In this study we present our experience with
four generations of uncemented total knee arthroplasty (TKA) from Smith
&
Nephew: Tricon M, Tricon LS, Tricon II and Profix, focusing
on the failure rates correlating with each design change. Beginning
in 1984, 380 Tricon M, 435 Tricon LS, 305 Tricon 2 and 588 Profix
were implanted by the senior author. The rate of revision for loosening
was 1.1% for the Tricon M, 1.1% for the Tricon LS, 0.5% for the
Tricon 2 with a HA coated tibial component, and 1.3% for the Profix
TKA. No loosening of the femoral component was seen with the Tricon
M, Tricon LS or Tricon 2, with no loosening seen of the tibial component
with the Profix TKA. Regarding revision for wear, the incidence
was 13.1% for the Tricon M, 6.6% for the Tricon LS, 2.3% for the
Tricon 2, and 0% for the Profix. These results demonstrate that
improvements in the design of uncemented components, including increased
polyethylene thickness, improved polyethylene quality, and the introduction
of hydroxyapatite coating, has improved the outcomes of uncemented
TKA over time.
Achieving the correct inclination angle for the acetabular component in total hip arthroplasty (THR) can be technically challenging. The aim of this study is to validate the use of a simple, laser-guided system to address the acetabular cup inclination angle intraoperatively and quantify its accuracy and repeatability across users. A simple inclinometer system was manufactured, consisting of a laser that snaps into both the inclinometer and the handle of a standard trial cup impacter. The system functions as follows:
desired inclination angle is set on the inclinometer, inclinometer is positioned on the acetabulum, laser beam is projected onto and marked on a screen outside of the surgical exposure, the impacter is reoriented in the acetabulum until the laser beam aligns with the recorded mark on the screen. A validation study was performed on this system using intact cadavers (N=4). A THR-specific. Trial acetabular components were installed unilaterally in each donor using both the laser inclinometer system with an in-line mounted intraoperative navigation system (NaviVision, Vector Vision Hip 3.1, BrainLab) serving as the measurement standard. Three orthopaedic surgeons participated in the study, two experienced with the device (“experts”) and one “novice”, and each surgeon performed two sequential validation experiments:
10 trials at a set device inclination angle, and 5 trials of matching the trial cup placement to this set angle. Using the laser-guided system, the inclination angle of the trial cup deviated from the desired orientation by 1.1±0.9° (mean st. dev; range: 0–3°) for all specimens across all operators. The corresponding error in anteversion angle was 1.4±1.3° (range: 0–5°). There was no difference in inclination angle between expert and novice surgeons (1.0±0.8° versus 1.1±1.2°, respectively; p>
0.10 for unpaired t-test). To set the desired inclination angle on the trial cup, original and final laser target positions were within 4.1±2.5 cm at 1 m screen placement. Results suggest that the laser-guided system has sufficient accuracy and repeatability for use intra-operatively. Inclination angles differed from prescribed angles by 1° on average, and malalignment in anteversion was subclinical, ≤5° for all cases. Furthermore, the tolerance for laser re-alignment sufficiently large (5–10 cm) to make the device functional intraoperatively. Future work will focus on expanding the sample size and correcting simple design limitations in the device.
