Minimally Invasive Approach to the Proximal Femur for Intramedullary Nailing
Minimally Invasive Approach to the Proximal Femur for Intramedullary Nailing
The minimally invasive approach to the proximal femur is used for the insertion of intramedullary nails for the treatment of the following:
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Acute femoral shaft fractures
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Pathologic femoral shaft fractures
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Delayed union and nonunion of femoral shaft fractures
The entry point for the insertion of an intramedullary nail into the femur is determined radiographically. It depends on the design of the nail and the anatomy of the proximal femur in the individual patient. The majority of intramedullary nails are straight when viewed in the anterior–posterior plane. The nail should be inserted so that its entry point into the bone is exactly in line with the intramedullary canal on both anterior–posterior and lateral radiographs. The use of preoperative templates overlying radiographs allows for a precise calculation of the entry point.
For nails that are straight when viewed in the anterior–posterior plane, the skin incision, the entry point of the nail in the bone, and the medullary canal of the femur should all be in a straight line.
Some nails especially those used for fixation of extracapsular hip fractures are angled at their upper end and require insertion via the tip of the greater trochanter. These nails require a skin incision directly over the tip of the greater trochanter.
Position of the Patient
Two positions are available for the insertion of femoral nails. The supine position allows easier control of fracture reduction and distal locking of the nail (Fig. 9-35). The lateral position allows easier access to the entry point in the proximal end of the femur. It is favored by many surgeons when treating obese patients.
Supine Position
Place the patient supine on a traction table. Employ traction using a supracondylar femoral pin or a traction boot. Adduct the leg as much as possible around the traction post to make it anatomically possible to enter the upper end of the femur via the skin on the lateral aspect of the buttock. Laterally flex the trunk of the patient away from the operative side. Flex and abduct the opposite hip and flex the knee, placing the leg in a support (see Figs. 9-35 and 9-36A). Ensure that adequate anterior–posterior and lateral radiographs of the entry point of the nail and the fracture site can be obtained. Be sure that the fracture is reduced or reducible before commencing surgery. Although this may be time-consuming, it is important to obtain good-quality radiographs before commencing surgery, or you will struggle to obtain quality imaging during the case. Five minutes of preoperative time may shorten your operating time by 2 hours.
Figure 9-35 Place the patient supine on the traction table. Reduce the fracture by traction and manipulation. Adduct the leg as much as possible around the traction pole. Abduct and flex the opposite hip to allow C-arm access to the whole of the femur.
In displaced subtrochanteric femoral shaft fractures, the proximal fragment will flex and abduct due to the unopposed pull of the psoas and the abductor muscles. Displaced proximal femoral fractures cannot be reduced by traction alone. Control of the proximal fragment frequently requires percutaneous insertion of a Steinmann pin into the proximal fragment, allowing its manipulation.
Inserting a nail in a very obese patient cannot be done successfully in the supine position (Fig. 9-36).
Lateral Position
Place the patient in a lateral position on a traction table with the affected limb uppermost. Apply traction to the femur through a distal supracondylar pin or a plaster boot. Adduct the leg over the traction pole. Place the contralateral limb in a flexed position at both hip and knee. Take care to pad the bony prominences of the bottom leg to prevent skin breakdown due to pressure. Ensure that adequate anterior–posterior and lateral radiographs of the entry point and the fracture site can be obtained. The fracture must be reduced or reducible before commencing surgery. Proximal femoral fractures will require ancillary modes of reduction
(Steinmann pins) (see Supine Position above).
The lateral position allows easier access to the proximal femur than the supine position because it allows more adduction, which is particularly useful in obese patients. In cases of extreme obesity, even this position may not permit successful intramedullary nailing; such patients are probably best treated by a retrograde nailing technique with an entry point into the bone in the intercondylar notch.
Landmarks and Incision
Landmarks
The greater trochanter is a large mass of bone that projects upward and backward from the junction of the shaft of the femur and its neck (see Fig. 8-43).
The anterior-superior iliac spine can be felt as the anterior margin of the iliac crest (see Fig. 8-43).
Figure 9-36 A: Adducting the leg moves the skin incision distally. B: In obese patients, nailing in this supine position is impossible. Note that even with maximal adduction, the ideal incision lies above the iliac crest.
The shaft of the femur can be felt as resistance through the massive vastus lateralis muscle on the lateral side of the thigh.
Incision
There are two techniques for planning the correct placement of the incision.
