1.  Field of the Invention
This invention relates, generally, to devices for placement of sutures in tissues, and more particularly, devices to gauge the depth of penetration of sutures in tissue. 
2.  Prior Art
In surgery, it is sometimes necessary to attach or suture materials to a first tissue, such materials including: an implanted device, an artificial tissue, a second tissue, or even the first tissue if that first tissue has become torn or separated.  The suturing method requires that a suturing device, usually a needle with attached suturing material, first be passed through the material to be attached, and then second, passed into the attachment tissue, thereby joining material and tissue by sutures.  The order of the above steps can be reversed. 
The required depth of penetration of the suture into the tissue can vary depending upon the materials to be attached, the type of attachment tissue, the thickness of the suturing device and the strength of the attachment desired.  The prior methods for gauging the depth of suture penetration depended upon the "look and feel" of the tissues and suture device.  That is, in placing the suture, the doctor would position a finger under the attachment tissue and would feel for the needle as it passed into the attachment tissue, the penetration depth being determined by the doctor's subjective estimate based upon the feel of the penetration and by visual inspection, where possible.  Because the "look and feel" method is subjective, proper suture depth penetration cannot be consistently or accurately obtained.  Further, with the increased concern over communicable blood-borne diseases, the "look and feel" method presents a danger because the suturing device, if depth of penetration is misjudged, can penetrate the doctor's finger causing the doctor's blood to mix with that of the tissue.  Thus, caution on the doctor's part is required; however, that caution must be balanced against the need to attain a suture with the desired penetration into the attachment tissue.