Background

 

CamCT focal pincerMRI coronal

 

Definition

 

Femoro-acetabular impingement (FAI)

- abnormal contact between the femoral head neck junction and the acetabular rim

- causes pain secondary to labral and chondral lesions

 

Types

 

Cam

Pincer

Mixed - CAM and Pincer

 

Cam impingement

- abnormal femoral head morphology at head neck junction

- loss of sphericity

- typically anterolateral

 

Pincer impingement

 

a. Global

- overcoverage of femoral head

- profunda, protrusio

- acetabular retroversion / relative anterior rim overcoverage

 

b. focal

- os acetabuli

- focal acetabular lesion

 

CT focal pincerLarge os acetabuli

 

Mixed

- combination of pincer and Cam impingement

 

Hip CT Anterior Cam LesionOs acetabuli

 

Epidemiology

 

Hack et al JBJS Am 2010

- MRI of bilateral hips in 200 asymptomatic people

- 14% had Cam deformity in at least one hip

- 80% men, 20% women

 

Gao et al J Orthop Surg Res 2021

- MRI of 125 hips in 70 asymptomatic patients

- 53% of hips had a labral tear

 

Etiology

 

Developmental / sports

- increased incidence of Cam in hockey / basketball / football / soccer

- suggests changes to femoral epiphysis with certain athletic pursuits

 

Pediatric hip disease / SUFE

 

Acetabular retroversion

- posteriorly orientated acetabular opening

- relative prominence of anterior rim

 

Coxa profunda (deep socket) / Protrusio

 

History

 

Groin pain

- with activity

- with flexion

 

C shaped pain

- patient uses hand to grip anterior and posterior hip

 

Examination

 

FADIR (Flexion-adduction Internal Rotation)

 

FABER (Flexion-abduction External Rotation)

 

X-ray

 

True AP

 

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

- exclude osteoarthritis

- pincer

- dysplasia

- retroversion / crossover sign

- os acetabuli / ossification labrum

- bony prominence junction anterolateral head and neck - Cam

 

PincerPincer lateral

Bilateral pincer

 

Ossified labrumOssified labrum
Ossified labrum

 

Os 1Os 2

Os acetabuli

 

45 and 90 degree Dunn view

 

Look for Cam morphology

 

Dunn view 1Dunn view cam

Small Cam on Dunn view                                       Large anterior Cam on Dunn view

 

Alpha angle

 

Measurement

- centered in the center of the femoral head (best fit circle)

- formed by two lines

- one line center of the femoral neck axis

- a line where the femoral head leaves a best-fit circle

- higher alpha angle with Cam lesion

 

Alpha 2Alpha 1

 

Alpha 2Alpha 1

Alpha < 55 degrees                                                   Alpha > 55 degrees

 

Barrientos et al J Hip Preserv Surg 2016

- 38 patients with Cam versus 108 control

- CT scans

- mean 48+/-5 degrees in controls

- mean 67+/-12 degrees in patients with symptomatic Cam

 

Kowalczuk et al Sports Med Arthrosc Rev 2015

- systematic review

- Cam lesions with elevated alpha angles predispose to development of OA

 

Lateral centre edge angle (LCEA)

 

Measurement

- vertical line drawn from the center of the femoral head

- line from the center of the femoral head to the lateral acetabular rim

- normal 20 - 40 degrees

- dysplasia < 20 degrees

- protrusio > 20 degrees

 

Protrusio 1Protrusio 2

Increased LCEA in protrusio

 

MRI

 

Labral tears

 

Best seen on coronal MRI

 

MRI coronal Mri labral MRI labrum 2

 

Saied et al BMC Musculoskeletal Disorders 2017

- systematic review

- labral tears: MRI sensitivity 86% and specificity 83%

- chondral lesions: MRI sensitivity 87% and specificity 72%

- labral tears: MRA sensitivity 91% and specificity 58%

- chondral lesions: MRA sensitivity 75% and specificity 79%

 

Hip MRI Anterior CAMMRI anterior cam

MRI alpha angle

 

CT

 

Cam impingement

 

Hip Cam CT Sagittalcam CT

 

Hip CT Cam 3DHIp Cam CT 3D 3

 

Pincer

 

CT focal pincer

Focal pincer

 

Os acetabuli

 

Os acetabuliLarge os acetabuli

 

Subspine impingement

 

Subspine Impingement 1Subspine impingement 2

Enlarged AIIS likely from old partial avulsion

 

Osteoarthritis

 

Hip arthroscopy OAOA with Cam < 2 mm joint spaceFemoral head osteophytes

 

Tonnis Grade

Grade 0 No sign of arthritis
Grade 1 Sclerosis, slight narrowing of joint space
Grade 2 Cyst, moderate narrowing of joint space, loss sphericity of femoral head
Grade 3 Severe narrowing or obliteration of joint space

TonnisTonnis Grade 0Tonnis grade 2

Tonnis grade 0                            Tonnis grade 1                                 Tonnis grade 1

