THESIS KINEMATIC AND KINETIC ANALYSIS OF CANINE THORACIC LIMB AMPUTEES AT A TROT Submitted by Sarah Jarvis Graduate Degree Program in Bioengineering In partial fulfillment of the requirements For the Degree of Master of Science Colorado State University Fort Collins, Colorado Fall 2011 Master’s Committee: Advisor: Raoul Reiser Deanna Worley Kevin Haussler ABSTRACT KINEMATIC AND KINETIC ANALYSIS OF CANINE THORACIC LIMB AMPUTEES AT A TROT Most dogs appear to adapt well to the removal of a thoracic limb, but clinically there is a particular subset of dogs that still have problems with gait that seem to be unrelated to age, weight, or breed. The purpose of this study was to objectively characterize biomechanical changes in gait associated with amputation of a thoracic limb. Sixteen amputees and 24 control dogs of various breeds with similar stature and mass greater than 14 kg were recruited and participated in the study. Dogs were trotted across three in-series force platforms as spatial kinematic and ground reaction force data were recorded during the stance phase. Ground reaction forces, impulses, and stance durations were computed as well as stance widths, stride lengths, limb and spinal joint angles. Kinetic results show that thoracic limb amputees have increased stance times and vertical impulses. The remaining thoracic limb and pelvic limb ipsilateral to the side of amputation compensate for the loss of braking, and the ipsilateral pelvic limb also compensates the most for the loss of propulsion. The carpus, and ipsilateral hip and stifle joints are more flexed during stance, and the T1, T13, and L7 joints experience significant differences in spinal motion in both the sagittal and horizontal planes throughout the gait cycle stance phases. The spine, carpus, and ipsilateral hip and stifle joints are of most concern when considering the biomechanical impact that a thoracic limb amputation may have for a given dog. ii TABLE OF CONTENTS I. INTRODUCTION ..........................................................................................................1 II. LITERATURE REVIEW ...................................................................................................5 III. MATERIALS AND METHODS ....................................................................................... 15 Subjects ............................................................................................................................... 15 Subject Measurements ........................................................................................................ 16 Marker Placement ............................................................................................................... 16 Data Collection .................................................................................................................... 17 Gait Parameter Definitions ................................................................................................... 19 Statistics .............................................................................................................................. 21 IV. RESULTS ................................................................................................................... 23 Subjects ............................................................................................................................... 23 Kinetic Data ......................................................................................................................... 27 Kinematic Data .................................................................................................................... 30 V. DISCUSSION .............................................................................................................. 35 VI. CONCLUSION ............................................................................................................ 45 VII. REFERENCES ............................................................................................................. 47 VIII. APPENDIX I: IACUC APPROVAL .................................................................................. 51 IX. APPENDIX II: SUMMARY OF PATIENT EXAMINATION FINDINGS .................................. 54 iii I. INTRODUCTION Limb amputation is standard treatment along with adjuvant chemotherapy for dogs with appendicular osteosarcoma.1-4 This is the most common type of primary bone tumor in dogs5,6 with over 6,000 new diagnoses made each year.7 Most dogs seem to adapt well to the removal of a thoracic limb.8,9 However, clinically there is a particular subset of dogs that do not return to normal or near-normal function even after the expected adaptation period of one month.10 Many propose that age, bodyweight, and breed will affect the dog’s functionality post- amputation,3,10-14 but bodyweight has not been shown to be a contributing factor.10 Additionally, owner surveys encompassing a wide variety of breeds and ages of dogs do not give any indication that these factors negatively impact the ability of a dog to adapt to the loss of a limb.8,9 With these factors unlikely to be the source of poor adaptation for amputees, there must be other factors related to gait that contribute to decreased mobility. It has been suggested that unless there is severe musculoskeletal or neurologic disease already present, any dog should be able to adapt well to a three-legged gait.3 However, there is no clear distinction between severe and moderate degrees of lameness as these are determined clinically through physical examination. One must therefore question whether any degree of musculoskeletal or neurologic disease present in the limbs or spine before amputation could predispose a dog to problems in adapting to a three-legged gait. Osteosarcoma patients often have signs of significant degenerative joint disease in at least one other limb,1 making this a concerning issue for these dogs. 1 Understanding compensatory changes in gait is also important for dogs that have had an amputation due to other reasons, such as traumatic injury, nerve damage, or infection.8,10 Currently, dogs with osteosarcoma rarely live long enough for degenerative conditions such as osteoarthritis to develop secondary to amputation,7,15 but dogs with amputations for other reasons often live many years after amputation8 when these conditions might begin to appear.15 Alternative treatments to limb amputation are available, such as limb-sparing surgery.3,16 However, this aggressive procedure is much more expensive,3 has a high risk of complication,1- 3,16 and has not been shown to result in a significantly greater lifespan for the dog.3,16 Less than 10% of dogs with osteosarcoma survive beyond three years,7 but advances in cancer detection and treatment could extend the life expectancy. In the future, more amputees may live longer and begin to experience problems associated with altered gait. This is especially important for thoracic limb amputees since the majority of osteosarcoma diagnoses are located in the distal radius and humerus.17 Current knowledge of compensation strategies in thoracic limb amputees is limited to kinetic data evaluating ground reaction forces (GRF), impulses, and stance durations in a group of five dogs at the walk.18 Significant differences were found in weight distribution and stance durations where thoracic limb amputees, in comparison to controls, exert an extra 16% of bodyweight on the remaining thoracic limb and an extra 7% of bodyweight on each pelvic limb while applying similar peak vertical GRFs over a shortened stance duration.18 Differences also exist in how amputees compensate for the loss of thoracic limb braking by spending more time than normal braking with the remaining thoracic limb rather than distributing more of the braking impulse to the pelvic limbs.18 2 With such limited data on amputee gait, there is a need to better understand in a larger population of thoracic limb amputees the compensatory mechanisms used that alter loading in the remaining limbs. Analysis of the GRFs only provides a small portion of the picture in understanding amputee gait, and thus a kinematic analysis of the limbs and spine is needed. Kinematic analysis has been used to evaluate gait in dogs that are either clinically normal, have hip dysplasia, or cranial cruciate ligament rupture,15,19-33 but data on amputee kinematics is lacking. Any alteration to normal limb kinematics can significantly change the distribution of force through a joint.34-36 This may lead to instability, muscle dysfunction, pain and decreased range of motion as well as abnormal biological changes such as cartilage degradation, impaired synthesis, and inflammation,35,36 both in the joint of interest and possibly other adjacent joints as well.37 Evidence of changes in maximum and minimum joint angles as well as ranges of motion combined with the knowledge of GRFs would indicate that there are indeed alterations in how the joints are being loaded in amputee gait. As with altered kinematics in the limbs, increased spinal motion may also lead to degenerative changes and issues with muscular control of the joints.27,35,36 Kinematic studies in dogs with hip dysplasia have shown significant differences in lateral pelvic movement, coxofemoral joint abduction-adduction and angular accelerations of the hip.19,32 With these types of compensatory changes appearing in dogs with an intact but diseased limb, one could assume that even greater changes may appear in thoracic limb amputees as