Microprocessor Prosthetic Knee Use for Trans-femoral Amputees - Essay Example

MICROPROCESSOR PROSTHETIC KNEE USE FOR TRANSFEMORAL AMPUTEES BACKGROUND Amputation is a serious life-changing event in a human being's life, bringing about one of the most prominent, sudden, and, in most cases, unexpected turning points in his or her life. Amputation has an impact on several aspects of an individual's activities, including activities of daily living, employment, social life, personal relationships and recreation. In this context, the artificial limb plays a very important role in the betterment of an amputee's quality of life. There has been evidence of artificial limbs being used from the days of yore. An artificial leg made of copper and wood was found in a tomb in Capua, Italy, which was from as far back as 300 BCE.1 Iron prostheses were in use in the 15th and 16th centuries. The 19th century saw the use of more advanced lighter-weight prostheses made of wood. It has been found that amputations are largely due to trauma in developing countries while they are from vascular reasons in the developed countries.2 Vascular problems are usually associated with a lot of other illnesses which may limit a person's mobility and hence eliminate the urgent need for an advanced prosthesis. On the contrary, post-trauma amputees are usually younger with more active lifestyles and hence are candidates for advanced prosthetic placements so as to ensure uncompromised quality of life. PRODUCTS AND FEATURES Conventional mechanically controlled prostheses utilize a pneumatic or hydraulic damper to provide the appropriate gait parameters for the user at his or her conventional normal walking speed.3 The adjustment is usually effected by a prosthetist. When there is a change in walking speed, the pendulum action of the prosthesis for the change in stride or step is compensated by tilting the pelvis or such other physical maneuvers which delay the extension so that the foot is appropriately placed for the next step. These physical negotiations not only mar the flow of the gait but also use up more energy. Mauch Knee4 from Ossur is a nonmicroprocessor-controlled prosthetic knee, which claims to have the ability to control knee stability under changing conditions and to walk at varying speeds. The flexibility of Mauch helps the user in negotiating stairs and ramps more naturally and even gives appropriate support for running and cycling. The basic concept of the microprocessor-controlled lower limb prosthesis is the use of a microprocessor-controlled damper with the help of which step time is measured and knee extension is adjusted to changing walking speeds. The first computer-controlled prosthesis was devised by Blatchford in the early 1990s with a view to improving the amputees' symmetry of gait over a wide a range of walking speeds. The "Intelligent Prosthesis (IP)," as it was called, programs the knee to optimum swing settings for each individual user to achieve the smoothest gait pattern with less energy expense.5 A pneumatic control unit in the knee senses speed changes and adjusts the swinging speed of the prosthesis, making the gait not only look natural but also feel natural for the user. However, the IP works well only on even surfaces. In 1998, Blatchford introduced the more advanced Adaptive Prosthesis. The Adaptive Prosthesis has a microcomputer that adjusts to the change in terrain underfoot and its combination of hydraulics and pneumatics assisted weightbearing and responded to changes in the walking speed. The Adaptive Prosthesis provides the required degree of stability for walking, standing and climbing as needed by each individual user. The IP+ of Blatchford offers individually programmed microprocessor cadence control, stance stability to provide a natural gait, and a Stanceflex unit that helps reduce shock during heel strike. The Smart IP of Blatchford, in addition to all of the above features, can be re-programmed at any time by the user for footwear and activity level changes. The Smart IP claims through its studies and trials that with its intelligent pneumatic swing control, the transfemoral amputees use up less amounts of energy, especially at slower walking speeds. According to trials amputees, it matches gait perfectly. This renders smoother transition and a more relaxed gait. The Smart IP does not necessitate study and recall of detailed programming instructions. The user can re-program it himself or herself and this helps do away with a lot of return visits and prolonged time in the clinic. The C-Leg from Otto Bock is a microprocessor-controlled knee prosthesis which was also devised with the amputees' improved quality of life in mind. As compared to the non-microprocessor-controlled knee prostheses, which controlled flexion and extension passively with a mechanical unit, the C-Leg with its microprocessor assured dynamic