**2. Biplane double-supported screw fixation method - Operative technique**

*Indications:* Fractures of the Garden types from I to IV. The indications and contraindications for application of the BDSF-method are generally the same as of the conventional methods for fixation of the femoral neck fractures. The BDSF-method significantly expands the indications for application of screw fixation in terms of the bone, changed by osteoporosis. The method is most useful and has no reasonable alternative in adult patients above 80 years with a high cardiopulmonary risk, as in patients with severe concomitant diseases, inclusively some mental diseases, patients with senile dementia, and others, for which the primary joint replacement may be contraindicated.

*Implants:* 7.3 mm self-tapping cannulated screws

82 Injury and Skeletal Biomechanics

head fragment, being only one [8,9,10].

solidity of the cancellous bone. This circumstance results in high failure rate in cases of osteoporosis. (2) *Lack of sliding phenomenon*. Upon body weight loading, in the process of the subsequent wedging of the osteoporotic cancellous bone in the fracture site, the screws of traditional methods of fixation, which lack two-point cortical support, cannot effectively slide distally and laterally keeping unchanged their angle towards the axis of diaphysis, and rather have expressed tendency to displace in varus, with fixation failure. (3**)** *Inability to move the entry point of the screws distally into the solid diaphyseal cortex, and simultaneous placing of three parallel screws*. In 1961 Garden [7], like other authors before, further developed the concept that the implants must have more vertical placement, similar to the direction of the medial compression lamellae of the femoral neck internal trabecular system, in order to provide resistance to the shearing forces. However, when developing this concept, the classic authors used only one implant (a nail). Thus the implant successfully provided resistance to the shearing forces, but it did not create compression between the fragments, because it is not a screw and it is also not able to ensure reliable rotational stability of the

The anatomy of proximal femur does not allow simultaneous placing of three screws, which are parallel to each other, and lie near the cortex in the periphery of the femoral neck and, at the same time, have their entry points positioned distally, in the solid cortex of the

When applying the *conventional* methods of positioning three parallel screws, in case movement of the screw entry point distally is attempted, the screws will be placed at a very obtuse angle towards the diaphysis and obliquely to the femoral neck. By increasing the angle of penetration, the surface of the femoral neck cross-section decreases geometrically, and in practice the placement of more than one or two screws is hard to be accomplished. However, a two-screw fixation does not provide reliable stability in all planes [10]. Both problems are resolved by the newly introduced method of *Biplane Double-supported Screw* 

The *Biplane Double-supported Screw Fixation Method in femoral neck fractures (BDSF-method)*, developed by O. Filipov, is a new method of screw fixation in femoral neck fractures, based to *an original concept of the establishment of two supporting points for the implants and their biplane positioning* in the femoral neck and head. The console-like proximal femur requires the fixation screws to have to support the weight-bearing head fragment, acting like a *beam with an overhanging end*, which must have two points of support in the distal fragment. The concept of the Biplane Double-supported Screw Fixation (BDSF) method is based on this principle. This method is original with the three screws being laid in two planes, which aspect allows the entry points of two of the implants to be placed much more distally, in the solid cortex of the proximal diaphysis, and also to lean onto the strong femoral neck distal cortex. Thus, we establish two points of support. The achieved by this method position of the distal screw and the middle screw as well, in view of statics, turns them into *a simple beam with an overhanging end, loaded by a vertical force*. This beam with an overhanging end successfully supports the

diaphysis, in order to avoid the fragile lateral metaphyseal cortex.

*Fixation* trough the concept of biplane positioning of the implants.

head fragment, bearing the body weight and transferring it to the diaphysis.

*Reduction:* Mild traction, slight abduction and internal rotation of the limb are applied. Only anatomical reduction is acceptable.

*Approach*. A straight lateral incision, starting at the level of the lower border of the greater trochanter, with distal length of 6 to 10 cm. A stripping of the periosteum of the lateral diaphysis at 6-7 cm is performed.

