Influence of a relaxing incision on suture tension in Bassini's and McVay's repairs.

Suture tension levels measured during 151 inguinal herniorrhaphies in 135 men were higher initially and after a standard relaxing incision in 78 McVay's as compared with 73 Bassini's repairs. The difference, as well as the effect of the relaxing incision on tension, was greater in the middle. In 77 indirect repairs, before relaxation suture tension differed in 51 Bassini's and 26 McVay's procedures only in the midzone. However, with a relaxing incision, the former had much less tension. Similar results were obtained in 74 direct hernias, but better relaxation was seen in 52 McVay's repairs than with their indirect counterparts. These findings were confirmed when 42 McVay's and 37 Bassini's operations on equally (moderate) sized defects were compared. Thus, the complete repair (McVay's operation), with closure of the femoral canal and a deeper, more posterior suturing than in Bassini's operation, is associated with more tension. Use of a relaxing incision is obviously indicated. Further follow-up of our cases may substantiate that the level of suture tension at the time of operation correlates with the risk of recurrence.

Skin friction drag measurements by LDV.

A laser Doppler velocimeter employing a microscope objective as the receiving lens has been developed for measuring fluid velocity inside the boundary layer flow field with a spatial resolution of 40 microm. The method was applied for direct measurement of aerodynamic skin friction drag from the measured velocity gradient at the wall. Experimental results obtained on skin friction and on velocity components in a turbulent boundary layer on a low speed wind tunnel showed good agreement with previously reported data using conventional instruments such as hot-wire anemometers and Preston tubes. The method thus provides a tool for measurement and control of skin friction on aerodynamic bodies without perturbing the flow field.

Device and method for controlling cement thickness.

The ideal thickness of cement between the prosthesis and bone has not been accurately determined, but there is general agreement that the surgeon should be able to provide and accurately produce a certain thickness of cement between the prosthesis and the bone. Conventional cementing technique could allow the surgeon to ovepush the cup into direct contact with the bone producing a very thin cement coat or a void. We have developed a simple method of achieving a predictable thickness. We insert small spacers made of methylmethacrylate, which can be placed between the bone of the acetabulum and the acetabular component, preventing voids or thin areas in the cement coat. The device has been used in over 50 patients and has proven to be a simple and reliable method of allowing the surgeon to produce a predictable thickness of cement surrounding a joint replacement component. An additional benefit obtained from the use of these spacers is the ability to rigidly hold the acetabular component during polymerization of the acrylic without fear of overpushing. This allows better packing of the bone cement and prevents imperfections caused by the cup contacting the bone.