control of flexion and extension during swing and stance phase, which increased the functional level of the user.6 Sensors in the shin of the C-Leg continually assessed the position of the leg in space while the user is walking, which data were simultaneously fed into a microprocessor inside the knee and the knee stiffness was adjusted throughout the gait cycle by adjusting resistance from a hydraulic damper. In comparison to a conventional non-microprocessor-controlled knee prosthesis, the C-Leg proved to be more advantageous as it offered easier negotiation of stairs and uneven and hilly terrain, decreased risk of stumbles and falls, decreased difficulty in multi-tasking, higher user satisfaction, lower rate of energy expense, and smoother gait. The Rheo Knee7 from Ossur is claimed to be a synergy of artificial intelligence and advanced sensor and magnetorheological actuator technologies which ensures more natural movements and hence better quality of life. With continual monitoring and optimization, the Rheo provides ongoing prosthetic adjustments even after the setting up of the initial program by the prosthetist. The magnetorheological fluid actuator ensures natural pelvic position. Advanced sensing and processing checks unexpected stance release. The initial programming for the Rheo is automatic. For a comparative study of all these prostheses, it is necessary to judge their efficiency both qualitatively and quantitatively. QUANTITATIVE MEASURES Effective comparison of different types of prostheses would be possible only if quantitative evaluations are made of the different relevant functions and features of the prostheses. Biomechanical Performance Biomechanical studies detect step time and alter knee extension level to suit walking speed8. It is the biomechanical performance that renders the gait close to natural. Biomechanical performance evaluation also includes evaluation of hip work production and hip work and knee flexion and hip flexion moment. In a study done by Johansson et al.,9 as compared with Mauch, Rheo had the biomechanical benefits like decrease in hip work production and lower peak hip flexion moment at terminal swing. There was reduced peak hip power generation at toe-off. Mauch had an exaggerated hip control and a larger peak knee moment during terminal swing. This meant that the Rheo required less effort than Mauch during the swing phase of walking. The biomechanical advantages also included improved smoothness of gait. Stance Flexion and Stance Stability The biggest discomfort that a thigh amputee faces is having to hold the prosthetic knee in full extension throughout the stance phase of the gait cycle to stop the leg from collapsing.10 This renders the gait unnatural and rule out the shock absorption feature of the biological knee. The stance flexion feature was designed to obviate this drawback of the prosthetic knees. The Blatchford of UK called this feature the bouncy knee. Blatchford countered this problem by introducing a friction brake that functions automatically during weightbearing, stabilizing the knee, along with a rubber component that absorbs the shock during heel strike, allowing a small degree of motion and simulating knee flexion. The evaluation of stability of stance is imperative in the study of the efficiency of a knee prosthesis. The Rheo, by actively modulating knee joint damping, provided more stability of stance when compared with Mauch which was mechanically passive. The study by Johansson et al.9(p11) also brought out, in addition to the differences in the stance period of walking, the fact that the Rheo required less effort, as compared to Mauch, during the swing phase. Gait, Balance and Gait Symmetry The evaluation of gait, how close it is to the natural gait pattern of the user, is a parameter that directly points to the efficiency of the knee prosthesis. The Intelligent Prosthesis is known to offer a closer to normal gait pattern to the user when compared to the mechanically controlled prosthesis during the swing phase of the gait cycle. This allows the user to walk efficiently and with confidence. According to the trials amputees, the Smart IP matched their gait perfectly. Balance and stability are two aspects of gait, which is imperative for the safe mobility of the individual. Loss of balance and stability add to the risk of fall. A study by Kaufman et al.11 used a crossover design to study 15 prosthesis users with above-knee amputation. Transfemoral amputees using the microprocessor-controlled knee showed improved gait and balance as compared to the mechanical prosthesis. According to the VATAP (VA Technology Assessment Program),12 the potential benefits of the C-Leg include decreased effort in walking, improved symmetry of gait which is more natural, lesser difficulty in adjusting to uneven terrain and stairs and inclines, and lesser risk of falls. Stumbles