Lateral acetabular coverage as a predictor of femoroacetabular cartilage thickness

Abstract

To investigate the correlation between femoroacetabular cartilage thickness and lateral acetabular coverage in patients undergoing hip arthroscopy for a variety of indications. Articular cartilage at the hip is hypothesized to undergo adaptive change secondary to unique patterns of pathomechanical loading which results in a direct relationship between acetabular coverage and femoroacetabular cartilage thickness. A cohort of 252 patients presenting to our dedicated hip preservation service between June 2013 and June 2015 were retrospectively analysed. Preoperative radiographs and MRI studies were obtained for all symptomatic hips and classified according to radiographic lateral center edge angle (LCEA) as follows: normal acetabular coverage (25–40°), acetabular overcoverage (≥40°), borderline dysplasia (20–24.9°) and frank dysplasia (<20°). Femoroacetabular cartilage thickness was measured on a preoperative MRI-scan at the fovea, middle sourcil, and lateral sourcil. In all groups, cartilage thickness was maximized at the lateral sourcil relative to the middle sourcil or fovea (P < 0.001). Furthermore, articular cartilage thickness was significantly increased when comparing one group to successive groups with diminished lateral acetabular coverage. Indeed, multivariate analyses confirmed LCEA to be the strongest determinant of femoroacetabular cartilage thickness compared with age, gender, body-mass index or presence of cam/pincer lesions. Patients with borderline and frank dysplasia exhibit increased values of femoroacetabular cartilage thickness in the weight-bearing zone, potentially indicating a compensatory reaction to the lack of bony coverage. Articular cartilage thickness may serve as an instability marker and inform clinical decision-making for patients with borderline dysplasia.

A Contemporary Look at the Evaluation and Treatment of Adult Borderline and Frank Hip Dysplasia

“…In addition to labral hypertrophy, femoroacetabular cartilage hypertrophy has been identified as a sign of hip dysplasia. 3,32 In a study of 252 patients presenting to a hip preservation service, Ashwell et al 3 examined preoperative MRI scans and found an inverse correlation between the femoroacetabular cartilage thickness and the degree of lateral acetabular bony coverage ( P < .001). Furthermore, a significant difference was found in cartilage thickness among patients with normal acetabular coverage (LCEA = 25°-40°), BHD (LCEA = 20°-24.9°), and frank dysplasia (LCEA <20°) ( P < .001 for all pairwise comparisons).…”

Hip instability: a review of hip dysplasia and other contributing factors

“…Articular cartilage thickness has also been shown to exhibit hypertrophy, particularly in the acetabular roof, in newborns with DDH 13,14 . Adults with borderline or frank dysplasia show a similar trend of femoroacetabular cartilage hypertrophy 15 , which is thought to arise as a compensatory mechanism to weight-bearing and sheer stress. The same may be seen in pediatric patients with DDH after hip reduction by decreasing the medially directed force of the femoral head into the acetabulum 13 .…”

Current knowledge on the genetic background of developmental dysplasia of the hip and the histomorphological status of the cartilage

“…Lateral acetabular coverage correlates with femoroacetabular cartilage thickness, which indicates that the cartilage may transform under certain circumstances. In dysplastic hips, the cartilage at the lateral part was 35% thicker compared with the hips with normal acetabular coverage, suggesting that the hip morphologically changes in response to abnormal joint loading ( 65 ). One study showed a more prominent T2 signal decrease in the outer superficial acetabular cartilage of dysplastic hips during weight loading in comparison with normal hips.…”