Abstract
The fate of the patella in two-stage revision total knee arthroplasty (TKA) for periprosthetic
joint infection (PJI) in which the patella is left as a bony shell is poorly described.
The purpose of this case series is to describe a phenomenon we name the Dalí Sign,
which is characterized by elongation and curvature of the patella around the lateral
edge of the femoral component occasionally observed in patients undergoing two-stage
revision without reimplantation of the patellar component. Our institutional surgical
database was queried for patients who were treated with two-stage revision arthroplasty
for PJI by the two senior authors. All available sequential skyline patellar radiographs
were viewed from immediately prior to first-stage explantation to latest image at
final outpatient follow-up at our institution and assessed for the abovementioned
morphological changes. Included patients underwent a two-stage revision surgery for
PJI at our institution, had a patellar component removed during the first stage of
their treatment which included implant explantation and insertion of temporary antibiotic
spacers, did not have the patellar component reimplanted during their second-stage
revision surgery, and demonstrated radiographic patellar morphological changes at
final follow-up. Patients' demographic, surgical, and outcome data were recorded.
Our review identified six patients meeting these criteria. Mean follow-up after second-stage
surgery was 12 months (range 2 to 21 months). At final follow-up, three patients were
walking without pain, one patient was exercising to tolerance, one patient was walking
with pain, and one was using a wheelchair or a walker for mobility. In this case series,
we characterize the Dalí Sign, the elongation and curvature of the patellar bony shell
over the femoral component after two-stage revision for PJI. Further comparative cohort
studies are necessary to identify the incidence and risk factors for the development
of this morphological change and to compare outcomes of patients with and without
the Dalí Sign when left with a bony shell after staged revision TKA.
Keywords
patella resurfacing - total knee arthroplasty - TKA - PJI - periprosthetic joint infection
