Is there a distinct pattern to the acetabular labrum and articular cartilage damage in the non-dysplastic hip with instability?

Abstract

Purpose: The purpose of this study was to determine whether or not there is a distinct pattern of injury to the acetabular labrum and/or cartilage in the hip with instability without bony dysplasia.

Methods: Surgical records and intra-operative images of consecutive patients who underwent primary hip arthroscopy for femoroacetabular impingement (FAI) and/or hip instability by the senior author from April 2007 to December 2014 were retrospectively reviewed. Pathological changes were documented and charted on a novel diagram of the acetabulum, and classified into eight patterns corresponding to the lesion's location and size. In patients who had acetabular chondroplasty treatment, the width of the cartilage lesion was recorded.

Results: A total of 953 hips in 886 patients were included, and patients who met our inclusion/exclusion criterion were grouped into an Instability-Only group (45 hips), an Instability-Dysplasia group (12 hips), as well as Pincer-FAI, Cam-FAI, and Combined-FAI groups consisting of 100, 54, and 269 hips, respectively. In the Instability-Only group, 42.2 % of the chondral and labral lesions demonstrated a "Straight-Anterior" pattern, which proportion was statistically significantly different compared with Pincer-FAI (p < 0.000), Cam-FAI (p = 0.0002), and Combined-FAI (p < 0.000) groups. In Instability-Only patients, only 15.6 % of the lesions had an "Anterior to Lateral" pattern, a significantly lower proportion (p < 0.000) compared with the FAI groups. Also 11.1 % of the lesions demonstrated a "Lateral" pattern, which is a significantly greater proportion compared with Pincer-FAI (p < 0.000) and Combined-FAI (p < 0.000) groups. The mean width of the cartilage lesions for the Instability-Only group was 2.9 mm, which was significantly shallower than for the other FAI groups (p < 0.000).

Conclusion: A significant predilection of "Straight-Anterior" or "Lateral" location of labral and/or cartilage damage was observed in the hip with instability, while there was shallow width of articular cartilage damage in these patients. These results suggest that there is a distinctive labral and cartilage damage pattern for hips with instability without inherent bony dysplasia.

Level of evidence: Diagnostic study, Level IV.

Keywords: Femoroacetabular impingement; Hip arthroscopy; Hip instability.