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[295] COMPARISON OF SEMI-SYNTHETIC AND AUTOLOGOUS CONNECTIVE TISSUE GRAFTS: A PILOT STUDY
Eric E. Sabelman, PhD; William C. Lineaweaver, MD;
Kenneth C.W. Hui, MD; Feng Zhang, MD; Paula Koran, BS;
Nicole Diep, BS; Min Hu, MD, PhD; Derek Timmermann
Rehabilitation R&D Center, VA Palo Alto Health Care
System, Palo Alto, CA 94304; Dept. of Functional
Restoration, Stanford University Medical School, Stanford CA
94305.
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Pilot Project #B1839-PA); Plastic Surgery Education
Foundation, Arlington Heights, IL 60005)
PURPOSE--Chronic pressure sores are now treated by reconstructive surgery, using a musculocutaneous flap. If this fails and the ulcer recurs, as is frequently the case when causative compression of soft tissue against a bony prominence cannot be avoided, there may be no remaining donor site for a flap or graft.
METHODOLOGY--A tissue-engineered graft for repair of the deep or recurring ulcer is constructed of natural and synthetic biomaterials seeded with autologous connective tissue and fat cells, nourished either from an external fluid loop through artificial capillaries, or by a microsurgically relocated arteriovenous loop. The synthetic capillary network is a branching mesh of permeable tubes, connected either to vessels at a distance from the injury, or to a supply of culture medium. The latter takes the place of the blood supply until replaced by it; it also provides a means for infusing antibiotics to combat infection. The matrix that best mimics mechanical and geometric properties of intact tissue is an interdigitated composite of collagen and hyaluronic acid (HyA), with the collagen cross-linked using ultraviolet light to avoid toxic chemicals.
PROGRESS--A 1-yr pilot project demonstrated cell compatibility of collagen/hyaluronic acid grafts in vitro. These composite materials were tested for creep compliance and tensile relaxation properties. A sub-project now underway involves testing capability of these grafts to resist bacterial and fungal infections common in pressure sores. A second pilot project to perform microsurgical revascularization of semi-artificial grafts in rats includes an effort to develop a better small animal model for pressure sores.
Three physical forms of semi-synthetic graft have been created: homogeneous dispersions of random-geometry HyA particles less than 100 µm in diameter; continuous-strand HyA mats or felts; and loosely packed HyA beads 0.5-1.0 mm in diameter. These are processed into porous discs 35-60 mm in diameter and 2-5 mm thick. Methods for controlling swelling and solubility of the HyA component have been adapted from the literature. Samples of a modified Type I collagen have been provided by Nova-Gen Inc. (Fremont, CA) in addition to purchased bovine collagen and in-house prepared rat-tail collagen.
Preliminary implantations in rats were completed, using a subcutaneous abdominal site. Inflammation was minimal, with rapid capillary outgrowth from the arteriovenous loop within 2 wk and preservation of the HyA component for 8 wk. As predicted from in vitro experiments, migrating cells enveloped individual HyA beads or strands, and did not form a fibrous capsule around the entire implant. The abdominal site did not provide a wound margin suitable for testing integration. Alternate sites that would better emulate the clinical pressure sore include latissimus dorsi and rectus abdominus muscle excision wounds, with the latter requiring less extensive mobilization of the saphenous vein to create the arteriovenous loop.
FUTURE PLANS--A larger scale animal implantation experiment will show that restoration of tissue volume and vascular supply can be reliably replicated; this will be followed by a proposal for a limited clinical trial. Because the costs and level of surgical skill are anticipated to be lower than reconstructive microsurgery, we expect this type of graft to occupy a place in the therapeutic armamentarium midway between surgery and conservative debridement followed by semiocclusive dressings.
[296] PREVENTION OF RECURRENT PRESSURE ULCERS AFTER MYOCUTANEOUS FLAP
Sally Holmes, MD; Janusz Markowski, MD; Kathleen Pace
Murphy, PhD; Susan L. Garber, MA, OTR; Jeffrey D. Friedman,
MD; Diana Rintala, PhD; Gladys P. Rodriguez PhD
Spinal Cord Injury Service (128), VA Houston Medical
Center, Houston, TX 77030, Baylor College of Medicine,
Houston, TX 77030: telephone: 713-794-7128, fax: 713 794
7865: email: holmes.sally_a@houston.va.gov
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B2082-RA)
PURPOSE--The purpose of this study is to evaluate the efficacy of individualized educational interventions with structured long-term follow-up for the prevention or early detection and treatment of recurrent pressure ulcers after surgical management in persons with spinal cord injury (SCI). Included are frequent assessments of the skin care treatment program, pressure ulcer knowledge retained and behaviors practiced, assessment of equipment, assessment of psychosocial status, and the monitoring of urinary collagen metabolites. As physiologic and/or psychosocial risk factors for recurrence of pressure ulcers are identified, the information will be used to individualize the educational program and the assessment and treatment plan to prevent recurrence of surgically managed pressure ulcers in the SCI population. The primary goal of this study is to decrease the recurrence of pressure ulcers in persons with SCI after surgical management. Long-term goals include decreasing the number of hospitalizations, lengths of hospital stay, and medical costs as well as increasing quality of life for these individuals after surgical management of pressure ulcers.
