Pullout strength of the anchors used in arthroscopic rotator cuff surgery depends on various factors, such as the implant shape and the density of the bone in ...
J Orthop Sci (2010) 15:696–698 DOI 10.1007/s00776-010-1505-x
Rapid short communication Technique to secure loose anchors during rotator cuff repair RAFAEL ARRIAZA, PABLO CODESIDO, and GONZALO COUCEIRO ISAKOS Teaching Center, Hospital USP-Santa Teresa, Calle Londres 2, La Coruña 15008, Spain
Pullout strength of the anchors used in arthroscopic rotator cuff surgery depends on various factors, such as the implant shape and the density of the bone in which they are inserted. Unfortunately, most patients with long-standing rotator cuff tears have diminished bone density in the proximal humerus.1 This can produce the feeling of anchor loosening when the surgeon tests the stability of the implant by tugging on the sutures, or — even worse — the anchor can loosen or dislodge from bone postoperatively.2,3 To improve anchor fixation if loosening is identified intraoperatively, it has been proposed that a second anchor be placed parallel to the first one, significantly increasing pullout resistance.4 In this article, we present a simple technique to reinforce anchors during arthroscopic rotator cuff repair if loosening is observed. The only required material is a cannulated, 4-mm osteosynthesis cancellous screw, which is available in most operating rooms.
through the same portal used to place the anchor to allow a parallel direction. First, by using an arthroscopic probe or a blunt trocar, the anchor is replaced at the proper depth into the bone tunnel. Then, a guidewire is placed parallel to the anchor, carefully choosing a position that allows the cancellous screw to avoid the suture limbs (Fig. 1). The configuration of most shoulder anchors results in the suture limbs exiting the anchor at a 180° angle, allowing a wide area in which to place the screw safely. Using palpation with the tip of the guidewire, thereby avoiding over-penetration, the intraarticular position is confirmed. If in doubt, arthroscopic intraarticular evaluation can help confirm that the tip of the screw is not protruding into the joint. In our cases, 28 to 30 mm long, 4-mm cannulated cancellous screws were inserted following the guidewire until the screw head was below the hole level, just above the anchor. In this way, the head of the screw helps prevent anchor migration. After repeated stability testing, surgery is continued.
Surgical technique
Discussion
After anchor placement, stability is tested by tugging on the sutures. If the anchor does not show evident loosening, surgery is continued. Sutures are passed through the tendon tissue of the cuff, and knots are tied. While tractioning the sutures for tying, it is important to again observe whether there is any sign of anchor loosening. If anchor loosening is appreciated at any point in time, reflecting poor fixation in the greater tuberosity bone, we reinforce it by introducing a cannulated screw parallel to the original anchor. Usually, the screw is placed
Although the geometry and design of anchors used for arthroscopic rotator cuff repair have evolved, implant loosening remains a problem. Insecure fixation can lead to failure of the cuff repair or even to implant dislodgement and migration to the subacromial space.5 In fact, new and stronger suture materials and suture configurations on the cuff could shift the mode of failure of rotator cuff repairs from knot slippage or suture cutting through the tendon tissue to anchor displacement from bone.6 The use of reabsorbable implants is appealing to the surgeon, as pull-out resistance is nowadays similar to that of metallic implants,7 with the theoretical advantages derived from their progressive absorption and disappearance, which would allow uncompromised
Introduction
Offprint requests to: R. Arriaza, Calle Juan Flórez 49, La Coruña 15004, Spain Received: December 8, 2009 / Accepted: May 11, 2010
R. Arriaza et al.: Loose anchor reinforcement
Fig. 1. Screw placement avoiding the suture limbs from the anchor
surgery in the future, should it be required. On the other hand, many bioabsorbable implants are not visible on plain radiographs, making unnoticed migration possible.5 If an anchor is found to be loose during surgery, the surgeon has several options for solving the problem, depending on whether the anchor can be reused and whether the knots have been tied. If the knots have not been tied, the usual option is to discard the hole and place a new anchor more laterally in the tuberosity, aiming for denser, more resistant bone because trying to place the implant deeper in the same hole usually does not increase the pull-out resistance of the implant, as the cancellous bone is not as dense as the subcortical bone. Alternatively, the anchor could be replaced by another one with a greater diameter, or it could be reinforced using another anchor placed parallel to the first one, in the “buddy system.”4 In any of these situations, there is a need to use another (expensive) anchor to solve the problem. The first option can work nicely if the problem is identified before the sutures are passed through the cuff tissue or even before they are tied, as the “retired” anchor can be reused in another area of the greater tuberosity with better bone quality. Reinforcing the anchor seems to offer better mechanical resistance to traction (or pull-out)4 and can be used even after knot tying, but it requires the use of another anchor. The use of a cannulated 4-mm osteosynthesis screw discussed here is another option; it is easy to use, fast, and inex-
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pensive. Even though the screw diameter is 1 mm less than that of the implants tested by other authors in the only published biomechanical study on the subject of loose-anchor-salvage procedure in cuff surgery,4 the interference fit stability could be increased by its greater length and the buttress effect of the screw head, offering greater resistance to anchor sliding. Although biomechanical testing should be done to confirm this point, our clinical experience, without postoperative complications and without screw mobilizations, suggests that it is a feasible alternative. The metallic osteosynthesis screw has the drawback of creating a magnetic artifact if magnetic resonanace imaging (MRI) of the shoulder is required after surgery, making it difficult to visualize the cuff; however, it is clearly visible in plain radiographs, allowing one to notice any displacement. One point of concern might be a biodegradable anchor reaction with the metallic screw, which could cause premature anchor degradation, or an increase in debris that could provoke an intraarticular reaction. Unfortunately, the mechanisms involved in degradable material-mediated tissue responses remain largely unknown. The problem of increased risk of foreign body reaction and sterile sinus formation seem to be more prevalent with increased debris. Especially in the case of polyglycolic acid (PGA) implants.8 The amount of debris caused by mechanical erosion of the implant by the metallic screw is probably too small to provoke what has been called a “burst” phenomenon. In syndesmotic ankle injuries, biodegradable screws are sometimes used through metal plate holes, which would cause some debris due to friction during screw insertion, as absolutely perfect perpendicularity is not possible; and in that setting, the prevalence of adverse reactions reported is not higher than with the use of resorbable implants alone.9 We have used this system in five cases, with good clinical results and without complications. The 1-year postoperative control radiographs have shown no screw migration. Unfortunately, anchor position could not be evaluated by MRI. Ultrasonography would not evaluate anchor movement, were it to occur, until the superior margin of the anchor lifted to the cortical bone level or beyond. Nevertheless, the good clinical progress of our patients has not suggested anchor migration or dislodgement.
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