Amandi Rhett, OPS III December 2, 2016

Transcription

1 A COMPARISON OF AN ABOVE THE KNEE AMPUTEE SPRINTER WHO USES A STRAIGHT PYLON NON-ARTICULATING RUNNING PROSTHESIS AND AN ARTICULATING KNEE RUNNING PROSTHESIS TO SPRINT A CASE STUDY Amandi Rhett, OPS III December 2,

2 Abstract TITLE: A COMPARISON OF AN ABOVE THE KNEE AMPUTEE SPRINTER WHO USES A STRAIGHT PYLON NON-ARTICULATING RUNNING PROSTHESIS AND AN ARTICULATING KNEE RUNNING PROSTHESIS TO SPRINT A CASE STUDY Author: Amandi J. Rhett Introduction Little objective data exists on evaluating running performance of transfemoral and above the knee athletes with unilateral amputations. Currently Paralympic regulations allow athletes to use a straight pylon running specific prosthesis (SPRSP) or a mechanical knee running specific prosthesis (MKRSP) in the same classification cohort to compete. This case study compares the running performance variables of contact time, flight time, center of gravity height, stride length, stride frequency, and speed of an elite athlete with a transfemoral amputation that uses both set ups to compete, in order to synthesize the efficiency of using one prosthetic set up over the other. Objectives/Purposes of Research This case study will record data of an elite unilateral above the knee sprinter to compare straight pylon running specific prosthesis (SPRSP) and mechanical knee running specific prosthesis (MKRSP) using the variables listed above. The validation of the protocol and the process, will set the stage for collection of more data, which will help prosthetists and amputee runners understand which set up that will work for them. Methodology (briefly stated) Data collection was carried out using the OptoJump gait analysis system, a modular system consisting of a series of optical sensors designed for athletic use, which accurately detect changes in contact time, flight time, step length, stride frequency, etc. The optojump sensors were positioned on either side of a track lane. Results Results show there is no significant difference in average stride length but a significant difference in average contact time, flight time, center of gravity height, stride frequency and overall speed comparing SPRSP vs MKRSP. Conclusion Case study results favor using a SPRSP over a MKRSP because faster running speeds can be accomplished for this subject. An athlete s performance is impacted by the prosthetic setup and components they choose to run with. Because of several limitations in this study, further analysis of running performance with a greater cohort and normalizing confounders could determine statistically relevant trends in data that would lend evidence to using one prosthetic set up over the other. Key words: mechanical knee running specific prosthesis (MKRSP), straight pylon running specific prosthesis (SPRSP), able-bodied (AB), intact limb (IL) 2

3 Introduction Every four years, the world is captivated by the athletic performances of the athletes that participate in the Paralympic Games, the third largest sporting event in the world. 1 Amputee runners that participate in track and field are emerging as one of the most watched events during the games. There also has been an increase in the number of amputees that have taken up running for recreation. 1 Running specific prostheses (RSP) are specialized prosthetics used for amputees that participate in running on the Paralympic level to use during recreational sports. People with transfemoral (above knee) amputations have two choices for running. One choice is to use a straight pylon setup without a knee. The runner circumducts, or swings their leg around, to run because there is no knee to bend. 2 Alternatively, the prosthesis could incorporate a mechanical knee joint. There is no known objective data comparing the two methods with ablebodied comparable runners. Elite unilateral above the knee sprinters are a unique group that uses these two methods to sprint for competition. A circumducted gait pattern is performed by using the trunk and core muscles to advance the limb forward in a run or sprint for the above the knee amputee, who uses a straight leg pylon set up to run. During takeoff, the hip abductors, trunk muscles, and core muscles activate in order to lift the leg, laterally, off the ground, clear the toe, and place the foot in front of the body, in preparation for the sound limb to take a normal stride. 2 For the above the knee amputee who uses an articulating knee to sprint, the current knee of choice is the Ottobock 3S80, a single axis mechanical fluid hydraulic knee joint, where the rotary hydraulic controls can accommodate rapid flexion and extension in response to different running speeds. 3 Alignment of the knee and foot of the prosthesis is vital in order to provide stability from initial contact to terminal stance. 3