METHODOLOGY--Enhanced instruction of clients and professional multidisciplinary follow-up are the independent variables of this study. Based on the Agency for Health Care Policy and Research (AHCPR) pressure ulcer guidelines, our educational program incorporated the following components: prevention, assessment of tissue damage, and monitoring of outcomes in covering the etiology and risk factors for development of pressure ulcers; the principles of wound healing and nutritional support; an individualized program of skin care; and the selection of support surfaces and equipment. Furthermore, there is a mechanism for accurate documentation and monitoring of education and treatment interventions. Subjects are randomized into one of three groups. The educational intervention is applied to subjects in Group 1. In addition to follow-up by physicians and routinely scheduled Spinal Cord Injury Outpatient Clinic visits, persons in Group 1 receive monthly telephone calls from either an occupational therapist or nurse to assess skin condition, pressure ulcer prevention behaviors practiced, and psychosocial status. Individualized education, equipment, and psychosocial needs are also addressed. Group 2 receives routine pressure ulcer education, no monthly phone contact with either the occupational therapist or registered nurse, and sends a monthly urine sample. Group 3 receives routine pressure ulcer education, no monthly contact, and no monthly urine samples. Subjects in both Groups 1 and 2 send monthly urine samples throughout the duration of the study for the purpose of determining collagen metabolite markers that may be predictive of skin breakdown occurrence. Collagen is the principal protein of the skin matrix, and it is responsible for the great tensile strength of the skin.
PROGRESS--This is the first year of this study. Preliminary results demonstrate no recurrence of pressure ulcers in those in Groups 1 or 3. Group 2 subjects have had a 40 percent recurrence pressure ulcer rate.
FUTURE PLANS--In addition to studying recurrence of surgically managed pressure ulcers in the SCI population, three additional groups will be studied: persons receiving split thickness skin grafts to surgically manage pressure ulcers, those whose pressure ulcers are debrided without surgical closure, and those with SCI whose ulcers are conservatively managed.
[297] USE OF TRETINOIN TO PREVENT PRESSURE ULCERS IN SPINAL CORD INJURY PATIENTS
Janusz Markowski, MD; Gladys P. Rodriguez, PhD
Spinal Cord Injury Service, VA Houston Medical Center,
Houston, TX 77030; Baylor College of Medicine, Houston, TX
77030
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #B688-2RA)
PURPOSE--We seek to determine, through amino acid assays and collagen typing determinations on biopsies taken before and after treatment, whether skin collagen structure has been sufficiently improved to expect that the risk of developing pressure ulcers has been diminished in the treated area.
We also want to determine whether the efficacy of the treatment depends on time since injury or age of the subject by using statistical regression analysis on the data from the amino acid and collagen typing determinations.
METHODOLOGY--This is a controlled, prospective, randomized study. The protocol has been approved by the Institutional Review Board for Human Subjects.
After obtaining informed consent, a 4 mm punch biopsy will be obtained from the sacral area. The biopsy will be assayed for content of the four amino acids characteristic of collagen (hydroxyproline, proline, hydroxylysine, and lysine), and the ratio of collagen Type I to collagen Type III will be determined. The amino acids will be assayed by HPLC chromatography using methods developed by Dr Rodriguez and H. Garza. The collagen typing will be done using gel electrophoresis.
The subject population will be recruited from the VA Medical Center in Houston or attending the Spinal Cord Injury Clinic and consist of 40 male, traumatic spinal cord injury (SCI) subjects between 20 and 55 years of age who have had at least one pressure ulcer previously. Additional inclusion criteria: physiologically complete, nonprogressive SCI and normal liver function. Exclusion criteria: any metabolic disease affecting protein metabolism, presence of other neurological disorder besides SCI, or cauda equina injuries.
Twenty of the subjects will be provided with the tretinoin cream and will be shown how to apply to the skin area at risk. They will apply the cream daily for 1 year. The other 20 subjects will be given a placebo cream. The subjects and the investigators will be blinded to the treatment. The main outcome measure is an improved skin collagen biosynthesis as determined by increased amino acid content and increased content of collagen Type I.
PROGRESS--All preliminary work setting up the assay methods has been completed. Needed supplies have been obtained and questionnaires developed. Ten subjects have been recruited. We do not have any results yet. We will do the assays in batches for increased efficiency.
SIGNIFICANCE--If this study demonstrates that our hypothesis (applying tretinoin cream to the skin will improve collagen biosynthesis) is correct, it will significantly impact on the cost of treating SCI subjects by reducing the number of hospitalizations. Pressure ulcers are a very costly sequelae of SCI. Reducing the incidence of pressure ulcers in the SCI population will also improve the quality of life of the subjects and might make it possible for more of them to be active participants in community life.
