Journal of Tissue Viability

Calendar of Events

2012-05-01

Deformations, mechanical strains and stresses across the different hierarchical scales in weight-bearing soft tissues

Naama Shoham, Amit Gefen — 2012-04-23

Abstract: Sustained internal tissue loads (deformations, mechanical strains and stresses) which develop during immobile weight-bearing postures such as while in bed or in a chair were identified as a fundamental cause for the onset and progression of pressure ulcers (PUs), particularly of the deep tissue injury (DTI) type. The sustained loading may compromise tissue viability either directly, by geometrically distorting cells, or indirectly, by distorting the vasculature or lymphatic networks or, at the micro-scale, by distorting cellular organelles involved in regulating transport, e.g. the plasma membrane, since transport-control-mechanisms are essential for adequate biological function of cells. In this article we provide a comprehensive, rigorous review of the up-to-date published computational-modeling-work as well as relevant experimental studies concerning tissue deformations, strains and stresses across the different hierarchical scales: tissue-scale [cm], meso-scale [mm] and cell-scale [μm]. Viability of tissues exposed to sustained loading should be investigated in all dimensional scales, from the macro to micro, in order to provide complete understanding of the etiology of PUs and DTIs and in particular, for identifying individuals for whom and conditions at which the susceptibility to these injuries might be greater. Emerging relevant bioengineering methods of computer simulation such as multiscale and multiphysics modeling will undoubtedly contribute to the aetiological research in this field in the near future.

Determining the optimal inner air cell pressure for the effective reduction of interface pressure

2012-04-30

Abstract: Alternating-pressure air mattresses can reduce interface pressure and prevent pressure ulcer development. However, bottoming out sometimes occurs, resulting in an increase in interface pressure. Therefore, optimal settings should be determined based on interface pressures and inner air cell pressures. The purpose of this study was to investigate the most effective inner air cell pressure to reduce interface pressure without causing bottoming out. A new alternating air mattress was used, which comprised three layers: a base layer, fitting (F) layer, and alternating layer. The alternating layer comprises inflated (I) cells and deflating (D) cells. The study participants were 13 healthy volunteers over 18 years of age, each of whom adopted supine position on the mattress. The pressures in the D cells were gradually deflated under different I cell and F layer pressure settings. We measured peak sacral pressure and inner air cell pressure to obtain the bottoming out cut-off values by using receiver-operating-characteristic (ROC) curves. We then investigated the effectiveness of different settings to reduce the peak sacral pressures. A number of test conditions were evaluated. Results indicated that the D cell pressure cut-off points were 1.26 kPa and 1.21 kPa, for phases 1 (F = 4 kPa, I = 4 kPa) and 4 (F = 1 kPa, I = 4 kPa), respectively. These settings significantly reduced the interface pressure (P < 0.001, P = 0.026, respectively). Our results suggest that appropriate configuration of inner air cell pressure could reduce interface pressure without causing bottoming out.

Development of prototype bandage lapper for constant tension bandaging required for effective medical-clinical treatments

Someshwar Bhattacharya, Tasnim Shaikh, Roshan Purushottam Solao — 2012-04-30

Abstract: Application of the bandaging materials is a skilled task and required considerable practice to perform it correctly. The variation in bandaging pressure is introduced due to different tensions applied by different persons during lapping. So, a handy mechanical bandage lapper is developed. This helps in keeping lapping tension uniform and adjustable irrespective of the bandager. Its proficiency is checked by bandaging two persons with different fore-arm circumferential measures. Bandaging is done at three different limb positions with and without the use of bandage lapper up to three layers by the same bandager. Three different lapping tensions viz; 0.40 kgf, 0.45 kgf and 0.50 kgf are set up for bandage lapper to study their impact on bandage pressure. Pneumatic bandage pressure mapper is developed for the measurement of bandage pressure. Seven trials separated by different time intervals are conducted for each variable. This has prevented record of consistency of bandage pressure measure by chance.Crepe bandage, normally employed for the management of Oedema in clinical treatment is used throughout the study. Higher coefficient of variations up to 15% in pressure values are found when bandaging done without the lapper. However, identical pressure, coefficient of variation less than 0.3% for all except 0.8% for bandaging done at 0.45 kgf for second person at position 1, is mapped when bandaging done with the lapper by the same bandager.

Limb salvage for spreading midfoot osteomyelitis following diabetic foot surgery

2012-01-09

Abstract: Osteomyelitis is a challenging problem when it appears in the feet of patients with diabetes. Although the most frequent port of entry for bacteria is an ulcer, surgical wounds also permit entry of bacteria into the foot. This surgical complication may become limb-threatening, and treatment is a challenge. Here we present two cases of patients with neuropathic feet and palpable distal pulses, who were previously treated with surgery, and who presented with spreading bone infection in the midfoot. Pictures and radiological studies are shown. In both cases, bone infection caused severe destruction of the architecture of the midfoot, and the limbs of both patients were threatened. Midfoot osteomyelitis is associated with a higher rate of major amputations than osteomyelitis of the forefoot. Furthermore, meticillin-resistant Staphylococcus aureus was isolated in one of the cases. Our successful limb salvage approach was based on three steps: 1) removing the infected bone; 2) culture-guided antibiotic treatment; and 3) stabilizing the infected foot by means of total contact casting with openings resulting in a stable foot. To the best of our knowledge, there are no reports of the use of a total contact cast to stabilize an unstable and infected foot. Eight years (Case 1) and four years (Case 2) after complete healing, there were no recurrences of infection.