Microprocessor Knee Versus Mechanical Knee: Impact on Functional Outcomes in Dysvascular Transfemoral Amputees

In older adults, poor circulation in the lower extremities or dysvascular disease can lead to serious health complications. In addition, these individuals also suffer from serious co-morbidities like diabetes and coronary or cerebrovascular disease. Circulatory dysfunction or dysvascular disease is the major cause for amputations in the United States (www.amputee-coalition.orf/fact_sheet/amp_stats_cause.html). Increasing sedentary lifestyles have lead to increased rates of diabetes which has significantly contributed to an increased number of amputations in recent years. The risk of amputation in a diabetic individual is 25 times higher than in the non-diabetic population. The level of amputation that is appropriate for an individual depends on the extent of damage to his/her tissues. Common amputations of the lower extremities in the dysvascular population include the transtibial and transfemoral amputations. The individual having a transtibial or below knee amputation, will be fitted with a prosthetic foot to assist with functional ambulation, while a person with a transfemoral amputation will require both a prosthetic foot and knee for ambulatory purposes. Currently dysvascular amputees are given prostheses based on the goal of returning them to a basic level of function focused primarily on stability. They are considered lower functioning walkers and are expected to use a slow and constant walking speed to ambulate around their homes and are not considered traditional community ambulators. Therefore, they are traditionally given standard mechanical knees which are considered safe, as they provide the ability for only simple single speed house-hold tasks. While this criterion does return the patient to function for basic Activities of Daily Living (ADLs) and walking at a single cadence, it does not empower the patient to counteract the previously existing co-morbidities. Dysvascular amputees tend to be less active predisposing them to a more sedentary lifestyle and exacerbating their risk factors. Their prostheses make them energy inefficient and use more energy for ADLs and functional walking. This causes early onset of fatigue, induces anxiety and fear of falling. Further, they are often depressed, lose motivation and curtail their community interaction. This raises the question if dysvascular amputees are further functionally limited by the prostheses traditionally given to them.

More recently, technology has been used to assist with return to function in the amputee population. Microprocessor (MP) controlled knees are among the technological innovations applied to prostheses to not only return amputees to a basic function, but also with a view to return them to their highest possible function. Over the years, clinical use has shown that traditional knees provide the ability to complete ADLs and basic functions like sit - stand. However, activities like negotiating stairs/steps, walking on uneven ground and self-correction during tripping; functions which reintegrate amputees into unlimited community ambulation and social reintegration require prosthetics which advanced functionality. The Otto Bock C-leg is a MP knee that allows the patient a greater level of control in swing and stance phases of gait. This enables the TF amputee to adjust the requirements of gait during dynamic walking like changing the speed of walking, going up and down stairs and inclines, walking on grass and uneven surfaces and crossing an obstacle. The C-leg has been traditionally given to patients who begin post-amputation rehabilitation at a higher level, but are more expensive than traditionally mechanical knees. In the contrary however, a European study that defined health outcomes in terms of quality-adjusted life year (QALY), indicated that the C-leg showed a QALY gain of €3218 per patient, makes it still financial viable keeping it mind its price tag.. The purpose of this study is to compare the traditional mechanical knee to the microprocessor knee (C-leg) in the dysvascular population. The study will specifically evaluate the potential of microprocessor knees to improve the quality of life in dysvascular transfemoral amputees. This includes identifying if the C-leg can increase the activity level to be classified at a higher level by the Medicare classification from K2 (lower level ambulators) to K3 (more proficient ambulators), along with increasing their social interaction in the community.