Ossur Scientific E-letter
26 September 2006
Ossur Scientific E-letter Issue #3 2006
Empower Scientific E-letter Issue 3#2006 (September 22nd, 2006) Dear readers, Welcome to the third issue of the Empower Scientific E-letter of 2006. A special welcome to all the new subscribers, it is a pleasure to see the increased interest in scientific news. This E-letter includes seven different scientific papers. The articles cover the subjects of amputation, rehabilitation, prosthetics/biomechanics, orthotics/biomechanics, and quality management. This e-letter also includes a new topic, bionics, which shortly means a fusion of electronics, mechanics and human physiology. Three of the selected papers have been published in 2006, three 2005 and one 2001.
Amputation
Karanikolas M. Monanterag A D. Tsolakis I. Swarm R A. Filos K. Rigorous perioperative analgesia decreases phantom pain frequency and intensity after lower limb amputation. A prospective, randomized, double-blind clinical trial.
Regional Anesthesia and Pain Medicine Volume 31, Issue 5, Supplement 1, September 2006, Page 88 XXV
Phantom pain is a problem for many amputees and can negatively affect their quality of life. Pain before amputation is considered a risk factor for phantom pain. Karanikolas et al. wanted to assess how pre-, peri- and post-operative anaesthesia affected the rate and magnitude of phantom pain.
The study included 35 patients who where divided in five groups with different pain treatments. Group one to four received continuous epidural or intra venous PCA (patient controlled analgesia) and the fifth group received intramuscular and/or oral analgesia. The stump pain was scored by VAS and McGill PRI(R) scores 48 and 24 hours before amputation and four and ten days, one and six months after amputation.
The study group found in all control occasions that the pain scores were lower in patients receiving rigorous analgesia. It was most pronounced in the two groups that received epidural analgesia both peri- and post-operatively in combination with epidural or PCA analgesia pre-operatively.
The authors concluded that optimized peri-operative analgesia significantly decreases phantom pain.
Rehabilitation
Dudek N L. Marks M B. Marshall S C. Chardon J P. Dermatologic conditions associated with use of a lower-extremity prosthesis.
Archives of Physical Medicine and Rehabilitation , Volume 86, Issue 4 , April 2005, Pages 659-663
To document the frequency of residual limb skin problems and also determine associating factors to those problems among users of lower extremity prosthesis Dudej and colleagues studied retrospectively 745 patients in an outpatient clinic with a total of 828 lower extremity amputations. The included subjects used prosthesis for functional activities.
The collected data described the patient’s age, age at time of amputation, sex, reason for amputation, level of amputation, presence and type of co-morbidity, smoking history, employment status, type of walking aid and distance walked. More specific data were recorded regarding the type of prosthetic socket and suspension, the length of time the current prosthesis have been used and finally the presence or absence of skin problem and if present the diagnosis of them.
The study showed, not surprisingly, that dermatologic problems are a frequent complication when using lower extremity prosthesis. Forty percent had at least one skin problem. Independently associational factors, with at least one skin problem was; level of amputation; being employed; type of walking aid and absence of peripheral vascular disease.
Dudej et al. suggest that more active amputees have a higher risk for developing dermatological problems. The authors explained that the more active an amputee is the more likely he/she has been amputated at trans-tibial or lower level; is employed; is using no or simpler walking aid, moreover is not suffering from peripheral vascular disease.
The four most common dermatological condition were ulcer (26,7%) followed by irritation (17.6%), inclusion cyst (15.0) and callus (11.4). All conditions could be related to high activity.
No significant differences could be seen in occurrence of skin problems related to the age of the prosthesis. Further this study could not show if anydifference exist between different suspension systems with regard to skin problems.
Prosthetics/biomechanics
Jonesa S F. Twigga P C. Scallyb A J. Buckleyc J G. The mechanics of landing when stepping down in unilateral lower-limb amputees.