and Falls For an amputee using a knee prosthesis, risk of fall is very dangerous and should be avoided at all costs. Evaluation of stumble recovery and risk of fall in a knee prosthesis directly points to its efficiency and safety for the user. Another study conducted by Kahle et al.,13 compares amputees' performance with nonmicroprocessor knee mechanism and with the C-Leg. The study demonstrated decreased reports of stumbles and falls. Energy Consumption Using prosthesis requires use of effort for physical maneuvering, negotiation of steps and movement, etc. The lesser the energy cost or the oxygen consumption for using a prosthesis, the greater the comfort for the user. On a comparative study of oxygen consumption and gait pattern in amputees using the Intelligent Prosthesis and the conventional prosthesis with the damped knee swing-phase control, it was found that the energy requirements may be reduced for the Intelligent Prosthesis at speeds that were more or less than the user's usual speed, but at customary speeds, the energy requirements with both prostheses were not remarkably different.14 Chin et al.15 conducted a study of energy expenditure in walking, in three patients of ages between 51 and 55 years, with unilateral disarticulation of the hip. Two patients demonstrated decreased expense of energy of 10.3% to 39.6% while using the Intelligent Prosthesis as against using the Otto Bock 3R15 which is a mechanically controlled device. One patient did not show any significant difference in the uptake of oxygen at 30 m/min, but there was a decrease in uptake of 10.5% to 11.6% at 50-70 m/min when using the IP. The effect of different prosthetic alignments and components on oxygen consumption and biomechanical features of gait pattern was delved into by Schmalz et al.16 There was reduced oxygen consumption associated with electronically controlled knee joint when compared with conventional knee controls. A comparison of energy expenditure and stride features with three different prostheses in the setting of bilateral knee disarticulations by Perry et al.17 revealed that the C-Leg was the most efficient with the least oxygen consumption. Walking Speed Walking speed affects the activity level of a prosthesis user and is a very important quantitative measure for evaluating the efficiency of a prosthesis. In the study conducted by Kahle et al.,13(p9) self-selected walking speed on even terrain (75 m), fastest possible walking speed on even terrain (75 m), fastest possible walking speed on uneven terrain (38 m), and fastest possible walking speed on even terrain (6m) were evaluated. The study demonstrated improved walking speeds with the C-Leg. Stair Descent Evaluation of the efficiency with stair descent is necessary for evaluating a knee prosthesis. In the test by Kahle et al.,13(6) the MRPP (Montreal Rehabilitation Performance Profile Performance composite scores) was used to evaluate stair descent because it considers a step-over-step pattern, cueing (verbal, tactile, and stabilizing), rate of descent, and errors in foot placement of the leading leg. The study found that the subjects improved their stair descent with the C-Leg. Vertical load, ankle movement and knee joint movement are some of the other quantitative measures that are evaluated with stance and other biomechanical features. QUALITATIVE MEASURES Qualitative measures evaluates the subjective experiences of the patient. Satisfaction Evaluation of user satisfaction is an important qualitative measure in evaluating a prosthesis. According to a study by Hafner et al.,18 subject satisfaction was more for C-Leg than the mechanically controlled prosthesis. The study population showed a preference for the C-Leg as compared to mechanical prosthesis. Quality of Life In the study done by Kahle et al.,13(5) the prosthesis evaluation questionnaire was used to measure subjective prosthesis function and prosthesis-related quality of life. Most subjects preferred the C-Leg. Cognitive Performance Cognitive performance is the evaluation of the attention required while walking with the knee prosthesis. In a study by Williams et al.,19 objective cognitive performance and perception of cognitive burden was compared while using the Otto Bock C-Leg and the Ossur Mauch SNS. No significant difference in objective cognitive performance was demonstrated. However, the participants reported that the walking required less attention while wearing the C-Leg than while wearing the Mauch. A study conducted by Heller et al.,20 however, found no discrepancies in the automation index between the two devices, the total sway of the conventional prosthesis was significantly higher, especially for a distracting task more than a simple task. Confidence The confidence level of the prosthesis user in using the device is also an important parameter in its evaluation. According to the VATAP,12(p3) the