final report - exoskeleton and aclr recovery - zk.tn.xs.pt

Final Project Report: Kurian, Nagasawa, Soto-Sida, Tavelli 1

Proposal for Novel Study Design: Exoskeleton Assisted Plyometric Training for Recovery ACLR Surgery Patients Zina Kurian, Xitlalic Soto-Sida, Trenton Nagasawa, J. Patrick Tavelli Under advisement of Stephanie Norman, Ph.D Department of Bioengineering - School of Engineering Santa Clara University Submitted for Review: 6/5/15 Abstract: The Anterior Cruciate Ligament (ACL) of the knee is of great importance to human biomechanics. It plays a key role in balance, torsional leg stability, and leg bone orientation maintenance. It is also extremely vulnerable to injury, especially in high performing athletes and physically active individuals. Every year a large number of athletes and individuals in the United States suffer some kind of ACL injury. Given the importance of the tendon these injuries are serious and often require surgical intervention or targeted rehabilitation techniques. In either case, the affected individual faces a long and arduous recovery process that will keep them for the most part sedentary and indoors. Trends in treatment/recovery protocol have not changed significantly in the last few decades in direct spite of 1) recent invention and optimization of technologies like supportive exoskeletons, and 2) increased interest in plyometric athletic training. This proposal presents a novel study designed to determine whether or not bringing exoskeleton assisted plyometric recovery exercises improves the ACL reconstruction recovery process. I. Introduction: The Anterior Cruciate Ligament of the knee is one of the most crucial and vulnerable ligaments in the body. It, together with the PCL, provides the necessary force couple within the knee to maintain the joint’s anatomy and directionality. These properties mean that it is one of the predominant anatomical features responsible for the range of motion and degrees of freedom in the knees, and also one of the predominant reasons humans can walk, run, and jump over extended periods of exertion without putting undue strain on the knee joint or muscles of the leg in general. More on this subject will be discussed later under knee anatomy (II.B).

Because of its position in the body and the scope of the loads commonly placed upon it, the ACL is particularly prone to injury relative to other ligaments in the body including the PCL.1 The two predominant mechanisms of injury that lead consistently to ACL injuries include blunt or oblique trauma directly to the leg and torsional trauma or strain placed on the joint and ligament during intense physical activity. Injuries of the former variety often come from football and rugby – full contact sports where direct, high impact force to the side of the knee are commonly observed and possible. Torsional strain to the knee and ACL 1 “Major Injuries in Competitive Athletes.” Brown University Department of Physiology. 5 June 2015. Web.


occurs during sports or activities that require fast changes in direction, balance, or stance. Activities such as skiing, lacrosse, soccer, or basketball.2 In either case, the ACL is prone to tearing transverse to its primary axis. Tears range in severity based on the forces at play during the injury and can be as serious as full ruptures (complete tears with no structural integrity of the ACL maintained). It is these cases (full ruptures) that predominantly need surgical reconstruction. The actual procedure of ACL reconstructive surgery will be discussed in relevant detail later in this paper, but usually relies on tissue grafting from the patellar tendon of the knee. The procedure is highly invasive, effective, and impactful on the patient’s ability to function physically. The typically prescribed recovery timeline (which has remained largely unchanged in the past 30 years) calls for somewhere between four and six months of recovery time and physical therapy before a return to sports.3 This is a very long time for serious athletes and non-serious athletes alike. To be absent from high level competition for so long is devastating to high-level competitors. In noncompetitive athletes the reduced activity levels are correlated variably with a large variety of physiological and mental effects including depression, obesity, and heart disease.4 This problem is significant. Over 200,000 ACL ruptures occur every year in the United States alone. Of these approximately 100,000 are complete enough to require

2 “Anterior Cruciate Ligament.” Massachusetts General Hospital Orthopedics: Sports Medicine Institute. Web. 6 June 2015. 3 Shelbourne, K. D., and P. Nitz. "Accelerated Rehabilitation After Anterior Cruciate Ligament Reconstruction." The American Journal of Sports Medicine 18.3 (1990): 292-99. Print. 4 Hamilton, Marc T., Genevieve N. Healy, David W. Dunstan, Theodore W. Zderic, and Neville Owen. "Too Little Exercise and Too Much Sitting: Inactivity Physiology and the Need for New Recommendations on Sedentary Behavior." Current Cardiovascular Risk Reports 2.4 (2008): 292-98. Print.

