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THE GAMMA NAILS (STANDARD, TROCHANTERIC, AND LONG) TIPS AND PITFALLS
G. Taglang, B. Schenck, C. Averous
Draping - Incision
Nail entry point
Placement of reamer guide wire
Lag screw insertion
Strasbourg C.R.A.M.A.M. Centre of Traumatology and Orthopaedic Surgery - F-67400 Illkirch, France
The Strasbourg Centre of Traumatology and Orthopaedic Surgery (C.T.O.) has a long tradition of closed intramedullary nailing. While the Centre itself was founded at the end of the last century, intramedullary nailing came in, as a major femoral shaft fracture fixation technique, in the late 40s of this century. Gaston Pfister, then a young surgeon at the C.T.O., was the first to use the Küntscher nail for the stabilization of femoral fractures, back in December 1944.
Given this long period during which the technique originally devised by Gerhard Küntscher has been in use at our Centre, it is not surprising that it should have been modified and improved over the years. The locking nail, perfected by Grosse and Kempf in the mid-70s, is a good example of the developments and enhancements that have taken place; it is still the gold standard for the management of femoral and tibial shaft fractures.
For trochanteric fractures, the Ender technique was used at our Centre for many years; in fact, it was the Strasbourg school that introduced Ender nailing in France. Whilst this technique also involves closed nailing, and notwithstanding the improvements made by Kempf and Bitar by modifying the distal flats to make them lockable, it was not ideal. Apart from intraoperative problems (e.g. fracture at the entry site), there were many postoperative complications (pain; displacement into varus; external rotation, which could be considerable) which prompted us to search for different solutions.
Taking the concept of the locking nail as a starting point, we also looked at how closed stabilization of trochanteric fractures could be performed. At our Centre, the use of inverted locking nails (i.e. using a left locking nail in the right femur and vice versa) had been practised for a long time, and the first proximal targeting devices accompanying the nail had been designed with this practice in mind. Unfortunately, while the concept as such had much to commend it, there were biomechanical and technical problems: the inadequate screw diameter (0.35mm); only one angle (130°); and, above all, the fact that the threaded opening for the femoral neck screw prevented the screw from sliding when loaded, suggested to us that this avenue should not be explored any further. However, it was agreed that the principle a such was sound - the closed insertion of a locking nail, plus a lag screw in the femoral neck was the way to go. All that would be required to make this idea work would be greater implant strength, to be provided by an improved diameter of the lag screw and of the nail itself. Also, it would have to be possible for the lag screw to slide along its axis without spinning, so as to obtain true compression of the fracture site on weight-bearing. Finally, in order to avoid problems with distal locking using an image intensifier, it was decided that the nail should be short enough to dispense with radiological targeting, so that all that would be required was a nail-mounted targeting device. All these requirements were put together - and the Gamma nail was born.
In the time between that early design phase (back in 1981!) and the insertion of the first clinical prototype at the C.T.O. in December 1986, many changes were made in the light of the biomechanical test results. Without going into all the detailed changes in the design and the technical characteristics of the nail, we will be looking here at the devices in present-day use, and, of course, at the surgical technique for their insertion.
It goes without saying that the learning curve for the use of this closed technique is very much longer than that required for mastery of conventional open nailing. This fact accounts for certain complications, described at length above all in the English-language literature, when this nail was first introduced into clinical practice. Eventually, however, the Gamma nail came to be better understood and better used; and nowadays, its utility is recognized world-wide. It is said that imitation is the most sincere form of flattery. This is certainly so with the Gamma nail, of which many (licit and illicit) copies are now being used, even by surgeons who, not so long ago, were vociferously defending hip screws or nail-plates.
The technique described in this paper derives from our experience with over 2,000 Gamma nails implanted since 1987.
In order to cater for all cases, including fractures involving the femoral shaft, the nail comes in a Standard and a Long version. Very recently, the range has been expanded to include also a Trochanteric nail.
The Standard Gamma nail comes in 3 diameters (11mm, 12mm, and 14mm). For several years now, the overwhelming majority of patients in our Department are managed with 11mm diameter nails. In order to streamline the range, it was, therefore, decided to supply the Long Gamma and the Trochanteric Gamma nails in an 11mm diameter version only. All the nails have a proximal diameter of 17mm.
The length of the Standard nail is 20cm; the Trochanteric nail has been shortened to 18cm (the nail being designed exclusively for the management of trochanteric fractures). We feel that this length is sufficient for the treatment of such fractures, and that too long a nail might damage the anterior cortex when using a nail without a sagittal curvature. If the fracture extends into the shaft, or with pathological fractures, the Long Gamma nail should be used. This nail comes in lengths from 36cm to 44cm.
