Introduction: Cam-type femoroacetabular impingement (FAI) is a pathoanatomical hip condition associated with hip and/or groin pain in the athlete. Cam-type FAI is characterised by a bony lesion on the anterosuperior quadrant of the femoral head-neck junction and is aggravated by activities that place the hip joint in positions of end-range hip flexion and internal rotation. The cam lesion is often assessed using alpha angle measures of the femoral head-neck junction on MRI, CT or X-ray, with angles ≥60° suggested to indicate a cam lesion. Using such approaches, the cam lesion has been reported in 25% of young active males and ~70% of male athletes.
Purpose: To study the prevalence and characteristics of the cam lesion and self-reported hip and/or groin pain among high-performance male water polo players.
Methods: Fifteen senior male water polo players (senior group-SG) and thirteen emerging male water polo players (emerging group-EG) with and without a history of hip and/or groin pain were examined. 3D MR examination with radial plane image reformation was used to visualise the anterosuperior and anterior regions of the femoral head-neck junction in both limbs. Anterosuperior and anterior alpha angles were measured to assess the presence/absence of the cam lesion, with alpha angles ≥ 60° dichotomously classified as indicating a cam lesion. In a subsample of 36 limbs, a radiologist graded the anterosuperior region of the femoral head-neck junction using a three-point cam lesion grading scale. In all participants, hip and/or groin pain was assessed using question 1 from the pain subscale of the Copenhagen Hip and Groin Outcome score (HAGOS).
Results: Overall, 13/15 (87%) of the players from the SG and 10/13 (77%) of the players from the EG had an alpha angle which exceeded the pre-determined dichotomous MRI criteria for a cam lesion in either one or both limbs. There was a significantly greater proportion of players with bilateral cam lesions in the SG (12/15) compared with the EG (4/13) (p= 0.002, two sided Fischer’s Exact test). Overall, 69% (9/13) of SG players and 33% (4/12) of EG players reported at least monthly hip and/or groin pain in one or both limbs. There was no significant difference between the proportion of self -reported hip and/or groin pain among limbs that met/did not meet the dichotomous MRI criteria for a cam lesion (p = 0.1695, one-sided Fischer’s Exact test). A one-way ANOVA with post hoc testing (Tukey HSD) indicated that limbs classified as having a prominent/severe cam lesion had significantly larger alpha angles than limbs classified as having either a evident/minor cam lesion (p = 0.037) or not having a cam lesion (p < 0.001).
Discussion: This study found that cam lesions, determined by anterior/anterosuperior alpha angle measures of radial MR images of the femoral head-neck junction, were common in the senior and emerging high-performance male water polo players. The larger anterior alpha angles and higher cam lesion prevalence in the senior water polo players observed in this study likely reflects a complex bony remodelling of the femoral head-neck junction in response to ageing and prolonged exposure to repetitive hip impingement related to sport specific loading (i.e., eggbeater kick). The findings of this initial research study highlight that cam lesions are a relatively common finding among high-performance male water polo players and may be associated with hip and/or groin pain and joint injury among these athletes.