Table 1

Primary cam morphology, its defining attributes and empirical referents; quotes from articles in italics (refer to online supplemental material folder 3 for more detail)

AttributeDescriptionEmpirical referent
Attribute 1: tissue types involved in primary cam morphologyDistinguish between bone and soft tissue (cartilage) on MRICartilage: 3 T MRI.
Bone: radiographs, CT scan, MRI.
Attribute 2: the size of primary cam morphologySmall; moderate; large; pathological; significant; severeAlpha angle (degrees), impingement angle (degrees), offset measure (mm), offset ratio, FHR of Murray, triangular index, relationship between the width of the femoral neck and diameter of the femoral head. Outcome variables are continuous and/or dichotomous using different cut-off values: alpha angle (≥50°, >50°,≥50.5°, >50.5°,>51°,>55°, ≥55°, >57°, >60°, >62°, >62.5°, >65°, >78°, >83°), head-neck offset <8 mm, anterior offset ratio <0.135, FHR >1.35, triangular index ≥0 mm.
Attribute 3: the site (location) of primary cam morphologyFemur; femoral head-neck; superior; anterior; inferior; posterior; lateral-lateral;
12 to 11 o’clock positions
Radiographs; CT scans or MRI.
CT scan or MRI.
Attribute 4: the shape of primary cam morphologyCam-shape; pistol-grip deformity; bump; hump; flattening; aspherical; oval-shapedQualitative judgement or quantified on radiographs, CT scans or MRI.
Attribute 5: ownership of primary cam morphologyMore common in asymptomatic males (vs females)
More common in asymptomatic athletes/sporting cohorts (vs non-athletes)
Reported: males vs females; athletes vs non-athletes
One hip (unilateral); both hips (bilateral); left and right hips;
Reported: per hip; per person; both per hip and per person
Qualitative judgement or quantified on radiographs, CT scans or MRI.
Cam-type deformities were seen in 868 male and 1192 female participants, respectively, as follows: pistol grip deformity, 187 (21.5%) and 39 (3.3%)’41;
‘Males participating in competitive sport are at particularly elevated risk of developing cam morphology…’23;
‘…CAM impingement is more common in the elite ice hockey athlete in comparison with non-athletes’69;
when a cam deformity was present in either view in either hip’92;
‘flattening or prominence in at least one hip in either AP or frog-leg lateral view’93;
‘randomly assigned one hip to be evaluated for each athlete’24;
‘To investigate the differences between ethnicities in the continuous measures, a univariate linear regression model with generalized estimating equations (GEE) was used to account for the correlation between the left and right hips of each individual’.94
  • FHR, femoral head ratio.