Extensor mechanism injury/failure following spacer dislocation in periprosthetic joint infection: a case series in a single reference center.

Antibiotic-loaded spacers are widely used in the two-stage revision protocol for managing periprosthetic joint infections (PJIs) of the knee, offering effective local antibiotic delivery while maintaining joint space and soft tissue tension. However, despite their clinical benefits, complications such as extensor mechanism rupture remain under-recognized and can severely compromise functional outcomes. This retrospective case series presents consecutive patients treated between 2014 and 2022 by a single orthopedic team at our institution. All patients were diagnosed with knee PJI and experienced extensor mechanism rupture following the implantation of either static or dynamic antibiotic-loaded spacers. The analysis highlights the multifactorial etiology of this complication, including factors such as severe bone loss, suboptimal spacer positioning or design, repeated debridements, and individual patient risks such as obesity and previous surgical history. Dynamic spacers, while allowing partial joint mobility, were associated with a higher risk of mechanical overload, whereas static spacers posed risks related to rigidity and stress transmission. Surgical management in all cases involved radical debridement, assessment of bone loss and femoral canal diameter, and careful selection of spacer type. Awareness of the potential for extensor mechanism injury should inform both surgical technique and postoperative care strategies.