The three nails are available with three different lag screw entry angles (125°, 130°, 135°). We have found the 135° angle to be required in very rare cases only.
The lag screw has a diameter of 12mm, and comes in 85mm to 120mm lengths. It is locked by a set screw introduced with the aid of the targeting device, which will allow the lag screw to slide to and fro but will prevent it spinning around its axis.
The distal locking screws have a diameter of 6.28mm; their lengths range from 25mm to 100mm (for the Long Gamma nail).
In order to avoid complications, this technique MUST be followed step by step. Each individual step is important; we feel that the first two steps in the sequence - patient positioning and fracture reduction - are crucial to the success of the procedure.
The patient is positioned supine on a fracture table. Most of our trochanteric fracture cases are operated on under spinal anaesthesia. The foot on the injured side is placed in the foot holder of the fracture table.
Reduction is performed as follows: Slight traction is exerted in the anatomical axis of the limb, WITHOUT any abduction or adduction, and in slight internal rotation. Rotation will depend on the pattern of the fracture to be reduced. (Some fractures in internal rotation - such as Ender IV fractures - will reduce in slight external rotation.) If the leg is correctly positioned, the patella should be looking straight up.
The patient’s trunk is tilted towards the unaffected side, to allow access to the trochanteric region and to tighten the gluteals, which will also help to reduce the fracture. The trunk is maintained in position by a well-padded chest support, to prevent compression and pressure sores (Fig. 1).
The unaffected limb is strongly abducted, to allow enough space for the image intensifier. The intensifier must be positioned in such a way as to give optimum visualisation of the trochanteric region on a.p. and lateral views; the axis of rotation of the intensifier must be centred on the femoral neck. In our Department, two intensifiers are used, for the sake of convenience (Fig. 2).
For the reduction of fractures extending into the femoral shaft (to be managed with a Long Gamma nail), we prefer to use a rigid traction stirrup on a Steinmann pin, rather than the foot holder of the fracture table. The Steinmann pin is inserted immediately preoperatively, through the femoral condyles or even through the tibial tubercle, if the femoral shaft fracture is very distal (Fig. 3).
As stated above, reduction is performed with traction on the straight, slightly internally rotated leg, with the patella pointing upwards.
In some patients - especially the obese -, reduction may be somewhat difficult: the weight of the thigh tends to drag the femoral shaft downwards. This problems may be solved by using two tricks, which may be employed together: firstly, a lateral support may be placed under the lower thigh, which will push the shaft upwards and allow it to be realigned with the proximal metaphysis on the lateral view. Secondly, the proximal region may be adjusted manually as the Gamma nail is being introduced.
Another difficulty may be encountered, especially with so-called steeple pattern of subtrochanteric fractures. In these cases, the anterior portion of the proximal fragment will tend to displace in flexion, because of the pull of the psoas muscle (Fig. 4). Through the same incision, we use a Wagner spoon over the anterior portion of the proximal fragment, so as to push the fragment back towards the shaft fragment until the lag screw has been inserted (Fig. 5).
Once reduction has been obtained, the nail to be inserted can be determined. As stated above, we use an 11mm nail in virtually all our cases (the Trochanteric and the Long Gamma nail are available in this diameter only). What has to be decided, therefore, is the lag screw entry angle. The 135° angle will be used only rarely, in cases of coxa valga. The choice therefore is between an angle of 125° and one of 130°. It may be useful to place a protractor on the a.p. reduction radiograph (providing that the film was taken with 0° femoral neck anteversion). We would use nails with a 125° angle for coxa vara patients or in cases of massive osteoporosis, and 130° angle nails in all the other patients.
Draping - Incision
Draping is very straightforward, since we use two image intensifiers, which avoids any repositioning during the procedure.
The skin is prepped in customary fashion, and a single sterile self-adhesive drape is applied to the side of the thigh, care being taken to ensure that a space is left between the anterior superior iliac spine and the middle of the thigh. This occlusion drape will cover the image intensifiers (Fig. 6).
The incision is started over the tip of the greater trochanter. The trochanter is identified by finger palpation or with fluoroscopy, using a pin placed over the front of the hip (Fig. 7). The length of the incision will depend upon the patient pattern; most commonly, it will be between 5cm and 8cm (Fig. 8). After the skin and the subcutaneous tissues have been incised, the fascia is incised in the direction of its fibres, and a self-retaining retractor is inserted.
