(DHS) Implant System2022-03-30 2022-03-30 15:03
(DHS) Implant System
(DHS) Implant System
3 DRS Implant System
The DRS implant system is composed of the DRS plate and the DRS lag screw.
The plates are available with two types of barrels: a standard barrel (38 mm) and a short barrel (25 mm).
The short barrel plates are seldom indicated; their gliding characteristics are far less satisfactory than those of the standard barrel plate.
Their use should be limited to especially small femurs and to the rare cases where a long impaction distance is to be expected and where the screw might “run out of glide” with a standard barrel. In cases where medial displacement osteotomy is carried out, the use of the short barrel might be advisable.
The DRS plates are produced with several barrel angles (135°, 140°, 145°, 150°), but in the great majority of cases a 135° plate is best. It must be realized that the technical problems of correct placement of the implant increase with greater plate angles, although greater angles may offer biomechanical advantages (better gliding characteristics, reduction of bending stresses on tube-plate junction), particularly in unstable cases. A wide selection of plate lengths (2, 4, 5, 6, 8, 10, and 12 holes) for the 135° (and the 150°) plates helps the surgeon in adapting to various fracture situations. The 140° and 145° plates exist in only three lengths (4, 5, and 6 holes). Lag screws are available from 50 mm up to 145 mm in length, in 5-mm increments.
Standard Surgical Technique
Trochanteric Fracture – 135° DRS
The operation is performed with the patient in a supine position, and we prefer the use of a regular operating table. The patient may be placed on a fracture table, although this takes more time and to us seems rather a disadvantage, particularly for the comminuted fracture types, because it may render reduction quite difficult.
One image intensifier is indispensable and allows for axial as well as AP viewing;
some authors, however, prefer two image intensifiers.
The extremity is draped freely in order to facilitate manipulation of the leg.
Using traction, abduction, and internal rotation, and sometimes slight flexion about the knee, even very severely dislocated and comminuted fractures can be reduced.Without the fracture table a temporary fixation of the reduced fragments 6 DHS Implant System with one or two Steinmann pins is advisable.The results of the reduction manoeuvers can be checked by means of the image intensifier.
The proximal femur is exposed by means of a straight lateral incision on the thigh, beginning at the greater trochanter and running toward the lateral femoral condyle, the length depending on the size of the DHS plate chosen. The fascia lata is split in the same direction. The origin of the vastus lateralis is incised in its posterior half and along the linea aspera. The proximal femur is now exposed by reflecting the vastus anteriorly. Any perforating vessel must be identified and ligated. Usually no further exposure of the fracture is required.
To determine the anteversion of the femoral neck a solid Kirschner wire is slid over the front of the femoral neck, using the appropriate angle guide with the T -handle, and hammered slightly into the head (Fig. 2).
The point of introduction of the guide pin is determined preoperatively on the X-ray of the fracture. The level varies with the angle of the plate to be used.
In the great majority of cases, when a 135° plate is used the guide pin is introduced at a point approximately 2.5 cm below the tuberculum innominatum (the rough line of the greater trochanter). The lesser trochanter can also be used as a landmark. The middle of the lesser trochanter would usually be the entry point for a 135° plate. The angle guide is placed against the middle of the femoral shaft with the guide tube pointing to the center of the femoral head. The lateral cortex is opened with a 2-mm drill (optional). The DHS guide pin is inserted in the center of the femoral head to the level of subchondral bone.
The pin must remain in place throughout the procedure. The threaded end of the guide pin helps to prevent accidental backing out (Fig. 3).
If the guide pin is inadvertently withdrawn it must be reinserted. A correct repositioning is possible using the short centering sleeve and a DHS lag screw inserted backward in the centering sleeve as guides (Figs. 4, 5). If the guide pin is not correctly reinserted there is a considerable risk of placing the lag screw in a wrong direction, away from the original bore hole, especially in porotic bone .
The exact placement of the guide pin into the center of the femoral head is the most important step of the surgical procedure. If the guide pin lies correctly and the operative technique is followed as described, major technical problems are unlikely to occur during the rest of the procedure.
The guide pin must lie in the middle of the femoral neck; its position must therefore be checked radiographically in both AP and axial views (Figs. 6, 7). If a fracture table is used the axial X-ray is somewhat impractical to take. Without the fracture table the axial view may be obtained by a 90° flexion, 30° abduction, and slight external rotation of the hip, with the image intensifier pointing in the AP direction (Fig. 7). (In these cases the fracture must of course be secured by one or two Steinmann pins placed cranialy to the future DHS position.
To minimize the