4 Paralympic athletes are classified based on their functional impairments, and the impact those functional impairments have on specific sport performance. The classification system is designed to promote fairness in athletic competition by normalizing the impact of the functional deficit on sport between athletes. In Athletics, the designation T denotes track events, and the designation F denotes field events. 4 Classification T- 42 includes unilateral and bilateral above knee amputees and athletes with other impairments that are comparable to a single above knee amputation. This includes athletes with loss of muscle power in the lower limbs. 4,5 The International Paralympic Committee s (IPC) document titled Position Statement on background and scientific rationale for classification in Paralympic sport states that a fundamental concept of the Paralympic classification system is to minimize the impact of impairment on the outcome of competition. 4,5 Additionally, the document states that In the competitive arena, many sports permit classified athletes to use individualized positioning and techniques, as well as strapping and other aids, which effectively alter the activity that each individual does in a way that minimizes the impact of an individual s impairment, thereby enhancing performance. Use of individualized adaptations should not affect the class that an athlete is allocated. However sports technical officials must be cognizant of the impact that each individualized adaption will have and ensure that technical rules governing permissible techniques and aids (including the materials that aids are made of) regulate their use so that the integrity of the sport is maintained. 5,6 The use of prosthetic knees versus straight pylon prosthesis to compete in the same classification, raises the question: How much is the measure of an athlete s performance, in the same Class, impacted by the prosthetic setup and components they choose to run with? 4

5 Top speed during constant speed running is a product of step frequency, contact length, and average ground reaction force applied to the running surface during foot contact with the ground. 7,8,9 There are three mechanical variables which constrained the speed of human runners. Stride frequency is how quickly the limbs can be repositioned for successive steps to achieve a shorter swing time. Stride length is the forward distance the body travels while the foot is in contact with the ground. The ground reaction force magnitude is how much force the limbs can apply to the ground in relation to the body s weight. If one or more of these variables could be improved, running speeds would be enhanced. 9,10 Results of a previous study by Hobara, 2015, showed that average velocity was greatest in able bodied sprinters, followed by bilateral transtibial, unilateral transtibial, and then transfemoral amputee sprinters. This previous study used video analysis of elite level ablebodied and elite level athletes with amputations,. 11 Unilateral transfemoral amputee runners were shown to have greater asymmetry between the amputation side and sound limb. The goal of this research study is to evaluate how athletic performance is impacted by using a SPRSP vs MKRSP. We will objectively evaluate contact times, flight times, center of gravity height, stride length, stride frequency, and overall speed of a T42 class elite level sprinter with a unilateral above the knee amputation, in order to synthesize evidence based recommendations on the efficiency of using one method versus the other. Research Objectives This study compared a unilateral transfemoral elite athlete that competes in the T42 class that uses both a SP RSP and a MKRSP to sprint. This study will compare the running set ups against each other to see how much the prosthetic set up influences running performance. 5

6 Methods One Paralympic elite athlete with a right unilateral transfemoral amputation was included in this study. The subject was well trained using a RSP with the Ottobock 3S80 mechanical hydraulic knee joint and a straight pylon running specific prosthesis. Subject used both prosthetic setups for sprinting. Both prostheses use a suction suspension type socket and Ossur Cheetah Xtreme foot. Subject wore their existing RSP optimized for sprinting events for testing. Data collection was performed in collaboration with Nike Biomechanics Lab at the Michael Johnson Performance Center in McKinney, TX. The testing protocol was carried out using the OptoJump system. The OptoJump gait analysis system is a measurement system consisting of meter long transmitting and receiving bars. Each bar contains 96 leds that communicate continuously between the transmitting and receiving bars. The system is able to detect interruptions in the transmission, and calculate and record the duration. 12 A modular system was used in this study where a track lane was lined on each side with 12, 2 meter long, bars connected in sequence to create 24 meters of data collection. Configuration for this study is similar to Figure 1: Photo of OptoJump modular system. The subject ran a 30 meter fly, to build up to a constant speed, before data was collected, and slow down after data collection was complete. Subject ran a total of eight trials. The first tested condition used the MKRSP for two trials then SPRSP for two trials. The conditions were reversed for the third and fourth set of trials to decrease bias in data toward a prosthetic set up. A full recovery rest period, determined by the athlete, but not exceeding 10 minutes, was given in between trials, and a longer rest period, not exceeding 20 minutes rest, was given in between the first four trials and the second four trials. The subject followed self-selected warm up, cool down, maximum velocity, and recovery procedures during the study. 6

