Fixation of Femoral Neck Fractures With Cannulated Screws

Overview

Intracapsular femoral neck fractures make up more than half of all hip fractures and are associated with a 30-day mortality of up to 10% (Rockwood). In the elderly, 1-year mortality is about 30%, and a third of patients have a permanent increase in care needs (AO).

Because the blood supply of the femoral head in adults comes mainly through retrograde retinacular vessels along the neck (largely from the medial femoral circumflex artery), displaced intracapsular fractures carry a high risk of osteonecrosis and nonunion (AO). In young patients, the best results are associated with early anatomic reduction and stable internal fixation (AO).

Multiple cannulated screw fixation is a closed (percutaneous) method of internal fixation. Screws should only be inserted after a satisfactory reduction; a poor closed reduction should never be accepted (Campbell).

Classification

Indications and Implant Choice

Who Should Have Internal Fixation?

• Nondisplaced (Garden I–II) fractures, at any age: Fixation is the consensus treatment (AO; Rockwood). Nonoperative treatment carries a high risk of displacement and is reserved for selected nonambulatory or late, asymptomatic patients (Rockwood). If these fractures are treated nonoperatively, AO advises close follow-up; secondary displacement, especially with slight retroversion of the head, requires fixation.

• Displaced fractures in young, physiologically fit patients: Reduction and internal fixation remains the standard (Campbell; AO; Rockwood). AO recommends urgent anatomic (often open) reduction and fixation for healthy, mobile patients under 65 with a low ASA score.

• Displaced fractures in the elderly: Arthroplasty is preferred (Campbell). AO cites consensus for arthroplasty in patients over 80, those with ipsilateral arthritis, rheumatoid arthritis or pathologic fracture, and those with severe chronic disease or limited life expectancy. Rockwood: the evidence now strongly supports cemented arthroplasty for most patients with displaced fractures, with primary THA giving better function and lower revision in fit older patients.

Implant Choice for Fixation

• Cannulated screws vs sliding hip screw (SHS): The FAITH trial (1,108 patients) and later meta-analyses found little or no clinically meaningful difference between the two (Campbell; Rockwood). FAITH subgroups suggested a possible advantage of SHS in displaced and basicervical fractures and in smokers, with more osteonecrosis (9% vs 5%) (Campbell).

• Pauwels III fractures in young adults: Some evidence favors fixed-angle devices. In one series, nonunion was 8% with fixed-angle devices vs 19% with sliding devices, but the evidence is weak (Rockwood).

• Medial buttress (antiglide) plate: Placed at the medial apex of the fracture through a Smith-Petersen approach. In 478 patients under 55, failure was 29% with an added medial plate vs 49% with standard implants (Rockwood). Campbell recommends a small-fragment plate placed directly medially if this option is used.

• Femoral Neck System (FNS): Data suggest less osteonecrosis, fewer complications, less shortening and better function than cannulated screws (Campbell).

• Basicervical fractures: These behave like extracapsular fractures and are best treated with an SHS (Rockwood); a derotation screw adds stability (Campbell; AO).

Preoperative Planning and Implants

• Fracture table, with biplanar fluoroscopy.

• Screws: Three partially threaded cannulated screws (6.5, 7.0 or 7.3 mm) in an inverted triangle (Campbell; AO). A fourth screw (diamond) for significant posterior comminution (Campbell).

  • The number of screws and their configuration are debated: there is some evidence that two screws can be effective, and the inverted triangle may be superior, but no specific configuration is clearly supported (Rockwood).

  • AO recommends a thread length of about 16 mm so that no threads cross the fracture.

• Smooth or drill-tipped guidewires, which improve tactile feedback and reduce cortical breach (Campbell).

• Parallel guide and washers. Washers are associated with better results, probably because of better compression (Campbell; Rockwood).

• A fluoroscopic image of the uninjured hip is a useful intraoperative reference (Campbell).

• Timing: Evidence for emergency fixation in the young is limited. The quality of reduction appears more important than the timing of surgery (Rockwood).

Patient Positioning and Reduction

1. Position the patient supine on a fracture table. Scissor the legs (uninjured hip extended relative to the injured side), or use a well-leg holder (Campbell).