 

Outcomes of hip arthroscopy and mild OA

 

Ruzbarsky et al AJSM 2023

- 2 year follow up of hip arthroscopy

- < 2 mm joint space 16% conversion to THA

- preserved joint space 2% conversion to THA

 

Skendzel et al AJSM 2014

- 5 year follow up of hip arthroscopy

- < 2mm joint space versus > 2 mm joint space

- 86% with joint space < 2mm had THA at 5 years

- 16% with preserve joint space had THA at 5 years

 

Fenn et al AJSM 2024

- 62 Tonnis grade 0 versus 31 Tonnis grade 1

- minimum 10 year follow up

- 5% THA grade 0 versus 26% THA grade 1

 

Pelvic tilt / acetabular retroversion

 

Definition

 

Acetabular retroversion causes anterior overcoverage

Likely due to rotational abnormality of the hemipelvis

 

Xray diagnosis

 

1.  Crossover sign - crossover of the anterior and posterior acetabular wall

2.  Positive ischial spine sign - intrapelvic protrusion of the ischial spine

3.  Positive posterior wall sign - the posterior wall runs medial to the femoral head center

 

Cross over signCross over

Crossover sign - anterior wall in red, posterior wall in black

 

Alter et al AJSM 2022

- CT versus xray for measurement of retroversion

- crossover sign and ischial spine sign not reliable

 

CT / MRI  diagnosis

 

CT acetabular versionAcetabular version

 

Acetabular version < 15 degrees between B and C

- affected by pelvic tilt and obliquity

- Line A: posterior acetabular walls

- Line B: posterior to anterior acetabular walls

- Line C: perpendicular to line A

 

Acetabular version 1Acetabular version 2

Normal acetabular version > 15 degrees

 

Acetabular version 1Acetabular version 2

Reduced acetabular version < 15 degrees

 

Management

 

Arthroscopy acetabular rim trim

Periacetabular Osteotomy (PAO)

 

Zurmuhle et al CORR 2017

- surgical treatment of acetabular retroversion

- 67 hips undergoing PAO and 57 underwent rim trimming

- no difference in outcomes at 5 years

- 80% 10 year survival for PAO, and 23% survival at 10 years for rim trim

 

Dysplasia

 

Borderline Dysplasia

- LCEA 18 - 25 degrees

 

Lee et al Arthroscopy 2023

- systematic review of hip arthroscopy in borderline dysplasia

- 6 articles and 400 studies

- at minimum 5 years follow up, 70% achieved MCID in at least one outcome

 

Nonoperative management

 

Physiotherapy

 

Probst et al J Orthop Sports Phys Therapy 2023

- meta-analysis of 16 studies of non-arthritic hip pain

- overall response rate to nonoperative treatment was 54%

- physiotherapy improved outcomes by average of 11 points on 100 point scale

 

Injections

 

Takla et al J Orthop 2023

- systematic review of 7 studies and 600 patients

- some association between responsiveness to injections and good outcomes after hip arthroscopy

 

Operative management

 

Operative versus nonoperative treatment

 

Dwyer et al Arthroscopy 2020

- meta-analysis of 3 RCTs and 650 patients

- improved outcomes with operative intervention

 

Griffin et al Lancet 2018

- 348 patients randomized to surgery v personalized hip therapy

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

- mean iHOT-33 scores had improved from 39·2 to 58·8 for hip arthroscopy group

- mean iHOT-33 35·6 to 49·7 in the personalised hip therapy group

 

Operative outcomes

 

Levy et al Arthroscopy 2016

- systematic review of 91 studies and 10,000 hips

- > 90% met MCID

- 88% achieved PASS for mHHS but 25 - 30% for HOS

- 6% revision rate hip arthroscopy

- 6% THA

 

Factors associated with outcomes

 

Sogbein et al Orthop J Sports Med 2019

- systematic review of 39 studies and 9000 hips

- male, Tonnis grade 0, younger age, BMI < 25 and relief with intra-articular injections associated with good outcomes

- female, > 45, < 2 mm joint space, increase LCEA and labral debridement associated with poorer outcomes

 

Labrum Repair v Debridement

 

Su et al Arthroscopy 2024

- 76 labral repairs matched to 76 labral debridement controls

- significant improvement in both groups

- no signficant difference between groups

 

Wirries et al Arthroscopy 2024

- German registry

- 963 labral repair versus 673 labral debridement

- no difference in outcome

- at 5 years > 90% arthroplasty free survival in both groups

- outcomes and THA influenced by cartilage status at time of surgery

 

Cam Resection

 

de Sa et al KSSTA 2014

- systematic review

- correction postoperative alpha angle associated with improved outcomes

 

Lansdown et al AJSM 2018

- 707 patients

- postoperative alpha angle associated with outcome

 

Capsular repair

 

Dasari et al Orthop J Sports Med 2023

- systematic review of capsular closure

- superior outcomes with complete capsular closure