Table 1.

Heterogeneity in defining cam and pincer femoroacetabular impingement across all studies analyzed. In addition, there was heterogeneity in defining acetabular retroversion, focal anterior acetabular overcoverage, coxa profunda, acetabular protrusio, and loss of sphericity of femoral head. MRI (magnetic resonance imaging)

Cam	Pincer
• Alpha angle on radiographs (or MRI)	• Relative acetabular retroversion
○ Greater than 40° on oblique radiograph	○ Cross-over sign
○ Greater than 50° on lateral radiograph	○ Prominent ischial spine sign
○ Greater than 50° on MR arthrogram	○ Positive posterior wall sign
○ Greater than 55° on oblique radiograph	○ Lateral center edge angle greater than 25°
○ Greater than 55° on cross-table lateral radiograph	• Focal anterior overcoverage
○ Loss of sphericity of femoral head	○ Cross-over sign
▪ Extension of lateral epiphysis onto cephalad neck	○ Negative posterior wall sign
▪ Pistol grip deformity with extension of lateral epiphysis down to base of femoral neck	○ Lateral center edge angle greater than 25°
○ Reduction in head-neck offset	• Coxa profunda
○ Bump, herniation pit, and abnormal alpha angle	○ Tear drop (floor of fossa) medial to ilioischial line
	○ Lateral center edge angle greater than 35°
	• Acetabular protrusio
	○ Medial aspect of femoral head medial to ilioischial line
	○ Lateral center edge angle greater than 40°
	• Pincer divot at femoral head-neck junction