Ossur Scientific E-letter

14 March 2008

Ossur Scientific E-letter Issue 1#2008

Ossur Academy Scientific E-letter - Issue 1 # 2008 (February 29th 2008)

Dear readers,

Welcome to the first issue of our Scientific E-letter of 2008.
This E-letter includes nine different scientific papers. The articles cover the subjects of amputation/rehabilitation, prosthetics/biomechanics, orthotics/biomechanics, bionics and quality management.
Three of the selected papers have been published in 2008, five in 2007 and one in 2006.

Enjoy the reading!

 

Amputation/Rehabilitation

Hallock GG.
Preservation of lower extremity amputation length using muscle perforator free flaps.
J Plast Reconstr Aesthet Surg (2008), doi:10.1016/j.bjps.2007. 12.007

In the right circumstances a lower limb amputation can be a reasonable and definitive reconstructive option. When the decision to amputate is made the level of the amputation must be considered so the patient maintains optimal mobility and independence. In addition, the soft tissue covering the stump must have the following features: the ability to absorb shear and direct forces for long term durability, a contour and thickness to fit into a prosthetic application and, if possible, be sensate.

If local soft tissues are inadequate to fulfil these fundamental requirements, consideration of a microsurgical tissue transfer is an option, especially to cover bone and/or to save a major joint.

Hallock has studied the technique of using muscle perforator free flaps on eight patients. He found that muscle perforator free flaps are an alternative to the necessary soft tissue augmentation. Multiple donor site alternatives are available even from the involved lower extremity, to minimize further morbidity. Furthermore he found that the vascular pedicles of this type of flap are long and of good calibre to facilitate reaching an appropriate recipient site. They can be sensate if desired. Muscle function is by definition preserved. The author found that complications are minimal and usually related to the reason for the amputation in the first place.

Sadat U. Chaudhuri A. Hayes P.D. Gaunt M.E. Boyle J.R. Varty K.
Five Day Antibiotic Prophylaxis for Major Lower Limb Amputation
Reduces Wound Infection Rates and the Length of In-hospital Stay
Eur J Vasc Endovasc Surg 35, 75-78 (2008)

A high level of wound infections after major lower limb amputations has been reported. Several contributing factors are known: ischemia, pre-existing limb ulceration and gangrene, patient co-morbidities and wound contamination. Careful selection of the amputation level, optimal surgical techniques and appropriate antibiotic prophylaxis are required to minimize infection rates.

Sadat and colleagues wanted to compare the incidence of wound infections, revision rate and length of hospital stay when treating patients with 24 hour antibiotic prophylaxis versus a 5 days antibiotic prophylaxis.

The study included two groups, each consisting of 40 major lower limb amputations. One group received a short 24-hour course of combined prophylactic antibiotics (flucloxacillin/vancomycin + gentamicin/ciproxin + metronidazole). The other group received a 5-day combined regime using the same antibiotics.

The result showed that the 5-day antibiotic regime led to a significant reduction in wound infection rates (5% vs. 22.5%) and a reduced length of hospital stay (22 vs. 34 days). Revision rates were lower, but did not show statistical significance (2.5% vs. 10%).

The authors concluded that their study supports the use of a prolonged 5-day course of combined antibiotics after major lower limb amputation. This appears to reduce stump infection rates, which leads to shorter in-hospital stays.

Tseng C L. Sambamoorthi U. Helmer D. Tiwari A. Rosen A K. Rajan M. Pogach L.
The association between mental health functioning and nontraumatic lower extremity amputations in veterans with diabetes
General Hospital Psychiatry 29 (2007) 537–546

Lower extremity amputation (LEA) is a catastrophic complication in diabetic individuals. A great deal of the research on risk factors associated with lower limb amputation has focused primarily on foot-specific risk factors (such as ulcers, infections and peripheral neuropathy), glycemic control, lower extremity complications and age, gender, race, education and medical comorbidity.

Tseng and his study group wanted to assess the association between mental health functioning and type of LEAs (major, minor and none) among veterans with diabetes. The study group performed a retrospective study of respondents with diabetes in a veteran health survey. The included subjects were Veterans Health Administration clinic users during the years 1998–2000.

