In a fragility fracture context, intra-capsular hip fractures are in fact through the femoral neck, as femoral head fractures are uncommon in the elderly.

Femoral neck fractures are at risk of non-union with/without mechanical collapse due to insufficient fixation and/or avascular necrosis of the femoral head. In adults, the femoral head is primarily supplied by the distal recurrent vessels entering the femur on the shaft side of the fracture. Avascular necrosis is caused by ischaemia hypothetically due to either a direct trauma to the arterial supply crossing the fracture-line or by a temporary arterial impingement, caused by vessel stretching or intra-capsular hematoma. Preoperative scintigraphy, electrode measurement and arthroscopic visualization of ischaemia have been tested but lack prognostic value. Since ischaemia could be temporary, acute reposition within hours (maybe supplemented by hematoma emptying) has been suggested [23, 27].

Femoral neck fracture classification has historically been contentious with several different systems, primarily based on fracture displacement seen in the anterior-posterior radiographs. Garden’s Classification (Fig. 6.2) has in the last half a century been the most widespread. Fractures are divided into four stages based on fracture displacement [16]. Garden’s classification has only fair inter-observer reliability when using all four stages, but moderate to substantial if dichotomized into just undisplaced (Garden I–II) or displaced (Garden III–IV) fractures [17].

In addition, a vertical fracture-line in the anterior-posterior radiograph or posterior wall multi-fragmentation, femoral head size, and posterior tilt angulation seen in the lateral radiograph are believed to influence outcome [12, 25, 42]. However the dualism of undisplaced versus displaced (with reference to Gardens stages I–II versus III–IV) remains the most consistent predictor of failure and the most widespread fracture classification, with respectively around 1/3 and 2/3 of femoral neck fractures [36, 65].

Extra-capsular fractures are at risk of mechanical collapse and non-union due to insufficient fixation. The fracture-line is anatomically located laterally to the nutrient vessels to the femoral head, so avascular necrosis is rarely seen, but muscle attachments often dislocate the fragments and bleeding into surrounding muscles can be severe and life-threatening. Classification systems are primarily based on fracture-line location and number of fragments.

Basicervical fractures are a few percent of borderline cases between the intra- and extra-capsular fractures, anatomically positioned on the capsular attachment line. The AO/OTA classification describes them as intra-capsular, but biomechanically they behave like the extra-capsular fractures [31] – except for the risk of rotation of the medial segment due to lack of muscle attachments.

The AO/OTA Classification (Fig. 6.3) from 1987 is nowadays the most widespread. It divides the 31-A trochanteric area into nine types by severity (1-2-3, each subtyped .1-.2-.3) [32].

Fracture type 31-A1 covers the simple two-part fractures, while 31-A2 demands a detached lesser trochanter, with an intact (31-A2.1) or a detached greater trochanter (31-A2.2-3). 31-A3 covers fracture lines through the lateral femoral wall – defined as the lateral cortex distal to the greater trochanter – in which the subgroup 31-A3.1 represent the reverse fracture and 31-A3.2 the transversal, while the most comminuted 31-A3.3 fracture demands both a fractured lateral femoral wall and a detached lesser trochanter.

The AO/OTA classification covers most fractures within previous classification systems, except the few trochanteric fractures with a detached greater trochanter and an intact lesser trochanter. The reliability when using all nine types is poor, but increases to substantial if only classifying into the three main groups (A1-2-3) [52].

Subtrochanteric fractures are positioned distally to the trochanters, and constitute around 5 % of all hip fractures. These have historically been classified by as many as 15 different systems, most often into the 8 types from 0 to 5 cm below the lesser trochanter by Seinsheimer or the 15 types from 0 to 3 cm in the AO/OTA classification for femoral shaft fractures, the type 32ABC (1–3).1 sub-division. A review doubts the value of such division and proposes simplicity into: (1) a stable two-part and unstable (2) three-part and (3) more comminuted fractures from 0 to 5 cm below the lessor trochanter, without involvement of the trochanters. It however still has to be established whether this easier classification is useful and necessary for decision-making and prognosis [28, 32, 36, 60].

There are two major strategies for treating hip fractures, prosthesis or osteosynthesis. A prosthesis involves removing the fracture-site, and replacing the femoral head with a Hemi-Arthroplasty or a Total Hip Arthroplasty, the latter also including an acetabular cup. An osteosynthesis involves reducing bone fragments to an acceptable position and retaining them until healing – usually with parallel implants, sliding hip screw or intramedullary nail (Fig. 6.4).

Prostheses are inserted with the patient supine or lateral depending on the surgical approach, while osteosynthesis is always performed through one or more lateral approaches, with the patient supine on a traction table and the use of a radiographic image-intensifier. There are pros and cons for all implants, but all are dependent on proper use, which is why well-defined implant position measurements are needed for optimal evaluation of one implant against another.

Parallel implants are inserted with limited operative bleeding and soft tissue damage through a few lateral stab-incisions or a single <5 cm incision. In spite of many clinical and cadaver studies, choice (screws/hookpins) and number (2/3/4) of implants lacks consensus [49]. Parallel implants permit fracture compression and they should be inserted as vertically as possible and in different head-quadrants. Furthermore, the posterior implant should have posterior cortex contact and the inferior implant calcar contact to achieve three-point fixation that best supports weight transfer from (1) the subchondral bone to (2) a calcar seat and (3) a lateral femoral cortex counterpoint [59]. The main reasons for failure are non-union, with or without mechanical collapse, due to insufficient fixation and/or avascular necrosis. Salvage normally necessitates a hip-prosthesis or, depending on patient demand, a simple removal of the femoral head. A new fall can result in fractures around the parallel implants, which should be reoperated with a sliding hip screw or an intramedullary nail.