7 Variables collected were flight times, contact times, height, stride length, stride frequency, speed, stance phase, contact phase, and foot flat. Contact time, measured in seconds, is the time the foot is in contact with the ground. Flight time, also measured in seconds, is the time where there is no ground contact. Height, measured in meters, is the variation of the center of gravity height during the execution of the runs. Stride length, measured in meters, is defined as the distance between the tips of two consecutive feet. Stride frequency, measured in steps/second, is defined as the number of steps through the data collection period. Contact phase imbalance, measured in seconds, is defined as the amount of time imbalance between the right and left leg as they contact the ground. Speed, measured in meters/second, is defined as the measure of distance covered over a period of time. 12 Statistical analyses The average, median, and standard deviation of the data sets, including contact time, flight time, height, stride length, stride frequency, and speed were calculated. A t-test was performed on the data sets to find statistically significant differences in values. The t-test value translates to the p-value of which less than 0.05 confidence interval shows statistically significant difference in calculated average data. 7

8 Results Step Count Side Tflight (s) Tcontact (s) Height (m) Stride Length (m) Avg Stride Frequncy; Pace (steps/s) Avg Speed (m/s) MKRSP SPRSP MKRSP SPRSP MKRSP SPRSP MKRSP SPRSP MKRSP SPRSP MKRSP SPRSP 1 R L R L R L R L AVERAGE VALUES Table 1.1 Variable Data and Average Values Tflight (s) Tcontact (s) Height (m) Stride Length (m) Avg Stride Frequncy; Pace (steps/s) Avg Speed (m/s) MKRSP Right Left Right Left Right Left Right Left Right Left Right Left Average Median Stdev T-test Average Median Stdev SPRSP Table 1.2 Statistical Analyses of Variables Right Prosthetic Leg Left Intact Limb Variable MKRSP SPRSP p-value MKRSP SPRSP p-value Contact Time (s) Flight Time (s) Height (m) Average Stride Length (m) Average Stride Frequency (steps/s) Average Speed (m/s) Table 1.3 MKRSP vs SPRSP Statistics Summary Table 1.3 compares the individual strides of the MKRSP and SPRSP. The data shows whether there is a statistically relevant difference in average values when individual strides, the 8

9 right prosthetic limb and left intact limb, are present. Figure 2 through Figure 5 show overall average graphical representations of variables compared to one another per Table 1.1. The results of the p-values calculated reveal no statistically significant difference in the average stride length, average height of the intact limb, and flight time of the intact limb. There is a statistically significant difference in the contact times, height and flight times for the right prosthetic leg, stride frequency, and speed. Discussion Results show that the there is a statistically relevant difference in the average contact times of the MKRSP and the SPRSP, where there is greater ground contact time using the MKRSP then the SPRSP for both for the right prosthetic limb and intact limb. Consequently, there is a statistically relevant average increase in flight time in the right prosthetic leg using the MKRSP over the SPRSP. Both limbs of the MKRSP have a statistically relevant lower average frequency and speed then the limbs of the SPRSP. The subject is moving slower when using the MKRSP set up. The right prosthetic limb of the MKRSP has a statistically relevant higher center of gravity then the SPRSP, which also correspond to the increase in flight time average over the SPRSP prosthetic limb. Data shows no statistically significant difference in average stride length between the two set ups nor flight time and corresponding height of the center of gravity. Results lend to using the SPRSP for faster running times due to the average increase in stride frequency, and consequent reduction in contact and flight times, over the distance measured. The subject reported preference using the SPRSP during athletic competition. The subject is 80 lbs and reported that the MKRSP adds about 6 lbs, versus the SPRSP, which is about 2 lbs. Alignment of the knee of a MKRSP was critical to optimize running performance and was continuously being tweaked for optimization, even during data collection. The 9

