Purpose or Learning Objective: (1) To highlight the possible complication of peg fracture observed a decade after
technically successful uncomplicated total knee replacement (TKR). (2) To evaluate
imaging modalities and optimum magnetic resonance imaging (MRI) sequences to aid the
diagnostic pathway.
Methods or Background: Knee surgeons have observed patients presenting with unexpected polyethylene peg
fractures a decade after technically successful uncomplicated knee arthroplasty with
the Journey 1 bicruciate substituting (BCS) prosthesis. In 2005, the Journey 1 BCS
(Smith & Nephew, UK) was introduced to produce better flexion and improved function
with the “guided motion mechanism” based on a more natural anatomical design. At 10
later, we have become aware of patients presenting with sudden nontraumatic knee instability
due to peg fractures proven on arthroscopy. The peg fractures may be missed on initial
imaging with nonoptimized MRI sequences. MRI sequences were evaluated for detecting
complications with various techniques and slice thicknesses.
Results or Findings: A total of 272 Journey 1 TKRs were inserted from June 2010 to June 2013. Early complications
included anterolateral pain from iliotibial band irritation, possibly due to excessive
femoral rollback and femorotibial dislocations. However, other than the small number
of patients with these early complications, the rest achieved excellent outcome parameters
regarding both range of movement and outcome scores.
Four patients have since been found to have peg fractures a decade after an uncomplicated
TKR. Three of them have undergone revision surgery; a fourth is awaiting surgery.
The observed imaging findings include a joint effusion, with truncation or discrete
fracture of the peg of the polyethylene liner of the tibial component or an intra-articular
loose fragment. On radiographs, there is anterior tibial translation in flexion that
would need to be specifically requested because knee radiographs are usually done
in extension. MRI sequences included axial, coronal, and sagittal short tau inversion
recovery, and sagittal proton density or T1. Our unit included slice encoding for
metal artifact correction (SEMAC) metal reduction sequences with 4- to 9-mm slices.
Conclusion: It would be beneficial for radiologists to be aware of potential polyethylene peg
fractures in patients with Journey 1 TKR prostheses, using imaging findings and optimized
MRI sequences as described here.
