SURGIGAL TEGHNIQUE FOR M/DN TIBIAL NAIL FIXATION

The major advantage of the tibial interlocking nail is the use of the closed technique during insertion as well as the ability to lock the nail proximally and distally to resist axial forces and shortening of the tibia. M/DN Tibial Interlocking Nails range in diameters from 6mm to 15mm and lengths from 18cm to 46cm. (Table 1)

INDICATIONS(FIG.1)

The Tibial Nail is indicated for use in a variety of tibial fractures, such as:

A. Comminuted fractures

B. Segmental fractures

C. Fractures with bone loss

D. Nonunions

E. Proximal and distal fractures

PREOPERATIVE PLANNING

Proper preoperative planning is essential to success-ful interlocked nailing of the tibia. A template or Ossimeter, and an x-ray film of the unaffected extremity are necessary for determining canal size and for measuring the length of the tibia to aid in determining nail length.

Harris/Galante Bulb-tipped Guide Wires (Sounds), available in diameters from 10mm-17mm, can be used as an alternate technique to determine nail diameter and length.

X-rays taken at a 36-inch distance from the x-ray source result in 10-15 percent magnification of bone. The M/DN Ossimeter has both an actual size scale and one that takes into account this magnification. It should be used routinely to determine nail diameter and length.

The proper length of the nail should extend from 1cm below the top of the tibia to the epiphyseal scar. The diameter of the tibial nail should match the canal in the lateral x-ray projection. The surgeon should review the x-ray to assure that there are no unusual anatomic variations.

PATIENT POSITIONING AND RADIOGRAPHIC CONTROL

Place the patient in the supine position of the fracture table with the injured extremity in traction and the knee in flexion. Place the counter traction bar at the level of the distal thigh and not in the popliteal fossa (Fig.2).Place the unaffected leg in a leg holder so it is held straigth to allow easy access for the C-arm to the injured extremity. Visualize the knee as well as the shaft of the tibia using image intensification to confirm proper positioning prior to prepping and draping.

An alternative method of positioning is to place a radiolucent frame under the knee.

Another alternative is to place the patient on a radiolucent table, using a distractor for fracture reduction.

REDUCTION

It is important to reduce the fracture before beginning the surgical procedure.

INCISION AND EXPOSURE

Make a longitudinal incision along the medial border of the patellar ligament extending from the joint line to the inferior pole of the patella (Fig.3). Carry the dissection medially to the patellar tendon down to the bone. Place a Blunt Retractor beneath the patellar ligament and retract the ligament laterally to expose the proximal tibia.

CREATING THE ENTRY PORTAL

Place the Tibal Awl medial to the patellar tendon and at the top of the tibia (Fig.4). Fox proximal fractures, either split the patellar tendon or position the wal lateral to the tendon to prevent angulation at the fracture site. Check the position with A/P and lateral views. When the correct position is achieved, rotate the awl to create an entry portal for the Bulb-tipped Guide Wire (Fig.5).

GUIDE WIRE PLACEMENT AND REAMING

Attach the 3.0mm Bulb-tipped Guide Wire to the Wire-Grip T-Handle (Fig.6) and tighten. To aid in manipula-tion, bend the tip of the guide wire at about a 10°-15°angle 2cm from the end (or use a pre-bent guide wire). Insert the guide wire through the entry hole and manipulate it down the proximal tibia. At the fracture site, manipulate the guide wire into the distal fragment under C-arm control (Fig.7). Once in the distal canal, pass the wire to its final position at the epiphyseal scar (Fig.8). Remove the Wire-Grip T-Handle.

Determine the proper nail length by placing a second guide wire of equal length on the proximal tibia. The length or the wire that is not overlapping is the correct nail length required (Fig.9). The 50cm ruler or ossimeter may be used for an accurate measurement.

Another way to measure the length is to use the C-arm to position the 0 mark on the metal ruler at the distal tibial epiphyseal scar. Then read the correct length at the proximal tibia directly off the metal ruler.

Place the Skin Protector in the wound. Then place an intramedullary reamer over the guide wire and ream the tibial canal in 1 millimeter increments until contact is made with the cortical wall. Continue to ream in 1/2 millimeter increments up to 1 millimeter greater than the selected nail diameter (Fig.10). During reaming, monitor the lateral view on the image intensifier to prevent excess reaming of the posterior cortex.

The proximal diameter of the 6mm through the 10mm nail is 11mm. Therefore the tibia must be overreamed to 12mm(approximately 64mm in length). Nails 11mm in diameter and above have proximal diameters equiva-lent to the shaft diameter. When the reaming is complete and the final measurements are made, insert the plastic Exchange Tube over the Bulb-tipped Guide Wire.

Remove the Bulb-tipped Guide Wire and insert the Smooth Guide Wire (Fig.11). Note: 6mm and 7mm nails are solid and, therefore, the guide wire must be removed prior to nail insertion.

NAIL INSERTION

Attach the selected nail to the Tibial Proximal Guide. A keyway in the proximal end of the nail will help ensure proper alignment. Be sure the arrow on the proximal guide is pointing to the appropriate ''Left'' or ''Right'' indication (Fig.12). Lift and turn the ratchet lever 90 degrees to open the ratchet mechanism of the Proximal Guide (Fig.13).

Insert the locking Bolt through the barrel of the guide (Fig.14). Lift and turn the ratchet lever 90 degrees to close the ratchet mechanism, and use the Pin Wrench to tighten the Locking Bolt into the proximal end of the nail. The ratchet mechanism will prevent the bolt from loosening during insertion of the nail.

Note: If the ratchet mechanism of the Tibial Proximal Guide does not operate freely, it may be necessary to disassemble, clean, and reassemble the mechanism. If the ratchet mechanism becomes inoperative, it may be removed. The assembly will still function; however, the Locking Bolt may loosen during the procedure.

Verify proper alignment by inserting the 8.0mm Tibial Screw Bushing, the 3.7mm Tibial/Humeral Drill Bushing, and the 3.7mm Drill (Table II) into the appropriate hole of the Tibial Proximal Guide. When the device is properly aligned, the drill will pass through one of the proximal holes and will not contact the nail (Fig.15).

Screw the Threaded Driver or Slaphammer into position on the Locking Bolt. Insert the nail over the Smooth Guide Wire and into the tibia. Begin seating the nail using bentle impaction with the mallet(Fig.16). The nail must advance with each blow of the mallet. If it does not, remove the nail and ream again. While impacting the nail, use the Tibial Proximal Guide to maintain the proper rotation.

Be careful when crossing the fracture site. Visualize the fracture in two planes with image intensification to assure proper passage of the nail into the distal fragment (Fig.17). The conical tip and the bevel of the nail will help guide it off the posterior cortex and maintain its position in the center of the canal (Fig.18). Reduce the force of impaction as the proximal end of the nail approaches the tibial tubercle.

Prior to inserting the nail past the guide wire exit hole, REMOVE THE GUIDE WIRE so it does not get trapped in the bone. Finish seating the nail after the guide wire is removed.