Basicervical Fractures

A basicervical fracture runs across the base of the femoral neck, at its junction with the trochanteric region; the current AO/OTA code is 31-B3. Published series have not used a uniform defining line or permitted trochanteric extension. That changes which injuries enter each cohort, and it is a major reason reported mechanical-failure rates vary.

The useful clinical task is therefore morphological. Trace the fracture on AP and lateral views, identify its verticality, displacement, comminution and any greater- or lesser-trochanter extension, and decide whether stable cortical contact can be restored.

Mechanism. The mechanisms are similar to those of femoral neck fractures:

• Low-energy fall - elderly patients with osteoporosis
• High-energy trauma - young patients (motor vehicle accident, fall from height)
• Torsion - a rotational force
• Direct trauma - less common

Who. The fracture is uncommon: 1.8% of all proximal femoral fractures in pooled review data, and up to about 4% in single-centre series. The older "5-10%" figure is not supported. Most patients are elderly with osteoporotic bone, hence a female predominance, and the injury is usually unilateral.

The high-energy minority. A minority of these fractures follow high-energy trauma in younger patients. In them, consider an ipsilateral femoral shaft fracture; that combination has its own section below.

The region. The basicervical region is the base of the femoral neck, immediately proximal to the intertrochanteric line: distal to the true femoral neck and proximal to the lesser trochanter. It is a transition zone between the femoral neck and the intertrochanteric region.

The capsule. The fracture line lies close to the capsular attachment, and its intracapsular or extracapsular extent varies with fracture morphology. "Extracapsular" is therefore not an absolute radiographic definition of this fracture.

The blood supply. Displacement at the base of the neck can still threaten the retinacular vessels, and published basicervical cohorts do not define vascular risk consistently. Assess displacement, intracapsular extension and viability concerns rather than assuming the femoral head is protected because the line is low.

Why it fails. Verticality, a short proximal segment, comminution and loss of the cortical buttress all influence shear and rotational stability, and shear, rotation and loss of cortical support may all contribute to failure. Because the line sits at the base of the neck, the head-neck fragment is short and its rotational lever arm small, which is why a single lag screw or blade is prone to allowing rotation and collapse. Fixation fails by:

• Rotational instability - the short head-neck fragment can spin around a single lag screw or blade
• Collapse and shortening - axial and varus collapse at the fracture line
• Cut-out - lag-screw migration through the head, worsened by a high tip-apex distance

AO/OTA. In the current AO/OTA proximal-femur classification a basicervical femoral-neck fracture is 31-B3, but older studies may place similar patterns in 31-A1.2 or use local definitions. Record which classification edition and radiographic criteria are being applied. The code identifies location; it does not by itself establish capsular extent, vascular risk or the optimal implant.

The definition problem. There is no consensus radiographic definition of a basicervical fracture. Some authors define it by the relation of the fracture line to the intertrochanteric crest, others by the capsular reflection, and studies also differ in their implants and failure endpoints. This heterogeneity is a major reason reported failure rates range from 0% to over 50% across series, and why pooled estimates must be read with caution.

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For the exam, state that the lack of a uniform definition limits the evidence base, and that you would treat the pattern as an intertrochanteric-type injury.

Stability and comminution. For treatment the fractures fall into two groups. Comminution and bone quality, not patient age alone, drive implant selection.

History. The mechanisms are set out above. The patient has immediate pain in the hip or groin, pain with movement and an inability to bear weight, and a shortened, externally rotated leg if the fracture is displaced.

Examination. Basicervical fractures may present like femoral neck or intertrochanteric fractures, so imaging is essential for diagnosis and classification. Leg shortening and external rotation suggest displacement. Swelling is minimal because the fracture lies deep.

• Palpation - tenderness over the hip, groin and greater trochanter; crepitus is rare
• Movement - hip range of motion limited by pain, pain with passive motion, and inability to perform a straight leg raise if displaced
• Neurovascular status - usually intact; assess distal pulses and sensation

Associated injuries. Other injuries may accompany the fracture:

• Other fractures (wrist, spine, other hip) - 10-15%
• Head injury - 5-10% (high-energy trauma)
• Soft-tissue injuries - less common

These associated-injury percentages are conventional teaching estimates for high-energy hip trauma, not measured rates from a basicervical-specific cohort.

