Review Question - QID 219837

This patient presents with a fracture of her fully coated porous stem with good distal in-growth and minimal proximal bone, which can lead to cantilever bending and eventual failure (Answer 1).

Fracture of a fully coated revision stem is a rarely seen complication but has been reported in multiple case series, each with different implants. The implant achieves sufficient distal fixation but is unsupported proximally leading to levering and fracture, especially in stems with smaller diameters. Other risk factors include a history of an extended trochanteric osteotomy (ETO), heavy body weight, and younger age or increased activity level. In the event of fracture, revision surgery is required, and extraction of the distal, fractured stem often requires using trephine reamers and/or creating a distal cortical window.

Landa et al. present a case series of three fractured uncemented, fully porous Echelon femoral stems. Fortunately, an uncommon complication, fracture occurs secondary to cantilever bending after distal bony ingrowth. The authors report increased risk among patients with increased body weight, excessive activity, an undersized stem, varus alignment, inadequate proximal femoral bone stock, and metallurgic defects.

Lu et al. present their series of 40 patients treated with VerSys fully bead-coated femoral stems. The authors report four cases of femoral stem fracture ranging from 23-86 months after surgery. Each patient with component failure had proximal bone deficiency secondary to nonunion. Additionally, this cohort had small stem diameters (<12 mm) and were relatively young with higher activity levels.

Figure A demonstrates a complete fracture of the porous coated stem. The cables indicate a history of prior ETO.

Incorrect Answers:
Answer 2: Stem fracture is the result of sufficient distal fixation with inadequate proximal support
Answer 3: Femoral anteversion plays an important role in stability and preventing dislocation, however, it is not implicated in component fracture.
Answer 4: The stem bypasses the most distal cable by a significant margin (greater than two cortical widths) and achieves good fixation. ETO is a risk factor for stem fracture but this is secondary to insufficient proximal bone stock, not distal fixation.
Answer 5: Thinner femoral stems are at risk for failure.