[298] THE USE OF GROWTH FACTORS IN PRESSURE ULCER HEALING: CLINICAL TRIALS
Dale S. Feldman, PhD
University of Alabama at Birmingham, Department of
Biomedical Engineering, Birmingham, AL 35294; email:
dfeldman@eng.uab.edu
Sponsor: National Institute on Disability and Rehabilitation Research, U.S. Dept. of Education, Washington, DC 20202
PURPOSE--Optimizing active treatment protocols for pressure ulcers requires speeding up the rate of regenerative healing in order to reduce both the likelihood and impact of other secondary complications. This project was designed to examine the use of fibrin matrices that serve as a drug delivery system for an angiogenic factor (FGF-1) as well as a regenerative scaffold. In the past we have worked on the development of biodegradable fibrin matrix for delivery of FGF-1 and on the development of a porous fibrin matrix; now we are working to evaluate clinically the pressure ulcer healing efficacy of the fibrin matrix with FGF-1.
METHODOLOGY--Clinical trials will be conducted with two treatment groups of 10 patients each. Group 1 will receive the standard clinical treatment of saline-soaked dressings and Group 2 will receive a biodegradable fibrin matrix with FGF-1 applied to the surface of the wound.
PROGRESS--It was found that the fibrin and the FGF-1 act synergistically to enhance the healing response. The FGF-1 apparently needs a matrix for the cells and blood vessels to grow into, and the fibrin matrix does not stimulate the angiogenic and healing response as well without FGF-1 incorporation.
For the porous system, which was made by adding polyethylene glycol (PEG) beads (100-200 µm) into the fibrinogen during the formation of the fibrin matrix, further optimization is needed prior to clinical testing. The current system did not give a better response in open wounds, and, in a related study with meshed skin grafts, the porous system was less effective than the nonporous, both due to its lower adhesive strength and the residence time of the PEG.
In preparation for clinical studies, effort has concentrated on development of the clinical protocol, development of clinical assessment tools, obtaining IRB approval, and obtaining FDA approval. For the assessment techniques, three aspects of pressure ulcer healing will be assessed: healing rate, tissue health, and overall clinical impression. For healing rate, the epithelialization rate, contraction rate, and tissue fill rate independent of wound size will be assessed. For tissue health, a scanning laser doppler will be used to assess the blood flow of the entire wound.
IRB approval has been obtained for two studies: 1) Assessment of control patients who receive the standard pressure ulcer clinic protocols and 2) Evaluation of a pressure ulcer patient with or without fibrin. The clinical study is currently waiting on an IND for FGF-1. Based on requirements outlined by the FDA, the protocol has been modified and the project is on hold until certain GMP requirements are met.
FUTURE PLANS--Over the next few months the emphasis will be on satisfying the FDA requirements, modifying the clinical protocol, and resubmitting to the IRB. One aspect of the FDA's ruling is that the double blind part of the study was lost. If the control group can be made to appear like the treatment, a double blind study is still possible. This however will require drawing plasma from control patients, which will not be used, applying an innocuous substance that looks like the fibrin/FGF, and requiring the control patients to have the same extra clinic visits. Additionally, efforts will continue to further optimize the porous fibrin matrix.
[299] CHARACTERISTICS OF GENITAL SKIN FLORA IN PERSONS WITH SCI AND THEIR EFFECT ON DEVELOPMENT OF URINARY TRACT INFECTION
Ken B. Waites, MD
University of Alabama at Birmingham, Department of
Pathology, Birmingham, AL 35233; email:
waites@wp.path.uab.edu
Sponsor: National Institute on Disability and Rehabilitation Research, U.S. Dept. of Education, Washington, DC 20202
PURPOSE--The nature of changes occurring in microbial ecology of the skin and urinary tract after SCI that result in establishment of diverse, antibiotic-resistant flora are complex and poorly defined. Increased understanding of these changes may lead to ways of preventing or eliminating skin colonization by urinary pathogens following SCI, and ultimately to reduced occurrence of complications resulting from UTI.
This study will determine whether there is a significant difference in skin colonization by urinary pathogens in those persons with SCI who retain normal bacterial flora of the genital skin long after injury in comparison to those who have chronic or recurrent bacteriuria. Whether the nature and degree of surface colonization and development of bacteriuria are affected by bladder management method will also be assessed.
The study will also evaluate the natural history of skin colonization in hospitalized persons with SCI, and determine whether and how administration of systemic antibiotics affects skin colonization and development of bacteriuria, by determining the relationships among urethral and perineal bacterial flora, bladder management method and bacteriuria in males with long-standing SCI, as well as the effect of systemic antibiotics on bacterial flora of the urethra and perineum in men with SCI currently hospitalized and undergoing treatment for UTI.
This study differs from prior investigations in that it includes persons injured many years ago, evaluates larger numbers of persons using different bladder management methods, and includes quantitative microbiologic procedures sufficient to detect all pertinent bacterial species and determine antibiotic susceptibility patterns.