reconstructive surgery.5 If one sums up the total time lost from athletic and exercise related activities across these 100,000 patients it amounts to an impressive 20,000-50,000 years of “benched” time annually. This numeral seems difficult to comprehend, but it gets more impressive. According to the American Academy of Orthopedic Surgeons the total cost incurred by society for ACLR operations annually in the United States exceeds $8,000,000,000.6 The problem is real, it is important, and it is costly. That is the objective of this proposal – to propose a study designed to test a theoretical method for speeding up and improving the ACLR recovery process/timeline. The primary method which this study proposes to accomplish this acceleration and improvement is through the use of exoskeleton assisted plyometric training regimens. It seems reasonable to assume that this combination of technology and advanced physical therapy could be used to great benefit in ACLR patients. Plyometric training exercises have been shown to improve physical fitness abilities (like vertical jump height) in health individuals. It stands to reason that the range of motion, extension, and stretch-loading benefits of plyometrics would be helpful in encouraging graft acceptance in ACLR patients if the harmful extreme load effects could be removed (hence the exoskeleton). II. Background: A. Problem Statement: The human anterior cruciate ligament or ACL is an integral component of the biomechanical lower extremity system but is highly injury prone. ACL injuries prevent thousands of

5 “Anterior Cruciate Ligament Injury.” University of California at San Francisco Medical Center: Department of Orthopedic Surgery. 2015. Web. 5 June 2015 6 Porucznik, Mary Ann. "Study Takes Close Look at Impact of ACL Surgery." American Academy of Orthopedic Surgeons. 1 Nov. 2013. Web. 6 June 2015.


athletes and non-athletes alike from engaging in physical activity each year. Current treatment options for these injuries are limiting and time-intensive. By shortening the process of recovery with an exoskeleton and plyometric training regimen it might be possible to lessen the benched time of athletes and the general public. It would also save society significant expense. This is the goal of our research. B. Knee Anatomy: The knee is easily one of the most important joints in body. The knee allows for a large range of motion that allows for movements such as flexing, extension, and medial and lateral rotation. The knee is made up of many different parts. The patella or knee cap is used to cover the tendons and protect them from outside harm. The knee is the point where the femur and the tibia meet. There are 4 key ligaments that connect the tibia and the femur, these are the anterior cruciate ligament (ACL), medial collateral ligament (MCL), lateral collateral ligament (LCL), and posterior cruciate ligament (PCL). For our experiment we focused on the ACL. The ACL is broken into two bundles, the anteromedial and the posterolateral. These names are based on their location attachment. Due to these attachments, the ACL is able to resist anterior translation and medial rotation. The ACL is said to contribute about 90% of total knee joint stability.

Figure 1. A zoomed in image of the knee. The ACL is one of the 4 ligaments in the knee joint that connects the femur and the tibia. The ACL limits forward movement.

The ACL tear is one of the most common knee injuries. Over one-hundred thousand ACL tears occur in the United States a year. The majority of ACL tears also come when not making contact with another person. This generally happens when an athlete or person makes a quick sudden cut or pivot. This is when there is excess strain placed on the knee joint causing the ACL to rupture. C. Current Solutions: There are many different strategies for an ACL tear. The most common for athletes is anterior cruciate ligament reconstruction surgery. What is done in this surgery is that the patient replaces the damaged ACL tissue from the patient’s own body, this is called autograft. The most common place to take tissue from is the knee cap tendon or the hamstring.7 Using a knee arthroscopy a camera the surgeon proceeds to observe the tissues in the patients knee. Making small incisions around the knee, the torn ligament should be removed and then an autograft should be removed as well (if using your own tissue). The surgeon will then insert screws and other devices to hold everything in place.

