Periprosthetic Proximal Femur Fractures

Etiology

Periprosthetic fractures have an increased prevalence in:

• Female sex (hormonal imbalance) 
• Osteoporosis and osteopenia
• Neuromuscular disease (e.g., Parkinson, epilepsy, ataxia)
• Cognitive disorder (e.g. dementia)
• Medication-related (chronic steroid use)
• Inflammatory arthritides (e.g., rheumatoid arthritis, osteoarthritis, etc.)
• Infection
• Primary total hip arthroplasty (e.g., aggressive broaching, stress shielding)
• Implant specific (level of constraint, polyethylene wear)[2][5]

Epidemiology

The overall incidence of periprosthetic proximal femur fractures ranges from 0.1 to 18%. Revision arthroplasty, surgical technique, and implant type each can increase the incidence of fracture. Canton et al. found that revision total hip arthroplasty often requires extensive soft tissue and bony dissection and raises the incidence of periprosthetic fracture to 4 to 11%.[6] Kurtz et al. found that inadequate bone stock, overzealous femoral bone preparation, and mismatch between component and patients anatomy accounts for an intraoperative fracture risk of 1.7% for primary total hip arthroplasty (THA). Osteolysis, continuous bone loss, and stress shielding at the proximal femur raises the incidence of periprosthetic proximal femur fracture after primary THA at 20 years to 3.5%.[2]

Pathophysiology

Capone et al. found that intraoperative periprosthetic femur fractures account for 1.7% of primary and 12% of revision total hip arthroplasties.[7] Operative technique and surgical experience have a significant effect on the risk of intraoperative fracture. Abdel et al. found fourteen times increased rate of intraoperative fracture when a cementless femoral stem is used for primary THA.[8] They also found the risk of periprosthetic proximal femur fracture is associated with specific implant designs. A monoblock cup, elliptical cup, and metaphyseal fit femoral stem with extreme taper angles increase the risk of fracture.[8] 

In the postoperative setting, minor trauma accounts for the majority of presentations of periprosthetic fractures. At-risk patients include those with osteoporosis, metabolic disease, medication-related bone loss, and substance abuse. Stress shielding of the proximal femur weakens the bone adjacent to an implant and creates a stress rise susceptible to fracture. The majority of total hip implants are a combination of a few metals, such as cobalt and chromium. Cuppone et al. evaluated the elastic modulus of cortical bone and that of a mixed metal arthroplasty component. Their study found the difference in elastic modulus from the surrounding cortical bone to be 7.7% that of the femoral component.[9] 

History and Physical

A significant number of patients who present with periprosthetic fractures will sustain their injury performing activities of daily living and rarely report considerable trauma associated with their presentation. A thorough history of recent injuries often reveals a history of fragility fractures. Patient presentation is highly variable. Many patients present with intractable thigh or leg pain and an inability to ambulate, while some present to the office with vague thigh pain but still able to ambulate. The physical exam varies between patients, but visible deformity is not easily recognizable secondary to the significant soft tissue surrounding the femur. Neurovascular injury is uncommon in these fractures but is evaluated and documented in every orthopedic patient.

Evaluation

The appropriate evaluation of a periprosthetic proximal femur fracture includes an x-ray assessment of the extremity from hip to ankle. Adequate visualization of the ipsilateral hip and knee is critical for determining what implants would be available to the performing surgeon. Thompson et al. stressed the importance of determining whether the implant has subsided from its position on primary arthroplasty.[10] Orthogonal imaging of the hip may not always provide adequate imaging for preoperative planning. If warranted, a computed tomography (CT) scan may be ordered and has the benefit of fine detail with three-dimension reconstitution possible. Previous operative reports or familiarity with the radiographic appearance of standard arthroplasty implants dramatically increases the ability to preoperative plan. The performing surgeon should be comfortable with a variety of surgical options ranging from in-situ fixation, revision femoral arthroplasty, proximal femoral replacement, and in rare situations, Girdlestone resection arthroplasty.