*Placement of the implants.* When applying the BDSF-method, the three cannulated screws are placed in the frontal plane at a highly increased angle. Both the distal and the middle screws touch tangentially on the curve of the distal femoral neck cortex (Fig.1-a.). At internal rotation of the leg, in anteroposterior view, the projection of the distal screw usually crosses the projections of the other two screws, thus forming the letter F (F-technique). Via the concept of *biplane positioning*, developed by the BDSF-method, the three screws are placed in two vertical oblique planes (in lateral view). The two planes diverge towards each other in the direction of the femoral head, and are oblique towards the frontal plane. The distal screw is laid in the dorsal oblique plane. The middle and the proximal screws are placed in the ventral oblique plane (Fig.1-b.).

First of all, we lay the guiding wire for the distal cannulated screw. Its tip is placed at 5-7 cm distally from the lower border of the greater trochanter in the anterior one-third of the surface of the stripped off diaphysis. It is directed proximally at an angle of 150 – 165° towards the diaphyseal axis, with inclination from anterodistally to posteroproximally, so that after it touches tangentially on the curve of the distal femoral neck cortex, the wire goes into the dorsal third of the femoral head.

The middle guiding wire is placed secondly. The entry point is at 2 to 4 cm proximally from the entry point of the distal wire, but in the dorsal one-third of the stripped off surface of the diaphysis. This wire is placed at an angle of 135-140° towards the diaphyseal axis and inclined from posterodistally to anteroproximally, so that after it touches tangentially on the curve of the distal femoral neck cortex, the wire goes into the front one-third of the femoral head. In the frontal plane (anteroposterior view) the tip of this guiding wire goes into the distal one-third of the femoral head.

Biomechanics of the Fractured Femoral Neck –

The New BDSF-Method of Positioning the Implant as a Simple Beam with an Overhanging End 85

angle of penetration. For this purpose we use the same hole in the lateral cortex, by taking out the wire completely and after a change in the direction of the wire, we try by the highspeed rotating trocar tip to change the direction of the channel in the cortical hole, in order to achieve the necessary angle of the wire through the bone. Sometimes, it is necessary to leave the old hole and to bore anew next to it. Sometimes, although very rarely, that is not sufficient and release from the thick lateral cortex is required, by reaming around the placed in poor position guiding wire by the 4.5 mm cannulated reamer. Thus the wire is freed from its contact with the lateral cortex in the created opening of 4.5 mm and is easily directed in

The placing of screws under very oblique angle requires following of the principle for their two-plane positioning and none of the screws must be placed in the central part of the femoral neck and head (in profile projection). If some of the screws are placed in the central part of femoral neck, it will be an obstacle for placing of the other two screws. The distal screw, which is more obliquely placed, must be located in the posterior part of the femoral neck and head. If in violation of BDSF-technique it is placed in the anterior part of the femoral head, then because of the physiological anteversion of the femoral neck, it will be difficult or impossible for the other two screws to be placed in the posterior part of the femoral neck, because there is a tendency to find them too marginally at the cortex of the

*Postoperative period.* Limited weight bearing for 4-6 months, by using two crutches would be

This method's innovation is laying of the three screws in two planes, which allows for the entry points of two of the implants to be placed much more distally, in the solid cortex of the proximal diaphysis, and also to lean onto the femoral neck distal cortex. Thus we establish two points of support. The solid distal cortex of the femoral neck acts as a medial supporting point for the screws, which works under pressure - *supporting point A*. The entry points of two of the screws (the distal and the middle one) in the thick cortex of the diaphysis, ensure a second solid supporting point for the screws – a lateral one, which works under tension (or pressure in proximal direction) - *supporting point B*. The position of the distal screw as well as of the middle screw, which are achieved by the method, in terms of the *statics*, turns them into *a simple beam with an overhanging end, loaded by a vertical force.* This beam with an overhanging end successfully supports the head fragment, bearing the body weight and transferring it to the diaphysis. Furthermore, due to the biplane placement, enough space for a third screw is provided, unlike the classic authors' models, where just one or maximum two implants are placed at an obtuse angle [7,11]. Another advantage of the

the necessary direction.

femoral head.

*Radiographic time:* from 0.2 to 0.3 minutes *Mean operative time:* 39 min (30 to 45 min)

**3. Biomechanical basis of the BDSF-method** 

perfect, if the patient is cooperative.