Figure 2. X-ray image of the anterior knee joint in a patient who has underfone ACLR. Note the pin holding the bone component of the tendon graft in place. There are also non-operative treatments to ACL tears. Most of these are associated with strengthening the ACL or rehabilitation. Most 7 Blahd, William. "Anterior Cruciate Ligament (ACL) Surgery." WebMD. WebMD. Web. 5 June 2015.


of these ACL tears are only possible if the ACL is not completely torn, and the patient must be very careful to not do too many activities that require pivoting or cutting. D. Problems with Current Methods: The current problem with ACL reconstruction surgery tends to be the time spent during recovery. On average, it takes about six months for the patient to return to normal levels of activity. Even then, when a patient returns to normal activity the injured knee doesn’t feel the same. Many patients will see a heavy decrease in their jump height, and will not be able to make as aggressive cuts and pivots. For most athletes this will be devastating not only to their performance, but also for risk of re-injury. This is attributed to the over use of the uninjured side of the body overcompensating for the injured side. Studies have shown that a person who has undergone ACL reconstruction surgery has a 15 times greater likelihood of tearing their ACL again than a patient who has not torn their ACL.8 We look to use an exoskeleton in combination with plyometric exercise in order to combat these issues with ACL reconstruction surgery post operation. E. Plyometric Training: Plyometric training, also known as jump training, is an exercise where the muscles stretch and contract rapidly with a pause in between. The idea behind plyometric training is that each time that you jump your muscles stretch and contract allowing for you to stretch and contract even further ultimately allowing you to jump higher.9 Most exercises consist of quick powerful concentric contractions and highly intense eccentric contraction. This rapid sequence of

8 Porucznik, Mary. "Athletes Risk Second ACL Injury After ACL Reconstruction." Athletes Risk Second ACL Injury After ACL Reconstruction. Web. 6 June 2015. 9 Robinson, Kara. "Plyometrics: What It Is and How to Do It." WebMD. WebMD, 10 July 2014. Web. 4 June 2015.

muscle loading and contraction use the strength and elasticity of muscle and other tissues to improve physical strength.10 The first stage or eccentric phase of plyometric training is the muscle lengthening movement or stretch. Then the power building period is between the two contraction steps. This is considered to be the holding period. The last stage is the eccentric contraction stage where the muscles are finally released to create a more explosive muscle shortening movement.

Figure 3. Pictured above is a male performing plyometric exercise. Note the full range of motion and emphasis on jumping. We believe that if we use this new method of training in combination with exoskeleton technology we will see better recovery in patients. F. Exoskeleton Technology: An exoskeleton can be considered to be a device that a user can wear or control and considered to be an extension of the user’s body. There are not many viable exoskeletons that are on the market for our type of research due to the mobility that we want in our experiment. The majority of the exoskeletons are full body exoskeletons that help people lift, carry, and perform high energy tasks. For our exoskeleton, we wanted to find a flexible,

10 Markovic, Goran. "Does Plyometric Training Improve Vertical Jump Height? A Meta‐analytical Review." British Journal of Sports Medicine. BMJ Group. Web. 5 June 2015.


adjustable, and mobile exoskeleton that would be able to support an ACL reconstruction patient through rehabilitation processes and plyometric training. The exoskeleton that we choose was RoboKnee. The RoboKnee would replace the crutches of a patient a few weeks after the surgery and eventually be able to taper down to no support. The RoboKnee’s design is simple and straightforward, two things that our group found very attractable. It utilizes an off the self-knee brace and series elastic actuator. The series actuator is used to compare the forces and applies the force exerted by the exoskeleton.11 Due to the relatively simple design this system is not only cheaper for the patient compared to most other exoskeletons, but its sleek and slender design allows for the range of mobility we were looking for. In addition the RoboKnee uses a simple algorithm to estimate the knee torque and calculate the amount of force that it needs to apply. This feature was key because we planned to slowly increase the amount of force taken by the knee. This calculated using a positive feedback force amplification loop. First the ground force reaction on the foot is calculated by using the equation τ= R x F where R is the vector from the ground reaction to the knee joint and F is the ground reaction force vector.12 In order to change the estimated knee torque RoboKnee uses a amplification factor alpha. For example is alpha is equal to zero, then the force provided by the exoskeleton is equal to zero. If alpha is equal to one then the force applied by the exoskeleton is 100% of the force needed. The main role that the exoskeleton plays in the experiment is allowing the patient to perform

11 Dollar, Aaron. "Lower Extremity Exoskeletons and Active Orthoses: Challenges and State-of-the-Art." IEEE TRANSACTIONS ON ROBOTICS, VOL. 24, NO. 1. 1 Feb. 2008. Web. 4 June 2015. 12 Pratt, Jerry. "The RoboKnee." An Exoskeleton for Enhancing Strength and Endurance During Walking. IEEE. Web. 4 June 2015.

the plyometric exercises. This allows the patient to perform tasks that he or she would not have been able to do otherwise. This could also help with the problem some patients face of overcompensating and using the non-injured leg too much and straining it. Using the RoboKnee allows for the distribution of weight on each leg to be the same making overcompensation a non-factor.