Clinical Biomechanics, Volume 21, Issue 2, February 2006, Pages 184-193
The ability to negotiate stairs is an important factor to be functionally independent. Many unilateral amputees find ascending or descending stairs relatively difficult. Jonesa and colleagues studied the biomechanics of landing in unilateral tibial- and femoral amputees. They also assessed the biomechanical effect of the use of a shank-mounted shock-absorbing device. Understanding the biomechanics of amputees negotiating stairs might help health care professionals determine new and/or improved rehabilitation techniques or prosthetic components.
Five transtibial-amputees, five femoral amputees and eight able bodied performed single steps down to a lower level. The amputees took the leading step with their prosthesis. Trials were repeated in amputees with the shock absorber device active and inactive.
The landings were registered by a motion analysis system and two force platforms and analysed regarding peak limb longitudinal force, maximal limb shortening, lower extremity stiffness, knee joint angular displacement during the initial contact period and limb and ankle angle at the instant of ground-contact.
It was found that amputees landed on a near vertical and straightened leg, unlike the able bodied subjects. In some of the transtibial amputees knee flexion occurred. There was significant greater lower extremity stiffness in transfemoral amputees compared to the other groups. The study group concluded that the, descending strategy for transfemoral amputees is to ensure the ground reaction force vector to be anterior to the knee joint centre to maintain stability. In the transtibial amputees they suggest it is a consequence of the ankle in neutral position and/or a way to minimize the moment required by the knee extensors. Further, the shock absorber had little effect on the mechanics of landing in transtibial amputees, but it affected the transfemoral amputees by bringing a reduction in lower extremity stiffness.
Orthotics /biomechanics
Wang w C. Ledoux W R. Sangeorzan B J. Reinhall P G. A shear and plantar pressure sensor based on fiber-optic bend loss.
Journal of Rehabilitation Research & Development Volume 42 Number 3, May/June 2005 Pages 315-326
It is known that shear stress in combination with pressure is a contributing factor to plantar ulcers. The measurement of stress distribution is difficult, mainly because of the technical and medical issues associated with measuring shear stress. The result is shortage of validated and commercially available shear sensors.
Wang et al presented and investigated a new way to transduce plantar pressure and shear stress with a fiber optic sensor.
A shear sensor prototype was constructed consisting of an array of optical fibers in perpendicular rows and columns separated by elastomeric pads. Deformation of the sensor causes a change in light intensity allowing measurement of both pressure and shear. With one layer of fibers it was possible to measure pressure, but two layers were needed to measure the shear stress applied.
The accuracy of the prototype was tested by creating a map of normal and shear stresses, based on macro bending of known magnitude of pressure and shear stress .It was found that the sensor responded to applied pressure and shear loads with good repeatability. Further no tendencies for material creep were detected.
The technology presented can be the basis for a new sensor design that allows real life measurements of pressure and shear stresses.
Bionics
Navarro X. Krueger T B. Lago N. Micera S. Stieglitz T. Dario P. A critical review of interfaces with the peripheral nervous system for the control of neuroprostheses and hybrid bionic systems.
Nature 442, 164-171(13 July 2006)
Restoring physical functions in disabled patients by connecting the nervous system with electronic robotic prosthesis - developing bionic systems - has been challenging for scientists. Navarro et al have critically reviewed literature and carefully explained available peripheral interfaces, their way from research to clinical use in controlling robotic prostheses.
The non-invasive (surface) electrodes records EMG signals and stimulate muscles. Applications of surface electrodes is for example; TENS, widely used in rehabilitation to activate skeletal muscles or to reduce pain by stimulating afferent nerves. Further they can be used in more sophisticated FES (Functional electrical stimulation) system for correction of paraplegic muscles. Other areas of applications are controlling artificial limbs and computers. Their main advantages are the fact that they are non-invasive and easily adaptable. That is counteracted by disadvantages such as the need for daily placement, frequent calibration, the quality of the signals and the poor reproducibility.
Invasive electrodes are placed directly on the surface of the muscle or in the muscle. Invasive electrical stimulation has been applied to maintain denervated muscles. Epimysial electrodes are suitable in complex motor prostheses that require coordinated stimulation of several muscles e.g. grasping, standing and walking systems for paraplegics. Intramuscular electrodes can be used for both recording and stimulation and they have been used widely in the FES field. It is found that intramuscular electrodes produce reliable, graded and low fatigue able stimulation.
