Cantilever Failure of Modular Uncemented Femoral Revision Stem in Patients with Poor Proximal Femoral Support; How to avoid it?

Abstract

Objectives: Revision hip arthroplasty is a major surgical challenge and is even more difficult in cases with a deficient proximal femur. Modular uncemented cone body revision femoral stems were introduced as a solution. They have the advantage of optimising joint kinematics by allowing the variable degrees of version, offset and leg length. However, we noticed cantilever failure of such stems, particularly in patients with deficient proximal femoral support. Fatigue fracture of the revision femoral stems should raise questions about its use in patients with insufficient proximal femoral bone support.

Methods: We present a case series of five patients with the cantilever failure of Stryker restoration modular stem conical distal femur prosthesis. These cases were identified during a retrospective review of revision hip surgeries performed at our trust.

Results: The stem failed after an average of 22.6 months post-revision surgery. Primarily, poor proximal femur bone support with a well-fixed distal stem and secondarily high BMI led to this catastrophic failure in the absence of trauma. All five cases were re-revised to Stanmore proximal femoral replacement and achieved good functional outcomes after an average follow-up of seven years.

Conclusion: Proximal femoral bone support should be restored to prevent early cantilever failure of distally fixed proximal modular revision femoral stems. Consider a proximal femoral replacement if we cannot ensure proximal bone support.