Figure 4. The RoboKnee design showing the two parts of the series elastic actuator and off the shelf knee brace. Overall, this exoskeleton is quite ideal for our experiment. The only issues that we are faced with are the cost of the exoskeleton and the battery life. As stated before, the cost of the exoskeleton is one of the cheapest out on the market. As for the battery life, the average life is around 30-40 minutes. This limits the use of the exoskeleton for prolonged activites or everyday use. However, since we only plan on using it for assistance in plyometric exercise and replacing crutches from place to place it is still a viable option. III. Experimental Design: A. Experimental Question and Theory: The question that this experiment seeks to answer is whether or not plyometric training regimens, performed with assistance from exoskeletal devices and used in combination with ordinary ACLR recovery therapy plans, have any significant impact on the overall


speed and totality of recovery from ACLR surgery. The theory behind this experiment is simple. Exoskeletal devices, particularly those for the legs and lower body, are designed to supplement human biomechanics to the tune of reducing the load and strain forces on the body while still allowing the same ranges of motion and loading capacities (generally even improved loading capacities). Plyometric exercises tend to improve jumping and activity biomechanics in healthy patients but are typically inaccessible to ACLR patients due to the high strain and load forces that accompany them. We believe that combining the positive health and training effects of extension based plyometric exercises with the ability to mitigate excessive loading forces provided by an exoskeleton, lead to improved ACLR surgery recovery times and more complete recoveries. B. Hypothesis: Given what we know about exoskeletons, physical therapy, plyometric training, and ACL reconstruction recovery time, we predict that we will observe an increase in the total recovery of the patient when encouraged to partake in exoskeleton assisted plyometric training in addition to regular physical therapy. C. Overall Testing Design: To successfully carry out this study we will need to use three separate groups of individuals. Because this study technically seeks to modify two independent variables (with and without plyometric training and with and without exoskeletal assistance) it is imperative that two forms of control group be established. It is also imperative that outside of the control groups each group receive identical treatment within the experiment as regards things that are relevant to ACLR recovery (activity level, exercise, therapy, etc). For this reason, we designed the following groups: − Control: Standard physical therapy

− Treatment 1/Control 2: Standard physical therapy with exoskeleton assistance

− Treatment 2: Standard physical therapy and plyometric training exercises with exoskeleton assistance

This study does not patients remain for its duration in a singular location (like a research facility or their home) which is beneficial as this would most likely have a significant impact on patient quality of life. It is important, though, to ensure the validity of the experiment, that a proctor and qualified trainer be present for all exercise periods to ensure that exercises are performed and performed correctly. It is equally important that the subjects of the experiment be tested at time points when all can engage in the tests. Since patients will be recovering (in theory) at different rates, it is important not to perform jump height recovery tests until later in the study when non-exoskeletal patients can test. Additionally, the study will be carried out with treatments and assessments lasting 24 weeks. There will be two mandatory follow-up assessments: the first after one year and another at two years. This is to ensure that the effects of the study, whatever they turn out to be, will be robust even in the long term. IV. Materials and Methods: A. Participant Selection: The necessity of securing patients who are scheduled for imminent ACLR surgery renders it difficult to maintain truly statistically random selection of study participants. It is important that we select only participant who have not have the operation so that they can all enter the treatment protocols immediately after surgery with no lag time where confounds could be introduced. The best method to both secure enough patients and a random sampling of patients is to offer this study as an opt-in for


pay study13 through all board certified orthopedic surgeons nationwide (to the extent possible). The aid of the AAOS will be solicited to this end. Ultimately the goal is a sample of 90 random ACL injury patients who can then each be assigned randomly to each of 3 treatment groups of 30 patients.

