Elite Rowers Demonstrate Consistent Patterns of Hip Cartilage Damage Compared With Matched Controls: A T2* Mapping Study
Authors: Bittersohl Bernd , Benedikter Chiara , Franz Alexander , Hesper Tobias , Schleich Christoph , Antoch Gerald , Hosalkar Harish S. , Krauspe Rüdiger , Zilkens Christoph 
Published: December 2018

Abstract

Background
Rowing exposes the femoral head and acetabulum to high levels of repetitive abutment motion and axial loading that may put elite athletes at an increased risk for developing early hip osteoarthritis.

Questions/purposes
Do elite rowers demonstrate characteristic hip cartilage lesions on T2* MRI sequences compared with asymptomatic individuals who do not row?

Methods
This study included 20 asymptomatic rowers (mean age, 23 ± 3 years; nine females, 11 males) who had a minimum of 5 years of intensive (≥ 12 hours/week) training. The recruiting of the rowers took place from the central German federal rowing base, which has inherent intense training and selection requirements to declare these athletes as “elite rowers.” We investigated one hip per study participant. MRI was performed on a 3-T scanner. The protocol included standard sequences, a double-echo steady-state sequence, and a multiecho data image combination sequence with inline T2* calculation (= the decay of transverse magnetization arising from molecular interactions [T2] and inhomogeneities in the magnetic field resulting from tissue susceptibility-induced field distortions and variations in the magnet itself), which detects changes in water content and the disruption of collagen structure. Although extrinsic and intrinsic influences on the T2* values including diurnal effects, MR technic-derived variations, and anatomic-related regional disparities need to be taken into account, low T2* values well below 20 ms indicate cartilage degeneration. Cartilage was morphologically analyzed in the anterior, anterosuperior, superoanterior, superior, superoposterior, posterosuperior, and posterior regions of the hip and graded as follows: Grade 0 = normal; Grade 1 = signal changes; Grade 2 = cartilage abrasion; Grade 3 = cartilage loss. Labrum was classified as follows: Grade 0 = normal; Grade 1 = partial tear; Grade 2 = full-thickness tear; Grade 3 = labrum degeneration. The T2* measurement was done through a region of interest analysis. For reliability assessment, morphologic evaluation and T2* measurement were performed by two observers while one observer repeated his analysis with a time interval > 2 weeks. Intra- and interobserver reliability was determined using κ analysis and intraclass correlation coefficients. Control T2* data were derived from a previous study on 15 hips in 15 asymptomatic volunteers of similar ages (seven males and eight females) who were not competitive rowers with similar MR hardware and imaging sequences.

Results
Compared with the control group of asymptomatic volunteers who were not competitive rowers, we noted a high level of labrum and cartilage degeneration in the cohort of elite rowers. In the group of elite rowers, cartilage degeneration was noted in all hips. Regarding the acetabular cartilage, 271 zones could be evaluated. Of those, 44% (120 of 271) were graded normal, 6% (15 of 271) revealed signal alteration, 45% (122 of 271) demonstrated cartilage abrasion, and 5% (14 of 271) were noted to have full-thickness cartilage loss. Morphologic cartilage degeneration in the femoral head was less frequent. T2* values were lower than the control hips in all zones except for the posterior central acetabular zone (global T2* acetabular: 20 ± 6 ms, range, 9–36 ms, 95% confidence interval [CI], 19–21 ms versus 25 ± 5 ms, range, 14–44 ms, 95% CI, 24–25 ms, p < 0.001; global T2* femoral: 23 ± 7 ms, range, 9–38 ms, 95% CI, 22–24 ms versus 27 ± 5 ms, range, 17–45 ms, 95% CI, 26–28 ms, p < 0.001). The difference in T2* between the two study groups was superior in the peripheral zone of the anterosuperior region (16 ± 3 ms; range, 10–22 ms, 95% CI, 15–18 ms versus 26 ms ± 5 ms, range, 18–38 ms, 95% CI, 24–29 ms, p < 0.001).

Conclusions
We found signs of hip cartilage degeneration to a much greater degree in elite rowers than in asymptomatic controls. Although causation cannot be inferred, this is concerning, and future investigations including controlled longitudinal studies both on elite and nonelite athletes with sufficient cohort size are warranted to clarify our findings.

Level of Evidence
Level III, therapeutic study.