Femoroacetabular Impingement

DefinitionHip CAM CT 1


Aberrant morphology involving the proximal femur and acetabulum

- usually between the femoral neck and the acetabular rim

- during terminal motion of the hip


Can cause pain secondary to labral and chondral lesions

- may lead to early OA




Childhood conditions

- Perthes




Post trauma

- prior femoral neck fracture


Acetabular retroversion

- posteriorly orientated acetabular opening

- relative prominence of anterior rim

- crossing of anterior and posterior walls on the AP radiograph


Acetabular Crossover Sign


Previous periacetabular osteotomy



- profunda (deep socket)

- breva

- magna

- vara










Cam impingement 


Between head and acetabulum 


Abnormal femoral head morphology

- often with flexion

- damage to anterior labrum and shearing of cartilage (carpet lesions)


Usually young men


CAM lesion x-rayHip Cam LesionHip CT Anterior Cam Lesion


Pincer impingement 


Between neck and acetabulum


Hip Pincer Impingement


Due to overcoverage of femoral head

- profunda, protrusio

- acetabular retroversion / relative anterior rim overcoverage


Damage to anterior labrum




Young active males

- CAM impingement


Middle aged athletic women

- pincer impingement




Groin pain

- with rest

- with activity


Pain with flexion


Clicking from labral tear




Typically limited ROM


AP impingement 

- IR / flexion /  adduction

- most common


Posteroinferior impingement

- full extension and external rotation




True AP

- coccyx and symphysis pubis within 1-2cm of each other 

- for assesment of retroversion / crossover sign

- bony prominence junction anterolateral head and neck

- ossification of labrum

- acetabular spurs


Hip Cam Lesion Xray



- shows CAM


CT reconstruction


Very good for bony morphology


Case 1


CAM Lesion CT


Case 2


Hip Cam CT SagittalHip CT Cam 3DHip Cam CT 3D 2HIp Cam CT 3D 3




Labral lesions


Hip MRI Labral Tear CoronalHip CAM Anterior Labral Degenerative TearHip MRI Labral Lesion


Femoral head morphology / Alpha angle


T1 axial MRI

- circle drawn on circumference of femoral head

- line from centre to where head extends beyond circle

- line drawn to centre of femoral neck at its narrowest

- angle > 55o may be indicative of CAM


Hip MRI Anterior CAMHip CAM Alpha Angle


Beta angle


Distance between pathological head-neck junction and acetabular rim

- hip in 90o flexion




Non Operative


Activity modification


Usually problem does not resolve






Open femoral head arthoplasty with surgical dislocation

Hip arthroscopy


Open femoral head arthoplasty


A.  Surgical dislocation of femoral head


Ganz Osteotomy

- preservation of blood supply

- deep branch of medial circumflex artery most important

- runs posterior to obturator externus

- emerges at superior border of quadratus femoris

- over short external rotators

- then retinacular vessels up anterosuperior neck



- must preserve short external rotators

- trochanteric osteotomy

- greater trochanter slid anteriorly

- has abductors and vas lateralis attached

- capsule divided in lazy S

- preserving capsule over anterosuperior neck 

- reflected subperiosteally off neck (like banana skin)

- dividing lig teres and dislocating hip


B.  Femoral head osteoplasty

- allow flexion of 120o

- rotation of 40o


3.  Acetabular debridement 

- debridement acetabular chondral flaps

- osteotomy of the acetabular rim (up to 1cm)

- reattachment / debridement of labral lesions





- debridement of labral tears

- femoral head osteoplasty





- patient supine

- foot IR full initially, leg extended

- traction applied


Hip Arthroscopy Portal Insertion II


Anterolateral viewing portal

- hip distracted

- under II vision

- guide wire in place

- dilators, insert cannula


Anterior working portal

- triangulate, using II

- anterior labral and CAM resection


Hip Arthroscopy Anterior Portal


Posterior working portal

- accessory for labrum and rim


Assess Cartilage


Hip Arthroscopy Chondral DamageHip Arthroscopy Carpet Lesion


Assess for Labral Tears


Hip Arthroscopy Degenerative Labral Tear From CAM lesionHip scope normal acetabular Labrum


Labral resection

- with long resector


Hip Arthroscopy Initial ViewHip Arthroscopy Post Labral Resection


Acetabular rim resection

- if necessary

- long burr

- difficult to know extent of resection required

- check on II


CAM resection

- flex hip, ER

- T capsulotomy to expose CAM lesion

- performed with long thin scapel

- burr resection of CAM lesion

- again, under II guidance

- put hip through range to ensure adequate debridement

- T capsulotomy exposes CAM well

- isolated reports of hip dislocation


Hip Arthroscopy Labral and Rim ResectionHip Arthroscopy CAM Lesion ExposedHip Arthroscopy CAM resection


FAI Cam Resection 1FAI Cam Resection 2FAI Cam Resection 3






Larson et al Arthroscopy 2009

- retrospective comparison of labral debridement v fixation in CAM / Pincer

- significantly improved hip scores in repair grou

- 67% G/E in debridement

- 90% G/E in fixation


Athletes with CAM


Singh et al Arthroscopy 2010

- 27 Australian Rules Playes

- treatment of chondral lesions / labral lesions / majority with CAM lesions

- high level of satisfaction and 26/27 returned to high level sport




Byrd et al Arthroscopy 2009

- 10 year follow up

- 80% good results if no OA

- 7/8 with OA had THR at mean of 6 years