Sliding hip screws have been the Gold Standard for treating trochanteric fractures for several decades – but have recently also gained ground for femoral neck fractures [49]. After reduction, the femoral head fragment is held by a large diameter screw, which can slide inside an approximately 135° angle plate attached laterally to the femoral shaft. The implant is inserted under the lateral vastus muscle through a single lateral approach, around 10 cm long depending on chosen plate-length.

To reduce the risk of cut-out of the screw into the hip joint, it should be positioned centrally or central-inferiorly in the femoral neck with the tip attached subchondrally in the femoral head, providing a short so-called tip-apex distance [4]. Beyond cut-out, the common reasons for failure are mechanical collapse, with or without non-union and a distal peri-implant fracture. Depending on femoral head bone status, salvage can be an intramedullary nail or a distally seated hip-prosthesis.

Intramedullary Nails have, during the last decade, outnumbered sliding hip screws as treatment for trochanteric fractures [55]. After reduction, the femoral head fragment is held by a large diameter screw, which can slide at an angle of approximately 130° through an intramedullary nail with 1–2 distal locking screws. The nail is inserted at the greater trochanter tip, through a 5 cm lateral incision, with the sliding and locking screw(s) inserted by use of a guide through stab incisions in the lateral vastus muscle. A central-inferior position in the femoral head and a short tip-apex-distance for the threaded types is important, while the new bladed types might need more distance [37, 58].

Some old nails had a reputation for risking a shaft fracture, but newer nails have moved beyond this, although the many new smaller designs, with different screw, blade, sleeve, locking and anti-rotation mechanisms, lack convincing clinical evidence so far [6, 53].

Reasons for failure are the same as for the sliding hip screws, and salvage can be a distally seated hip-prosthesis for bone-collapse. In case of a distal peri-implant fracture, a longer nail or a condylar plate can be used, depending on the nail-length.

Prostheses involve a metal femoral head replacement attached by a stem seated in the shaft cavity. To fit individual patients’ anatomy, implants are modular and assembled during surgery; thus mono-blocks are no longer recommended [56]. Reoperations are primarily caused by repeated dislocations or by a peri-prosthetic fracture (produced during insertion or subsequent to a new fall). For dislocations, closed reduction is the norm, but reposition or modification with a low-range-of-motion constrained liner is necessary in recurrent cases. Peri-prosthetic fractures are treated with circumferential wires and/or a plate, and a loose prosthesis is changed or removed depending on the patient’s demands.

Hemi–arthroplasties (HA) traditionally have reduced dislocation rate, shorter operating time and less blood loss than a total hip arthroplasty. Reports of acetabular chondral erosion, following unipolar HA, have encouraged bipolar heads with an additional ball-joint – their efficiency is however still debated [24, 48, 57].

Total Hip Arthroplasties (THA) also replace the acetabular cartilage, theoretically a source of pain and thus reduced functional ability, and THAs might provide a better result than HAs in active, independent living, and cognitively intact patients [8, 48]. Despite the higher implant price, the total cost of using THA is probably lower when taking complications and function into account, in the healthiest patients [62]. THAs however have an increased dislocation risk [8, 48], which might be reduced by the technically demanding new dual-mobility types [1, 5].

Beyond optimal implant positioning, the dislocation rate following both HA and THA might be reduced to 1–3 % of patients using the antero-lateral approach, compared to 4–14 % by use of the postero-lateral approach, though the latter can probably be improved by an optimal capsular and muscle repair [13, 14, 51]. The only randomized study however found no difference in dislocation rate between the two methods [50] and research is on-going regarding the consequences of the surgical approach for soft-tissue, pain and mobility. It may be that dual-mobility cups can justify the continued use of the postero-lateral approach [1, 5].

Cementation is associated with more dislocations in some studies but less in others. Cementation seems to improve patient mobility, reduce pain and the rate of peri-prosthetic fractures (1–7 % for uncemented prostheses), although only a few studies include the newer hydroxyapatite-coated surfaces. Cementation probably increases blood loss and operation time, but registries have shown that the higher acute mortality appears to equilibrate after a couple of months [2, 18, 23, 48, 57, 63].

Patients should receive their operation as soon as possible, because the negative impact on body functions, while waiting for surgery, appears to be significant. Surgery on the day of, or the day after admission (12–48 h) is recommended, although studies to prove this are difficult, because stratification by comorbidities is challenging [7, 26, 35, 61].

Surgical drains [11], and pre-operative traction are no longer recommended [21]. Conservative treatment should be avoided in modern healthcare systems [20], except in a few terminally ill patients who can be kept pain-free by analgesics in their last few days of life.

Patients sustaining a metastatic fracture should be identified, the cancer investigated and the proximal femur fixed in a way that takes into account the growing cancer, normally by use of a long nail or a distally seated THA.

Prophylactic antibiotic treatment should be given. Deep infection is rare (Table 6.1), but potentially devastating, often with several procedures and implant removal. While treating the infection, an external fixator can be used to keep extra-capsular fractures reduced. Predictors of infections are primarily surgeon experience and operation duration [19, 38].