Classification systems play a significant role in orthopedics, and most fractures in the body have a classification system designed to dictate treatment.[11] The Vancouver classification is a reliable and accurate tool that guides therapeutic plans. Naqvi et al. reviewed forty-five radiographs of patients with postoperative periprosthetic femur fractures and found an 81% interobserver agreement when classifying B1, B2, and B3 fractures.[12] The Vancouver classification was initially divided into intraoperative and postoperative systems. The intraoperative classification system considers its location, pattern, and stability of the fracture. The locations are divided into A, B, and C and correspond to the proximal metaphysis, diaphysis, and distal to stem, respectively. These fractures are further subdivided into fracture morphology and include cortical perforation, nondisplaced fracture, and displaced/unstable fracture. Duncan et al. postoperative Vancouver classification focus on the stability of the prosthesis and quality of the surrounding bone.[11]

Intraoperative Vancouver Classification

• A = Proximal

• A1 = Proximal metaphysis, cortical perforation
• A2 = Proximal metaphysis, nondisplaced fracture
• A3 = Proximal metaphysis, displaced, unstable fracture
• B = Diaphyseal
• B1 = Diaphyseal, cortical perforation
• B2= Diaphyseal, nondisplaced fracture
• B3 = Diaphyseal, displaced unstable fracture
• C = Distal to stem
• C1 = Distal to stem tip, cortical perforation
• C2 = Distal to stem tip, nondisplaced fracture
• C3 = Distal to stem tip, displaced unstable fracture

Postoperative Vancouver Classification

• A = Fracture in the trochanteric region

• AG = Fracture of the greater trochanter
• AL = Fracture of the lesser trochanter
• B = Fracture around the stem
• B1 = Fracture around the stem or just below, well-fixed stem
• B2 = Fracture around the stem or just below, a loose stem, with good proximal bone stock
• B3 = Fracture around the stem or just below it with poor proximal bone stock
• C = Fracture well distal to the tip of the prosthesis

Treatment / Management

Immediate Treatment Options

• Risk of soft tissue compromise or neurovascular injury: emergent skeletal stabilization
  • Options: traction via placement of a traction pin or application of external fixator
• Stable fracture with no soft tissue or neurovascular concern:
  • Immobilization, weight-bearing restrictions, skeletal immobilization (splint application, knee immobilizer).

Postoperative Periprosthetic Fractures

1. Nonoperative management
   • Indications: rare (medically unfit surgical candidates).
   • Restriction: non-weight bearing to involved extremity until callus present
   • Pearls: increase soft tissue surveillance in bed-bound patients (increase turns in bed, offload fracture with additional padding).
   • Education: crucial to educate patient and patient's family risk of complications (nonunion, malunion, skin compromise)
2. Vancouver A fractures (operative fixation):
   • Indications: Marsland et al. argue that displacement of the greater trochanter more than 2 cm significantly compromised the abductor complex and should be an indication for operative fixation.[13] 
   • Fixation options: Ricci et al. described the use of trochanteric claw plates for additional fixation for displaced greater trochanter fractures.[14]
   • Pearls: a unique subset of fractures with a lack in the literature regarding the treatment of isolated Vancouver Ag fractures exist.
   • Postoperative weight-bearing: Ricci et al. recommend partial weight-bearing with or without abduction brace for up to 3 months or until fracture callus is present.[13]
   • Other: If the greater trochanter is significantly stress shielded or damaged secondary to osteolysis, the fragment may not be amenable to stabilization with a plate and screw construct.
3. Vancouver B fractures (operative fixations):
   • Location: occur at or just distal to the tip of the femoral stem.
     • Vancouver B1 fractures
       • Stability: occur around a well-fixed prosthesis.
       • Bone stock: adequate bone stock surrounding the femoral implant.
       • Treatment:
         • Open reduction and internal fixation with a plate construct is the standard method of fixation.
         • Ricci et al. described the number of screws used in a locking plate proximal and distal depend on the location of the fracture. In general, four cortices proximal and eight cortices distal provide sufficient fixation.
         • Augmentation with cerclage wiring and allograft or autograft struts may be indicated in a very proximal or distal location, existing intramedullary hardware, or adequate bone stock.[15] 
         • If a stemmed total knee component is close to the proximal femoral component, overlapping the plate over the femoral prosthesis lessens the stress riser between the components.[14]
       • Postoperative care: non-weight bearing on operative extremity until fracture callus is present
       • Complications:
         • Fredin et al. found that immobilization and weight-bearing restrictions pose a significant medical concern for this patient population increased the length of hospital stay an average of 91 days.[16] 
         • Lindahl et al. found a high rate of failure when open reduction with internal fixation was performed alone, citing a 34% failure rate attributed to a misdiagnosed loose femoral component (missed Vancouver B2 type fracture).[17]
         • Must compare the immediate postoperative image of primary THA with preoperative X-rays taken in the emergency room prior to fixation.
     • Vancouver B2 fractures
       • Stability: unstable femoral component.
       • Bone stock: adequate proximal bone stock
       • Treatment:
         • Revision THA with a fracture bypassing diaphyseal fit stem and open reduction with internal fixation of the fracture is the recommended treatment for Vancouver B2 fractures.
         • Lewallen et al. describe the use of cerclage wire fixation distal to the fracture to prevent the propagation of the fracture when reaming or broaching for the revision stem. Additional fixation is utilized proximal and distal to the fracture site to maintain fracture reduction.[18] The length of the stem should bypass the fracture by 2 to 3 cortical diameters to achieve sufficient distal fixation.[18] 
       • Postoperative care:
         • Mulay et al. recommend the patients to be restricted to toe-touch weight-bearing for six weeks on the postoperative extremity with progression to full weight-bearing by three months.[19] 
     • Vancouver B3 fractures
       • Stability: Unstable femoral component.
       • Bone stock: Adequate proximal bone stock
       • Treatment:
         • Options: revision THA with a diaphyseal fit prosthesis, tumor (mega) prostheses, and allograft prosthesis
         • Proximal fixation of the fracture with plate fixation with or without cerclage wire construct.[13]
         • Rayan et al. found that fully coated uncemented femoral stems have an excellent clinical outcome with a union rate of 86 to 100%.[20] 
4. Vancouver C fractures
   • Location: occur distal to the femoral prosthesis.
   • Stability: stable femoral component.
   • Bone stock: adequate proximal bone stock
   • Treatment:
     • Open reduction with internal fixation using locked, nonlocked, or compression plate technology with or without cerclage wire fixation.
     • O'Toole et al. highlighted the importance of plate length. They recommended the plate length should be long enough to overlap the distal aspect of the femoral prosthesis and amenable to four to six cortices distal. Unicortical screws at the level of the femoral stem offer additional support and can be combined with cerclage wire fixation if needed.[21]
(B2)

