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Femoroacetabular Impingement Morphology
MK Jesse, MD; Donna G. Blankenbaker, MD, FACR; B. J. Manaster, MD, PhD, FACR
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KEY FACTS

  • Terminology

    • Imaging

      • Pathology

        • Clinical Issues

          • Diagnostic Checklist

            TERMINOLOGY

            • Abbreviations

              • Femoral acetabular impingement (FAI)
            • Definitions

              • Morphologic abnormality at femoral head-neck junction or acetabulum resulting in osseous &/or labral and cartilaginous impingement
                • Cam type: prominence at femoral head-neck junction impinges anterosuperior acetabulum
                  • Decreased femoral head-neck offset (aspherical femoral head)
                  • Bump at anterolateral femoral head-neck junction: may result from eccentric skeletal maturation
                  • Flat anterosuperior femoral head-neck junction: may reflect subclinical slipped capital femoral epiphysis
                  • Primarily young men
                • Pincer type: prominence of anterior acetabulum leads to impingement on femoral neck
                  • Coxa profunda: acetabulum too deep with excessive surface area
                  • Posterior acetabular deficiency: femoral head shifts posteriorly with hip flexion, increasing coverage by acetabulum anteriorly
                  • Primarily middle-aged women
                • May have both cam and pincer FAI in same patient
                  • Most common morphology is combined

