Fracture of the femoral adapter bolt and taper adapter in a modern rotating platform knee arthroplasty

A 58-year-old woman presented with onset of pain associated with a popping sound after a twisting motion 4 years after left total knee revision arthroplasty. She had a complex medical history, including a reported bone cement allergy, and presented to the hospital unable to bear weight. Plain radiographs revealed a broken femoral component, with the femoral metaphyseal sleeve separated from the distal articular component. During surgery, it was observed that the femoral adapter bolt and taper adapter had both fractured. Scanning electron microscopy of the fracture surfaces of the components confirmed that the implant had failed in fatigue, presumably due to high cyclic loads. Failure at this junction has not been described previously. In this type of knee design, we recommend supporting the distal articular component either with bone, augmentation, and/or bone cement to reduce the risk for this mode of failure. Keywords: Total knee arthroplasty, Revision, Implant failure, Modula

Modular junction fractures in a modern rotating-platform knee arthroplasty system

In this series, we report the findings from four patients who presented with pain and mechanical symptoms after revision total knee arthroplasty with the DePuy Sigma TC3 RP prosthesis. Plain radiographs for each patient demonstrated failure of the femoral component at the modular junction of the femoral prosthesis. Retrieved implants at the time of surgery revealed fractures occurring exclusively at the femoral adapter bolt and the corresponding adapter. Retrieval analysis was performed on two of the four cases by visual light microscopy. Our findings suggest that the implants had suffered from fatigue fractures likely due to cyclic loading. This is the first case series to describe the failure mechanism and clinical scenarios contributing to failure of the femoral locking bolt and adapter sleeve in this prosthesis. Keywords: Total knee arthroplasty, Implant failure revision, Modula

Fracture of an S-ROM stem at the sleeve-stem junction

Fracture of a well-ingrown femoral component is a rare and often challenging complication. Modular junctions and sleeve interfaces have been identified as one potential point of weakness with corrosion and fretting being contributing factors to ultimate femoral component fracture. Stem fractures at the sleeve interface were reported occasionally for the proximal ingrowth modular Emperion System (Smith and Nephew, Memphis, TN). However, this failure mechanism has been reported infrequently, often associated with corrosion at the modular junction, for the similarly designed S-ROM system (DePuy Orthopedics Inc., Warsaw, IN). We present the case of a 52-year-old patient, with a body weight of 84 kg (185 lbs) and a body mass index of 30.6 kg/m2, who suffered a fatigue fracture of a 14 × 09 × 130 mm S-ROM stem 42 months after implantation. The present study presents the results of the surface analysis, discusses possible failure mechanisms, provides treatment guidelines, and a review of the literature revealing 15 cases of failure at the level of the stem-sleeve junction. In particular, modifiable risk factors for potential stem failure, including stem diameter, stem offset, and the resulting cantilever bending forces on the proximal sleeve-stem junction, are discussed in detail. Keywords: Stem fracture, Removal technique, Breakage, Failure, Corrosio

Catastrophic failure of tripolar constrained liners due to backside wear: a novel failure mode

Constrained acetabular liners have been developed for patients who are at high risk for dislocation or who are undergoing revision surgery for recurrent dislocations. We report on 2 cases of failure of tripolar constrained liners due to severe backside polyethylene wear after dissociation of the outer polyethylene liner without dislocation, a mode of failure not previously reported. The backside of the inserts suffered severe polyethylene deformation, wear, and scratching due to dissociation from the locking mechanism. In patients with tripolar constrained liners, radiographic evidence of eccentric wear should be considered as possible occult dissociation of the polyethylene liner within the shell. Conversion to a modular dual mobility liner appears to be a viable solution in this setting. Keywords: Revision total hip arthroplasty, Dislocation, Tripolar constrained liner, Modular dual mobilit