potential benefits of the C-Leg include more confidence for the patient with the perception that activities like sports is possible for him or her. Body Image The body image of a prosthesis user improves with improved gait and confidence. The relevance of psychosocial considerations in selecting prosthetic knee technologies were put forward by Swanson et al.21 after a study on function and body image levels using the C-Leg. With improved activity levels, the participants' self-confidence improved which led to significant body image improvement associated with improved gait. DISCUSSION In conclusion from the above findings, the advantages of the microprocessor-controlled knee prosthesis over the mechanically controlled prosthesis include reduced walking effort, improved gait symmetry, easier negotiation of uneven surfaces like stairs, inclines and rough terrains, lesser risk for stumbles and falls, biomechanical advantages, more natural gait and increased confidence level of the user. However, improper handling of the C-Leg may cause the stance control to malfunction thus leading to increased risk of fall.22 Nevertheless, the C-Leg is considered to be the leading microprocessor-controlled knee device available today.23 Since the introduction of the C-Leg in 1997, it has had a growing international market.24 A study on energy expenditure and obstacle course negotiation by Seymour et al.,25 demonstrating the decrease in effort with the use of C-Leg to complete the obstacle course, kinematic and kinetic comparisons of transfemoral amputee gait by Segal et al.,26 studying the biomechanical advantages of C-Leg, Physiological Cost Index (PCI) and walking performance in individuals with transfemoral prostheses in comparison with healthy controls, a study by Hagberg et al.,27 the study of the efficacy of PCI by Chin et al.,28 a comparative study with user's verdict by Datta et al.29 and the gait efficiency study by Orendurff et al.30 reinforce the above findings. References 1. Medical Museum: The Cultural Body, The History of Prostheses. University of Iowa Hospitals & Clinics Web site. June 5, 2006. Available at: http://www.uihealthcare.com/depts/medmuseum/wallexhibits/body/histofpros/histofpros.html. Accessed August 21, 2008. 2. Marks, LJ, Michael JW. Science, medicine and future: Artificial limbs. BMJ. 2001; 323(7315): 732-735. Available at: http://www.pubmedcentral.nih.gov/articlerender.fcgiartid=1121287. Accessed August 21, 2008. 3. Clinical Policy Bulletin: Lower Limb Prostheses. Aetna Web site. 2008. Available at: http://www.aetna.com/cpb/medical/data/500_599/0578.html. Accessed August 22, 2008. 4. Ossur introduces the new Mauch Knee to amputees. Palscience. 2008. Available at: http://palscience.com/2008/01/30/ossur-introduces-the-new-mauch-knee-to-amputees/. Accessed August 25, 2008. 5. Endolite: History of Prosthetics. Endolite Web site. July 28, 2008. Available at: http://www.blatchford.co.uk/company/history/history.html. Accessed August 21, 2008. 6. Brodtkorb T-H, Henricksson M, Johannesen-Munk K, Thidell F. Cost-effectiveness of C-Leg compared to non-microprocessor-controlled knees: a modelling approach. Archives of Physical Medicine and Rehabilitation. 2008; 89:24-30. 7. Rheo Knee technology in depth. Ossur Web site. 2008. Available at: http://www.ossur.com/pageid=2743 Accessed August 25, 2008. 8. Microprocessor controlled prosthetic knee. Wellmark BlueCross BlueShield Web site. 2008. Available at: http://www.wellmark.com/e_business/provider/medical_policies/policies/c-leg.htm. Accessed August 25, 2008. 9. Johansson JL, Sherrill DM, Riley PO, Bonato P, Herr H. A clinical comparison of variable-damping and mechanically passive prosthetic knee devices. Am J Phys Med Rehabil. 2005; 84:000-000. Available at: http://biomech.media.mit.edu/publications/Johansson2005.pdf. Accessed August 24, 2008. 10. Marks, LJ, Michael JW. Science, medicine and future: Artificial limbs. BMJ. 2001; 323(7315): 732-735. Available at: http://www.pubmedcentral.nih.gov/articlerender.fcgiartid=1121287. Accessed August 21, 2008. 11. Kaufman KR, Levine JA, Brey RH et al. Gait and balance of transfemoral amputees using passive mechanical and microprocessor-controlled prosthetic knees. Gait Posture. 2007;26:489-93. Available at: http://www.ncbi.nlm.nih.gov/pubmed/17869114. Accessed August 25, 2008. 12. VA technology assessment program: Short report - computerized lower limb prostheses. VA HSR&D MDRC. 2000 Available at: http://www.va.gov/vatap/pubs/ta_short_3_00.pdf. Accessed August 24, 2008. 13. Kahle JT, Highsmith MJ, Hubbard SL. Comparison of nonmicroprocessor knee mechanism versus C-Leg on prosthesis evaluation questionnaire, stumbles, falls, walking tests, stair descent and knee preference. JRRD. 2008;45:1-14. Available at: http://www.research.va.gov/programs/JRRD/45_1/kahle.pdf. Accessed August 24, 2008. 