Bore Disruption: An Unusual Mechanical Failure of Two Hip Hemiarthroplasties

Abstract

We report a case of two hemiarthroplasties (HAs) that underwent an unexpected mechanical failure. Two patients affected by femoral fractures were treated with an HA. At 5 and 7 years after surgery, they showed a breakage of the HA at the head–stem junction. We analyzed macroscopically and microscopically (by a scanning electron microscopy) the surfaces of the broken prostheses. In both cases, a fracture was detected starting at the joining point between the femoral head and the slot that receives the taper cone of the stem (the so-called bore), with the typical macroscopic and microscopic pattern of a fatigue fracture. The fatigue fracture resulted from repeated cycles of torsional stresses throughout the years. In literature, we did not find any other report of such HA failure.

Keywords

fatigue - fracture - hemiarthroplasty - hip - scanning electron microscopy

• References

• 1 Raaymakers EL. Fractures of the femoral neck: a review and personal statement. Acta Chir Orthop Traumatol Cech 2006; 73 (01) 45-59
• 2 Becker DJ, Kilgore ML, Morrisey MA. The societal burden of osteoporosis. Curr Rheumatol Rep 2010; 12 (03) 186-191
• 3 Giori NJ. Unexpected finding of a fractured metal prosthetic femoral head in a nonmodular implant during revision total hip arthroplasty. J Arthroplasty 2010; 25 (04) 659.e13-659.e15
• 4 Grupp TM, Weik T, Bloemer W, Knaebel HP. Modular titanium alloy neck adapter failures in hip replacement--failure mode analysis and influence of implant material. BMC Musculoskelet Disord 2010; 11: 3 . Doi: 10.1186/1471-2474-11-3