Physical disabilities have been at the forefront of medical science and engineering efforts for decades. Advances in technology have reached a point where disabilities due to traumatic losses of limbs, birth defects, or complications from cancer are able to be almost completely repaired. Yet there is still room for improvement. Most artificial body parts, or prostheses, used to fix the varying disabilities are fitted to unique specifications and only require minor adjustments after that. But what happens when you are dealing with physical disabilities in children? It turns out pediatric prostheses become much more complicated than their traditional counterparts. The prosthetic requirements for children are complex mainly because of the subjects' small size, continuous growth into adulthood, and psychosocial development as they mature. A specific family's financial status plays a crucial role in the decision to use prosthetics for their children as well, especially when private insurance and public funding are scarce [1].
These problems are exactly what families and doctors face when dealing with a youth diagnosed with osteosarcoma. Osteosarcoma is the most common form of bone cancer, and also the 6th most common in children [2]. For years, the only treatment was complete amputation of the affected area and replacement with a prosthetic leg. If families wished to attempt to salvage the limbs around the bones, doctors could go in and replace the bone with a prosthetic implant, but to deal with the leg's constant growth would require multiple expensive surgeries that risked infection and even death. Doctors needed a way to attain equal leg length at skeletal maturity while also decreasing the risks and total cost, and they turned to engineers to find it. Biomechanical engineers at Wright Medical Technologies found the answer by designing the Repiphysis prosthesis, a limb salvage system that expands with the growth rate of the child [3]. This new innovation has made the world of pediatric prostheses more efficient, affordable, and safer for the patient, but more can be done to advance the technology further. This drive to improve an innovation that has already drastically improved a system is what I believe to be the main trait of an engineer, and it is what pushes me to be an engineer in the future.
Children are immature in nature in several senses of the word. In one sense, they are at a psychosocial point in their lives where they are discovering their image, and also who they are and will be for the rest of their lives. In another, their physical selves are immature as well and must handle a large amount of growth over the next several years. These two factors are crucial when handling a patient with pediatric osteosarcoma. There may be many options for treating this cancer, but the thought of having a prosthetic leg is very difficult to come to terms with for a child. It is visible and it can be seen as a handicap in the minds of others. Children do not want to feel obviously different compared to their peers, and that is exactly the type of mindset a prosthesis can create for a child. A child with an exposed prosthesis cannot walk, run, or play like the rest of his or her friends do due to the possibility of damage to it. In addition to this, whenever mechanics are shrunk down to accommodate for a smaller subject, the device becomes more inaccurate. The large change in growth that a patient undergoes will also create a discrepancy in his or her legs, and a countless amount of maintenance and adjustments are required to main equal length in the limbs [4].
The most appealing solution for a patient would be a discrete and simple prosthesis device that could expand as the patient grows. The first part of this option came in the form of an invasive surgery where the leg was opened and the cancerous bone was removed. A prosthetic implant was then inserted and connected to the foot and other connecting bone (usually the knee cap or pelvis). This operation salvaged the limbs of the patient, but it still left a lot to be desired. To fix the inequality in leg length, operations involving reopening the leg were countlessly required for adjustments. This increased the risk of infection, disease, and even death in the patient, and demanded a period of painful rehabilitation. If the leg did become infected, amputation of the limb would be needed, and all efforts would be for nothing [4]. Engineers were given the challenge to create a prosthesis system that would expand on its own and eliminate these risk factors. Many groups designed models that served as building blocks for the system, but it was Wright Medical Technologies that developed the solution and created the Repiphysis expandable prosthesis. As seen in figures 1 and 2, the simple prosthetic implant itself is made of titanium and is wrapped in an aerospace polymer. A condensed spring is held tightly within the polymer by a locking mechanism. When the patient goes in for an expansion, a transmission ring is lined up with the spring and creates an electromagnetic field. This heats the locking mechanism and causes the polymer to soften. Finally, the spring is able to expand to any desired length to achieve leg equality. The entire process is completely non-invasive meaning that no medical instruments need to be introduced into the body and no surgery is required. Doctors are able to monitor the entire expansion process through x-rays. The biggest advantage in my opinion is that the expansion only takes approximately 20 seconds to complete, and no rehabilitation is needed following the process [3]. As Wright puts it, "Children simply get up and walk out of the doctor's office" [3].
The simplistic design of the Repiphysis system allows for many medical advantages for the patient and economic advantages for the family when compared to the conventional modular implant. Both cases require an initial implant surgery, however a conventional implant requires at least four expansion surgeries for larger midsections to expand the system. For the Repiphysis implant, there are no other surgeries required after the initial surgery. That means less hospital stays and less painful rehabilitation for the patient. For the conventional option, the patient goes through strenuous recovery after every surgery they undergo which adds up to 44 weeks. Repiphysis only needs 12 weeks of rehabilitation for the initial surgery. One of the most appealing facts is that compared to the average conventional price of $274,476, the Repiphysis prosthesis will only cost a family $90,368 on average due to its simple design and lack of numerous surgeries. The value and ability of the Repiphysis truly shows promise as an excellent successor to the conventional modular implant [3].
