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 pelvis radiograph


Previous periacetabular osteotomy



- profunda (deep socket)

- breva

- magna

- vara




Many are idiopathic

- very common in sports

- i.e. soccer, hockey

- perhaps there is an abnormality that develops at the proximal femoral epiphysis






Mixed - CAM and Pincer


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


Hip CT Anterior Cam Lesion


Pincer impingement 


Between neck and acetabulum


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


AP Pelvis


Lateral / Dunn view

- shows CAM


CT reconstruction


Very good for bony morphology of the CAM


Case 1


CAM Lesion CT


Case 2


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


Case 3: Subspine Impingement


Subspine Impingement 1Subspine impingement 2




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


Core strengthening



- pain < 1 year

- OA


Hip Arthroscopy Anterior PortalHip Pincer Impingement

Hip Cam LesionHip Arthroscopy Chondral Damage







Open femoral head arthoplasty with surgical dislocation - now rearely done


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 / repair of labral tears

- femoral head osteoplasty





- patient supine

- foot IR full initially, leg extended

- traction applied


Hip Arthroscopy Portal Insertion II




Proximal anterolateral viewing portal (PALA)

- hip distracted

- under II vision

- guide wire in place

- dilators, insert cannula


Mid Anterior working portal

- triangulate, using II

- anterior labral and CAM resection


Posterior working portal

- accessory for labrum and rim

- rarely used

- can be used to remove loose bodies


Distal anterolateral Working Portal (DALA)

- between midanterior and PALA
- useful for labral repair


Labral Repair


Assess for Labral Tears


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

Hip Arthroscopy Carpet Lesion


Labral resection

- with long resector

- rarely performed now

- if labrum irreparable or ossified


Hip Arthroscopy Initial ViewHip Arthroscopy Post Labral Resection


Acetabular rim resection / Acetabuloplasty

- 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




RCT Surgery v Nonoperative


Griffin Lancet 2018

- 348 patients randomized to surgery v personalized hip therapy

- 1 year follow up, significant improvements in hip arthroscopy group


Labrum Repair v Debridement


Larson et al Arthroscopy 2009

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

- significantly improved hip scores in repair group

- 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