METHODOLOGY--A cross-sectional study will examine cultures of the perineum and urethra obtained simultaneously with urine cultures and urinalysis on eligible persons who return to the UAB-SCICS clinic for routine annual evaluation. If antibiotics are being taken for any reason, these data are recorded. Also recorded are any positive urine cultures greater than 100,000 colonies/ml since their last annual and for which antibiotics were given. Persons whose urine culture is negative will be cultured again at their next annual evaluation to determine whether the characteristics of skin flora and freedom from bacteriuria persist. Only men are being included in this investigation because of the nature of the study.
The data analysis will compare the percentage of persons with each degree of bacteriuria by the method of bladder management. Next the percentage of persons with each type of bladder management who have abnormal skin flora will be compared. The results of the urethral, perineal, and urine cultures will then be used to determine whether persons with negative urine cultures are less likely to have pathogenic bacteria on the skin.
For those persons who have negative urine cultures initially, the percentage who remain negative at the next annual evaluation will be compared for each type of bladder management.
A prospective follow-up study will be performed on hospitalized persons with SCI who develop UTI requiring treatment. Urethral and perineal cultures will be obtained just before initiation of systemic antibiotic treatment, during treatment, and 7 days after treatment. This will allow determination of the effect of systemic antibiotics on skin flora.
PROGRESS--The first patient was enrolled March 1997. We have developed a syllabus and data collection instruments, finalized project entry criteria, and trained a data collector. To date, 14 patients have been enrolled in the study, none of whom experienced any adverse effects.
[300] IMPROVING TISSUE VIABILITY OF PARALYZED MUSCLE USING NEUROMUSCULAR ELECTRICAL STIMULATION
Ronald J. Triolo, PhD; John A. Chae, MD; Kath
Bogie
Cleveland FES Center, Case Western Reserve University,
Cleveland OH 44106; Department of Rehabilitation Medicine,
Metro Health Medical Center, Cleveland OH; email:
rxt24@po.cwru.edu
Sponsor: Spinal Cord Research Foundation/Paralyzed Veterans of America
PURPOSE--Pressure sores are a major secondary complication of spinal cord injury (SCI). They are extremely expensive to treat and often require long periods of bedrest or surgery for successful healing. The purpose of this study is to investigate new techniques for addressing the underlying causes of pressure sores. Neuromuscular electrical stimulation (NMES) can change the characteristics of paralyzed muscles to improve their long-term response to loading, especially while seated in a wheelchair. The objectives of this study are therefore two-fold. First, it will determine the effects of exercise with electrical stimulation on the tissue viability of the skin and underlying muscle most susceptible to pressure sores. Second, it will determine the efficacy of using electrical stimulation to alter the pressure distribution under the buttocks dynamically while sitting.
METHODOLOGY--Five individuals with histories of chronic and recurrent pressure sores will be enrolled in the study. Subjects must be pressure sore free at the time of participation. Since the primary site for pressure sores is the buttock region, NMES will be applied bilaterally to the gluteal muscles. Chronically indwelling intramuscular electrodes with percutaneous leads developed at Case Western Reserve University and the Cleveland VA Medical Center will be used with an externally programmable stimulator. Following implantation, a baseline period without stimulation will yield control data for comparison to the post-treatment phases. Subjects then undergo an intensive exercise program with NMES, during which time progressive changes in muscle bulk and blood flow are monitored using computerized tomography (CT) scans and transcutaneous oxygen measurement. These assessments are indicative of the health, or viability, of the skin and muscle and will gage the effects of exercise alone on pressure sore formation. Changes in weight distribution both over the long-term (due to alterations in the intrinsic muscle properties) and over the short-term (due to active muscle contractions) will be assessed using interface pressure measurements. After reconditioning with NMES, seated pressure distributions will be recorded during slowly varying weight shifts produced by stimulated contraction of the gluteal muscles. The location and magnitude of high pressure regions will be monitored to determine the effectiveness of dynamic posture shifting. Finally, NMES will be withdrawn so that progressive changes after long-term use of NMES can be monitored.
PROGRESS--Initial testing on three NMES users and several candidates with active pressure sores has been completed to refine the methods and calibrate the assessment equipment. These pilot data indicate that individuals with histories of NMES use exhibited healthier skin and muscle than their counterparts with pressure sores as measured by transcutaneous oxygen values. Preliminary data also indicate that seated pressure distribution can be modified with stimulation of the gluteal muscles. These initial observations support the underlying rationale of the study.
FUTURE PLANS--Two individuals have recently agreed to participate in the investigation. Electrode implantation is scheduled for the last quarter 1997. Recruiting for additional volunteers is ongoing. This investigation should provide preliminary data on the therapeutic use of NMES for improving the properties of paralyzed muscle so that the incidence of pressure sores in people with SCI can be reduced. A larger-scale clinical trial will be designed based on the results of this pilot study.