Not only are the design and application of the Repiphysis appealing, but it has shown positive results in real patients as well. A study done in 2010 by a group of researchers at American University and St. Jude's Children's Research Hospital in Tennessee produced very successful statistics for the non-invasive implant. In the study, 17 patients who received a Repiphysis implant for osteosarcoma around the knee were followed from January 2002 to March 2009. The average follow up was 61.7 months. 13 of the patients successfully underwent active expansion (Four patients suffered disease or death after complications from the initial surgery that were unrelated to the actual performance of the implant). Of those 13, five of them are still undergoing expansion and eight of them have fully expanded. All 13 retained leg equality through the process with a limb length discrepancy of 1 cm or less. Finally, functional evaluations using the Musculoskeletal Tumor Society scoring systems gave the implants an average score of 90% [5].
It is these success rates that truly change the face of pediatric prostheses and give children like Enrique Gonzalez hope for the future. Gonzalez was a seven-year-old in 2013 diagnosed with osteosarcoma after a soccer injury brought him to the ER. He received a Repiphysis implant and has been able to avoid both painful rehabilitation and risky surgeries because of it. Due to the innovation that is the Repiphysis non-invasive prosthesis, Enrique and many other children can continue to dance, run, and be themselves without worry [2].
Though the Repiphysis implant is undeniably a huge step forward in the realm of pediatric prostheses, any innovation can always be improved. A study done by researchers in the Department of Orthopedics at the University of Bologna presented 32 patients given expandable prostheses for bone sarcoma of the femur. Both the Repiphysis and Kotz prosthesis were used. The Kotz prosthesis is also a growing prosthesis, but requires surgeries to induce the expansion. The survival rate of the Kotz implant was 90% after both 48 and 72 months. The Repiphysis performed worse in comparsion with survival rates of 60% at 48 months and 32% at 72 months. The difference between these statistics are due to many factors. Even though the small sample size distorts the true survival rate, the Kotz system is able to attain such a high rating due to the fact that it is operated on and improved during the expansion process. The Repiphysis system is left untouched after the initial implantation, so it becomes more prone to mechanical defects, loosening, and even breakage of the prosthesis [6]. The non-invasive option sacrifices some mechanical efficiency in order to avoid risks of infection during repetitive surgeries, while a system like the Kotz prosthesis does the exact opposite. If the Repiphysis was improved to account for the mechanical defects, it would become the absolute solution to pediatric prostheses.
As a freshman in high school, I began to do community service work at the rehabilitation center my mother worked in. She was a physical therapist who worked in pediatrics. There were many patients there dealing with adjustments to prostheses and building their strength. I was able to get a personal look at the struggles and hardships faced by a child with these physical disabilities. Each child had already been through so much personal pain that it was sad seeing them have to struggle with what was supposed to be their cure. I knew there had to be an easier way to get better results.
I find inspiration in the Repiphysis expandable prosthesis due to the very fact that there is more to be done for such a life changing device. When I personally think of what it means to be an engineer, I believe it is not what has already been done that drives them, but what still needs to be accomplished. Engineers need to be forward-thinking and driven to push innovation to new heights. They design the future we live in and therefore cannot look at a specific innovation and say it is good enough. There is always more to be done when it comes to the improvement of someone's life. The Repiphysis system is a prime example of that. It is the start to that "easier way" that I knew would be discovered. It has drastically improved the options for a child diagnosed with osteosarcoma. Now instead of amputation and an obvious prosthesis that requires constant adjustment, a patient can have a discrete prosthesis that salvages the limb and allows for expansion with their natural growth. But there are still ways to improve the system. Stronger material to avoid breakage inside the limb, a sturdier design to eliminate mechanical loosening and failure, and so many other possibilities are out there to make the prosthesis even more efficient for the patient. In my opinion, there is nothing better than knowing you improved the lives of others. This is especially true when dealing with the lives of children. Every child deserves to have a positive childhood, and by eliminating their disabilities, engineers are achieving that. Allowing a child to be a child with no restraint is something incredible that engineers can accomplish if they truly focus. As an engineer, I will be able to go into work every day knowing that what I am doing is making a difference. I knew there had to be an easier way to handle pediatric prostheses, and to be able to be a part of the group that finds that way is what I strive to attain one day.
For many years, a child faced with osteosarcoma only had the option of amputation with a prosthetic replacement. The psychosocial toll of having to deal with such a difference compared to their peers is hard enough for a young child. But they also had to deal with constant adjustments due to their continuous growth. The Repiphysis non-invasive and expandable prosthesis reinvented the way the cancer was handled. Now not only could the limbs surrounding the affected bone be saved, but the risk of infection from surgery was eliminated due to its ability to expand within the limb. However, this is only the beginning of what can be achieved. New innovations will arise that will once again change pediatric prostheses as the Repiphysis system did. The thought that I could be among those who create a new life changing device that has a higher success rate, even less risk, and more durability inspires me every day to achieve my dream of becoming an engineer. Advancements in technology are never-ending, and the fact that engineers harness those advancements to improve the lives of humankind is what truly inspires me.
I would first like to thank my mother, Jeanne Fried, for inspiring me to follow this topic in the medical world. Without her constant support, inspiration, and guidance, I would not be writing this paper here at the University of Pittsburgh. She constantly encourages me to become whatever I want. This encouragement has enabled me to find a topic for this paper that truly motivates me. Secondly, I would like to thank my writing instructor, Mrs. Liberty Ferda, for her reliability and thoroughness when answering any question I had for her. Her guidance through this process has allowed me to write this assignment to the fullest of my ability with confidence. Finally, I would like to thank Hector Li for our remarkable debates during this process. You sparked me to discover new ways of thinking.