The study showed that of the 114,890 individuals included in the study, there were 450 (3.9‰) major and 431 (3.8 ‰) minor LEAs. Individuals with major and minor LEAs had lower mean mental health scores than those without LEAs. The study group found that a five-point increase in mental health score was associated with a 5% decrease in the risk of major LEAs, no relation was found to minor LEAs.

The authors suggest that foot care programs should assess individuals for mental health functioning and consider it to be a risk factor. Furthermore  they propose that appropriate interventions should be developed to reduce the risk of major amputation.

 

Prosthetics/biomechanics

Traballesi M. Porcacchia P. Averna T. Brunelli S.
Energy cost of walking measurements in subjects with lower limb amputations: A comparison study between floor and treadmill test
Gait & Posture 27 (2008) 70–75

Energy cost measurement is an evaluation method adopted for studying the physiology of physical exercise, which is used to determine the effect of a disability on walking.

Traballesi et al wanted to verify if there was a difference in energy cost of walking (ECW) in lower limb amputees when walking on a treadmill versus a floor.

The study included 24 subjects with unilateral lower limb amputations (16 transfemoral- and 8 transtibial-amputations), caused by vascular diseases. During the tests the subjects walked at a self-selected comfortable speed on the floor and on a treadmill. The energy cost was measured by a portable gas analyser, walking speed was also recorded.

The result showed that the self-selected comfortable speed on the treadmill was significantly lower than that on the floor while the oxygen consumption and steady-state heart rate were the same in the two tests. Therefore, for both transtibial and transfemoral patients, the ECW was greater during walking on the treadmill.

The study group suggests that the reason for lower energy cost during walking on floor could be due to the fact that the patients were able to use their normal walking aids and therefore were more comfortable and performed better.

Out of the result the authors concludes that the floor test may better reflect walking with prostheses and aids in everyday life, in subjects with dysvascular lower limb amputation, using the prosthesis for a short time.

Lee M-Y.  Lin C-F. Soon K-S.
Balance control enhancement using sub-sensory stimulation and visual-auditory biofeedback strategies for amputee subjects
Prosthetics and Orthotics International, Volume 31, Issue 4 December 2007 , pages 342–352

Balance is a critical functional capability that greatly influences the ability to perform activities of daily living.

It is known that sub-sensory electrical or mechanical stimulation and visual-auditory biofeedback can improve the balance control capabilities in the elderly.

Lee et al hypothesized that static balance and gait performance could be improved by providing proprioceptive neuromuscular facilitation using sub-sensory stimulation and visual-auditory biofeedback in amputee subjects. To confirm their hypothesis they developed a computerized foot pressure biofeedback sensory compensation system, using sub-threshold low-level electrical stimulation combined with visual-auditory biofeedback.

The study included seven unilateral transtibial amputees who had used prostheses for over 2 years. The subjects performed multiple single leg quiet standing trials while sub-sensory electrical stimulation was applied at the quadriceps muscle during half of the trials. Static balance performance was assessed by measuring the sway distance and duration of the centre of mass on the second sacral vertebra of the subjects. Furthermore multiple treadmill ambulatory trials with or without visual-auditory biofeedback were performed. Dynamic gait performance was investigated with an instrumented insole to evaluate the temporal responses of foot pressure sensors.

The authors reported that the result showed improvement during single leg quiet standing by applying sub-sensory stimulation. It was also verified that visual-auditory biofeedback during treadmill ambulation improved  performance. The findings suggest that sub-threshold electrical stimulation and visual-auditory biofeedback rehabilitation strategies may be effective in compensating sensory loss and improving static balance and dynamic ambulation performance for amputees.

 

Orthotics /biomechanics

Faes M. van den Akker B. de Lint J.A. Kooloos J.G.M. Hopman M.T.E.
Dynamic Extensor Brace for Lateral Epicondylitis
CLINICAL ORTHOPAEDICS AND RELATED RESEARCH 2006 Number 442, pp. 149–157

Lateral epicondylitis (tennis elbow) is a common, often disabling disorder, caused by overuse or injury and characterized by pain over the lateral epicondyle of the humerus aggravated by wrist extension. Furthermore, patients experience a weakened grip strength and functionality of the arm.

