Background: Severe acetabular bone loss following total hip arthroplasty (THA) presents a complex reconstructive challenge. Traditional classification systems, such as Paprosky, may not fully capture the morphology of defects in the most extreme cases. Additionally, previous revision plans could not safely manage such cases.
Case Presentation: A 71-year-old man presented with pain and instability four years after a primary THA. Imaging revealed a massive acetabular defect with extensive osteolysis and metallosis, including complete loss of the posterior column, medial wall, posterior wall, inferior rim, and ischium, and only the anterior wall and column remained intact. The acetabular cup had also protruded into the pelvic cavity, approaching the bladder, and had migrated centrally. While the defect resembled a Paprosky type IIC pattern, it was markedly more severe and did not fit existing classifications. A complex two-stage reconstructive surgery was performed, involving elevation of the hip center by 2.5 to 3 cm and compensation for limb shortening through femoral stem lengthening using a long-stem prosthesis. After 2-step revision surgery, the patient experienced prosthetic dislocation, necessitating a third surgery. During this procedure, a bipolar cup was manually drilled to allow bone cement to pass through the holes for improved fixation. Additionally, bone cement was applied over the screw heads (positioned superior to the cup) to construct a scaffold that enhanced implant stability and reduced the risk of dislocation.
Discussion: This case may represent a novel subtype of acetabular bone defect not encompassed by current classification systems. Furthermore, the innovative approach of penetrating a bipolar cup and using cement augmentation over a screw framework presents a potential new strategy for achieving stable fixation in cases of severe bone loss.
Conclusion: This case underscores the need for updated classification systems to account for atypical acetabular defect patterns and demonstrates a novel fixation technique that may improve outcomes in revision THA involving extensive bone loss.