Nail entry point
This is the same as the point described for femoral nailing by Küntscher, in 1939 - i.e. the tip of the greater trochanter. The tip is palpated, and an awl is introduced under the surgeon’s index finger to enter the tip of the greater trochanter. Placing the awl in the digital fossa is not only more difficult to perform, but may damage the blood supply to the femoral head and violate the joint capsule. The nail entry point described above is used in ALL cases, even if there is a comminuted fracture involving the greater trochanter or if there has been major bone loss (metastases). In case of doubt, a check may be made with fluoroscopy (Fig. 9).
Placement of reamer guide wire
When the entry point has been made, the reamer guide wire Is placed in position. In obese patients, especially, wire insertion is made easier if the wire is pre-curved. In the majority of cases, medial rotation of the guide will prevent the guide wire coming out of the fracture posteriorly. Most trochanteric fractures are associated with posterior comminution (Fig. 10).
The guide wire is advanced down to the condylar region, to prevent it coming out during reaming. A check may be made with fluoroscopy, to ascertain that the guide wire is in the correct position.
Reaming is performed in customary fashion, as for conventional intramedullary nailing, going up in 0.5mm increments. Obviously, in severely osteoporotic patients with wide femoral canals, reaming may be done “by hand”, with the motor switched off. We use the classical Küntscher reamers, which are still the best available (Fig. 11). In the shaft, reaming is continued to a diameter of 2mm above that of the chosen Gamma nail. Thus, with our policy of using 11mm nails, we ream the shaft to a diameter of 13mm or 14mm. In young patients, and especially if the trochanteric region is intact, reaming should be continued to a diameter of 17mm over the first 6cm. All these reaming details are of the utmost importance, since the Gamma nail is pushed in by hand, rather than tapped in with a mallet.
Once the nail has been chosen after reduction, it is advisable to test the implant and the instruments (or to have them tested by the operating department assistant). This will ensure that everything that is required for nailing and proximal and distal locking has been checked once more prior to insertion.
The selected nail is mounted on the carbon fibre targeting device, making sure that the locating peg engages the corresponding notch in the nail. The nail and targeting device are locked together by tightening the nail holding bolt with the socket wrench and the screwdriver for the nail holding bolt.
The nail is pushed in BY HAND, without the aid of a mallet, inserting it directly over the guide wire. Thus, in contrast to the conventional intramedullary nailing technique, there is no need to exchange the guide wire. Nail insertion must be done gently, pushing the nail on its carbon fibre targeting device, and twisting it from side to side (Fig. 12).
If the nail happens to get stuck as it is being inserted, or if it tends to go into excessive external rotation, it should be removed, and one or two further reamers should be used. Under no circumstances must a mallet be used, since hammering in the nail may damage the cortices.
Once the nail is in the desired position, the guide wire must be removed before the next step is performed.
Lag screw insertion
Before the start of lag screw insertion, a check must be made to ensure that the nail is correctly positioned in the femur. There are two useful clues. Firstly, there is a narrowing between the targeting device and the proximal part of the nail. This waist must be seen on the image intensifier to be level with the tip of the greater trochanter. Secondly, the lag screw holes may be used to check the position of the nail. On the a.p. view, these holes must line up with the axis of the femoral neck.
Since the nail has been pushed in by hand, its position may readily be changed if it is found to have gone in too far or not far enough.
For lag screw positioning, the metal targeting sleeve corresponding to the chosen angle is used (Fig. 13). Attention: At this stage, the targeting sleeve thumbwheel has not yet been tightened. The serrated guide sleeve for the lag screw and the soft tissue protector are assembled and passed into the targeting sleeve, and advanced down to the skin.
A stab incision is made and the guide sleeve/tissue protector assembly is advanced down to the bone. The serrated guide sleeve is left in contact with the cortex, while the blunt soft tissue protector is withdrawn. At this point, the thumbwheel on the targeting sleeve is tightened, to prevent the serrated guide sleeve becoming dislodged.
The awl is inserted, and applied to pierce the lateral cortex. Once again, there is no need for a mallet, since the handle of the awl has been designed in such a way as to fit snugly into the surgeon’s hand (Fig. 14).
When the lateral cortex has been pierced, the soft tissue protector is re-inserted in the guide sleeve. The lag screw guide wire, which is threaded over the last centimetre, is inserted using the Jacob’s chuck. A check is made with a.p. and lateral fluoroscopy (Fig. 15).
