Skiers Have Increased Risk of Distal Femoral Cortical Irregularity

By Lisa Rappaport

July 09, 2020

(Reuters Health) - Youth competitive alpine skiers have a higher prevalence of distal femoral cortical irregularities (DFCIs) than peers outside the sport, a recent study suggests.

Researchers compared unilateral MRI scans from 105 alpine skiers (mean age 14.8 years) with scans for 105 control participants of the same age who didn't ski. They found a total of 63 DFCIs in 61 knees of the skiers (58%) at femoral tendon attachment sites, compared with a total of 28 DFCIs in 28 knees among the control participants.

Youth competitive alpine skiers are exposed to periodic high physical activity and loading patterns to the knee joint that are likely to affect the bones and connective tissue of the joint, which are still maturing and therefore are more vulnerable to injury, said lead study author Dr. Christoph Stern, a musculoskeletal radiologist at Balgrist University Hospital in Zurich, Switzerland.

"Competitive skiing is a sport with unique motion patterns and with repetitive strain of the gastrocnemius muscles, predominantly to the inside muscle head, which causes increased stress to the tendon attachment site where DFCI occur," Dr. Stern said by email. "Thus, the accumulation of such adverse loading patterns over time might serve as a potential explanation for the higher prevalence of DFCI in youth competitive alpine skiers."

Among the skiers in the study, 60 of the 63 DFCIs were at the femoral attachment of the medial head of the gastrocnemius muscle (MGH) and three were at the lateral head of the gastrocnemius muscle (LGH). None were found at the adductor magnus attachment point.

In the control group, 26 of the 28 DFCIs were at the MGH, one was at the LGH, and one was at the adductor magnus attachment site.

There was no significant difference in the size of MGH-related DFCIs between the skiers and the controls (mean 3.7mm v 3.4mm, respectively).

There was also no significant difference between skiers and controls in the craniocaudal position of MGH attachment with DFCI (63.9mm v 63mm) or without DFCI (63.6mm v 62.8mm).

Researchers found an increased signal intensity of the MGH tendon among 40 of the 105 skiers and 15 of 105 controls.

Compared to people without increased signal intensity, both skiers and controls who did experience increased signal intensity were more likely to have MGH-related DFCI (odds ratio 3.7 and 5.6, respectively).

One limitation of the study is that there were different MRI protocols for the skiers and the control group, the researchers note in Radiology.

No other sports with repetitive loading and different mechanisms, such as running, or football were investigated, making it impossible to examine the potential impact of other types of mechanical loads on DFCI risk, said Dr. Alberto Grassi, an orthopedic surgeon at IRCCS Istituto Ortopedico Rizzoli in Bologna, Italy, who wasn't involved in the study.

In addition, the lack of follow-up MRI means it's unclear what happens to these lesions, if they disappear or worsen, or even if they appear in previously negative patients, Dr. Grassi said by email.

Nonetheless, the results underscore that DFCI may often be benign, Dr. Grassi said.

"It could be an incidental finding and not a malignancy, so follow-up is required only if symptomatic," Dr. Grassi advised. "MRI in young skiers should be recommended only in the case of acute traumas or symptomatic overuse injuries, and treatment should be tailored based on symptoms and not on MRI features, similarly to many other musculoskeletal conditions."

SOURCE: Radiology, online June 16, 2020.