Figure 5. Experimental Design Map. Note that times on the left are listed in months with t=0 being the date of ACLR surgery. Refer to later sections for specific treatments applied to each group. B. Treatment Protocols: The treatment protocols for the three treatment groups will be adjusted to reflect the body of research available regarding each component of the treatment options, but are reflected as current below: B.1 Control Treatment: The control group receives only standard physical therapy throughout the experiment. The PT plan that this study will employ is the widely accepted plan produced by the Massachusetts General Institute of Sports

13 The authors recognize that this may derandomize the sample along socioeconomic lines, but feel that this is not the characteristic of prime importance in selection.

Medicine.14 Each of the exercises described in the plan will be performed for 3 sets of 20 repetitions each twice daily. These exercises and activities will be monitored either remotely on video or in person by a qualified therapist and an experimental proctor to ensure validity. B.2 Treatment 1: The secondary treatment group will perform the identical physical therapy regimen as described above, but with the addition of an exoskeleton. The exoskeleton protocol is will taper the effective support that the device provides – gradually reducing to allow the patient to regain full weight bearing capability slowly. The device will provide 100% assistance (functionally the same as crutches) for the first two weeks post-op. The taper will begin at the end of the second week and follow a linear decrease to 0% assistance by week 16. B.3 Treatment 2 This group of subject will receive the full identical physical therapy regimen that both the control and treatment 1 groups will undergo. This group will also receive exoskeleton assistance according to the same exoskeleton protocol as was prescribed for treatment 1. Additionally, they will perform a plyometric training regimen consisting of the following twice daily (parenthetical references indicate number of sets x number of reps/set):

− Bounding jumps (3 x 20) − Countermovement jumps (3 x 20) − Vertical drop jumps (3 x 20) − Heiden hops (3 x 20)

Like the physical therapy, these exercises will be observed remotely or directly by qualified personnel. C. Evaluation/Testing Protocols: The methods for determining the progress of recovery and abilities of the subjects will make use of plyometric jumping measurements. For

14 “Anterior Cruciate Ligament.” Massachusetts General Hospital Orthopedics: Sports Medicine Institute.


this reason, assessments will only begin to be performed at week 16 of the study and every week thereafter for the remainder of the study so that all subjects can receive the same assessment safely (in theory this should not matter as the recovery effects will be present whether or not we test during the actual recovery progression). Assessments will be performed in a controlled laboratory environment to ensure data accuracy. The actual testing protocol will consist of the following: − 5 consecutive squat vertical jumps − Rest 5 minutes − 5 consecutive countermovement jumps − Rest 5 minutes − 5 consecutive drop jumps − Rest 5 minutes − 3 Filmed drop jumps

For the first 15 jumps, the metric of the assessment will be the vertical flight height, or the vertical distance that the center of gravity of an individual travels. For the final 3 jumps, Landing Error Scoring System scores will be computed and analyzed to determine a relative measurement of jump efficiency and balance.

Figure 6. A diagram showing vertical flight height as h. Ignore the horizontal velocity indicated – our experiments do not involve horizontal motion – only vertical jumps.

F. Data Analysis Protocol: The data collected at each time point or assessment will exist in two forms. There will be quantitatively valuable average vertical flights heights for each of three jumps and then an additional average LESS score provided a relative measure of jump efficiency. Each of these metrics will be tracked over time for each treatment group. Independent tables and graphs will be created showing the change over time in each jump height for each condition and the same will be done for LESS scores. Additional graphs will be created showing all three conditions on one graph for each jump and for LESS scores. These will be used to determine estimated and qualitative efficacy of our treatments. In order to determine the quantitative efficacy, we will perform one way ANOVA tests across all three treatment groups for the mean change in each metric across the experiment and week to week. This will yield a highly robust indication of the validity and efficacy of our treatments. Additional T-tests will be performed within treatment groups to ensure that any change observed across the experiment is actually significant for each type of jump and LESS scores. V. Conclusions: Limitations: The limitations for this experiment include the type of exoskeleton used, technological issues, and study measurements. There may be problems with variation in patient personal ability. A baseline score will counter this potential pitfall. Other issues include measuring participant ability at 6 months, one year, and five years to allow full recovery to be monitored. Some patients may require longer to see full function of knee. The type of exoskeleton used may vary with material. This should be calibrated before the study. It is important to monitor other factors that could influence patient improvement, such as diet,


