NEW ORLEANS—Genetics, cartilage type, and other factors may help senior athletes maintain well-functioning hips and stave off osteoarthritis even when radiographic results indicate abnormalities, according to research presented at the 2014 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS).
It is not known whether morphological abnormalities of the hip are compatible with life-long hip function and avoidance of osteoarthritis. Lucas Anderson, MD, from the University of Utah in Salt Lake City, and colleagues sought to investigate the prevalence of radiographic findings consistent with dysplasia and femoroacetabular impingement in senior athletes with well-functioning hips.
A total of 546 senior athletes (55% men, 45% women), average age 67 years (range 50 to 91) participated in this study. Two orthopedic surgeons independently evaluated 1,087 hips (excluding hip fractures) for radiographic signs of dysplasia and femoroacetabular impingement. Alpha angle was measured on frog-lateral and anteroposterior radiographs. Lateral center edge angle, acetabular index, and crossover sign were measured on anteroposterior films. Radiographic interpretations were averaged between 2 observers to assess prevalence of dysplasia, femoroacetabular impingement, and osteoarthritis. Cam femoroacetabular impingement was noted if the alpha angle was 50° or greater on either radiograph. Pincer femoroacetabular impingement was noted if lateral center edge angle was greater than 39°, acetabular index was less than 0°, and/or a positive crossover sign was detected. Dysplasia was noted if center edge angle was less than 20° and/or acetabular index was greater than 10°. A chi-squared analysis was used to assess for associations between osteoarthritis (Tönnis grade 2-3) and dysplasia and femoroacetabular impingement. Dysplasia and femoroacetabular impingement were then analyzed using a mixed-effect logistic regression model.
Nine percent of hips (99) had radiographic evidence for dysplasia; 3% (28) had a lateral center edge angle that was less than 20° and 8% (89) had an acetabular index that was greater than 10°. Just over 80% of hips had radiographic evidence of femoroacetabular impingement; 67% had isolated cam, 8% isolated pincer impingement, and 24% of hips had mixed femoroacetabular impingement. Osteoarthritis was present in 17% of hips; 93% of hips with osteoarthritis also had radiographic femoroacetabular impingement and 10% dysplasia. Hips with osteoarthritis were more likely to have radiographic evidence of femoroacetabular impingement (odds ratio = 3.7). However, 80% of the hips with findings of femoroacetabular impingement had no evidence of osteoarthritis despite the athletes’ age and lifelong activity levels. Femoroacetabular impingement was more prevalent in males than females (odds ratio = 10.7).
While the data suggest that senior athletes with femoroacetabular impingement are at a greater risk for having radiographic evidence of osteoarthritis, a substantial portion of the senior athletes in this study did not have osteoarthritis. While femoroacetabular impingement and dysplasia have historically been associated with development of early osteoarthritis, this study suggests that there may be other factors, such as genetics and cartilage type, which may play a joint-preserving role despite presence of pathomorphology in this series of high-functioning senior athletes.