2. Avoid forceful reduction. Start with minimal traction and rotation, check on fluoroscopy, then increase traction and internal rotation in small steps until reduction is acceptable. A common error is excessive traction with forceful rotation, which can produce a valgus reduction that is hard to correct by closed means (Rockwood).

3. Leadbetter maneuver (AO): Abduction and external rotation with lateral traction, then gentle return to neutral and internal rotation, then release of traction to allow impaction.

4. Check the reduction in several planes (for example 0°, 30°, 60° and 90°) (AO). Do not make repeated forceful attempts; convert to open reduction instead (AO).

5. Assessing reduction:

   • The concave neck and convex head should form an S or reverse-S curve on all sides, on AP and lateral views (Campbell; Rockwood).

   • Garden alignment index: About 160° on the AP view (medial trabecular stream to medial cortex) and 180° on the lateral view. Good results were reported when both views were within 155°–180° (Rockwood).

   • Valgus is preferred to varus. A varus reduction of 20° is associated with a 55% failure risk. Arnold recommends less than 20° of posterior angulation (Rockwood).

   • In the young, aim for anatomic alignment. In osteoporotic elderly patients, the fracture can be left impacted in slight valgus (AO).

Surgical Technique

1. Localization and approach: Use biplanar fluoroscopy to locate the inferocentral wire. Make a 2–3 cm incision extending proximally (Campbell), or about 5 cm just below the vastus lateralis ridge if done open (Rockwood). The procedure can be done percutaneously.

2. Split the fascia in line with the incision and split the vastus lateralis fibers longitudinally with a Cobb elevator (Campbell).

3. Inferocentral (first) guidewire:

   • Place it ideally on both views. A wire along the anterior neck helps estimate anteversion.

   • The entry point must not be below the lesser trochanter, and the wire should run along the calcar.

   • The screw should end up less than 4 mm from the calcar (Campbell).

4. Remaining guidewires: Using the parallel guide, insert the posterosuperior wire, then the anterosuperior wire (Campbell).

   • On the AP view, the posterosuperior wire should not be above the equator; the anterosuperior wire should be above it.

   • Keep the screws at least 1 cm apart where anatomy allows.

   • Place the screws peripherally in the neck to resist displacement in all directions; the inferior screw should run very close to the calcar (AO).

   • Advance the wires to just short of the articular surface.

5. Screw length: Measure the guidewire and subtract 5 mm (Campbell).

6. Screw insertion: Self-drilling, self-tapping screws are generally used. The lateral cortex may need predrilling in dense bone. Use washers where possible (Campbell).

   • Tighten the screws carefully and repeatedly to compress the fracture. If a fracture table is used, release traction (AO).

   • Confirm in several planes that no screw penetrates the joint (AO).

7. Fourth screw (optional): For significant posterior comminution (diamond configuration). Take extreme care, because a posteriorly placed screw may be extraosseous (Campbell).

Technical Pearls and Pitfalls

• Technical errors predict failure (Collinge et al., 492 patients under 50; Rockwood): Major reconstructive surgery was needed in 20% of technically adequate fixations vs 56% of those with errors, and risk rose with the number of errors. Errors defined for cannulated screws:

  • Inadequate buttress: inferior screw more than 4 mm from the intact inferomedial cortex

  • Inadequate screw length: screws more than 1 cm from the subchondral bone of the head

  • Inadequate screw spread: 10 mm or less between screws

  • Inadequate reduction

• Neck geometry: The neck is an anteriorly leaning ellipse. The posterosuperior screw of the inverted triangle has the highest perforation risk; keeping screws below the piriformis fossa landmark reduces it (Campbell).

• Subtrochanteric fracture risk: Repeated drilling of the lateral cortex, or entry below the lesser trochanter, is associated with subtrochanteric fracture. An apex-distal configuration (inverted triangle) withstood higher loads (Campbell).

• Thread length: Maximize thread length proximal to the fracture without crossing it (Campbell; AO).

• Bone quality is the critical factor in fixation and implant choice (AO).