10 prosthetic knee needs to extended prematurely in swing, and remain fully extended until late stance phase. 10 The added complexity of the function of the knee, along with the increase in physical weight of the MKRSP, perhaps limited the MKRSP from outperforming the SPRSP in testing. Additionally, fatigue may have played a role in results due to the repetitive, full speed, trials, performed by the subject. The potential confounder of proficiency in the use of the different prosthetic set ups was minimized in this study because the subject was well trained to use both. The results obtained will be more generalizable to any amputee using the prosthetic set-ups tested. With this in mind, there are several limitations to this study. The population of elite level athletes with a transfemoral amputation that use both an SPRSP and MKESP is very small in comparison to elite able bodied sprinters. Most of these athletes either chose to run with the SPRSP or MKRSP to sprint. Variables that support an athlete s choice to use one method over the other may include, but are not limited, an athlete s preference of method, existing musculature that makes one method preferred over the other, and/or the time and effort it takes for the athlete to acclimatize and develop the proficiency of use of that method in competition. All of these variables have a level of subjectivity, where objective comparison of the two methods may be difficult to achieve. A study with a larger cohort, normalizing confounders such as height, weight, and amputation level would further bolster conclusions from this future study. Additionally, gait analysis of an athletes using both prosthetic setups may yield trends or patterns in functional ability and performance to aid in the advancement of prosthetic componentry. 10

11 Conclusion Data from this case study lends to using the SPRSP over the MKRSP for this subject. An athlete s performance is impacted by the prosthetic setup and components they choose to run with. However, further analysis of running performance with a greater cohort and normalizing confounders could determine statistically relevant trends in data that would lend evidence to using one prosthetic set up over the other. 11

12 References 1. International Paralympic Committee (IPC): Official Website of the Paralympic Movement IPC Lusardi M.: Athletic Options for Persons with Amputation, In: Orthotics and Prosthetic in Rehabilitation. 3 rd ed. St. Louis, Mo: Saunders; P Otto Bock Healthcare LP. Fitness Knee Information Brochure ormation_brochure.pdf 4. International Paralympic Committee: Athletics Rules and Regulations Tweedy, S.: IPC Athletics Classification Project for Physical Impairment, 16 July IPC Athletics Classification Project, School of Human Movement Studies, University Of Queensland. IPC Athletics Classification Project for Physical Impairments: Final Report - Stage. Research Report 6. International Paralympic Committee.: Position Statement on background and scientific rationale for classification in Paralympic sport. Chapter December Wening, J., Stockwell, M.: Oxygen consumption and prosthetic moments for two transfemoral amputees running with and without a knee. American Academy of Orthotists & Prosthetists 38th Academy Annual Meeting and Scientific Symposium, March 21-24, Weyand, P.G., Sandell, R.F, Prime, D.N and Bundle, M.W.: The biological limits to running speeds are imposed from the ground up. Journal of Applied Physiology, 2010; 108: , 12

13 9. Weyand, P.G., Sternlight, D.B., Bellizzi, M.J. and Wright, S.: Faster top running speeds are achieved with greater ground forces not more rapid leg movements. Journal of Applied Physiology, , 2000; Buckley, JG.:.Sprint Kinematics of Athletes With Lower-Limb Amputations. Physical Medicine and Rehabilitation 1999; 80: Hobara H, Kobayashi Y, Mochimaru M.: Spatiotemporal variables of able-bodied and amputee sprinters in men 's 100-m sprint. Int J Sports Med., in press. 12. Micrograte: Users Manual Moen, B.: Determining Compensatory Muscle Activations in Sprinters with Lower Limb Amputations. IRB Procedure Section. BCM Weyand, P.G. and Bundle, M.W.. Point: Artificial limbs do make artificially fast running speeds possible. Journal of Applied Physiology, 2010; 108: Grabowski AM, McGowan CP, McDermott WJ, Beale MT, Kram R, Herr HM: Running specific prostheses limit ground-force during sprinting. 2010; Biol Lett. 6 (2):

14 Tables and Figures Figure 1 Photo of OptoJump modular system ( Gallery/On-the-field.aspx?fileid=200) 14

15 Average Contact Time (s) Straight Pylon Knee Figure 1 Average Contact Time Average Flight Time (s) Straight Pylon Knee Figure 2 Average Flight Time Average Height (m) Straight Pylon Knee Figure 3 Average Height 15

16 Average Stride Length (m) Straight Pylon Knee Figure 4 Average Stride Length Average Stride Frequency (Steps/s) Straight Pylon Knee Figure 5 Average Stride Frequency Average Speed m/s Straight Pylon Knee Figure 6 Average Speed 16

17 Appendix IRB Approval protocol Nike Biomechanics Lab Letter of Support 17