Intraoperative Periprosthetic Femur Fractures

Vancouver A1 and A2 fractures involve a cortical perforation and nondisplaced fracture of the proximal metaphysis, respectively. Vancouver A1 fractures are amenable to autograft bone graft from the acetabulum or femoral head and continuation of hip arthroplasty. Vancouver A2 fractures are fixed with a cerclage wire construct to prevent the fracture propagation and then insertion of the femoral component in a standard fashion. Displaced A3 fractures may require provisional fixation with a plate or cerclage wire prior to placing a fully porous-coated stem. Vancouver B1 to B3 fractures involve diaphysis. Lewallen et al. found that provisional fixation with cerclage wire is sufficient to stabilize the fracture and allow a fully porous-coated stem to be inserted distal to the fracture by a minimum of 2 to 3 cortices.[18] Strut allografts may be necessary for B3 fractures. Vancouver C fractures are all distal to the femoral component. These fractures are similar to Vancouver B fractures and benefit from open reduction with internal fixation using a combination of plate and cerclage wiring and insertion of a long porous-coated femoral stem.

Differential Diagnosis

Before the radiographic evaluation, the differential diagnosis should include:

• Periprosthetic fracture
• Aseptic loosening
• Prosthetic joint infection
• Ligamentous injury
• Fracture of the metal or polyethylene implant
• Contusion
• Hip dislocation
• Venous thromboembolism
• Occult fracture
• Metallosis

Prognosis

Drew et al. compared the mortality rate of periprosthetic proximal femur fractures and hip fractures. They reviewed 291 patients and found a one-year mortality rate of 24%, which is similar to the 30% cited for hip fractures.[22] Zheng et al. highlighted the complexity of the surgery and its effect on morbidity and mortality; despite proper surgical treatment, patients struggle to recover entirely and often have unfavorable outcomes.[23]

Complications

A periprosthetic proximal femur fracture is a challenging situation, and reports of complications are high. Lindahl et al. reported an 18% overall complication rate, with 23% of patients requiring reoperation. They found that 24% of patients resulted in a nonunion, and 24% suffered a refracture.[17] In addition, they found that delayed union, failure of hardware, hip dislocation, neurovascular injury, wound complications, and infection also affects this patient population.[17] Henderson et al. quoted the rate of infection for in-situ fixation with plating up to 9%.[24] In-situ fixation with plate technology involves a more substantial operative dissection and trauma to the bone and soft tissue. Klein et al. reported a 21% rate of dislocation after revision THA due to the compromised abductor complex.[25]