Radiographs. An AP pelvis and a lateral hip are essential; together they show the fracture's location and displacement. Read them for:

• Location - the base of the femoral neck, at the junction with the intertrochanteric region
• Displacement - under or over 2mm
• Comminution
• Bone quality - osteoporosis

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CT is not routine, but it helps in complex cases and for surgical planning. It assesses the fracture pattern, comminution and displacement, plans the fixation strategy and looks for associated fractures.

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Three-dimensional reconstruction is helpful for complex patterns, for judging comminution and for preoperative planning.

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MRI is rarely needed and is not routine. It is indicated only for a specific concern: an occult fracture when the radiographs are negative, pre-existing AVN, or associated injuries.

Where is the fracture line? The whole management decision turns on distinguishing a basicervical fracture from its neighbours on the AP and lateral films.

The decision. Fixed-angle fixation is usual, but comparative evidence does not mandate one device for every pattern. Select a sliding hip screw, cephalomedullary nail or other construct after assessing fracture orientation, trochanteric extension, comminution, reduction and bone quality, and address any missing cortical support. Do not reduce the decision to an implant label.

Non-operative treatment is rarely indicated: a non-displaced, stable fracture in a low-demand patient, medical contraindications to surgery, or patient refusal. Outcomes are poor compared with surgical treatment, with a high risk of displacement and nonunion. The protocol:

• Bed rest initially
• Progressive mobilisation
• Non-weight bearing for 6-8 weeks
• Follow-up radiographs

Surgical indications. Operate within 24-48 hours, as for femoral neck fractures.

• Absolute - a displaced fracture, an unstable pattern, or a symptomatic non-displaced fracture
• Relative - a non-displaced fracture in an active patient, or failed non-operative treatment

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Principles for every construct. Obtain cortical apposition, restoring medial and anterior cortical support when possible, and avoid varus and malrotation. Place the head element safely, and confirm on both views that the chosen construct controls the instability you observed.

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Every construct in this topic is judged against one number, the tip-apex distance (TAD). A low TAD is the single most reproducible way to reduce lag-screw cut-out in a rotationally unstable base-of-neck fracture, so the metric deserves defining in its own right.

Definition (Baumgaertner). TAD is the sum of two distances: from the tip of the lag screw to the apex (subchondral surface) of the femoral head on the AP radiograph, plus the same distance on the lateral radiograph. Each is corrected for radiographic magnification, using the known diameter of the lag screw as the on-screen scale.

Why 25 mm. In the original 198-fracture series, none of the 120 screws with a TAD of 25 mm or less cut out. Mean TAD was 24 mm in fractures that healed and 38 mm in those that failed, with a strong dose-response: every additional millimetre raised the cut-out risk regardless of fracture pattern, reduction or implant.

How to hit it. Aim the guide wire centre-centre or slightly inferior-central, deep to within 5-10 mm of subchondral bone, on both views before reaming. A calcar-referenced TAD (CalTAD), which measures the AP component from an inferiorly placed screw to the calcar rather than to the centre, has been proposed as a refinement; it reflects evidence that an inferior rather than superior AP screw position resists cut-out. The practical message is the same: deep, central-to-inferior, and never superior or short.

Collapse and fixation failure. The collapse and conversion figures come from a cohort of fixed fractures (Lee 2018). Rotational instability and comminution of the short proximal fragment cause the collapse, and its sequelae are neck shortening and varus malunion. Prevention is rotational control (a derotation screw or helical blade), a central lag screw and a low TAD; established failure is managed by revision fixation or conversion to arthroplasty.

AVN and nonunion. Both are uncommon. The fracture is largely extracapsular and distal to the main retinacular entry, so the head usually keeps its blood supply and AVN is far less common than after a displaced intracapsular neck fracture; nonunion, too, is less common than after intracapsular neck fractures. Capsular extent still varies with morphology, and displacement can still threaten the retinacular vessels, so vascular risk is assessed in each fracture rather than assumed from the label. Nonunion is managed by revision fixation or conversion to arthroplasty.

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Weight bearing. Early mobilisation is the goal in this elderly population: prolonged restricted weight bearing is poorly tolerated and increases medical complications. With a stable cephalomedullary nail or sliding hip screw the patient weight bears as tolerated under physiotherapy supervision, and protected weight bearing is reserved for very comminuted or tenuous constructs. After arthroplasty the patient also weight bears as tolerated. Hip and knee range of motion and quadriceps work begin from day one.

