
When evaluating how the sutures perform, researchers need to test them under normal canine conditions. If the simulator’s performance in experimental conditions deviates from the intended behavior, it could not meaningfully predict the performance in a living system. A veterinarian attached six sutures of each type to the hip
joint of a medium-sized cadaver, and the system was placed into the JMS for testing. The three suture types were the Tightrope, Ethibond, and Securos. The trials were split into three variable range-of-motion phases with different loads and speeds. During each phase, the load applied and repetitions changed to mimic the environments that the canine joint would normally experience. For the study, the motion patterns used were smooth, fluctuating waves for both motors representing a simplification of the types of motions the canine hip joint would experience daily. The JMS can test those motion patterns with variable ranges of motion, under different load amounts, and at different speeds. The combination of the simulator’s capabilities of the simulator and the surgical technique analysis allows for comprehensive results that account for factors that other simulations commonly ignore. The main measurement, derived from the allowances of the surgical procedure throughout the simulation, was of the distance the femoral head moved out from the pelvic socket. That measurement, along with the number of repetitions until failure, was used to measure how well the sutures performed.
FIGURE 2. Canine hip motion replicated by simulator showing results ±
one standard deviation
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Results
As shown by validation testing, the JMS can mimic the rotational motion of the canine hip joint. The simulator reproduced a simplified model of the canine motion pattern found in the literature.3 While reproducing motions for the canine hip, the simulator accuracy remained within 1.2 degrees of the value in the predicted model throughout our trials, and the average of the position standard deviations— measured using the position data from a specific time over 10 trials—remained below 0.8 degrees. Figure 2 shows those results over one testing cycle. When we compared our validation testing data with other validation studies of similar simulators, the JMS clearly excelled at simulating the motion of a canine joint. The data comparison was helpful for understanding how early concepts of those joint devices behaved under natural movements.4,5 Our results show that the simulator can be an adequate substitute for subjects during preliminary testing of devices or surgical techniques, reducing the number of live animals needed during a study. |
Its effectiveness was shown in the performance comparative study that used the JMS to test types of sutures. Success was evaluated with two criteria:
(1) that the suture lasted through all phases of motion testing and (2) of the specimens that lasted through all three phases, the average displacement of the bones remained low. The Tightrope model had the best performance. All tests using that suture survived to the third phase of motion, showing that the device is best suited
to withstand the normal motion and load that would be present in a real canine. All other models did not survive for all phases of testing. The Tightrope model also had the lowest overall average displacement, suggesting that it would be least likely to fail. Information from such tests helps surgeons effectively choose treatment options; thus, the joint simulator has already proven itself to be an effective alternative to inpatient testing.
(1) that the suture lasted through all phases of motion testing and (2) of the specimens that lasted through all three phases, the average displacement of the bones remained low. The Tightrope model had the best performance. All tests using that suture survived to the third phase of motion, showing that the device is best suited
to withstand the normal motion and load that would be present in a real canine. All other models did not survive for all phases of testing. The Tightrope model also had the lowest overall average displacement, suggesting that it would be least likely to fail. Information from such tests helps surgeons effectively choose treatment options; thus, the joint simulator has already proven itself to be an effective alternative to inpatient testing.
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Discussion
The JMS also can be adapted for many future applications, such as a surgical technique assessment tool. According to a 2012 review of surgical errors, 65% of cases could be attributed to technical error and 29% of cases could be attributed to an error in judgment.6 That finding implies that many errors are due to inexperience, possibly as a result of shortcomings in current surgical training programs. The JMS can provide feedback to the user so that mistakes made in practice can be fixed before a real surgery. |
JMS ALSO CAN BE ADAPTED FOR MANY FUTURE APPLICATIONS, SUCH AS A SURGICAL TECHNIQUE ASSESSMENT TOOL. |
Previous studies have concluded that simulators are effective training tools. A simulation model for knee arthroscopy procedures, the Kneetrainer 1, can distinguish between junior and senior surgeon skill levels and can help surgeons develop their surgical technique.7 The simulator could replicate those findings and even extend them to a broader line of skills because of its adaptability, offering a way to determine the quality of various surgical procedures. One way to apply the JMS as a surgical trainer is by using its dial indicator. That tool measures changes in position—for this experiment, the distance from the femoral head to the hip—generatedby the technique to determines its quality. If the method creates a large displacement in the beginning stages of motion trials or enters a displacement range at which the method is no longer effective, the application can be considered inadequate. Techniques that maintain their position signify quality and longevity of the surgical procedure. Using that method to train surgeons can give trainees access to feedback without the need for live animal trials, thereby improving the overall quality of ensuing surgeries.