            IMAGING

            • General Features

              • Radiographic Findings

                • MR Findings

                  • Imaging Recommendations

                    • Pitfalls

                      DIFFERENTIAL DIAGNOSIS

                        PATHOLOGY

                        • General Features

                          • Staging, Grading, & Classification

                            • Gross Pathologic & Surgical Features

                              • Microscopic Features

                                CLINICAL ISSUES

                                • Presentation

                                  • Natural History & Prognosis

                                    • Treatment

                                      DIAGNOSTIC CHECKLIST

                                      • Consider

                                        • Image Interpretation Pearls

                                          • Reporting Tips

                                            Selected References

                                            1. Welton KL et al: The anteroposterior pelvic radiograph: acetabular and femoral measurements and relation to hip pathologies. J Bone Joint Surg Am. 100(1):76-85, 2018
                                            2. Petersen BD et al: Lateral acetabular labral length is inversely related to acetabular coverage as measured by lateral center edge angle of Wiberg. J Hip Preserv Surg. 3(3):190-6, 2016
                                            3. Sutter R et al: Assessment of femoral antetorsion with MRI: comparison of oblique measurements to standard transverse measurements. AJR Am J Roentgenol. 205(1):130-5, 2015
                                            4. Byrd JW: Femoroacetabular impingement in athletes: current concepts. Am J Sports Med. 42(3):737-51, 2014
                                            5. Lepage-Saucier M et al: Femoroacetabular impingement: normal values of the quantitative morphometric parameters in asymptomatic hips. Eur Radiol. 24(7):1707-14, 2014
                                            6. Omoumi P et al: Anatomic features associated with femoroacetabular impingement are equally common in hips of old and young asymptomatic individuals without CT signs of osteoarthritis. AJR Am J Roentgenol. 202(5):1078-86, 2014
                                            7. Riley GM et al: MRI of the hip for the evaluation of femoroacetabular impingement; past, present, and future. J Magn Reson Imaging. 41(3):558-72, 2014
                                            8. Tranovich MJ et al: A review of femoroacetabular impingement and hip arthroscopy in the athlete. Phys Sportsmed. 42(1):75-87, 2014
                                            9. Bredella MA et al: Femoroacetabular impingement. Magn Reson Imaging Clin N Am. 21(1):45-64, 2013
                                            10. Dimmick S et al: Femoroacetabular impingement. Radiol Clin North Am. 51(3):337-52, 2013
                                            11. Nepple JJ et al: Coxa profunda is not a useful radiographic parameter for diagnosing pincer-type femoroacetabular impingement. J Bone Joint Surg Am. 95(5):417-23, 2013
                                            12. Petchprapa CN et al: Imaging of chondral lesions including femoroacetabular impingement. Semin Musculoskelet Radiol. 17(3):258-71, 2013
                                            13. Philippon MJ et al: Prevalence of increased alpha angles as a measure of cam-type femoroacetabular impingement in youth ice hockey players. Am J Sports Med. 41(6):1357-62, 2013
                                            14. Rubin DA: Femoroacetabular impingement: fact, fiction, or fantasy? AJR Am J Roentgenol. 201(3):526-34, 2013
                                            15. Sankar WN et al: Femoroacetabular impingement: current concepts and controversies. Orthop Clin North Am. 44(4):575-89, 2013
                                            16. Schmitz MR et al: Spectrum of radiographic femoroacetabular impingement morphology in adolescents and young adults: an EOS-based double-cohort study. J Bone Joint Surg Am. 95(13):e90, 2013
                                            17. Larson CM et al: Arthroscopic debridement versus refixation of the acetabular labrum associated with femoroacetabular impingement: mean 3.5-year follow-up. Am J Sports Med. 40(5):1015-21, 2012
                                            18. Robinson P: Conventional 3-T MRI and 1.5-T MR arthrography of femoroacetabular impingement. AJR Am J Roentgenol. 199(3):509-15, 2012
                                            19. Sutter R et al: Femoral antetorsion: comparing asymptomatic volunteers and patients with femoroacetabular impingement. Radiology. 263(2):475-83, 2012
                                            20. Sutter R et al: How useful is the alpha angle for discriminating between symptomatic patients with cam-type femoroacetabular impingement and asymptomatic volunteers? Radiology. 264(2):514-21, 2012
                                            21. Banerjee P et al: Femoroacetabular impingement: a review of diagnosis and management. Curr Rev Musculoskelet Med. 4(1):23-32, 2011
                                            22. Laborie LB et al: Prevalence of radiographic findings thought to be associated with femoroacetabular impingement in a population-based cohort of 2081 healthy young adults. Radiology. 260(2):494-502, 2011
                                            23. Palmer WE: Femoroacetabular impingement: caution is warranted in making imaging-based assumptions and diagnoses. Radiology. 257(1):4-7, 2010
                                            24. Jessel RH et al: Radiographic and patient factors associated with pre-radiographic osteoarthritis in hip dysplasia. J Bone Joint Surg Am. 91(5):1120-9, 2009
                                            25. Kang C et al: Acetabular labral tears in patients with sports injury. Clin Orthop Surg. 1(4):230-5, 2009
                                            26. Leunig M et al: The concept of femoroacetabular impingement: current status and future perspectives. Clin Orthop Relat Res. 467(3):616-22, 2009
                                            27. Lohan DG et al: Cam-type femoral-acetabular impingement: is the alpha angle the best MR arthrography has to offer? Skeletal Radiol. 38(9):855-62, 2009
                                            28. Pfirrmann CW et al: MR arthrography of acetabular cartilage delamination in femoroacetabular cam impingement. Radiology. 249(1):236-41, 2008
                                            29. Tannast M et al: Femoroacetabular impingement: radiographic diagnosis--what the radiologist should know. AJR Am J Roentgenol. 188(6):1540-52, 2007
                                            30. Blankenbaker DG et al: The painful hip: new concepts. Skeletal Radiol. 35(6):352-70, 2006
                                            31. Martinez AE et al: Os acetabuli in femoro-acetabular impingement: stress fracture or unfused secondary ossification centre of the acetabular rim? Hip Int. 16(4):281-6, 2006
                                            32. Bredella MA et al: MR imaging of femoroacetabular impingement. Magn Reson Imaging Clin N Am. 13(4):653-64, 2005
                                            33. Kassarjian A et al: Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement. Radiology. 236(2):588-92, 2005
                                            34. Siebenrock KA et al: Anterior femoro-acetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am. 85-A(2):278-86, 2003
                                            35. Ito K et al: Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br. 83(2):171-6, 2001
                                            36. Abe I et al: Acetabular labrum: abnormal findings at MR imaging in asymptomatic hips. Radiology. 216(2):576-81, 2000
                                            37. Ferguson SJ et al: The influence of the acetabular labrum on hip joint cartilage consolidation: a poroelastic finite element model. J Biomech. 33(8):953-60, 2000
                                            38. Myers SR et al: Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res. (363):93-9, 1999
                                            39. Tönnis D et al: Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 81(12):1747-70, 1999
                                            Related Anatomy
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                                            Related Differential Diagnoses
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                                            References
                                            Tables

                                            Tables

                                            KEY FACTS

                                            • Terminology

                                              • Imaging

                                                • Pathology

                                                  • Clinical Issues

                                                    • Diagnostic Checklist

                                                      TERMINOLOGY

                                                      • Abbreviations

                                                        • Femoral acetabular impingement (FAI)
                                                      • Definitions