[301] A COMPUTERIZED TECHNIQUE FOR THE ASSESSMENT OF ALTERNATING PRESSURE RELIEF INDEX
Shyam V. S. Rithalia, PhD
Department of Rehabilitation, University of Salford,
Salford M5 4WT (UK); email:
S.Rithalia@rehab.salford.ac.uk
Sponsor: Huntleigh Healthcare plc, Luton (UK); and University College Salford, Salford (UK)
PURPOSE--Decubitus ulcers result in unnecessary expenditure and misery to the patient. An important aspect in their prevention and treatment is the use of appropriate support surfaces, with the object of reducing pressure on the body surface. There is a great deal of interest in finding ways of assessing the possible efficacy of alternating pressure air mattresses (APAMs) and cushions (APACs). The purpose of this project was to develop equipment and software to provide an effective and efficient technique for the assessment of performance criteria of alternating pressure or dynamic support surfaces.
METHODOLOGY--The action of a dynamic support surface is time varying, and therefore it is important that any pressure relieving 'performance' indicator take this factor into account. A computerized system has been developed, which continuously measures the air pressure (AP), interface pressure (IP), and pressure-time cycle characteristics of alternating air mattresses and cushions. The system provides a mouse and keyboard-based, graphically oriented interface. The parameter of interest is pressure relief (PR) defined as a percentage of the cycle. This allows like-for-like comparisons to be made choosing any arbitrary common multiple of the cycle times, such as, 1 hr requires six 10-min cycles or five 12-min cycles. The pressure relief index (PRI) at any given IP threshold is defined as: the length of time (min) IP remains below the chosen threshold in 1 hr, divided by 60.
PROGRESS--Since the project began in early 1994, we have evaluated six APAMs and five APACs. This has given us a better understanding of their advantages and limitations. From the experience gained, we have also implemented several changes to the original computer program, test procedures, and pressure threshold values. In the case of APAMs for PRI calculations as a percentage of the cycle, the IP thresholds are set at 30, 20, and 10 mmHg; and for APACs the thresholds are 60, 45, and 30 mmHg.
RESULTS--Measurements of IP and pressure-time cycle indicated significant differences (p<0.001) between products, showing some devices were only capable of momentarily relieving pressure. Results also indicated that PR was sensitive to the design of the support system, principally air pressure, cycle time, and inflation sequence. The APAMs included in the investigation were capable of providing very low or near zero interface pressures at the sacrum only. However, the corresponding PRI values were better in the case of a mattress that reacted to changes in posture and weight of a subject.
FUTURE PLANS--Performance measurements such as PRI can be extremely useful in looking at differences between APAMs APACs, but only to indicate relative merit with respect to pressure relief. Ultimate performance is only measurable via controlled clinical trial and assessment of the many other important parameters such as comfort, ease of use, cost, maintenance, and long-term reliability. We are continuing the investigation to assess the relationship between PRI, skin tissue perfusion, and clinical outcome. Through such exercises, the true validity of performance measurement tools will become evident.
[302] A STATIC HEEL-CUSHION CONTACT MODEL USING FINITE ELEMENT ANALYSIS
Michael W. Chang, MD, PhD; Len K. Higashi, MS
Department of Rehabilitation Medicine, School of
Medicine and Department of Mechanical Engineering, College
of Engineering, University of Washington, Seattle, WA 98195;
email: mwc@u.washington.edu
Sponsor: The Whitaker Foundation, Rosslyn, VA 22209
PURPOSE--Pressure sores are common clinical problems for debilitated persons and for those with insensate skin. Once developed, pressure sores become very costly and labor-intensive to manage. Prevention is therefore essential, especially in the managed-care era when the health care dollar is tightly regulated. An optimal cushion design is perhaps the most effective means of prevention. However, since many factors govern the effectiveness of the cushion for pressure relief, designing an adequate cushion has been a process of trial-and-error and its outcome has been often unpredictable. Pressure sores are believed to be caused by excessive internal tissue compressive and shear stresses, which cannot be measured clinically. We developed a computer model simulating a static heel-cushion contact using finite element (FE) analysis. With the model, we hope to predict internal tissue stresses that may be used to optimize cushion design.
METHODOLOGY--A mathematical model was developed using FE analysis software, MARC/MENTAT (MARC Analysis Research Corporation, Palo Alto, CA). T1-weighted MR images of a supine unloaded heel were taken in discrete axial slices by placing a surface coil directly beneath the heel. The cross-sectional images were then manually digitized into nodes using NIH Image software. The nodes from the two-dimensional (2-D) axial images were then meshed with eight-node 3-D elements to reconstruct the heel geometry. The calcaneous bone was modeled as a near-rigid, linear, isotropic material (Young's modulus (E)=1700 kPa, Poisson's ratio (p)=0.1). The skin and subcutaneous tissue were modeled both as a linear isotropic (E=15.2 kPa, p=0.49) and as a homogeneous Mooney material (literature-reported) properties. A rigid flat surface (E=2000 kPa, p=0.1) and a firm foam cushion (linear isotropic, E=100 kPa, p=0.1) were both used as contact surfaces. The static loading condition was estimated to represent the total gravitational load of the foot in a supine position, and applied to the finite element model in small increments.
