May 11, 2015
August 5, 2015



– Increasing recognized cause of hip pain

– FAI was first characterized by Smith-Petersen in 1936 in the setting of old SCFE

– Interest in FAI has increased over the past 10 years with a sig increase in publications on the topic

– Concerns related to risk of developing labral tears and advancing hip OA

FAI is “a clinical entity in which a pathological, mechanical process causes hip pain when morphological abnormalities of the acetabulum and/or femur, combined with vigorous hip motion (especially at the extremes), lead to repetitive collisions that damage the soft-tissue structures within the joint itself.”


CAM: Abnormal morphology of the ant femoral head/neck junction

PINCER: over coverage (overgrowth of anterior aspect of acetabulum) or retroversion of the acetabulum.

Figure 1 – a – normal hip, b – CAM type deformity of neck, c – pincer type deformity of acetabulum



CAM lesions more common in males with ratio of 3:2 in N/A

Pincer more common in women with a 3:1 ratio

Typically becomes symptomatic within the 2nd or 3rd decade



Impingement caused by contact between the femoral head and acetabular rim during hip movement. This repeated contact/friction can lead to labral tear or detachment and injury to the articular cartilage. The causative role in development of early arthritis is somewhat controversial


Anterior hip or groin pain aggravated with hip flexion, twisting/turning, lateral movements.  Pain can occur with kicking motions, getting in and out of a car or rolling to get out of bed.  May also have clunking, clicking, catching if labral tears present


Labral tears, Iliopsoas snapping, tendinopathy, Athletic pubalgia, psoas abscess, psoas bursitis, stress fractures (Femoral neck, pubic ramus), femoral hernia, rectus femoris strain, psoas strain.



– Pain with flexion/adduction/internal rotation (FADIR) of the hip with the patient supine; not specific to FAI

Pincer FAI

The postero-inferior impingement sign: patient supine with examined leg at the edge of the table, the patient extends the hip, while the examiner passively externally rotates the hip.

Limited hip IR ROM at 90 degrees however note there is variation in normal hip ROM , compare to contralateral side

Figure 2 – A: FADIR; B: Post-inf impingement signFAIexam


CAM impingement defined by

– alpha angle > 55, (some papers site 60)

Pincer impingement defined by : crossover sign, coxa profunda, or protrusion acetabula



– Initial mode of investigation if condition suspected

-AP pelvis, cross table lateral, Dunn view

– alpha angle measured on Dunn view, best at looking at femoral neck/head contour

– herniation pit may be a sign of FAI, 30% prevalence in pathological FAI but may be present in asymptomatic people (4)

MR arthrography

– best to assess articularr cartilage, labral pathology.

– recommend inclusion of long acting local anesthetics for diagnostic purposes. Temporary relief of patient’s symptoms helps confirm intra articular source


Most useful for assessing bony anatomy and for arthroscopic correction

Cross over sign indicating over coverage of acetabulum

– The anterior (white dots) and posterior (black dots) rim of the acetabulum

Image courtesy of J.W. Thomas Byrd, MD.


Limited literature on non operative management

Conservative: Rest from sport, aggravating activity, NSAIDs/analgesics, Physio (available evidenced based literature suggests there may be some evidence for hip muscle strengthening and addressing hip flexor tightness).


Indications once diagnosis confirmed:

Persistent hip pain and mechanicals sx’s after failure of conservative mx for at least 6 weeks

? indicated in patients with min to no osteoarthrtitic changes

Open vs arthroscopic and can involve: osteochondroplasty of the femoral head-neck junction, acetabular rim trimming, labral debridement, and/or suture refixation, with partial psoas tendon release

Both open and arthroscopic procedures appear to be equally safe and effective including skeletally immature population


OA and FAI

Epidemiological studies reveal an association between OA and CAM lesions, no clear association between pincer and OA.
CAM deformity and decreased internal rotation lead to a PPV of developing OA >50%.

Figure 3,4,5,6 – Xray of FAI that has developed into OA:  Bilateral CAM and Pincer (a – AP, b – AP with CAM hilighted in green, Pincer in orange, Lateral left hip, lateral left hip with pincer hilighted)



Dr. Kevin Asem ( August 5, 2015 – PRND)


1) Genovese E, Spiga S, Vinci V, Aliprandi A, Di Pietto F, Coppolino F, Scialpi M, Giganti M. Femoroacetabular impingement: role of imaging. 2013 Aug;97 Suppl 2:S117-26. doi: 10.1007/s12306-013-0283-y. Epub 2013 Aug 15.

2) Aliprandi A1, Di Pietto F, Minafra P, Zappia M, Pozza S, Sconfienza LM. Femoro-acetabular impingement: what the general radiologist should know. Radiol Med. 2014 Feb;119(2):103-12. doi: 10.1007/s11547-013-0314-7. Epub 2013 Nov 26.

3) Grant AD1, Sala DA, Schwarzkopf R. Femoro-acetabular impingement: the diagnosis-a review. J Child Orthop. 2012 Mar;6(1):1-12. doi: 10.1007/s11832-012-0386-2. Epub 2012 Feb 29.

4) Byrd J.W., Femoroacetabular Impingement in Athletes: Current ConceptsAm J Sports Med 2014 42: 737

5) de Sa D, Cargnelli S, Catapano M, Bedi A, Simunovic N, Burrow S, Ayeni OR. Femoroacetabular impingement in skeletally immature patients: a systematic review examining indications, outcomes, and complications of open and arthroscopic treatment. Arthroscopy. 2015 Feb;31(2):373-84. doi: 10.1016/j.arthro.2014.07.030. Epub 2014 Sep 26.

6) Yeung M1, Khan M2, Schreiber VM3, Adamich J2, Letkemann S2, Simunovic N2, Bhandari M2, Musahl V3, Philippon MJ4, Safran MR5, Ayeni OR2. Global discrepancies in the diagnosis, surgical management, and investigation of femoroacetabularimpingement. Arthroscopy. 2014 Dec;30(12):1625-33. doi: 10.1016/j.arthro.2014.06.008. Epub 2014 Aug 20.

7) Rubin DA. Femoroacetabular impingement: fact, fiction, or fantasy? AJR Am J Roentgenol. 2013 Sep;201(3):526-34. doi: 10.2214/AJR.13.10913.

8) Grant AD1, Sala DA, Schwarzkopf R. Femoro-acetabular impingement: the diagnosis-a review. J Child Orthop. 2012 Mar;6(1):1-12. doi: 10.1007/s11832-012-0386-2. Epub 2012 Feb 29.

9) Wall PD1, Fernandez M, Griffin DR, Foster NE. Nonoperative treatment for femoroacetabular impingement: a systematic review of the literature. PMR. 2013 May;5(5):418-26. doi: 10.1016/j.pmrj.2013.02.005. Epub 2013 Feb 16.

10) Byrd JW1. Femoroacetabular impingement in athletes: current concepts. Am J Sports Med. 2014 Mar;42(3):737-51. doi: 10.1177/0363546513499136. Epub 2013 Aug 27.

11) Agricola R and Weinans H. Femoroacetabular impingement: what is its link with osteoarthritis? Br J Sports Med published online June 24, 2015

12) Agricola R and Weinans H What is femoroacetabular impingement?  Br J Sports Med published online June 30, 2015

A properly centered anteroposterior radiograph must be controlled for rotation and tilt. Proper rotation is confirmed by alignment of the coccyx over the symphysis pubis (vertical line). Proper tilt is controlled by maintaining the distance between the tip of the coccyx and the superior border of the symphysis pubis at 1 to 2 cm. Image courtesy of J.W.

Thomas Byrd, MD