Extraneural electrodes are placed on the nerve and activate selective nerve fascicles providing simultaneous interface with many axons in the nerve. They are used in FES applications, for instance stimulation of the phrenic or vagus nerve for breathing control, foot drop control and relief of neuropathic pain.
Intraneural electrodes are placed inside a peripheral nerve and are in direct contact with the tissue they intend to activate or control. That minimizes disturbing noise, which allows the electrodes to stimulate selected fascicles and small stimulus intensities can be used. Intraneural electrodes are used in experiment in nerve activity, controlling of paralyzed muscles and artificial limbs.
The study group also invented biological, technological and material issues regarding electrode design and injury of tissue. Considering a foreign material is implanted in the body and left there for long time particular requirements have to be fulfilled.
Finally different strategies to use the recorded information from peripheral interfaces and the up to date state of controlling neuroprosthesis and hybrid bionic systems were briefly explored.
Navarro and colleagues concluded that, today, there is no universal best choice for all possible uses of the described interfaces. There are many approaches in the use of electrodes to establish contact with peripheral nerves and control technical devices. The technique must be used carefully according to the capacity of the patient and the neuroprosthesis.
Quality management
Rabin R, de Charro F. EQ-5D: a measure of health status from the EuroQol Group.
Ann Med. 2001 Jul;33(5):337-43
Rabin and de Charro gave the background, described and demonstrated applications for EQ-5D in their article. The EQ-5D was developed by the EuroQol group, consisting of a network of international, multilingual and multidisciplinary researchers. The EQ-5D is a generic measure of health status that provides a simple descriptive profile and a single index value, which was a consequence of the process of shared development and local experimentation. The aim was to provide a standardized, non disease specific tool to describe and evaluate health related quality of life. The requirements:
- “an easy ‘add-on’ to studies using existing instruments
- capable of being disseminated as a postal questionnaire for self completion
- relatively undemanding – taking only few minutes to complete
- relevant to all respondents: healthy or severely ill; at home or in hospital; of all ages
- capable of producing a single index value
- consistent with health states ‘worse than dead’.”
The applications are in clinical or health-economical evaluations and in population health surveys.
The EQ-5D consists of two parts. One is a descriptive system that gives the respondent the possibility to classify the health regarding: mobility; self-care; usual activities; pain/discomfort and anxiety/depression. The five dimensions are divided into three levels; no problem; some/moderate problems and extreme problems. The result will be a five digit index number that describes the health status of the respondent. The other part is a visual analogue scale (VAS) where the respondent assess their health status by marking a 0 to 100 scale (0=worst imaginable health state and 100=best imaginable health state).
The EQ-5D has been used and is used in many and different ways, for example to observe the health of certain patient groups at the moment or over time, to monitor the seriousness of conditions at different moments in time, to provide evidence of given treatment, to obtain economical studies and to set level of population health status.
Kind P. Hardman G. Leese B. Measuring health status: information for primary care decision making.
Health Policy Volume 71, Issue 3 , March 2005, Pages 303-313
When treating a patient it is essential to know if the patient actually benefit from the treatment. An accurate measurement tool is needed to find that out.
To explore the benefits of the EQ-5D to measure health status over time Kind et al performed a study where 1942 patients at a general practitioner surgery (GP) were included. When visiting the GP the patients were given the EQ-5D questionnaire and one year later a new questionnaire was sent to the patient. In addition diagnosis and treatment was recorded during the visit at the GP.
By measuring health by EQ-5D it is possible to identify variations within a patient population, compare patient data with normal population levels and to observe changes in health by diagnostic subgroups. Providers of care can also compare performance with each other. Further the quantified health status gives information to decision makers at all levels to make judgements about the most efficient way of using resources.
The study showed that EQ-5D could be utilized to identify patients with specific health problems and to better target health resources.
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Empower Health Care Solutions wish you all the best and is looking forward to providing you with more interesting scientific news in November 2006!
Best regards,
Louise Klevbo
- EmpowerELetter2006Q3.pdf (52kb)
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