Radiographic Technique. Palpate the shaft of the femur on the lateral aspect of the thigh through the bulk of the vastus lateralis muscle. With a marker pen, draw a line on the skin, marking the lateral aspect of the shaft of the femur (Fig. 9-37). This line is curved because the femur is bowed anteriorly when viewed in the lateral plane. Extend this gently curving line proximal to the tip of the greater trochanter, up to the level of the iliac crest (Fig. 9-38).
Take a long artery forceps and move it proximally along the line you have drawn on the skin. Screen this instrument using an image intensifier in the anterior–posterior planes (see Fig. 9-39). When the image of the tip of the forceps coincides with the guidewire radiographically, mark the skin (see Fig. 9-39). This skin mark will be the center of the skin incision. A wire inserted through this incision and through the correct entry point in the bone will pass perfectly down the center of the medullary canal of the femur in both anterior–posterior and lateral planes.
If the patient is obese and/or you are unable to adduct the leg, then this entry point will be above the level of the iliac crest (see Fig. 9-36B). Such an entry point is clearly not usable. If this is the case, then alternative techniques using curved instrumentation will need to be used through a more proximally based incision.
Landmark Technique. Palpate the shaft of the femur through the bulk of the vastus lateralis muscle. With a marker pen, draw a curved line on the skin of the lateral aspect of the thigh, marking the shaft of the femur (see Fig. 9-37). Extend this line proximally beyond the tip of the greater trochanter, curving it slightly posteriorly.
Figure 9-37 Palpate the shaft of the femur through the vastus lateralis muscle. Draw a line on the skin, marking the line of the shaft of the femur. Note that this line is curved.
Figure 9-38 Extend the drawn line above the tip of the greater trochanter to the level of the anterior-superior iliac spine.
Incision
Make a longitudinal incision centered on the skin mark. The size of the incision depends on the type of nail to be used. Nails that have proximal interlocking jigs that are considerably offset from the nail can be inserted through a 3-cm incision. Nails whose proximal jigs attach close to the nail require a longer skin incision (up to 7 cm).
Internervous Plane
There is no internervous plane or intermuscular plane. The dissection splits fibers of the gluteus maximus and gluteus medius but does not denervate either muscle.
Superficial Surgical Dissection
Incise the subcutaneous fat and the fascia overlying the gluteus maximus in line with the incision. Split the fibers of gluteus maximus for 3 cm in the line of its fibers using a curved clamp.
Deep Surgical Dissection
Continue the dissection distally using a long curved clamp to split the fibers of the gluteus medius muscle to gain access to the proximal femur. Careful use of a finger as a blunt dissector to identify the medial aspect of the greater trochanter is often helpful as well. Insert a marker wire (or rod) through the completed dissection onto the proximal end of the femur, and adjust the position of the wire using x-ray control in both anterior–posterior and lateral planes until the wire is at the correct entry point into the bone. The wire must line up with the intramedullary canal on both anterior–posterior and lateral planes (Figs. 9-41 and 9-42).
The exact techniques for entering the proximal femur vary from nail to nail. You must consult the appropriate literature to ensure that the instrumentation is used correctly.
Figure 9-39 Place a long guidewire on the anterior surface of the thigh and position it under image intensifier control so that its image overlies the center of the medullary canal of the femur. Take a long artery forceps and move it
proximally along the drawn line on the lateral aspect of the thigh. When the image of the forceps coincides with the image of the guidewire radiographically, mark the skin.
Dang
Bone Deformity
The presence of an incorrect entry point is potentially hazardous in intramedullary nailing of the femur.
An entry point that is too far lateral commonly occurs. This will create a varus deformity at the fracture site if the nail used is rigid, and the fracture is in the proximal third of the femur. Lateral entry points may also create an iatrogenic fracture of the medial femoral cortex during nail insertion.
An entry point that is too far medial may create an iatrogenic fracture of the femoral neck, usually a vertical basicervical fracture. On occasion, medial entry points may also damage the blood supply to the femoral head, creating avascular necrosis.
Nerves
The superior gluteal nerve runs posteriorly to anteriorly through the substance of the gluteus medius muscle 3 to 5 cm above the tip of the greater trochanter. If the femur is adducted, the nerve will not be damaged during insertion of a nail. If, however, a retrograde nailing technique is used when the femur is not necessarily abducted, then damage to the nerve may occur.
How to Enlarge the Approach
This approach cannot be usefully enlarged proximally or distally because it does not utilize an internervous plane.
Figure 9-40 Landmark technique. Draw a line perpendicularly downward from the anterior-superior iliac spine. Where this line crosses the previously drawn line on the lateral aspect of the thigh, mark the skin.
Figure 9-41 Split the fibers of the gluteus maximus in line with the skin incision. Deepen the incision down to the femur by splitting the fibers of the gluteus medius.