Page 3 - AUTHOR’S SURGICAL TECHNIQUE FEMUR

Step 1: The patient is positioned supine on a radiolucent operating table (Fig. 4). A radiolucent bump (usually a folded towel or sheet) is placed underneath the ischium on the operative side. This allows good visualization of the hip on both anteroposterior (AP) and cross table lateral views (Fig. 4).

Step 2: Using the image intensifier (fluoroscopy) the tip of the level of the greater trochanter is marked on the skin. Knowing the length of the nail to be used for the surgery, a ruler is used to mark the distal end of the nail.

Step 3: The level of the osteotomy is determined by knowing the amount of distraction planned. One must plan to end up with the larger diameter of the nail always engaged on both sides of the distraction gap at the end of lengthening. Assuming one wants to have 2 cm of the larger diameter of the nail engaged, then add 2 cm plus the 3 cm of smaller diameter nail, which is exposed plus the distraction amount. This total measured from the distal end of the nail represents the level of the desired osteotomy that will leave at least 2 cm of the larger diameter of nail always engaged.

Step 4: Make a 1-cm incision laterally at the level of the osteotomy. Drill holes using a 4.8-mm drill bit. I prefer one entrance and 3 exit holes; anteromedial, anterolateral, and medial. Then make 2 more holes anterolateral and posterolateral at the level of the other holes. These holes will serve to vent the canal from fat emboli and to allow the reamings that spill out to help fertilize the bone formation at the distraction gap.

Step 5: Get your starting point using a Steinmann pin in the piriformis fossa for adults or children with closed growth plates. Enlarge this opening using an anterior cruciate ligament (ACL) reamer. For open growth plates, insert the Steinmann pin into the tip of the greater trochanter.

Step 6: Open the fossa or trochanter with an ACL reamer.

Step 7: Insert a beaded guide rod down the femur.

Step 8: Ream in 1-mm increments until there is chatter and then in ½-mm increments. Ream to 12.5mm for the 10.7mm nail and to 14.5mm for the 12.5mm nail.

Step 9: Prepare the nail for insertion. With Precice 1, choose and assemble the insertion end type (trochanteric, piriformis, retrograde, tibial) and lengths. The mechanism comes in 1 length, whereas the final nail length depends on the length of the insertion end chosen. With the new Precice 2, the nail is not modular and one must choose the length of the entire nail in advance.

Step 10: Apply the proximal targeting device and test its alignment to the screw holes by inserting the drill guides and bits.

Step 11: Place the nail under the beam of the image intensifier to see if the mechanism is not predistracted. Save this image for reference.

Step 12: Remove the initial beaded guide wire used for reaming, as the nail is not cannulated. Insert the nail into the canal up to the level of the planned osteotomy (drill holes). Step 13: Have one assistant lift the foot off the table.

Have the other assistant lift the proximal end of the nail using the insertion guide. The two assistants are applying an extension moment to the femur to prevent displacement of the femur during the osteotomy.

Step 14: Use a sharp osteotome to osteotomize the femur through the 1-cm lateral incision. The femur will easily break through the 6 drill holes. Listen for the break and once it occurs withdraw the osteotome. Test that the femur is fractured while maintaining the extension moment. Move the femur gently into varus and valgus and watch it move on the image intensifier.

Step 15: Once the break is confirmed to be complete, advance the nail by gently hammering on the impactor until the upper end is at the level of the base of the piriformis fossa or just inside the greater trochanter for piriformis and trochanteric nails, respectively.

Step 16: Lock the nail proximally with 2 screws. For distal locking screws, my personal preference is to insert a long 1.8- mm wire into the locking hole, followed by a 3.8-mm cannulated drill for the distal 10.7 nails and a 4.8-mm cannulated drill for the distal 12.5-mm drills. In the 10.7mm over drill with a solid 4.0mm drill after removing the cannulated one.

Step 17: Lock the nail distally with 2 screws. Avoid inserting the anteroposterior middle screw because it can act as a stress riser for fracture of the femur.

Step 18: Insert the end cap into the proximal part of the nail.

Step 20: Close all the incisions.

Step 21: Insert the ERC device into a sterile sleeve. Mark out the level of the magnet on the skin using fluoroscopy. Apply, the ERC directly over the magnetic spindle, using the image intensifier to mark out the magnet. It takes 7 minutes to lengthen the femur 1 mm. Remember to program the ERC for antegrade or retrograde use.

Step 22: Check if the distraction gap is seen radiographically and compare it to the predistraction space. If an objective increase in space is seen the procedure is completed. If not do a second millimeter of distraction to confirm. In the rare case where the bone does not separate, the nail must be extracted and tested on the bench and if it does not distract then replaced with another nail. An incomplete osteotomy can cause a failure of distraction and can even lead to failure of the mechanism due to the high force of resistance.