                                                        • Morphologic abnormality at femoral head-neck junction or acetabulum resulting in osseous &/or labral and cartilaginous impingement
                                                          • Cam type: prominence at femoral head-neck junction impinges anterosuperior acetabulum
                                                            • Decreased femoral head-neck offset (aspherical femoral head)
                                                            • Bump at anterolateral femoral head-neck junction: may result from eccentric skeletal maturation
                                                            • Flat anterosuperior femoral head-neck junction: may reflect subclinical slipped capital femoral epiphysis
                                                            • Primarily young men
                                                          • Pincer type: prominence of anterior acetabulum leads to impingement on femoral neck
                                                            • Coxa profunda: acetabulum too deep with excessive surface area
                                                            • Posterior acetabular deficiency: femoral head shifts posteriorly with hip flexion, increasing coverage by acetabulum anteriorly
                                                            • Primarily middle-aged women
                                                          • May have both cam and pincer FAI in same patient
                                                            • Most common morphology is combined

                                                      IMAGING

                                                      • General Features

                                                        • Radiographic Findings

                                                          • MR Findings

                                                            • Imaging Recommendations

                                                              • Pitfalls

                                                                DIFFERENTIAL DIAGNOSIS

                                                                  PATHOLOGY

                                                                  • General Features

                                                                    • Staging, Grading, & Classification

                                                                      • Gross Pathologic & Surgical Features

                                                                        • Microscopic Features

                                                                          CLINICAL ISSUES

                                                                          • Presentation

                                                                            • Natural History & Prognosis

                                                                              • Treatment

                                                                                DIAGNOSTIC CHECKLIST

                                                                                • Consider

                                                                                  • Image Interpretation Pearls

                                                                                    • Reporting Tips

                                                                                      Selected References

                                                                                      1. Welton KL et al: The anteroposterior pelvic radiograph: acetabular and femoral measurements and relation to hip pathologies. J Bone Joint Surg Am. 100(1):76-85, 2018
                                                                                      2. Petersen BD et al: Lateral acetabular labral length is inversely related to acetabular coverage as measured by lateral center edge angle of Wiberg. J Hip Preserv Surg. 3(3):190-6, 2016
                                                                                      3. Sutter R et al: Assessment of femoral antetorsion with MRI: comparison of oblique measurements to standard transverse measurements. AJR Am J Roentgenol. 205(1):130-5, 2015
                                                                                      4. Byrd JW: Femoroacetabular impingement in athletes: current concepts. Am J Sports Med. 42(3):737-51, 2014
                                                                                      5. Lepage-Saucier M et al: Femoroacetabular impingement: normal values of the quantitative morphometric parameters in asymptomatic hips. Eur Radiol. 24(7):1707-14, 2014
                                                                                      6. Omoumi P et al: Anatomic features associated with femoroacetabular impingement are equally common in hips of old and young asymptomatic individuals without CT signs of osteoarthritis. AJR Am J Roentgenol. 202(5):1078-86, 2014
                                                                                      7. Riley GM et al: MRI of the hip for the evaluation of femoroacetabular impingement; past, present, and future. J Magn Reson Imaging. 41(3):558-72, 2014
                                                                                      8. Tranovich MJ et al: A review of femoroacetabular impingement and hip arthroscopy in the athlete. Phys Sportsmed. 42(1):75-87, 2014
                                                                                      9. Bredella MA et al: Femoroacetabular impingement. Magn Reson Imaging Clin N Am. 21(1):45-64, 2013
                                                                                      10. Dimmick S et al: Femoroacetabular impingement. Radiol Clin North Am. 51(3):337-52, 2013
                                                                                      11. Nepple JJ et al: Coxa profunda is not a useful radiographic parameter for diagnosing pincer-type femoroacetabular impingement. J Bone Joint Surg Am. 95(5):417-23, 2013
                                                                                      12. Petchprapa CN et al: Imaging of chondral lesions including femoroacetabular impingement. Semin Musculoskelet Radiol. 17(3):258-71, 2013
