The present invention relates to a surgical fastener or device (implant) formed in the shape of a screw and washer system and the method for manufacturing the same. The surgical implant of the present invention is particularly but not solely intended to be used in repair surgery for the tendons of the rotator cuff.
Tearing and degradation of the tendons of the rotator cuff muscles is a common and potentially painful and debilitative problem affecting thousands of people each year. The repair of the rotator cuff nearly always requires that the surgeon affix tendon to bone. Initially, surgical treatment of this condition required open surgery. To reduce the trauma of open surgery, arthroscopic surgical techniques have been developed to treat this condition. In both open and arthroscopic surgery, surgeons presently use sutures to affix torn tendons to the humeral head. Specifically, the surgeon will suture the tendon to the humeral head by drilling holes entirely through the bone and running the sutures through the holes (intraosseous or transosseous suturing). See e.g., Ellman, Gartsman, Arthroscopic Shoulder Surgery and Related Procedures, pp. 178-79, 189-97 (1993); and Iannotti, The Rotator Cuff: Current Concepts and Complex Problems, p. 18-19 (1998), the entire disclosures of each of which are incorporated herein by way of this reference.
The use of sutures can be problematic for several reasons. The surgeon must carefully drill holes entirely through the humeral head. Suturing the tendon to the bone through the drillhole is an intricate and exceedingly time consuming process, particularly when done arthroscopically. Sutures may easily break or tear out of the tissue that is being sutured, rendering the cuff repair a failure. Alternatively, sutures may stretch or otherwise allow portions of the repaired tendon to separate from the humeral head (causing diastasis), which results in poor tendon-to-bone healing. Sutures may also strangulate the tissue being sutured. Also, generally nonabsorbable sutures must be used because absorbable sutures degrade too quickly. These nonabsorbable sutures, however, represent a foreign body that can cause irritation or other post-operative problems in the shoulder joint.
In an attempt to prevent sutures from easily tearing out of a tendon, some surgeons have used small plates to help distribute the force of the sutures across a greater cross section of the tendon, as described, for instance, in EP 520,177, the entire disclosure of which is incorporated herein by way of this reference. Such plates, however, do not address the weakness of sutures generally or the difficulty and time-consuming nature of using sutures. Further, such plates can reduce vascularization of the tendon, resulting in tissue necrosis.
One alternative to intraosseous suturing is the use of a suture anchor in the humerus. The suture anchor is inserted into a hole in the humeral head and the tendon is thereby sutured to bone. However, little study has been done with suture anchors in the repair of rotator cuffs and there is a concern about the pull out strength of suture anchors. This is of particular concern where the humeral head has become osteoporotic. As a result, such suture anchors present a problem in rotator cuff repair surgery. If a suture anchor pulls out, not only is the cuff repair jeopardized, the anchor may cause further additional damage and/or discomfort within the shoulder joint. This procedure also has the aforementioned difficulties concerning the use of suturing in the tendon. Further, if the suture anchor is not made of a bioabsorbable material, then its continued presence in the humerus could lead to postoperative difficulties due to the patient's possible negative reaction to the foreign material of the anchor or migration of the anchor.