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Femoral neck fractures are common and constitute one of the largest healthcare burdens of the modern age. Fractures within the joint capsule (intracapsular) represent a specific surgical challenge due to the difficulty in predicting the rates of bony union and whether the blood supply to the femoral head has been disrupted in a way that would lead to avascular necrosis. Most femoral neck fractures are treated surgically, aiming to maintain mobility, whilst reducing pain and complications associated with prolonged bedrest.
Femoral neck fractures are one of the biggest diseases of modern times, with lifetime incidences of approximately 1 in 4 for women and 1 in 10 for men . Their prevalence and severity result in vast health and financial burdens; they are the most expensive fractures to treat . Complications remain common given the spectrum of different fracture patterns and the baseline functions of the population affected, and if reoperations are required, mortality rates and financial costs rise considerably .
Most hip fractures occur within the capsule of the joint. These fractures pose specific difficulties because of the risk of disruption to the vascularity of the femoral head which can lead to avascular necrosis (AVN). Outcomes, compared to extracapsular fractures, are thus potentially more dependent on the choice and quality of the operation performed. Focusing on intracapsular fracture types, we aimed to create an evidence-based algorithm for the management of an intracapsular hip fracture.
Fractures within the region of the femoral neck (AO/OTA 31–B1-3) present surgical challenges due to the uncommon vascular supply to that region. The majority of the blood supply to the femoral head enters in a retrograde fashion, predominantly via the lateral epiphyseal artery, a branch of the medial femoral circumflex artery. Healing of intracapsular fractures occurs through primary osteonal reconstruction due to the inability to bone in this region to form external callus. These anatomical factors combine to heighten the risk of nonunion and AVN with these fractures, further worsened by any disruption to the arterial blood supply due to the energy from the initial trauma, and/or ongoing hypoperfusion through malreduction and reduced arterial flow. However, even in the presence of initial arterial damage, fragment stabilization can be sufficient to reduce the risk of AVN, as reduction and stability enable revascularization across the fracture, before AVN and subsequent collapse can occur . Concerns about AVN occurring (including the difficulty in predicting which fractures are more susceptible), fractures not uniting, and the risks from any further operations often justify a more pre-emptive approach in patients with a reduced physiological capacity to deal with such events. This is contrasted with a more accepting stance towards future surgery in young patients , where preservation of the native joint predominates due to both the finite lifespan from articular replacements and the increased demands that an active patient would be expected to have.
Pathological fractures require additional management considerations, in part, due to the lack of healing potential that is required for successful osteosynthesis, alongside presenting other technical complexities such as having reduced quantity and unknown quality of residual bone stock. Therefore, arthroplastic solutions—total hip arthroplasty (THA) or hemiarthroplasty (HA)—are required to restore the patients to their baseline function and to enable mobilization; these operative options have been shown to last longer than fixation treatments . Furthermore, intramedullary procedures may risk generating metastases through embolization of malignant tissue. As further bone destruction can occur after fracture treatment due to the ongoing neoplastic condition, replacement surgery reduces the risk of future reoperation, as may be the case with fixation options. The exception to this is when additional neoplastic lesions within the shaft of the femur would result in stress raisers to an implanted stem. In this instance, cephalomedullary nailing or arthroplasty with concurrent stress-reducing plating are surgical options but require planning on a case-by-case basis. Thorough imaging of adjacent joints is required to assess for other lesions and to ensure that stress raisers are neither encountered nor created intra- or post-operatively.
In the absence of prior symptomatic osteoarthritis (OA), fracture displacement needs to be assessed to determine the operative intervention. Completely undisplaced fractures occur rarely . Though being an imperfect surrogate marker , displacement is thought to correlate with suspected femoral head blood supply disruption, which in turn predicts the rates of AVN; reportedly between 7 and 78%, with younger groups having higher rates, probably reflecting the higher energy that caused their fracture . Displacement needs to be assessed orthogonally. Commonly the Garden classification  (I—valgus impacted, II—undisplaced, III—partially displaced, IV—fully displaced) is used for assessing coronal displacement, though the key distinction needed is whether there is true displacement or not, regardless of whether partial or full. Firstly, as there has not been shown to be a difference in healing rates between Garden III and IV  and secondly, as partially and fully displaced fractures are managed in the same way. Additionally, as the Garden classification is based only on coronal radiographs, lateral images must also be viewed to ensure displacement is not underestimated or missed entirely. Sagittal displacement, typically measured on a lateral radiograph, ≥20° posterior tilt, or ≥10° anterior tilt, has been shown to worsen outcomes when fixed .
Intracapsular hip fractures are heterogeneous both in terms of fracture characteristics and patients they occur in. Using the described algorithm enables an evidence-based approach, addressing the numerous factors that need consideration for optimum management.