**Figure 1.** Radiography. a. Anteroposterior view; b. Lateral view.

Last to be laid is the proximal guiding wire, with its entry point at 1-2 cm proximally from the entry point of the middle wire, in the dorsal one-third of the stripped off diaphysis, close to the lower border of the greater trochanter. Placed parallel to the middle wire, the proximal wire also goes into the front one-third and into the proximal one-third of the femoral head.

Afterwards we drill and place the screws one by one. Before placing the middle and distal screws, we overdrill their holes in the thick lateral cortex by using a 7.0 mm cannulated reamer.

The middle and the proximal screws are placed first, because they are perpendicular to the fracture surface. Next we release the foot traction, and a repeated impaction of the fracture with an additional tightening up of the screws follows. We perform the impaction gently by hammering on a plastic impactor on the diaphyseal cortex. Finally, the distal screw is placed.

The guiding wire easily changes its initial direction when passing through the thick diaphyseal cortex, therefore its tip is guided into the necessary direction by the surgeon's free hand with the help of a cannulated instrument.

When we place the two distal guiding wires tangentially over calcar femorale, if we suddenly feel resistance, it indicates that the tip has got into the medial diaphyseal cortex distally from the femoral neck. In such a case we change the direction by increasing the angle of penetration. For this purpose we use the same hole in the lateral cortex, by taking out the wire completely and after a change in the direction of the wire, we try by the highspeed rotating trocar tip to change the direction of the channel in the cortical hole, in order to achieve the necessary angle of the wire through the bone. Sometimes, it is necessary to leave the old hole and to bore anew next to it. Sometimes, although very rarely, that is not sufficient and release from the thick lateral cortex is required, by reaming around the placed in poor position guiding wire by the 4.5 mm cannulated reamer. Thus the wire is freed from its contact with the lateral cortex in the created opening of 4.5 mm and is easily directed in the necessary direction.

The placing of screws under very oblique angle requires following of the principle for their two-plane positioning and none of the screws must be placed in the central part of the femoral neck and head (in profile projection). If some of the screws are placed in the central part of femoral neck, it will be an obstacle for placing of the other two screws. The distal screw, which is more obliquely placed, must be located in the posterior part of the femoral neck and head. If in violation of BDSF-technique it is placed in the anterior part of the femoral head, then because of the physiological anteversion of the femoral neck, it will be difficult or impossible for the other two screws to be placed in the posterior part of the femoral neck, because there is a tendency to find them too marginally at the cortex of the femoral head.

*Radiographic time:* from 0.2 to 0.3 minutes

84 Injury and Skeletal Biomechanics

femoral head.

reamer.

placed.

**Figure 1.** Radiography. a. Anteroposterior view; b. Lateral view.

free hand with the help of a cannulated instrument.

Last to be laid is the proximal guiding wire, with its entry point at 1-2 cm proximally from the entry point of the middle wire, in the dorsal one-third of the stripped off diaphysis, close to the lower border of the greater trochanter. Placed parallel to the middle wire, the proximal wire also goes into the front one-third and into the proximal one-third of the

Afterwards we drill and place the screws one by one. Before placing the middle and distal screws, we overdrill their holes in the thick lateral cortex by using a 7.0 mm cannulated

The middle and the proximal screws are placed first, because they are perpendicular to the fracture surface. Next we release the foot traction, and a repeated impaction of the fracture with an additional tightening up of the screws follows. We perform the impaction gently by hammering on a plastic impactor on the diaphyseal cortex. Finally, the distal screw is

The guiding wire easily changes its initial direction when passing through the thick diaphyseal cortex, therefore its tip is guided into the necessary direction by the surgeon's

When we place the two distal guiding wires tangentially over calcar femorale, if we suddenly feel resistance, it indicates that the tip has got into the medial diaphyseal cortex distally from the femoral neck. In such a case we change the direction by increasing the *Mean operative time:* 39 min (30 to 45 min)

*Postoperative period.* Limited weight bearing for 4-6 months, by using two crutches would be perfect, if the patient is cooperative.
