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PubMed2003

Can loaded interface characteristics influence strain distributions in muscle adjacent to bony prominences?

Pressure distributions at the interface between skin and supporting tissues are used in design of supporting surfaces like beds, wheel chairs, prostheses and in sales brochures to support commercial products. The reasoning behind this is, that equal pressure distributions in the absence of high pressure gradients is assumed to minimise the risk of developing pressure sores. Notwithstanding the difficulty in performing reproducible and accurate pressure measurements, the question arises if the interface pressure distribution is representative of the internal mechanical state of the soft tissues involved. The paper describes a study of the mechanical condition of a supported buttock contact, depending on cushion properties, relative properties of tissue layers and friction. Numerical, mechanical simulations of a buttock on a supporting cushion are described. The ischial tuberosity is modelled as a rigid body, whereas the overlying muscle, fat and skin layers are modelled as a non-linear Ogden material. Material parameters and thickness of the fat layer are varied. Coulomb friction between buttock and cushion is modelled with different values of the friction coefficient. Moreover, the thickness and properties of the cushion are varied. High shear strains are found in the muscle near the bony prominence and the fat layer near the symmetry line. The performed parameter variations lead to large differences in shear strain in the fat layer but relatively small variations in the skeletal muscle. Even with a soft cushion, leading to a high reduction of the interface pressure the deformation of the skeletal muscle near the bone is high enough to form a risk, which is a clear argument that interface pressures alone are not sufficient to evaluate supporting surfaces.

Adipose Tissue↗
PubMed1995

Evaluation of an active seating system for pressure relief.

In the first part of this study, the inflation-pressure and interface-pressure profiles of an active cushion system, the Talley active air bellows cushion, were examined continuously for one complete working cycle using the dynamic pressure monitor. The relationship between the inflation pressure and the interface pressure was explored. A well-defined relationship was found in the areas directly over the air bellows. In the second part of this study, the pressure-relieving characteristics of the active cushion were assessed quantitatively and compared to two types of passive cushions--the Roho high-profile air floatation cushion and the polyurethane (PU) foam cushion. Eight non-disabled subjects were positioned on the active cushion at two inflation-pressure levels--30 mmHg and 60 mmHg, or on the Roho or the PU foam cushions. Interface pressures were recorded using the Oxford pressure monitor. For the active cushion it was shown that the higher the inflation pressure was, the better the pressure-relieving characteristics seemed to be. In general, the pressure-relieving characteristics of the active cushion were not as good as those of the passive cushions being tested. The active cushion could alter the pressures over the ischial tuberosities cyclically but the amount of pressure alternation depended on the relative position of the ischial tuberosities and the air bellows.

Adult↗
PubMed1996

Magnetic resonance imaging examinations of gluteal decubitus ulcers in spinal cord injury patients.

The purpose of our study was to use magnetic resonance imaging (MRI) to determine deep changes in soft tissues and bones underlying decubitus ulcers which occur in spinal cord injury (SCI) patients. By diagnosing these deep changes adjacent to decubitus ulcers, MRI can facilitate proper clinical management and prevent contraindicated surgery. MRI evaluation was performed on 37 male SCI patients for a total of 44 diagnostic studies. The studies were evaluated by the following criteria: 1) the presence of an adjacent fluid collection, 2) bone involvement raising the possibility of osteomyelitis and 3) heterotopic bone formation. Results demonstrated 11 patients (29.7 percent) with fluid collection in the deep soft tissues underlying the decubitus ulcer and eight patients (21.6 percent) with abnormal adjacent bone marrow signal. Four patients (10.8 percent) had heterotopic bone formation near the ulcer. We conclude that MRI is helpful in determining the depth and extent of soft tissue involvement underlying decubitus ulcers including underlying fluid collections, heterotopic bone formation and evidence of adjacent bone marrow edema. This is beneficial in planning proper therapy.

Adult↗
PubMed1975

Effect of training on the use of weight-bearing orthoses.

Weight-bearing orthoses have been disigned with the primary goal of reducing or eliminating weight bearing in skeletal structures. In evaluating various designs and adjustments of these orthoses, we found that the training of the subject in the use of his orthosis was one of the most significant factors in controlling weight bearing. Subjects fitted with instrumented ischial weight-bearing and patellar-tendon-bearing orthoses walked over a force plate which measured forces imparted to the floor. The force data from the orthoses and force plate were computer-processed with single frame, multiple exposure photographic data to provide plots of axial loading in the orthosis and total axial loading imparted to the floor during the duration of the stance phase. The difference between these two forces represents the load carried by the skeletal system. Measurements were made first with subjects who had no specific instructions about the use of their orthoses. The subjects were then instructed how to use their orthoses more efficiently. In all cases, the effect of training produced a 30 to 50 percent increase in loading borne through the orthosis.

Biomechanical Phenomena↗
PubMed1993

Ischiogluteal bursitis in cancer patients: an infrequently recognized cause of pain.

We report eight patients with metastatic malignancy who developed severe back and leg pain caused by ischiogluteal bursitis. Careful evaluation excluded the possibility of bony metastases. Ischiogluteal bursitis is an easily diagnosed condition that can be effectively treated with local injection of corticosteroids. Recognition of this disorder will allow prompt therapy and unnecessary evaluation expenses.