14. Datta D, Heller B, Howitt J. A comparative evaluation of oxygen consumption and gait pattern in amputees using Intelligent Prostheses and conventionally damped knee swing-phase control. Clinical Rehabilitation. 2005; 19: 398-403. Available at: http://cre.sagepub.com/cgi/content/abstract/19/4/398. Accessed August 24, 2008. 15. Chin T, Sawamura S, Shiba R et al. Energy expenditure during walking in amputees after disarticulation of the hip. Journal of Bone and Joint Surgery. 2005; 87-B:117-119. Available at: http://www.jbjs.org.uk/cgi/content/abstract/87-B/1/117. Accessed August 25, 2008. 16. Schmalz T, Blumentritt S, Jarasch R. Energy expenditure and biomedical characteristics of lower limb amputee gait: the influence of prosthetic alignment and different prosthetic components. Gait Posture. 2002; 16: 255-63. Available at: http://www.ncbi.nlm.nih.gov/pubmed/12443950. Accessed August 25, 2008. 17. Perry J, Burnfield JM, Newsam CJ, Conley P. Energy expenditure and gait characteristics of a bilateral amputee walking with C-Leg prosthesis compared with stubby and conventional articulating prosthesis. Arch Phys Med Rehabil. 2004; 85: 1711-7. Available at: http://www.ncbi.nlm.nih.gov/pubmed/15468036. Accessed August 25, 2008. 18. Hafner BJ, Willingham LL, Buell NC, Allyn KJ, Smith DG. Evaluation of function, performance, and preference as transfemoral amputees transition from mechanical to microprocessor control of the prosthetic knee. Arch Phys Med Rehabil. 2007;88:207-17. Available at: http://www.ncbi.nlm.nih.gov/pubmed/17270519ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DiscoveryPanel.Pubmed_Discovery_RA&linkpos=2&log$=relatedarticles&logdbfrom=pubmed. Accessed August 25, 2008. 19. Williams RM, Turner AP, Orendurff M et al. Does having a computerized prosthetic knee influence cognitive performance during amputee walking Arch Phys Med Rehabil. 2006: 87:989-94. Available at: http://lib.bioinfo.pl/pmid:16813788. Accessed August 25, 2008. 20. Heller BW, Datta D, Howitt J. A pilot study comparing the cognitive demand of walking for transfemoral amputees using the Intelligent Prosthesis with that using conventionally damped knees. Clinical Rehabilitation. 2000; 14:518-522. Available at: http://cre.sagepub.com/cgi/content/abstract/14/5/518. Accessed August 25, 2008. 21. Swanson E, Stube J, Edman P. Function and body image levels in individuals with transfemoral amputations using the C-Leg. Journal of Prosthetics & Orthotics. 2005; 17:80-84. Available at: http://www.abledata.com/abledata.cfmpageid=160377&ksectionid=160164&atlitid=179480. Accessed August 25, 2008. 22. The electronic C-Leg knee joint system: instructions for use. Otto Bock Web site. 2002. Available at: http://www.ottobock.ca/products/lower_limb_prosthetics/c-leg_instructions.pdf. Accessed August 25, 2008. 23. Meier MR, Hansen AH, Gard SA. Performance on an obstacle course: Otto Bock C-LegVS. Otto Bock 3R60 VS. Catech SNS. American Academy of Orthotists and Prosthetists. 2005. Available at: http://www.oandp.org/publications/jop/2005/2005-5.asp. Accessed August 25, 2008. 24. Otto Bock microprocessor knees. Otto Bock Web site. 2008. Available at: http://www.ottobockus.com/PRODUCTS/LOWER_LIMB_PROSTHETICS/c-leg2.asp. Accessed August 25, 2008. 25. Seymour R, Engbretson B, Kott K et al. Comparison between the C-Leg (R) microprocessor-controlled prosthetic knee and non-microprocessor-controlled prosthetic knee: a preliminary study of energy expenditure, obstacle course performance and quality of life survey. Prosthet Orthot Int. 2007;31:51-61. Available at: http://lib.bioinfo.pl/pmid:17365885. Accessed August 25, 2008. 26. Segal AD, Orendurff MS, Klute GK. Kinematic and kinetic comparisons of transfemoral amputee gait using C-Leg and Mauch SNS prosthetic knees. J Rehabil Res Dev. 2006; 43: 857-70. Available at: http://www.ncbi.nlm.nih.gov/pubmed/17436172. Accessed August 25, 2008. 27. Hagberg K, Haggstrom E, Branemark R. Physiological Cost Index (PCI) and walking performance in individuals with transfemoral prostheses compared to healthy controls. Disabil Rehabil. 2007;29:643-9. Available at: http://www.level1diet.com/1144836_id. Accessed August 25, 2008. 28. Chin T, Sawamura S, Fujita H et al. The efficacy of physiological cost index (PCI) measurement of a subject walking with an Intelligent Prosthesis. Prosthet Orthot Int. 1999;23:45-9. Available at: http://www.ncbi.nlm.nih.gov/sites/entrezdb=pubmed&uid=10355642&cmd=showdetailview&indexed=google. Accessed August 25, 2008. 29. Datta D, Howitt J. Conventional versus microchip controlled pneumatic swing phase control for transfemoral amputees: user's verdict. Prosthet Orthot Int. 1998;22:129-35. Available at: http://www.ncbi.nlm.nih.gov/pubmed/9747997. Accessed August 25, 2008. 30. Orendurff MS, Segal AD, Klute GK. Gait efficiency using the C-Leg. J Rehabil Res Dev. 43: 239-46. Available at: http://lib.bioinfo.pl/pmid:16847790. Accessed August 25, 2008. Read More