Precision and Accuracy of Identification of Anatomical Surface Landmarks by 30 Expert Hip Arthroscopists
We conducted a study to assess 30 expert hip arthroscopists’ ability to identify common surface landmarks used during hip arthroscopy. Thirty hip arthroscopists independently performed a blinded examination of an awake supine human volunteer for identification of 5 surface landmarks: anterior superior iliac spine (ASIS), tip of greater trochanter (GT), rectus origin (RO), superficial inguinal ring (SIR), and psoas tendon (PT). The examiners applied the labels ASIS, GT, RO, SIR, and PT to the landmarks. An ultrasonographer performed a musculoskeletal ultrasound examination and applied labels as well, and a photographer documented the examiner labels after obtaining overhead and lateral digital images with use of fixed camera mounts. Digital overlay composite images of arthroscopist and ultrasonographer labels were analyzed. Direction and distance of inaccurately placed labels were compared with known values for neurovascular structures previously reported for common arthroscopic portals. Average distance from examiner-applied labels to ultrasonographer-applied labels was 31 mm for ASIS, 24 mm for GT, 26 mm for RO, 19 mm for SIR, and 35 mm for PT. Interobserver variability of examiner-applied labels was recorded as areas of 95% predictive interval: 65 cm2 for ASIS, 16 cm2 for GT, 221 cm2 for RO, 38 cm2 for SIR, and 29 cm2 for PT. Examiner labels demonstrated the highest potential for injury because of anterior portal inaccuracy. Expert hip arthroscopists varied in their ability to accurately and precisely identify common surface landmarks about the hip, using only manual palpation.
Limitations
This study had several limitations. The surgeons were limited to palpation and static examination of a body in its natural state. Hip arthroscopic portals typically are created under traction and after a standard perineal post is placed for hip arthroscopy. In addition, in an awake injection setting, the clinician may receive patient feedback in the form of limb movement or speech. To what degree palpation or ultrasound will be affected in these scenarios is unknown.
Another limitation is the lack of serial examination by each examiner—intrarater variability could not be gauged. In addition, with only 1 ultrasonographic examination performed, there is the potential that adding ultrasonographic examinations, or having an examiner perform serial physical examinations, could better define the precision of each component. Given the practical limitations of our volunteer’s time and the schedules of 30 expert arthroscopists, we kept the chosen study design for its single setting.
Conclusion
Visual inspection and manual palpation are standard means of identifying common surface anatomical landmarks for the creation of arthroscopy portals and the placement of injections. Our study results showed variance in landmark identification between expert examiners and an ultrasonographer. The degree of variance exceeded established neurovascular safe zones, particularly for AP and MAP. This new evidence calls for further investigation into the best, safest means of performing hip arthroscopic techniques and injection-based interventions.
Am J Orthop. 2017;46(1):E65-E70. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.