PRELIMINARY RESULTS--Locations of maximum tissue stress were sensitive to soft tissue and cushion material properties. Soft tissue with the linear isotropic model created the maximum compressive stresses near the calcaneous-soft tissue interface. On the other hand, soft tissue with the Mooney model created the maximum compressive stress at near the heel-cushion interface. Presence of foam cushion helped to reduce maximum internal tissue stresses in both cases. All models failed to converge at high static loads. The stress distribution predicted by the Mooney models seemed unlikely.
IMPLICATIONS--Soft tissue models used for simulation are sensitive to internal tissue stress distributions. Clinical measurements of in-vivo tissue properties are essential in developing an accurate soft tissue model.
FUTURE PLANS--We plan to verify tissue strains using MRI for cases involving both heel-rigid surface and heel-cushion contact. Interface pressures will be verified by direct measurement. An optimization scheme will be developed to help design the cushion. In addition, better material properties for the soft tissue needs to be further investigated.
[303] A NEW BIOELECTRIC METHOD FOR EARLY DIAGNOSIS OF DELAYED FRACTURE HEALING
Dennis A. Chakkalakal, PhD; Michael H. McGuire,
MD
VA Medical Center, Omaha, NE 68105; Division of
Orthopaedic Surgery, Creighton University School of
Medicine, Omaha, NE 68131; email:
dchakkal@creighton.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #A623-2RA) and Health Future Foundation,
Creighton University, Omaha NE 68178.
PURPOSE--We seek to develop a procedure of skin-surface measurements of endogenous electricity for the early identification of delayed healing fractures.
METHODOLOGY--This project is designed to test the following hypothesis: normal and delayed healing fractures have distinct electrical signatures, represented by different temporal patterns of skin-surface electrical activity during the first 8 wks after a fracture. The skin-surface voltages are measured over the fracture site within 24 to 48 hrs of initial treatment. These measurements are repeated at 1, 2, 3, 4, 6, 8, 12, 16, and 24 wks after the first measurement. The patient measurements show a change in the voltage magnitude over the course of the study. The data from each patient are statistically analyzed and graphed to see if the voltage pattern revealed follows the voltage patterns seen in a previous canine study. The data are categorized as following either a normal healing (NH) or a delayed healing (DH) model. Patient charts are checked at 4 months after the initial treatment to determine whether the fracture was clinically judged by the orthopaedic surgeon to be a NH or DH fracture. Finally, a correlation between the analyzed data and the clinician's determination is made to determine validity of the hypothesis. Only patients with long bone fractures treated at the Creighton University Medical Center (CUMC) and Omaha VA Medical Center are included in the study. Instrumentation and procedure for bioelectric measurements are as described previously for the canine study, except that miniature EKG-type Ag/AgCl electrodes are used. The relationship of the voltage magnitude and time, compared to the healing time (T), is analyzed to develop indices that represent electrical signatures for NH and DH groups.
PROGRESS--Twenty-six persons have been enrolled so far, all at CUMC. These consist of 18 males and 8 females with an age range of 10 to 91. The distribution according to the type of bone is as follows: 12 femora, 7 tibiae, 2 tibiae/fibulae, 3 humeri, 1 radius, 1 ulna. The protocol is in progress for 8 subjects. Among the 18 other subjects, 8 were available for only 4 visits or fewer. The data collected so far are being analyzed and correlated with the clinician's reports to discern patterns that will allow us to establish universal characteristics of normal healing fractures, if any, regardless of age, sex, type of bone, and type of fracture treatment. In the long term, we expect to distinguish characteristics of NH and DH fractures using the aforementioned variables. We currently have two subjects who have been determined by the clinicians to have DH fractures, which have displayed distinctively different voltage patterns from those of the NH fractures. The number of subjects is still too low to make a definite conclusion on whether or not the hypothesis is valid.
[304] STIMULATION OF BONE HEALING USING BONE-MATRIX-RELATED BIOMATERIALS
Dennis A. Chakkalakal, PhD; Michael H. McGuire, MD;
Kevin L. Garvin, MD
VA Medical Center, Omaha, NE 68105; Division of
Orthopaedic Surgery, Creighton University School of
Medicine, Omaha, NE 68131; Department of Orthopaedic Surgery
and Rehabilitation, University of Nebraska Medical Center,
Omaha, NE 68198; email: dchakkal@creighton.edu
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #A2022-2RA).
PURPOSE--We are evaluating the efficacy of selected biomaterials that are structurally related to bone matrix or one of its macromolecular components, with or without an autologous bone marrow graft, for achieving a complete repair of large bone defects and delayed unions.
