Causes / typical injury mechanism: Total hip arthroplasty (THA) periprosthetic fractures are rare, occurring in approximately 0.1%-3% of all cementless THAs. The most common cause of THA periprosthetic fractures is minor trauma (87%), particularly low-energy falls, followed by spontaneous fracture (9%) and major trauma (4%). The large majority of these fractures occur at the femur, but acetabular fractures may also occur.

Classic history and presentation: The condition presents as pain, swelling, or bruising over the hip or thigh, particularly during weight-bearing and hip mobilization. A lower limb length discrepancy may be present, with the affected limb appearing shorter. Patient history includes THA and often involves a recent fall.

Prevalence: The occurrence of postoperative THA periprosthetic fracture has been estimated as up to 3%-4% following a primary hip arthroplasty and up to 12% following a revision hip arthroplasty.

• Age – Postoperative THA periprosthetic fractures most commonly occur in patients of advanced age due to association with other comorbidities, such as osteoporosis, and increased likelihood of falls. However, younger patients with an active lifestyle are also at an increased risk.
• Sex / gender – This condition can occur in either sex but is more common in females due to increased bone degeneration with age.

Risk factors:

• Osteoporosis
• Rheumatoid arthritis
• Advanced age
• Posttraumatic osteoarthritis
• Proximal femoral deformities
• Prior ipsilateral hip surgery
• Trauma
• Osteolysis
• Stem loosening with associated osteolysis
• Revision THAs

Pathophysiology: The condition occurs as a result of a break in the bone surrounding the implant of a THA. In most cases, the integrity of the bone is compromised prior to the fracture due to underlying conditions, such as osteoporosis, in which excessive bone resorption and inadequate bone formation cause skeletal fragility. A low-energy trauma, such as a fall from a sitting or standing height, then compromises the biomechanical integrity of the bone, resulting in a fracture. Although this mechanism is most common, THA periprosthetic fractures can also occur in individuals without pre-existing loss of bone integrity as a result of high-energy trauma to the hip, such as a car accident.

Grade / classification system: The Vancouver classification system is a validated method for guiding treatment of postoperative periprosthetic femoral fractures based on location of the fracture, stability of prosthesis, and surrounding bone quality. Type A fractures involve either the greater (AG) or lesser (AL) trochanter. Type B fractures occur around or just below the stem, and are divided into B1, B2, and B3, depending on surrounding bone quality and implant stability, with B1 having a well-fixed stem, B2 having an unstable stem with good surrounding bone quality, and B3 having an unstable prosthesis and poor proximal bone quality. Type C fractures occur distal to a stable implant and stem.