Stabilization of Coxofemoral Luxation Using the Toggle Pin Method
by IMEX Veterinary
There are a number of popular surgical methods for maintaining reduction of coxofemoral luxations - use of 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 stability, and especially for long-term stability. If the joint capsule is severely traumatized and not conducive to primary repair, some surgeons elect to perform a capsulorrhaphy or dorsal suture augmentation of the joint capsule. With any surgical method for stabilization of hip luxations, it is important to remember that the use of sutures and anchors must be considered temporary solutions until the joint capsule and periarticular soft tissue 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, 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 is perhaps partially responsible for the logic and popularity of the method.
Different suture material and sizes are used based on the surgeon’s preference. IMEX customers use both monofilament and braided suture material. Braided material is popular with customers who desire strength and knot security and tends to bend acutely around anchors or toggles better than monofilament suture material. Typical sizes include #2 and #5. Monofilaments are popular with customers who desire a relatively inert material; common examples include monofilament fishing leader and Prolene.
Craniolateral Approach to the Hip
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, a hole is drilled completely through the medial wall of the acetabulum centered in the acetabular fossa. Use of a hand-held drill sleeve will simplify drilling while protecting the femoral head. The diameter of the hole must be large enough for the toggle pin and suture combination chosen. A 3.2 mm toggle pin will require at minimum a 3.5 mm hole. However, a 3.9 mm hole or larger is often needed if using heavy monofilament line. For the 4.0 mm toggle pin, a 4.5 mm to 5.5 mm 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 may be enlarged with a larger drill bit.
FIGURE 1 | Craniolateral approach to the hip
Femoral Neck Tunnel for Suture
The aiming device is used to drill a femoral neck tunnel for the suture. The aiming device is placed so the tunnel is drilled from the subtrochanteric area of the lateral femur to the fovea capitis of the femoral head. It is helpful to have a surgical assistant at this time. The 3.5 mm drill bit is the most common drill bit utilized in medium to large dogs and also the minimum hole diameter used with the suture passer. When drilling of the femoral tunnel is nearly complete, it is advisable to remove the aiming device and complete the drill hole by hand. This eliminates potential damage to the drill bit. 2.0 mm and 2.7 mm tunnels should be used in smaller patients.
FIGURE 2 | Femoral neck tunnel for suture
Toggle Pin and Suture Insertion
The suture used for repair is passed once through the hole in the toggle pin creating a simple loop. The toggle pin is held at one end using large needle holders, Kelly forceps, or a similar instrument. The suture is pulled tight along the sides of the toggle pin so 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 instrument will allow. The instrument is removed, and the blunt end of the suture passer or drill bit 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 and suture combination used.
FIGURE 3 | Toggle pin and suture insertion
Test Security of the Toggle Pin within the Pelvic Canal
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 and tensioned while the femoral head is reduced into the acetabulum.
FIGURE 4 | Capsulorrhaphy for hip luxation
Verify Reduction and Suture is Securely Tied
Appropriate reduction is verified and the ends of the suture are tied over another toggle pin or a suture button as shown in figure 5. 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.
FIGURE 5 | Verify reduction and suture is securely tied