Patient Performance and Outcome: A Comparative Analysis of Microprocessor and Mechanically Controlled Prosthetic Knee Joint

Jason T. Kahle CPO
Westcoast Brace & Limb
Tampa, Florida

The advantages and the medical necessity of a microprocessor-controlled knee over a mechanical-controlled knee (conventional) are unclear, in terms of clinical outcomes. The predominant issue is the absence of fact that a microprocessorcontrolled knee may not yield clinically detectable functional improvement(s) relative to a conventional knee. There is a lack of objective research in the industry to substantiate claims that a microprocessor-controlled knee would improve a patient's function and confidence. However, if a microprocessor does enhance performance, it will encompass a larger scope of patients that would benefit from its capabilities. Therefore, there is a need to establish a protocol for prosthetists to follow that provides clinically objective information. The patient's subjective perspective should also be accounted for, in a comparison. In short, it is important to determine if the patient is benefiting from a knee's capabilities. This study compares the functional difference between a patient's conventional knee and a microprocessor-controlled knee. The study will determine if the knee improves function, perception, performance, and is a medical necessity.

This is an independent twenty patient study that analyzes the actual (objective) and perceived (subjective) performance of the microprocessor-controlled knee (C-Leg) when compared to a conventional knee. The twenty subjects are a convenience sample that range in age from 19- 83. The subjects use conventional components for a period of at least ninety days. They are then tested on an obstacle course. The course includes timing various distances on a level surface and an uneven surface, the measuring of heart rate, and the ability to descend stairs and a ramp. Following physical testing, two subjective tests are administered. One subjective test rates their confidence, stability, and performance on their components. The other subjective test is a patient evaluation questionnaire (PEQ), which rates their perception of confidence, stability, performance, and achievement of activities of daily living with their prosthesis. The patient is then fit into a C-Leg for a period of at least ninety days. The obstacle course test, subjective questionnaire, and PEQ are then retested with the C-Leg. Both tests are videotaped for comparison, documentation, and presentation. The results are compared, contrasted, and evaluated in this study.

There is a clear difference in performance between the microprocessorcontrolled knee and a conventional knee. The microprocessor knee did significantly reduce gait deviations, falls, and stumbles in most patients. It also allowed greater efficiency in ramp and stair descent, although most patients did not utilize its full capabilities (as described by the manufacturer). The walking speeds did increase on the timed distances. The research protocol did help establish a clear difference between the two knees, and assisted the prosthetist and patient in the decision of knee selection. Some patients showed an increase in energy and a decrease in heart rate in the microprocessor-controlled knee. Most patients preferred the microprocessor-controlled knee.

This study clinically establishes if, in fact, the microprocessor-controlled knee improves function and is a medical necessity for most patients. Some patients did not improve in all fields. However, most patients made dramatic improvements. The study contrasts and differentiates the two knees, while providing a template for prosthetists to determine the performance of one knee to another in their own practice. It establishes a protocol to determine whether or not a patient is a candidate for a microprocessorcontrolled knee. The materials and method are designed to be used in any clinical situation. This type of instrument, to determine a component's validity, is essential to the process of justifying the medical necessity and a patient's need.

REFERENCES

  • Walter Reed Army Medical Center Microprocessor Knee Forum/ Patient Evaluation Protocol 2003

  • Gailey The Amputee Mobility Predictor Archives of Physical Medicine and Rehabilitation. May 2002

  • Legro PEQ study in the Archives of Physical Medicine and Rehabilitation. 1998

View the PDF for the Prosthetic Knee Joint Performance Questionanaire