If Closed Reduction Fails: Open Reduction

• Approaches: Modified Smith-Petersen (anterior) or Watson-Jones (anterolateral) (Campbell; AO). Subcapital and transcervical fractures are easier to see and reduce through the Smith-Petersen approach, which needs a second incision for fixation. If a medial plate is planned, open reduction through an anterior approach is mandatory (Rockwood).

• Rockwood authors' approach: Attempt closed reduction first and assess its quality before choosing the fixation strategy. They do not routinely open the fracture, and use a Smith-Petersen approach if closed reduction is not good enough.

• Modified Smith-Petersen technique (Campbell):

  1. Supine on a flat-top or fracture table (a fracture table makes lateral imaging easier).

  2. About 10 cm longitudinal incision from the ASIS toward the lateral border of the patella.

  3. Develop the TFL–sartorius interval and cauterize ascending branches of the lateral femoral circumflex artery.

  4. Tag the direct head of the rectus femoris and release it from the AIIS if needed; repair it at closure.

  5. Reflect the indirect head (and iliocapsularis, if present) from the capsule.

  6. T, inverted-T, Z or H capsulotomy. Avoid extending the transverse limb posteriorly at the base of the neck, to protect the head's blood supply. AO describes a T-capsulotomy with the transverse limb at the acetabular rim.

  7. A 5.0 mm Schanz pin with T-handle in the proximal femur controls the distal fragment.

  8. Two 2.0 mm threaded K-wires in the head act as joysticks. Two wires are needed, because rotation is hard to control with one (AO). Farabeuf or Jungbluth clamps can compress the fracture.

  9. Fix with cannulated screws or a fixed-angle device, and/or a medial plate (3 or 4 holes, 3.5 mm one-third tubular, directly over the medial apex; Rockwood).

• Open reduction has been associated with a higher reoperation rate, and the approach chosen has not been shown to affect reduction quality (Campbell). Rockwood: if only intraosseous fixation is planned, opening the fracture does not seem to change results as long as reduction is adequate.

Postoperative Care

• Elderly patients: Aim for mobilization on the first postoperative day with full weight bearing, because most cannot manage partial weight bearing; the fixation should allow this (AO). Campbell allows protected weight bearing with a walker if balance and comorbidities allow, and mobilization to a chair for those who cannot walk safely.

• Young, high-energy fractures: Touch-down weight bearing (weight of the leg) for about 10 weeks (Campbell); young patients can manage partial weight bearing (AO).

• Follow mobile patients until union is confirmed (Rockwood).

• All patients with fragility fractures need secondary prevention (AO).

Complications

• Fixation failure and nonunion: Reoperation rates approach 50% in some series of young patients (Rockwood). In the young, consider revision fixation if the head is viable; valgus osteotomy for nonunion or varus. In older patients with poor bone, bipolar or total hip arthroplasty (AO).

• Osteonecrosis of the femoral head: May take 2–3 years to appear radiographically and leads to secondary arthritis (AO). Treatment options include THA or arthrodesis.

• Femoral neck shortening: Common after screw fixation and associated with pain, reduced mobility and gait changes (Campbell).

• Subtrochanteric fracture; screw perforation of the cortex or joint (Campbell).

References

1. Weinlein JC. Fractures and dislocations of the hip. In: Azar FM, Sawyer JR, Throckmorton TW, eds. Campbell's Operative Orthopaedics. 15th ed. Philadelphia: Elsevier; 2026. Chapter 60, Techniques 60.1–60.2.

2. Simmermacher RKJ. Femur, proximal. In: Buckley RE, Moran CG, Apivatthakakul T, eds. AO Principles of Fracture Management. 3rd ed. Stuttgart: Thieme; 2017. Chapter 6.6.1. (Turkish edition: AO Kırık Tedavisinin Prensipleri.)

3. Griffin XL, Lane JCE, Moppett I, Seymour H. Femoral neck fractures. In: Tornetta P III, Ricci WM, Ostrum RF, McKee MD, Ollivere BJ, de Ridder VA, eds. Rockwood and Green's Fractures in Adults. 10th ed. Philadelphia: Wolters Kluwer; 2024. Chapter 53. (Turkish edition: Erişkin Kırıkları.)