The endpoint. Functional recovery to pre-injury mobility is the realistic endpoint. The priority is preventing collapse and a second fall; return to sport is not the aim.

Revision by implant. Pooled systematic-review data (Dekhne 2021; Yoon 2022) give approximate revision rates; the cannulated-screw figure sits with the argument against them under Surgical Technique.

• Sliding hip screw - ~7%
• Cephalomedullary nail - ~8%
• Hemiarthroplasty - ~8%
• Total hip arthroplasty - ~0% (very small numbers)

Prognostic factors. The dominant late problem is mechanical collapse rather than vascular failure.

This is predominantly a fragility fracture, so management does not end with the operation.

• Treat the osteoporosis - assess fracture risk and start bone-protective therapy (for example a bisphosphonate or denosumab) with calcium and vitamin D as indicated
• Prevent falls - multifactorial assessment, gait and balance training, medication review, home-hazard modification
• Orthogeriatric co-management and early mobilisation reduce medical complications and mortality after hip fracture

Recognise it. Ipsilateral neck-and-shaft fractures are a recognised association of high-energy femoral shaft fractures in younger patients. The neck component is notoriously easy to miss: it is often minimally displaced, vertical or basicervical, and overshadowed by the dramatic shaft injury. In a review of 722 cases basicervical was the commonest hip-fracture subtype (39%), and diagnosis was delayed in 30% (Alho 1997).

Image the neck. Every high-energy femoral shaft fracture therefore warrants dedicated hip imaging: a true AP internal-rotation hip view, fine-cut CT of the femoral neck, and a deliberate fluoroscopic check of the neck before, during and after shaft fixation.

The neck fracture takes priority. Its risk of avascular necrosis and nonunion dominates the long-term prognosis, so it must be anatomically reduced and stabilised; do not let neck reduction be lost while passing an antegrade nail. There are two construct strategies:

• Single-implant reconstruction (cephalomedullary) nail - one device spans both fractures, but neck reduction and proximal-screw placement are constrained by the nail, and the neck can be left under-reduced
• Dual-implant "separate" fixation - the neck is fixed independently (cannulated screws or a sliding hip screw) and the shaft with a retrograde nail or plate; increasingly favoured because the higher-stakes neck fracture can be reduced and fixed anatomically and independently of the shaft implant

Whichever is chosen, treat the neck fracture as the priority injury and confirm that its reduction is maintained after the shaft is stabilised.

Global Epidemiology

• Basicervical fractures are uncommon: ~1.8% of all proximal femoral fractures in pooled review data, up to ~4% in single-centre series
• Predominantly a fragility fracture of older adults with osteoporotic bone; female predominance
• In high-energy young patients, basicervical was the commonest hip-fracture subtype (39%) in concurrent ipsilateral hip-and-shaft injuries (Alho 1997, 722 cases)

Guidelines Side by Side

Registry and Practice Variation

• Registries generally pool basicervical injuries with broader neck or trochanteric categories, limiting fracture-specific outcome estimates
• Resource setting affects implant availability, imaging and rehabilitation, but the same principles apply: define morphology, obtain stable reduction, place the implant safely and mobilise according to construct and patient

No agreed definition. The definition problem set out under Classification is the first uncertainty (Yoo 2020; Dekhne 2021). Until series agree on the boundary, every pooled estimate on this page must be read cautiously.

Nail or plate. A meta-analysis found no significant difference in cut-out or reoperation between the cephalomedullary nail and the sliding hip screw, with slightly faster union for the nail (Yoon 2022). One cohort, however, found substantially higher collapse and failure with a purely extramedullary plate-and-screw construct than with an intramedullary helical-blade construct, and identified the plate as an independent risk factor for failure (Lee 2018). Read that interval before quoting it: OR 12.2, 95% CI 1.08 to 137.7, which barely excludes 1 and spans two orders of magnitude. The pragmatic position is that both work, with an intramedullary helical-blade construct favoured in osteoporotic or comminuted bone.

Cannulated screws. Once considered acceptable, isolated cannulated screws now have clear evidence against them from pooled revision data and biomechanics (Dekhne 2021; Panteli 2015). This is a genuine change in recommended practice.

Primary arthroplasty. Whether primary arthroplasty should be offered to selected frail elderly patients, rather than fixation followed by conversion when it fails, remains unresolved for want of comparative trials.