A femoral neck fracture has multiple facets and it is important to understand all aspects of this problem.
An Example
A 40 year old patient had a displaced femoral neck fracture, fixed with multiple cancellous screws about 9 months ago. The patient still has persistent groin pain. They cannot bear full weight on this hip. They have a painful limp, antalgic gait, and difficulty walking. X-rays are not clear and show a possible nonunion. On the other hand, a CT scan shows the nonunion with some varus angulation. So, what would the treatment be?
The treatment for such a case would be removal of the hardware and valgus osteotomy. However, the scenario can be more complicated if there is a healed femoral shaft fracture along with the nonunion of the femoral neck. In this case, the hardware from both the femur and the screws from the femoral neck fracture should be removed. Valgus osteotomy would then be performed with fixation with a plate, preferably a blade plate, in order to treat the femoral neck nonunion.
Intracapsular fractures of the proximal part of the femur are not common in adults younger than 50 years of age. However, they are associated with a high incidence of avascular necrosis and nonunion. For instance, about 10-30% of femoral neck fractures end up as nonunion after an open reduction and internal fixation is performed. It is usually the vertical fracture pattern that turns into a nonunion, such as Type III in Pauwel’s classification. These fractures are more prone to nonunion due to the shear stress, rather than compression forces across the fracture site. Type IV fractures in the Garden classification are also more prone to nonunion. These fractures are completely displaced, and the greater the displacement, the higher the incidence of nonunion and reoperation rate after fixation of the femoral neck.
Technical Aspects
The inverted triangle pattern of fixation of femoral neck fractures is the pattern that is commonly used with the inferior screw posterior to the midline and adjacent to the calcar. Achieving and maintaining anatomic reduction is important for femoral neck fracture fixation and healing.
Femoral neck fractures are intracapsular, so there will be no abundant callus formation during the healing (healing is intraosseous only). Therefore, it is often difficult to know if the fracture is healed or not. There is also no correlation between age or gender and the rate of nonunion, also making it difficult to know if the fracture is healed. One way to tell is that varus malreduction correlates with failure of the fixation after reduction and cannulated screw fixation.
Posterior comminution of the fracture does not allow stable fixation and can lead to nonunion. The comminution of the femoral neck is usually posterior and inferior. Some surgeons recommend adding a fourth screw in this situation.
High energy fractures often have a worse prognosis for healing, especially in patients with metabolic bone disease and nutritional deficiency. When a femoral neck nonunion after fixation is present, blood work (sedimentation rate and CRP) will need to be done in order to rule out infection.
Clinical Examination and X-rays
For a high angle femoral neck fracture, the patient should be followed closely with clinical exams and x-rays. There might be a varus collapse seen on x-rays. There may also be a femoral neck nonunion seen or a failed internal fixation. The patient will walk with a limp, the limb may be shortened, and the patient may have rotational deformity of the extremity.
Treatment
In young patients with femoral neck nonunion, arthroplasty is not a desirable option. In young patients with a femoral neck nonunion, valgus intertrochanteric osteotomy with plate fixation will produce a good result in the majority of cases; it produces approximately 80% union rate. This procedure makes a vertical fracture more horizontal, converting the shear forces into compressive forces. It is done in a healthy, young patient with no joint arthritis when the femoral head is intact. This procedure also corrects the varus malalignment. Basically, the procedure changes the vertical fracture orientation to a horizontal fracture to achieve compression.
However, there are other procedures done in a young patient, and these include revision open reduction internal fixation with or without bone graft( rarely done), free vascularized fibular graft (done in younger patients with a nonviable femoral head), hemiarthroplasty (done in patients with low physical demand and the articular cartilage is persevere with no evidence of infection), and total hip arthroplasty (done in young patients who are active and the femoral head is not viable, and the patient does not want a free vascularized fibular graft or if the patient had a collapse if the femoral head with nonunion). However, with a total hip replacement, there will be a problem with more dislocations of the hip post-operatively.