amount of leisure time spent active, a control group that does outside therapy, bias because of loss of patients to follow-up, or a difference in imaging techniques to capture vertical jump. These limitations should not affect our study because proper planning and controlled technique will minimize variation throughout. Alternative Directions: Further research may include changing one or more variables for type of exercise training, which may include resistance, HIIT, endurance, electrostimulation, or vibration training.15 Additionally, the type of testing could include measurements of squat or gait pattern, vertical ground force, or an EMG for muscle isometric or isotonic contraction activity. Similar studies may compare healthy people against ACLR patients to check performance, or check performance before and after ACL injury. These studies are inferior to our proposed method because it avoids finding direct match candidates for healthy compared controls, and it avoids a timely waiting period for an injury to occur. Since ACL injury is a very painful and long recovery for the patient, studies must be highly likely to show increased efficiency of recovery and reduced idle time. This proposal maximizes resources and patient sensitivity to ability during recovery process. Overall Conclusions: This proposed study design attempts to address the problem with inefficient recovery techniques for ACLR patients. A faster, more efficient, and less painful therapy technique can improve quality of life and reduce the need for further surgeries. By testing the jump height of patients undergoing recovery, the different therapy treatment groups allow researchers to evaluate the best course of treatment. The methods include testing three different treatment groups, and measuring their success 15 Bien, Daniel P., and Thomas J. Dubuque. “Considerations For Late Stage ACL Rehabilitation And Return To Sport To Limit Re‐Injury Risk And Maximize Athletic Performance.” International Journal of Sports Physical Therapy 10.2 (2015): 256–271. Print.

in vertical jump height. Exoskeleton technologies will be able to assist physical therapy protocols in improving totality of recovery. This will be significant for indicating future clinical guidelines in ACL recovery. VI. References: “Anterior Cruciate Ligament Injury.” University of

California at San Francisco Medical Center: Department of Orthopedic Surgery. 2015. Web. 5 June 2015

“Anterior Cruciate Ligament.” Massachusetts General Hospital Orthopedics: Sports Medicine Institute. Web. 6 June 2015.

Blahd, William. "Anterior Cruciate Ligament (ACL) Surgery." WebMD. WebMD. Web. 5 June 2015.

Dollar, Aaron. "Lower Extremity Exoskeletons and Active Orthoses: Challenges and State-of-the-Art." IEEE TRANSACTIONS ON ROBOTICS, VOL. 24, NO. 1. 1 Feb. 2008. Web. 4 June 2015.

Hamilton, Marc T., Genevieve N. Healy, David W. Dunstan, Theodore W. Zderic, and Neville Owen. "Too Little Exercise and Too Much Sitting: Inactivity Physiology and the Need for New Recommendations on Sedentary Behavior." Current Cardiovascular Risk Reports 2.4 (2008): 292-98. Print.

“Major Injuries in Competitive Athletes.” Brown University Department of Physiology. 5 June 2015. Web.

Markovic, Goran. "Does Plyometric Training Improve Vertical Jump Height? A Meta‐analytical Review." British Journal of Sports Medicine. BMJ Group. Web. 5 June 2015.

Porucznik, Mary. "Athletes Risk Second ACL Injury After ACL Reconstruction." Athletes Risk Second ACL Injury After ACL Reconstruction. Web. 6 June 2015.

Porucznik, Mary Ann. "Study Takes Close Look at Impact of ACL Surgery." American Academy of Orthopedic Surgeons. 1 Nov. 2013. Web. 6 June 2015.

Pratt, Jerry. "The RoboKnee." An Exoskeleton for Enhancing Strength and Endurance During Walking. IEEE. Web. 4 June 2015.

Robinson, Kara. "Plyometrics: What It Is and How to Do It." WebMD. WebMD, 10 July 2014. Web. 4 June 2015.

Shelbourne, K. D., and P. Nitz. "Accelerated Rehabilitation After Anterior Cruciate Ligament Reconstruction." The American Journal of Sports Medicine 18.3 (1990): 292-99. Print.

final report - exoskeleton and aclr recovery - zk.tn.xs.pt

Documents