Adrenal Cortex Hormones↗
PubMed1997

The location of the prostatic apex on retrograde urethrography and its relationship to the bottom of the ischial tuberosities.

To determine the proportion of patients undertreated if the inferior border of the prostate field is set at the bottom of the ischial tuberosities, we reviewed the ports of 80 patients with prostate cancer who had retrograde urethrography as part of simulation for radiation therapy. For the 75 evaluable urethrograms, the mean distance from the top of the urethrogram cone to the bottom of ischial tuberosities was 1.38 cm (range, -0.48-2.90 cm). A comparison of the inferior border defined by the bottom of the ischial tuberosities and retrograde urethrography showed that 47 of 75 (62.7%) patients would have been undertreated if a margin of 1.5 cm was employed, and the prostatic apex was thought to be directly above the urethrogram cone. If the apex was thought to be 1 cm above the cone, six of 75 (8.0%) patients would have been undertreated, using a margin of 1.5 cm. Although previously published reports have established that using the bottom of the ischial tuberosities as the inferior border of the prostate field results in 10-45% undertreatment, our findings, when adjusted for the variability of prostatic apex location and margin of normal tissue employed, indicate that only 8% may actually be undertreated.

Aged↗
PubMed1978

The tensor fascia lata musculocutaneous flap.

The tensor fascia lata (TFL) muscle, together with the overlying skin of the anterolateral thigh, makes a reliable musculocutaneous unit. It can be lengthened safely by taking the fascia lata and the skin of the anterolateral mid and lower thigh to within 8 cm of the knee. The skin of the longer flap is supplied by large perforating musculocutaneous arteries, the terminal branches of the vascular pedicle of the muscle. The shorter flap can easily be transposed over the trochanteric area, while the larger flap will cover not only the trochanter but also the ischial and sacral areas. The flap serves equally well as a transposition, island, or free flap. The anatomical and vascular basis of the flap is presented, together with its application in 21 patients. Possible further applications of the flap, including anterior rotation, are discussed.

Fascia↗
PubMed1982

Surgical methods for managing ischial pressure wounds.

Several surgical modalities are available for closing ischial pressure wounds, but while they all aim for a permanently closed and well-padded ischial area, the manner in which this objective is achieved is different for each operation. Each technique has its unique design, transposes variable amounts and quality of soft tissue, and creates different scars and donor defects. These factors, in return, influence to a considerable extent the durability of each operation and, more important, create scars that dictate the nature of the secondary surgery in the all too common event of recurrent ulceration. No tissue is immune to pressure, and therefore there is no one best operation for closing pressure ulcers. This article critically reviews and updates contemporary surgical management and presents an orderly approach to selecting an operation for closing ischial pressure ulcers.

Adult↗
PubMed1988

Coverage of chest wall and pelvic defects with the external oblique musculofasciocutaneous flap.

The external oblique muscle, its fascia, and overlying skin have comprised flaps that have been used successfully in reconstructive surgery of various defects in the past. This flap provides good coverage for lower and upper chest wall defects to the level of the ipsilateral fourth rib. It provides skin of a similar color and texture and of large quantity. The skin of the flap is innervated; thus, sensation can be maintained. The remaining flat abdominal musculature and fascia maintain the integrity of the abdominal wall after transposition. We demonstrate that the external oblique musculofasciocutaneous flap can also be rotated in an inferior direction to close large hemipelvectomy defects in the absence of the usual ipsilateral thigh musculature.

Abdominal Muscles↗
PubMed2001

Split gluteus maximus island flaps for concomitant closure of ischial and sacral pressure sores.

The author presents an innovation in the use of the gluteus maximus musculocutaneous flap that allows one to repair both sacral and ischial pressure sores concomitantly in a paraplegic patient. The musculocutaneous unit is divided into superior and inferior halves, each of which is supplied by their respective gluteal arteries. The "islanded" flaps can be moved in different directions independent of one another to cover both the sacral and ischial regions at the same time. The donor area can be closed primarily. Three patients were operated using this method. The 1-year follow-up of 1 patient is presented.

Debridement↗
PubMed2002

Outcomes for surgical coverage of pressure sores in nonambulatory, nonparaplegic, elderly patients.

Pressure sores are a common complication of long-term institutional care. Surgical coverage of late-stage ulcers in the elderly refractory to conservative therapy remains controversial. The authors reviewed the outcome of 22 predominately nonambulatory, nonparaplegic, elderly patients with coverage of 27 pressure sores. The mean patient age was 59 years (range, 50-82 years). The average follow-up was 6 months (range, 3 months-2 years). There were 11 complications for the 22 patients (50%) and the 27 ulcers (41%). Postoperatively, a well-healed ulcer was present in 19 of 27 patients (70%) at 6 months. Of the 19 reconstructed sacral ulcers, there were 10 complications (53%) and one recurrence at 6 months. Seven trochanteric ulcers were covered with tensor fascia lata flaps without complications or recurrences at the 6-month follow-up. One ischial ulcer was managed using a V-Y hamstring advancement flap, resulting in dehiscence and a subsequent revision. The authors advocate surgical coverage to treat late-stage pressure sores in nonparalyzed elderly persons to reduce the morbidity, mortality, and economic burden of patients with late-stage pressure ulcers. With an increasing geriatric population, prevention and postoperative care are necessary to diminish the incidence, recurrence, and burden of pressure sores.

Aged↗