Purpose
The ability to predict the acetabular labral height based on pre-operative advanced imaging compared to intra-operative measurement has been evaluated in the past with mixed findings. However, it has not been studied in the revision setting in which advanced arthroscopic techniques, such as labral augmentation or reconstruction, may be indicated due to poor quality or deficiency of labral tissue. The purpose of this study was to compare magnetic resonance imaging (MRI) labral height and intraoperative labral height measurements in revision hip arthroscopy.
Methods
Patients who underwent revision hip arthroscopy with labral repair by a single surgeon from January 2008 to
December 2015 were identified retrospectively from a prospectively collected database. The height of the labrum was measured intraoperatively at the time of surgery. Two orthopaedic surgeons performed labral height measurements on MRI at 3 standardized locations using the clockface method at two time points 4 weeks apart. Inter- and intraobserver reliabilities were calculated as were comparisons between intraoperatively measured labral heights and MRI measurements at the three positions.
Results
Fifty-eight patients who underwent revision hip arthroscopy were enrolled in the study. The average labral height measurements at the 3, 12, and 9 o’clock positions were 7.4 mm (± 1.2), 7.5 mm (± 1.4), and 6.6 mm (± 1.2), respectively, on MRI compared to 6.7 mm (± 2.1), 6.5 mm (± 2.5), and 7.0 mm (± 1.9), respectively, when measured intraoperatively. The average intraoperative measurements were smaller than the MRI measurements at the 3 (p=.03) and 12 (p=.01) o'clock positions. The inter-rater ICCs between the two surgeons exhibited good agreement (.612) at the 3 o’clock position, fair agreement (.498) at the 12 o’clock position, and poor agreement (.171) at the 9 o’clock position. The positive predictive value (PPV) of the MRI was 72% at 3 o'clock, 68% at 12 o'clock, and 88% at 9 o’clock for identifying a labrum 6 mm or greater.
Conclusion
Measuring labral height on MRI yielded, on average, a value that was larger than the intraoperative measured height in revision hip arthroscopy procedures. Further investigation is needed to better image the labrum after primary hip arthroscopy to discern its dimensions in an effort to help streamline the approach to preoperative evaluation and planning for revision arthroscopy.
Keywords
labral height; MRI; intraoperative measurements;