The management choice in the vast majority of patients with undisplaced fractures, irrespective of age or other factors, is internal fixation. This is best achieved with either a cannulated screw system or a sliding hip screw device with a short plate. In a meta-analysis, there was a single nonunion (0.9%) in 118 young adults with undisplaced intracapsular femoral neck fractures managed with internal fixation [1]. The same study found the overall rate of AVN to be 5.9%, highlighting the need for patients to be kept under review for up to 2 years to detect this [37–39]. Most patients with healed fractures have a good functional outcome and can return to their pre-injury level of mobility.

The majority of intracapsular neck of femur fractures are displaced, and the management principles are very different in physiologically younger and active patients when compared to their frailer elderly counterparts. For an elderly patient, the goals are to restore mobility with early weight bearing and to reduce the complications seen with prolonged bed rest. This is often best achieved with a hemiarthroplasty or total hip replacement. For a physiologically young and active patient, the aims are to preserve the femoral head, achieve union and prevent AVN. Other than in patients with a very limited life expectancy, these injuries are not amenable to nonoperative treatment. Anatomic reduction and stable robust internal fixation are essential for a good outcome [40].

The important factors to consider when deciding whether to undertake an open reduction and internal fixation of a displaced femoral neck fracture are the patient’s chronological and biological age, pre-injury level of activity, medical comorbidities and the fracture morphology. Anatomic reduction and internal fixation are the treatment of choice for most young patients with a displaced femoral neck fracture, with good results achieved in the majority of patients. Rates of nonunion are between 0% and 15.6% and AVN between 10% and 46% (Table 5.1). A meta-analysis reported the overall rates of nonunion and AVN to be 8.9% and 23%, respectively, with a rate of 6.0% and 22.5%, respectively, for displaced fractures [1]. Patients can anticipate a good functional outcome with a healed femoral neck fracture that does not progress to AVN [41–47]. The ability to achieve a good outcome by attaining an anatomic reduction and avoiding fixation failure depends on several factors that the surgeon can control [45, 48–50].

As already noted, approximately half or more of young patients with displaced femoral neck fractures are between 40 and 60 years of age. This patient group may have medical comorbidities predisposing them to hip fractures including chronic diseases associated with osteoporosis and osteomalacia [8]. Smoking is a significant risk factor for hip fractures in women under 65 years of age [51]. A large study from Edinburgh determined the risk factors for failure after internal fixation in patients under the age of 60 with displaced intracapsular neck of femur fractures [5]. In a retrospective series of 122 patients, union occurred in 83 (68%), with failure more frequent in patients aged between 40 and 60 years (37/104, 36%) than those under 40 years (2/18, 11%). The authors identified respiratory disease, alcohol excess and renal disease as independently predictive of failure on multivariate analysis. In younger patients with a history of alcohol abuse or significant other medical comorbidities, arthroplasty can be considered.

There is controversy surrounding the timing of surgery for displaced intracapsular fractures in young adults. In theory, early reduction and stabilization should allow timely re-establishment of the retinacular vessels to potentially restore blood flow to the femoral head and minimize the potential risk of AVN. However, some would argue any damage to the vessels is done at the time of injury and early intervention may not improve this.

One study compared fixation within 12 h of injury with delayed fixation (>12 h) and reported the rate of AVN to be 16% in the delayed group compared with 0% in the early fixation group [52]. However, Barnes et al. found that the timing of surgery did not affect the rates of nonunion and AVN in patients treated with reduction and fixation within the first week post-injury [14]. Experimental studies have also demonstrated that whilst cellular changes occur in the femoral head within the first 6 h postfracture, osteocyte cell death occurs more slowly and may not be apparent until 2–3 weeks following injury [53]. In the face of contradictory evidence, a sound and safe approach is to operate as soon as an appropriately skilled surgeon and equipped theatre are available. This may be on the day of injury or the following morning but probably need not be in the middle of the night. Fixation should still be considered in patients who present late (up to 1 or 2 weeks following injury), although an imperfect reduction may have to be accepted.

To reduce the fracture, gentle traction and internal rotation are applied to the leg. Fracture reduction is assessed on both the AP and lateral images, with the convex femoral head-neck junction producing an S-shaped curve in all planes. There is a debate about what represents an adequate reduction, but a 20° varus malreduction is associated with a 55% risk of failure, and less than 10° of posterior angulation is recommended to minimize this complication also [54, 55].

There is a relationship between quality of reduction and AVN. The risk is lowest with an anatomic reduction and increases with either valgus or varus malreduction [56]. An open reduction is sometimes necessary if an acceptable reduction cannot be achieved with closed techniques. This is most conveniently done on traction. A two-incision approach is recommended:

Post-surgery, patients can be mobilized touch weight bearing for a total of 6 weeks. Union of a femoral neck facture is slow and routinely takes longer than 6 months in most cases [14]. AVN is a late complication, usually presenting postfracture union, and is most common in the second year after injury [14]. It is recommended that patients should be kept under clinical review with regular radiographs for 2 years to detect this complication.

There is a rise in intracapsular pressure due to the haemarthrosis that arises from an intracapsular fracture, and this can cause a tamponade effect which might impede blood flow to the femoral head [57–59]. For this reason, aspiration or capsulotomy to decompress the haemarthrosis seems a sensible option [40]. Despite this, the efficacy of these techniques has not been clearly demonstrated in clinical studies, and whilst there remain advocates, aspiration or capsulotomy is now rarely recommended [14, 60, 61].

There is no definitive consensus on the optimal device for fixation of displaced intracapsular fractures in young patients, with either cannulated screws or a sliding hip screw commonly used. Both these techniques allow controlled linear compression at the fracture to promote union. More rigid methods of fixation, such as blade plates and locked plate systems, have an increased risk of cut-out with repetitive loading [62]. The disadvantage of implants that allow compression is that shortening of the femoral neck can occur and this may have an effect on abductor biomechanics, joint reaction force and ultimately gait. Stockton et al. reported on 65 patients under the age of 60 years old who underwent internal fixation, with 32% having leg shortening of more than 1 cm [63]. Femoral neck shortening and loss of offset may be associated with poorer functional outcomes in younger patients [64, 65].

Three cannulated screws are more stable than two, but there is no additional advantage known in using four [66, 67]. There is controversy regarding the optimal position of screws, particularly whether they should be divergent or parallel, but there is no strong evidence to prove that position greatly influences outcome. However, we advocate the use of three partially threaded cannulated screws in the configuration found in Fig. 5.3. It has been suggested that a fully threaded posterior screw could improve stability in a commonly comminuted and length-unstable region of the fracture. This would prevent posterior angulation and give controlled compression in the anteroinferior region. Schaefer et al. performed a biomechanical study using a saw bone femora and reported this proposed construct to have higher bending stiffness and less failure compared to three partially threaded screws, although there are no clinical studies analysing this [68]. Vertically orientated Pauwels’ type III fractures have a tendency to fail through shear, and there is some evidence that they should be fixed with a sliding hip screw and a short plate rather than with cannulated screws [21].