Due to poor results  of current therapies, a new dynamic extensor brace has been developed. This brace is constructed to relieve the hand extensor muscles by allowing the wrist to flex while applying an external wrist extension force on the palm of the hand. This results in a flexion moment that is produced by the flexor muscles while gripping,and is counterbalanced by an external extension moment of the brace, which is normally produced by the extensor muscles. Previous study showed a reduced electromyographic activity of the wrist extensor muscles during hand grip with this type of brace.

Faes and collegues wanted to study the effects of treating Lateral epicondylitis with this brace. They wanted to see  if patients’ complaints  declined with prolonged application of this brace.

63 patients with lateral epicondylitis were randomly assigned to 12 weeks of brace treatment or to no brace treatment. Pain (VAS), pain free grip strength, maximum grip strength and functionality of the arm were assessed at 6, 12, 18 and 24 weeks after starting the treatment.

This level-1-of-evidence study demonstrated with statistical significance that the treatment with the brace reduced pain, improved functionality of the arm and improved the pain free grip strength. In comparison with the group not receiving a brace the beneficial effects in the group treated with the dynamic extensor brace, observed after 12 weeks, were significantly different. Further it was found that the beneficial effects were sustained for another 12 weeks.

The authors conclude that the result of this study strongly supports the treatment of lateral epicondylitis with the dynamic extensor brace.

Bulthuis G.J. Veldhuizen A.G. Nijenbanning G.
Clinical effect of continuous corrective force delivery in the non-operative treatment of idiopathic scoliosis: a prospective cohort study of the triac-brace
Eur Spine J 2007 DOI 10.1007/s00586-007-0513-9

External devices have throughout history been used to correct deformities and immobilize the spine. Designs have changed over the years, but most modifications have solely focused on improved efficacy and not acknowledged the importance of physical appearance, especially for teenagers. A new brace was developed to meet the criteria of appearance and comfort in addition to correcting the scoliosis.

The TriaC brace works by reversing the transversal force pattern with constant, externally applied forces. In the frontal plane the force system used in the TriaC brace is similar to the force system of conventional braces. However, in the sagittal plane the force system acts only on the thoracic region. This results in upper trunk flexibility without affecting the corrective forces during body motion. The brace does not limit the normal body motions of the patient and therefore gives an increased comfort level to the patient.

Bulthuis and his study group have presented the results of a prospective cohort study of the treatment with this new orthotic device. They wanted to determine if the TriaC brace was effective in preventing curve progression in skeletally immature idiopathic scoliotic patients with a high risk of curve progression.

The patients were included or excluded according to following criteria:
Inclusion criteria

• Idiopathic scoliosis with a Cobb-angle between 20° and 40°
• Skeletally immature
• Risser 0–1 status
• Pre-menarche
• Post-menarche\1 year
• Primary thoracic apex between the 7th and 11th thoracic vertebra
• Primary lumbar apex between the 2nd and 5th lumbar vertebra
• Flexible spinal column as evidenced by at least 40% correction on bending films

Exclusion criteria

• Idiopathic scoliosis<20° and>40°
• Other types of scoliosis
• Skeletal age [Risser]
• Rigid curves
• Thoraco-lumbar curves with an apex at the 12th thoracic and the 1st
• lumbar vertebra
• Patients with a systemic disease which could influence the study

The study included 63 patients, 57 girls and 6 boys. The mean age of the patients at the start of treatment was 11.3 ± 3.1 years. The treatment was complete when the patients had reached Risser 4 with a mean age of 15.6 ± 1.1 years, all patients were followed up to skeletal maturity. There were seven patients (11%) with a single curve and 56 (89%) with a double curve. All patients were assessed by radiographic analysis using a standardized protocol. One single observer collected all measurements.

The study demonstrated a successful result in 76% of the patients treated with the TriaC brace. Further, when comparing their data with similar studies, it was established that the TriaC brace significantly changes the predicted natural history. The study demonstrates that treatment with the TriaC brace reduces the scoliosis, and that the achieved correction is maintained in some degree after skeletal maturity is reached and bracing is terminated. Further progression of the Cobb angle in idiopathic scoliosis was also prevented. The new brace does not differ from the conventional braces as far as maintaining the deformity is concerned. In addition the new dynamic brace offers more comfort to the patient and a better cosmetic appearance.