This check may indicate the need for changing the position of the nail in the coronal or the sagittal plane. If the lag screw guide wire is too high or too low in the femoral neck, it should be withdrawn, and the nail repositioned downwards or upwards. Equally, if the lateral view shows the lag screw guide wire to be too far forward or backward, it should be removed, and the rotation of the Gamma nail corrected by moving it more posteriorly or anteriorly. Since the Gamma nail has been inserted by hand, these changes will be quite straightforward.
Once any necessary changes in the position of the nail have been made, the lag screw guide wire is inserted, care being taken to ensure that it does not go beyond the subchondral bone.
The length of the lag screw to be used is determined with the measuring gauge, having made sure that the lag screw guide sleeve is against the cortex (Fig. 16).
The length is read on the gauge, and transferred to the step drill, whose stop is adjusted in such a way as to have the length displayed on the side facing the drill tip (Fig. 17).
The drill is used with the Jacob’s chuck. A power drill would be used only if the bone is very hard, as it would be in younger subjects or in the case of necrosis of the femoral head.
Drilling is continued until the drill stop contacts the serrated guide sleeve (Fig. 18). At this point, the tip of the drill will be at the start of the threaded portion of the lag screw guide wire. This can be ascertained, if need be, on the image intensifier screen.
A lag screw of a length corresponding to that indicated on the gauge is inserted. For this purpose, the screw is fitted in the lag screwdriver. This screwdriver is threaded in its proximal part and also has a compression device at this site. It will be seen that the distance between the end of the threaded portion of the screwdriver and its distal part is exactly the same as the length of the serrated guide sleeve. This means that once the threaded portion of the screwdriver is in contact with the guide sleeve, the lag screw will be ideally placed in the femoral head.
The lag screw is inserted. When it has been screwed home, a check must be made to ensure that the handle of the screwdriver is parallel with (or at right angles to) the targeting device, so as to have one of the locking grooves correctly lined up to engage the set screw (Fig. 19).
The set screw is inserted with the hex screwdriver fitted onto the socket wrench. It is inserted through the carbon fibre targeting device, and screwed onto the lag screw (Fig. 20).
The set screw is screwed home, and then unscrewed one quarter-turn. The action of the set screw may be tested using the lag screwdriver: if, after the set screw has been inserted, one tries to turn the lag screw without being able to, the set screw may be taken to be working.
All the instruments used for lag screw and set screw insertion, other than the metal targeting sleeve, are now removed.
Distal targeting is performed using the targeting device with a double sleeve assembly, which has greatly reduced the risk of misdrilling at this site.
Prior to distal drilling, a check is made to ensure that the targeting device is securely fixed to the nail, so as not to have any inadvertent movement while the locking is being performed.
The distal sleeve is used through the targeting device; it permits a minimal skin incision. Through this incision, the sleeve is pushed down against the cortex (Fig. 21).
The second sleeve, colour-coded blue, is then used directly. We think that the use of an awl is dangerous, because of the risk of causing intraoperative microfractures, which may be missed. We therefore stopped using a distal awl several years ago. The drill, which is marked with a blue ring, is used without a previous starter hole having been made; the drill is inserted through the second sleeve (Fig. 22).
The length of the screw to be used (fully threaded 6.28mm diameter screw) is obtained from the distal depth measuring gauge, which is used after the removal of the second sleeve. The measurement obtained relates to the threaded length of the screw, taking no account of the screw head and tip.
The most commonly used locking screws are 25mm or 30mm long.
For the Long Gamma nail, targeting cannot be done using the carbon fibre targeting device. (Attempts to use a “stretched” targeting device have been unavailing.) Therefore, the technique used is the customary one employed for conventional locked nailing. Many surgeons use the free-hand technique, with a hand-held targeting device. We still use the targeting device first described, in the 70s, by Grosse and Laforgue, with which we are entirely satisfied. This sterile targeting device is mounted on the intensifier by the surgeon (Fig. 23).
Targeting is performed by the radiographer handling the intensifier, while the surgical team keep out of the radiation field. This is the only way of free-hand targeting that is perfectly safe for the surgical team.
The wound is closed in customary fashion over a suction drain, which should be placed in the subcutaneous tissues so as to prevent inappropriate suction (such as may occur if the drain is placed inside the nail body).
The patients are out of bed on the first postoperative day, and walking with weight-bearing is resumed on the third postoperative day, in the overwhelming majority of cases (more than 85% of the patients in our series). Also, we have learned that the time to weight-bearing is independent of the fracture pattern (stable or unstable fractures). Patients who do not progress to weight-bearing do so because of their poor general condition, and not for reasons related to the intramedullary nailing that they have undergone.
Maîtrise Orthopédique n° 75 - June 1998
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