Cortical Screw Post Femoral Fixation Using Whipstitches, Fabric Loop, or Endobutton: The Universal Salvage

Chapter 32 Cortical Screw Post Femoral Fixation Using Whipstitches, Fabric Loop, or Endobutton


The Universal Salvage



Chadwick C. Prodromos



Background



Importance


We believe that every surgeon performing anterior cruciate ligament reconstruction (ACLR) would benefit by being able to perform at least one of the variants of cortical screw post femoral fixation described here. Although probably not their primary techniques, they are the universal “bail-out” methods for rescuing more exotic and complicated single-incision techniques gone awry on the femoral side. The ability to troubleshoot is arguably the most important skill a surgeon can possess, and these techniques not only troubleshoot all other femoral methods (and all grafts), but they also can be accomplished with materials that are present in every orthopaedic surgical suite.



History


Whipstitch cortical screw post was perhaps the most popular method of soft tissue ACL graft fixation when two-incision methods were commonly used. There are many reports of high stability using this method.1–6 However, the advent of the Endobutton and then the various cross-pins that did not require a formal second incision relegated the two-incision method to a secondary role. More recently it has become apparent that a second incision for outside-in drilling can facilitate the lower femoral tunnel placement that is now recognized as biomechanically preferable, and more two-incision methods are now being described.



Biomechanics


The technique uses rigid cortical bone for anchorage. This has been shown to be the most important factor in producing high-stiffness fixation.7 The stiffness is reduced slightly by the length of the construct, but the rigidity of the cortical bone7 has been shown to more than compensate. A fabric or suture interface has been associated with high-stability ACLR,8–11 as have whipstitches if properly implanted.12–14 Both are described here in conjunction with cortical screw post fixation.



Advantages


We no longer use the femoral screw post through a second incision as a primary method because we have had success using the one-incision Endobutton method. However, we still believe that the two-incision technique has a number of advantages.


1 It is useful in revision cases where single-incision techniques may be problematic or impossible.

2 It is useful in difficult primary cases, particularly those with small distal femora resulting in short femoral tunnels as a backup to single-incision techniques if the surgeon blows out the back wall.

3 It allows odd-numbered strand grafts such as triple semitendinosus (3ST), 3ST/1 gracilis (Gr), and 3ST/2Gr,2 grafts that cannot be looped as a quadruple graft with the use of cross-pins.

4 We believe that due to the small learning curve, it is a more reliable method than some complicated single-incision techniques for the surgeon who performs a small volume of ACL reconstructions.

5 It allows the most precise proximal-distal positioning of the graft in the tunnels and knee of any method. This is useful with shorter grafts where malposition in the proximal-distal direction may result in too little graft length in one of the tunnels.

6 No other fixation method has resulted in higher stability rates.2

7 Most importantly, as mentioned earlier, it can troubleshoot any problem that occurs with a femoral fixation device, femoral tunnel, or femoral graft.

The only disadvantage to this technique is that it requires a second incision. However, this disadvantage is usually primarily in the mind of the surgeon. We, and others, have never found the use of a small second incision to be of concern to the patient (see Chapter 49). Furthermore, the incision does not need to be large. Some may dislike the fact that a nonbioabsorbable and nonradiolucent screw remains in the patient. However, we have never seen one of these screws back out, nor have we ever seen one bother the patient2 because the screw sits flush on cortical bone under a thick muscular layer. Plus, because they are metadiaphyseal, they are far enough from the joint to not interfere with subsequent magnetic resonance images (MRIs).



Surgical Technique



Materials


A standard 6.5-mm, two-thirds threaded cortical screw with a smooth washer is usually used. ACL tibial fixation posts can also be used as follows: There are two 4.5-mm screws without washers with which we are familiar, one made by Smith & Nephew (Andover, MA) and one by Arthrex (Naples, FL). If these washerless screws are used, the screw must be slightly angled away from the femoral tunnel to prevent suture or fabric loop slippage. Linvatec (Largo, FL) has a good 6.5-mm screw, which is used with a washer. Arthrex also has a 6.5-mm screw that is used with a washer, but it uses a smaller (2.5-mm) hex screwdriver. In the past we had occasional instances of breakage of the smaller screwdriver when it encountered high torque with the large screw.


Whipstitches should be put in using either standard #5 braided, nonabsorbable polyester sutures such as Ethibond (Ethicon, Somerville, NJ), Tevdek (SybronEndo, Orange, CA), or Mersilene (Ethicon) or one of the newer stronger #2 sutures such as Fiberwire (Arthrex) or Ultrabraid (Smith & Nephew). The surgeon may also pass a 5- or 6-mm Dacron tape through a quadruple graft and tie it around the cortical screw instead of using whipstitches. A 2- or 3-mm tape is not strong enough. The best loop, however, is the fabric loop that is attached to the Endobutton-CL, which comes in 5-mm increments with 15 mm being the smallest.



Incision


The lateral femoral incision should be made with the knee flexed. The posterior border of the lateral femoral condyle should be palpated and the incision made over the middle of the lateral femoral metaphysis at the flare of the condyle. In a lean patient this incision is about 2 cm long. It will need to be larger in larger patients. The iliotibial band is longitudinally split, and the lateral femoral metaphysis is exposed.



Femoral Screw Insertion Technique


The femoral screws should be inserted unicortically as with tibial screw posts for three reasons.


1 As mentioned earlier, we have never had one back out, so bicortical insertion is unnecessary.

2 They are cancellous screws, and if they are inserted bicortically, they may be impossible to remove later if needed.

3 Also, they can toggle if they are tied under tension before final tightening, with the tip moving slightly away from the predrilled hole in the opposite cortex. This may make it impossible for the tip of the screw to enter this hole at final tightening, resulting in the screw remaining proud and potentially irritating the patient. Unicortical insertion prevents this problem.


Attaching the Graft to the Femoral Post


There are four methods by which this may be successfully accomplished, all of which we have used. We prefer number four. Numbers one and four require an Endobutton-CL to be available. If it is not available, then method two or three may be used, and both are very satisfactory.

Related posts:

Anatomical Anterior Cruciate Ligament Reconstruction with Double-Bundle, Double-Stranded Hamstring Autografts: A Four-Tunnel Technique Proprioception and Anterior Cruciate Ligament Reconstruction Anterior Cruciate Ligament Reconstruction Utilizing the Rigidfix for Femoral-Sided Fixation Revision Anterior Cruciate Ligament Reconstruction Using Autologous Hamstring Tendons High-Stiffness, Slippage-Resistant Cortical Fixation Has Many Advantages over Intratunnel Fixation Endobutton Anterior Cruciate Ligament Reconstruction Femoral Fixation

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Mar 9, 2016 | Posted by in Reconstructive surgery | Comments Off on Cortical Screw Post Femoral Fixation Using Whipstitches, Fabric Loop, or Endobutton: The Universal Salvage

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