Bionics

Davoodi R. Urata C. Hauschild M. Khachani M. Loeb G E.
Model-Based Development of Neural Prostheses for Movement
Biomedical Engineering, IEEE Transactions on Volume 54,  Issue 11,  Nov. 2007 Page(s):1909 - 1918

Controllers in functional electrical stimulation (FES) systems for paralyzed limbs and in motorized prosthetic limbs for amputees are complex because they must solve problems of coordination similar to those normally handled by the central nervous system. These controllers must coordinate the actions of actuators such as muscles to move the limb with kinematically and mechanically interacting segments. Furthermore, these movements must be performed in the face of external disturbances and in coordination with residual voluntary movements so that man and machine can operate in harmony. Design of controllers with such sophistication is obviously nontrivial.

Trial-and-error approaches and subjective intuition have been applied to the design and clinical fitting of simple systems with limited functionality. These approaches are time consuming, difficult to apply in larger scale, and not applicable to limbs under development with more human like motion and actuation.

Davoodi and his colleagues have found that the field of neural prosthetics needs more systematic methods, including tools that allow users to develop accurate models of neural prostheses and simulate their behavior under various conditions before actual manufacturing or clinical application. Such virtual prototyping would provide an efficient and safe test-bed for narrowing the design choices and tuning the control parameters before actual clinical application.

The authors described a software environment, known as musculoskeletal modelling software (MSMS), that they developed to facilitate the construction and modification of accurate mathematical models of paralyzed and prosthetic limbs and simulate their movement under various neural control strategies. With MSMS users can build accurate models of human and prosthetic limbs or a combination of them in the same environment.

Physics-based simulations can then be performed to predict the behaviour of the system under various movement control strategies and external conditions. Accurate simulations including all of the known system parameters and elements can be performed to narrow the choices for the control strategy, optimize the control parameters, and analyze the sensitivity to control and system parameters.

The same models or their simpler versions can be simulated in real-time with the patient-in-the-loop where the patients can evaluate and learn to operate candidate neural prostheses before actually receiving them. As a general framework, MSMS can be used to simulate any neural prosthetic system. The authors reported that this system so far has been used for design and evaluation of FES control systems for reach and grasp and prosthetic control systems for amputees.

Quality management

Franchignoni F. Giordano A. Ferriero G. Muñoz S. Orlandini D. Amoresano A.
Rasch analysis of the Locomotor Capabilities Index-5 in people with lower limb amputation
Prosthetics and Orthotics International, Volume 31, Issue 4 December 2007, pages 394-404

The primary goal of rehabilitation programs for lower extremity amputees is the best possible restoration of mobility and locomotor function. Sound outcome measures of mobility are needed to accurately examine the impact of therapeutic interventions.

Franchignoni and his team wanted to perform a Rasch analysis on the 5-level ordinal scale version of the Locomotor Capabilities Index (LCI-5), in order to investigate rating scale quality and conduct reliability and validity assessments.

Rasch models are mathematical models of how probabilities of response should be in order to act in accordance with fundamental requirements of measurement. Depending on the string of responses provided by a particular sample of subjects on a particular sample of items, the Rasch model estimates goodness-of-fit of the real data to the modelled data. If the differences between observed and expected scores are not too large, it is said that ‘the data fit the model´and this is seen as equivalent to a test of the theoretical construct validity and adequacy of the scale.

The study commenced with 123 people who underwent lower extremity amputation and responded to a questionnaire, that included the LCI-5. This was followed by a Rasch analysis and expert review of the questionnaire.

The authors concluded that the Rasch analysis provided the rationale for improving the measurement qualities of the LCI-5, refining its rating scale, identifying those items most useful for measuring the intended construct and showing that one can place high confidence in the consistency of both the person-ability and item-difficulty estimates obtained (reliability).

Ossur Academy is looking forward to providing you with more interesting scientific news in May!

Thank you for reading,
Ossur Academy.

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