Abstract
Accurate placement of acetabular components during total hip arthroplasty (THA) is
paramount in ensuring long-term stability. Current methods for monitoring cup position
and leg length intraoperatively are lacking due to susceptibility to inaccuracy or
prohibitive cost. The purpose of this study was to evaluate the ability of an imageless
surgical navigation tool to accurately measure acetabular cup inclination and leg
length differential during THA. The authors retrospectively reviewed the medical records
of patients who underwent primary or revision THA (posterolateral approach) at their
facility with the assistance of computer-assisted navigation between February 2016
and March 2017. Pre- and postoperative radiographs were analyzed for leg length discrepancies
and acetabular cup inclination. Radiographic values were compared with intraoperative
values provided by the surgical navigation tool. The mean difference between inclination
as measured from radiographs (44.4 ± 5.9 degrees) and navigation (43.0 ± 4.4 degrees)
was −1.4 ± 4.6 degrees (mean absolute difference: 3.8 ± 2.8 degrees). Seventy-seven
percent (48/62) of navigation measurements were within 5 degrees of radiographs. The
mean difference between radiographic (7.39 ± 5.67 mm) and navigation (7.44 ± 4.81
mm) measurements of leg length differential was 0.29 ± 4.20 mm (mean absolute difference:
3.20 ± 2.69 mm). Navigation tool measurements were within 5 mm of radiographic values
in 85% (39/46) of cases. At 90 days, idiopathic dislocation requiring revision surgery
occurred in one patient (1.2%) with one additional patient (1.2%) requiring revision
surgery due to a traumatic injury (fall). Computer-assisted navigation provided accurate
intraoperative data regarding inclination and changes in leg length and was associated
with a low rate of dislocation and revision surgery at 90-day follow-up.
Keywords
total hip arthroplasty - cup position - computer-assisted navigation - leg length
