Distal Femoral Cortical Irregularity at Knee MRI: Increased Prevalence in Youth Competitive Alpine Skiers

Abstract

To compare the prevalence of distal femoral cortical irregularities (DFCIs) at different tendon attachment sites in youth competitive alpine skiers with that in young adults. Materials and Methods:In this secondary analysis of a prospective trial, unenhanced 3-T knee MRI scans obtained in youth competitive alpine skiers were compared with images in control participants of the same age from 2014 to 2019 (Cantonal Ethics Committee Zurich registry number: KEK-ZH-2017-01395) for presence of DFCIs at the femoral attachment of the medial head of the gastrocnemius muscle (MHG) and/or lateral head of the gastrocnemius muscle (LHG) and adductor magnus tendon by two radiologists. DFCI size and tendon attachment position were measured. Tendon attachment position and associated MRI findings (meniscus, cartilage, bone marrow edema, joint effusion, ligaments, tendons) were examined for an association with DFCI. Pearson x 2 , Student t test, logistic regression, and k statistics were applied.Results: Unilateral knee MRI scans obtained in 105 skiers (mean age, 14.8 years 6 0.6 [standard deviation]; 66 boys) and in 105 control participants (mean age, 14.6 years 6 0.5; 59 boys) were evaluated. DFCIs were found in 61 of 105 skiers (58%; 95% confidence interval [CI]: 48.5%, 67.2%) compared with 28 of 105 control participants (27%; 95% CI: 18.9%, 35.7%) (P , .001). Two skiers had more than one DFCI. Distribution of DFCIs for skiers and control participants was 60 of 63 (95.2%) and 26 of 28 (92.8%) at the MHG, three of 63 (4.8%) and one of 28 (3.6%) at the LHG, and zero of 63 (0%) and one of 28 (3.6%) at the adductor magnus attachment site, respectively. Interreader agreement was almost perfect (k = 0.87; 95% CI: 0.80, 0.93). The mean size of MHG-related DFCIs in skiers (3.7 mm) was not different compared to the size of those in control participants (3.4 mm) (P = .32), nor was a difference found for the MHG tendon attachment position in knees with DFCI (63.9 mm vs 63.0 mm, P = .83) or without DFCI (63.6 mm vs 62.8 mm, P = .86). Regarding associated MRI findings, increased signal intensity of the MHG tendon showed a significant association with MHG-related DFCI in both groups (P = .01 for both). Conclusion:A distal femoral cortical irregularity at the attachment sites of tendons was a frequent incidental finding on knee MRI scans, with an increased prevalence in youth competitive alpine skiers.

Cortical Desmoid of the Distal Femur—Incidentaloma or Insertional Tendinopathy?

“…According to this, DFCI is the result of repetitive traction from the medial head of the gastrocnemius muscle at its attachment site on the posteromedial femoral condyle. Apart from the cortical irregularity itself, an increased signal intensity of the tendon as well as paratendinous cystic lesions are observed [2]. This theory is supported by an observation of higher incidence rates of DFCI in physically highly active athletes with frequent activation of the calf muscles, and even in the setting of knee trauma in terms of an acute traction injuries of the medial head of gastrocnemius muscle [11].…”

“…The finding of DFCI was defined as a circumscribed, usually oval area of high signal intensity expanding into bone on fat-suppressed proton density or T2-weighted MRI scans, usually with a thin dark rim at the periphery representing sclerosis [2]. The presence of an accompanying paratendinous cystic lesion is optional (Figure 1).…”

“…The cortical desmoid, in the literature also referred to as distal femoral cortical irregularity (DFCI) or cortical irregularity syndrome, is a common finding in radiological diagnostics of the knee joint [1,2]. DFCI is considered a benign, self-limiting fibrous or fibro-osseous lesion that most frequently occurs in the posteromedial aspect of the femoral condyles or more unusually at the aponeurosis of the adductor magnus muscle [2,3]. On plain radiographs, DFCI appears as a small radiolucent area with surrounding sclerosis.…”

“…Recently, MRI cross-sectional studies on a relevant number of asymptomatic competitive alpine skiers revealed dramatically higher incidences between 58% and 63% [2,9,10], implicating an accumulation of DFCI in ambitious and high-level athletes.…”

“…Subsequently, an insertional tendinopathy of the medial head of the gastrocnemius or adductor magnus muscle due to repetitive mechanical stress at the tendinous attachment sites ("tug lesion") is discussed as a possible pathogenetic explanation [2,3,11]. MRI morphology also reveals signal alterations of the determined tendon attachments itself as well as cyst-like formations adjacent to the DFCI [2]. An association to acute trauma has also been discussed [11].…”