Simple or comminuted fracture patterns at or around an unstable stem with poor bone stock are classified as type IV.3-B3 fractures by UCPF. The remaining proximal bone cannot support stem revision and fracture repair.
UCPF type IV.3-B3 fractures have extensive considerations outside of the fracture morphology. They involve underlying bony metabolic problems, infectious or underlying mechanical complications of the total hip replacement.
Often low energy injuries
Bony erosion due to infection
Polyethylene wear and associated osteolysis
Pathologic fracture must always be considered.
Deformity of the lower limb
Leg length discrepancy
Preinjury and postinjury pain
Constitutional symptoms, such as: fever, malaise, metallic taste
AP and lateral radiographs usually reveal the complexity of the fracture. When the fracture extends more proximally, a CT scan can be helpful to delineate lines that extend between the trochanters. Most important is a review of any prior radiographs of the hip replacement which can allow for evaluation of stability. If any changes are noted between the prior set of radiographs and the injury films, the stem should be considered unstable and revision is the appropriate treatment. Evaluation of bone stock is necessary to determine appropriate surgical treatment plan.
Features of a IV.3-B3 fracture include thinning of the cortex about the stem, significant osteolysis and osteopenia. Look for asymmetric liner wear and associated osteolysis.
Important consideration should be given to the underlying cause of inadequate bone stock. Preoperative aspiration of the hip joint to evaluate for infectious etiology should be done as it will change surgical approach dramatically.