METHODOLOGY--The experimental model for normal healing in this research is a 2 mm segmental defect in rat fibula grafted with a 5 mm long demineralized-bone-matrix (DBM) cylinder made from an allogeneic animal. Compared to this model, segmental defects 4 mm or longer grafted with a normal or inactivated DBM cyliner demonstrate varying degrees of delayed healing. Inactivation involves removal of osteoinductive proteins from DBM by a trypsin digestion method, extraction with guanidine HCl, or a combination of the two methods. These defects were treated with the following bone-matrix-related osteoconductive biomaterials: 1) DBM powder of particle size ;le100 µm (DBMP) and DBMP subjected to trypsin digestion (tDBMP) or guanidine HCl extraction (gDBMP); 2) methylcellulose gel (MCG) that is structurally related to collagen; 3) microcrystalline hydroxyapatite (MHA) similar in crystallite sizes to the amorphous fraction of hydroxyapatite in bone; and 4) chitosan, which is structurally related to glycosaminoglycans in the mineral-bound proteoglycans in bone. The treatments will be applied immediately after creating the defect and injected through a predrilled hole in the DBM cylinder at 3 wks after creating the defect. The outcome of treatment is evaluated at 7 wks postsurgery by measuring the bending rigidity of the fibula and the bone mineral content of the repair tissue.
To understand the cellular mechanisms that govern the healing process in the presence of the these biomaterials, the following osteogenic markers are measured at various time points during healing: DNA synthesis, DNA content, and bone-liver-kidney type alkaline phosphatase (ALP) activity (4 days postsurgery); ALP, osteocalcin and collagen types I, II, and X (2 and 5 wks); rigidity and bone mineral content (3 and 5 wks).
PROGRESS--In preliminary studies using 400-425 g
Sprague-Dawley rats, we found that at 11 wks postsurgery,
the mean bending rigidity of fibulae with 4 mm defects
grafted with normal 7 mm DBM cylinders approached the value
for fibulae with 2 mm defects grafted with 5 mm DBM
cylinders (
RESULTS--MHA treatment of fresh 4 mm defects resulted in a 21 percent increase in rigidity over untreated controls at 7 wks postsurgery, but this difference was not statistically significant. Treatments with DBMP, tDBMP, gDBMP, MCG, and chitosan resulted in 14 to 35 percent decrease in rigidity. Injection of chitosan or MHA into the defect 3 wks postsurgery also failed to accelerate bone repair. We hypothesize that there were too few osteogenic cells in the defect to benefit from the osteoconductive properties of these biomaterials. Therefore, the biomaterials, which filled the defect, proved to be barriers to new bone formation.
FUTURE PLANS--The segmental defects in rat fibula will be treated with the combination of each biomaterial and autologous bone marrow, the latter providing a supply of osteogenic cells. Concurrent experiments will involve measurement of osteogenic markers to allow a description of the sequence of cellular events involved in the success and failure of the bone repair process in the presence of osteoconductive biomaterials.
[305] A PROSPECTIVE STUDY OF PLANTAR FOOT PRESSURE AND DIABETIC FOOT ULCER RISK
Edward J. Boyko, MD; Douglas G. Smith, MD; Jessie H.
Ahroni, PhD; ARNP
Seattle VA Medical Center, Seattle, WA 98108;
Departments of Medicine and Orthopedic Surgery, University
of Washington, Seattle, WA 98195; email:
eboyko@u.washington.edu;
dgsmith@u.washington.edu;
ahroni.jessie@seattle.va.gov
Sponsor: Department of Veterans Affairs, VA
Rehabilitation Research and Development Service, Washington,
DC 20420
(Project #A318-5RA)
PURPOSE--We are conducting prospective research designed to identify risk factors for foot ulceration associated with diabetes, examining the independent contributions of foot deformity, macrovascular and microvascular disease, peripheral neuropathy and behavioral factors on the risk of developing a diabetic foot ulcer.
METHODOLOGY--Eligible subjects are enrolled in an internal medicine clinic, and meet the criteria for diabetes mellitus by physician diagnosis or treatment with hypoglycemic medication or insulin. Subjects who participate are assessed for the presence of suspected risk factors grouped into four categories: circulation, neuropathy, foot deformity, and self-care behaviors. Circulation factors include lower extremity Doppler blood pressures, toe blood pressures, transcutaneous oximetry, laser Doppler flowmetry, arterial pulse palpation, venous filling time, and capillary refill time. Neuropathy measures include monofilament testing, bioesthesiometry, deep tendon reflexes, intrinsic muscle atrophy, and cardiovascular reflexes reflecting autonomic neuropathy. Foot deformity measures include clinical examinations, posture and gait assessments, joint ankle measurements, and Harris mat and F-Scan testing for abnormal pressure points. Behavioral factors assessed include type of foot wear, diabetes history and control, foot self-care practices, and visual acuity. All subjects receive yearly repeat examinations and a mailed questionnaire on a quarterly basis asking them to report the occurrence of ulceration. We compare rates of outcome occurrence (incidence) by exposures of interest to determine which particular factors are related to risk of diabetic foot ulcer.
PROGRESS--To date we have enrolled 977 diabetic subjects from the Veterans Affairs Puget Sound Health Care System, Seattle Division, general internal medicine outpatient clinic.
