Elevated ARI May Be Indicator for Chondral Lesions

Poster presentation examines influence of radiologic findings on intra-articular damage

Peter Pollack

Acetabular retroversion is a condition linked to femoral acetabular impingement (FAI). In Scientific Poster P081, “Acetabular Retroversion and Femoroacetabular Impingement: The Importance of Acetabular Retroversion Index,” Bahar Adeli, BA, suggests that systematic evaluation of acetabular retroversion could provide clinicians with an important radiologic marker to help predict chondral damage.

“Although various radiologic signs indicative of acetabular retroversion have been described, the prognostic value of these signs have not been well understood,” explained Mr. Adeli. His poster describes his attempt to evaluate the influence of radiologic findings on the extent of intra-articular damage detected during surgical intervention, and develop an operational definition for focal acetabular overcoverage to assist with clinical decisions.

He identified 93 patients with acetabular retroversion (47 men and 46 women) who underwent surgical treatment for FAI. Preoperative radiographs for all patients were evaluated using software designed to correct the tilt and rotation of the pelvis image. The following four radiologic parameters indicative of acetabular retroversion were evaluated:

crossover sign
posterior wall sign
ischial spine sign
acetabular retroversion index (ARI)

After adjusting for patient age and radiologic arthritis, the author found that ARI of greater than 20 percent was a significant predictor for the absence of chondral lesions. Of the four radiologic parameters examined, ARI was the only marker that significantly correlated with the presence or absence of chondral lesions. Because ARI is a continuous variable, a cutoff point was established based on the results.

Via multivariate analysis, Mr. Adeli produced a predictive model, which he used to determine that ARI of less than 20 percent, Tonnis Grade 0, and age of less than 32 years was associated with an 88 percent probability of absence of chondral lesions.

Mr. Adeli observed no association between radiologic signs and the extent or type of labral tears.

“The systematic evaluation of acetabular retroversion provides relevant preoperative information when dealing with symptomatic patients,” explained the author. “The acetabular retroversion index appears to be the most important radiologic sign that can help predict chondral damage.”

Based on the study data, the author suggests that orthopaedic surgeons take ARI into consideration when dealing with patients with acetabular retroversion.

To view this and other Scientific Posters, visit Academy Hall B; to view this as an iPoster, visit http://aaos.posterview.com

Disclosure—Mr. Adeli reports no conflicts.

2013 Annual Meeting News
Tuesday through Friday, February 19 – 23, 2013.
http://www.aaos.org/news/acadnews/2013/AAOS6_3_19.asp