Failed internal fixation due to osteonecrosis following traumatic periprosthetic fracture after hip resurfacing arthroplasty

Abstract

A 55-year-old man had undergone a Birmingham Hip Resurfacing (Cup 56, Head 50; BHR; Smith and Nephew TLC, London, UK) for primary osteoarthritis. The index procedure and postoperative healing were uneventful and radiographs showed well-fixed femoral and acetabular components. 18 weeks after surgery, the patient was involved in a motorcycle accident and fell on the operated hip. An undislocated vertical fracture of the femoral neck was treated surgically to preserve the prosthesis. As the centrally located implant stem might cause difficulty with the placing of typical implants (e.g. screw-plate device or a cephalomedullary nail), 3 parallel cannulated cancellous screws in a triangular configuration (Figure 1A) were used for fixation of the fracture. Care was taken to avoid contact between the implanted stainless steel screws and both the stem and lateral walls of the femoral component. The patient was operated on 14 h after the injury. Figure 1. A. Traumatic periprosthetic femoral neck fracture 18 weeks after the index procedure treated with cannulated cancellous screws. B. Collapse of the femoral neck (short arrow) led to marked dislocation of both the proximal femoral remnant and all 3 screws ... 11 weeks later, the patient presented with hip pain. Radiographs showed 15-mm descent of the femoral component and a dislocation of all 3 screws (Figure 1B). The arthroplasty was converted to a femoral stemmed total hip replacement with extra-large femoral head (cement-free BiCONTACT System, Aesculap AG, Tuttlingen, Germany) (Figure 1C) and retention of the well-fixed acetabular component. Follow-up at 8 months was uneventful. Retrieved femoral remnant tissue with the in situ femoral component and several bone tissue fragments from the neck obtained at revision surgery were immediately fixed in buffered formalin for further analysis. The specimen was cut with the femoral component in situ, by a diamond-coated band saw, into 4 quadrants and analyzed macroscopically and by contact radiography (Faxitron X-Ray LLC, Wheeling, IL). Both the medial and lateral sections of the central slice were completely embedded in plastic after cement dissolution with acetone and removal of the prosthesis. The specimens were processed undecalcified and embedded in methylmethacrylate. From each undecalcified processed plastic block, one 5-μm section was cut with a heavy-duty microtome. The sections were stained by the toluidine blue staining method. Macroscopically (Figure 2A), a well-fixed femoral component with minimal cement mantle and focal superficial cement penetration was found. Contact radiography of the specimen revealed no reaction to the intraosseously located screw (Figure 2B). Figure 2. A. Well-fixed femoral component, narrow superficial zone of cement penetration, and irregular fracture line were apparent macroscopically on the cut plane. B. Absence of vital reaction to the screw was evident by contact radiography several weeks after ... Microscopically, foreign body granulomas and loose fibrosis were apparent at the bone-cement interface (Figure 2C). The remaining bone tissue showed a loss of stainable osteocytes and disorganized intertrabecular bone marrow. More distally, many dead, irregular bone fragments—so-called “bone chips” (Doorn et al. 1996)—without resorptive reaction were found in the vicinity of both the intraosseous screw and the fracture line (Figure 2D). In contrast with the former, multifocal fracture of bone trabeculae associated with the formation of microcallus (Figure 2E) and broad areas of mineralized callus (Figure 2F) were present in the bone fragments removed from the rest of the femoral neck at the revision surgery. We found no fibrocartilaginous tissue, characteristic of pseudoarthrosis.