Conclusion
The JMS’s performance results during the smooth, fluctuating wave, straight-line, and documented canine motion pattern validation tests have shown the system’s ability to perform as a reliable research tool. Because the JMS’s creators incorporated the three Rs of animal ethics into its design, its presence on the market will improve animal welfare, decrease the number of dogs needed for orthopedic studies, and cultivate a high-quality learning environment for veterinary orthopedic surgeons. The development of the simulator has already helped save dogs from pain associated with animal research and will continue to be dogs’ best friend.
The JMS’s performance results during the smooth, fluctuating wave, straight-line, and documented canine motion pattern validation tests have shown the system’s ability to perform as a reliable research tool. Because the JMS’s creators incorporated the three Rs of animal ethics into its design, its presence on the market will improve animal welfare, decrease the number of dogs needed for orthopedic studies, and cultivate a high-quality learning environment for veterinary orthopedic surgeons. The development of the simulator has already helped save dogs from pain associated with animal research and will continue to be dogs’ best friend.
THE DEVELOPMENT OF THE SIMULATOR HAS ALREADY HELPED SAVE DOGS ...AND WILL CONTINUE TO BE DOGS’ BEST FRIEND.
Amanda Bass '17Amanda Bass is a senior biomedical engineering major from Houston, Texas. Bass has conducted research in the Biomechanical Environments Lab at Texas A&M and plans to pursue her interests in prosthetics and mechanical exoskeleton development in industry after graduation.
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Nathan Dunkelberger '17Nathan Dunkelberger is a 2017 Texas A&M graduate with a degree in mechanical engineering. Dunkelberger is currently pursuing a PhD in mechanical engineering with a specialization in rehabilitation engineering at Rice University and plans to work in the field of medical robotics.
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References
1. United States Department of Agriculture. 2015. Annual Report Animal Usage by Fiscal Year (2015). https://go.usa.gov/xNtQc (PDF, 51 KB). 2. College of Veterinary Medicine—Communications. “Small Animal Orthopedics.” http://vethospital.tamu. edu/small-animal-hospital/orthopedics. 3. Fu, Yang-Chieh, Torres, Bryan T., Budsberg, Steven C., et al. 2010. “Evaluation of a Three-Dimensional Kinematic Model for Canine Gait Analysis.” American Journal of Veterinary Research 71:1118–1122. 4. Giles, J.W., Ferreira, L.M., Athwal, G.S., et al. 2014. “Development and Performance Evaluation of a Multi- PID Muscle Loading Driven In Vitro Active-Motion Shoulder Simulator and Application to Assessing Reverse Total Shoulder Arthroplasty.” Journal of Biomechanical Engineering 136:121007. 5. Noble, L.D. Jr., Colbrunn, R.W., Lee, Dong-Gil, et al. 2010. “Design and Validation of a General Purpose Robotic Testing System for Musculoskeletal Applications.” Journal of Biomechanical Engineering 132:025001. 6. Karam, M.D., Kho, J.Y., Yehyawi, T.M., et al. 2012. “Application of Surgical Skill Simulation Training and Assessment in Orthopaedic Trauma.” Iowa Orthopaedic Journal 32:76–82. 7. Peres, L.R., Alves, W.M. Jr., Coelho, G., et al. 2016. “A New Simulator Model for Knee Arthroscopy Procedures.” Knee Surgery, Sports Traumatology, Arthroscopy doi: 10.1007/s00167-016-4099-9. [Epub ahead of print.] |