For the fixation of trochanteric fractures, the dynamic hip screw (DHS) implant system has been designed. It can also be used for certain subtrochanteric fractures as well as for selected basi-cervical femoral fractures.
The implant is based on the sliding nail principle which allows impaction of the fracture. This is done by the insertion of a wide diameter screw into the femoral head. A side plate, which has a barrel at a fixed angle is slid over the screw and fixed to the femoral shaft. The barrel and the screw each have two matching flats, thus allowing the smooth shaft of the screw to slide within the barrel yet retain rotational stability. The femoral head fragment fixed with the screw can be impacted, either deliberately or from weight-bearing.
The correct placement of the implant is essential for the success. The anteversion of the femoral neck must be determined with guide wire as well as the site of the screw in the middle of the femoral head with a guide pin. The correct position of the guide pin must be checked with two-plane radiography. All steps necessary for the insertion of the implant are performed over the guide pin.
By evaluating the angle subtended between the femoral neck and shaft axes of the uninjured side, the barrel angle can be predetermined. Most commonly indicated angle is 135°.
The dynamic condylar screw (DCS) is like the DHS in its design and concept. The fixed angle between plate and barrel is 95° and the plate is contoured to fit the lateral surface of the distal end of the femur.
Fractures of the distal femur and intercondylar fractures are the main indications. It may also be used for certain intertrochanteric fractures and very proximal subtrochanteric fractures. For the successful application of DCS implant, preplanning the exact site of the screw is essential. For application in the distal femur the axis of the knee joint as well as the inclination of the patellar articular surface of the condyles must be predetermined. Impaction or compression of the fracture is achieved by using the compression screw.