Stabilization of Coxofemoral Luxation Using the Toggle Pin Method
A number of surgical methods for maintenance of reduction of coxofemoral luxations are currently popular and include: the toggle pin method, ilio-femoral sutures to limit external rotation of the hip, and caudo-distal transposition of the greater trochanter. Each of these methods depends on the joint capsule and associated muscles for acute and especially, for long-term maintenance of joint stability. If the joint capsule is severely traumatized and not conducive to primary repair, some surgeons will elect to perform a capsulorrhaphy or dorsal augmentation of the joint capsule. With any of the just mentioned surgical methods for stabilization of hip luxations, it is important to remember that the use of sutures and anchors must be considered a temporary solution until the joint capsule and periarticular soft tissues can heal. As such, patients with poor hip conformation are not good candidates for these methods of repair and should be considered for salvage procedures, such as FHNE or THR.
The toggle pin method of maintenance of coxofemoral luxations has been around many years. Commercially available toggle pins, IMEX™ Polypropylene Suture Buttons, and the IMEX™ Universal Aiming Device have simplified the method and increased its popularity. This method places a strand (or multiple strands) of suture material in a location that mimics the normal origin and insertion of the round ligament of the femoral head, which is torn when the hip is traumatically luxated. This anatomic positioning of suture material is relatively straightforward and visually demarcated in the hip, and perhaps is partially responsible for the logic and popularity of the method. Different suture materials and sizes are used based on the surgeon’s preference. Our customers use both monofilament and braided suture materials. Braided materials are popular with customers who desire strength and knot security. Typical sizes include # 2 and # 5 commercially available braided polyester. Monofilaments are popular with customers who desire a relatively inert material, and common examples include monofilament nylon fishing leader and Prolene® (Ethicon).
Figure 1: This method of repair is best accomplished through a craniolateral approach to the hip with caudal retraction of the femur to allow for complete visualization, exploration, and appropriate debridement of the acetabulum. After debridement of impinging tissue, clot, and remaining round ligament in the acetabulum, a hole is drilled completely through the medial wall of the acetabulum centered in the acetabular fossa. The diameter of the hole must be large enough for the toggle pin and suture combination chosen. A 3.2mm toggle pin will require at minimum a 3.5mm hole. However, a 4.0mm hole, or larger, is often needed if using heavy monofilament line. For the 4.0mm toggle pins, a 4.5mm or 5.5mm drill bit is recommended. The toggle pin-suture combination should be easily inserted through the acetabular drill hole. If difficulty is encountered, the acetabular hole should be enlarged with a larger drill bit.
Figure 2: The aiming device is used to drill a femoral tunnel for the suture. The aiming device is placed such that the tunnel is drilled from the subtrochanteric area of the lateral femur to the fovea capitis of the femoral head. A 3.5mm drill bit is the most frequently recommended size, as the IMEX™ suture passer is 3.2mm in diameter. If heavy monofilament line is being used, it may be necessary to use a larger diameter drill bit. When drilling of the femoral tunnel is nearly complete, it is advisable to extend the pointed end of the aiming device so that it no longer contacts the femoral head such that when the drill bit exits, it is not damaged on the aiming device.
Figure 3: The suture used for repair is passed through the hole in the toggle pin once so that a simple loop is created. The toggle pin is held at one end using wire twisters, Kelly forceps, or a similar instrument. The suture is pulled tight along the sides of the toggle pin such that each strand seats within the toggle pin grooves. The toggle pin is then visually started into the acetabular drill hole and inserted as far as the forceps will allow. The instrument is removed, and the blunt end of the IMEX™ suture passer is used to push the toggle pin completely through the acetabular drill hole. (If this step seems to require excess force, it is likely that the acetabular drill hole is not large enough to accommodate the diameter of the toggle pin-suture combination used.)
Figure 4a: The ends of the suture are spread and tensioned to pull the toggle pin tight against the medial wall of the acetabulum. The toggle pin is tested for secure seating within the pelvic canal. The suture is then pushed or pulled through the femoral canal to exit the lateral femur. The suture is tensioned while the femoral head is reduced into the acetabulum.
Figure 4b: Appropriate reduction is verified and the ends of the suture are tied over another toggle pin or a suture button as shown in figure 4b. Alternatively, another small bone tunnel can be drilled in the lateral aspect of the femur to allow one of the suture strands to be passed through and then tied to the opposite strand. The hip should be appropriately reduced and firmly seated; however, do not over tighten the suture by placing excess tension on it. This will adversely effect hip joint range of motion and will cause the suture to fail prematurely.
Multiple Uses for Universal Aiming Device
|A. Accurate placement of transcondylar lag screws for repair of humeral condylar fractures is facilitated by use of the universal aiming device. Transcondylar ESF pins can also be pre-drilled in similar fashion.
B. Utilizing ESF diameter drill guides also allows one to target ESF full-pins, which can be beneficial when using the KE and KE-like devices.
C. Placement of a temporary calcaneo-tibial screw is one method of protecting surgical repair of the Achilles tendon.
D. Placement of lag screws or wires across femoral neck fractures is also facilitated by use of the universal aiming device. A variety of drill guide diameters are available to support a wide range of screw diameters.
E. Anytime one desires to exit a drill bit at an exacting location there is potential benefit to using the universal aiming device.