PRELIMINARY RESULTS--We prospectively categorized 730 subjects for their risk of developing diabetic lower extremity complications by two standard risk stratification schemes. We found that one provided no information on the risk of foot complications and subjects categorized as high risk by the other had a risk of these complications only slightly higher than their average pre-test risk. Multivariate logistic regression analysis identified five clinical factors predictive of diabetic foot ulceration and five clinical factors predictive of amputation. When all five factors are present the probability of a foot ulcer is 68 percent and the probability of an amputation is 84 percent.
Results from an analysis predicting diabetic foot ulceration by a tree structured analysis of prospective survival data were presented at the 16th International Diabetes Federation, Helsinki, Finland, 1997. The classification tree incorporating demographic, historical, and examination variables shows that individuals at highest risk for foot ulceration are those insensate to the 5.07 monofilament, who have a history of amputation, and a glycosylated hemoglobin greater than 13.7 percent at entry to the study. Those who were sensate and did not have a self-reported history of peripheral vascular disease were at lowest risk. Subjects who were sensate to the 5.07 monofilament but had a history of peripheral vascular disease were at increased risk, while those who were insensate without a history of amputation had intermediate degrees of risk depending upon the presence of an orthostatic blood pressure decrease greater than 31 mmHg, the presence of hallux limitus, and poor vision.
FUTURE PLANS/IMPLICATIONS--We continue this prospective cohort study of subjects with diabetes, being followed prospectively for development of a full-thickness cutaneous foot ulcer. Extended follow-up will allow us to identify risk factors for diabetic foot ulceration. The findings to date related to risk factors for foot ulceration should be viewed as preliminary. It appears that plantar pressure, sensory and autonomic neuropathy, and skin oxygenation will be important in the pathogenesis of diabetic foot ulceration. Final analysis will provide additional information concerning risk factors for diabetic foot ulcer and potential means for prevention.
[306] PROBLEM-SOLVING SKILLS TRAINING IN THE TREATMENT OF PRESSURE ULCERS
Timothy R. Elliott, PhD
University of Alabama at Birmingham, Spain
Rehabilitation Center, Birmingham, AL 35233; email:
elliott@sun.rehabm.uab.edu
Sponsor: National Institute on Disability and Rehabilitation Research, U.S. Department of Education, Washington, DC 20202
PURPOSE--Pressure ulcers are a largely preventable secondary complication following SCI. Prevention requires appropriate behavior on the part of the individual and/or caregiver, namely the use of appropriate seating, proper transfer techniques, frequent pressure relief maneuvers, and the like. Despite extensive education of persons with SCI, centers treating them see some of them return with pressure ulcers that require surgery or prolonged bedrest in the hospital. Unique behavioral interventions that have promise for improving compliance, and therefore the prevention of repeat ulcers, are badly needed. Prior work has demonstrated that problem-solving skills can be learned, retained, and applied in everyday situations. The focus of this project is to evaluate the efficacy of problem-solving skills training for the prevention of skin rebreakdown in persons with SCI who are hospitalized following pressure ulcer surgery or who are on prolonged bedrest for pressure ulcer healing.
In this study we propose to test the effectiveness of a problem-solving skills training intervention for pressure ulcer prevention in terms of the following criterion measures: the degree of self-perceived responsibility for health care and maintenance; the degree of psychosocial impairment secondary to disability; general problem-solving skills; demonstrated ability to solve problems specific to skin care and maintenance; demonstrated compliance with pressure relief maneuvers; and the prevalence of skin rebreakdown following discharge. We shall also develop and disseminate materials documenting the effectiveness of this intervention and methods for implementation in other agencies by a variety of professionals.
METHODOLOGY--Potential participants in this study will be randomly assigned to either a problem-solving skills training group (training) or a no-treatment group (control). Randomization will be stratified by neurologic level of injury (paraplegia/tetraplegia) to ensure comparability of the two groups. After randomization, those who consent to participate and are assigned to training will be administered an initial battery of measures prior to intervention. They will complete the initial battery again after intervention to assess possible changes. Those assigned to control will be given the pretest battery and then administered the posttest battery 2 wks later. Both groups will be further evaluated at 6 wks postdischarge and during their next annual follow-up visit.
PROGRESS--Thirteen training and 28 control subjects have completed the initial battery. Of those, 11 training and 22 controls completed the 10-day follow-up; 6 training and 12 control subjects also completed the 6-wk follow-up; and 3 training and 8 controls have also completed the 1 year followup. Two subjects refused to participate; three training subjects are to be reimbursed.
FUTURE PLANS--We had originally anticipated enrollment of 34 controls group and 34 participants in the training group by this time. We have encountered considerable problems with recruitment and retention of participants owing to changes in hospital and department practice that have now limited the number of patients available for recruitment and participation, and to the fact that many patients are indigent and unable to procure reliable transportation back to the outpatient followup appointments.
To improve recruitment and participation we have made arrangements with plastic surgery to meet with patients admitted for skin flap repair and see them following surgery in other hospital units. Secondly, we now offer a $150 stipend to all participants who agree to be in the study. We continue to recruit exclusively for the training group so that we can have comparable numbers for the data analysis.
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Last revised Fri 04/30/1999