Background Firm bandaging of the knee following knee replacement may prevent bleeding into the joint by a tamponade effect. We studied the pressure required to achieve tamponade, and then clinically compared the use of a compression bandage with the use of a standard crêpe bandage, with or without a drain.Method Transducers were used to measure the pressure achieved on the surface of the knee under different bandages, and within the knee following release of the tourniquet. We prospectively compared 3 series of 50 patients each: (1) with compression bandaging from toes to mid-thigh, (2) with crêpe bandage from mid-calf to mid-thigh alone, or (3) with crêpe bandage and suction drain.Results The pressure within the joint at which tamponade occurs is 52-62 mm Hg. The pressure on the skin under a properly applied compression bandage is between 28 and 32 mm Hg, and this controls bleeding within the joint. Patients treated with compression bandaging recovered more quickly from the operation, had a shorter hospital stay, and a greater range of flexion on discharge. They had no swelling of the limb, rarely suffered a tense hemarthrosis, and had fewer complications.Interpretation The use of a compression bandage incorporating the foot and calf following knee replacement surgery, without the use of drains, confers specific advantages over the use of a crêpe bandage alone.

Veins taken from patients undergoing surgery for varicose veins were compared with those obtained from patients undergoing other surgical procedures ('normals'). Varicose veins had a lower breaking strength and breaking energy than normal veins. Elastic stiffness was less in normals (tan theta = 41 (24] than in varicose veins (tan theta = 55 (18); P less than 0.01). There was no difference in viscoelastic behaviour between samples taken above, at, or below the valve leaflet insertion. In normals, perivalvular vein wall exhibited a 50 per cent lower breaking strength and elastic stiffness than vein from other sites. Collagen content was significantly higher in normal vein specimens in all sites examined (mean collagen content = 70 (21) micrograms/mg, versus 51 (20) micrograms/mg for varicose veins; P less than 0.001). We conclude that significant structural changes are seen in varicose veins. In normal veins, the perivalvular vein wall has distinct viscoelastic features when compared with vein wall from other sites. This difference was not found in veins which became varicose.

Compression therapy is the principal treatment for leg ulcers associated with venous disease. The efficacy of compression therapy can be variable, which may in part be owing to the degree of compression applied. However, if the mechanism of action of this treatment could be better understood, it might be possible to improve its efficacy. It is not clear whether assessment of the degree of compression should be made under static or dynamic conditions, or both. A review of methods used previously suggests the need for a new method of assessment allowing continuous monitoring, even during movement. A system for continuous static and dynamic measurements of compression is described. Using an air chamber and manometer to test the system, agreement within +/- 3 mmHg is observed. The system is applied to investigate changes in forces, expressed as pressure, under bandages and compression stockings. Application of five bandage systems by experienced nurses to a volunteer shows a marked variation in applied pressure. During short periods of walking, rapid changes in pressure under compression stockings are observed, including some transients of less than 0.25 s. The method is simple to apply and may help to understand further the mechanism of action of compression therapy.

This paper describes a study of pilonidal excision wounds and abdominal wounds in which measurements of the wounds' volume and area were compared to their circumferences. A structured light method is proposed for the measurement of the three-dimensional circumference of acute cavity wounds, as circumference.is not easily measured by standard methods owing to the complex shape of some wounds.

Compression therapy is the principal treatment for leg ulcers associated with venous disease. The extent of compression generally can be estimated from the general Laplace equation relating pressure, bandage tension and leg radius. This study aimed to investigate the physical forces under long stretch bandages applied under constant tensions to cylinders of three defined radii ('model limbs'). Force expressed as pressure was measured under one, two and three layers of eight long stretch bandages and a plastic film (control) using temperature-compensated, strain-gauge pressure transducers. The bandages were applied at the manufactures' recommended extensions/tensions and at constant tensions (2-10N) to three rigid plastic tubes of increasing size, covered with a layer of soft foam. Foams of different hardnesses ranging from 20 to 230N were assessed. The median applied pressure and observed bandage characteristics changed with bandage type. The median applied pressure also changed with tension, number of layers, tube radius and foam hardness. The inter-layer shear component also tended to increase with the number of layers. An increase in sub-bandage pressure was observed relative to the radius, tension, foam hardness and number of layers but the relationship was not directly proportional. The shear force tended to be associated with increased bandage layers.

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The system enables forces associated with compression therapy to be examined during movement and may thus be of value in further understanding its mechanism of action. Foot movement can be associated with clear changes in pressure under compression stockings and rapid changes in pressure may occur during walking.

-This paper describes a digital image processing system for the analysis of colour in wound images under clinical conditions. The system uses a 3CCD array digital video camera together with a colour scale for reference. The accuracy of colour assessment was compared with clinicians' assessment of the amount of slough (necrotic tissue) in digital images. The system was found to be within the range of 10% in describing red hue values in red colour patches between different clinical sessions. There was agreement in 75% of the cases between clinicians' assessment of the amount of slough and a computer assessment using digital imaging. However, colour may not be sufficient to describe wound appearance accurately.