Appendix C: Background Research
Introduction
We began by reading the written description of our project given by our client, who is a physical therapist at the Shirley Ryan Ability Lab. The project consists of creating a device for patients with a scissor gait that decreases scissoring and aids patients to take wider steps. Patients with a scissor gait tend to bring their thighs together or cross their legs completely while walking, which impairs their balance and ability to walk independently. We began background research to have a better understanding of scissor gaits and how this problem is currently being treated. Our background research allowed us to prepare and formulate detail-specific questions for our client. We researched four specific topics: (1) pathologies that lead to scissor gait; (2) biomechanics of scissor gait; (3) existing solutions to aid in decreasing scissoring; and (4) current physical therapy for patients.
Pathologies that lead to scissor gait
Scissor gait is a neurological gait disorder that causes either the knees and thighs to press together or cross each other. Scissoring is caused by abnormal muscle tightness (spasticity) in the hip adductors. The hip adductors are responsible for pulling the thighs together and rotating the leg inward. The tightness in the hip adductors forces the thighs inward to cause the scissoring motion.
The main causes of a scissor gait are strokes, cerebral palsy, and multiple sclerosis. Patients who have suffered from strokes experience changes in muscle tone, balance, sensation, and cognition awareness. Similarly, patients who are affected by spastic diplegia (a common form of cerebral palsy) have increased muscle tone, resulting in stiff movements. They tend to develop a scissor gait because of the spasticity in their hip muscles.
Muscle sclerosis (MS) damages the central nervous system, which creates motor tract damage and can develop into an impaired gait. Overall, the changes in spasticity of the muscles, coordination, and awareness can all contribute to a patient developing a scissor gait.
Biomechanics of scissor gait
According to our project description, patients with scissor gaits have trouble walking independently. The scissor gait disrupts the patient’s balance and puts strain on the assisting physical therapist.
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Scissor gaits are mainly caused by abnormal synergy patterns, spasticity in the muscles, and hip weakness.
Synergy patterns are characterized by muscle groups working together to perform a task. Patients who have suffered from a stroke can experience abnormal synergy patterns, where the patient loses independent control of a selected muscle group. An abnormal synergy pattern in the lower extremities can result in a scissor gait.
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Spasticity in the muscles, as mentioned above, refers to abnormal tightness in the muscles. In scissor gaits, this tightness causes the scissoring motion and impairs the patient’s balance.
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Lastly, hip weakness can cause a scissor gait. The hip is supported by hip muscles on both sides of the body. When someone has hip weakness, one support is damaged, leading to an imbalance in stability and the scissoring motion. This is analogous to two pillars holding up a roof (Figure 10). When one pillar is damaged, the roof collapses because of the imbalance.
Figure 10: Hip structure analogous to pillars supporting a roof
Existing solutions
We researched three commonly used products to help people decrease scissoring and take wider steps. They are a gait trainer with an anti-scissoring bar, muscle relaxers/botox, and a SWASH brace.
Gait trainer with anti-scissoring bar
A gait trainer with an anti-scissoring bar creates a physical barrier between a patient’s limbs to prevent scissoring. The barrier can be placed at the ankles or knees depending on the severity of the scissor gait. The gait trainer has a harness and side handles that allow for increased stability in the patient (Figure 11). This product is only available for pediatric patients.
Figure 11: Gait trainer with anti-scissoring bar
Source: <https://www.rehabmart.com/product/antiscissoring-bar-17888.html>
Muscle relaxers/Botox
Muscle relaxers help reduce the spasticity in the hip adductor muscles. Similarly, botox injections reduce the tightness in the muscles by blocking the nerves that cause muscle contractions. However, since the muscle relaxers cannot target a specific muscle group, such as the hip adductors, the whole body experiences fatigue.
SWASH brace
The SWASH brace is a rigid structure with a pelvic and thigh section and rods on the side (Figure 12). The rods on the sides are designed at specific angles to stabilize the hip. The pelvic brace stretches the hip adductors and therefore increases the abduction of the thighs. The brace forces the thighs and knees apart to decrease scissoring and enhance stability in patients. The SWASH brace requires a prescription and needs to be fitted by a physical therapist.
Figure 12: SWASH brace
Source: Allard USA <https://www.allardusa.com/media/wysiwyg/Custom-ToeOFF/A291_SWASH_Clinical_Manual-WEB.pdf>
Current physical therapy for patients
Patients with a scissor gait can undergo physical therapy to improve their walking and stability. There are currently numerous such methods for patients with a scissor gait.
According to our project description, one form of physical therapy used is a taped line down the center of a treadmill to encourage patients to place their feet on either side. However, this method’s success varies depending on the severity of the scissor gait as well as the patient. Another approach our client described was an orange/yellow pathway where the patients place one foot on each color. This method limits the workspace to only the gym where the pathway is. We also researched a common therapy that uses a rigid structure to forcefully separate the legs and makes the patient practice walking repeatedly.
References
Allard USA. “Allard USA SWASH Clinical Manual” Allard USA, Sept-2013. Available: https://www.allardusa.com/media/wysiwyg/Custom-ToeOFF/A291_SWASH_Clinical_Manual-WEB.pdf. [Accessed 17-Jan-2022].
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“Anti-Scissoring Bar for LiteGait Gait Trainers.” Rehabmart. Available: https://www.rehabmart.com/product/antiscissoring-bar-17888.html. [Accessed: 17-Jan-2022].
E. O. Berman, “Walking abnormalities,” UF Health, University of Florida Health, 28-Jul-2021. [Online]. Available: https://ufhealth.org/walking-abnormalities. [Accessed: 16-Jan-2022].
F. Rehab, “Scissoring gait and cerebral palsy: Causes, risks, & treatment,” Flint Rehab, 26-Jul-2021. [Online]. Available: https://www.flintrehab.com/scissoring-gait-cerebral-palsy/. [Accessed: 16-Jan-2022].
“Hip Muscles Pillars.” [Online]. Available: https://www.youtube.com/watch?v=XnLch2WEeBI. [Accessed: 16-Jan-2022].
Sakuma, K., Ohata, K., Izumi, K. et al. Relation between abnormal synergy and gait in patients after stroke. J NeuroEngineering Rehabil 11, 141 (2014). Available: https://doi.org/10.1186/1743-0003-11-141. [Accessed: 17-Jan-2022].