                                                                                      13. Philippon MJ et al: Prevalence of increased alpha angles as a measure of cam-type femoroacetabular impingement in youth ice hockey players. Am J Sports Med. 41(6):1357-62, 2013
                                                                                      14. Rubin DA: Femoroacetabular impingement: fact, fiction, or fantasy? AJR Am J Roentgenol. 201(3):526-34, 2013
                                                                                      15. Sankar WN et al: Femoroacetabular impingement: current concepts and controversies. Orthop Clin North Am. 44(4):575-89, 2013
                                                                                      16. Schmitz MR et al: Spectrum of radiographic femoroacetabular impingement morphology in adolescents and young adults: an EOS-based double-cohort study. J Bone Joint Surg Am. 95(13):e90, 2013
                                                                                      17. Larson CM et al: Arthroscopic debridement versus refixation of the acetabular labrum associated with femoroacetabular impingement: mean 3.5-year follow-up. Am J Sports Med. 40(5):1015-21, 2012
                                                                                      18. Robinson P: Conventional 3-T MRI and 1.5-T MR arthrography of femoroacetabular impingement. AJR Am J Roentgenol. 199(3):509-15, 2012
                                                                                      19. Sutter R et al: Femoral antetorsion: comparing asymptomatic volunteers and patients with femoroacetabular impingement. Radiology. 263(2):475-83, 2012
                                                                                      20. Sutter R et al: How useful is the alpha angle for discriminating between symptomatic patients with cam-type femoroacetabular impingement and asymptomatic volunteers? Radiology. 264(2):514-21, 2012
                                                                                      21. Banerjee P et al: Femoroacetabular impingement: a review of diagnosis and management. Curr Rev Musculoskelet Med. 4(1):23-32, 2011
                                                                                      22. Laborie LB et al: Prevalence of radiographic findings thought to be associated with femoroacetabular impingement in a population-based cohort of 2081 healthy young adults. Radiology. 260(2):494-502, 2011
                                                                                      23. Palmer WE: Femoroacetabular impingement: caution is warranted in making imaging-based assumptions and diagnoses. Radiology. 257(1):4-7, 2010
                                                                                      24. Jessel RH et al: Radiographic and patient factors associated with pre-radiographic osteoarthritis in hip dysplasia. J Bone Joint Surg Am. 91(5):1120-9, 2009
                                                                                      25. Kang C et al: Acetabular labral tears in patients with sports injury. Clin Orthop Surg. 1(4):230-5, 2009
                                                                                      26. Leunig M et al: The concept of femoroacetabular impingement: current status and future perspectives. Clin Orthop Relat Res. 467(3):616-22, 2009
                                                                                      27. Lohan DG et al: Cam-type femoral-acetabular impingement: is the alpha angle the best MR arthrography has to offer? Skeletal Radiol. 38(9):855-62, 2009
                                                                                      28. Pfirrmann CW et al: MR arthrography of acetabular cartilage delamination in femoroacetabular cam impingement. Radiology. 249(1):236-41, 2008
                                                                                      29. Tannast M et al: Femoroacetabular impingement: radiographic diagnosis--what the radiologist should know. AJR Am J Roentgenol. 188(6):1540-52, 2007
                                                                                      30. Blankenbaker DG et al: The painful hip: new concepts. Skeletal Radiol. 35(6):352-70, 2006
                                                                                      31. Martinez AE et al: Os acetabuli in femoro-acetabular impingement: stress fracture or unfused secondary ossification centre of the acetabular rim? Hip Int. 16(4):281-6, 2006
                                                                                      32. Bredella MA et al: MR imaging of femoroacetabular impingement. Magn Reson Imaging Clin N Am. 13(4):653-64, 2005
                                                                                      33. Kassarjian A et al: Triad of MR arthrographic findings in patients with cam-type femoroacetabular impingement. Radiology. 236(2):588-92, 2005
                                                                                      34. Siebenrock KA et al: Anterior femoro-acetabular impingement due to acetabular retroversion. Treatment with periacetabular osteotomy. J Bone Joint Surg Am. 85-A(2):278-86, 2003
                                                                                      35. Ito K et al: Femoroacetabular impingement and the cam-effect. A MRI-based quantitative anatomical study of the femoral head-neck offset. J Bone Joint Surg Br. 83(2):171-6, 2001
                                                                                      36. Abe I et al: Acetabular labrum: abnormal findings at MR imaging in asymptomatic hips. Radiology. 216(2):576-81, 2000
                                                                                      37. Ferguson SJ et al: The influence of the acetabular labrum on hip joint cartilage consolidation: a poroelastic finite element model. J Biomech. 33(8):953-60, 2000
                                                                                      38. Myers SR et al: Anterior femoroacetabular impingement after periacetabular osteotomy. Clin Orthop Relat Res. (363):93-9, 1999
                                                                                      39. Tönnis D et al: Acetabular and femoral anteversion: relationship with osteoarthritis of the hip. J Bone Joint Surg Am. 81(12):1747-70, 1999