Measurement of Tibial Translation in Dogs with Anterior Cruciate Ligament Rupture October 17, 2009 Team: Graham Bousley: Team Leader Alex Bloomquist: Communicator James Madsen: BSAC Mike Nonte: BWIG Client: Prof. Peter Muir Advisor: Prof. Wan-Ju Li 1 Abstract: Arthritis is the major cause of ACL rupture in canines and a quantitative, minimally invasive diagnostic device is needed to increase the quality of healthcare for canines as well as reduce costs. The device will measure tibial translation and force exerted on the canine’s paw during the tibial thrust test. This data will be plotted and from this graph the state of the ACL will be determined. The design consists of two needles inserted at anatomical markers in line with the ACL. The distance that separates these two markers is measured by the Hall Effect sensor. In the future, a final prototype will be built and used in clinical cases and applications to humans will be explored. 2 Table of Contents Abstract ......................................................................................................................................................... 2 Problem Statement ........................................................................................................................................ 4 Background ................................................................................................................................................... 4 Current Methods of Diagnosis ...................................................................................................................... 6 Design Constraints ........................................................................................................................................ 7 Current Device .............................................................................................................................................. 7 Hall Effect ..................................................................................................................................................... 8 Load Cell ....................................................................................................................................................... 9 Future Work ................................................................................................................................................ 10 References ................................................................................................................................................... 11 Product Design Specifications .................................................................................................................... 12 3 Problem Statement: Arthritis in canines often leads to joint degeneration and rupture of the Anterior Cruciate Ligament (ACL). Diagnosis of this condition is often difficult because the current methods used are non-quantitative. The aim of this project is to quantify the amount of tibial translation in a canine’s leg caused by a known applied force in order to determine the severity of an ACL rupture. Preliminary parts for a device that can accomplish this aim have been developed and it is the goal of this team to create and test a working model. Background: Dr. Peter Muir conducts research on the anterior cruciate ligament, ACL, in canines. He and his colleagues have come up with an apparatus to measure the displacement of a canine’s tibia when a force is applied to the paw. This allows for an accurate reading of the severity of the ACL rupture. The ACL has an important biomechanical function; it prevents hyperextension, internal rotation and anterior-posterior translation (DeRooster 777). The ACL is located between the tibia and femur in the canine knee; it can be seen in the posterior view of the canine knee in Figure 1. The ACL is labeled cranial cruciate ligament in Figure 1. ACL rupture is a common medical diagnosis in canines. Dogs with ACL rupture usually have inflammation in the synovial membrane and fluid. This inflammation deteriorates the canine’s ACL gradually over time. Current diagnosis of ACL rupture in dogs is only qualitative, and must be performed by an experienced veterinarian. The diagnosis is performed by applying a force on the paw, while holding the femur in place. This creates a displacement across the Figure 1 4 tibia and the experienced veterinarian must use his judgment on the severity of the canine’s ACL rupture (Harasen 1). This is shown in Figure 2. The device design allows it to be applicable to many different-sized canines. For example, the canines can range from a Yorkshire Terrier (1.5kg) to a Mastiff (up to 100kg). The designed apparatus will allow for a quantitative measurement of the severity of the ACL rupture, leading to intervention during earlier stages of the disease. Earlier diagnosis may help preserve ACL properties by preventing further collagen degradation (DeRooster 769). This will decrease the need for ACL surgery and reduce the financial burden of ACL rupture. The anatomical markers for the placement of the needles on the device are shown in Figure 3. They are located in between the fabella and femur, and between the top of the tibia and the femur. An experienced veterinarian would easily find these anatomical markers. Figure 2 Figure 3 5 Current Methods of Diagnosis: Non-invasive methods of determining the presence of ACL deterioration in canines include the drawer test, the tibial thrust test, and stress radiography. To perform the drawer test, the veterinarian stabilizes the canine femur with one hand while manipulating the tibia with the other hand (Figure 4). The veterinarian subjectively assesses the extent of the forward translation to determine if the ACL is ruptured. To perform the tibial thrust test the veterinarian stabilizes the femur with his hand while flexing the canine paw with the other hand. Again, the veterinarian assesses the extent of forward tibial translation to determine if the ACL is ruptured. Often it is necessary to sedate the canine for both tests because tension in the canine leg muscles can prevent tibial translation and thus obscure the result of the test (www.dogkneeinjury.com). Diagnosis of partial ACL deterioration is difficult using these tests due to their subjective assessment of tibial translation (DeRooster 573). Figure 4 Stress radiography may
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